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Next: Extensions Up: Explicit Parallel I/O Previous: Parallel Data Transfer

Restrictions

The following restrictions allow for a simpler, more efficient implementation of parallel I/O. We may either put them in the language, or list them as recommended programming style.

1. Items in the item list of a PREAD or PWRITE statements are restricted to be variables (no io-implied-do). [Compilers may want to relax this rule, by considering an io-implied-do as being an operation that defines a new variable, akin to an array section, with a distribution induced by the distribution of the variables appearing in the implied-do-loop.]
2. All values needed to determine which entities are specified by a parallel I/O item list need be specified before the I/O statement. That is, we prohibit a statement of the form PREAD (...) N, A(1:N).