1 files changed, 115 insertions, 0 deletions
diff --git a/src/math/huge_test.go b/src/math/huge_test.go
new file mode 100644
index 0000000..bc28c6f
--- /dev/null
+++ b/src/math/huge_test.go
@@ -0,0 +1,115 @@
+// Copyright 2018 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.
+
+// Disabled for s390x because it uses assembly routines that are not
+// accurate for huge arguments.
+
+//go:build !s390x
+
+package math_test
+
+import (
+	. "math"
+	"testing"
+)
+
+// Inputs to test trig_reduce
+var trigHuge = []float64{
+	1 << 28,
+	1 << 29,
+	1 << 30,
+	1 << 35,
+	1 << 120,
+	1 << 240,
+	1 << 480,
+	1234567891234567 << 180,
+	1234567891234567 << 300,
+	MaxFloat64,
+}
+
+// Results for trigHuge[i] calculated with https://github.com/robpike/ivy
+// using 4096 bits of working precision.   Values requiring less than
+// 102 decimal digits (1 << 120, 1 << 240, 1 << 480, 1234567891234567 << 180)
+// were confirmed via https://keisan.casio.com/
+var cosHuge = []float64{
+	-0.16556897949057876,
+	-0.94517382606089662,
+	0.78670712294118812,
+	-0.76466301249635305,
+	-0.92587902285483787,
+	0.93601042593353793,
+	-0.28282777640193788,
+	-0.14616431394103619,
+	-0.79456058210671406,
+	-0.99998768942655994,
+}
+
+var sinHuge = []float64{
+	-0.98619821183697566,
+	0.32656766301856334,
+	-0.61732641504604217,
+	-0.64443035102329113,
+	0.37782010936075202,
+	-0.35197227524865778,
+	0.95917070894368716,
+	0.98926032637023618,
+	-0.60718488235646949,
+	0.00496195478918406,
+}
+
+var tanHuge = []float64{
+	5.95641897939639421,
+	-0.34551069233430392,
+	-0.78469661331920043,
+	0.84276385870875983,
+	-0.40806638884180424,
+	-0.37603456702698076,
+	-3.39135965054779932,
+	-6.76813854009065030,
+	0.76417695016604922,
+	-0.00496201587444489,
+}
+
+// Check that trig values of huge angles return accurate results.
+// This confirms that argument reduction works for very large values
+// up to MaxFloat64.
+func TestHugeCos(t *testing.T) {
+	for i := 0; i < len(trigHuge); i++ {
+		f1 := cosHuge[i]
+		f2 := Cos(trigHuge[i])
+		if !close(f1, f2) {
+			t.Errorf("Cos(%g) = %g, want %g", trigHuge[i], f2, f1)
+		}
+	}
+}
+
+func TestHugeSin(t *testing.T) {
+	for i := 0; i < len(trigHuge); i++ {
+		f1 := sinHuge[i]
+		f2 := Sin(trigHuge[i])
+		if !close(f1, f2) {
+			t.Errorf("Sin(%g) = %g, want %g", trigHuge[i], f2, f1)
+		}
+	}
+}
+
+func TestHugeSinCos(t *testing.T) {
+	for i := 0; i < len(trigHuge); i++ {
+		f1, g1 := sinHuge[i], cosHuge[i]
+		f2, g2 := Sincos(trigHuge[i])
+		if !close(f1, f2) || !close(g1, g2) {
+			t.Errorf("Sincos(%g) = %g, %g, want %g, %g", trigHuge[i], f2, g2, f1, g1)
+		}
+	}
+}
+
+func TestHugeTan(t *testing.T) {
+	for i := 0; i < len(trigHuge); i++ {
+		f1 := tanHuge[i]
+		f2 := Tan(trigHuge[i])
+		if !close(f1, f2) {
+			t.Errorf("Tan(%g) = %g, want %g", trigHuge[i], f2, f1)
+		}
+	}
+}