Pools made thread static. Various small optimizations. "in" parameter added to read-only method parameters

PerfectNumbers.Core.Tests/MersenneNumberDivisorByDivisorTesterTests.cs

@@ -70,7 +70,7 @@ public class MersenneNumberDivisorByDivisorTesterTests
             return new DummySession();
         }
 
-        public void PrepareCandidates(ReadOnlySpan<ulong> primes, Span<ulong> allowedMaxValues)
+        public void PrepareCandidates(in ReadOnlySpan<ulong> primes, Span<ulong> allowedMaxValues)
         {
             for (int i = 0; i < primes.Length; i++)
             {
@@ -80,7 +80,7 @@ public class MersenneNumberDivisorByDivisorTesterTests
 
         private sealed class DummySession : IMersenneNumberDivisorByDivisorTester.IDivisorScanSession
         {
-            public void CheckDivisor(ulong divisor, in MontgomeryDivisorData divisorData, ulong divisorCycle, ReadOnlySpan<ulong> primes, Span<byte> hits)
+            public void CheckDivisor(ulong divisor, in MontgomeryDivisorData divisorData, ulong divisorCycle, in ReadOnlySpan<ulong> primes, Span<byte> hits)
             {
                 throw new NotSupportedException();
             }

PerfectNumbers.Core/Cpu/MersenneNumberDivisorByDivisorCpuTester.cs

@@ -1,18 +1,14 @@
-using System;
 using System.Collections.Concurrent;
-using System.Collections.Generic;
+using System.Runtime.CompilerServices;
-using System.Numerics;
-using PerfectNumbers.Core;
 
 namespace PerfectNumbers.Core.Cpu;
 
 public sealed class MersenneNumberDivisorByDivisorCpuTester : IMersenneNumberDivisorByDivisorTester
 {
     private readonly object _sync = new();
-    private readonly ConcurrentBag<DivisorScanSession> _sessionPool = new();
+    private readonly ConcurrentBag<DivisorScanSession> _sessionPool = [];
     private ulong _divisorLimit;
     private ulong _lastStatusDivisor;
-    private bool _isConfigured;
     private int _batchSize = 1_024;
 
 
@@ -24,55 +20,25 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester : IMersenneNumberDiv
 
     public void ConfigureFromMaxPrime(ulong maxPrime)
     {
-        lock (_sync)
+		_divisorLimit = ComputeDivisorLimitFromMaxPrime(maxPrime);
-        {
+		_lastStatusDivisor = 0UL;
-            _divisorLimit = ComputeDivisorLimitFromMaxPrime(maxPrime);
-            _lastStatusDivisor = 0UL;
-            _isConfigured = true;
-        }
     }
 
     public ulong DivisorLimit
-    {
+	{
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
         get
         {
-            lock (_sync)
+			return _divisorLimit;
-            {
-                if (!_isConfigured)
-                {
-                    throw new InvalidOperationException("ConfigureFromMaxPrime must be called before using the tester.");
-                }
-
-                return _divisorLimit;
-            }
         }
     }
 
-    public ulong GetAllowedMaxDivisor(ulong prime)
+	[MethodImpl(MethodImplOptions.AggressiveInlining)]
+	public ulong GetAllowedMaxDivisor(ulong prime) => ComputeAllowedMaxDivisor(prime, _divisorLimit);
+
+	public bool IsPrime(ulong prime, out bool divisorsExhausted)
     {
-        lock (_sync)
+        ulong allowedMax = ComputeAllowedMaxDivisor(prime, _divisorLimit);
-        {
-            if (!_isConfigured)
-            {
-                throw new InvalidOperationException("ConfigureFromMaxPrime must be called before using the tester.");
-            }
-
-            return ComputeAllowedMaxDivisor(prime, _divisorLimit);
-        }
-    }
-
-    public bool IsPrime(ulong prime, out bool divisorsExhausted)
-    {
-        ulong allowedMax;
-        lock (_sync)
-        {
-            if (!_isConfigured)
-            {
-                throw new InvalidOperationException("ConfigureFromMaxPrime must be called before using the tester.");
-            }
-
-            allowedMax = ComputeAllowedMaxDivisor(prime, _divisorLimit);
-        }
 
         if (allowedMax < 3UL)
         {
@@ -81,13 +47,11 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester : IMersenneNumberDiv
         }
 
         ulong processedCount;
-        ulong lastProcessed;
         bool processedAll;
 
         bool composite = CheckDivisors(
             prime,
             allowedMax,
-            out lastProcessed,
             out processedAll,
             out processedCount);
 
@@ -109,26 +73,11 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester : IMersenneNumberDiv
         return true;
     }
 
-    public void PrepareCandidates(ReadOnlySpan<ulong> primes, Span<ulong> allowedMaxValues)
+    public void PrepareCandidates(in ReadOnlySpan<ulong> primes, Span<ulong> allowedMaxValues)
     {
-        if (allowedMaxValues.Length < primes.Length)
+        ulong divisorLimit = _divisorLimit;
-        {
+		int length = primes.Length;
-            throw new ArgumentException("allowedMaxValues span must be at least as long as primes span.", nameof(allowedMaxValues));
+		for (int index = 0; index < length; index++)
-        }
-
-        ulong divisorLimit;
-
-        lock (_sync)
-        {
-            if (!_isConfigured)
-            {
-                throw new InvalidOperationException("ConfigureFromMaxPrime must be called before using the tester.");
-            }
-
-            divisorLimit = _divisorLimit;
-        }
-
-        for (int index = 0; index < primes.Length; index++)
         {
             allowedMaxValues[index] = ComputeAllowedMaxDivisor(primes[index], divisorLimit);
         }
@@ -136,21 +85,13 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester : IMersenneNumberDiv
 
     public IMersenneNumberDivisorByDivisorTester.IDivisorScanSession CreateDivisorSession()
     {
-        lock (_sync)
+		if (_sessionPool.TryTake(out DivisorScanSession? session))
-        {
+		{
-            if (!_isConfigured)
+			session.Reset();
-            {
+			return session;
-                throw new InvalidOperationException("ConfigureFromMaxPrime must be called before using the tester.");
+		}
-            }
 
