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Nick Higham Awarded the IMA Gold Medal 2020

Professor Nick Higham has been awarded the IMA Gold Medal 2020 by the Institute of Mathematics and its Applications. Institute Gold Medals are awarded every two years in recognition of outstanding contributions to mathematics and its applications.

This is the second such success for a member of the Department of Mathematics: Professor Fritz Ursell won the IMA Gold Medal 1994.

The full prize citation is available here.

Professor Nicholas J. Higham, University of Manchester

Stefan Güttel awarded the 2021 SIAM James H. Wilkinson Prize

Dr Stefan Güttel will receive the 2021 James H. Wilkinson Prize in Numerical Analysis and Scientific Computing. This prestigious prize, established in 1979, is awarded every four years by the Society for Industrial and Applied Mathematics (SIAM). SIAM is the world’s largest professional association devoted to applied mathematics with over 14,000 individual members.

Dr Güttel’s research is in computational mathematics, and in particular, in efficient numerical algorithms for high-dimensional problems. The prize recognizes his contributions to the analysis, implementation, and application of rational and block Krylov methods. These methods have recently become very popular for the efficient solution of large eigenvalue problems, matrix equations, and in model order reduction.

Dr Güttel’s work is applicable to a wide range of problems in science and engineering. He maintains active collaborations with other Departments and companies such as Arup, Autotrader, AspenTech, N Brown Group, and Schlumberger-Doll Research. He also holds a fellowship with the Alan Turing Institute, the UK’s national institute for data science and artificial intelligence.

Dr Güttel will deliver a prize lecture at the 2021 SIAM Conference on Computational Science and Engineering (CSE21), to be held on a virtual platform in March 2021.

NLA Group Articles Amongst Most Read In SIAM Journals

Sixteen publications by members of the NLA group feature among the top 40 most read articles in two SIAM journals, both leading venues for publications in numerical linear algebra.

The following articles are amongst the 20 most read in the SIAM Journal on Matrix Analysis and Applications:

The following articles are amongst the 20 most read in the SIAM Journal on Scientific Computing:

The full lists (updated daily) are available here and here

CPFloat: A C library for emulating low-precision arithmetic

Computing machines with floating-point capabilities started appearing in the late 1940s, and despite being regarded as an optional feature for decades to come, floating-point hardware equipped a number of the mainframe computers produced in the 1960s and 1970s. At the time, there was no consensus on what features a number system ought to have, and the arithmetics implemented by any two vendors could differ widely in terms of word sizes, floating-point representations, rounding behaviour, and accuracy of the operations implemented in hardware. This lack of standardization was a major hindrance to the portability of the source code, as it made it significantly harder to write and maintain architecture-independent code.

The way out of this predicament was the establishment of the IEEE 754-1985 standard, which dictated word sizes, representations, and accuracy requirements for two default floating-point formats: single and double precision. For about three decades, hardware vendors conformed with the standard, and the large majority of general-purpose processing units came equipped with IEEE-compliant arithmetic units. Motivated by the low-precision requirements of machine learning applications, however, in recent years hardware manufacturers have started exploring the realm of low-precision arithmetics, commercialising a variety of highly optimised hardware units that pursue efficiency at the expense of accuracy. The high-performance computing community has attempted to channel the extreme performance of this hardware and utilise it in more traditional scientific computing applications, where more stringent accuracy needs typically require the use of higher precision.

The broad range of different formats available poses a serious challenge to those trying to develop mixed-precision algorithms, since studying the numerical behaviour of an algorithm in different working precisions may require access to a number of high-end hardware platforms, including supercomputer-grade CPUs and GPUs. In order to alleviate the problem, several software packages for simulating low-precision floating-point arithmetics in software have been developed. Some of these are described in the table below. All these solutions execute each arithmetic operation in hardware, and use the software layer only to round the results to the desired number of significant bits of precision.

If the hardware and the software-simulated floating-point format are both IEEE compliant, rounding requires only standard mathematical library functions, but a straightforward implementation of the rounding formulae may potentially cause two kinds of issues. From a theoretical point of view, handling subnormals, underflow, and overflow demands special attention, and numerical errors can cause mathematically correct formulae to behave incorrectly when evaluated in finite arithmetic. In terms of performance, on the other hand, the algorithms obtained in this way are not necessarily efficient, as they build upon library functions that, being designed to handle a broad range of cases, might not be optimised for the specific needs of floating-point rounding functions.

In MATLAB, low-precision arithmetics can be simulated using the chop function, developed by Higham and Pranesh and discussed in a previous post. Mantas Mikaitis and I decided to port the functionalities of this MATLAB implementation to a lower level language, in order to obtain better performance. The scope of the project has progressively broadened, and we have recently released the first version of CPFloat, an open-source C library that offers a wide range of routines for rounding arrays of binary32 or binary64 numbers to lower precision. Our code exploits the bit-level representation of the underlying floating-point formats, and performs only low-level bit manipulation and integer arithmetic without relying on costly library calls.

The project is hosted in a GitHub repository where, along with the C code, we provide a MEX interface for MATLAB and Octave which is fully compatible with the chop function. The algorithms that underlie our implementation, as well as the design choices and the testing infrastructure of CPFloat are discussed in detail in a recent EPrint. In the numerical experiments shown there, CPFloat brings a considerable speedup (typically one order of magnitude or more) over existing alternatives in C, C++, and MATLAB. To the best of our knowledge, our library is currently the most efficient and complete software for experimenting with custom low-precision floating-point arithmetic available in any language.

Simulating Stochastically Rounded Floating-Point Arithmetic Efficiently

Most general-purpose computing devices implement floating-point arithmetic defined in the IEEE 754-1985 standard (revised in 2008 and 2019) [1]. The standard provides various compulsory and recommended operations in order to prepare the hardware for as wide a space of applications as possible, as well as to assure reproducibility of numerical calculations across different devices. Hardware that is IEEE 754-compliant usually includes at least addition/subtraction, multiplication, division and square root operations. Each of these can be performed with various rounding modes, chosen by the user from round-to-nearest ties-to-even, round-toward-zero, round-toward-infinity, and round-toward-minus-infinity. Round-to-nearest provides the lowest error bound possible and thus is the default choice for most, but the other rounding modes find uses in various applications as well.

Given hardware with the five arithmetic operations and four rounding modes described above, how can we simulate other rounding modes efficiently when needed? Rounding modes that are not included in the IEEE 754 standard but are of interest in various research domains are, for example: round-to-odd [2], round-to-nearest ties-to-zero [3], stochastic rounding with 50/50 chance of rounding to either of the neighbouring values [4], or stochastic rounding with probabilities proportional to the distances between the exact value and the neighbouring floating-point values [5, 6]. The last of these is also used in fixed-point arithmetic: for example in machine learning [7] and ordinary differential equation (ODE) solvers [8].

In a recent preprint with Massimiliano Fasi [9] we address the problem of simulating the proportional variant of stochastic rounding of operations in precision $k$, when there is no higher precision available in hardware (therefore $k$ is the working precision as well as the target precision for rounding). This rounding mode requires the round-off bits captured to be used in calculating the probabilities, but they are lost in IEEE 754-compliant operations of present hardware devices—an operation is performed and only the rounded result is returned in a register. A straightforward approach would be to perform operations in higher precision than $k$ and derive the probabilities from the high precision answer. However, this approach can result in low efficiency code because we would need to use software implementation of higher precision arithmetic operations; for example the MPFR package or other similar software packages developed for the purpose of computing in higher precisions than the working precision.

Our solution is to use error-free floating-point transformations [10] for addition/subtraction and multiplication, and similar transformations (yet not error free) for the division and square root, to compute the distances between the exact number and the two closest floating-point values. This can be done by having the original arguments and the rounded answer from the hardware operation, and knowing what rounding mode was used for producing it. Our algorithms presented in the paper cover two possible cases: when the rounding mode of the hardware operations is round-to-nearest ties-to-even (default) or a combination of the other three rounding modes. The former strategy results in slightly more complicated algorithms since round-to-nearest can round to both sides of the exact number, but the latter is slower due to costs associated with changing the rounding modes—this is true at least with Intel processors which we used for testing.

In simulating stochastically rounded binary64 (double precision) arithmetic operations on a computer equipped with IEEE 754-compliant operations in that precision, our algorithms achieved between 7.3 and 19 times higher throughput of arithmetic operations compared with the simulation that uses MPFR (Table 1), while not making any compromises in accuracy. In the preprint we also evaluate our algorithms in various applications where stochastic rounding is expected to bring advantages: summation of floating-point numbers and ODE solvers. In summary, our algorithms can provide significant speedup for programs that use stochastic rounding operations in working precision.

It is worth noting that the algorithms explored in [9] should not be used if higher precision than the target precision (the precision of which stochastic rounding we would like to simulate) is available in hardware. In such cases, the higher precision should be used if possible, and the high precision results from arithmetic operations should be rounded stochastically to the target precision using different algorithms: such as the ones used in the MATLAB chop [11] and CPFloat [12] packages (a separate blog post on CPFloat can be found here).

References

[1] 754-2019 – IEEE Standard for Floating-Point Arithmetic. July 2019.
[2] Emulation of a FMA and Correctly Rounded Sums: Proved Algorithms Using Rounding to Odd. S. Boldo and G. Melquind. IEEE Trans. Comp., February 2008.
[3] Emulating Round-to-Nearest-Ties-to-Zero “augmented” Floating-Point Operations Using Round-to-Nearest-Ties-to-Even Arithmetic. S. Boldo, C. Q. Lauter, and J.-M. Muller. IEEE Trans. Comp., June 2020.
[4] CADNA: A library for estimating round-off error propagation. F. Jézéquel and J.-M. Chesneaux. Comp. Phys. Comm., 2008.
[5] Stochastic Rounding and its Probabilistic Backward Error Analysis. M. Connolly, N. J. Higham, and T. Mary. April 2020 (updated August 2020). To appear in SIAM J. Sci. Comp.
[6] Effects of round-to-nearest and stochastic rounding in the numerical solution of the heat equation in low precision. M. Croci and M. B. Giles. October 2020.
[7] Deep Learning with Limited Numerical Precision. S. Gupta, A. Agrawal, K. Gopalakrishnan, and P. Narayanan. Int. Conf. Machin. Learn., 2015.
[8] Stochastic rounding and reduced-precision fixed-point arithmetic for solving neural ordinary differential equations. M. Hopkins, M. Mikaitis, D. R. Lester, and S. B. Furber. Phil. Tran. A. Roy. Soc., January, 2020.
[9] Algorithms for stochastically rounded elementary arithmetic operations in IEEE 754 floating-point arithmetic. M. Fasi and M. Mikaitis. April 2020 (updated October 2020).
[10] Handbook of Floating-Point Arithmetic. J.-M. Muller, N. Brunie, F. de Dinechin, M. Joldes, V. Lefèvre, G. Melquiond, N. Revol, and S. Torres. 2nd ed. Birkhäuser Basel, 2018.
[11] Simulating Low Precision Floating-Point Arithmetic. N. J. Higham and S. Pranesh. SIAM J. Sci. Comp., October 2019.
[12] CPFloat: A C library for emulating low-precision arithmetic. M. Fasi and M. Mikaitis. October 2020.

Related articles

What Is Stochastic Rounding? by Nicholas J. Higham
What Is IEEE Standard Arithmetic? by Nicholas J. Higham
What Is Floating-Point Arithmetic? by Nicholas J. Higham
What Is Rounding? by Nicholas J. Higham

Parallel sparse Linear solvers: Double versus Single precision

It is well established that mixed precision algorithms that factorize a matrix at a precision lower than the working precision can reduce the execution time and the energy consumption of parallel solvers for dense linear systems. Much less is known about the efficiency of mixed precision parallel algorithms for sparse linear systems. Existing work on the performance of mixed precision algorithms for solving sparse linear systems has shown that a speedup up to 2x can be expected, but these studies are limited to single core experiments. In this EPrint, Nick Higham, Françoise Tisseur, Craig Lucas and I evaluate the benefits of using single precision arithmetic in solving a double precision sparse linear systems on multi-core processors and GPUs, focusing on the key components of LU factorization and matrix–vector products.

We find that single precision sparse LU factorization is prone to a severe loss of performance due to the intrusion of subnormal numbers. This phenomenon of LU factorization generating subnormal numbers does not appear to have been observed before. In fact, the elements at the $(k +1)st$ stage of Gaussian elimination are generated from the formula $a_{ij}^{(k+1)} = a_{ij}^{(k)} - m_{ik} a_{kj}^{(k)}, \quad m_{ik} = a_{ik}^{(k)}/a_{kk}^{(k)}$, where $m_{ik}$ is a multiplier. If $A$ is a dense matrix of normalized floating-point numbers with norm of order 1, it is extremely unlikely that any of the $a_{ij}^{(k)}$ will become subnormal. However, for sparse matrices we can identify a mechanism whereby fill-in cascades down a column and small multipliers combine multiplicatively. This mechanism is described, with an illustration for better understanding, in the EPrint, as well as strategies to automatically flush subnormals to zero, to avoid the performance penalties.

The figure below shows the speedup of single precision sparse LU factorization over double precision using the sparse direct solver MUMPS on 10 Intel Skylake cores. We used 36 sparse matrices from the SuiteSparse Matrix Collection, from which 21 matrices are of medium size with 700, 000 to 5, 000, 000 nonzero elements, and 15 larger matrices with 7,000,000 to 64,000,000 nonzeros. The orange bars represent the speeds achieved when subnormals are not flush to zero (FTZ) during the single precision LU factorization. For approximately 30% of the matrices, the orange bars are below the threshold of 1. This means instead of accelerating the computation, single precision slows it down compared with the double sparse LU decomposition. This has been corrected by flushing subnormals to zero as illustrated by the blue bars.

As for the overall performance, our experiments show that the anticipated speedup of 2x over a double precision LU factorization is obtained only for the very largest of our test problems. In the figure above, the matrices that exceed the speedup of 1.5x are exclusively of very large size. This result is not atypical, as two other sparse direct solvers considered in our work, PARDISO and SuperLU show a similar result. This contrasts with dense linear systems, where a 2x speedup is often achieved even for matrices of size as small as $200 \times 200$ when single precision is used in place of double precision.

The speedups observed in our parallel experiments are clearly lower than the speedups reported in the existing works based on single core experiments. To understand this contrast, it is important to recall that sparse matrix factorization algorithms have a pre-processing step called reordering and analysis, before the actual numerical factorization. In most of the sparse direct solvers, the reordering and analysis step is serial or has a limited parallelism. Therefore, while the time spent in numerical factorization step decreases with increasing number of cores, the reordering and analysis time stagnates and can becomes a performance bottleneck. In addition, as the reordering and analysis step does not involve floating point computation, lowering the precision, from double to single, has a little impact on the speedup except in the case of very large matrices where the numerical factorization step remains dominant despite the use of multiple cores.

For iterative solvers, our results show that the performance gain in computing or applying incomplete factorization preconditioners in single precision is not appealing enough to justify the accuracy sacrifice, but we have observed a speedup of 1.5x from matrix–vector product kernels by using single precision. In future work, we will explore new approaches to integrate efficiently single precision matrix–vector product kernels and single precision preconditioners in double precision iterative solvers without accuracy loss.

Mixed Precision LU Factorization on GPU Tensor Cores

Modern GPUs are equipped with mixed precision units called tensor cores that offer the capability of computing matrix–matrix products both at very high performance and with high accuracy. GPU tensor cores have been used to accelerate various numerical linear algebra algorithms. Among these, LU factorization is a natural candidate, since it can be written so as to heavily rely on matrix–matrix operations.

Haidar et al. were the first to propose an algorithm to compute the LU factorization of a general dense matrix exploiting GPU tensor cores, and obtained up to a 4x-5x speedup in the solution of various linear systems. Moreover, they also showed that the accuracy boost delivered by tensor cores could significantly improve the convergence of iterative methods preconditioned by the computed LU factors.

In a recent paper, Pierre Blanchard, Nick Higham, Florent Lopez, Srikara Pranesh, and I performed the rounding error analysis of an LU factorization algorithm exploiting what we called block FMAs—a generalization of tensor cores that also includes similar mixed precision units such as Google’s TPUs. We explained how block FMAs can be chained together to accumulate the result of intermediate computations in the higher precision (single precision for tensor cores), which allows for a significant accuracy boost.

However, these algorithms shared a common limitation: the matrix was stored in single, rather than half, precision. Indeed, if the matrix is stored in half precision, the accuracy boost is lost and the computed LU factors are essentially identical to those obtained by a standard LU factorization run entirely in half precision. This represents a lost opportunity, because storing the matrix in half precision not only halves the memory footprint, but also greatly reduces data movement, which brings a significant performance boost.

In a recent preprint, Florent Lopez and I propose a new LU factorization algorithm that is able to store the matrix in half precision without incurring such a significant accuracy loss. There are two main ingredients to this new algorithm. First, we switch from the standard right-looking scheme to a left-looking one, which, together with single precision buffers of controlled size, allows us to perform the update operations accurately. Second, we doubly partition the matrix so as to accurately perform the panel factorizations by exploiting tensor cores.

In our experiments, we factorize a range of test matrices using an NVIDIA V100 GPU. The two figures below summarize our main results by comparing three LU factorization algorithms: the standard algorithm (of Haidar et al. and Blanchard et al.) with the matrix stored in either single or half precision, and the new algorithm.

The figure on the left reports the backward error obtained by solving a linear system $Ax=b$ for a dense $n\times n$ matrix with random entries. The figure on the right displays the performance in GigaFLOPS. Unlike the standard algorithm, the new one does not incur a significant loss of accuracy by storing the matrix in half precision. In doing so, it greatly reduces data movement which leads to significant speedup: the new algorithm can be up to twice faster than the standard one.

A MULTIPRECISION DERIVATIVE-FREE SCHUR-PARLETT ALGORITHM FOR COMPUTING MATRIX FUNCTIONS

The need to compute matrix functions arises in many applications in science and engineering. Specialized methods exist for evaluating particular matrix functions, for example, the well-known scaling and squaring algorithm for the matrix exponential, Newton’s method for matrix sign function, and the inverse scaling and squaring method for the matrix logarithm. For some functions a specialized method is not available, in which case a general purpose algorithm is needed. The Schur-Parlett algorithm computes a general function $f$ of a matrix, with the function dependence restricted to the evaluation of $f$ on the diagonal blocks of the reordered and blocked Schur form. It evaluates $f$ on the nontrivial diagonal blocks via a Taylor series, so it requires the derivatives of $f$ and it also requires the Taylor series to have a sufficiently large radius of convergence. However, the derivatives are not always available or accurately computable.

