[MPIWG Fortran] Questions about MPI_Comm_spawn

Junchao Zhang jczhang at mcs.anl.gov
Tue Mar 25 09:51:37 CDT 2014


Hello, Fortran experts,

  p.377 of MPI3 defines prototype of MPI_Comm_spawn.

  MPI_Comm_spawn(command, argv, maxprocs, info, root, comm, intercomm,
array_of_errcodes, ierror)
     CHARACTER(LEN=*), INTENT(IN) ::  command, argv(*)
     ...

I can understand that command is a variable-length character. I fetch its
length by len(command). The Fortran compiler needs to pass in data of
command, as well as length of command.
But I can't understand argv(*). I interpret it as an assumed-size array of
variable-length characters. Does that imply each argv(i) could have
different lengths, e.g., len(argv(1)) may be different from len(argv(2))?
I think it is unreasonable, since if that, the compiler has to pass in
length of every element of argv(*).

Thank you
--Junchao Zhang
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