Re: Interprocedural optimization and code reuse

In article 91-07-007 ssr@stokes.princeton.edu (Steve S. Roy) writes:
> It would be really nice if I could write one general purpose matrix
>multiply routine like (schematicly and in FORTRAN notation):
> [...]
>and use it everywhere.
>
> The tuning involves things like the size of cache and the relative
>size of each of the arrays, the pipeline structure of the processor, etc.
>If the arrays will all fit in cache then one way of coding this is best.
>If one will and the other won't then a second is best. If you know that
>'c(i,j)' starts out in cache then a third is best.


This answer doesn't directly answer your question about code reuse,
but there is a body of literature on "loop blocking" for locality and
cache reuse. There's no need to rewrite the code - simply changing
the "blocking factor" is sufficient based on cache characteristics and
array sizes. This can be done efficiently at runtime. I recommend
reading the paper:


Monica Lam & Michael Wolf, "A Data Locality Optimizing Algorithm",
PLDI'91.


There are a couple of other papers written by Michael Wolf, et al.,
but I can't find where they've been published off hand. I think "The
Cache Performance and Optimizations of Blocked Algorithms" was in this
year's APLOS.


Rob
--

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