Parallel Programming Guide for HP-UX Systems

MPI

Running

Chapter 234

MPI_LOCALIP MPI_LOCALIP speciﬁes the host IP address that is assigned throughout a

session. Ordinarily, mpirun determines the IP address of the host it is running on by calling

gethostbyaddr. However, when a host uses a SLIP or PPP protocol, the host’s IP address is

dynamically assigned only when the network connection is established. In this case,

gethostbyaddr may not return the correct IP address.

The MPI_LOCALIP syntax is as follows:

xxx

where

xxx

speciﬁes the host IP address.

MPI_MT_FLAGS MPI_MT_FLAGS controls runtime options when you use the

thread-compliant version of HP MPI. The MPI_MT_FLAGS syntax is a comma separated list as

follows:

[ct,][single,][fun,][serial,][mult]

where

ct Creates a hidden communication thread for each rank in the job. When you

enable this option, be careful not to oversubscribe your system. For example,

if you enable ct for a 16-process application running on a 16-way machine,

the result will be a 32-way job.

single Asserts that only one thread executes.

fun Asserts that a process can be multithreaded, but only the main thread

makes MPI calls (that is, all calls are funneled to the main thread).

serial Asserts that a process can be multithreaded, and multiple threads can make

MPI calls, but calls are serialized (that is, only one call is made at a time).

mult Asserts that multiple threads can call MPI at any time with no restrictions.

Setting MPI_MT_FLAGS=ct has the same effect as setting MPI_FLAGS=s[a][p]#, when the

value of # that is greater than 0. MPI_MT_FLAGS=ct takes priority over the default

MPI_FLAGS=sp0 setting. Refer to “MPI_FLAGS” on page 29.

The single, fun, serial, and mult options are mutually exclusive. For example, if you specify

the serial and mult options in MPI_MT_FLAGS, only the last option speciﬁed is processed

(in this case, the mult option). If no runtime option is speciﬁed, the default is mult.

For more information about using MPI_MT_FLAGS with the

thread-compliant library, refer to “Thread-compliant library” on page 21.

MPI_NOBACKTRACE On PA-RISC systems, a stack trace is printed when the following

signals occur within an application: