Re: [myrinet] Registered memory in MPICH over GM

Bill,

> I have written a goodly amount of code using GM.  I am now about to use
> MPICH-GM because I want to compare the performance of it with my code
> while uses GM.

We have MPICH-GM available on our web site. Please get the source and
compile for your OS/platform.

> I have the following question.  If you call MPI_Send or MPI_Receive, are
> the respective buffers copied into DMA-able memory with
> gm_register_memory or is it assumed that the buffers are already
> gm_registered?

GM send/receive functions need to operate memory that is DMAable.
It is user's responsibility to prepare the buffer to be DMAable
before calling GM send/receive functions.

The user can either use GM API gm_dma_malloc/gm_dma_calloc to
allocate DMAable memory of certain size and copy data into it, or
using gm_register_memory to lock down user memory which make the
memory DMAable.

In your case, you will need to implement MPI_Send/MPI_Receive using
GM functions.

Karen Wang
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Dr. Karen Honge Wang                    Software Development
(626) 821-8015                          Myricom Inc.
[email protected]                          325 N. Santa Anita Ave.
http://www.myri.com                     Arcadia, CA 91006
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