source code
/* The Computer Language Benchmarks Game
https://salsa.debian.org/benchmarksgame-team/benchmarksgame/
contributed by Isaac Gouy, transliterated from Oleg Mazurov's Java program
concurrency fix and minor improvements by Peperud
parallel and small optimisations by Anthony Lloyd
*/
using System;
using System.Threading;
public static class FannkuchRedux
{
static int taskCount;
static int[] fact, chkSums, maxFlips;
static void firstPermutation(int[] p, int[] pp, int[] count, int idx)
{
for (int i=0; i<p.Length; ++i) p[i] = i;
for (int i=count.Length-1; i>0; --i)
{
int d = idx/fact[i];
count[i] = d;
if(d>0)
{
idx = idx%fact[i];
for (int j=i ;j>=0; --j) pp[j] = p[j];
for (int j = 0; j <= i; ++j) p[j] = pp[(j+d)%(i+1)];
}
}
}
static int nextPermutation(int[] p, int[] count)
{
int first = p[1];
p[1] = p[0];
p[0] = first;
int i = 1;
while (++count[i] > i)
{
count[i++] = 0;
int next = p[1];
p[0] = next;
for(int j=1;j<i;) p[j] = p[++j];
p[i] = first;
first = next;
}
return first;
}
static int countFlips(int first, int[] p, int[] pp)
{
if (first==0) return 0;
if (p[first]==0) return 1;
for(int i=0; i<pp.Length; i++) pp[i] = p[i];
int flips = 2;
while(true)
{
for (int lo=1,hi=first-1; lo<hi; lo++,hi--)
{
int t = pp[lo];
pp[lo] = pp[hi];
pp[hi] = t;
}
int tp = pp[first];
if (pp[tp]==0) return flips;
pp[first] = first;
first = tp;
flips++;
}
}
static void run(int n, int taskSize)
{
int[] p = new int[n], pp = new int[n], count = new int[n];
int taskId = 0, chksum = 0, maxflips = 0;
while((taskId = Interlocked.Decrement(ref taskCount)) >= 0)
{
firstPermutation(p, pp, count, taskId*taskSize);
var flips = countFlips(p[0], p, pp);
chksum += flips;
if(flips>maxflips) maxflips = flips;
for(int i=1; i<taskSize; i++)
{
flips = countFlips(nextPermutation(p, count), p, pp);
chksum += (1-(i%2)*2) * flips;
if(flips>maxflips) maxflips = flips;
}
}
chkSums[-taskId-1] = chksum;
maxFlips[-taskId-1] = maxflips;
}
public static void Main(string[] args)
{
int n = args.Length > 0 ? int.Parse(args[0]) : 7;
fact = new int[n+1];
fact[0] = 1;
var factn = 1;
for (int i=1; i<fact.Length; i++) { fact[i] = factn *= i; }
taskCount = n>9 ? factn/(7*6*5*4*3*2) : Environment.ProcessorCount;
int taskSize = factn/taskCount;
int nThreads = Environment.ProcessorCount;
chkSums = new int[nThreads];
maxFlips = new int[nThreads];
var threads = new Thread[nThreads];
for(int i=1; i<nThreads; i++)
{
(threads[i] = new Thread(() => run(n, taskSize))).Start();
}
run(n, taskSize);
int chksum=chkSums[0], maxflips=maxFlips[0];
for(int i=1; i<threads.Length; i++)
{
threads[i].Join();
chksum += chkSums[i];
if(maxFlips[i]>maxflips) maxflips = maxFlips[i];
}
Console.Out.WriteLineAsync(chksum+"\nPfannkuchen("+n+") = "+maxflips);
}
}
notes, command-line, and program output
NOTES:
64-bit Ubuntu quad core
.NET SDK 8.0.200
Host Version: 8.0.2
Commit: 1381d5ebd2
<ServerGarbageCollection>true
<PublishAot>true
Thu, 07 Mar 2024 00:06:38 GMT
MAKE:
cp fannkuchredux.csharpaot-6.csharpaot Program.cs
cp Include/csharpaot/tmp.csproj .
mkdir obj
cp Include/csharpaot/project.assets.json ./obj
/usr/bin/dotnet publish -c Release -r linux-x64
MSBuild version 17.9.4+90725d08d for .NET
Determining projects to restore...
Restored /home/dunham/all-benchmarksgame/benchmarksgame_i53330/fannkuchredux/tmp/tmp.csproj (in 876 ms).
/home/dunham/all-benchmarksgame/benchmarksgame_i53330/fannkuchredux/tmp/Program.cs(15,18): warning CS8618: Non-nullable field 'fact' must contain a non-null value when exiting constructor. Consider declaring the field as nullable. [/home/dunham/all-benchmarksgame/benchmarksgame_i53330/fannkuchredux/tmp/tmp.csproj]
/home/dunham/all-benchmarksgame/benchmarksgame_i53330/fannkuchredux/tmp/Program.cs(15,24): warning CS8618: Non-nullable field 'chkSums' must contain a non-null value when exiting constructor. Consider declaring the field as nullable. [/home/dunham/all-benchmarksgame/benchmarksgame_i53330/fannkuchredux/tmp/tmp.csproj]
/home/dunham/all-benchmarksgame/benchmarksgame_i53330/fannkuchredux/tmp/Program.cs(15,33): warning CS8618: Non-nullable field 'maxFlips' must contain a non-null value when exiting constructor. Consider declaring the field as nullable. [/home/dunham/all-benchmarksgame/benchmarksgame_i53330/fannkuchredux/tmp/tmp.csproj]
tmp -> /home/dunham/all-benchmarksgame/benchmarksgame_i53330/fannkuchredux/tmp/bin/Release/net8.0/linux-x64/tmp.dll
Generating native code
tmp -> /home/dunham/all-benchmarksgame/benchmarksgame_i53330/fannkuchredux/tmp/bin/Release/net8.0/linux-x64/publish/
18.70s to complete and log all make actions
COMMAND LINE:
./bin/Release/net8.0/linux-x64/publish/tmp 12
PROGRAM OUTPUT:
3968050
Pfannkuchen(12) = 65