fannkuch-redux C clang #8 program
source code
/* The Computer Language Benchmarks Game
https://salsa.debian.org/benchmarksgame-team/benchmarksgame/
Naive transliteration from Rex Kerr's Scala program
contributed by Isaac Gouy
*/
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
int fannkuch(int n)
{
int perm1[n];
for (int i=0; i<n; i+=1) perm1[i] = i;
int perm[n];
int count[n];
int f = 0, flips = 0, nperm = 0, checksum = 0;
int i, k, r;
r = n;
while (r > 0) {
i = 0;
while (r != 1) { count[r-1] = r; r -= 1; }
while (i < n) { perm[i] = perm1[i]; i += 1; }
// Count flips and update max and checksum
f = 0;
k = perm[0];
while (k != 0) {
i = 0;
while (2*i < k) {
int t = perm[i]; perm[i] = perm[k-i]; perm[k-i] = t;
i += 1;
}
k = perm[0];
f += 1;
}
if (f > flips) flips = f;
if ((nperm & 0x1) == 0) checksum += f; else checksum -= f;
// Use incremental change to generate another permutation
bool more = true;
while (more) {
if (r == n) {
printf("%d\n", checksum);
return flips;
}
int p0 = perm1[0];
i = 0;
while (i < r) {
int j = i + 1;
perm1[i] = perm1[j];
i = j;
}
perm1[r] = p0;
count[r] -= 1;
if (count[r] > 0) more = false; else r += 1;
}
nperm += 1;
}
return flips;
}
int main(int argc, char *argv[])
{
int n = argc > 1 ? atoi(argv[1]) : 7;
printf("Pfannkuchen(%d) = %d\n", n, fannkuch(n));
return 0;
}
notes, command-line, and program output
NOTES:
64-bit Ubuntu quad core
Ubuntu clang version 18.1.8 (11)
Mon, 04 Nov 2024 01:11:17 GMT
MAKE:
/usr/bin/clang -pipe -Wall -O3 -fomit-frame-pointer -march=ivybridge fannkuchredux.clang-8.c -o fannkuchredux.clang-8.clang_run
rm fannkuchredux.clang-8.c
5.70s to complete and log all make actions
COMMAND LINE:
./fannkuchredux.clang-8.clang_run 12
PROGRAM OUTPUT:
3968050
Pfannkuchen(12) = 65