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Subject: [OMPI devel] MPI_GROUP_EMPTY and MPI_Group_free()
From: Lisandro Dalcin (dalcinl_at_[hidden])
Date: 2007-12-04 10:43:28


Dear all,

As I see some activity on a related ticked, below some comments I
sended to Bill Gropp some days ago about this subject. Bill did not
write me back, I know he is really busy.

Group operations are supposed to return new groups, so the used has to
free the result. Additionally, the standard say that those operations
may return the empty group. Then the issue: if the empty group is
returned, the user should or should not call MPI_Group_free()??. I
could not find any part of the standard about freeing MPI_GROUP_EMPTY.

This issue is very similar to the one in MPI-1 related to error handlers.

I believe the standard should be a bit stricter here, but many
possibilities are:

* MPI_GROUP_EMPTY must be freed it it is the result of a group
operation. This way similar to the management of predefined error
handlers.

* MPI_GROUP_EMPTY cannot be freed, as it is a predefined handle. Users
have to always check if the result of a group operation is
MPI_GROUP_EMPTY to know if they can or cannot free them. This way is
similar to the current management of predefined datatypes.

--
Lisandro Dalcín
---------------
Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
PTLC - Güemes 3450, (3000) Santa Fe, Argentina
Tel/Fax: +54-(0)342-451.1594
-- 
Lisandro Dalcín
---------------
Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
PTLC - Güemes 3450, (3000) Santa Fe, Argentina
Tel/Fax: +54-(0)342-451.1594