Booting LAM

4. BOOTING LAM

4.1 lamboot

Every MPI session must begin with one and only one lamboot command. To initiate a MPI session under LAM, at the unix prompt:

shell$ lamboot -v hostfile

The -v is to enable the verbose flag, so that the you can observe what LAM is doing. Upon a sucessful invocation using the hostfile listed above, you should see something like (depending on your hostfile ):

LAM /MPI 2 C++/ROMIO - Indiana University

Executing hboot on n0 (node1.cluster.example.com)...
Executing hboot on n1 (node2.cluster.example.com)...
Executing hboot on n2 (node3.cluster.example.com)...
Executing hboot on n3 (node4.cluster.example.com)...
Executing hboot on n4 (node5.cluster.example.com)...
topology done  

If you have having problems with lamboot, check the LAM FAQ under the section "Booting LAM" for lots of helpful information.

4.2 tping

A quick and simple way to check the status of the machines in the current MPI session is with the tping N command. tping can be very helpful when you susppect that the MPI program hangs or when you are not observing expected results. The N command line argument is to tell LAM to "ping"" all of the hosts in the hostfile .

Unless you tell tping to execute a specific number of times, it will run until you hit control-c (just like the Unix ping). You can use the -c flag to specify a number pings to execute: tping -c3 N.