Added shootout benchmark

benches/shootout-pidigits.rs

@@ -0,0 +1,139 @@
+// The Computer Language Benchmarks Game
+// http://benchmarksgame.alioth.debian.org/
+//
+// contributed by the Rust Project Developers
+
+// Copyright (c) 2013-2014 The Rust Project Developers
+//
+// All rights reserved.
+//
+// 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.
+
+extern crate num;
+extern crate test;
+
+use std::from_str::FromStr;
+use std::num::One;
+use std::num::Zero;
+use std::num::FromPrimitive;
+
+use test::Bencher;
+
+use num::Integer;
+use num::bigint::BigInt;
+
+struct Context {
+    numer: BigInt,
+    accum: BigInt,
+    denom: BigInt,
+}
+
+impl Context {
+    fn new() -> Context {
+        Context {
+            numer: One::one(),
+            accum: Zero::zero(),
+            denom: One::one(),
+        }
+    }
+
+    fn from_int(i: int) -> BigInt {
+        FromPrimitive::from_int(i).unwrap()
+    }
+
+    fn extract_digit(&self) -> int {
+        if self.numer > self.accum {return -1;}
+        let (q, r) =
+            (self.numer * Context::from_int(3) + self.accum)
+            .div_rem(&self.denom);
+        if r + self.numer >= self.denom {return -1;}
+        q.to_int().unwrap()
+    }
+
+    fn next_term(&mut self, k: int) {
+        let y2 = Context::from_int(k * 2 + 1);
+        self.accum = (self.accum + (self.numer << 1)) * y2;
+        self.numer = self.numer * Context::from_int(k);
+        self.denom = self.denom * y2;
+    }
+
+    fn eliminate_digit(&mut self, d: int) {
+        let d = Context::from_int(d);
+        let ten = Context::from_int(10);
+        self.accum = (self.accum - self.denom * d) * ten;
+        self.numer = self.numer * ten;
+    }
+}
+
+fn pidigits(n: int) {
+    let mut k = 0;
+    let mut context = Context::new();
+
+    for i in range(1, n + 1) {
+        let mut d;
+        loop {
+            k += 1;
+            context.next_term(k);
+            d = context.extract_digit();
+            if d != -1 {break;}
+        }
+
+        print!("{}", d);
+        if i % 10 == 0 {print!("\t:{}\n", i);}
+
+        context.eliminate_digit(d);
+    }
+
+    let m = n % 10;
+    if m != 0 {
+        for _ in range(m, 10) { print!(" "); }
+        print!("\t:{}\n", n);
+    }
+}
+
+static DEFAULT_DIGITS: int = 512;
+
+#[bench]
+fn use_bencher(b: &mut Bencher) {
+    b.iter(|| pidigits(DEFAULT_DIGITS))
+}
+
+fn main() {
+    let args = std::os::args();
+    let args = args.as_slice();
+    let n = if args.len() < 2 {
+        DEFAULT_DIGITS
+    } else {
+        FromStr::from_str(args[1].as_slice()).unwrap()
+    };
+    pidigits(n);
+}