fannkuch-redux Swift program
source code
/* The Computer Language Benchmarks Game
https://salsa.debian.org/benchmarksgame-team/benchmarksgame/
contributed by Isaac Gouy
transliterated from Rex Kerr's Scala program
*/
func fannkuch(_ n: Int) -> Int {
var perm = Array(repeating: 0, count: n),
count = Array(repeating: 0, count: n)
var perm1 = Array(repeating: 0, count: n)
for j in 0...n-1 { perm1[j] = j }
var f = 0, i = 0, k = 0, r = 0, flips = 0, nperm = 0, checksum = 0
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 {
let 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
var go = true
while go {
if r == n {
print(checksum)
return flips
}
let p0 = perm1[0]
i = 0
while i < r {
let j = i+1
perm1[i] = perm1[j]
i = j
}
perm1[r] = p0
count[r] -= 1
if count[r] > 0 { go = false } else { r += 1 }
}
nperm += 1
}
return flips
}
let n: Int = Int(CommandLine.arguments[1])!
print("Pfannkuchen(\(n)) = \(fannkuch(n))")
notes, command-line, and program output
NOTES:
64-bit Ubuntu quad core
Swift version 6.0
(swift-6.0-RELEASE)
Target: x86_64-unknown-linux-gnu
Wed, 18 Sep 2024 23:09:15 GMT
MAKE:
/opt/src/swift-6.0-RELEASE/usr/bin/swiftc fannkuchredux.swift -Ounchecked -wmo -o fannkuchredux.swift_run
12.57s to complete and log all make actions
COMMAND LINE:
./fannkuchredux.swift_run 12
PROGRAM OUTPUT:
3968050
Pfannkuchen(12) = 65