Developer Guide and Reference

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GAP Message (Diagnostic ID 30526)

Message

To parallelize the loop at line %d, annotate the routine %s with %s.

Advice

If the loop contains a call to a function, the compiler cannot parallelize the loop without more information about the function being called.
However, if the function being called in the loop is
a const function
or
a concurrency-safe function,
then the call does not inhibit parallelization of the loop.
Example
Consider the following:
#define N 10000 double A[N], B[N]; int bar(int); void foo(){ int i; for (i=0;i<N;i++){ A[i] = B[i] * bar(i); } }
In this case, the compiler does not parallelize the loop because it is not safe to do so without further information about routine
bar
, which is being called.
If you determine it is safe to do so, you can modify the program code as follows:
#define N 10000 double A[N], B[N]; __declspec(const) int bar(int); void foo(){ int i; for (i=0;i<N;i++){ A[i] = B[i] * bar(i); } }
If you determine it is safe to do so, an alternative way you can modify the program code is as follows:
#define N 10000 double A[N], B[N]; __declspec(concurrency_safe(profitable)) int bar(int); void foo(){ int i; for (i=0;i<N;i++){ A[i] = B[i] * bar(i); } }
Verify
Confirm the routine satisfies the semantics of this annotation. A weaker annotation able to achieve a similar effect is
__declspec(concurrency_safe(profitable)
.