bench: Update shootout-ackermann for performance

src/test/bench/shootout-ackermann.rs

@@ -1,25 +1,24 @@
+use std;
 
-
-
-// -*- rust -*-
 fn ack(m: int, n: int) -> int {
     if m == 0 {
-        ret n + 1;
+        ret n + 1
     } else {
         if n == 0 {
             ret ack(m - 1, 1);
-        } else { ret ack(m - 1, ack(m, n - 1)); }
+        } else {
+            ret ack(m - 1, ack(m, n - 1));
+        }
     }
 }
 
-fn main() {
-    assert (ack(0, 0) == 1);
-    assert (ack(3, 2) == 29);
-    assert (ack(3, 4) == 125);
-    // This takes a while; but a comparison may amuse: on win32 at least, the
-    // posted C version of the 'benchmark' running ack(4,1) overruns its stack
-    // segment and crashes. We just grow our stack (to 4mb) as we go.
-
-    // assert (ack(4,1) == 65533);
-
+fn main(args: [str]) {
+    // FIXME: #1527
+    sys::set_min_stack(1000000u);
+    let n = if vec::len(args) == 2u {
+        int::from_str(args[1])
+    } else {
+        11
+    };
+    std::io::println(#fmt("Ack(3,%d): %d\n", n, ack(3, n)));
 }