Parallel execution can increase performance.
On OpenVMS, Linux, Windows systems, and in programs compiled without the -hpf option on Tru64 UNIX systems, the HPF directives are parsed and checked for syntactic errors, but have no effect on program execution. HPF directives are preceded by a special prefix that identifies them to the compiler. Specification directives must appear in the specification part of a scoping unit. Executable directives must appear in the execution part of a scoping unit. For details on how to use these directives, see the Compaq Fortran User Manual for Tru64 UNIX and Linux Alpha Systems .