mirror of
https://github.com/golang/go
synced 2024-11-24 22:00:09 -07:00
b9caa4ac56
- renamed Len -> BitLen, simplified implementation - renamed old Div, Mod, DivMod -> Que, Rem, QuoRem - implemented Div, Mod, DivMod (Euclidian definition, more useful in a mathematical context) - fixed a bug in Exp (-0 was possible) - added extra tests to check normalized results everywhere - uniformly set Int.neg flag at the end of computations - minor cosmetic cleanups - ran all tests R=rsc CC=golang-dev https://golang.org/cl/1091041
136 lines
3.3 KiB
Go
136 lines
3.3 KiB
Go
/*
|
|
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"
|
|
"flag"
|
|
"fmt"
|
|
)
|
|
|
|
var n = flag.Int("n", 27, "number of digits")
|
|
var silent = flag.Bool("s", false, "don't print result")
|
|
|
|
var (
|
|
tmp1 = big.NewInt(0)
|
|
tmp2 = big.NewInt(0)
|
|
y2 = big.NewInt(0)
|
|
bigk = big.NewInt(0)
|
|
numer = big.NewInt(1)
|
|
accum = big.NewInt(0)
|
|
denom = big.NewInt(1)
|
|
ten = big.NewInt(10)
|
|
)
|
|
|
|
func extract_digit() int64 {
|
|
if numer.Cmp(accum) > 0 {
|
|
return -1
|
|
}
|
|
|
|
// Compute (numer * 3 + accum) / denom
|
|
tmp1.Lsh(numer, 1)
|
|
tmp1.Add(tmp1, numer)
|
|
tmp1.Add(tmp1, accum)
|
|
tmp1.DivMod(tmp1, denom, tmp2)
|
|
|
|
// Now, if (numer * 4 + accum) % denom...
|
|
tmp2.Add(tmp2, numer)
|
|
|
|
// ... is normalized, then the two divisions have the same result.
|
|
if tmp2.Cmp(denom) >= 0 {
|
|
return -1
|
|
}
|
|
|
|
return tmp1.Int64()
|
|
}
|
|
|
|
func next_term(k int64) {
|
|
// TODO(eds) If big.Int ever gets a Scale method, y2 and bigk could be int64
|
|
y2.SetInt64(k*2 + 1)
|
|
bigk.SetInt64(k)
|
|
|
|
tmp1.Lsh(numer, 1)
|
|
accum.Add(accum, tmp1)
|
|
accum.Mul(accum, y2)
|
|
numer.Mul(numer, bigk)
|
|
denom.Mul(denom, y2)
|
|
}
|
|
|
|
func eliminate_digit(d int64) {
|
|
tmp := big.NewInt(0).Set(denom)
|
|
accum.Sub(accum, tmp.Mul(tmp, big.NewInt(d)))
|
|
accum.Mul(accum, ten)
|
|
numer.Mul(numer, ten)
|
|
}
|
|
|
|
func printf(s string, arg ...interface{}) {
|
|
if !*silent {
|
|
fmt.Printf(s, arg)
|
|
}
|
|
}
|
|
|
|
func main() {
|
|
flag.Parse()
|
|
|
|
var m int // 0 <= m < 10
|
|
for i, k := 0, int64(0); ; {
|
|
d := int64(-1)
|
|
for d < 0 {
|
|
k++
|
|
next_term(k)
|
|
d = extract_digit()
|
|
}
|
|
|
|
printf("%c", d+'0')
|
|
|
|
i++
|
|
m = i % 10
|
|
if m == 0 {
|
|
printf("\t:%d\n", i)
|
|
}
|
|
if i >= *n {
|
|
break
|
|
}
|
|
eliminate_digit(d)
|
|
}
|
|
|
|
if m > 0 {
|
|
printf("%s\t:%d\n", " "[m:10], *n)
|
|
}
|
|
}
|