(j3.2006) MPI usage problems in Fortran

[Bill Long]

If a dummy has TARGET, the actual is not required to have TARGET.  See, 
for example, [270:20-22] in f03.

Cheers,
Bill


Craig Rasmussen wrote:
> A problem was described to me at the MPI Forum meeting last week.   
> Using split-phase communication (asynchronous) the user can call send  
> on a buffer, do computation, then call wait before reusing the  
> buffer.  The sequence is:
>
>
>        A = 3
>        call MPI_Isend(A, ...., request, ...)
>        ! do computation not involving A
>        call MPI_Wait(request, ...)
>
> The problem is that the way the interfaces are currently defined, the  
> compiler can't know that MPI_Isend has retained a pointer to A that  
> it doesn't release until after the MPI_Wait call.  So a common hack  
> is to add
>
>        call MPI_Get_address(A, ...)
>
> after the MPI_Wait.  I assume the correct way to fix this is to add  
> the target attribute to the first dummy argument in MPI_Isend.  Is  
> there a better way?  This is especially a problem for codes using the  
> implicit MPI interfaces.
>
> However, when I try the following:
>
>        implicit none
>        interface
>          subroutine send(A)
>            real, target :: A(*)
>          end subroutine send
>        end interface
>
>        real :: buf(10)
>
>        call send(buf)
>
>        end program
>
> I get no error message.  Is this a legal program?  Shouldn't the  
> target attribute be required for the actual argument?  Section 5.3.17  
> doesn't say.
>
> Thanks,
> Craig
>
>
>
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>   

-- 
Bill Long                                   longb at cray.com
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