GCD project status?

Torbjörn Granlund tg at gmplib.org
Fri Sep 27 09:35:59 UTC 2019

We now have almost complete results for the latest hgcd2.c tweaks.

We have 5 div1 variants (as chosen by HGCD2_DIV1_METHOD).  There are
results and brief documentation here:


About half of our test machines prefer '/', i.e., whatever word division
the compiler comes up with.  About one quarter prefers method 3, which
handles n / d < 8 with plain and branch-free code, but '/' for greater
divisors.  About one quarter prefers table-driven inverse-and-multiply,
which is in practice branch-free.

The even-numbered methods are clearly unpopular.

Please encrypt, key id 0xC8601622

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