7.13 -show hpf Option

Take advantage of the information given by the -show hpf option. This option prints useful information about interprocessor communication generated by the compiler, statements that are recognized as nearest-neighbor, statements that are not handled in parallel, and other information. This is very useful in determining what the compiler is doing with your program.

For example, consider this test program: 

PROGRAM test
INTEGER a(100), b(100), c(100)
!HPF$ DISTRIBUTE (BLOCK) :: a,c
!HPF$ DISTRIBUTE b(CYCLIC)
c= a+b
END PROGRAM test

When this program is compiled with the -show hpf_comm option, the following output is generated: 

% f90 -wsf -show hpf_comm test.f90

f90: Info:
f90: Info: test.f90, line 5:
f90: Info:     Communication needed because
f90: Info:     the target is distributed differently than the source.
f90: Info:         Target: @1(1:100)
f90: Info:         Source: B
f90: Info:     Temp @1(1:100) has distribution (block)

This tells you that since A and C are distributed BLOCK, the compiler re-maps B to BLOCK in order to do the statement in parallel. The "at" sign (@) indicates a compiler-generated temporary array. If you see more communication generated than you expect, it indicates that you need to check your program to verify that the HPF directives you have issued are what you intended.

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