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The FORALL statement and construct and PURE procedures have been added to Fortran 95 to allow Fortran 95 programs to execute efficiently in parallel on multi-processor systems. These features allow the majority of programs coded in High Performance Fortran (HPF) to run on a standard conforming Fortran 95 processor with little change. Adding these features to Fortran 95 does not imply that a particular Fortran 95 processor is multi-processor.

The purpose of the FORALL statement and construct is to provide a convenient syntax for simultaneous assignments to large groups of array elements. The multiple assignment functionality it provides is very similar to that provided by the array assignment statement and the WHERE construct in Fortran 90. FORALL differs from these constructs in its syntax, which is intended to be more suggestive of local operations on each element of an array, and in its generality, which allows a larger class of array sections to be specified. In addition, a FORALL may invoke user-defined functions on the elements of an array, simulating Fortran 90 elemental function invocation (albeit with a different syntax).

FORALL is not intended to be a completely general parallel construct; for example, it does not express pipelined computations or multiple-instruction multiple-data (MIMD) computation well. This was an explicit design decision made in order to simplify the construct and promote agreement on the statement's semantics.



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