> On Apr 21, 2016, at 12:08 PM, Matthew Knepley <[email protected]> wrote:
>
> On Wed, Apr 20, 2016 at 2:09 PM, Barry Smith <[email protected]> wrote:
>
> When running with --batch one must provide the flag
> --known-mpi-shared-library this is annoying since no one will know this
>
> I am trying to understand the purpose of this flag. It is used in MPI.py
> in the code
>
> def checkSharedLibrary(self):
> '''Sets flag indicating if MPI libraries are shared or not and
> determines if MPI libraries CANNOT be used by shared libraries'''
> self.executeTest(self.configureMPIEXEC)
> try:
> self.shared = self.libraries.checkShared('#include
> <mpi.h>\n','MPI_Init','MPI_Initialized','MPI_Finalize',checkLink =
> self.checkPackageLink,libraries = self.lib, defaultArg =
> 'known-mpi-shared-libraries', executor = self.mpiexec)
> except RuntimeError, e:
> if self.argDB['with-shared-libraries']:
> raise RuntimeError('Shared libraries cannot be built using MPI
> provided.\nEither rebuild with --with-shared-libraries=0 or rebuild MPI with
> shared library support')
> self.logPrint('MPI libraries cannot be used with shared libraries')
> self.shared = 0
> return
>
> It looks to me like the code says that if MPI is not a shared library then
> you cannot build PETSc with a shared library.
>
> 1) Is this true? What if MPI was built with PIC but static, won't it still be
> possible to use it with a PETSc shared library? i.e. is this even the right
> test?
>
> PETSc used to have multiple shared libraries, and its still possible. If you
> link MPI statically into multiple shared libraries,
> you duplicate symbols like isInitialized. This messes up tons of things in
> MPI.
Matt,
We generate (or should if we don't) our shared PETSc libraries by
sharedlink petscsys.so -lmpi
sharedlink petscvec.so -lpetscsys
etc.
If it is done this way then will the problem with duplicate symbols be an
issue?
What if we make them with
sharedlink petscsys.so -lmpi
sharedlink petscvec.so -lpetscsys -lmpi
etc.
Maybe it is impossible to do the first case since we cannot remove from the
link libraries "just" the MPI libraries whatever they happen to be?
Barry
>
> 2) Is there any way to get rid of this flag or will there be cases were
> configure goes through with success and accepts using shared libraries but
> then the build fails with unable to make the PETSc shared library?
>
> If we allow --single-library=0, I do not see how we can avoid this.
Could we not require --known-mpi-shared-libraries when --single-library=1
(which is the usual case most users will see?)
>
> Matt
>
> Thanks for any input
>
> Barry
>
>
>
>
>
>
> --
> What most experimenters take for granted before they begin their experiments
> is infinitely more interesting than any results to which their experiments
> lead.
> -- Norbert Wiener
