5084706
Pipes: linguistic support for ordered asynchronous invocations
We describe pipes, a new linguistic mechanism for sequences of ordered asynchronous procedure calls in multiprocessor systems. Pipes allow a sequence of remote invocations to be performed in order, but asynchronously with respect to the calling thread. Using pipes results in programs that are easier to understand and debug than those with explicit synchronization between asynchronous invocations. The semantics of pipes make no assumptions about the underlying architecture, which enhances code portability. However, the implementation of pipes by the language compiler can be optimized so as to take advantage of any underlying message ordering a particular architecture may provide. Pipes also provide application-transparent flow control for asynchronous invocations and are able to throttle invocations from multiple calling threads. We present four implementations of pipes and show that the performance and space overheads associated with pipes are low.
10974617
PRELUDE: A System for Portable Parallel Software
Abstract : In this paper we describe PRELUDE, a programming language and accompanying system support for writing portable MIMD parallel programs. PRELUDE supports methodology for designing and organizing parallel programs that makes them easier to tune for particular architectures and to port to new architectures. It builds on earlier work on Emerald, Amber, and various Fortran extensions to allow the programmer to divide programs into architecture-dependent and architecture-independent parts, and then to change the architecture-dependent parts to port the program to a new machine or to tune its performance on a single machine. The architecture-dependent parts of a program are specified by annotations that describe the mapping of a program onto a machine. PRELUDE provides a variety of mapping mechanisms similar to those in other systems, including remote procedure call, object migration, and data replication and partitioning. In addition, PRELUDE includes novel migration mechanisms for computations based on a form of continuation passing. The implementation of object migration in PRELUDE uses a novel approach based on fixup blocks that is more efficient than previous approaches, and amortizes the cost of each migration so that the cost per migration drops as the frequency of migrations increases.
42642346
Multi-version memory: software cache management for concurrent B-trees
The authors describe a new concurrent B-tree algorithm. The algorithm is designed to work well in large-scale parallel or distributed systems in which the number of processors sharing the tree is large or the communication delay between processors (or between processors and the global memory for a shared-memory system) is large relative to the speed of local computation. The basis of the algorithm is an abstraction that is similar to coherent shared memory, but provides a weaker semantics; this abstraction is called multiversion memory. Multi-version memory uses caches but weakens the semantics of ordinary shared memory by allowing process reading data to be given an old version of the data. This semantics is adequate for the non-leaf nodes in the B-tree algorithms presented.<<ETX>>
14708626
Computation migration: enhancing locality for distributed-memory parallel systems
We describe computation migration, a new technique that is based on compile-time program transformations, for accesing remote data in a distributed-memory parallel system. In contrast with RPC-style access, where the access is performed remotely, and with data migration, where the data is moved so that it is local, computation migration moves part of the current thread to the processor where the data resides. The access is performed at the remote processor, and the migrated thread portion continues to run on that same processor; this makes subsequent accesses in the thread portion local.
We describe an implementation of computation migration that consists of two parts: an implementation that migrates single activation frames, and a high-level language annotation that allows a programmer to express when migration is desired. We performed experiments using two applications; these experiments demonstrate that computation migration is a valuable alternative to RPC and data migration.
6861036
Practical factorization of univariate polynomials over finite fields
Research presented fort to establish state-of-the-art Kent State University “ Kent, Ohio 44242-0001 here is part of an effactoring routines for polynomials. The foundation of such algorithms lies in the efficient factorization over a finite field GF(p~). The Cantor-Zassenhaus algorithm together with innovative ideas suggested by others is compared with the Berlekamp algorithm. The studies led us to design a hybrid algorithm that combine the strengths of the different approaches. The algorithms are also implemented and machine timings are obtained to measure the performance of these algorithms.
5684281
Hopf bifurcation and oscillations in a communication network with heterogeneous delays
In this paper, we investigate stability, bifurcation and oscillations arising in a single-link communication network model with a large number of heterogeneous users adopting a Transmission Control Protocol (TCP)-like rate control scheme with an Active Queue Management (AQM) router. In the system considered, different user delays are known and fixed but taken from a given distribution. It is shown that for any given distribution of delays, there exists a critical amount of feedback (due to AQM) at which the equilibrium loses stability and a limit cycling solution develops via a Hopf bifurcation. The nature (criticality) of the bifurcation is investigated with the aid of Lyapunov-Schmidt perturbation method. The results of the analysis are numerically verified and provide valuable insights into dynamics of the AQM control system.
22564863
The TMS390C602A floating-point coprocessor for Sparc systems
A recent Sparc (scalable processor architecture) processor consists of a two-chip configuration, containing the TMS390C601 integer unit (IU) and the TMS390C602A floating-point unit (FPU). The second device, an innovative coprocessor that lets the processor execute single- or double-precision floating-point instructions concurrently with IU operations is described. Dedicated floating-point hardware in the FPU increases the performance of the system. Running at clock periods as small as 20 ns, the chip should deliver 5.5 million double-precision floating-point operations per second under the Linpack benchmark (50-MHz clock rate). The FPU provides single- and double-precision arithmetic functions: addition, subtraction, multiplication, division, square root, compare, and convert. To minimize its math unit's latency, the FPU uses a highly parallel architecture requiring separate math units to optimize additions and multiplications. Traps stop the execution of a program to jump to software routine for handling data-dependent errors or to execute instructions not implemented in the hardware. Benchmark results are presented.<<ETX>>
38040297
A Mammography Database and View System for the African American Patients
In this research, we have obtained and scanned mammography films (within the last ten years) of African American women treated at Howard University Hospital Radiology Department, constructed a database using the digitized mammography images, and developed an image viewing system to display these digital mammograms. The images are scanned with the high resolution Kodak LS85 laser scanner. The digital mammography database is powered by MySQL and PHP. It also has a Web-based search engine (with secure access) so that the information can be made accessible to all medical team members. The image viewing software, D-Viewer, is coded in C# and is intended to help medical professionals view and retrieve large data sets in near real time. We have already digitized 260 cases (one case per patient, twenty to forty films per case). We also have developed a MySQL-based image database, and a PHP-based web-search engine to retrieve cases that have masses (benign or malignant) or calcifications (benign or malignant). This database has been evaluated by medical professionals and the experimental results obtained so far are very promising (high image qualities, fast access time). We are currently developing an image content-based retrieval function for the database system in order to provide improved search capability for the medical professionals.
3478780
Time-domain simulation of uniform and nonuniform multiconductor lossy lines by the method of characteristics
A numerical technique to compute the time-domain response of multiconductor lossy uniform and nonuniform lines terminated in general nonlinear elements is presented. The technique is based on the method of characteristics and is used to study the propagation characteristics of multiple coupled uniform and nonuniform transmission line structures terminated in linear and nonlinear elements. This includes signal delay, distortion and crosstalk in interconnections in high-frequency analog and digital integrated circuits and chip modules. >