-            if (_sessionPool.TryTake(out DivisorScanSession? session))
+		return new DivisorScanSession(this);
-            {
-                session.Reset();
-                return session;
-            }
-
-            return new DivisorScanSession(this);
-        }
     }
 
     private void ReturnSession(DivisorScanSession session)
@@ -161,11 +102,9 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester : IMersenneNumberDiv
     private bool CheckDivisors(
         ulong prime,
         ulong allowedMax,
-        out ulong lastProcessed,
         out bool processedAll,
         out ulong processedCount)
     {
-        lastProcessed = 0UL;
         processedCount = 0UL;
         processedAll = false;
 
@@ -214,7 +153,6 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester : IMersenneNumberDiv
         {
             ulong candidate = (ulong)divisor;
             processedCount++;
-            lastProcessed = candidate;
 
             bool admissible = lastIsSeven
                 ? (remainder10 == 3 || remainder10 == 7 || remainder10 == 9)
@@ -348,13 +286,8 @@ public sealed class MersenneNumberDivisorByDivisorCpuTester : IMersenneNumberDiv
             _disposed = false;
         }
 
-        public void CheckDivisor(ulong divisor, in MontgomeryDivisorData divisorData, ulong divisorCycle, ReadOnlySpan<ulong> primes, Span<byte> hits)
+        public void CheckDivisor(ulong divisor, in MontgomeryDivisorData divisorData, ulong divisorCycle, in ReadOnlySpan<ulong> primes, Span<byte> hits)
         {
-            if (_disposed)
-            {
-                throw new ObjectDisposedException(nameof(DivisorScanSession));
-            }
-
             int length = primes.Length;
             if (length == 0)
             {

PerfectNumbers.Core/FactorEntry128.cs

@@ -0,0 +1,8 @@
+namespace PerfectNumbers.Core;
+
+public readonly struct FactorEntry128(in UInt128 value, int exponent)
+{
+	public readonly UInt128 Value = value;
+
+	public readonly int Exponent = exponent;
+}

PerfectNumbers.Core/Gpu/MersenneNumberDivisorByDivisorGpuTester.cs

@@ -148,7 +148,7 @@ public sealed class MersenneNumberDivisorByDivisorGpuTester : IMersenneNumberDiv
         return true;
     }
 
-    public void PrepareCandidates(ReadOnlySpan<ulong> primes, Span<ulong> allowedMaxValues)
+    public void PrepareCandidates(in ReadOnlySpan<ulong> primes, Span<ulong> allowedMaxValues)
     {
         if (allowedMaxValues.Length < primes.Length)
         {
@@ -583,7 +583,7 @@ public sealed class MersenneNumberDivisorByDivisorGpuTester : IMersenneNumberDiv
             _disposed = false;
         }
 
-        public void CheckDivisor(ulong divisor, in MontgomeryDivisorData divisorData, ulong divisorCycle, ReadOnlySpan<ulong> primes, Span<byte> hits)
+        public void CheckDivisor(ulong divisor, in MontgomeryDivisorData divisorData, ulong divisorCycle, in ReadOnlySpan<ulong> primes, Span<byte> hits)
         {
             if (_disposed)
             {

PerfectNumbers.Core/IMersenneNumberDivisorByDivisorTester.cs

@@ -16,10 +16,10 @@ public interface IMersenneNumberDivisorByDivisorTester
 
     IDivisorScanSession CreateDivisorSession();
 
-    void PrepareCandidates(ReadOnlySpan<ulong> primes, Span<ulong> allowedMaxValues);
+    void PrepareCandidates(in ReadOnlySpan<ulong> primes, Span<ulong> allowedMaxValues);
 
     public interface IDivisorScanSession : IDisposable
     {
-        void CheckDivisor(ulong divisor, in MontgomeryDivisorData divisorData, ulong divisorCycle, ReadOnlySpan<ulong> primes, Span<byte> hits);
+        void CheckDivisor(ulong divisor, in MontgomeryDivisorData divisorData, ulong divisorCycle, in ReadOnlySpan<ulong> primes, Span<byte> hits);
     }
 }

PerfectNumbers.Core/MersenneNumberDivisorByDivisorTester.cs

@@ -10,129 +10,126 @@ namespace PerfectNumbers.Core;
 
 public static class MersenneNumberDivisorByDivisorTester
 {
-    public static void Run(
+	public static void Run(
-            List<ulong> candidates,
+			List<ulong> candidates,
-            IMersenneNumberDivisorByDivisorTester tester,
+			IMersenneNumberDivisorByDivisorTester tester,
-            Dictionary<ulong, (bool DetailedCheck, bool PassedAllTests)>? previousResults,
+			Dictionary<ulong, (bool DetailedCheck, bool PassedAllTests)>? previousResults,
-            ulong startPrime,
+			ulong startPrime,
-            Action markComposite,
+			Action markComposite,
-            Action clearComposite,
+			Action clearComposite,
-            Action<ulong, bool, bool, bool> printResult,
+			Action<ulong, bool, bool, bool> printResult,
-            int threadCount)
+			int threadCount)
-    {
+	{
-        if (candidates.Count == 0)
+		if (candidates.Count == 0)
-        {
+		{
-            Console.WriteLine("No candidates were provided for --mersenne=bydivisor.");
+			Console.WriteLine("No candidates were provided for --mersenne=bydivisor.");
-            return;
+			return;
-        }
+		}
 
