The grid engine system starts the parallel environment by using the exec system call to invoke a startup procedure. The name of the startup executable and the parameters passed to this executable are configurable from within the grid engine system.
An example for such a startup procedure for the PVM environment is contained in the distribution tree of the grid engine system. The startup procedure is made up of a shell script and a C program that is invoked by the shell script. The shell script uses the C program to start up PVM cleanly. All other required operations are handled by the shell script.
The shell script is located under sge-root/pvm/startpvm.sh. The C program file is located under sge-root/pvm/src/start_pvm.c.
The startup procedure could have been a single C program. The use of a shell script enables easier customization of the sample startup procedure.
The example script startpvm.sh requires the following three arguments:
The path of a host file generated by grid engine software, containing the names of the hosts from which PVM is to be started
The host on which the startpvm.sh procedure is invoked
The path of the PVM root directory, usually contained in the PVM_ROOT environment variable
These parameters can be passed to the startup script as described in Configuring Parallel Environments With QMON. The parameters are among the parameters provided to parallel environment startup and stop scripts by the grid engine system during runtime. The required host file, as an example, is generated by the grid engine system. The name of the file can be passed to the startup procedure in the parallel environment configuration by the special parameter name $pe_hostfile. A description of all available parameters is provided in the sge_pe(5) man page.
The host file has the following format:
Each line of the file refers to a queue on which parallel processes are to run.
The first entry of each line specifies the host name of the queue.
The second entry specifies the number of parallel processes to run in this queue.
The third entry denotes the queue.
The fourth entry denotes a processor range to use in case of a multiprocessor machine.
This file format is generated by the grid engine system. The file format is fixed. Parallel environments that need a different file format must translate it within the startup procedure. See the startpvm.sh file. PVM is an example of a parallel environment that needs a different file format.
When the grid engine system starts the parallel environment startup procedure, the startup procedure launches the parallel environment. The startup procedure should exit with a zero exit status. If the exit status of the startup procedure is not zero, grid engine software reports an error and does not start the parallel job.
You should test any startup procedures first from the command line, without using the grid engine system. Doing so avoids all errors that can be hard to trace if the procedure is integrated into the grid engine system framework.