Re: Calling Fortran routines on short arrays

Raymond Toy <[email protected]> writes:

> It's not multithreading, per se.  It's because we can't have GC
> suddenly move the vectors before doing the foreign call, otherwise the
> foreign function will be reading and writing to some random place in
> memory.

OK.  But if GC is done by the same thread, my simple mind would think that
switching it off means setting one global variable to NIL.

> A factor of 2 will be very difficult to achieve, since a Lisp function
> call basically loads up a bunch of pointers and calls the function.  We
> need to compute addresses, do the without-gc/unwind-protect stuff, load
> up the registers for a foreign call and then call it.

Yes.  Here I assume (in the direction to what Duane posted) that also the
Lisp compiler works with addresses and has them readily available.

>     Nicolas> and choosing Matlisp data for the blocks would be a possibility.  But the
>     Nicolas> blocks can be small, therefore I cannot make compromises when operating on
>     Nicolas> those blocks.
>
> I assume you've profiled it so that the small blocks really are the
> bottleneck?

I'm still more or less in the design phase.  I have now a compact
row-ordered scheme (which is as fast as the C version) and want to make it
more general without destroying too much performance.  It is a very safe
bet that I cannot bear too much of overhead here.  Could be that I will
have to handle the very small blocks (1x1--3x3) even without any function
call.

Nicolas.