-        _ = threadCount;
+		_ = threadCount;
 
-        candidates.Sort();
+		candidates.Sort();
-        Span<ulong> candidateSpan = CollectionsMarshal.AsSpan(candidates);
+		Span<ulong> candidateSpan = CollectionsMarshal.AsSpan(candidates);
-        int candidateCount = candidateSpan.Length;
+		int candidateCount = candidateSpan.Length;
 
-        bool applyStartPrime = startPrime > 0UL;
+		bool applyStartPrime = startPrime > 0UL;
-        int skippedByPreviousResults = 0;
+		int skippedByPreviousResults = 0;
 
-        if (previousResults is not null && previousResults.Count > 0)
+		ArrayPool<ulong> pool = ThreadStaticPools.UlongPool;
-        {
+		if (previousResults is not null && previousResults.Count > 0)
-            int recordedCount = previousResults.Count;
+		{
-            ulong[] recordedCandidates = ArrayPool<ulong>.Shared.Rent(recordedCount);
+			int recordedCount = previousResults.Count;
-            try
+			ulong[] recordedCandidates = pool.Rent(recordedCount);
-            {
-                Span<ulong> recordedSpan = recordedCandidates.AsSpan(0, recordedCount);
-                int recordedIndex = 0;
-                foreach (ulong value in previousResults.Keys)
-                {
-                    recordedSpan[recordedIndex++] = value;
-                }
 
-                recordedSpan.Sort();
+			Span<ulong> recordedSpan = recordedCandidates.AsSpan(0, recordedCount);
+			int recordedIndex = 0;
+			foreach (ulong value in previousResults.Keys)
+			{
+				recordedSpan[recordedIndex++] = value;
+			}
 
-                int writeIndex = 0;
+			recordedSpan.Sort();
-                int skipIndex = 0;
 
-                for (int readIndex = 0; readIndex < candidateCount; readIndex++)
+			int writeIndex = 0;
-                {
+			int skipIndex = 0;
-                    ulong candidate = candidateSpan[readIndex];
 
-                    while (skipIndex < recordedCount && recordedSpan[skipIndex] < candidate)
+			for (int readIndex = 0; readIndex < candidateCount; readIndex++)
-                    {
+			{
-                        skipIndex++;
+				ulong candidate = candidateSpan[readIndex];
-                    }
 
-                    if (skipIndex < recordedCount && recordedSpan[skipIndex] == candidate)
+				while (skipIndex < recordedCount && recordedSpan[skipIndex] < candidate)
-                    {
+				{
-                        skippedByPreviousResults++;
+					skipIndex++;
-                        skipIndex++;
+				}
-                        continue;
-                    }
 
-                    candidateSpan[writeIndex++] = candidate;
+				if (skipIndex < recordedCount && recordedSpan[skipIndex] == candidate)
-                }
+				{
+					skippedByPreviousResults++;
+					skipIndex++;
+					continue;
+				}
 
-                if (writeIndex < candidateCount)
+				candidateSpan[writeIndex++] = candidate;
-                {
+			}
-                    candidates.RemoveRange(writeIndex, candidateCount - writeIndex);
-                    candidateSpan = CollectionsMarshal.AsSpan(candidates);
-                    candidateCount = candidateSpan.Length;
-                }
-            }
-            finally
-            {
-                ArrayPool<ulong>.Shared.Return(recordedCandidates, clearArray: true);
-            }
-        }
 
-        if (skippedByPreviousResults > 0)
+			if (writeIndex < candidateCount)
-        {
+			{
-            Console.WriteLine($"Skipped {skippedByPreviousResults.ToString(CultureInfo.InvariantCulture)} candidates excluded by previous results.");
+				candidates.RemoveRange(writeIndex, candidateCount - writeIndex);
-        }
+				candidateSpan = CollectionsMarshal.AsSpan(candidates);
+				candidateCount = candidateSpan.Length;
+			}
 
-        int startIndex = 0;
+			pool.Return(recordedCandidates, clearArray: true);
-        if (applyStartPrime)
+		}
-        {
-            startIndex = candidates.BinarySearch(startPrime);
-            if (startIndex < 0)
-            {
-                startIndex = ~startIndex;
-            }
-            else
-            {
-                while (startIndex > 0 && candidates[startIndex - 1] >= startPrime)
-                {
-                    startIndex--;
-                }
-            }
-        }
 
-        List<ulong> primesToTest = candidates;
+		if (skippedByPreviousResults > 0)
-        Span<ulong> primesSpan = CollectionsMarshal.AsSpan(primesToTest);
+		{
-        ulong maxPrime = 0UL;
+			Console.WriteLine($"Skipped {skippedByPreviousResults.ToString(CultureInfo.InvariantCulture)} candidates excluded by previous results.");
-        int primeWriteIndex = 0;
+		}
+
+		int startIndex = 0;
+		if (applyStartPrime)
+		{
+			startIndex = candidates.BinarySearch(startPrime);
+			if (startIndex < 0)
+			{
+				startIndex = ~startIndex;
+			}
+			else
+			{
+				while (startIndex > 0 && candidates[startIndex - 1] >= startPrime)
+				{
+					startIndex--;
+				}
+			}
+		}
+
+		List<ulong> primesToTest = candidates;
+		Span<ulong> primesSpan = CollectionsMarshal.AsSpan(primesToTest);
+		ulong maxPrime = 0UL;
+		int primeWriteIndex = 0;
 
 		// This implementation is terribly slow, while this method expect prime p given as --filter-p input already.
 		// We don't need to additionally check it.
 
