[petsc-users] Compile flags for a Blue Gene\Q

[Christian Klettner]

Dear PETSc group,
We have been given access to a Blue Gene\Q system to run code we normally
run on a traditional cluster architecture. We have ported the code
successfully and run some jobs using 16 cores per node however the
performance is roughly four times slower to that of a Xeon processor. We
expect less performance (due to the slower chips) however this seems a bit
excessive. One problem we think is that we are not using all four hardware
threads per core. To achieve this do we need to use a threaded version of
PETSc? Could someone suggest the additional arguments required to make use
of the pthreads when launching an MPI job? We are using the Blue Gene MPI
libraries but are currently unable to use the ESSL blas libraries. We
found the example compile flags for a Blue Gene \P in the PETSc package
but were wondering if anyone had compile flags which they would recommend
for a Blue Gene\Q?
Best regards,
Christian