On 3/18/2012 3:54 AM, Michel Talon wrote:
> Akshay Srinivasan wrote:
>> On 03/18/2012 02:20 AM, Richard Fateman wrote:
>>> You mention AD (automatic differentiation). Have you seen this?
>>>
>>> http://www.cs.berkeley.edu/~fateman/papers/overload-AD.pdf
>>>
>>>
>> Yes, well sort of, I remember that I didn't read the paper completely
>> or try the source code though.
>>
>> I think the trouble is, as it is now, I don't think I can rely on
>> Maxima for doing efficient numerical calculations, and there really
>> isn't a very usable lisp alternative for something like NumPy,
>> although Matlisp comes close.
Are you saying that NumPy is efficient? Or that you like its user
interface? Or its scope?
The efficiency of numerical calculations in Lisp is heavily dependent on
the particular
implementation. CMU-CL or SBCL, among the free lisps, should be pretty
good.
> Indeed, from my experience with colnew, i don't think that Common Lisp
> may really be used for extensive numerical computations, contrary to what
> is claimed by lisp evangelists.
With GCL? Also, there is a certain loss inherent in the f2cl, if that
was used. For example,
the result of a fortran call by reference is mimicked by a
multiple-value return, and there may
be other issues too.
> Knowing how well NumPy works, i think
> like you that the solution is to allow convenient translation of the numerical
> intensive work from maxima to Fortran or C, automatic compilation of this code
> and linking in the maxima process.
This has been a long-time traditional way of dealing with the issue.
Actually, C was traditionally
less favored compared to FORTRAN because the optimization of FORTRAN was
more
sophisticated (e.g. loop unrolling, code motion, common subexpression
optimization....).
Either C has got this kind of stuff too, or no one cares. Consider the
possibility that, if you
are not wedded to portability, you can generate assembler (from lisp
directly)!
> Automatic translation can be helped by
> primitive programs like fortran (or my cgrind), but also by more sophisticated
> ones like contrib/gentran.
Yep, original Gentran and related stuff is decades old.
> Dan Stanger has recently contributed work to
> gentran so i think it works now on recent Maxima, at least up to producing
> fortran code. As far as i remember some work is still needed for producing C
> code. If you are interested it should not be difficult to do: by comparing an
> old version of gentran and a recent one you will see what Dan
> has done to make fortran generation work. Basically the point is that gentran
> has been written for old versions of lisp, and needs some adaptation to work
> with sbcl, cmucl, etc. gentran is *very* sophisticated, it can translate whole
> maxima programs to fortran programs (resp C) including the logical flow
> operators, etc. so i think that with some polishing and testing, you have here
> a tool which is as least as sophisticated as anything existing for python.
> Arranging things so that gcc is invoked on the code produced from within lisp
> is probably trivial. Arranging that the object can be linked into maxima is
> perhaps less trivial, this has to do with foreign function interface in lisp,
> which apparently may have variations from lisp to lisp.
> Unfortunately there
> are several Common Lisp variants, with differences in the non normalized parts
> of the language, but fortunately it seems that sbcl emerges as the only widely
> used variant, at least in the free software world, which may help creating
> equivalents of NumPy working with sbcl.
There is some attempt, CFFI, which I have not used myself, to
standardize foreign function interfaces.
My understanding is the GCL doesn't allow this. If SBCL truly runs on
Windows, (for which there
seems to be some issues), that would help. I personally solve these
issues by not
using "several Common Lisp variants" but only one.
>
>
>
>
>
>> Ray and I have been incorporating new stuff into Matlisp though,
>> hopefully that will mature into something that I'd be happy using.
Great! I'm a fan of Matlisp, at least in principle; I haven't used it
myself :)
>>
>> Akshay