-        // using IEnumerator<ulong> primeEnumerator = Prime.Numbers.GetEnumerator();
+		// using IEnumerator<ulong> primeEnumerator = Prime.Numbers.GetEnumerator();
-        // bool hasPrime = primeEnumerator.MoveNext();
+		// bool hasPrime = primeEnumerator.MoveNext();
-        // ulong currentPrime = hasPrime ? primeEnumerator.Current : 0UL;
+		// ulong currentPrime = hasPrime ? primeEnumerator.Current : 0UL;
 
-        for (int index = startIndex; index < candidateCount; index++)
+		for (int index = startIndex; index < candidateCount; index++)
-        {
+		{
-            ulong candidate = primesSpan[index];
+			ulong candidate = primesSpan[index];
 
-            if (candidate <= 1UL)
+			if (candidate <= 1UL)
-            {
+			{
-                markComposite();
+				markComposite();
-                printResult(candidate, false, false, false);
+				printResult(candidate, false, false, false);
-                continue;
+				continue;
-            }
+			}
 
 			// This implementation is terribly slow, while this method expect prime p given as --filter-p input already.
 			// We don't need to additionally check it.
-			
+
 			// while (hasPrime && currentPrime < candidate)
 			// {
 			//     hasPrime = primeEnumerator.MoveNext();
@@ -154,123 +151,118 @@ public static class MersenneNumberDivisorByDivisorTester
 
 			primesSpan[primeWriteIndex++] = candidate;
 
-            if (candidate > maxPrime)
+			if (candidate > maxPrime)
-            {
+			{
-                maxPrime = candidate;
+				maxPrime = candidate;
-            }
+			}
-        }
+		}
 
-        if (primeWriteIndex < primesToTest.Count)
+		if (primeWriteIndex < primesToTest.Count)
-        {
+		{
-            primesToTest.RemoveRange(primeWriteIndex, primesToTest.Count - primeWriteIndex);
+			primesToTest.RemoveRange(primeWriteIndex, primesToTest.Count - primeWriteIndex);
-        }
+		}
 
-        if (primesToTest.Count == 0)
+		if (primesToTest.Count == 0)
-        {
+		{
-            if (applyStartPrime)
+			if (applyStartPrime)
-            {
+			{
-                Console.WriteLine($"No primes greater than or equal to {startPrime.ToString(CultureInfo.InvariantCulture)} were found for --mersenne=bydivisor.");
+				Console.WriteLine($"No primes greater than or equal to {startPrime.ToString(CultureInfo.InvariantCulture)} were found for --mersenne=bydivisor.");
-            }
+			}
-            else
+			else
-            {
+			{
-                Console.WriteLine("No prime candidates remain for --mersenne=bydivisor after filtering.");
+				Console.WriteLine("No prime candidates remain for --mersenne=bydivisor after filtering.");
-            }
+			}
 
-            return;
+			return;
-        }
+		}
 
-        if (maxPrime <= 1UL)
+		if (maxPrime <= 1UL)
-        {
+		{
-            Console.WriteLine("The filter specified by --filter-p must contain at least one prime exponent greater than 1 for --mersenne=bydivisor.");
+			Console.WriteLine("The filter specified by --filter-p must contain at least one prime exponent greater than 1 for --mersenne=bydivisor.");
-            return;
+			return;
-        }
+		}
 
-        tester.ConfigureFromMaxPrime(maxPrime);
+		tester.ConfigureFromMaxPrime(maxPrime);
 
-        int primeCount = primesToTest.Count;
+		int primeCount = primesToTest.Count;
-        ulong[] primeBatch = ArrayPool<ulong>.Shared.Rent(primeCount);
+		ulong[] primeBatch = pool.Rent(primeCount);
-        ulong[] allowedMaxBatch = ArrayPool<ulong>.Shared.Rent(primeCount);
+		ulong[] allowedMaxBatch = pool.Rent(primeCount);
-        List<ulong> filteredPrimes = new(primeCount);
+		List<ulong> filteredPrimes = new(primeCount);
 
-        try
+		Span<ulong> primeSpan = primeBatch.AsSpan(0, primeCount);
-        {
+		Span<ulong> allowedMaxSpan = allowedMaxBatch.AsSpan(0, primeCount);
-            Span<ulong> primeSpan = primeBatch.AsSpan(0, primeCount);
-            Span<ulong> allowedMaxSpan = allowedMaxBatch.AsSpan(0, primeCount);
 
-            for (int i = 0; i < primeCount; i++)
+		for (int i = 0; i < primeCount; i++)
-            {
+		{
-                primeSpan[i] = primesToTest[i];
+			primeSpan[i] = primesToTest[i];
-            }
+		}
 
-            tester.PrepareCandidates(primeSpan, allowedMaxSpan);
+		tester.PrepareCandidates(primeSpan, allowedMaxSpan);
 
-            for (int i = 0; i < primeCount; i++)
+		for (int i = 0; i < primeCount; i++)
-            {
+		{
-                ulong prime = primeSpan[i];
+			ulong prime = primeSpan[i];
-                ulong allowedMax = allowedMaxSpan[i];
+			ulong allowedMax = allowedMaxSpan[i];
 
