next up previous
Next: The ch_nexus Device Up: MPICH Previous: The ch_p4 device

The ch_shmem and ch_lfshmem devices

The ch_shmem and ch_lfshmem devices allow communication through shared memory on a number of SMP platforms. ch_lfshmem uses so-called lock-free queues to reduce synchronization overhead and is therefore preferred. Both devices run on most SMP platforms including Sun, SGI, HP and Digital platforms.

Usability of applications using these shared memory devices is high, because process management is handled by normal operating system mechanisms. E.g. process startup is trivial, ps shows every process in a parallel job (though still doesn't have the concept of a parallel process), signals are propagated (usually) and I/O is buffered to the same extent as normal language I/O.

However, these devices are restricted to communication within an SMP, aren't thread-safe, and aren't themselves multithreaded. All of these are potentially desirable in SMP clusters.

Jack Dongarra
Sun Nov 9 14:03:51 EST 1997