In our recent preprint, Nick Higham and I present a version of the Schur-Parlett algorithm that requires only function values and uses higher precision arithmetic to evaluate $f$ on the diagonal blocks of order greater than 2 (if there are any) of the reordered and blocked Schur form. Our algorithm is inspired by Davies’s randomized approximate diagonalization method, but we show that the measure of error that underlies randomized approximate diagonalization makes it not a reliable numerical method for computing matrix functions. The key idea in our algorithm is to compute by diagonalization the function of a small random diagonal perturbation of each triangular block, where the perturbation ensures that diagonalization will succeed. Multiprecision algorithms have already been developed for the matrix exponential and the matrix logarithm, and those algorithms are tightly coupled to the functions in question, whereas here we place no restrictions on the function. And the algorithm we propose is not restricted only to a working precision of double since its framework is precision independent. We test our algorithm in double precision on a variety of test problems, and the results show that the algorithm generally behaves in a numerically stable fashion. We apply our algorithm to the matrix Mittag-Leffler function and show that it yields results of accuracy similar to, and in some cases much greater than, the state of the art algorithm for this function.

In the following example we employ the algorithm to compute in double precision the matrix Airy function, and compare the result with that produced by a spectral decomposition method (which breaks down if A is defective, and will be inaccurate if A is close to being defective).

We observe that the normwise relative difference between our algorithm and the spectral decomposition method is tiny. This is just one of the many matrix functions that no specialized algorithm is available for, and the MATLAB $\texttt{funm}$ function, which implements the Schur-Parlett algorithm, is not able to compute. Our new algorithm greatly expands the class of readily computable matrix functions, and its MATLAB code is available here.

Pivoted Matrices with Tunable Condition Number and the HPL-AI Benchmark

Traditionally, the fastest supercomputers in the world are ranked according to their performance on HPL, a portable implementation of the High-Performance Computing Linpack Benchmark for distributed memory systems. This software package measures the rate of execution, expressed in binary64 floating-point operations per second, at which a computer solves a large dense linear system using LU factorization with row partial pivoting. This metric is an excellent predictor of the performance a machine will achieve on compute-bound tasks executed in binary64 arithmetic, but the test problem is not representative of typical artificial intelligence computations, where lower precision is typically considered satisfactory.

In an endeavour to consider both workloads at once, the Innovative Computing Laboratory (ICL) at the University of Tennesse, Knoxville, developed the HPL-AI Mixed-Precision Benchmark. The reference implementation of the benchmark solves a dense linear system $Ax = b$ of order $n$ to binary64 accuracy by complementing a low-precision direct solver with a high-precision refinement strategy. The code generates $A$ and $b$ in binary64, computes the LU factorization without pivoting of $A$ using only binary32 arithmetic, finds an approximate binary32 solution $\widetilde x$ using forward and back substitution, and finally solves the linear system with GMRES in binary64 arithmetic, using $\widetilde x$ as starting vector and the low-precision LU factors of $A$ as preconditioners.

In order to obtain the best possible rate of execution, the coefficient matrix $A$ must be dense and, as the benchmark is expected to be needed for $n > 10^7$, it should also be easy to generate at scale on a distributed memory environment. Furthermore, we require that $A$ have growth factor of order 1, so as to guarantee the stability of Gaussian elimination without pivoting, and be not too ill-conditioned, in order to ensure the convergence of GMRES. Currently, the reference implementation relies on a randomly generated matrix that is diagonally dominant by rows. This choice ensures the stability of LU factorization without pivoting, but the matrix thus constructed requires an amount of communication that depends on $n$, and turns out to be extremely well conditioned, with an $\infty$-norm condition number just above 4 for large $n$.

In our EPrint Matrices with Tunable Infinity-Norm Condition Number and No Need for Pivoting in LU Factorization, Nick Higham and I present a new parametric class of dense square matrices $A(\alpha,\beta)$ for which LU factorization without pivoting is stable. The parameters $\alpha$ and $\beta$ that yield a specified $\infty$-norm condition number can be computed efficiently, and once they have been chosen the matrix $A(\alpha,\beta)$ can be formed from an explicit formula in $O(n^2)$ floating-point operations.

We also discuss several adaptations aimed at further improving the suitability of the generated matrix as a test problem for the HPL-AI benchmark, as our main goal is to provide a robust and efficient matrix generator for it. In particular, we explain how scaling the matrix can help transition from binary32 to binary16, in order to take advantage of the hardware accelerators for low precision such as the tensor cores that equip recent NVIDIA GPUs, and we discuss how the matrices can be tweaked to make the entries in the LU factors less predictable and slow down the convergence of GMRES.

Numerical Behaviour of Tensor Cores

For many years, the arithmetic operations available on most hardware were $+, -, *, /, \sqrt{}$. More recently ($\sim 20$ years ago) the FMA (fused multiply-add) operation also became prevalent in general purpose devices such as CPUs and GPUs. Software builds on top of these operations, for example compilers use a series of these and other hardware instructions to implement more complex functions and algorithms such as the exponential function, matrix multiply, or the algorithms for pseudo random number generation. These arithmetic operations have been standardized by the IEEE 754 floating-point standard since 1985 and most current systems are compliant with it.

Recently, because of the increasing adoption of machine learning, general purpose devices started to include inner product or matrix multiply-accumulate (MMA) operations in hardware. This is a generalization of a scalar FMA to vectors and matrices. Since it is performed in hardware, the expected speedup is achieved due to parallelism — instead of using a few FMA hardware units sequentially to multiply matrices as is the case in software, all of the elements of a matrix of some size are computed in parallel. Using the inner product and matrix multiply-accumulate operations in hardware, compute-bound applications that have high-intensity usage of them are sped up significantly.

NVIDIA GPUs are widely used for machine learning and other applications. In the latest TOP500 supercomputer list published in June 2020 [1], 112 computers are equipped with NVIDIA graphics cards. The main feature of the recent NVIDIA GPUs is hundreds of arithmetic units for performing the MMA operation — NVIDIA calls these tensor cores. Various applications outside machine learning are being explored in order to utilize very high arithmetic throughput that can be achieved when using MMAs in hardware [2]. Table 1 lists three recent NVIDIA architectures as well as other hardware devices with an MMA operation on chip. The NVIDIA V100 has the first version and the T4 has the second version of tensor cores; in these devices tensor cores work on matrices of size $4 \times 4$ in mixed-precision of fp16 and fp32, as shown in Figure 1. The most recent revision of tensor cores in the A100 updated both the precisions available and the dimensions of input/output matrices. See the NVIDIA V100 and NVIDIA A100 whitepapers for more details.

The MMA operation is not standardized by the IEEE 754, therefore various numerical features of tensor cores are not clear. Knowing such features as the support for subnormal numbers, order of operations, and rounding modes and normalization of significands in various parts of the MMA computation can be important, for example when doing error analysis of algorithms that utilize MMAs in order to derive error bounds [3]. As the application space utilizing tensor cores is growing beyond machine learning, understanding of the numerical behaviour of tensor cores will become increasingly useful. Even before such hardware is put to use in some applications, one might want to simulate the behaviour of tensor cores in order to develop numerical codes targeted to tensor cores, on a conventional hardware. Furthermore, there is also a question of differences in numerical behaviour between tensor cores and software MMA using the standard FMA hardware calls, for example differences that would appear when transitioning the existent software to use tensor cores.

Motivated by this, in our recent preprint [4] we investigate an experimental testing methodology of the tensor cores. The method consists of the following steps.

1. Identify a numerical feature that needs to be tested, for example, the rounding mode in the 5-operand adders that accumulate products in MMA.
2. Identify possible implementations, for example round to nearest or round toward zero.
3. Find floating-point inputs that would result in different outputs for each possible hardware behaviour in 2.
4. Observe outputs and make a conclusion based on expected outputs for each possible behaviour in 2.

Using this approach, we identified the following list of numerical features of the NVIDIA tensor cores.

• Subnormal floating-point numbers are fully supported, both on the inputs and outputs.
• 5-operand adders accumulate 5 addends (4 products from $AB$ and a value from $C$) starting from the largest in magnitude.
• Round toward zero, rather than round to nearest (default in IEEE 754-compliant arithmetic), in the 5-operand adders is implemented.
• Different normalization behaviour from the MMA implemented in software (tensor cores normalize the answer of the whole 5-element dot product at the end rather than after each addition of products).
• Inner products without intermediate normalization are shown to be non-monotonic in rare cases (this result is more general than tensor cores, since to the best of our knowledge, most hardware implementations do not normalize on every addition due to lower hardware costs).

Our conclusion is that in the current version, the tensor cores on V100 and T4 (the A100 is not yet available to us) do not replicate the behaviour of the MMA implemented with IEEE 754 compliant FMA hardware operations. These numerical behaviours are expected in a hardware MMA optimized for reducing hardware cost and most likely is motivated by a fact that machine learning applications usually are claimed to not need all the IEEE 754 features and high precision in general. These results provide the parameters that can be used in rounding error analysis of tensor cores [3] which can be useful when developing numerical software.

Our CUDA code to test numerical features of tensor cores is available here.