-                if (allowedMax < 3UL)
+			if (allowedMax < 3UL)
-                {
+			{
-                    clearComposite();
+				clearComposite();
-                    printResult(prime, true, true, true);
+				printResult(prime, true, true, true);
-                    continue;
+				continue;
-                }
+			}
 
-                filteredPrimes.Add(prime);
+			filteredPrimes.Add(prime);
-            }
+		}
-        }
-        finally
-        {
-            ArrayPool<ulong>.Shared.Return(allowedMaxBatch, clearArray: true);
-            ArrayPool<ulong>.Shared.Return(primeBatch, clearArray: true);
-        }
 
-        if (filteredPrimes.Count == 0)
+		pool.Return(allowedMaxBatch, clearArray: true);
-        {
+		pool.Return(primeBatch, clearArray: true);
-            if (applyStartPrime)
-            {
-                Console.WriteLine($"No primes greater than or equal to {startPrime.ToString(CultureInfo.InvariantCulture)} were found for --mersenne=bydivisor.");
-            }
 
-            return;
+		if (filteredPrimes.Count == 0)
-        }
+		{
+			if (applyStartPrime)
+			{
+				Console.WriteLine($"No primes greater than or equal to {startPrime.ToString(CultureInfo.InvariantCulture)} were found for --mersenne=bydivisor.");
+			}
 
-        int workerCount = threadCount <= 0 ? Environment.ProcessorCount : threadCount;
+			return;
-        if (workerCount < 1)
+		}
-        {
-            workerCount = 1;
-        }
 
-        void ProcessPrime(ulong prime)
+		int workerCount = threadCount <= 0 ? Environment.ProcessorCount : threadCount;
-        {
+		if (workerCount < 1)
-            bool isPrime = tester.IsPrime(prime, out bool divisorsExhausted);
+		{
+			workerCount = 1;
+		}
 
-            if (!isPrime)
+		void ProcessPrime(ulong prime)
-            {
+		{
-                markComposite();
+			bool isPrime = tester.IsPrime(prime, out bool divisorsExhausted);
-                printResult(prime, true, true, false);
-                return;
-            }
 
-            clearComposite();
+			if (!isPrime)
-            printResult(prime, true, divisorsExhausted, true);
+			{
-        }
+				markComposite();
+				printResult(prime, true, true, false);
+				return;
+			}
 
-        if (workerCount == 1)
+			clearComposite();
-        {
+			printResult(prime, true, divisorsExhausted, true);
-            foreach (ulong prime in filteredPrimes)
+		}
-            {
-                ProcessPrime(prime);
-            }
-        }
-        else
-        {
-            ParallelOptions options = new()
-            {
-                MaxDegreeOfParallelism = workerCount
-            };
 
-            Parallel.ForEach(filteredPrimes, options, ProcessPrime);
+		if (workerCount == 1)
-        }
+		{
-    }
+			foreach (ulong prime in filteredPrimes)
+			{
+				ProcessPrime(prime);
+			}
+		}
+		else
+		{
+			ParallelOptions options = new()
+			{
+				MaxDegreeOfParallelism = workerCount
+			};
+
+			Parallel.ForEach(filteredPrimes, options, ProcessPrime);
+		}
+	}
 }

PerfectNumbers.Core/PartialFactorResult.cs

@@ -38,8 +38,8 @@ namespace PerfectNumbers.Core
             return instance;
         }
 
-        public static readonly PartialFactorResult Empty = new PartialFactorResult
+        public static readonly PartialFactorResult Empty = new()
-        {
+		{
             Cofactor = 1UL,
             FullyFactored = true,
         };
@@ -70,7 +70,7 @@ namespace PerfectNumbers.Core
                 if (factors is not null)
                 {
                     Factors = null;
-                    ArrayPool<FactorEntry>.Shared.Return(factors, clearArray: false);
+                    ThreadStaticPools.FactorEntryPool.Return(factors, clearArray: false);
                 }
 
                 _next = s_poolHead;

PerfectNumbers.Core/PrimeOrderCalculator.Wide.cs

@@ -10,10 +10,10 @@ namespace PerfectNumbers.Core;
 internal static partial class PrimeOrderCalculator
 {
     public static UInt128 Calculate(
-        UInt128 prime,
+        in UInt128 prime,
-        UInt128? previousOrder,
+        in UInt128? previousOrder,
-        PrimeOrderSearchConfig config,
+        in PrimeOrderSearchConfig config,
-        PrimeOrderHeuristicDevice device)
+        in PrimeOrderHeuristicDevice device)
     {
         var scope = UsePow2Mode(device);
         MontgomeryDivisorData divisorData;
@@ -49,7 +49,7 @@ internal static partial class PrimeOrderCalculator
         return result;
     }
 
-    private static UInt128 CalculateWideInternal(UInt128 prime, UInt128? previousOrder, in MontgomeryDivisorData divisorData, PrimeOrderSearchConfig config)
+    private static UInt128 CalculateWideInternal(in UInt128 prime, in UInt128? previousOrder, in MontgomeryDivisorData divisorData, in PrimeOrderSearchConfig config)
     {
         if (prime <= UInt128.One)
         {
@@ -79,12 +79,12 @@ internal static partial class PrimeOrderCalculator
     }
 
     private static UInt128 RunHeuristicPipelineWide(
-        UInt128 prime,
+        in UInt128 prime,
-        UInt128? previousOrder,
+        in UInt128? previousOrder,
         in MontgomeryDivisorData divisorData,
-        PrimeOrderSearchConfig config,
+        in PrimeOrderSearchConfig config,
-        UInt128 phi,
+        in UInt128 phi,
-        PartialFactorResult128 phiFactors)
+        in PartialFactorResult128 phiFactors)
     {
         if (phiFactors.FullyFactored && TrySpecialMaxWide(phi, prime, divisorData, phiFactors))
         {
@@ -112,12 +112,12 @@ internal static partial class PrimeOrderCalculator
         return candidateOrder;
     }
 
