Yukihiro "Matz" Matsumoto b7593cde15 mruby-bigint: optimize multiplication for all-ones numbers ...

Add fast path for multiplying numbers of form 2^n - 1 (all bits set).

Uses algebraic identities:
- (2^n - 1) * (2^m - 1) = 2^(n+m) - 2^n - 2^m + 1
- (2^n - 1) * y = (y << n) - y

These are O(n) operations instead of O(n^1.585) for Karatsuba.
Fuzzing test cases using all-ones patterns now complete in 0.01s
instead of 13+ seconds.

Also raises KARATSUBA_THRESHOLD from 8 to 32 for ~32% speedup
on general large number multiplication.

Co-authored-by: Claude <noreply@anthropic.com>

2026-01-09 12:25:22 +09:00

..

bigint.c

mruby-bigint: optimize multiplication for all-ones numbers

2026-01-09 12:25:22 +09:00

bigint.h

misc: fix spelling

2025-05-14 02:01:02 +10:00