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// Copyright 2015 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 runtime_test
import (
"math"
"runtime"
"testing"
)
func TestFastLog2(t *testing.T) {
// Compute the euclidean distance between math.Log2 and the FastLog2
// implementation over the range of interest for heap sampling.
const randomBitCount = 26
var e float64
inc := 1
if testing.Short() {
// Check 1K total values, down from 64M.
inc = 1 << 16
}
for i := 1; i < 1<<randomBitCount; i += inc {
l, fl := math.Log2(float64(i)), runtime.Fastlog2(float64(i))
d := l - fl
e += d * d
}
e = math.Sqrt(e)
if e > 1.0 {
t.Fatalf("imprecision on fastlog2 implementation, want <=1.0, got %f", e)
}
}
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