[libgfortran, configury] BLAS-based implementation of matmul

Brooks Moses bmoses@stanford.edu
Tue Apr 4 04:40:00 GMT 2006

Steve Kargl wrote:
> On Mon, Apr 03, 2006 at 05:37:28PM -0700, Mike Stump wrote:
>>It is possible.  In general, I like the compiler best, when it has  
>>all of its runtime libraries bundled with it and suitable for  
>>commercial development.  For example, STL for C++ is part of the  
>>language standard and C++ is best when bundled with it.  This was  
>>done by bundling the SGI STL with gcc.  Likewise implementation  
>>libraries like libgcc.a, libmudflap.a and libgcov.a and so on.
> Mike, I am completely baffled by the above.  Are you saying that
> the STL provided by GCC is optimized for all architectures supported
> by gcc?  libgfortran will contain a complete runtime library for
> gfortran.  What FX is trying to do is map the generic matmul()
> routine to optimized BLAS routines.  Indeed, FX showed a 425%
> increase in speed in computing the matrix multiplication with his
> example.  There simply isn't a generic BLAS matrix multiplication
> algorithm that is optimal for all of the CPUs supported by GCC.
> The last time I compiled ATLAS on my system, it took something
> like 3 days to complete.

I think Mike was understanding the proposal to be that the matmul() 
routine would be mapped to optimized BLAS routines all the time, and 
thus that libgfortran, by not including the optimized BLAS routines, 
would _not_ be a complete runtime library for gfortran.

FX's more recent post on the subject makes it quite clear that that's 
not the case and that it will still definitely be possible to run 
gfortran without a third-party BLAS library, but Mike was replying to 
the one from a few days ago which didn't make it nearly so clear.

- Brooks

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