References

[2] A. Abdelfattah et al. A Survey of Numerical Methods Utilizing Mixed Precision Arithmetic. July 2020. Published online.

[3] P. Blanchard, N. J. Higham , F. Lopez, T. Mary, and S. Pranesh. Mixed Precision Block Fused Multiply-Add: Error Analysis and Application to GPU Tensor Cores. SIAM J. Sci. Comput. May 2020.

[4] M. Fasi, N. J. Higham, M. Mikaitis, and S. Pranesh. Numerical Behavior of NVIDIA Tensor Cores. July 2020; revised October 2020. MIMS Eprint, published online.


text:
How to configure Raspberry Pi in Ad hoc wifi mode

· 4 mins read

Hi friends! Today’s tutorial is Part 02 of the Raspberry Pi (RPi) learning series. In this, you will learn how to configure your RPi device in Ad hoc mode or infrastructure-less mode. Yes, that means without any requirement of a wifi router. That is a significant advantage of Ad hoc mode because it gives us the wifi-router freedom, and a dedicated point-to-point link provides lower latency, which is the best choice for the FPV systems.

By default, the RPi devices connect to the wifi router upon providing the SSID to them. However, in Ad hoc mode, we have to assign our SSID and the IP address to the device. So, instead of searching and connecting to other wireless networks, the RPi will create its network, which is, of course, ad hoc in nature. We can name this network RPitest.

The first thing to do is to SSH to the RPi, just like we did in the previous tutorial. Then use the following to cd to the network directory:

cd /etc/network

Now, to keep the original interface file for the wifi interface, let’s make a backup as:

sudo cp interfaces wifi-interface

Next is to create a new file for our Ad hoc interface so do the following to make file and edit:

sudo nano adhoc-interface

Now copy the following and paste in the above file:

  auto lo
iface lo inet loopback
iface eth0 inet dhcp

auto wlan0
iface wlan0 inet static
wireless-channel 4
wireless-essid RPitest

After that, we need to save the file, so press Ctrl+X and then Yes and enter to save it. This configuration of adhoc-interface will let the IP address of our RPi to be 192.168.1.1, and the netmask will be 255.255.255.0. You can select more channels as well e.g. 11, but 4 is enough to keep it a lightweight network. The network SSID is RPitest, and of course, the mode is ad-hoc. You can also add the password using wireless-key yourpassword, and other parameters to this configuration, but you got the idea.

The next step is to let our RPi assign an IP to the device trying to connect to it in Ad hoc mode. Now, please make sure that your RPi is already connected to the wifi to install something in it. For this, we need to run the following command:

sudo apt-get install isc-dhcp-server

After that, we need to edit this dhcpd.conf file using:

sudo nano /etc/dhcp/dhcpd.conf

Scroll down in this file, and after the end line, copy and paste the following in it:

  ddns-update-style interim;
default-lease-time 600;
max-lease-time 7200;
authoritative;
log-facility local7;
subnet 192.168.1.0 netmask 255.255.255.0 {
range 192.168.1.5 192.168.1.150;

}

Again save the file by pressing Ctrl+X and Yes Enter. In the above lines, any new device connected to RPi will be assigned 192.168.1.5 IP address and so on. That’s all for the configuration editing part.

The next step is to tell our cute little RPi zero, that after rebooting, which interface should it follow? i.e., wifi-interface or adhoc-interface.

To answer this question, we can always go to the network directory as:

cd /etc/network

Then, if we want to switch to adhoc-interface use:

sudo cp /etc/network/adhoc-interface interfaces

Similarly, if we want to switch to wifi-interface use:

sudo cp /etc/network/wifi-interface interfaces

That’s it if you have switched to adhoc-interface, then after reboot, you can find an RPitest network on your mobile or computer device. Once connected to this network, you can enjoy FPV mode. Also, note that in the adhoc mode your RPi will be on 192.168.1.1 adress.

Finally, every time you want to update some parameters to the adhoc interface, you must switch to wifi interface and then again switch to adhoc interface to get the results back.

That’s it for this tutorial, enjoy :)

format: plain


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# proper mapping theorem

###### Theorem.

Let $X$ and $Y$ be complex manifolds, $f\colon X\to Y$ be a proper (http://planetmath.org/ProperMap) holomorphic map, and $V\subset X$ be a complex analytic subvariety of $X.$ Then $f(V)$ is a subvariety of $Y.$

## References

• 1 Hassler Whitney. . Addison-Wesley, Philippines, 1972.
Title proper mapping theorem ProperMappingTheorem 2013-03-22 17:41:01 2013-03-22 17:41:01 jirka (4157) jirka (4157) 4 jirka (4157) Theorem msc 32A60 msc 32A25


text:
# Determine whethere the following series is convergent or divergent

## Homework Statement

Determine whether the following series is convergent or divergent:
$$\frac{1}{2^2}+\frac{2^2}{3^3}+\frac{3^3}{4^4}+....$$
I rewrite it as:
$$\sum_{n=1}^{\infty} \frac{n^n}{(n+1)^{n+1}}$$

## The Attempt at a Solution

I stopped.
I can not do anything.

## The Attempt at a Solution

Related Calculus and Beyond Homework Help News on Phys.org
jgens
Gold Member
You do need to show us your attempt at the solution before we can help, so which convergence tests have you tried?

You do need to show us your attempt at the solution before we can help, so which convergence tests have you tried?
Its not geometric
not telescoping
nth term test failed
can not use integral test
Ratio & Root failed because its algebric function

There is only the comparison tests
I tried them a lot
but every time i failed :/

Dick
Homework Helper
Write it as (n^n/(n+1)^n)*(1/(n+1)). The first factor approaches a finite limit. What is it?

Write it as (n^n/(n+1)^n)*(1/(n+1)). The first factor approaches a finite limit. What is it?
The first one goes to 1/e
the second goes to 0
1/e times 0 = 0

nth term test failed.

jgens
Gold Member
Alright, I would suggest using the comparison test for this particular series (although I'm sure that there's probably a simpler way to do it). If $n \geq 1$ can you find an upper bound for the following:

$$\frac{(n + 1)^{n+1}}{n^{n+1}}$$

Edit: Fixed typo

Edit 2: Fixed another typo. Sorry, I just seem to be mistake prone today.

Last edited:
Dick
Homework Helper
The first one goes to 1/e
the second goes to 0
1/e times 0 = 0

nth term test failed.
What 'nth term test' are you talking about? You are right the first factor approaches 1/e. So for large values of n a term in the series is approximately 1/(e*(n+1)). What kind of test does that suggest?

What 'nth term test' are you talking about? You are right the first factor approaches 1/e. So for large values of n a term in the series is approximately 1/(e*(n+1)). What kind of test does that suggest?
nth terms test = Test for divergence.

hmmm .. I got it .. Limit comparison test with the divergent series $$\sum_{n=1}^{\infty} \frac{1}{n+1}$$
The limit of the limit comparison test will give 1/e which is positive and finite number
hence, our series diverges.

Right?

Last edited:
Dick
Homework Helper
nth terms test = Test for divergence.

hmmm .. I got it .. Limit comparison test with the divergent series [tex]\frac{1}{n+1}[\tex]
The limit of the limit comparison test will give 1/e which is positive and finite number
hence, our series diverges.

Right?
Right.


