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8. Performance & scalability

The SPARTA distribution includes a bench sub-directory with several sample problems. The Benchmarks page of the SPARTA WWW Site gives timing data for these problems run on different machines, for both strong and weak scaling scenarioes:

For each problem there is an input script and sample log file outputs on different machines and different numbers of processors. E.g. a log file like means the the free molecular problem with 1 million grid cells ran on P processors of machine "foo".

Each can be run as a serial benchmark (on one processor) or in parallel. In parallel, all the benchmarks can be run as a fixed-size problem, meaning the same problem is run on various numbers of processors (strong scaling). They can also be run as scaled-size problem, if the problem size is increased with the number of processors (weak scaling).

Here is an example of how to run the benchmark problems. See the bench/README file for more details.

1-processor runs:

spa_g++ -v x 100 -v y 100 -v z 100 <
spa_g++ -v x 100 -v y 100 -v z 100 < in.collide
spa_g++ -v x 50 -v y 50 -v z 50 < in.sphere 

32-processor runs:

mpirun -np 32 spa_g++ -v x 100 -v y 100 -v z 100 <
mpirun -np 32 spa_g++ -v x 100 -v y 100 -v z 100 < in.collide
mpirun -np 32 spa_g++ -v x 50 -v y 50 -v z 50 < in.sphere 

Note that the benchmark scripts define variables that can be set from the command line that determine the size of problem that is run. Specifically, the x,y,z variables specify the grid size (e.g. 100x100x100) that is used, and variable n specifies the number of particles (10 per grid cell in this case).