mirror of
https://github.com/golang/go
synced 2024-11-25 05:57:57 -07:00
math: faster hypot
Use hardware sqrt for faster hypot; preserve software-only hypot as hypotGo (like sqrtGo); enable benchmarking of hypotGo. R=rsc CC=golang-dev https://golang.org/cl/229049
This commit is contained in:
parent
ac499ed7a5
commit
067fe2840b
@ -54,6 +54,7 @@ ALLGOFILES=\
|
||||
fmod.go\
|
||||
frexp.go\
|
||||
hypot.go\
|
||||
hypot_port.go\
|
||||
logb.go\
|
||||
lgamma.go\
|
||||
ldexp.go\
|
||||
|
@ -1754,6 +1754,12 @@ func BenchmarkHypot(b *testing.B) {
|
||||
}
|
||||
}
|
||||
|
||||
func BenchmarkHypotGo(b *testing.B) {
|
||||
for i := 0; i < b.N; i++ {
|
||||
HypotGo(3, 4)
|
||||
}
|
||||
}
|
||||
|
||||
func BenchmarkIlogb(b *testing.B) {
|
||||
for i := 0; i < b.N; i++ {
|
||||
Ilogb(.5)
|
||||
|
@ -1,4 +1,4 @@
|
||||
// Copyright 2009-2010 The Go Authors. All rights reserved.
|
||||
// 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.
|
||||
|
||||
@ -6,11 +6,6 @@ package math
|
||||
|
||||
/*
|
||||
Hypot -- sqrt(p*p + q*q), but overflows only if the result does.
|
||||
See:
|
||||
Cleve Moler and Donald Morrison,
|
||||
Replacing Square Roots by Pythagorean Sums
|
||||
IBM Journal of Research and Development,
|
||||
Vol. 27, Number 6, pp. 577-581, Nov. 1983
|
||||
*/
|
||||
|
||||
// Hypot computes Sqrt(p*p + q*q), taking care to avoid
|
||||
@ -35,29 +30,12 @@ func Hypot(p, q float64) float64 {
|
||||
if q < 0 {
|
||||
q = -q
|
||||
}
|
||||
|
||||
if p < q {
|
||||
p, q = q, p
|
||||
}
|
||||
|
||||
if p == 0 {
|
||||
return 0
|
||||
}
|
||||
|
||||
pfac := p
|
||||
q = q / p
|
||||
r := q
|
||||
p = 1
|
||||
for {
|
||||
r = r * r
|
||||
s := r + 4
|
||||
if s == 4 {
|
||||
return p * pfac
|
||||
}
|
||||
r = r / s
|
||||
p = p + 2*r*p
|
||||
q = q * r
|
||||
r = q / p
|
||||
}
|
||||
panic("unreachable")
|
||||
return p * Sqrt(1+q*q)
|
||||
}
|
||||
|
63
src/pkg/math/hypot_port.go
Normal file
63
src/pkg/math/hypot_port.go
Normal file
@ -0,0 +1,63 @@
|
||||
// Copyright 2009-2010 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.
|
||||
See:
|
||||
Cleve Moler and Donald Morrison,
|
||||
Replacing Square Roots by Pythagorean Sums
|
||||
IBM Journal of Research and Development,
|
||||
Vol. 27, Number 6, pp. 577-581, Nov. 1983
|
||||
*/
|
||||
|
||||
// Hypot computes Sqrt(p*p + q*q), taking care to avoid
|
||||
// unnecessary overflow and underflow.
|
||||
//
|
||||
// Special cases are:
|
||||
// Hypot(p, q) = +Inf if p or q is infinite
|
||||
// Hypot(p, q) = NaN if p or q is NaN
|
||||
func hypotGo(p, q float64) float64 {
|
||||
// TODO(rsc): Remove manual inlining of IsNaN, IsInf
|
||||
// when compiler does it for us
|
||||
// special cases
|
||||
switch {
|
||||
case p < -MaxFloat64 || p > MaxFloat64 || q < -MaxFloat64 || q > MaxFloat64: // IsInf(p, 0) || IsInf(q, 0):
|
||||
return Inf(1)
|
||||
case p != p || q != q: // IsNaN(p) || IsNaN(q):
|
||||
return NaN()
|
||||
}
|
||||
if p < 0 {
|
||||
p = -p
|
||||
}
|
||||
if q < 0 {
|
||||
q = -q
|
||||
}
|
||||
|
||||
if p < q {
|
||||
p, q = q, p
|
||||
}
|
||||
|
||||
if p == 0 {
|
||||
return 0
|
||||
}
|
||||
|
||||
pfac := p
|
||||
q = q / p
|
||||
r := q
|
||||
p = 1
|
||||
for {
|
||||
r = r * r
|
||||
s := r + 4
|
||||
if s == 4 {
|
||||
return p * pfac
|
||||
}
|
||||
r = r / s
|
||||
p = p + 2*r*p
|
||||
q = q * r
|
||||
r = q / p
|
||||
}
|
||||
panic("unreachable")
|
||||
}
|
9
src/pkg/math/hypot_test.go
Normal file
9
src/pkg/math/hypot_test.go
Normal file
@ -0,0 +1,9 @@
|
||||
// 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
|
||||
|
||||
// Make hypotGo available for testing.
|
||||
|
||||
func HypotGo(x, y float64) float64 { return hypotGo(x, y) }
|
Loading…
Reference in New Issue
Block a user