MIMD

Types of Computers. Computers can be classified by Flynn s taxonomy (19). The three important classes are SISD single instmction, single data SIMD single instmction, multiple data and MIMD multiple instmctions, multiple data. 

MIMD Multicomputers. Probably the most widely available parallel computers are the shared-memory multiprocessor MIMD machines. Examples include the multiprocessor vector supercomputers, IBM mainframes, VAX minicomputers. Convex and AUiant rninisupercomputers, and SiUcon... 

The Advanced Flexible Processor is a unique entry into the multiprocessing field. It provides the dynamic capabilities offered by an MIMD machine with advanced features provided by the interprocessor ring communications network efficient utilization of the system processors is therefore effected. Within each Advanced Flexible Processor, dynamic multiple chaining can be achieved due to the superior flexibility of the... 

The proposed standard may be obtained using anonymous file transfer from titan.cs.rice.edu (in public/HPFF/draft). An effort commenced January 1994 to extend the HPF proposal to accommodate irregular data distributions and to support parallel 1/O and more complex data structures, as well as task-driven MIMD computation. Additional information is available by sending electronic mail to hpff-info cs.rice.edu. 

Each vendor of MIMD parallel machines has a proprietary messagepassing library. However, many portable libraries, varying in quality and functionality, are available both commercially and in the public domain. 

Message passing remains the main programming model for developing new parallel chemistry applications. This is because of the wide availability of portable message-passing tools, the inherent portability and simplicity of the model, its close relationship to the architecture of parallel machines, and the historical lack of support for other models by MIMD MPP vendors. 

For MIMD shared-memory environments, the evaluation facility is likely to be based on per-processor events and states that are explicitly defined by the programmer and/or automatically defined by the programming environment. There is wide variation in the level of detail that can be obtained by automatic instrumentation. Information may be provided at the level of proce-... 

A Transputer-based systolic loop implementation for the simulation of rigid polyatomic molecules described by Craven and Pawley revealed that in contrast to many problems on MIMD computers, the main loss of efficiency arose not from the time spent in communication between processors but, rather, from certain extra calculation and addressing work that was deemed inevitable in the parallel decomposition of the problem, and from a slight load imbalance. This study provided an excellent practical example of the ability of the Transputer to communicate and calculate in parallel, with minimal degradation of the computation rate, and provided very encouraging timing comparisons with the Cray X-MP. 

As part of a major research program involving MD simulations of large biopolymers, Schulten and co-workers i8,234,237-240 60-node MIMD... 

Based on the wealth of experience to date, there can be little doubt that the MIMD programming model is the only one that provides sufficient flexibility to embrace all the data structures and computational enhancements that are routinely exploited in MD codes on serial and vector machines. 

Each of the five steps demonstrated different parallel efficiencies. Steps two and four were the most intensive in terms of computation. The implementation by Kuppermann and co-workers obtained better than 80% efficiency for up to 64 nodes on the Caltech/JPL Mark Illfp MIMD computer for step two.275 For large global matrix dimensions, step four was 40% efficient on 64 nodes and —80% efficient on 8 nodes. 

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