text:
Powershell create scheduled task run as system

In order to do that, go to the Actions tab. Say we have a PowerShell script that we want to run on a regular basis. This article will guide you to create Scheduled task using PowerShell. Type the following commands to create a variable to store the action of the task and press Enter. 168. 5. The version I am using here ships with Windows Server 2008 R2, but the concepts should be the same on earlier releases. 0 a scheduled task can be easily created with the new cmdlets New-ScheduledTaskAction, New-ScheduledTaskTrigger and Register-ScheduledTask, but unfortunately i have to create a solution that works on clients running PowerSshell version 3. After the scheduled task is registered and showing up in Task Scheduler, you can now run the Get-ScheduledTask cmdlet to see the task. ps1 as a scheduled task. And withthat, you can easily filter on (Get-ScheduledTask -TaskPath) only If I manually execute the scheduled task via PowerShell Start-ScheduleTask, again, nothing seems to happen. This ensures that our Powershell script will run when the computer starts. exe -i -s powershell. How do I run a PowerShell script as a system user? Powershell Tip #53: Run PowerShell as SYSTEM (NT AUTHORITY\SYSTEM) Open cmd. Of interest to me right now are the Get-ScheduledTask cmdlet, that will allow me to analyse the existing tasks, and New-ScheduledTaskTrigger, as it’s the one I’ll have to understand. Type the following comm a nds to create a v a ri a ble to store the a ction of the t a sk a nd press Enter. the Create Basic Posted: (1 week ago) To create PowerShell scheduled t a sks on Windows 10, use these steps: Open St a rt. The command we'll need is New schedule Exchange Server Scripts using PowerShell is pretty straightforward, and basically just create your ps script and run through the Wizard, do a basic task and schedule that to run on a weekly basis or daily basis or whatever works for you. Below is a full example: Change the properties of scheduled task schtasks /Change /? Run scheduled task on demand schtasks /Run /TN MyTaskName Stop currently running scheduled task schtasks /End Adding a task to to the OS task scheduler. This bat file will be used in the scheduled task later. Use the New-JobTrigger cmdlet to create a startup trigger. I setup my task to run at 12:00am and to "recur every" 1 days, now I'm in advanced properties. Powershell - Create Scheduled Task to run as local system / service Solution: For those who can use PowerShell 3. You can leave the “configure for” as the default (Vista/Server08) Trigger: Set it to run “On A Schedule” => Daily start at 12:05 AM To create PowerShell scheduled tasks on Windows 10, use these steps: Open Start. To create your encrypted password file, open Powershell and run the following command: The Register-ScheduledTask cmdlet registers a scheduled task definition on a local computer. Start the “Basic Task” wizard. 0 you can simply use any module cmdlet without having to import the module. exe as administrator. Create a Scheduled Task to run as local system Post by devlife3 » January 4th, 2010, 8:23 am Can anyone tell me how to create a scheduled task that will run as the local system or service? Create a script to create the task and copy the PowerShell file. 0 If I manually execute the scheduled task via PowerShell Start-ScheduleTask, again, nothing seems to happen. schtasks is in System32 if it's not already in your path. Alright, so you’ve built up your skills for Powershell, developed your script, got all the kinks worked out and now it’s time to set the script to do your work on daily bases by putting it to Windows Task Scheduler. By default, all the scheduled tasks are created under the root “\” folder, if you have many tasks here, from the taskschd. 25 Okt 2018 The command below schedules creates a task to run a PowerShell script at the top of the hour (:00), every hour, as SYSTEM. So I suggest to create your tasks to some custom task folders. Tick the radio button ‘Run whether the user is logged in or not’. Verify the script ran and the task was deleted . 0 and the ScheduledTasks module which we'll find in Windows 8 and Windows Server 2012. 0,5. jpg -Recurse | Copy-Item -Destination "\\192. Creating a single task to run a Powershell script via the Windows Task Scheduler GUI can be a set-it-and-forget-it configuration. the task doesn't run: Open the Task Scheduler in Windows or Windows Server. My question is I want to create a scheduled job running as user administrator through code. However, you cannot schedule tasks to run only one time. Ok, so lets get started! the ingredients we will need today are: Windows 8. Setup a scheduled task to run a PowerShell script: First, open the Task Scheduler. However, if  20 Şub 2020 Create Scheduled Task uses PowerShell to create an entry in the Task Scheduler that launches a cmd file. Select a user, preferably one that has permissions to save the Excel file to the path you entered in the script. 4 May 2020 In the first part of my blog posting, I showed how to use the Windows Task Scheduler to run PowerShell scripts at specific times. C:\Windows\System32\WindowsPowerShell\v1. de 2020 $principal = New-ScheduledTaskPrincipal -UserID "NT AUTHORITY\SYSTEM" -LogonType ServiceAccount -RunLevel Highest. @machineslave. Apparently the task scheduler API supports hiding the console window, but the command line and visual interface don't expose it. In fact, without better software, checking manually can take quite a while even on a single PC. At a minimum, you should fill out the following To start, open task scheduler by clicking start menu and typing task scheduler and click create basic task… or create task… from the actions pane. On the system that the task will be run from, open the Windows Task Scheduler. Open the task scheduler (Start -> All Programs -> Accessories -> System Tools -> Task Scheduler. In this post When we run the example script block, the schedule task will be created in the PowerShell\ScheduledJobs folder within the Task Scheduler. the task doesn't run: Task Scheduler is probably the best way to run a PowerShell script since it includes a scheduling option for startup execution. Task Scheduler to run PowerShell. Give a name to the task and select ok. Net method of creating the task, as there’s more options using the . Task Scheduler is one of the best utilities of Windows 10, allows you to create Aug 21, 2019 · I set up the task schedule to execute my the bat file with the The task runs under the SYSTEM account; It runs with highest privilleges; 17 Mar 2021 Creating a task with an administrator or System user account may not work Tip: Open PowerShell and run the command Get-ScheduledTask | ? 8 Mar 2019 Setup a scheduled task to run a PowerShell script: · First, open the Task Scheduler.$Action = New-ScheduledTaskAction -Execute 'C:\Windows\System32\WindowsPowerShellv1. exe -File \\location\to\file. At a minimum, you should fill out the following Posted: (1 week ago) To create PowerShell scheduled t a sks on Windows 10, use these steps: Open St a rt. Setup the scheduled task: Create a basic task. 19 Jul 2019 Our N-Central monitoring system creates a ticket for this so we can PowerShell; A monitoring system, or way to run the scripts. To start, open task scheduler by clicking start menu and typing task scheduler and click create basic task… or create task… from the actions pane. Follow these easy steps to add your dailyjob. 29 de out. Things change a bit here, when we plan to run the task scheduler with Domain Account. 2 Ağu 2019 1. msc”, hit Enter key to launch it. If you add the code in this script to the NppUpdater script, it'll also create the scheduled task … Posted: (1 week ago) To create PowerShell scheduled t a sks on Windows 10, use these steps: Open St a rt. This is because as only the creator can decrypt the . I have my little Latte Panda machine that run Windows server and I want it to auto turn of at 2am everyday. a) on the computer which will be running the scheduled task b) using the account which will run the Scheduled Task. And configure your trigger. Here is the code which creates the schedule with SYSTEM User. · Give your task a name and a description and any other  6 Mei 2017 Net method rather than using the PowerShell cmdlet: New-ScheduledTask The information to help build the below… If you were creating a GUI to run in Powershell that would be annoying that the task needs to be scheduled to run under the NT AUTHORITY\SYSTEM account,  6 Agu 2015 The script below will create a Scheduled task called CWS-ArchiveLogFiles, which will run on a daily basis as 12am and run a powershell script in  Jan 26, 2021 · The scheduled task will have no user to execute as and will not Use PowerShell to Create Scheduled Tasks Sep 25, 2018 · PowerShell  22 Jun 2016 ps1 from C:\script and execute it. This forced me to store my service account password as clear text, which made me cringe. Therefore, using command-line tools and PowerShell to list scheduled tasks is a more attractive option. If I run the scheduled task using the System account, the dialogue box isnt displayed but the reg keys are all set. Therefore I create a  13 Mar 2019 In the script below I use Register-ScheduledJob to create a PowerShell job. 0\  3 Mei 2020 Create Scheduled Task to Trigger a PowerShell Script The only thing I've changed is for it to stop if the task runs longer than 1 hour. This script will generate a new Scheduled Task. Two methods can be used depending on your Windows operating system. Right click Task Scheduler Library and select Create Task (not basic task) Under the General tab, insert the Name and Description. This blog describes the automated creation of such Scheduled Tasks with PowerShell and the possibilities to use such a task as a service replacement. A quick Get-Command *sched* tells me that there is a whole module dedicated to scheduled tasks. Se a rch for PowerShell, right-click the top result, a nd select the Run a s a dministr a tor option. The PowerShell script does all it's stuff locally when it's called from the Windows Task Scheduler. Below is a full example: First use Register-ScheduledJob to create your PowerShell job. To create your encrypted password file, open Powershell and run the following command: Right click Task Scheduler Library and select Create Task (not basic task) Under the General tab, insert the Name and Description. This will make a ta Powershell, create ScheduledTask as system, run once, run CMD, delete - Script Center - Spiceworks If I run the scheduled task with the Builtin\Users user account and call the powershell script it presents the dialog box but the reg keys dont get set as the registry needs to be edited using admin creds. You can find more commands in the MSDN and hope this article is useful for creating a basic task in the task scheduler using the PowerShell script. For Program/script enter: C:\Windows\System32\WindowsPowerShell\v1. msc” in the window that opens. Go to “Windows PowerShell ISE” and run as administrator if needed and type the command that you want to add to the script by using the command window as below: Figure 6: Command window . key file, and this can only be done on the computer which generated the key file. A variation of the above command with more explicit options like compatibility and run level produces the same result - i. Step 1 – Open Task Scheduler and create a new task. static class PoshExec { static void Main (string [] args) { (new System Note that you need to run this script with elevated privileges – start Windows PowerShell by using the Run as Administrator option if running interactively, or specify the Scheduled Task runs as the SYSTEM account and enable the ‘Run with highest privileges’ option. I knew there had to be a better way, even if the cmdlet did not allow a credential object to be passed to it. exe utility enables you to manage scheduled tasks on a local or remote One of my tasks is to install a web based product using powershell. The following script will setup a scheduled task to run as any user by running the task as the ‘Users’ group. 