MPI_LB and MPI_UB is what you're looking for. Or better, for MPI-2
compliant libraries such as Open MPI and MPICH2, you can use
MPI_Type_create_resized. This will allow you to create the gap at the
beginning and/or the end of a data-type description.
george.
On Jul 10, 2007, at 10:53 AM, jody wrote:
hi
I want to create datatypes of the form
XX000000...
00XX0000...
0000XX00...
etc.
I tried MPI_Type_indexed(1, ais, ait, MPI_SHORT, &dtNewType)
where ais= {2} and ait = {2} but this only gives me a datatype of
the form
00XX, i.e. no holes at the end.
I guess MPI_Type_vector won't work, because there seems to be
no way to create holes at the beginning of the datatype
I need these datatypes to let each process write its data into the
file
in the following way:
XXYYZZXXYYZZXXYYZZ....
(X is data from proc 0, Y is data from proc 1, Z is data from proc 2)
My intended approach was to define datatypes of the form XX0000,
00XX00, 0000XX
for the respective processors, and then call MPI_File_set_view
with displacement 0 and the respective datatypes fo the "filetype"
parameter,
and finally let each processor write its stuff to file
sequentially using MPI_File_write.
However, my plan failed since i am unable to create datatypes with
holes in front and at the end.
What function should i use to create the desired datatypes?
Thank You
Jody
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