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-rw-r--r--misc/cgo/gmp/pi.go104
1 files changed, 104 insertions, 0 deletions
diff --git a/misc/cgo/gmp/pi.go b/misc/cgo/gmp/pi.go
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+++ b/misc/cgo/gmp/pi.go
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+/*
+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())
+}