HP-MPI Version 2.2 for HP-UX Release Note

HP-MPI V2.2 for HP-UX Release Note
What’s in This Version
14
New Environment Variables
The following section provides brief descriptions of the new environment variables included in
this release.
MPI_RDMA_MSGSIZE=a,b,c
Specifies message protocol length where:
a Short message protocol threshold. If the message length is bigger than this
value, middle or long message protocol is used. The default is 16384 bytes.
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. The
default is 4194304 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 8.
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 concurrently pinned down for
each connection. This is only for one-direction traffic. The default is 3.