// Copyright 2015 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package runtime_test
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import (
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"math"
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"runtime"
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"testing"
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)
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func TestFastLog2(t *testing.T) {
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// Compute the euclidean distance between math.Log2 and the FastLog2
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// implementation over the range of interest for heap sampling.
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const randomBitCount = 26
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var e float64
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inc := 1
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if testing.Short() {
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// Check 1K total values, down from 64M.
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inc = 1 << 16
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}
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for i := 1; i < 1<<randomBitCount; i += inc {
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l, fl := math.Log2(float64(i)), runtime.Fastlog2(float64(i))
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d := l - fl
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e += d * d
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}
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e = math.Sqrt(e)
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if e > 1.0 {
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t.Fatalf("imprecision on fastlog2 implementation, want <=1.0, got %f", e)
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}
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}
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