Objective: Utilize parallel computers and workstation cluster for improved performance of computational fluid dynamics codes. Produce a robust code that is portable across a variety of platforms and that uses parallel technology when available and appropriate.
Approach: Parallelize the serial multiple-zone Navier-Stokes flow solver OVERFLOW using domain decomposition, each zone being one domain. Use a manager/worker paradigm, and use the Parallel Virtual Machine (PVM) message-passing library. The manager/worker paradigm does not scale well on higher connectivity machines such as the IBM SP2. Use a peer-to-peer communication pattern to improve scalability.
Accomplishments: Parallel capability was added to OVERFLOW as part of the standard OVERFLOW package; this parallel capability will be supported. The source code requires no modification for different platforms. The parallel code is robust in that it can recover from failure of a worker machine. The speedup depends on the ratio (no. of points in largest zone) / (total no. of points). For a sample 6-zone case with 1 million grid points, with the largest zone having 40% of the total (so the maximum speedup is 2.5), timing on a network of SGI machines found a speedup of 2. A peer-to-peer communication pattern, halving the communication volume and improving scalability, was implemented in a prototype code. The resultant code has been executed on Ethernet, FDDI, HiPPI, and proprietary switch-based networks linking various vendors' machines. Problems with more than 3 million grid points have been solved.
Significance:The portable parallel code can utilize workstation clusters during nights and weekends to improve productivity. The availability of a portable and scalable code will allow faster and less costly design cycles.
Status/Plans: The parallel code has been released to customers. It will continue to be supported. Parallelization of a new automated preprocess code required for optimization and multidisciplinary simulations is underway.
Point(s) of Contact:
Dennis Jespersen
NASA/Ames Research Center
jesperse@nas.nasa.gov
(415) 604-6742
Dr. Christopher A. Atwood
NASA/Ames Research Center
atwood@nas.nasa.gov
(415) 604-3974
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