Parallel Programming Guide for HP-UX Systems

MPI

Debugging

Chapter 2 57

To improve performance, HP MPI supports a process-to-process, one-copy messaging

approach. This means that one process can directly copy a message into the address space

of another process. Because of this process-to-process bcopy (p2p_bcopy) implementation,

a kernel thread is created for each process that has p2p_bcopy enabled. This thread deals

with page and protection faults associated with the one-copy operation.

TotalView multihost example The following example demonstrates how to debug a typical

HP MPI multihost application using TotalView, including requirements for directory

structure and ﬁle locations.

The MPI application is represented by an appﬁle, named my_appﬁle, which contains the

following two lines:

-h local_host -np 2 /path/to/program1

-h remote_host -np 2 /path/to/program2

my_appﬁle resides on the local machine (local_host) in the

/work/mpiapps/total directory.

To debug this application using TotalView (in this example, TotalView is invoked from the

local machine):

1. Place your binary ﬁles in accessible locations.

• /path/to/program1 exists on local_host

• /path/to/program2 exists on remote_host

To run the application under TotalView, the directory layout on your local machine,

with regard to the MPI executable ﬁles, must mirror the directory layout on each

remote machine. Therefore, in this case, your setup must meet the following

additional requirement:

• /path/to/program2 exists on local_host

2. In the /work/mpiapps/total directory on local_host, invoke TotalView by passing the -tv

option to mpirun:

% $MPI_ROOT/bin/mpirun -tv -f my_appfile

Using the diagnostics library

HP MPI provides a diagnostics library (DLIB) for advanced run time error checking and

analysis. DLIB provides the following checks: