HP-MPI Version 2.2.5 for Linux Release Note

HP-MPI V2.2.5 for Linux Release Note

What’s in This Version

b Middle message protocol threshold. If the message length is less than or equal to b,

consecutive short messages are used to send the whole message. By default, we set b

to 16384 bytes, the same as a, to effectively turn off middle message protocol.

c Long message fragment size. If the message is greater than b, the message is

fragmented into pieces up to c in length (or actual length if less than c) and the

corresponding piece of the user’s buffer is pinned directly. For VAPI, IBV, and

uDAPL, the default is 4194304 bytes. For Myrinet, the default is 1048576 bytes.

MPI_RDMA_NENVELOPE=N Specifies the number of short message envelope pairs for each connection if

RDMA protocol is used, where N is the number of envelope pairs. The default is between 8 and 128

depending on the number of ranks.

MPI_RDMA_NSRQRECV=K Specifies the number of receiving buffers used when the shared receiving queue

is used, where K is the number of receiving buffers. If N is the number of offhost connections from a

rank, then the default value can be calculated as:

((N x 8) <= 2048) ? (N x 8) : 2048

In the above example, the number of receiving buffers are calculated as 8 times the number of offhost

connections. If this number is greater than 2048, then 2048 is used as the maximum number.

MPI_RDMA_NFRAGMENT=N Specifies the number of long message fragments that can be pinned down for

each process, either sending or receiving. The max number of fragments that can be pinned down for a

process is 2*N. The default value of N is 128.

MPI_RDMA_NONESIDED=N Specifies the number of one-sided operations that can be posted concurrently

for each rank, no matter the destination. The default is 8.

Rank Identification Environment Variables HP-MPI sets several environment

variables to let the user access information about the MPI rank layout prior to calling

MPI_Init. These variables differ from the others in this section in that the user doesn’t set

these to provide instructions to HP-MPI; HP-MPI sets them to give information to the user’s

application.

HPMPI=1 This variable is set so that an application can conveniently tell if it is running under HP-MPI.

MPI_NRANKS This is set to the number of ranks in the MPI job.

MPI_RANKID This is set to the rank number of the current process.

MPI_LOCALNRANKS This is set to the number of ranks on the local host.

MPI_LOCALRANKID This is set to the rank number of the current process relative to the local host (0..

MPI_LOCALNRANKS-1).