[petsc-users] behavior of running same codes on different clusters many times

[Xiangdong]

Hello everyone,

When I ran the same petsc codes on different clusters many times, one
cluster always produces the same results, while the other one varies in
terms of number of iterations for SNES and KSP convergence. If the problem
is ill-conditioned, the round-off errors may cause different number of
iterations to converge. However, what puzzles me is that the number of
iterations on one machine is always the same while the other varies. I use
same codes with same version of PETSc. The differences I can think about
are MPI implementations (mvapich2 vs openmpi), compiler (icc vs gcc) and
the network between the nodes. Could these factors cause these different
behaviors?

Thank you.

Best,
Xiangdong
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