diff options
Diffstat (limited to 'misc/cgo/gmp/pi.go')
-rw-r--r-- | misc/cgo/gmp/pi.go | 104 |
1 files changed, 104 insertions, 0 deletions
diff --git a/misc/cgo/gmp/pi.go b/misc/cgo/gmp/pi.go new file mode 100644 index 000000000..45f61abbd --- /dev/null +++ b/misc/cgo/gmp/pi.go @@ -0,0 +1,104 @@ +/* +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 "gmp" + "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.Cgocalls(), numer.Len(), accum.Len(), denom.Len()) +} |