1 // Copyright 2015 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 package runtime_test 6 7 import ( 8 "math" 9 "runtime" 10 "testing" 11 ) 12 13 func TestFastLog2(t *testing.T) { 14 // Compute the euclidean distance between math.Log2 and the FastLog2 15 // implementation over the range of interest for heap sampling. 16 const randomBitCount = 26 17 var e float64 18 19 inc := 1 20 if testing.Short() { 21 // Check 1K total values, down from 64M. 22 inc = 1 << 16 23 } 24 for i := 1; i < 1<<randomBitCount; i += inc { 25 l, fl := math.Log2(float64(i)), runtime.Fastlog2(float64(i)) 26 d := l - fl 27 e += d * d 28 } 29 e = math.Sqrt(e) 30 31 if e > 1.0 { 32 t.Fatalf("imprecision on fastlog2 implementation, want <=1.0, got %f", e) 33 } 34 } 35
