[petsc-users] Using direct solvers in parallel

[Thomas Witkowski]

Am 15.05.2012 10:00, schrieb Dave May:
> Ah okay. Thanks for the timings.
>
> Have you monitored the CPU usage when you using umfpack?
> On my machine, it's definitely not running on a single process,
> so I wouldn't consider it a sequential solver.
>
>
>
Yes, the CPU usage is 100% and not more. If you see umfpack using more 
than 1 core its because your BLAS library is compiled for multi-thread 
using. MKL and ACML can do this. In this case just set the environment 
variable OMP_NUM_THREADS to 1. When I use the multi-threaded version of 
MKL, using more than 1 threads is SLOWER than the sequential run.

Thomas