-    private static UInt128 FinishStrictlyWide(UInt128 prime, in MontgomeryDivisorData divisorData)
+    private static UInt128 FinishStrictlyWide(in UInt128 prime, in MontgomeryDivisorData divisorData)
     {
         return CalculateByFactorizationWide(prime, divisorData);
     }
 
-    private static bool TrySpecialMaxWide(UInt128 phi, UInt128 prime, in MontgomeryDivisorData divisorData, PartialFactorResult128 factors)
+    private static bool TrySpecialMaxWide(in UInt128 phi, in UInt128 prime, in MontgomeryDivisorData divisorData, in PartialFactorResult128 factors)
     {
         ReadOnlySpan<FactorEntry128> factorSpan = factors.Factors;
         int length = factors.Count;
@@ -134,7 +134,7 @@ internal static partial class PrimeOrderCalculator
         return true;
     }
 
-    private static UInt128 InitializeStartingOrderWide(UInt128 prime, UInt128 phi, in MontgomeryDivisorData divisorData)
+    private static UInt128 InitializeStartingOrderWide(in UInt128 prime, in UInt128 phi, in MontgomeryDivisorData divisorData)
     {
         UInt128 order = phi;
         UInt128 mod8 = prime & (UInt128)7UL;
@@ -150,19 +150,20 @@ internal static partial class PrimeOrderCalculator
         return order;
     }
 
-    private static UInt128 ExponentLoweringWide(UInt128 order, UInt128 prime, in MontgomeryDivisorData divisorData, PartialFactorResult128 factors)
+    private static UInt128 ExponentLoweringWide(UInt128 order, in UInt128 prime, in MontgomeryDivisorData divisorData, in PartialFactorResult128 factors)
     {
-        FactorEntry128[]? tempArray = null;
+		ArrayPool<FactorEntry128> pool = ThreadStaticPools.FactorEntry128Pool;
+		ReadOnlySpan<FactorEntry128> factorSpan = factors.Factors;
+		int length = factors.Count;
+		// TODO: This should never trigger from production code - check
+		// if (length == 0)
+		// {
+		//     return order;
+		// }
+		FactorEntry128[]? tempArray = pool.Rent(length + 1);
         try
         {
-            ReadOnlySpan<FactorEntry128> factorSpan = factors.Factors;
-            int length = factors.Count;
-            if (length == 0)
-            {
-                return order;
-            }
 
-            tempArray = ArrayPool<FactorEntry128>.Shared.Rent(length + 1);
             Span<FactorEntry128> buffer = tempArray.AsSpan(0, length);
             factorSpan.CopyTo(buffer);
 
@@ -198,14 +199,11 @@ internal static partial class PrimeOrderCalculator
         }
         finally
         {
-            if (tempArray is not null)
+			pool.Return(tempArray, clearArray: false);
-            {
-                ArrayPool<FactorEntry128>.Shared.Return(tempArray, clearArray: false);
-            }
         }
     }
 
-    private static bool TryConfirmOrderWide(UInt128 prime, UInt128 order, in MontgomeryDivisorData divisorData, PrimeOrderSearchConfig config)
+    private static bool TryConfirmOrderWide(in UInt128 prime, in UInt128 order, in MontgomeryDivisorData divisorData, in PrimeOrderSearchConfig config)
     {
         if (order == UInt128.Zero)
         {
@@ -263,11 +261,11 @@ internal static partial class PrimeOrderCalculator
     }
 
     private static bool TryHeuristicFinishWide(
-        UInt128 prime,
+        in UInt128 prime,
-        UInt128 order,
+        in UInt128 order,
-        UInt128? previousOrder,
+        in UInt128? previousOrder,
         in MontgomeryDivisorData divisorData,
-        PrimeOrderSearchConfig config,
+        in PrimeOrderSearchConfig config,
         out UInt128 result)
     {
         result = UInt128.Zero;
@@ -339,7 +337,7 @@ internal static partial class PrimeOrderCalculator
         return false;
     }
 
-    private static void SortCandidatesWide(UInt128 prime, UInt128? previousOrder, List<UInt128> candidates)
+    private static void SortCandidatesWide(UInt128 prime, in UInt128? previousOrder, List<UInt128> candidates)
     {
         UInt128 previous = previousOrder ?? UInt128.Zero;
         int previousGroup = previousOrder.HasValue ? GetGroupWide(previousOrder.Value, prime) : 1;
@@ -367,9 +365,9 @@ internal static partial class PrimeOrderCalculator
     }
 
     private static CandidateKey128 BuildKeyWide(
-        UInt128 value,
+        in UInt128 value,
-        UInt128 prime,
+        in UInt128 prime,
-        UInt128 previous,
+        in UInt128 previous,
         int previousGroup,
         bool hasPrevious)
     {
@@ -391,7 +389,7 @@ internal static partial class PrimeOrderCalculator
         return new CandidateKey128(primary, false, distance, false, value);
     }
 
-    private static int CompareComponents(bool descendingX, UInt128 valueX, bool descendingY, UInt128 valueY)
+    private static int CompareComponents(bool descendingX, in UInt128 valueX, bool descendingY, in UInt128 valueY)
     {
         if (descendingX == descendingY)
         {
@@ -416,7 +414,7 @@ internal static partial class PrimeOrderCalculator
         return valueX > valueY ? 1 : -1;
     }
 
