data.perf

Compiling with --cfg idx_reverse --opt-level=3

Samples: 27K of event 'cycles', Event count (approx.): 18709445305
 39.57%  fannkuchredux  fannkuchredux       [.] fannkuch::h3c886b0c9fd4152cYda
 37.13%  fannkuchredux  fannkuchredux       [.] reverse::h8a92c2595b4c13ffaca
 11.71%  fannkuchredux  fannkuchredux       [.] next_permutation::h0b3a5cb57aef64bcdba
  7.96%  fannkuchredux  fannkuchredux       [.] rotate::ha766464a328f18a5Kaa
  3.40%  fannkuchredux  fannkuchredux       [.] vec::Vec$LT$T$GT$::push_all::h9473677268961327811
  0.01%  fannkuchredux  [kernel.kallsyms]   [k] native_write_msr_safe

fannkuchredux.rs

// The Computer Language Benchmarks Game
// http://benchmarksgame.alioth.debian.org/
//
// contributed by the Rust Project Developers

// Copyright (c) 2014 The Rust Project Developers
//
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//
// - Redistributions of source code must retain the above copyright
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//   the documentation and/or other materials provided with the
//   distribution.
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//   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.
//
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// "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 test;

use std::cmp::max;
use std::mem;

#[inline(never)]
fn fact(n: uint) -> uint {
    range(1, n + 1).fold(1, |accu, i| accu * i)
}

#[inline(never)]
fn rotate(x: &mut [i32]) {
    let mut prev = x[0];
    for place in x.mut_iter().rev() {
        prev = mem::replace(place, prev)
    }
}
#[inline(never)]
fn next_permutation(perm: &mut [i32], count: &mut [uint]) {
    for i in range(1, perm.len()) {
        rotate(perm.mut_slice_to(i + 1));
        let count_i = &mut count[i];
        if *count_i >= i {
            *count_i = 0;
        } else {
            *count_i += 1;
            break
        }
    }
}

#[inline(never)]
fn reverse(tperm: &mut [i32], mut k: uint) {
    if cfg!(idx_reverse) {
        let mut i = 0;
        k -= 1;
        while i < k {
            unsafe {
                std::ptr::swap(tperm.unsafe_mut_ref(i), tperm.unsafe_mut_ref(k));
            }
            i += 1;
            k -= 1;
        }
    } else if cfg!(ptr_reverse) {
        unsafe {
            let mut p = tperm.as_mut_ptr();
            let mut q = p.offset(k as int - 1);

            while p < q {
                use std::ptr;
                ptr::swap(p, q);
                p = p.offset(1);
                q = q.offset(-1);
            }
        }
    } else if cfg!(iter_reverse) {
        tperm.mut_slice_to(k).mut_iter().reverse_()
    } else {
        tperm.mut_slice_to(k).reverse()
    }
}

#[inline(never)]
fn fannkuch(n: uint, i: uint) -> (int, int) {
    let mut perm = Vec::from_fn(n, |e| ((n + e - i) % n + 1) as i32);
    let mut tperm = perm.clone();
    let mut count = Vec::from_elem(n, 0u);
    let mut perm_count = 0i;
    let mut checksum = 0;

    for countdown in range(1, fact(n - 1) + 1).rev() {
        next_permutation(perm.as_mut_slice(), count.as_mut_slice());

        tperm.clone_from(&perm);
        let mut flips_count = 0;
        loop {
            let k = tperm[0];
            if k == 1 { break; }
            reverse(tperm.as_mut_slice(), k as uint);
            flips_count += 1;
        }
        perm_count = max(perm_count, flips_count);
        checksum += if countdown & 1 == 1 {flips_count} else {-flips_count}
    }
    (checksum, perm_count)
}

fn main() {
    let n = std::os::args().as_slice()
                           .get(1)
                           .and_then(|arg| from_str(arg.as_slice()))
                           .unwrap_or(2u);

    let (tx, rx) = channel();
    for i in range(0, n) {
        let tx = tx.clone();
        spawn(proc() tx.send(fannkuch(n, i)));
    }
    drop(tx);

    let mut checksum = 0;
    let mut perm = 0;
    for (cur_cks, cur_perm) in rx.iter() {
        checksum += cur_cks;
        perm = max(perm, cur_perm);
    }
    println!("{}\nPfannkuchen({}) = {}", checksum, n, perm);
}