diff --git a/src/test/bench/shootout-fannkuch-redux.rs b/src/test/bench/shootout-fannkuch-redux.rs index fbea63e65f126..4bea355472de1 100644 --- a/src/test/bench/shootout-fannkuch-redux.rs +++ b/src/test/bench/shootout-fannkuch-redux.rs @@ -8,94 +8,65 @@ // option. This file may not be copied, modified, or distributed // except according to those terms. -use std::os; +use std::cmp::max; -fn max(a: i32, b: i32) -> i32 { - if a > b { - a - } else { - b - } +fn fact(n: uint) -> uint { + range(1, n + 1).fold(1, |accu, i| accu * i) } -fn fannkuch_redux(n: i32) -> i32 { - let mut perm = Vec::from_elem(n as uint, 0i32); - let mut perm1 = Vec::from_fn(n as uint, |i| i as i32); - let mut count = Vec::from_elem(n as uint, 0i32); - let mut max_flips_count = 0i32; - let mut perm_count = 0i32; - let mut checksum = 0i32; - - let perm = perm.as_mut_slice(); - let perm1 = perm1.as_mut_slice(); - let count = count.as_mut_slice(); - - let mut r = n; - loop { - while r != 1 { - count[r as uint - 1] = r; - r -= 1; - } - - for (perm_i, perm1_i) in perm.mut_iter().zip(perm1.iter()) { - *perm_i = *perm1_i; - } +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 = 0; + let mut checksum = 0; - let mut flips_count: i32 = 0; - let mut k: i32; - loop { - k = perm[0]; - if k == 0 { - break; + for countdown in range(1, fact(n - 1) + 1).rev() { + for i in range(1, n) { + let perm0 = *perm.get(0); + for j in range(0, i) { + *perm.get_mut(j) = *perm.get(j + 1); } + *perm.get_mut(i) = perm0; - let k2 = (k+1) >> 1; - for i in range(0i32, k2) { - perm.swap(i as uint, (k - i) as uint); + let count_i = count.get_mut(i); + if *count_i >= i { + *count_i = 0; + } else { + *count_i += 1; + break; } - flips_count += 1; } - max_flips_count = max(max_flips_count, flips_count); - checksum += if perm_count % 2 == 0 { - flips_count - } else { - -flips_count - }; - - // Use incremental change to generate another permutation. + tperm.clone_from(&perm); + let mut flips_count = 0; loop { - if r == n { - println!("{}", checksum); - return max_flips_count; - } - - let perm0 = perm1[0]; - let mut i: i32 = 0; - while i < r { - let j = i + 1; - perm1[i as uint] = perm1[j as uint]; - i = j; - } - perm1[r as uint] = perm0; - - count[r as uint] -= 1; - if count[r as uint] > 0 { - break; - } - r += 1; + let k = *tperm.get(0); + if k == 1 { break; } + tperm.mut_slice_to(k as uint).reverse(); + flips_count += 1; } - - perm_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 args = os::args(); - let n = if args.len() > 1 { - from_str::(args[1]).unwrap() - } else { - 2 - }; - println!("Pfannkuchen({}) = {}", n as int, fannkuch_redux(n) as int); + let n = std::os::args().get(1).and_then(|arg| from_str(*arg)).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); }