mpn_mul is embarrassingly slow
tg at gmplib.org
Tue Apr 24 13:24:09 UTC 2018
paul zimmermann <Paul.Zimmermann at inria.fr> writes:
I would entirely drop all the squaring-related stuff from mpn_mul:
the user/developer should call mpn_sqr instead (see my previous mail).
That's tempting, but a 30% slowdown on some user code would not be nice.
(I believe it is vn and not un that should be compared to MUL_TOOM22_THRESHOLD.)
The comment added before that "if" statement motivates why un is used:
/* If un, and thus vn, are below the toom22 range, drop into mul_basecase.
Test un and not vn here not to thwart the code handling un >> vn below. */
Please encrypt, key id 0xC8601622
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