[MPICH] MPI datatype question

[Rajeev Thakur]

As far as I can tell, you are right. Send in the bug report :-).

Rajeev
 

> -----Original Message-----
> From: owner-mpich-discuss at mcs.anl.gov 
> [mailto:owner-mpich-discuss at mcs.anl.gov] On Behalf Of Avery Ching
> Sent: Tuesday, January 30, 2007 2:46 PM
> To: mpich-discuss at mcs.anl.gov
> Subject: [MPICH] MPI datatype question
> 
> Hi all,
> 
> I'm working on improving my MPI-IO testing suite and ran into 
> something
> I thought was confusing to me.  Hopefully someone knows the answer.
> 
> Imagine I use some pseudocode such as:
> 
> arr_blk[2]  = {1, 2}
> arr_disp[2] = {1, 3}
> MPI_Type_create_hindexed(2, arr_blk, arr_disp, MPI_BYTE, first_dtype)
> 
> Which should give me:
> 
> first_dtype = 
> _X_XX (ext = 4)
> 01234
> 
> If I did MPI_Type_contiguous(2, &first_dtype, contig_dtype)
> 
> I would get
> _X_XXX_XX (ext = 8)
> 012345678
> 
> Then I do this:
> 
> arr_blk[2]  = {1, 2}
> arr_disp[2] = {1, 10}
> MPI_Type_create_hindexed(2, arr_blk, arr_disp, &first_dtype,
> second_dtype);
> 
> What would second_dtype look like?  My best guess is this, but I'm not
> sure if it's correct....
> 
> second_dtype = 
> __X_XX_____X_XXX_XX (ext = 17)
> 0123456789012345678 
> 
> Note the positions of the spaces. =)
> 
> One more question.
> 
> arr_blk[2]  = {1, 2}
> arr_disp[2] = {1, 3}
> MPI_Type_indexed(2, arr_blk, arr_disp, &first_dtype, third_dtype)
> 
> Again, I'd like to know what is correct.  My best guess is...
> 
> third_dtype = 
> _X_XX________X_XXX_XX (ext = 20)
> 012345678901234567890 
> 
> Again, please note the positions of the spaces. =)
> 
> Thanks for your help.
> 
> Avery
> 
>