MPI memory leak

Question

I am writing some code that uses MPI and I was keeping noticing some memory leaks when running it with valgrind. While trying to identify where the problem was, I ended up with this simple (and totally useless) main:

#include "/usr/include/mpi/mpi.h"

int main(int argc,char** argv)
{
MPI_Init(&argc, &argv);
MPI_Finalize();
return 0;
}

As you can see, this code doesn't do anything and shouldn't create any problem. However, when I run the code with valgrind (both in the serial and parallel case), I get the following summary:

==28271== HEAP SUMMARY:

==28271== in use at exit: 190,826 bytes in 2,745 blocks

==28271== total heap usage: 11,214 allocs, 8,469 frees, 16,487,977 bytes allocated

==28271==

==28271== LEAK SUMMARY:

==28271== definitely lost: 5,950 bytes in 55 blocks

==28271== indirectly lost: 3,562 bytes in 32 blocks

==28271== possibly lost: 0 bytes in 0 blocks

==28271== still reachable: 181,314 bytes in 2,658 blocks

==28271== suppressed: 0 bytes in 0 blocks

I don't understand why there are these leaks. Maybe it's just me not able to read the valgrind output or to use MPI initialization/finalization correctly...

I am using OMPI 1.4.1-3 under ubuntu on a 64 bit architecture, if this can help.

Thanks a lot for your time!

cnicutar cnicutar · Accepted Answer · 2011-12-12T08:57:01

You're not doing anything wrong. Memcheck false positives with valgrind are common, the best you can do is suppress them.

This page of the manual speaks more about these false positives. A quote near the end:

The wrappers should reduce Memcheck's false-error rate on MPI applications. Because the wrapping is done at the MPI interface, there will still potentially be a large number of errors reported in the MPI implementation below the interface. The best you can do is try to suppress them.

MPI memory leak

2 Answers