[MPICH] Difference in sizes reported by MPI_DOUBLE & double

[Christina Patrick]

Hi Everybody,

I have written an MPI program on "Linux 2.6.17-1.2142_FC4smp #1 SMP",
architecture is i686 to print the size of MPI_DOUBLE and double (C
primitive datatype). Both of them report different sizes. I am a bit
curious about this and would appreciate if any of anybody could shed
some light on this. My program writes some data to a file and then
reads it back. Because of the discrepancy in sizes, I am getting some
problems.

sizeof(double) = 8
sizeof(MPI_DOUBLE) = 4

Thanks and Warm Regards,
Christina.