6.1.2.3 Specifying parallel execution

The following additional options for the molpro command may be used to specify and control parallel execution.

-n tasks/tasks_per_node:smp_threads

tasks specifies the number of Global Array processes to be set up, and defaults to 1. tasks_per_node sets the number of GA processes to run on each node, where appropriate. The default is the number of shared-memory processors on the current node. smp_threads specifies the maximum number of OpenMP threads that will be opened, and defaults to 1. Any of these three components may be omitted, and appropriate combinations will allow GA-only, OpenMP-only, or mixed parallelism.

-N user1:node1:tasks1:executable1:directory1,user2:node2:tasks2:executable2:directory2$\dots$

node1, node2 etc. specify the host names of the nodes on which to run. On most parallel systems, node1 defaults to the local host name, and there is no default for node2 and higher. On Cray T3E and IBM SP systems, if -N is not specified, nodes are obtained from the system in the standard way. tasks1, tasks2 etc. may be used to control the number of tasks on each node as a more flexible alternative to -n /tasks_per_node. If omitted, they are each set equal to -n /tasks_per_node. user1, user2 etc. give the username under which processes are to be created. executable1, executable2 etc. specify the absolute path of the executable, and directory1, directory2 etc. specify the absolute path of the working directory on each node. Most of these parameters may be omitted in favour of the usually sensible default values.

-M memory

This sets, for each node, the amount of memory to allocate in total, to include both Molpro's internal memory (-m option or memory input command) and that for Global Arrays.