I'm making a matriz multiplication program in OpenMPI, and I got this error message:
[Mecha Liberta:12337] *** Process received signal ***
[Mecha Liberta:12337] Signal: Segmentation fault (11)
[Mecha Liberta:12337] Signal code: Address not mapped (1)
[Mecha Liberta:12337] Failing at address: 0xbfe4f000
--------------------------------------------------------------------------
mpirun noticed that process rank 1 with PID 12337 on node Mecha Liberta exited on signal 11 (Segmentation fault).
--------------------------------------------------------------------------
That's how I define the matrices:
int **a, **b, **r;
a = (int **)calloc(l,sizeof(int));
b = (int **)calloc(l,sizeof(int));
r = (int **)calloc(l,sizeof(int));
for (i = 0; i < l; i++)
a[i] = (int *)calloc(c,sizeof(int));
for (i = 0; i < l; i++)
b[i] = (int *)calloc(c,sizeof(int));
for (i = 0; i < l; i++)
r[i] = (int *)calloc(c,sizeof(int));
And here's my Send/Recv (i'm pretty sure my problem should be here):
MPI_Send(&sent, 1, MPI_INT, dest, tag, MPI_COMM_WORLD);
MPI_Send(&lines, 1, MPI_INT, dest, tag, MPI_COMM_WORLD);
MPI_Send(&(a[sent][0]), lines*NCA, MPI_INT, dest, tag, MPI_COMM_WORLD);
MPI_Send(&b, NCA*NCB, MPI_INT, dest, tag, MPI_COMM_WORLD);
and:
MPI_Recv(&sent, 1, MPI_INT, 0, tag, MPI_COMM_WORLD, &status);
MPI_Recv(&lines, 1, MPI_INT, 0, tag, MPI_COMM_WORLD, &status);
MPI_Recv(&a, lines*NCA, MPI_INT, 0, tag, MPI_COMM_WORLD, &status);
MPI_Recv(&b, NCA*NCB, MPI_INT, 0, tag, MPI_COMM_WORLD, &status);
Can anyone see where is the problem?
This is a common problem with C and multidimensional arrays and MPI.
In this line, say:
you're telling MPI to send NCAxNCB integers starting at b to
dest,MPI_COMM_WORLD
with tagtag
. But, b isn't a pointer to NCAxNCB integers; it's a pointer to NCA pointers to NCB integers.So what you want to do is to ensure your arrays are contiguous (probably better for performance anyway), using something like this:
and then
should work more as expected.