From fe08ebaebb09cb0c45e3728a96d494f7f9f5c1b3 Mon Sep 17 00:00:00 2001 From: Brian Kessler Date: Thu, 17 Aug 2017 23:44:34 -0700 Subject: [PATCH] math/big: use internal square for Rat updates #13745 A squared rational is always positive and can not be reduced since the numerator and denominator had no previous common factors. The nat multiplication can be performed using the internal sqr method. Change-Id: I558f5b38e379bfd26ff163c9489006d7e5a9cfaa Reviewed-on: https://go-review.googlesource.com/56776 Reviewed-by: Robert Griesemer Run-TryBot: Robert Griesemer TryBot-Result: Gobot Gobot --- src/math/big/rat.go | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/src/math/big/rat.go b/src/math/big/rat.go index 56ce33d882..f0f436e452 100644 --- a/src/math/big/rat.go +++ b/src/math/big/rat.go @@ -490,6 +490,13 @@ func (z *Rat) Sub(x, y *Rat) *Rat { // Mul sets z to the product x*y and returns z. func (z *Rat) Mul(x, y *Rat) *Rat { + if x == y { + // a squared Rat is positive and can't be reduced + z.a.neg = false + z.a.abs = z.a.abs.sqr(x.a.abs) + z.b.abs = z.b.abs.sqr(x.b.abs) + return z + } z.a.Mul(&x.a, &y.a) z.b.abs = mulDenom(z.b.abs, x.b.abs, y.b.abs) return z.norm() -- 2.50.0