(j3.2006) Interesting F2003-ism
Fri Feb 23 13:43:17 EST 2007
Bill Long wrote:
> At the beginning, only Fortran
> callees have arguments like these, so initially in the actual real
> world, all the focus will be on C calling Fortran. None of the "lots of
> libraries" you mention are set up to deal with this.
And we don't have an interop TR so how this point makes any sense is
beyond me. We are trying to help them set up to deal with this!
> Most of the rank-independent arguments I see in C libraries
> are typeless buffers in routines used to just move data from one place
> to another. Given that Fortran has intrinsic assignment for arrays,
> libraries like these seem irrelevant to a Fortran programmer.
That is where you are wrong! I am at a SIAM conference now where I heard
at least five Fortran jokes in random contexts in public talks, mostly
by people developing FRAMEWORKS for solving scientific problems. Things
like coupling different PDE solvers together, meshing by a centralized
agent that than calls other specialized solvers, adaptive mesh
refinement libraries, automatic computation and communication
reordering, and all kinds of other stuff. I can try to write examples if
I had the time, but I suggest looking at the program for the SIAM
Conference on Computational Science and Engineering program on line.
There is tons of talks about software infrastructures.
At present, all of those people are mostly concerned about calling
Fortran-77 codes to do some compute-intensive jobs. They are trying to
do Fortran-90 and are running into major headaches...this is what gave
Craig headaches too...People get payed by DOE to do this but it is not
easy. For example, AMR codes allocate memory for the refined meshes
themselves. They use *sophisticaed* data structures---they don't just
copy around buffers (and there are some that do, notably MPI and
variants thereof). PETSc, which is now considered legacy code, uses
array pointers to give Fortran 90 access to internal data-structures.
But it needs the interop TR to do this portably. With the allocatable TR
they may sometimes be able to do better by allowing non-alised access to
the Fortran codes.
I am not even an expert on these C++ infrastructure codes developed
mostly at DOE labs, since I program very specific particle-based codes
and they are focused on PDEs mostly. But I have been to enough talks and
have enouigh colleagues that do to know they are very important. You
don't see them because as I said they avoid anything above Fortran 77
like the plague...
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