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https://github.com/golang/go
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dcc821faf8
This file is not part of the benchmark shootout, and we wrote it, so use the usual copyright header, not a partial version of the shootout license. Fixes #13575. Change-Id: Ib610e2ad82914b4ef096a2424cfffe3383db2d5b Reviewed-on: https://go-review.googlesource.com/17715 Run-TryBot: Ian Lance Taylor <iant@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Russ Cox <rsc@golang.org>
74 lines
1.3 KiB
Go
74 lines
1.3 KiB
Go
// Copyright 2009 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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// +build ignore
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package main
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import (
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big "."
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"fmt"
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"runtime"
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)
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var (
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tmp1 = big.NewInt(0)
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tmp2 = big.NewInt(0)
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numer = big.NewInt(1)
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accum = big.NewInt(0)
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denom = big.NewInt(1)
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ten = big.NewInt(10)
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)
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func extractDigit() int64 {
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if big.CmpInt(numer, accum) > 0 {
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return -1
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}
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tmp1.Lsh(numer, 1).Add(tmp1, numer).Add(tmp1, accum)
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big.DivModInt(tmp1, tmp2, tmp1, denom)
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tmp2.Add(tmp2, numer)
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if big.CmpInt(tmp2, denom) >= 0 {
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return -1
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}
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return tmp1.Int64()
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}
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func nextTerm(k int64) {
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y2 := k*2 + 1
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accum.Add(accum, tmp1.Lsh(numer, 1))
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accum.Mul(accum, tmp1.SetInt64(y2))
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numer.Mul(numer, tmp1.SetInt64(k))
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denom.Mul(denom, tmp1.SetInt64(y2))
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}
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func eliminateDigit(d int64) {
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accum.Sub(accum, tmp1.Mul(denom, tmp1.SetInt64(d)))
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accum.Mul(accum, ten)
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numer.Mul(numer, ten)
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}
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func main() {
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i := 0
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k := int64(0)
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for {
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d := int64(-1)
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for d < 0 {
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k++
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nextTerm(k)
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d = extractDigit()
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}
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eliminateDigit(d)
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fmt.Printf("%c", d+'0')
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if i++; i%50 == 0 {
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fmt.Printf("\n")
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if i >= 1000 {
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break
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}
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}
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}
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fmt.Printf("\n%d calls; bit sizes: %d %d %d\n", runtime.NumCgoCall(), numer.Len(), accum.Len(), denom.Len())
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}
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