4 Make necessary changes for all settings. If you like me, want to run a PowerShell script, type Use a scheduled task principal to run a task under the security context of a specified account. In my previous post, I described the PowerShell script used to rebuild the Development environment for TechnologyToolbox. exe, right-clicking on the result, selecting "run as administrator" and hitting enter. Follow the below steps to create and schedule a task using the Windows task scheduler: Step 1 – Press Windows + R (or click the start button and type run) and type taskschd. When you create a scheduled task; you need to specify what Action to perform when  12 de jun. In the Task Scheduler, select the Create Task option under the Actions heading on the right-hand side. When creating the scheduled task, ensure only the first path goes in the “Program/script:” edit box and everything after “-PSConsoleFile” goes into the “Add arguments (optional)” edit box. The first method is to create a new basic task in Computer Management / System  $STPrincipal = New-ScheduledTaskPrincipal -UserID "NT AUTHORITY\SYSTEM" -LogonType ServiceAccount -RunLevel Highest Register-ScheduledTask To create a schedule task to either run as the system-account or the Below are the requirements to create PowerShell scheduled tasks using PowerShell. At Action step, select Start a program and click Next. When you use a scheduled task principal, Task Scheduler can run the task regardless of whether that account is logged on. This is a step-by-step tutorial on how you can do this in Windows 10, but the steps in this guide applies to all modern Windows client and Windows server operating systems. Repetitive creating and updating Windows Scheduled Tasks manually using Windows built in manager can be annoying. Execute a PowerShell 7 Script Create a Scheduled Task to run as local system Post by devlife3 » January 4th, 2010, 8:23 am Can anyone tell me how to create a scheduled task that will run as the local system or service? However, manually creating these tasks can be really time-consuming. 0\powershell 20 Mei 2011 Windows Server 2003. Options parameter is optional. de 2013 With PowerShell 4. The script below will create a Scheduled task called CWS-ArchiveLogFiles, which will run on a daily basis as 12am and run a powershell script in C:\ScheduledTasks called CWS-ArchiveLogFiles. 0 in Windows 8 and Windows Server 2012. Configure the action “Start a program” The program to start is Powershell. Task Scheduler is probably the best way to run a PowerShell script since it includes a scheduling option for startup execution. This is where we configure what our scheduled task will run. Create the job trigger. 1. Select the file to be run on the action tab. The great trick about this is that the set automatically resets itself after 24 hours, unless we create another task. But when you have to configure several tasks every day with the same parameters, the process becomes monotonous. msc to launch the Windows Task Scheduler as shown below: Step 2 – Click on the Create a task to create a new task as shown below: Step 3 – In the General tab, provide Applies to: Windows PowerShell 3. In this post 1 Create the PowerShell script which we want to run on schedule and save to . First, We’ll start by trying to get all tasks on our system. Create Windows scheduled task (for the NppUpdater script) The previous NppUpdater script doesn't do anything without it being scheduled in the task scheduler. We can schedule this by opening up the Windows Task Scheduler and choosing Create Basic Task: Follow through the wizard choosing a Task Name, Trigger (for example, daily) and for the action choose Start a Program. Right-click on the task, select Properties to make all the settings available for change. bat), command files (*. This can be used a few ways, remote powershell doesn't have network access to shares, so a CMD that you may worked with PSEXEC wont work in remote PS. I've tried querying the event log with PowerShell, but can't see anything immediately useful. Pass the arguments if any that is required for the script in the set Argument tab. Step 5 – Click on the Actions tab and To start, open task scheduler by clicking start menu and typing task scheduler and click create basic task… or create task… from the actions pane. Delete the existing action, in my example ‘Custom handler’ and add your own. This code above will create a scheduled task that will fire off your PowerShell script when any user logs on to the system. So I thought I also release a script to you, which does just that. Please note, this is using the . de 2018 New-ScheduledTask cmdlet is used to create a scheduled task. 3 Click on “Create Task” from right hand side. powershell. 2. Enabling the local admin account Open task scheduler by searching in windows and select create a basic task. 0 on Windows 8 or Windows Server 2012, new cmdlets will let you do it in a simple way when registering Creating Scheduled Task with Windows PowerShell Let's create a scheduled task named (checkbox Run with highest privileges) under the SYSTEM account. This will bring up your Group Policy Object for which we will set this policy's conditions. g. Immediate Scheduled Task to run PowerShell script. Hello. This post is about how to create scheduled task programmatically. I'm trying to create a scheduled task of a powershell script to run every hour. Make sure to test the PowerShell independently if it works fine. If you want to create a scheduled task under windows server 2003 then we should use the schtasks. If I manually execute the scheduled task via PowerShell Start-ScheduleTask, again, nothing seems to happen. ps1. With this example, you can learn how to use PowerShell scripts to collect WCI data for scheduled tasks. At the next window, type PowerShell as the Program/script and the full-path of the script file as the argument. And because we included the RunNow switch parameter, the script was run and a text file was created in the Temp\Export folder as expected. Notes. Remember, with PowerShell 3. To create the job trigger, open the Windows PowerShell console with admin rights by right clicking the Windows PowerShell icon on the Start page or from the task bar, and then choosing Run as Administrator from the action menu. Edit GPO to add settings. A scheduled task action represents a command that 29 Eki 2020$principal = New-ScheduledTaskPrincipal -UserID "NT AUTHORITY\SYSTEM" -LogonType ServiceAccount -RunLevel Highest. Then I use Set-ScheduledTask to change the startup account to  10 Mar 2014 If you like me, want to run a PowerShell script, type powershell in the program field and type the path to your . 30 de ago. Create Scheduled Task with Windows PowerShell; In modern versions of PowerShell, to create them we can use the New-ScheduledTaskTrigger and Register-ScheduledTask cmdlets. Configure a Trigger – once a week should be more than enough for this particular task. There are a few things that are required when it comes to creating a schedule task. 0 a scheduled task can be easily created with to run the task when the system is idle we set the value of Create to 6. Right-click ‘Task Scheduler (local)’ in the left pane. You can do that with a tap on the Windows-key, typing Powershell. Applies to: Windows PowerShell 3. Task Scheduler is mainly used to run any  Also, scheduled tasks are executed in their own session, instead of the same session as system services or the current user. I know, I’ve been there myself. Figure 1. Type a name and description for your task. I find myself creating Windows Scheduled Tasks very often to run a PowerShell Script on a scheduled basis, and while PowerShell V3 will provide Cmdlets to manage the Scheduling Engine - V2 does not. ps1 file in the Add Arguments  6 Jul 2012 I find myself creating Windows Scheduled Tasks very often to run a PowerShell Script on a scheduled basis, and while PowerShell V3 will  11 Mar 2017 powershell scheduled tasks Create a scheduled task (at least Windows 7). Part of that install is to schedule a powershell script to archive and prune logs. “Create a Basic Task” – Give your task a friendly name (“PowerShell – Daily Running Service Report”) and description. It allows schedulex execution of programs or scripts at specific pre-defined time or recurrent time interval. This time, we look at creating a new scheduled task. Windows provides the schtasks. I have a windows PowerShell Script that I made to move a folder to anther folder on the same drive. So the strategy is to use the Windows Task Scheduler to run a PowerShell script. ps1) 2 Launch Task Scheduler from start menu or use Win + R then type “taskschd. Scheduled Task to run as any User. In advanced, I checked "repeat task every" and set it to "1hour", but do I set "for a duration of" to "indefinitely" or "1 day"? In the last lesson we started looking at using the PowerShell 3. Practical Example. Choose your trigger. the task doesn't run: Run PowerShell Script as a Scheduled Task. Next, create the job as whatever you like, then when you get to the Job Step, create it as Operating System (CmdExec) and change the Run as: to your newly created proxy account. the task doesn't run: Trying to troubleshoot these issues using Task Manager can be very difficult, since services and scheduled tasks are stored and displayed separately. The Operating System, indeed, does not supported this option for the "LOCALSERVICE" account, but in order to avoid the mandatory password, you can check it when you create the scheduled task in Advanced Installer, and it will be installed correctly on the machine (with Instead, PowerShell 3. The actions pane. Next, load Task Scheduler from Start > All Programs > Accessories > System Tools. When I run the Powershell code, it is creating my scheduled task that will run in exactly 30 minutes: As you can see, scheduled tasks are quite powerful, and having the ability to create them to run in XX amount of time can be handy. The New-ScheduledTaskAction cmdlet creates an object that contains the definition of a scheduled task action. In our case its a Posted: (1 week ago) To create PowerShell scheduled t a sks on Windows 10, use these steps: Open St a rt. Any advice greatly Note The Scheduled Task module first appeared with Windows PowerShell 3. In the last lesson we started looking at using the PowerShell 3. Select ‘Create Task’. These Scheduled Jobs can be managed within PowerShell using cmdlets. Case 2: Run the PowerShell script with Windows Task Scheduler with a Domain Account. With PowerShell 4. When the computer enters an idle state. To create a new scheduled task, click Create Task from the right-hand “Actions” panel. 20\CopiedFiles" @dafyre said in Creating Scheduled Task with Powershell - Using specific user account:. You can use the definition of a scheduled task principal to register a new scheduled task or update an existing task registration. at action step, select start a program and click next. Configure the dropdown to use the latest version. 1 or higher; PowerShell; A monitoring system, or way to run the scripts. the task doesn't run: Directly setting the PowerShell file on Task Scheduler may resolve to indefinite task that is running, above solution will help. ps1), and then schedule powershell. After you create a scheduled task with PowerShell, you can open the Task Scheduler to see the name of the task, its triggers and other details. the task doesn't run: Posted: (1 week ago) To create PowerShell scheduled t a sks on Windows 10, use these steps: Open St a rt. Step 3 – In General tab, specify the name, description and security options of the task. What we need to do first is create a PowerShell script which copies the PowerShell file to a directory so the scheduled task can start it. Posted: (1 week ago) To create PowerShell scheduled t a sks on Windows 10, use these steps: Open St a rt. echo on. Scheduled task is one of the useful feature in Windows Operating System enable to schedule to launch a program or to run some scripts at specified time, date or even when particular event occurred. And also the properties are disabled like "Run,Start in,Comment and so on". Register-ScheduledTask  Task Scheduler is a Windows tool that allows you to Create and automate any routine tasks on a chosen computer. exe -NoLogo -File "c:\tmp\scripts\AD_Health_Check\ad health check v2 parms. The bat file is simple and only has the following reference in it: 1. Here's how I solved it: First, I had to use the UNC path to specify the path of the mapped drive: Get-ChildItem -Path "C:\MyFiles\*" -Include *. Under Add Arguments enter for Exchange 2010: Hi and welcome to our forums. Create a new trigger and set “at logon” as the trigger. msc GUI, it might take time to display all of them. e. Figure 9 – Windows tasks scheduler. Directly setting the PowerShell file on Task Scheduler may resolve to indefinite task that is running, above solution will help. To close off on the subject of triggers, please note that some advanced options can be set. You can run it multiple times under an administrative account if you want to check how it works. Net method rather than using the PowerShell cmdlet: New-ScheduledTask. Something that is pretty cool, this process survives sysprep --- meaning, you could have a scheduled task run upon first login, perform some action items in the SYSTEM security context, and then delete itself; also works on cloud images. Storage FlashCopy Manager schedules are activated by using Windows System Account permissions. 