MOAB
A Batch Job Scheduler for Clusters

MOAB is a batch job scheduler for clusters. MOAB allows a user to set up a batch file describing how a program is to be executed in parallel. Once the batch file is submitted, it goes into a queue and MOAB waits for a time when the desired number of processors are available. At that time, MOAB allows the job to begin execution. On job completion, MOAB gathers the program output and returns it to the user. Until the job is complete, MOAB allows the user to query its current status.

A user typically logs into a special login node of the cluster, which is intended only for editing, file management, job submission, and other small interactive tasks.

The user wishes to run a parallel program on several processors of the cluster. To do so, the user must create an executable version of the program, write a suitable MOAB batch job script describing the job limits, and listing the commands to be executed, and then submit the script to MOAB for processing.

The job script can be thought of as consisting of two parts:

• Commands to MOAB, which must begin with the string #MOAB, and which describe properties of the job;
• Ordinary operating system commands, which could essentially be typed interactively, which cause the program to execute, but which may also create or delete files, print the date, change directories, and so on.

The user has two separate issues when preparing a first job script:

• understanding the local "dialect" of MOAB, and the local job policies, such as the names of queues, the limits on the number of processors that can be requested, and so on. The exact form of the MOAB commands is usually obscure, but you only have to figure it out once.
• understanding how to set up the appropriate parallel environment for OpenMP or MPI. For OpenMP, this primarily involves finding out the name of the compiler, and the switches required to compile with OpenMP; for MPI, it is often necessary to invoke a locally defined setup script, to know the names of the compiler scripts, and to know the syntax for the command to execute a program under MPI.

Licensing:

The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.

Related Data and Programs:

MPI, C programs which illustrate the use of the MPI application program interface for carrying out parallel computations in a distributed memory environment.

OPENMP, FORTRAN90 programs which illustrate the use of the OpenMP application program interface for carrying out parallel computations in a shared memory environment.

Source Code:

ENVIRON is a batch job script that simply queries the values of certain environment variables, in particular PBS_O_WORKDIR, which can be useful when trying to set up a program to run under the batch system.

• environ.sh, a MOAB job script.
• environ_output.txt, the output file.

HELLO is a batch job script that works with MOAB to compile and run a program. The script also "cleans up" after itself, that is, it discards the executable program once the job is complete.

• hello.sh, a MOAB job script.
• hello_output.txt, the output file.

HELLO_OPENMP illustrates the compilation and execution of a program that includes OpenMP directives.

• hello_openmp.sh, a MOAB job script.
• hello_openmp_output.txt, the output file.

HELLO_MPI illustrates the compilation and execution of a program that includes MPI directives.

• hello_mpi.sh, a MOAB job script.
• hello_mpi_output.txt, the output file.

You can go up one level to the EXAMPLES source code page.