Merge pull request #66 from mlemanczyk/codex/analyze-locking-mechanisms-in-evenperfectbitscanner

Trim PrintResult critical work further

EvenPerfectBitScanner/Program.cs

@@ -23,6 +23,7 @@ internal static class Program
 	private const string PrimeFoundSuffix = " (FOUND VALID CANDIDATES)";
 	private static StringBuilder? _outputBuilder;
         private static readonly object Sync = new();
+        private static readonly object FileWriteSync = new();
 	private static int _consoleCounter;
 	private static int _writeIndex;
 	private static int _primeCount;
@@ -1349,6 +1350,51 @@ internal static class Program
 		}
 	}
 
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static bool TryAcquireConsoleSlot(bool primeCandidate, out bool primeFlag)
+        {
+                int consoleInterval = PerfectNumberConstants.ConsoleInterval;
+                int counterValue = Interlocked.Increment(ref _consoleCounter);
+                if (counterValue >= consoleInterval)
+                {
+                        int previous = Interlocked.Exchange(ref _consoleCounter, 0);
+                        if (previous >= consoleInterval)
+                        {
+                                primeFlag = primeCandidate;
+                                return true;
+                        }
+                }
+
+                primeFlag = false;
+                return false;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static StringBuilder? AppendToOutputBuffer(StringBuilder source)
+        {
+                StringBuilder? builderToFlush = null;
+
+                lock (Sync)
+                {
+                        StringBuilder outputBuilder = _outputBuilder!;
+                        _ = outputBuilder.Append(source);
+
+                        int nextIndex = _writeIndex + 1;
+                        if (nextIndex >= _writeBatchSize)
+                        {
+                                builderToFlush = outputBuilder;
+                                _outputBuilder = StringBuilderPool.Rent();
+                                _writeIndex = 0;
+                        }
+                        else
+                        {
+                                _writeIndex = nextIndex;
+                        }
+                }
+
+                return builderToFlush;
+        }
+
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private static void PrintResult(ulong currentP, bool searchedMersenne, bool detailedCheck, bool passedAllTests)
         {
@@ -1362,7 +1408,7 @@ internal static class Program
                 }
 
                 bool lastWasComposite = _lastCompositeP;
-		bool primeFlag = false, printToConsole = false;
+                bool primeCandidate = passedAllTests && !lastWasComposite && Volatile.Read(ref _primeFoundAfterInit);
 
                 StringBuilder localBuilder = StringBuilderPool.Rent();
                 _ = localBuilder
@@ -1371,26 +1417,12 @@ internal static class Program
                                 .Append(detailedCheck).Append(',')
                                 .Append(passedAllTests).Append('\n');
 
-		lock (Sync)
-		{
-			if (_consoleCounter >= PerfectNumberConstants.ConsoleInterval)
-			{
-				printToConsole = true;
-				primeFlag = passedAllTests && !lastWasComposite && _primeFoundAfterInit;
-				_consoleCounter = 0;
-			}
-			else
-			{
-				_consoleCounter++;
-			}
+                bool printToConsole = TryAcquireConsoleSlot(primeCandidate, out bool primeFlag);
+                StringBuilder? builderToFlush = AppendToOutputBuffer(localBuilder);
 
-			_ = _outputBuilder!.Append(localBuilder);
-
-			_writeIndex++;
-			if (_writeIndex >= _writeBatchSize)
+                if (builderToFlush is not null)
                 {
-				FlushBuffer();
-			}
+                        FlushBuffer(builderToFlush);
                 }
 
                 if (printToConsole)
@@ -1413,19 +1445,41 @@ internal static class Program
 	[MethodImpl(MethodImplOptions.AggressiveInlining)]
         private static void FlushBuffer()
         {
-		var stream = new FileStream(ResultsFileName, FileMode.Append, FileAccess.Write, FileShare.Read);
-		var writer = new StreamWriter(stream) { AutoFlush = false };
+                StringBuilder? builderToFlush = null;
 
-		if (_writeIndex > 0)
+                lock (Sync)
                 {
-			writer.Write(_outputBuilder);
-			writer.Flush();
-			_outputBuilder!.Clear();
+                        if (_writeIndex == 0 || _outputBuilder is null || _outputBuilder.Length == 0)
+                        {
+                                return;
+                        }
+
+                        builderToFlush = _outputBuilder;
+                        _outputBuilder = StringBuilderPool.Rent();
                         _writeIndex = 0;
                 }
 
-		writer.Dispose();
-		stream.Dispose();
+                FlushBuffer(builderToFlush!);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void FlushBuffer(StringBuilder builderToFlush)
+        {
+                try
+                {
+                        lock (FileWriteSync)
+                        {
+                                using FileStream stream = new(ResultsFileName, FileMode.Append, FileAccess.Write, FileShare.Read);
+                                using StreamWriter writer = new(stream) { AutoFlush = false };
+                                writer.Write(builderToFlush);
+                                writer.Flush();
+                        }
+                }
+                finally
+                {
+                        builderToFlush.Clear();
+                        StringBuilderPool.Return(builderToFlush);
+                }
         }
 
 	[MethodImpl(MethodImplOptions.AggressiveInlining)]