[Numpy-discussion] BLAS and LAPACK ABI questions (mostly OSX related)

[Robert McGibbon]

#4776 is definitely a separate issue. #4007 could be related similar f2c
ABI issues, but I don't think so.  The difference between the gfotran and
g77/f2c ABIs, to my knowledge, is that (1) fortran REAL (single precision
floating point) return values are actually returned as a c double, not a c
float. (2) when return values are complex, the function is actually
implemented with an ABI that looks like a c function with an extra
pass-by-reference argument at the front of the function where the return
value is placed.

Despite the differences in the handling of the return values, I don't think
there is any difference in how float32 parameters are passed *in*, so I'm
not sure that these issues are related to subroutines like SGEMV which is
presumably behind #4007.

-Robert


On Sun, Jun 8, 2014 at 8:33 PM, Matthew Brett <matthew.brett at gmail.com>
wrote:

> Hi,
>
> On Mon, Jun 9, 2014 at 2:31 AM, Robert McGibbon <rmcgibbo at gmail.com>
> wrote:
> > Yeah, that's definitely not the right signature for sdot when linked
> against
> > the Accelerate framework.
> >
> > But what's the purpose of those wrappers in _umath_linalg? The one for
> sdot,
> > for example, doesn't appear to be used internally, and it isn't available
> > from the python side. While scipy has all of those function pointers
> > accessible in scipy.linalg.blas (e.g. scipy.linalg.blas.sdot._cpointer),
> > those function pointers point to the underlying blas function and expose
> the
> > ABI differences between platforms, leading to, for example the utter
> > nightmare of using the scipy blas function pointers from cython in a
> cross
> > platform way: https://gist.github.com/anonymous/6659007.
>
> Is it possible this is related to:
>
> https://github.com/numpy/numpy/issues/4007
>
> or even:
>
> https://github.com/numpy/numpy/issues/4776
>
> ?
>
> Best,
>
> Matthew
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