mirror of
https://github.com/golang/go
synced 2024-11-22 09:24:41 -07:00
5bf420f0c8
I tried adding a Scale method to big.Int and it didn't make any noticeable difference, so I'm removing my TODO. Also got rid of a few obvious allocations that I missed earlier for a modest improvement (~5%). R=golang-dev, gri CC=golang-dev https://golang.org/cl/2711043
136 lines
3.3 KiB
Go
136 lines
3.3 KiB
Go
/*
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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* Neither the name of "The Computer Language Benchmarks Game" nor the
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name of "The Computer Language Shootout Benchmarks" nor the names of
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its contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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*/
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/* The Computer Language Benchmarks Game
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* http://shootout.alioth.debian.org/
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*
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* contributed by The Go Authors.
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* based on pidigits.c (by Paolo Bonzini & Sean Bartlett,
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* modified by Michael Mellor)
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*/
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package main
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import (
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"big"
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"flag"
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"fmt"
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)
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var n = flag.Int("n", 27, "number of digits")
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var silent = flag.Bool("s", false, "don't print result")
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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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tmp3 = big.NewInt(0)
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y2 = big.NewInt(0)
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bigk = 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 extract_digit() int64 {
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if numer.Cmp(accum) > 0 {
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return -1
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}
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// Compute (numer * 3 + accum) / denom
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tmp1.Lsh(numer, 1)
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tmp1.Add(tmp1, numer)
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tmp1.Add(tmp1, accum)
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tmp1.DivMod(tmp1, denom, tmp2)
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// Now, if (numer * 4 + accum) % denom...
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tmp2.Add(tmp2, numer)
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// ... is normalized, then the two divisions have the same result.
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if tmp2.Cmp(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 next_term(k int64) {
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y2.SetInt64(k*2 + 1)
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bigk.SetInt64(k)
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tmp1.Lsh(numer, 1)
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accum.Add(accum, tmp1)
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accum.Mul(accum, y2)
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numer.Mul(numer, bigk)
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denom.Mul(denom, y2)
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}
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func eliminate_digit(d int64) {
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tmp3.SetInt64(d)
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accum.Sub(accum, tmp3.Mul(denom, tmp3))
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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 printf(s string, arg ...interface{}) {
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if !*silent {
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fmt.Printf(s, arg...)
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}
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}
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func main() {
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flag.Parse()
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var m int // 0 <= m < 10
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for i, k := 0, int64(0); ; {
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d := int64(-1)
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for d < 0 {
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k++
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next_term(k)
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d = extract_digit()
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}
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printf("%c", d+'0')
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i++
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m = i % 10
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if m == 0 {
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printf("\t:%d\n", i)
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}
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if i >= *n {
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break
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}
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eliminate_digit(d)
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}
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if m > 0 {
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printf("%s\t:%d\n", " "[m:10], *n)
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}
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}
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