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go/src/math/hypot.go
Thanabodee Charoenpiriyakij 1124fa300b math: use Abs rather than if x < 0 { x = -x }
This is the benchmark result base on darwin with amd64 architecture:

name     old time/op  new time/op  delta
Cos      10.2ns ± 2%  10.3ns ± 3%  +1.18%  (p=0.032 n=10+10)
Cosh     25.3ns ± 3%  24.6ns ± 2%  -3.00%  (p=0.000 n=10+10)
Hypot    6.40ns ± 2%  6.19ns ± 3%  -3.36%  (p=0.000 n=10+10)
HypotGo  7.16ns ± 3%  6.54ns ± 2%  -8.66%  (p=0.000 n=10+10)
J0       66.0ns ± 2%  63.7ns ± 1%  -3.42%  (p=0.000 n=9+10)

Fixes #21812

Change-Id: I2b88fbdfc250cd548f8f08b44ce2eb172dcacf43
Reviewed-on: https://go-review.googlesource.com/84437
Reviewed-by: Giovanni Bajo <rasky@develer.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Giovanni Bajo <rasky@develer.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
2018-02-13 20:12:23 +00:00

39 lines
773 B
Go

// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package math
/*
Hypot -- sqrt(p*p + q*q), but overflows only if the result does.
*/
// Hypot returns Sqrt(p*p + q*q), taking care to avoid
// unnecessary overflow and underflow.
//
// Special cases are:
// Hypot(±Inf, q) = +Inf
// Hypot(p, ±Inf) = +Inf
// Hypot(NaN, q) = NaN
// Hypot(p, NaN) = NaN
func Hypot(p, q float64) float64
func hypot(p, q float64) float64 {
// special cases
switch {
case IsInf(p, 0) || IsInf(q, 0):
return Inf(1)
case IsNaN(p) || IsNaN(q):
return NaN()
}
p, q = Abs(p), Abs(q)
if p < q {
p, q = q, p
}
if p == 0 {
return 0
}
q = q / p
return p * Sqrt(1+q*q)
}