[Openmcl-devel] back to coding and optimizing

Hamilton Link hamlink at cs.unm.edu
Fri Feb 25 11:00:17 PST 2005

Hey Gary (or alternatively anyone else who wants to chew on this), I 
have some software that's way numerically intensive, and I was thinking 
about writing a C function or several to take consing and tag-bit 
manipulation within a set of operations down to zip, or close.

What this would entail, I suspect, is storing a lot of data as raw 
memory blocks (real-valued multidimensional arrays, actually), passing 
them around and doing memory management with them with lisp or by hand 
and doing some C operations on them behind the scenes. Most of the 
operations are going to be block+block->block or block->block, and only 
very rarely will I need to look at the actual numbers in the blocks 
from lisp.

So... question: how close can I come to just allocating uvectors and 
passing them into C functions? And actually for that matter how close 
to that do big honkin' vectors with the type of their contents declared 
as short float get me? I assume at least that the latter stores stuff 
without tags and takes care of tagging/untagging through svref -- but 
if I got my hands on the raw vector underneath then C would not have 
tags to worry about.

The other question is, what's the best way to make the GCer play nice 
with C? Stack-allocate copies of all my uvectors? I would guess that 
copying these things about would be chunky but it might not be toooo 
bad... the alternative would be to malloc them, and have lisp only deal 
with their macptrs, right? In which case I have to free them by hand, 
which might also not be toooo bad and would I presume be somewhat 

I know conversations along these lines have floated around the list 
before, so I'll go check the archive too.


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