Parallel Computing Support User Guide
Summary
This page discusses support for generic parallel computing jobs on the EGI infrastructure. We consider using the MPI-START framework as a means for launching multiple jobs on a cluster. The are several clearly apparent application areas:
* Hadoop-On-Demand/myHadoop * Charm++ * Parallel R
This is a work in progress.
JDL requirements
As we are using the MPI-START framework, the format of the JDL is the same as for an MPI job. However, the executable hello_bin may launch any process
JobType = "Normal"; CPUNumber = 4; Executable = "starter.sh"; Arguments = "OPENMPI hello_bin hello"; InputSandbox = {"starter.sh", "hello_bin"}; OutputSandbox = {"std.out", "std.err"}; StdOutput = "std.out"; StdError = "std.err"; Requirements = member("MPI-START", other.GlueHostApplicationSoftwareRunTimeEnvironment) && member("OPENMPI", other.GlueHostApplicationSoftwareRunTimeEnvironment);
The starter.sh is based on the code from http://grid.ifca.es/wiki/Middleware/MpiStart/UserDocumentation
hello_bin
This is a very simple code that shows how we detect and execute specific code on the master process only.
#!/bin/bash if test x"$OMPI_COMM_WORLD_RANK" = x"0" ; then echo "I am the one true master" echo "My hostname is `hostname`" echo "My name is `whoami`" echo "Systype `uname -a`" echo "My directory is $PWD" pwd ls echo Machine_file ${MPI_START_MACHINEFILE} cat ${MPI_START_MACHINEFILE}
Using MPI-START and mpiexec to perform non mpi workloads
Both OpenMPI and MPICH2 define a number of environment variables that are available to every MPI process. In particular, they export variables which relate to the number of process slots allocated to the job and to the MPI Rank of the processes. Using this information one can nominate a "master" or coordinator process in the set of processes. This allows us to accommodate some master/slave use-cases.
MPI Distribution | Rank Variable | Communicator Size variable |
---|---|---|
OpenMPI | OMPI_COMM_WORLD_RANK | OMPI_COMM_WORLD_SIZE |
MPICH2 | MPIRUN_RANK | MPIRUN_NPROCS |
#!/bin/bash if test x"$OMPI_COMM_WORLD_RANK" = x"0" ; then ### Code for coordinating master process else ### Code for slave processes fi