From: rusrabe@XXXXXXXXXXXXXXXXXXXXXXXXXX
Subject: MPI_GET_PROCESSOR_NAME Fortran and C
To: lusk@XXXXXXXXXXX
Date: Tue, 21 Dec 1999 11:31:59 +0100 (MEZ)
Cc: mpi-core@XXXXXXXXXXX
Sender: owner-mpi-core@XXXXXXXXXXX

I want to remember to the original question from Nils Joensson
who asked about the C and the Fortran interface of 
MPI_GET_PROCESSOR_NAME(name, resultlen).

The MPI standard says in general (not about the specific language 
bindings):

| The 'name' is a character string...
| From this value it must be possible to identify a specific piece of 
| hardware... 
| The argument 'name' must represent storage that is at least 
| MPI_MAX_PROCESSOR_NAME characters long.
| MPI_GET_PROCESSOR_NAME may write up to this many characters into 
| 'name'. 
| The numbers of characters actually written is returned in the output
| argument, resultlen. 
| Advice to users. ... The user should examine the output argument,
|                  'resultlen', to determine the actual length
|                  of the name.

I would expect: 
- 'resultlen' and the 'resultlen' characters in 'name' contain
  the same value in all language bindings.
- The 'resultlen' characters in 'name' are printable and 
  do not contain trailing blanks or null characters.
- Additionally, only in the C and C++ binding, a '\0' is stored
  in name[resultlen].

(This is e.g. the behavior of CRAY's MPI.) 
 
I do not see, that there is any need to modify the standard
in the way, that we allow or require that
MPI_GET_PROCESSOR_NAME must write blanks in 
the last (MPI_MAX_PROCESSOR_NAME-resultlen) characters of name.

The application programmer has no problem with this solution, e.g.
    Fortran: write(*,*) name(1:resultlen),' rank=',myrank
    C:       printf("%s rank=%d", name, myrank) 

Rolf 


Rolf Rabenseifner                          High Performance Computing
Parallel Computing                         Center Stuttgart    (HLRS)
Rechenzentrum Universitaet Stuttgart (RUS) Phone:    ++49 711 6855530
Allmandring 30                             FAX:      ++49 711 6787626
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