On Jan 17, 2006, at 3:17 AM, Yves Reymen wrote:
Brian Barrett wrote:
On Jan 16, 2006, at 11:32 AM, Yves Reymen wrote:
Recently openmpi v1.0.1 was installed on our cluster. It contains
all
parameters of ompi_config.h within a #ifndef OMPI_CONFIG_H. I am
wondering how it is possible to give one of these parameters an
other
value after everthing is configured and installed, given the fact
that
no ompi_config.h is present in the installation.
Take for instance the OMPI_WANT_CXX_BINDINGS that decides if you
want to
include de C++ bindings in mpicxx.h or not. If I set it on my
compile
line as -DOMPI_WANT_CXX_BINDINGS=0. It will always be redefined
to the
value in mpi.h, which for our installation is 1.
Is there a way of getting rid of this redefinition?
Your only options are to live with the defaults installed or re-
configure with the values you want. For this one value, you could
probably safely edit the #define for OMPI_WANT_CXX_BINDINGS in mpi.h,
but that would only work in this one scenario, and even then, would
prevent the use of the C++ bindings with that install.
We generally don't allow for overriding those configure options
because in almost all cases, it won't result in what the user
expects. For instance, if the value for WANT_CXX_BINDINGS is set to
0 by configure, and the user tries to set it to 1, the headers and
libraries required for the C++ bindings won't be present. Or if you
tried to change the WANT_EXCEPTIONS value from 0 to 1, code not built
to handle exceptions might suddenly be expected to do so, resulting
in very bad things.
Is there a reason that you want to disable the C++ bindings after
installation? They should be absolutely harmless if you aren't using
them. If that isn't the case, then we need to fix whatever is
causing your problems.
The problem is that I am using libraries written in C but intended
also
for use in C++. The problem occurs with autopack, which is a
message-passing library which transparently packs small messages into
fewer larger ones for more efficient transport by MPI.
http://www-unix.mcs.anl.gov/autopack/
The last release is 1.3 and dates back to May 2000. Now it seems
development has started on version 1.4.
In the main header, autopack.h, mpi.h is included in a Extern C
block if
a C++ compiler is used:
#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */
...
#include mpi.h>
...
#ifdef __cplusplus
}
#endif /* __cplusplus */
The problem can be solved by taking the #include out of the extern C
block, the C bindings will still be available. But that would mean I
have to edit third party software, which I like to avoid if possible.
I would definitely contact the autopack developers about this problem
-- mpi.h is required by the MPI-2 standard to be safe for inclusion
directly by C++ programs, and given the requirement that mpi.h
provide the C++ bindings when compiling C++ code, I'm not sure what
else we can do. In the short term, my only suggestion would be to
remove the extern C in autopack or build Open MPI without C++ bindings.
Brian
--
Brian Barrett
Open MPI developer
http://www.open-mpi.org/