0. Create the Job and Job Step. Are there application or domain specific  Can anyone tell me how to create a scheduled task using powershell that runs as the local system or local service?Everything works great except the call to  Suppose, we need to create a scheduled task that should run during startup (or at a specific time) and execute some PowerShell script or command. Search for PowerShell, right-click the top result, and select the Run as administrator option. Then use Set-ScheduledTask to change the startup account to LocalSystem or any another built-in account. The schtasks. The following PS-code example explains everything. I am using the Windows 10 GUI for the sake of this demonstration. In advanced, I checked "repeat task every" and set it to "1hour", but do I set "for a duration of" to "indefinitely" or "1 day"? Microsoft Windows Task Scheduler component is a standard part of Microsoft Windows operating system since Windows98. Step 8: Save the scheduled task. What do I want the scheduled task to do? Without specifying an action, there is no reason to create a scheduled task. de 2018 run powershell script as administrator: PowerShell Script not working through Task Scheduler: how to execute powershell script to run as  How to Create a Scheduled Task for PowerShell Script with Windows Task Scheduler? · In Program/script, Enter: C:\Windows\System32\WindowsPowerShell\v1. You can leave the “configure for” as the default (Vista/Server08) Trigger: Set it to run “On A Schedule” => Daily start at 12:05 AM Follow these easy steps to add your dailyjob. In General tab, you can set scheduler name and description about the task like  25 Haz 2020 Method 1: Run a task as different user with Scheduled Tasks. 0,4. Set the triggers, it can be weekly, daily or monthly. <#This code is provided AS-IS and  18 Eyl 2020 Creating a New Scheduled Task · Execute a PowerShell 7 Script · Run the account as the System account using the highest level · Run every day at 3  PowerShell script to create a scheduled task that runs a choco upgrade all at machine startup - Schedule-ChocoUpgradeAll. Step 4 – Click on the Triggers tab and set your schedule or event that will trigger the running of your PowerShell script. PowerShell provides commands to create scheduled tasks. Such a script can also always be started with system rights or as a "Network Service" (in this case the permissions of the computer are used for the network access). Click op Create Basic Task. Create a script to create the task and copy the PowerShell file. Give it a meaningful name. Open a command prompt window. 0 introduced new cmdlets for creating scheduled tasks, New-ScheduledTaskTrigger and Register-ScheduledTask, which make creating a scheduled task much easier and more convenient. at the next window, type powershell as the program script and the full path of the script file as the argument. To start, open Task Scheduler by clicking Start menu and typing Task Scheduler and click Create Basic Task… or Create Task… from the Actions pane. ps1". Step 5 – Click on the Actions tab and The PowerShell of Windows offers another quick option on Windows 8 and later. If the same commands work fine from normal powershell console and if you face issue only in Task Scheduler, then the problem might be the user account that you have configured for the schedule task. Suppose, we need to create a scheduled task to run at a specific time and execute some PowerShell script or command. Create your PowerShell script (for this example, I'll use C:\Scripts\Startup. The monitoring set. ps1 file (e. ps1 (changing the filename to whatever you used). Copying the file Creating Tasks with Task Scheduler. As previously stated, I included the options that I most often use — repeat every X indefinitely, run as specified user, and run with highest privileges. Then we will create the task itself and set the schedule to run every time the user logs onto the computer. Mark it as “Run whether user is logged in or not” and check the “run with highest privileges”. Create scheduled task folder. In the path i wrote about how to schedule a powershell script in Windows. schtasks can be run either on startup, timed, or as a one off execution For those who can use PowerShell 3. 16 Sep 2013 PowerShell v3 has a bunch of cmdlets that manage scheduled tasks. Copying the file Creating a New Scheduled Task. exe. exe --File C:\Scripts\Startup. You can see this is calling Webster’s admin script. I create a batch file for backing up the Sharepoint farm then i schedule it to run daily. My solution, rather than working with the API, is to create the world's smallest PowerShell host and compile it as a windows mode executable. Click the “Change User or Group” and select SYSTEM. Open Task scheduler –> Task Scheduler Library –> Create Task · 2. The command Send-MailMessage accepts the parameter -Credential. It also gets confusing in the wizard as soon as a PowerShell script has many parameters. Click here to download a zip file containing the ps1 script file. “Trigger” – Set to Daily and set the time to “7:30 AM”. Note: PsExec is a tool written by Mark Russinovich (included in the Sysinternals Suite) and can downloaded here. 4. Similarly, to create a new task in task scheduler using PowerShell comprises of several settings. 5 Click on “Actoins” tab If I manually execute the scheduled task via PowerShell Start-ScheduleTask, again, nothing seems to happen. the task doesn't run: Windows Task Scheduler can be a very useful tool to run your PowerShell scripts on boot, login, on a schedule or other events. the task doesn't run: With this example, you can learn how to use PowerShell scripts to collect WCI data for scheduled tasks. exe utility to report on scheduled tasks that you create in the Task Scheduler user interface or by using the AT command. PowerShell: Create Windows Scheduled Task to run Powershell script every hour If you are using a newer version of PowerShell, then by all means use the New-ScheduledTaskAction, New-ScheduledTaskTrigger, and Register-ScheduledTask and to create a Windows schedule task using PS scripting . “Action” – Set to Start a Program. A couple of quick examples I checked show the job running as SYSTEM in stead of a local admin account. 0 While writing the DSC configuration for some Jenkins slaves, I discovered the Register-ScheduledTask cmdlet only accepts string variables. The password is mandatory in case the "Run only if this user is logged on" option is unchecked. To run the program with administrator privileges, check the “Run with the highest Create the job trigger. 20 Jul 2019 PowerShell. Remedy the fact that you do not actually need the Wizard, but can create multiple scheduled tasks via PowerShell. . I have set mine to hourly in this example. To create a task using GUI (As shown below image) we need a few settings like the Name of the task, trigger, and Action. Here you have to make sure that the syntax of the argument is correct. The only output to be seen is in the Last Run Result column from the Task Scheduler, this will display the following Scheduled task is one of the useful feature in Windows Operating System enable to schedule to launch a program or to run some scripts at specified time, date or even when particular event occurred. The New-ScheduledTaskPrincipal cmdlet creates an object that contains a scheduled task principal. exe. Step 2 – Name the task, and set the security options (use an account that has the permissions to run your script and the commands within it, unless you are using the -Credentials parameter on your commandlets) Step 3 – Set your triggers. You can register a task to run any of the following application or file types: Win32 applications, Win16 applications, OS/2 applications, MS-DOS applications, batch files (*. the task doesn't run: Re: Powershell script via task scheduler not work as expected. psexec. Once you have created that GPO and linked it to your selected organizational unit (OU) or root domain, right-click it and select Edit. Open Task Scheduler by pressing “Windows+R” and then typing “taskschd. 0 on Windows 8 or Windows Server 2012 , new cmdlets will let you do it in a simple way when registering your scheduled task with the cmdlet Register-ScheduledTask and as argument -User "System" Note The Scheduled Task module first appeared with Windows PowerShell 3. Create Scheduled task using PowerShell: Posted: (1 week ago) To create PowerShell scheduled t a sks on Windows 10, use these steps: Open St a rt. Then take the following steps: 1. Use a scheduled task principal to run a task under the security context of a specified account. exe tool. So let’s create a task that will execute our script daily at 10 AM using the system account (SYSTEM). We want the task to do the following. Click “Create a task” and enter a name and description for the new task. Case 2 : Option 1. int GetHashCode() GetObjectData Method void GetObjectData(System. 0 on Windows 8 or Windows Server 2012, new cmdlets will let you do it in a simple way when registering your scheduled task with the cmdlet Register-ScheduledTask and as argument -User "System" Posted: (1 week ago) To create PowerShell scheduled t a sks on Windows 10, use these steps: Open St a rt. (move-item 'E:\System State Folder' 'E:\Backup Folder') Action : Start a Program, Program/script: PowerShell, Add arguments: -ExecutionPolicy Bypass, Start in: C:\Users\Administrator\Desktop\Test. I now open the Windows tasks scheduler and notice that the trigger Check Services is created in the folder PowerShell. Two things to consider. cmd), or any properly registered file type. In order to run this as a Scheduled Task in Windows I’d need to run it as SYSTEM (NT AUTHORITY\SYSTEM) – change the “Configure for:” section at the bottom to match the OS you’re using as well, for compatibility purposes. 54. Trying to troubleshoot these issues using Task Manager can be very difficult, since services and scheduled tasks are stored and displayed separately. When a user Logs on. One of these things is the action. How to Setup a PowerShell Script to Run as a Scheduled Task. 24 Mar 2015 Verify that the account the task runs as has the appropriate privileges for any systems that you query. I am having trouble finding the correct code to run a scheduled task as logged on user The schedule task uses the system account and not the current … 29 de dez. You can configure additional triggers if you like, say for the script to run every day on a specific time. com on a daily basis. You can leave the “configure for” as the default (Vista/Server08) Trigger: Set it to run “On A Schedule” => Daily start at 12:05 AM When the system is booted. powershellscript. In the Command: area, enter powershell. To create a scheduled task with PowerShell on Windows 10, use these steps: Open Start. The command Get-ScheduledTask returns all or select scheduled tasks of the local computer. Ability to wake up a machine  21 de set. Set the user account (preferably a service account with a password that doesn’t expire) Check the option to run whether the user is logged in or not. The Windows Task Scheduler has been a part of the Windows operating system for many years. Sadly this task will fail silently once it is run, and there is no helpful information to be found. When the task is registered. exe utility enables you to manage scheduled tasks on a local or remote Posted: (1 week ago) To create PowerShell scheduled t a sks on Windows 10, use these steps: Open St a rt. Step 2 – Open Windows Task Scheduler and click on “Create Task” option on right. If PowerShell script works fine when run manually but hangs or keep running in Task Scheduler then create a batch file and set the above settings. 3. Create a Scheduled Task. One of my tasks is to install a web based product using powershell. I am scheduling a task through code. to make sure this task is run under the system context. 10 Feb 2021 However, you have to execute some commands to get the job done. de 2017 Then right-click and select "Create a GPO in this domain, and Link it here. 0\powershell. This can be found in the Start menu, under Start > Administrative Tools. Type the I had a similar challenge when trying to create a scheduled task on Powershell to copy files to a mapped drive. This post explains the subtleties of running the script -- or, more generally, any PowerShell script -- using the Windows Task Scheduler To start, open task scheduler by clicking start menu and typing task scheduler and click create basic task… or create task… from the actions pane. I’ll show you two ways, one from the plain GUI (yes, I know…gross) and then the cool-kids way, using PowerShell…to create a scheduled task that runs PowerShell. In my example, I want the task to start a PowerShell script as system. Register-ScheduledTask  4 Oca 2010 For those who can use PowerShell 3. By default the "Run as" user is NT AUTHORITY\SYSTEM. 0 and 4. You can create tasks and schedule based on the above response. I typically just create the Scheduled Tasks manually, but that is becoming less desirable as I work on larger SharePoint engagements… To start, open task scheduler by clicking start menu and typing task scheduler and click create basic task… or create task… from the actions pane.