-    private static int GetGroupWide(UInt128 value, UInt128 prime)
+    private static int GetGroupWide(in UInt128 value, in UInt128 prime)
     {
         UInt128 threshold1 = prime >> 3;
         if (value <= threshold1)
@@ -439,7 +437,7 @@ internal static partial class PrimeOrderCalculator
         return 0;
     }
 
-    private static void BuildCandidatesWide(UInt128 order, FactorEntry128[] factors, int count, List<UInt128> candidates, int limit)
+    private static void BuildCandidatesWide(in UInt128 order, FactorEntry128[] factors, int count, List<UInt128> candidates, int limit)
     {
         if (count == 0)
         {
@@ -452,10 +450,10 @@ internal static partial class PrimeOrderCalculator
     }
 
     private static void BuildCandidatesRecursiveWide(
-        UInt128 order,
+        in UInt128 order,
-        ReadOnlySpan<FactorEntry128> factors,
+        in ReadOnlySpan<FactorEntry128> factors,
         int index,
-        UInt128 divisorProduct,
+        in UInt128 divisorProduct,
         List<UInt128> candidates,
         int limit)
     {
@@ -511,7 +509,7 @@ internal static partial class PrimeOrderCalculator
         }
     }
 
-    private static bool TryConfirmCandidateWide(UInt128 prime, UInt128 candidate, PrimeOrderSearchConfig config, ref int powUsed, int powBudget, in MontgomeryDivisorData divisorData)
+    private static bool TryConfirmCandidateWide(in UInt128 prime, in UInt128 candidate, in PrimeOrderSearchConfig config, ref int powUsed, int powBudget, in MontgomeryDivisorData divisorData)
     {
         PartialFactorResult128 factorization = PartialFactorWide(candidate, config);
         if (factorization.Factors is null)
@@ -564,7 +562,7 @@ internal static partial class PrimeOrderCalculator
         return true;
     }
 
-    private static PartialFactorResult128 PartialFactorWide(UInt128 value, PrimeOrderSearchConfig config)
+    private static PartialFactorResult128 PartialFactorWide(in UInt128 value, in PrimeOrderSearchConfig config)
     {
         if (value <= UInt128.One)
         {
@@ -664,7 +662,8 @@ internal static partial class PrimeOrderCalculator
             return new PartialFactorResult128(null, value, false, 0);
         }
 
-        FactorEntry128[]? rented = counts.Count > 0 ? ArrayPool<FactorEntry128>.Shared.Rent(counts.Count) : null;
+		ArrayPool<FactorEntry128>? pool = null;
+		FactorEntry128[]? rented = counts.Count > 0 ?  (pool = ThreadStaticPools.FactorEntry128Pool).Rent(counts.Count) : null;
         int index = 0;
         if (rented is not null)
         {
@@ -676,20 +675,20 @@ internal static partial class PrimeOrderCalculator
         }
 
         FactorEntry128[]? resultArray = null;
-        if (rented is not null)
+        if (pool is not null)
         {
             Span<FactorEntry128> span = rented.AsSpan(0, index);
             span.Sort(static (a, b) => a.Value.CompareTo(b.Value));
             resultArray = new FactorEntry128[index];
             span.CopyTo(resultArray);
-            ArrayPool<FactorEntry128>.Shared.Return(rented, clearArray: false);
+            pool.Return(rented!, clearArray: false);
         }
 
         bool fullyFactored = cofactor == UInt128.One;
         return new PartialFactorResult128(resultArray, cofactor, fullyFactored, index);
     }
 
-    private static UInt128 PopulateSmallPrimeFactorsCpuWide(UInt128 value, uint limit, Dictionary<UInt128, int> counts)
+    private static UInt128 PopulateSmallPrimeFactorsCpuWide(in UInt128 value, uint limit, Dictionary<UInt128, int> counts)
     {
         UInt128 remaining = value;
         uint[] primes = PrimesGenerator.SmallPrimes;
@@ -729,7 +728,7 @@ internal static partial class PrimeOrderCalculator
 
         return remaining;
     }
-    private static bool TryPollardRhoWide(UInt128 n, Stopwatch stopwatch, long budgetTicks, out UInt128 factor)
+    private static bool TryPollardRhoWide(in UInt128 n, Stopwatch stopwatch, long budgetTicks, out UInt128 factor)
     {
         factor = UInt128.Zero;
         if ((n & UInt128.One) == UInt128.Zero)
@@ -771,7 +770,7 @@ internal static partial class PrimeOrderCalculator
         }
     }
 
-    private static UInt128 AdvancePolynomialWide(UInt128 x, UInt128 c, UInt128 modulus)
+    private static UInt128 AdvancePolynomialWide(in UInt128 x, in UInt128 c, in UInt128 modulus)
     {
         BigInteger value = (BigInteger)x;
         value = (value * value + (BigInteger)c) % (BigInteger)modulus;
@@ -809,7 +808,7 @@ internal static partial class PrimeOrderCalculator
         }
     }
 
-    private static int TrailingZeroCountWide(UInt128 value)
+    private static int TrailingZeroCountWide(in UInt128 value)
     {
         if (value == UInt128.Zero)
         {
@@ -865,7 +864,7 @@ internal static partial class PrimeOrderCalculator
         return order;
     }
 
-    private static void FactorCompletelyWide(UInt128 value, Dictionary<UInt128, int> counts)
+    private static void FactorCompletelyWide(in UInt128 value, Dictionary<UInt128, int> counts)
     {
         if (value <= UInt128.One)
         {
@@ -883,7 +882,7 @@ internal static partial class PrimeOrderCalculator
         FactorCompletelyWide(value / factor, counts);
     }
 
