Getting started with LAM
转自:http://www.lam-mpi.org/tutorials/one-step/lam.php
LAM is a simple yet powerful environment for running and monitoring MPI applications on clusters. The few essential steps in LAM operations are covered below.
Booting LAM
The user creates a file listing the participating machines in the cluster.
shell$ cat lamhosts # a 2-node LAM node1.cluster.example.com node2.cluster.example.com
Each machine will be given a node identifier (nodeid) starting with 0 for the first listed machine, 1 for the second, etc.
The recon tool verifies that the cluster is bootable:
shell$ recon -v lamhosts recon: -- testing n0 (node1.cluster.example.com) recon: -- testing n1 (node2.cluster.example.com)
The lamboot tool actually starts LAM on the specified cluster.
% lamboot -v lamhosts LAM 7.1.4 - Indiana University Executing hboot on n0 (node1.cluster.example.com - 1 CPU)... Executing hboot on n1 (node2.cluster.example.com - 1 CPU)...
lamboot returns to the UNIX shell prompt. LAM does not force a canned environment or a "LAM shell". The tping command builds user confidence that the cluster and LAM are running.
shell$ tping -c1 N 1 byte from 1 remote node and 1 local node: 0.008 secs 1 message, 1 byte (0.001K), 0.008 secs (0.246K/sec) roundtrip min/avg/max: 0.008/0.008/0.008
Compiling MPI Programs
Refer to MPI: It's Easy to Get Started to see a simple MPI program. mpicc (and mpiCC and mpif77) is a wrapper for the C (C++, and F77) compiler that includes all the necessary command line switches to the underlying compiler to find the LAM include files, the relevant LAM libraries, etc.
shell$ mpicc -o foo foo.c shell$ mpif77 -o foo foo.f
Executing MPI Programs
A MPI application is started by one invocation of the mpirun command. A SPMD application can be started on the mpirun command line.
shell$ mpirun -v -np 2 foo 2445 foo running on n0 (o) 361 foo running on n1
An application with multiple programs must be described in an application schema, a file that lists each program and its target node(s).
shell$ cat appfile # 1 master, 2 slaves n0 master n0-1 slave shell$ mpirun -v appfile 3292 master running on n0 (o) 3296 slave running on n0 (o) 412 slave running on n1
Monitoring MPI Applications
The full MPI synchronization status of all processes and messages can be displayed at any time. This includes the source and destination ranks, the message tag, count and datatype, the communicator, and the function invoked.
shell$ mpitask TASK (G/L) FUNCTION PEER|ROOT TAG COMM COUNT DATATYPE 0/0 master Recv ANY ANY WORLD 1 INT 1 slave <running> 2 slave <running>
Process rank 0 is blocked receiving a message consisting of a single integer from any source rank and any message tag, using the MPI_COMM_WORLD communicator. The other processes are running.
shell$ mpimsg SRC (G/L) DEST (G/L) TAG COMM COUNT DATATYPE MSG 0/0 1/1 7 WORLD 4 INT n0,#0
Later, we see that a message sent by process rank 0 to process rank 1 is buffered and waiting to be received. It was sent with tag 7 using the MPI_COMM_WORLD communicator and contains 4 integers.
Cleaning LAM
All user processes and messages can be removed, without rebooting.
shell$ lamclean -v killing processes, done sweeping messages, done closing files, done sweeping traces, done
It is typical for users to mpirun a program, lamclean when it finishes, and then mpirun another program. It is not necessary to lamboot to run each user MPI program.
Terminating LAM
The lamhalt tool removes all traces of the LAM session on the network. This is only performed when LAM/MPI is no longer needed (i.e., no more mpirun/lamclean commands will be issued).
shell$ lamhalt
In the case of a catastrophic failure (e.g., one or more LAM nodes crash), the lamhalt utility will hang. In this case, the wipe tool is necessary. The same boot schema that was used with lamboot is necessary to list each node where the LAM run-time environment is running:
shell$ wipe -v lamhosts Executing tkill on n0 (node1.cluster.example.com)... Executing tkill on n1 (node2.cluster.example.com)...