Fortran 90 and Up: New Features in Previous: Extrinsic Procedures

Sequence and Storage Association

A goal of HPF was to maintain compatibility with Fortran 90. Full support of Fortran sequence and storage association, however, is not compatible with the goal of high performance through distribution of data in HPF. Some forms of associating subprogram dummy arguments with actual values make assumptions about the sequence of values in physical memory which may be incompatible with data distribution. Certain forms of EQUIVALENCE statements are recognized as requiring a modified storage association paradigm. In both cases, HPF provides a directive to assert that full sequence and storage association for affected variables must be maintained. In the absence of such explicit directives, reliance on the properties of association is not allowed. An optimizing compiler may then choose to distribute any variables across processor memories in order to improve performance. To protect program correctness, a given implementation should provide a mechanism to ensure that all such default optimization decisions are consistent across an entire program. Section describes the restrictions and directives related to storage and sequence association.
Thu Dec 8 16:17:11 CST 1994