[Sbcl-devel] Optimise integer division by a constant

[<lut...@fr...>]

Hi folks,

I have done some work on implementing an algorithm found in "Division
by Invariant Integers using Multiplication", 1994 by Torbjörn Granlund
and Peter L. Montgomery, to optimise SBCL's TRUNCATE and friends.

It works nicely: cl-bench's SEARCH-SEQUENCE -- which, as the name
suggests, tests mostly the speed of (MOD <(INTEGER 0 999999)> 1000) --
runs three times as fast on my machine with these changes, and an
integer implementation of a CMRG (L'Ecuyer's "Combined Multiple
Recursive Random Number Generator" that consists of several multi-
plications and modulo reductions) that runs at one seventh the speed
of a C implementation in current SBCL catches up to run at half the
speed of C.

I would like to send a patch for review, hoping I have piqued interest,
and just wanted to ask: Should I send it to the mailing list or open
a launchpad item?

Thanks so far,

Lutz