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mirror of https://github.com/golang/go synced 2024-11-25 07:57:56 -07:00
go/misc/cgo/gmp/pi.go
Shenghou Ma 1abd8d8fd0 misc/cgo/gmp: update for Go 1
1. make the program go buildable
2. update os.EINVAL and runtime.Cgocalls()
3. wrap mpz_div_2exp() and mpz_mul_2exp to support both
   pre-5.0 and post-5.0 gmp (we really have no reason to
   restrict ourselves to gmp 5.0+)

R=golang-dev, remyoudompheng, iant
CC=golang-dev
https://golang.org/cl/5847061
2012-03-21 00:51:48 +08:00

107 lines
2.9 KiB
Go

// +build ignore
/*
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
* Neither the name of "The Computer Language Benchmarks Game" nor the
name of "The Computer Language Shootout Benchmarks" nor the names of
its contributors may be used to endorse or promote products derived
from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
*/
/* The Computer Language Benchmarks Game
* http://shootout.alioth.debian.org/
*
* contributed by The Go Authors.
* based on pidigits.c (by Paolo Bonzini & Sean Bartlett,
* modified by Michael Mellor)
*/
package main
import (
big "."
"fmt"
"runtime"
)
var (
tmp1 = big.NewInt(0)
tmp2 = big.NewInt(0)
numer = big.NewInt(1)
accum = big.NewInt(0)
denom = big.NewInt(1)
ten = big.NewInt(10)
)
func extractDigit() int64 {
if big.CmpInt(numer, accum) > 0 {
return -1
}
tmp1.Lsh(numer, 1).Add(tmp1, numer).Add(tmp1, accum)
big.DivModInt(tmp1, tmp2, tmp1, denom)
tmp2.Add(tmp2, numer)
if big.CmpInt(tmp2, denom) >= 0 {
return -1
}
return tmp1.Int64()
}
func nextTerm(k int64) {
y2 := k*2 + 1
accum.Add(accum, tmp1.Lsh(numer, 1))
accum.Mul(accum, tmp1.SetInt64(y2))
numer.Mul(numer, tmp1.SetInt64(k))
denom.Mul(denom, tmp1.SetInt64(y2))
}
func eliminateDigit(d int64) {
accum.Sub(accum, tmp1.Mul(denom, tmp1.SetInt64(d)))
accum.Mul(accum, ten)
numer.Mul(numer, ten)
}
func main() {
i := 0
k := int64(0)
for {
d := int64(-1)
for d < 0 {
k++
nextTerm(k)
d = extractDigit()
}
eliminateDigit(d)
fmt.Printf("%c", d+'0')
if i++; i%50 == 0 {
fmt.Printf("\n")
if i >= 1000 {
break
}
}
}
fmt.Printf("\n%d calls; bit sizes: %d %d %d\n", runtime.NumCgoCall(), numer.Len(), accum.Len(), denom.Len())
}