[petsc-users] Why the code needs much longer time when I use MPI

[Ji Zhang]

Dear all,
I'm using KSP included in PETSc to solve some linear equations. The code
runs well if I do not use mpirun. However, the running duration since
increase linearly with the number of CUPs.

The solve method is gmres and without precondition method. For a same case,
it need about 4.9s with 'mpirun -n 1', which is about 7.9s if I use 'mpirun
-n 2', and 12.5s when I use 'mpirun -n 4'. It looks like that I need double
time when I use double CUPs. Is there any one could give me some
suggestion? Thanks.

Best,
Regards,
Zhang Ji, PhD student
Beijing Computational Science Research Center
Zhongguancun Software Park II, No. 10 Dongbeiwang West Road, Haidian
District, Beijing 100193, China
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