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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.