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  • Computer Systems  (5)
  • Communications and Radar
  • Numerical Analysis
  • TEM
  • 1995-1999  (5)
  • 1935-1939
  • 1925-1929
  • 1996  (5)
  • 1
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    Satisfiability Test with Synchronous Simulated Annealing on the Fujitsu AP1000 Massively-Parallel Multiprocessor (1996)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Solving the hard Satisfiability Problem is time consuming even for modest-sized problem instances. Solving the Random L-SAT Problem is especially difficult due to the ratio of clauses to variables. This report presents a parallel synchronous simulated annealing method for solving the Random L-SAT Problem on a large-scale distributed-memory multiprocessor. In particular, we use a parallel synchronous simulated annealing procedure, called Generalized Speculative Computation, which guarantees the same decision sequence as sequential simulated annealing. To demonstrate the performance of the parallel method, we have selected problem instances varying in size from 100-variables/425-clauses to 5000-variables/21,250-clauses. Experimental results on the AP1000 multiprocessor indicate that our approach can satisfy 99.9 percent of the clauses while giving almost a 70-fold speedup on 500 processors.
    Keywords: Computer Systems
    Type: NASA-CR-200964 , NAS 1.26:200964 , RIACS-TR-96-07 , 10th ACM International Conference on Supercomputing; May 25, 1996 - May 28, 1996; Philadelphia, PA; United States
    Format: application/pdf
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  • 2
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    Global Load Balancing with Parallel Mesh Adaption on Distributed-Memory Systems (1996)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Dynamic mesh adaption on unstructured grids is a powerful tool for efficiently computing unsteady problems to resolve solution features of interest. Unfortunately, this causes load imbalance among processors on a parallel machine. This paper describes the parallel implementation of a tetrahedral mesh adaption scheme and a new global load balancing method. A heuristic remapping algorithm is presented that assigns partitions to processors such that the redistribution cost is minimized. Results indicate that the parallel performance of the mesh adaption code depends on the nature of the adaption region and show a 35.5X speedup on 64 processors of an SP2 when 35% of the mesh is randomly adapted. For large-scale scientific computations, our load balancing strategy gives almost a sixfold reduction in solver execution times over non-balanced loads. Furthermore, our heuristic remapper yields processor assignments that are less than 3% off the optimal solutions but requires only 1% of the computational time.
    Keywords: Computer Systems
    Type: NASA-CR-202186 , NAS 1.26: 202186 , RIACS-TR-96-16 , Supercomputing 1996; Nov 17, 1996 - Nov 22, 1996; Pittsburgh, PA; United States
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  • 3
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    Global Load Balancing with Parallel Mesh Adaption on Distributed-Memory Systems (1996)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Dynamic mesh adaptation on unstructured grids is a powerful tool for efficiently computing unsteady problems to resolve solution features of interest. Unfortunately, this causes load inbalances among processors on a parallel machine. This paper described the parallel implementation of a tetrahedral mesh adaption scheme and a new global load balancing method. A heuristic remapping algorithm is presented that assigns partitions to processors such that the redistribution coast is minimized. Results indicate that the parallel performance of the mesh adaption code depends on the nature of the adaption region and show a 35.5X speedup on 64 processors of an SP2 when 35 percent of the mesh is randomly adapted. For large scale scientific computations, our load balancing strategy gives an almost sixfold reduction in solver execution times over non-balanced loads. Furthermore, our heuristic remappier yields processor assignments that are less than 3 percent of the optimal solutions, but requires only 1 percent of the computational time.
    Keywords: Computer Systems
    Type: NASA-CR-203532 , NAS 1.26:203532 , NAS-96-013 , Supercomputing 1996; Nov 17, 1996 - Nov 22, 1996; Pittsburgh, PA; United States
    Format: application/pdf
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  • 4
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    Parallel Implementation of an Adaptive Scheme for 3D Unstructured Grids on the SP2 (1996)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Dynamic mesh adaption on unstructured grids is a powerful tool for computing unsteady flows that require local grid modifications to efficiently resolve solution features. For this work, we consider an edge-based adaption scheme that has shown good single-processor performance on the C90. We report on our experience parallelizing this code for the SP2. Results show a 47.OX speedup on 64 processors when 10% of the mesh is randomly refined. Performance deteriorates to 7.7X when the same number of edges are refined in a highly-localized region. This is because almost all mesh adaption is confined to a single processor. However, this problem can be remedied by repartitioning the mesh immediately after targeting edges for refinement but before the actual adaption takes place. With this change, the speedup improves dramatically to 43.6X.
    Keywords: Computer Systems
    Type: NASA-TM-112033 , NAS 1.15:112033 , NAS-96-011 , International Workshop on Parallel Algorithms for Irregularly Structured Problems (IRREGULAR''96); Aug 19, 1996 - Aug 21, 1996; Santa Barbara, CA; United States
    Format: application/pdf
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  • 5
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    Impact of Load Balancing on Unstructured Adaptive Grid Computations for Distributed-Memory Multiprocessors (1996)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The computational requirements for an adaptive solution of unsteady problems change as the simulation progresses. This causes workload imbalance among processors on a parallel machine which, in turn, requires significant data movement at runtime. We present a new dynamic load-balancing framework, called JOVE, that balances the workload across all processors with a global view. Whenever the computational mesh is adapted, JOVE is activated to eliminate the load imbalance. JOVE has been implemented on an IBM SP2 distributed-memory machine in MPI for portability. Experimental results for two model meshes demonstrate that mesh adaption with load balancing gives more than a sixfold improvement over one without load balancing. We also show that JOVE gives a 24-fold speedup on 64 processors compared to sequential execution.
    Keywords: Computer Systems
    Type: NASA-TM-112034 , NAS 1.15:112034 , NAS-96-012 , IEEE Symposium on Parallel and Distributed Processing (SPDP''96); Oct 23, 1996 - Oct 26, 1996; New Orleans, LA; United States
    Format: application/pdf
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