MPI taking so much VIRT memory

[mrobin]

Hi,
I have a fortran program compiled with ifort and openMPI and I experienced a strange behaviour - when runing at one processor, it takes about 105M of VIRT memory (which is fine) but when I run it on 2 processors ( mpirun -np 2 ...) each process takes about 550MB of virt memory. There is nothing in the code that would scale with the number of processes and the amount of SHR memory fits well ( 44 MB with one proc and cca 52MB altogether with 2 procs). Any ideas why does it need so much memory?

[William_M_Intel1]

It could be that OpenMPI is pre-allocating a lot of message buffers.

Can you try the same experiment with Intel MPI? If the memory consumption is still too high, Intel MPI provides knobs that you can turn to reduce memory consumption.

--Bill

[umar]

Do you happen to use "contains" statement? I remember long time ago
that with contains somehow the memory usage was much larger.