Jeff: Thanks for your response. It is indeed a Cray system that I am working with. I'll try your suggestion of MPI_THREAD_SERIALIZED to see whether there is a difference and get back to you. I am already aggregating communication. Do you guys have any configure scripts tuned for Cray systems if I needed to install the latest mpich? Thanks! Bobby On Tue, Jul 2, 2013 at 2:41 AM, Jeff Hammond <[email protected]> wrote:

I have done my own studies of this but only in detail on Blue Gene/Q, which supports both fine-grain and fat locking to support MPI_THREAD_MULTIPLE.

I believe that CrayMPI takes a noticeable hit in MPI_THREAD_MULTIPLE because their network hardware is very low latency and the software overhead associated with locking (which is fat in their case AFAIK) is noticeable by comparison. Is that the vendor in question?

Do you have the option to aggregate communication and or otherwise use MPI_THREAD_SERIALIZED instead? If not, then there really isn't an alternative so comparative study will only make you a sad panda. However, if you can use MPI_THREAD_SERIALIZED, perhaps with some overhead, then you can compare the two implementations.

It would be helpful if you could share code and system details.

Best,

Jeff

On Mon, Jul 1, 2013 at 2:05 AM, Bobby Philip <[email protected]> wrote:

...

Hi:

Are there any studies that have been done on the effect of turning on MPI_THREAD_MULTIPLE with the latest versions of MPICH? I have an AMR application where halo or ghost updates require lots of small messages to be sent/rec'd and I am currently seeing a performance hit with a vendor specific implementation based on MPICH2 and am trying to see whether there are any implementations out there that might deliver better performance.

Thanks, Bobby

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