Which tests are you referring to?
On Jun 16, 2008, at 11:09 AM, George Bosilca wrote:
On Jun 16, 2008, at 10:58 AM, Jeff Squyres wrote:
I completely agree that we should follow the standard to the
greatest possible extend, but then at least we should have our
test codes following the same guidelines. It doesn't means I
volunteer for anything ...
I'm not sure what you mean by that...?
I simply emphasized that most of the tests we're using expect
MPI_ERROR to be set even after MPI_Wait and MPI_Test. I was amazed
that we use tests that are not standard compliant.
george.
The spec clearly states that the singular MPI_TEST* and MPI_WAIT*
functions should not edit the MPI_ERROR field in the status.
george.
On Jun 9, 2008, at 10:44 AM, George Bosilca wrote:
Rainer,
The snippet from the MPICH2 is irrelevant to the current
discussion.
It only concern set empty status. A quick grep in the MPICH2
source
code (find . -name "*.[ch]" -exec grep -Hn MPI_ERROR {} \;) shows
that they ALWAYS set the MPI_ERROR field in the status if they
detect something wrong.
george.
On Jun 9, 2008, at 4:17 AM, Rainer Keller wrote:
Hi,
that's one of the mysteries of the MPI-1 standard.
Nevertheless, we should be std. conforming. Therefore, I included
the comment
and omitted the setting of .MPI_ERROR.
MPIch2 does not for the same reasons. Therefore I would say the
tests are
wrong.
With best regards,
Rainer
PS: e.g. from mpich2-1.0.7:
include/mpiimpl.h:2112
/* Do not set MPI_ERROR (only set if ERR_IN_STATUS is returned */
#define MPIR_Status_set_empty(status_) \
{ \
if ((status_) != MPI_STATUS_IGNORE) \
{ \
(status_)->MPI_SOURCE = MPI_ANY_SOURCE; \
(status_)->MPI_TAG = MPI_ANY_TAG; \
(status_)->count = 0; \
(status_)->cancelled = FALSE; \
} \
}
On Sonntag, 8. Juni 2008, George Bosilca wrote:
Here is what the MPI standard state:
"In general, message passing calls do not modify the value of
the
error code field of status variables. This field may be
updated only
by the functions in Section 3.7.5 which return multiple
statuses.
The
field is updated if and only if such function returns with an
error
code of MPI ERR IN STATUS.
Rationale. The error field in status is not needed for calls
that
return only one status, such as MPI WAIT, since that would only
duplicate the information returned by the function itself. The
current
design avoids the additional overhead of setting it, in such
cases.
The field is needed for calls that return multiple statuses,
since
each request may have had a different failure. (End of
rationale.)"
First, the sentence start with "In general" which is not a
limiting
statement, it absolutely doesn't state that the field doesn't
have
to
be set. Second, the reason cited in the rationale is completely
fake.
We're talking about one store instruction, while the simple
usage of
the status will generate a cache miss.
On the other side, a simple grep in the ompi-tests shows that
hundreds
of tests use this MPI_ERROR over the return value. If test
writers
(which are supposed to know the standard quite well), do such
things,
I wonder how can we expect that the users will never do it.
george.
On Jun 6, 2008, at 12:04 PM, Brian Barrett wrote:
Since this is not the first or second time we've had the
discussion in
the group, perhaps a comment in the code would be a good
idea :).
Brian
On Jun 6, 2008, at 9:58 AM, Jeff Squyres wrote:
George --
This is not correct. Note the comment that says to see
MPI-1.2
section 3.2.5 page 22 (I think it means MPI-1.1). It says:
"In general, message passing calls do not modify the value
of the
error code field of status variables. This field may be
updated
only
by the functions in Section 3.7.5 which return multiple
statuses."
So we should not be setting status.MPI_ERROR here; you should
check
the return value from MPI_WAIT to get the error code.
On Jun 6, 2008, at 11:53 AM, bosi...@osl.iu.edu wrote:
Author: bosilca
Date: 2008-06-06 11:53:17 EDT (Fri, 06 Jun 2008)
New Revision: 18607
URL: https://svn.open-mpi.org/trac/ompi/changeset/18607
Log:
Update the MPI_ERROR field as well.
Text files modified:
trunk/ompi/request/req_wait.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)
Modified: trunk/ompi/request/req_wait.c
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=
=============================================================
--- trunk/ompi/request/req_wait.c (original)
+++ trunk/ompi/request/req_wait.c 2008-06-06 11:53:17 EDT
(Fri,
06
Jun 2008)
@@ -50,6 +50,7 @@
/* See MPI-1.2, sec 3.2.5, p.22 */
status->MPI_TAG = req->req_status.MPI_TAG;
status->MPI_SOURCE = req->req_status.MPI_SOURCE;
+ status->MPI_ERROR = req->req_status.MPI_ERROR;
status->_count = req->req_status._count;
status->_cancelled = req->req_status._cancelled;
}
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