Re: BLAS (was Matlisp tests)

On 03/12/2012 12:18 AM, Raymond Toy wrote:
> On 3/11/12 11:11 AM, Akshay Srinivasan wrote:
>> On 03/11/2012 12:37 PM, Raymond Toy wrote:
>>> On 3/10/12 7:03 PM, Akshay Srinivasan wrote:
>>>> On 03/10/2012 11:16 PM, Raymond Toy wrote:
>>>>> On 3/10/12 8:40 AM, Akshay Srinivasan wrote:
>>>>> 
>>>>>>> It would be nice to be able to detect either mode and
>>>>>>> have the ffi do the right thing, but I think many lisps
>>>>>>> do not support structure returns the way gcc is doing
>>>>>>> it now.
>>>>>> It returns a struct ? I never could get hold of the 
>>>>>> documentation for that.
>>>>> That's my understanding.  And when I look at the
>>>>> disassembly for a simple Fortran function, it returns the
>>>>> real and imaginary parts in xmm0 and xmm1 (at least on
>>>>> OSX).
>>>> Hmm. Too clumsy and non-portable to support all that, no ?
>>> It would be good if cffi supported that, but I suspect not.
>>>>>>> We also have an alternative: Add simple C wrappers
>>>>>>> that use the f2c-mode return and call the Fortran
>>>>>>> routine directly.
>>>>>> CBLAS :) (not the netlib version).
>> After some more thinking, I vote for adding wrapper subroutine
>> around zdotu/zdotc in F77. It'll be far too much boring work to
>> migrate to CBLAS, given that I seem to be able to handle ordering
>> quite well within lisp itself. There aren't any other complex
>> returning functions in BLAS, are there ?
> Let me do a grep....Nope.  Looks like those are the only two.
> 
> Not quite sure what you're going to do here.  You want to write two
> C wrapper functions that call zdotu/zdotc correctly, and have the
> wrapper use the f2c convention?
> 
> Since we already detect if we need -ff2c, what is the utility for
> this when matlisp builds its own libraries?  Of course, for atlas,
> I can see that we would want this if we've determined that atlas is
> not compatible.  That would be a nice enhancement.
>> 
>> We probably don't need any other f2c features, since most
>> functions I know only take character arguments instead of string
>> ones.
> Fortunately, matlisp is in control of that because I think it is
> valid fortran to pass in, say, 'Transpose', instead of 'T'.

I have to flip back on my words. I now think CBLAS is the only way
forward. I was writing a wrapper for dgemv (y <- alpha * A . x + beta
y) today and really couldn't figure out a way to support row-ordered
matrices; to do this I will have to use dgemm at best to doing it
completely in lisp at worst. This is bad because, I can't use gemv to
support sliced matrices in gemm!

I do think it is worth the trouble now, given that I will be able
support a lot of matrix-slicey things with access to the order switch
which is provided by CBLAS functions.

What do you think ?

Akshay

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