-    private static UInt128 PollardRhoWide(UInt128 n)
+    private static UInt128 PollardRhoWide(in UInt128 n)
     {
         if ((n & UInt128.One) == UInt128.Zero)
         {
@@ -916,7 +915,7 @@ internal static partial class PrimeOrderCalculator
         }
     }
 
-    private static bool IsPrimeWide(UInt128 value)
+    private static bool IsPrimeWide(in UInt128 value)
     {
         if (value <= ulong.MaxValue)
         {
@@ -996,7 +995,7 @@ internal static partial class PrimeOrderCalculator
         return true;
     }
 
-    private static UInt128 Pow2ModWide(UInt128 exponent, in UInt128 modulus, in MontgomeryDivisorData divisorData)
+    private static UInt128 Pow2ModWide(in UInt128 exponent, in UInt128 modulus, in MontgomeryDivisorData divisorData)
     {
         if (modulus == UInt128.One)
         {
@@ -1026,7 +1025,7 @@ internal static partial class PrimeOrderCalculator
         return exponent.Pow2MontgomeryModWindowed(modulus);
     }
 
-    private static void AddFactor(Dictionary<UInt128, int> counts, UInt128 prime, int exponent)
+    private static void AddFactor(Dictionary<UInt128, int> counts, in UInt128 prime, int exponent)
     {
         if (counts.TryGetValue(prime, out int existing))
         {
@@ -1038,60 +1037,30 @@ internal static partial class PrimeOrderCalculator
         }
     }
 
-    private readonly struct CandidateKey128
+    private readonly struct CandidateKey128(int primary, bool secondaryDescending, in UInt128 secondary, bool tertiaryDescending, in UInt128 tertiary)
-    {
+	{
-        public CandidateKey128(int primary, bool secondaryDescending, UInt128 secondary, bool tertiaryDescending, UInt128 tertiary)
+		public int Primary { get; } = primary;
-        {
-            Primary = primary;
-            SecondaryDescending = secondaryDescending;
-            Secondary = secondary;
-            TertiaryDescending = tertiaryDescending;
-            Tertiary = tertiary;
-        }
 
-        public int Primary { get; }
+		public bool SecondaryDescending { get; } = secondaryDescending;
 
-        public bool SecondaryDescending { get; }
+		public UInt128 Secondary { get; } = secondary;
 
-        public UInt128 Secondary { get; }
+		public bool TertiaryDescending { get; } = tertiaryDescending;
 
-        public bool TertiaryDescending { get; }
+		public UInt128 Tertiary { get; } = tertiary;
+	}
 
-        public UInt128 Tertiary { get; }
+    private readonly struct PartialFactorResult128(FactorEntry128[]? factors, UInt128 cofactor, bool fullyFactored, int count)
-    }
+	{
+		public FactorEntry128[]? Factors { get; } = factors;
 
-    private readonly struct FactorEntry128
+		public UInt128 Cofactor { get; } = cofactor;
-    {
-        public FactorEntry128(UInt128 value, int exponent)
-        {
-            Value = value;
-            Exponent = exponent;
-        }
 
-        public UInt128 Value { get; }
+		public bool FullyFactored { get; } = fullyFactored;
 
-        public int Exponent { get; }
+		public int Count { get; } = count;
-    }
 
-    private readonly struct PartialFactorResult128
+		public static PartialFactorResult128 Empty => new(null, UInt128.One, true, 0);
-    {
-        public PartialFactorResult128(FactorEntry128[]? factors, UInt128 cofactor, bool fullyFactored, int count)
-        {
-            Factors = factors;
-            Cofactor = cofactor;
-            FullyFactored = fullyFactored;
-            Count = count;
-        }
-
-        public FactorEntry128[]? Factors { get; }
-
-        public UInt128 Cofactor { get; }
-
-        public bool FullyFactored { get; }
-
-        public int Count { get; }
-
-        public static PartialFactorResult128 Empty => new(null, UInt128.One, true, 0);
 
         public PartialFactorResult128 WithAdditionalPrime(UInt128 prime)
         {

PerfectNumbers.Core/ThreadStaticPools.cs

@@ -0,0 +1,41 @@
+using System.Buffers;
+using System.Runtime.CompilerServices;
+
+namespace PerfectNumbers.Core
+{
+    public static class ThreadStaticPools
+    {
+		[ThreadStatic]
+		private static ArrayPool<FactorEntry>? _factorEntryPool;
+		public static ArrayPool<FactorEntry> FactorEntryPool
+		{
+			[MethodImpl(MethodImplOptions.AggressiveInlining)]
+			get
+			{
+				return _factorEntryPool ??= ArrayPool<FactorEntry>.Create();
+			}
+		}
+
+		[ThreadStatic]
+		private static ArrayPool<FactorEntry128>? _factorEntry128Pool;
+		public static ArrayPool<FactorEntry128> FactorEntry128Pool
+		{
+			[MethodImpl(MethodImplOptions.AggressiveInlining)]
+			get
+			{
+				return _factorEntry128Pool ??= ArrayPool<FactorEntry128>.Create();
+			}
+		}
+
+		[ThreadStatic]
+		private static ArrayPool<ulong>? _ulongPool;
+		public static ArrayPool<ulong> UlongPool
+		{
+			[MethodImpl(MethodImplOptions.AggressiveInlining)]
+			get
+			{
+				return _ulongPool ??= ArrayPool<ulong>.Create();
+			}
+		}
+	}
+}