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# How do you find the vertex and axis of symmetry for a quadratic equation y = -x^2 + 6x -9?

Jul 11, 2015

The vertex is at ($3 , 0$).
The axis of symmetry is $x = 3$.

#### Explanation:

The standard form for the equation of a parabola is

$y = {a}^{2} + b x + c$

$y = - {x}^{2} + 6 x - 9$

So

$a = - 1$, $b = 6$, and $c = - 9$.

Vertex

Since $a < 0$, the parabola opens downwards.

The $x$-coordinate of the vertex is at

x = –b/(2a) = -6/(2(-1)) = -6/-2 = 3.

Insert this value of $x$ back into the equation.

y = -x^2 + 6x - 9 = -3^2 + 6×3 - 9 = -9 + 18 – 9 = 0

The vertex is at ($3 , 0$).

Axis of symmetry

The axis of symmetry must pass through the vertex, so

The axis of symmetry is $x = 3$.


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filehash v2.4-2

0

0th

Percentile

Simple Key-Value Database

Implements a simple key-value style database where character string keys are associated with data values that are stored on the disk. A simple interface is provided for inserting, retrieving, and deleting data from the database. Utilities are provided that allow 'filehash' databases to be treated much like environments and lists are already used in R. These utilities are provided to encourage interactive and exploratory analysis on large datasets. Three different file formats for representing the database are currently available and new formats can easily be incorporated by third parties for use in the 'filehash' framework.

Functions in filehash

 Name Description createS Create/Initialize Stack stack-class Class "stack" dbLoad Load database into environment dbInit Simple file-based hash table stackqueue Operations on Stacks/Queues queue-class Class "queue" filehashOption Set filehash options filehashFormats List and register filehash formats createQ Create/Initialize Queue dumpObjects Dump objects of database filehash-class Class "filehash" No Results!


text:
When do submanifolds lie in the same homology class? - MathOverflow [closed] most recent 30 from http://mathoverflow.net 2013-05-23T05:55:21Z http://mathoverflow.net/feeds/question/40934 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/40934/when-do-submanifolds-lie-in-the-same-homology-class When do submanifolds lie in the same homology class? Henry Wegener 2010-10-03T14:24:34Z 2010-10-03T14:45:51Z
Hello,

this may be a trivial question, but I am not very familiar with the topic. Let (M,g) be a Riemannian Manifold. (In fact, we don't need the metric here.)

What exactly does it take for two k-submanifolds $S$ and $S'$ to lie in the same homology class? And why does that imply $~ \int_S ~ \omega = \int_{S'} ~ \omega ~$, where $\omega$ is a closed differential form on M.

This must be somehow a consequence of Stokes' Theorem. I would be pleased with an answer for Dummies. :)

$~$

Greetings,

Henry
 http://mathoverflow.net/questions/40934/when-do-submanifolds-lie-in-the-same-homology-class/40937#40937 Answer by Jim Conant for When do submanifolds lie in the same homology class? Jim Conant 2010-10-03T14:45:51Z 2010-10-03T14:45:51Z
By triangulating each manifold $S$ and $S'$, you can regard them as sums of singular simplices. (A singular simplex is a continuous map $f\colon \Delta^n\to M$.) So the very simple answer is that $S$ and $S'$ are the same homology class if and only if they are the boundary of some sum of singular simplices. This can happen if, for example, there is a map of an oriented manifold of one higher dimension into $M$ whose boundary is the disjoint union $S\cup -S'$. If all the singular simplices are smooth maps, then Stokes theorem indeed tells you that the integral along the boundary of each singular simplex is zero, which then implies that the integral $\int_{S\cup-S'}\omega=0$, or $\int_S\omega=\int_{S'}\omega$. Someone else can probably comment on why you can pass from the topological to the smooth category.


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# American Institute of Mathematical Sciences

February  2007, 1(1): 13-28. doi: 10.3934/ipi.2007.1.13

## The interior transmission problem

 1 Department of Mathematical Sciences, University of Delaware, Newark, Delaware 19716, United States 2 Department of Mathematics and Statistics, University of Helsinki, P.O. Box 68 FI-00014 3 Department of Mathematics, University of Washington, Seattle, Washington 98195, United States

Received  July 2006 Revised  October 2006 Published  January 2007

The interior transmission problem is a boundary value problem that plays a basic role in inverse scattering theory but unfortunately does not seem to be included in any existing theory in partial differential equations.This paper presents old and new results for the interior transmission problem ,in particular its relation to inverse scattering theory and new results on the spectral theory associated with this class of boundary value problems.
Citation: David Colton, Lassi Päivärinta, John Sylvester. The interior transmission problem. Inverse Problems and Imaging, 2007, 1 (1) : 13-28. doi: 10.3934/ipi.2007.1.13
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2021 Impact Factor: 1.483


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# Sequence Equation

See the original problem on HackerRank.

## Solutions

This simple problem can be solved by memorizing the inverse of $$p$$ into a fast-lookup container like a map/dictionary or even into an array (since the domain spans from $$1$$ to $$N$$).

Since all the associations are unique, $$p$$ is invertible.

Basically, the key of the map is the value of $$p$$ and the value is the index.

Here is a C++ implementation:

  1 2 3 4 5 6 7 8 9 10 11  int N, y; cin >> N; unordered_map f; for (auto i=0; i> y; f[y] = i+1; } for (auto i=0; i

We can even use a vector instead of a map:

  1 2 3 4 5 6 7 8 9 10 11  int N, y; cin >> N; vector f(N+1); for (auto i=0; i> y; f[y] = i+1; } for (auto i=0; i


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# The area of a plan of an old survey plotted on a sheet is found to have shrunk so that a line originally 10 cm long now measures 9.7 cm only. Calculate the shrinkage factor.

This question was previously asked in
SSC JE CE Previous Year Paper 10 (Held on 30 Oct 2020 Evening)
View all SSC JE CE Papers >
1. 0.97
2. 9.7
3. 97
4. 1.03

Option 1 : 0.97
Free
ST 1: Building Material and Concrete Technology
18752
20 Questions 20 Marks 12 Mins

## Detailed Solution

Explanation:

Original length of line = 10 cm

Length after shrinkage of line = 9.7 cm

$${\bf{Shrinkage}}{\rm{ }}{\bf\ {Factor}} = \frac{{{\bf{Shrunk}}\ {\rm{ }}{\bf{length}}}}{{{\bf{Original}}{\rm{ }}{\bf\ {length}}}}$$

$${\bf{Shrinkage}}{\rm{ }}{\bf{Factor}} = \frac{{9.7}}{{10}}$$

Shrinkage Factor = 0.97