30629384
Ordering Unsymmetric Matrices into Bordered Block Diagonal Form for Parallel Processing
Large, sparse, unsymmetric systems of linear equations appear frequently in areas such as chemical engineering. One way of speeding up the solution of these linear systems is to solve them in parallel by reordering the unsymmetric matrix into a bordered block-diagonal (BBD) form. A multilevel ordering algorithm is presented in this paper. Numerical results of the algorithm are given to demonstrate that this algorithm gives better orderings than existing algorithms.
13831969
The Communication Performance of the Cray T3D and its Effect on Iterative Solvers
On many distributed memory systems, such as workstation clusters or the Intel iPSC/860, the multigrid algorithm suffers from having extensive communication requirements and, in general, it is not very competitive in comparison to the conjugate gradient algorithm. This is in contrast to the sequential problem whereby the multigrid algorithm is very effective in reducing the global residual, particularly for very large linear systems of equations. These two algorithms are now compared on the Cray T3D for solving very large systems of linear equations (resulted from grids of the order 2563 cells). The communication performance of the Cray T3D is first measured by the standard ping-pong tests and also by practical communication tasks that are found frequently in CFD calculations. It is found that the Cray T3D has a low latency (≈ 6 μs) and a high bandwidth interprocessor communication (120 MB/s) when the low-level intrinsic communication routines are used. As a result, the multigrid algorithm is found to be very competitive when compared with the conjugate gradient algorithm for solving the very large linear systems arising from the Direct Numerical Simulation of turbulent Combustion (DNSC). Results are contrasted by those on the Intel iPSC/860.
9413805
A numerical evaluation of sparse direct solvers for the solution of large sparse symmetric linear systems of equations
In recent years a number of solvers for the direct solution of large sparse symmetric linear systems of equations have been developed. These include solvers that are designed for the solution of positive definite systems as well as those that are principally intended for solving indefinite problems. In this study, we use performance profiles as a tool for evaluating and comparing the performance of serial sparse direct solvers on an extensive set of symmetric test problems taken from a range of practical applications.
23412949
An optimal migration algorithm for dynamic load balancing
14708530
An Evaluation of Sparse Direct Symmetric Solvers: An Introduction and Preliminary Findings
In recent years a number of solvers for the direct solution of large sparse, symmetric linear systems of equations have been developed. These include solvers that are designed for the solution of positive-definite systems as well as those that are principally intended for solving indefinite problems. The available choice can make it difficult for users to know which solver is the most appropriate for their applications. In this study, we use performance profiles as a tool for evaluating and comparing the performance of serial sparse direct solvers on an extensive set of symmetric test problems taken from a range of practical applications.
40122351
Numerical Experiences with Partitioning of Unstructured Meshes
Abstract The problem of partitioning unstructured meshes for parallel computing is considered. Four existing algorithms as well as a new hybrid algorithm are tested. The numerical results favour the recursive spectral bisection algorithm and the hybrid algorithm. A generalisation of the recursive spectral bisection algorithm to deal with an arbitrary number of processors is discussed.
17520632
Global optimization in clustering using hyperbolic cross points
Erich Novak and Klaus Ritter developed in 1996 a global optimization algorithm that uses hyperbolic cross points (HCPs). In this paper we develop a hybrid algorithm for clustering called CMHCP that uses a modified version of this HCP algorithm for global search and the alternating optimization for local search. The program has been tested extensively with very promising results and high efficiency. This provides a nice addition to the arsenal of global optimization in clustering. In the process, we also analyze the smoothness of some reformulated objective functions.
5939586
Simultaneous time slack budgeting and retiming for dual-Vdd FPGA power reduction
Field programmable dual-Vdd interconnects are effective to reduce FPGA power. Assuming uniform length interconnects, existing work has developed time slack budgeting to minimize power based on estimating the lower bound of power reduction using dual-Vdd for given time slack. In this paper, we show that such lower bound estimation cannot be extended to mixed length interconnects that are used in modern FPGAs. We develop a technique to estimate power reduction using dual-Vdd for mixed length interconnects, and apply linear programming (LP) to solve slack budgeting to minimize power for mixed length interconnects. Experiments show 53% power reduction on average compared to single-Vdd interconnects. Furthermore, this paper presents a simultaneous retiming and slack budgeting algorithm to reduce power in dual-Vdd FPGAs considering placement and flip-flop binding constraints. The algorithm is based on mixed integer and linear programming (MILP) and achieves up to 20% power reduction compared to retiming followed by slack budgeting. We propose a runtime efficient flow to apply simultaneous retiming and slack budgeting only when it is necessary. To the best of our knowledge, this paper is the first; in-depth study of simultaneous retiming and slack budgeting for dual-Vdd programmable FPGA power reduction while considering layout constraints
5185627
OpenMP for networks of SMPs
In this paper we present the first system that implements OpenMP on a network of shared-memory multiprocessors. This system enables the programmer to rely on a single, standard, shared-memory API for parallelization within a multiprocessor and between multiprocessors. It is implemented via a translator that converts OpenMP directives to appropriate calls to a modified version of the TreadMarks software distributed memory system (SDSM). In contrast to previous SDSM systems for SMPs, the modified TreadMarks uses POSIX threads for parallelism within an SMP node. This approach greatly simplifies the changes required to the SDSM in order to exploit the intra-node hardware shared memory. We present performance results for six applications (SPLASH-2 Barnes-Hut and Water; NAS 3D-FFT, SOR, TSP and MGS) running on an SP2 with four four-processor SMP nodes. A comparison between the threaded implementation and the original implementation of TreadMarks shows that using the hardware shared memory within an SMP node significantly reduces the amount of data and the number of messages transmitted between nodes, and consequently achieves speedups up to 30% better than the original versions. We also compare SDSM against message passing. Overall, the speedups of multithreaded TreadMarks programs are within 7-30% of the MPI versions.
8326799
Topology-Aware Peer-to-Peer On-demand Streaming
In this paper, we consider large-scale high-bandwidth on-demand media streaming in a dynamic and heterogeneous environment. We present MetaStream, a scalable and distributed content discovery protocol that enables clients across the Internet to self-organize into a topology-aware overlay network, in which they can “cache and relay” a stream among nearby peers. We present the design and implementation of MetaStream and show experimental results obtained in a large-scale emulated environment. Our evaluation shows that MetaStream distributes relaying load among the clients in a topology-aware manner, imposing low link cost to the underlying network and low streaming load on the media server. MetaStream is also highly resilient to node or network failures and is capable of quickly recovering the streaming quality at clients even at high failure rates.
62602047
A self-organizing flock of Condors