From: Oleg Trott <oleg_trott@columbia.edu>
To: Markus Mottl <markus@oefai.at>
Cc: OCaml <caml-list@inria.fr>
Subject: Re: [Caml-list] Matrix libraries
Date: Sun, 14 Dec 2003 18:10:58 -0500 [thread overview]
Message-ID: <200312141810.58462.oleg_trott@columbia.edu> (raw)
In-Reply-To: <20031214150152.GB4945@fichte.ai.univie.ac.at>
On Sunday 14 December 2003 10:01 am, Markus Mottl wrote:
> In any case, LACAML is supposed to stay a low-level interface to
> BLAS/LAPACK.
The $1e6 quesion: do you want the library to be safe from user abuse, i.e.
no function input should result in corrupted memory ?
> Others are working on higher-level ones, e.g.:
>
> http://www.math.ucsb.edu/~lyons/camlFloat/index.html
Thanks for the link! CamlFloat isn't even in Google yet. It must be new. Are
there others?
> I'd also like to see something like that, but I am skeptical that this
> is realistically possible. Writing the C-code for the interface is very
> little work. It's the OCaml-code around it that costs time to write,
> especially error handling.
Some of this error-handling like checking that input matrices/vectors have
compatible sizes seems tedious (and error-prone), and I think it can be
auto-generated from parsing *.f files (including comments) But, yes, maybe
it's too hard and not worth the effort.
> > 3.) Regarding "WORK" arguments. Why not have a shared workspace:
>
> Yes, that's exactly the problem: what about SMP-machines and threading
> then?
Each thread oviously needs its own workspace. I think this can be done using
(int * vec ref) list ref (* int = id (self ()) *)
association list (or hash table). Now, "get", "resize", etc. could check if
the thread has its workspace and return it, allocating if necessary.
I think there is a problem with this approach though: each thread's workspace
needs to be removed once the thread terminates. OCaml has at_exit but no
at_thread_exit that I can find (Maybe it can be defined using
Sys.set_signal's ?)
> I had indeed thought about this, but that would have made it more
> inconvenient to people who want to keep accessing "a" directly using
> the Bigarray-module and the .{}-notation.
I think the inconvenience is minimal:
a.{...} vs a.mat_data.{...}
(and it's just typing)
But it saves you from the very error-prone and boring task of having to
remember which variables designate which dimensions ("Is it m x n or n x k,
did I transpose that?"), etc.
OTOH submatrices/slices probably aren't the most frequently used features,
so I haven't made up my mind as to which is better.
> > 5) I think a function that lets one view matrices as vectors vec_of_mat
> > is needed. They are all just ordered sets of numbers after all.
>
> This would collide with 4), wouldn't it? Vector arguments in LAPACK
> don't have anything like a "leading dimension" so this wouldn't help you
> unless you allow copying data.
Just a runtime error if LD does not equal the number of rows would be good.
(If your matrix type includes info about both the number of rows and LD)
--
Oleg Trott <oleg_trott@columbia.edu>
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next prev parent reply other threads:[~2003-12-14 23:11 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-12-13 13:51 romildo
2003-12-13 16:36 ` Markus Mottl
2003-12-13 21:38 ` Oleg Trott
2003-12-14 15:01 ` Markus Mottl
2003-12-14 23:10 ` Oleg Trott [this message]
2003-12-15 10:01 ` Markus Mottl
2003-12-15 17:05 ` [Caml-list] CamlFloat Shivkumar Chandrasekaran
2003-12-15 17:14 ` [Caml-list] Matrix libraries Shivkumar Chandrasekaran
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