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
diff --git a/src/pkg/math/Makefile b/src/pkg/math/Makefile
index 6650482..3b82a78 100644
--- a/src/pkg/math/Makefile
+++ b/src/pkg/math/Makefile
@@ -54,6 +54,7 @@
fmod.go\
frexp.go\
hypot.go\
+ hypot_port.go\
logb.go\
lgamma.go\
ldexp.go\
diff --git a/src/pkg/math/all_test.go b/src/pkg/math/all_test.go
index 6279499..8cb5756 100644
--- a/src/pkg/math/all_test.go
+++ b/src/pkg/math/all_test.go
@@ -1754,6 +1754,12 @@
}
}
+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)
diff --git a/src/pkg/math/hypot.go b/src/pkg/math/hypot.go
index 3192416..ecd115d 100644
--- a/src/pkg/math/hypot.go
+++ b/src/pkg/math/hypot.go
@@ -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 @@
/*
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 @@
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)
}
diff --git a/src/pkg/math/hypot_port.go b/src/pkg/math/hypot_port.go
new file mode 100644
index 0000000..27f335b
--- /dev/null
+++ b/src/pkg/math/hypot_port.go
@@ -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")
+}
diff --git a/src/pkg/math/hypot_test.go b/src/pkg/math/hypot_test.go
new file mode 100644
index 0000000..85ce1d4
--- /dev/null
+++ b/src/pkg/math/hypot_test.go
@@ -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) }
