[MPICH] help self-defined datatype
Rob Ross
rross at mcs.anl.gov
Wed Sep 28 10:06:23 CDT 2005
Hi,
At least one problem is that your displacements are wrong. All
displacements are relative to the pointer to the type, not the last
displacement. So you want:
> #ifndef FIVE
> int S=4;
> MPI_Datatype type[4] = { MPI_DOUBLE, MPI_DOUBLE, MPI_DOUBLE, MPI_DOUBLE};
> int blocklen[4] = { 1, 1, 1, 1 };
> MPI_Aint disp[4] = { 0, sizeof(double), 2*sizeof(double), 3*sizeof(double)};
> #else
> int S=5;
> MPI_Datatype type[5] = { MPI_DOUBLE, MPI_DOUBLE, MPI_DOUBLE, MPI_DOUBLE, MPI_DOUBLE};
> int blocklen[5] = { 1, 1, 1, 1, 1 };
> MPI_Aint disp[5] = { 0, sizeof(double), 2*sizeof(double), 3*sizeof(double), 4*sizeof(double)};
> #endif
That explains the "FIVE undefined" behavior, but not what you show for
the defined case.
You should also check that sizeof(Grid) == MPI_Type_extent(GRID), just
to make sure that the compiler isn't doing any weird padding or anything
(very unlikely, but types built on structs are tricky).
Regards,
Rob
---
Rob Ross, Math and Comp. Science Division, Argonne National Laboratory
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