Scientific computing with D

[Bill Baxter]

On Sun, Feb 1, 2009 at 3:06 AM, Lars Kyllingstad
<public at kyllingen.nospamnet> wrote:
> Bill Baxter wrote:
>>
>> On Fri, Jan 30, 2009 at 10:23 PM, Lars Kyllingstad
>> <public at kyllingen.nospamnet> wrote:
>>>
>>> I think D is, or at least could be, the scientific programming language
>>> of
>>> the future.
>>
>> Agreed!  Numerics is one place where D fits nicely.
>>
>>> [...]
>>> The one thing I miss the most, however, and which I think is necessary
>>> for D
>>> to "take off" as a scientific language, is a native D scientific library.
>>
>>> I think it would be really nice if many or all of the above mentioned
>>> things
>>> could be collected in a single library, together with all kinds of other
>>> stuff. Something like the GSL, only written in D.
>>
>> ...and not GPL, preferably.  :-)
>>
>> The goal sounds great.  I'm certainly willing to help out.
>>
>> To me it seems one of the first things you need to get nailed down is
>> how to represent multidimensional data.  Both dense, strided, and --
>> for 2D -- common sparse and BLAS formats.   Probably this can be done
>> at the concept (compile-time interface) level without having to go
>> into implementation details.  But it might also be nice to have some
>> concrete implementation nailed down too, so not everything is built as
>> a giant house of template cards.  Once you have that, then any package
>> that can work with that concept or array format will be able to share
>> data pretty easily.
>
> Agreed. Unfortunately, linear algebra is not my area of expertise. As I
> said, I have written some basic linear algebra code -- very simplistic
> vector/matrix classes, LU decomposition, etc. -- but just because they're
> needed for my numerical calculus modules. I haven't put any work into
> tweaking the performance of this code.
>
> For my use, and I expect for lots of other areas in numerics, very simple
> vector/matrix interfaces suffice. All I need is opIndex, opAdd, opSub and
> opMul. And then you linear algebra people can take care of the details. ;)
> But that's the nice thing about D -- by using templates and interfaces, I
> think it is possible to create a library that's user-friendly, but which has
> super-speedy functions and classes that are tailored for very specific use
> cases.
>
>> But it's not so easy.  Even now I use 3 different libraries at
>> different times for different things.
>> * I have MatrixT/VectorT,  fixed-size dense matrix and vector, whose
>> 2D and 3D versions have some special operations like "cross product"
>> * I have Dflat, which provides dynamically-sized Matrix types that
>> match what BLAS accepts.  And also a few dynamically-sized sparse
>> formats that work with various sparse libs.
>> * I have MultiArray which is a generic container for N-dimensional
>> strided data, with dynamic number of dimensions and size.
>>
>> On the last one ... I consider that one a bit of a failed experiment.
>> Dynamic number of dimensions causes too many headaches and is not
>> really useful very often.  I think Fawzi is brewing a fix-dim N-d
>> array of his own, or was at one point.
>>
>> But anyway uniting all these things under a single library or even a
>> single concept would be significant work.
>
> ...and, I think, would draw even more people to D.

...and it sounds like Andrei's got plans for creating basically that,
a matrix lib that unites all those different needs.  Or at least BLAS,
sparse types and multidimensional arrays.  Not sure if he has any plan
for fixed-size arrays in that mix, too.  (float2,float2x2, etc)

--bb