Use stack buffers for CPU exponent lowering and add MutableUInt128
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Marek Lemańczyk committed
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@@ -0,0 +1,108 @@
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using System;
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using System.Numerics;
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namespace PerfectNumbers.Core;
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/// <summary>
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/// Mutable helper for 128-bit arithmetic derived from the .NET runtime UInt128 implementation.
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/// Portions adapted from https://github.com/dotnet/runtime/blob/v8.0.0/src/libraries/System.Private.CoreLib/src/System/UInt128.cs.
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/// </summary>
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internal sealed class MutableUInt128
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{
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public ulong High { get; private set; }
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public ulong Low { get; private set; }
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public MutableUInt128()
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{
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}
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public MutableUInt128(ulong value)
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{
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Low = value;
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}
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public MutableUInt128(ulong high, ulong low)
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{
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High = high;
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Low = low;
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}
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public MutableUInt128(UInt128 value)
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{
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Set(value);
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}
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public void Set(UInt128 value)
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{
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High = (ulong)(value >> 64);
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Low = (ulong)value;
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}
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public void Set(ulong high, ulong low)
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{
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High = high;
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Low = low;
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}
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public UInt128 ToUInt128() => ((UInt128)High << 64) | Low;
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public void Add(ulong value)
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{
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ulong low = Low + value;
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if (low < value)
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{
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High++;
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}
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Low = low;
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}
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public void Add(in MutableUInt128 value)
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{
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ulong low = Low + value.Low;
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ulong carry = low < Low ? 1UL : 0UL;
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ulong high = High + value.High + carry;
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Low = low;
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High = high;
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}
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public void Subtract(ulong value)
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{
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ulong low = Low;
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ulong result = low - value;
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ulong borrow = result > low ? 1UL : 0UL;
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Low = result;
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High -= borrow;
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}
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public void Subtract(in MutableUInt128 value)
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{
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ulong low = Low;
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ulong result = low - value.Low;
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ulong borrow = low < value.Low ? 1UL : 0UL;
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Low = result;
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High = High - value.High - borrow;
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}
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public void Multiply(ulong value)
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{
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ulong high = High;
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ulong low = Low;
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ulong highContribution = Math.BigMul(low, value, out ulong newLow);
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Math.BigMul(high, value, out ulong shiftedHigh);
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ulong newHigh = shiftedHigh + highContribution;
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Low = newLow;
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High = newHigh;
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}
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public void MultiplyAdd(ulong multiplier, ulong addend)
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{
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Multiply(multiplier);
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Add(addend);
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}
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}
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@@ -314,69 +314,84 @@ internal static partial class PrimeOrderCalculator
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return order;
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}
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[ThreadStatic]
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private static ArrayPool<FactorEntry>? _factorPool;
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private static ArrayPool<FactorEntry> FactorPool => _factorPool ??= ArrayPool<FactorEntry>.Create();
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[ThreadStatic]
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private static ArrayPool<FactorEntry>? _factorPool;
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private static ArrayPool<FactorEntry> FactorPool => _factorPool ??= ArrayPool<FactorEntry>.Create();
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[ThreadStatic]
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private static ArrayPool<ulong>? _ulongPool;
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private static ArrayPool<ulong> ULongPool => _ulongPool ??= ArrayPool<ulong>.Create();
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private const int FactorEntryStackThreshold = 32;
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private static ulong ExponentLoweringCpu(ulong order, ulong prime, PartialFactorResult factors, in MontgomeryDivisorData divisorData)
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{
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ArrayPool<FactorEntry> factorPool = FactorPool;
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[ThreadStatic]
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private static ArrayPool<ulong>? _ulongPool;
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private static ArrayPool<ulong> ULongPool => _ulongPool ??= ArrayPool<ulong>.Create();
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FactorEntry[]? tempArray = null;
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try
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{
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ReadOnlySpan<FactorEntry> factorSpan = factors.Factors;
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int length = factors.Count;
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tempArray = factorPool.Rent(length + 1);
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Span<FactorEntry> buffer = tempArray;
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factorSpan.CopyTo(buffer);
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private static ulong ExponentLoweringCpu(ulong order, ulong prime, PartialFactorResult factors, in MontgomeryDivisorData divisorData)
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{
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ArrayPool<FactorEntry> factorPool = FactorPool;
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bool isPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(factors.Cofactor);
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// bool isPrime = PrimeTester.IsPrimeInternal(factors.Cofactor, CancellationToken.None);
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if (!factors.FullyFactored && factors.Cofactor > 1UL && isPrime)
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{
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buffer[length] = new FactorEntry(factors.Cofactor);
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length++;
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}
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FactorEntry[]? tempArray = null;
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try
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{
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ReadOnlySpan<FactorEntry> factorSpan = factors.Factors;
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int length = factors.Count;
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int capacity = length + 1;
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buffer.Slice(0, length).Sort(static (a, b) => a.Value.CompareTo(b.Value));
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Span<FactorEntry> buffer;
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if (capacity <= FactorEntryStackThreshold)
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{
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buffer = stackalloc FactorEntry[capacity];
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}
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else
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{
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tempArray = factorPool.Rent(capacity);
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buffer = tempArray.AsSpan(0, capacity);
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}
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for (int i = 0; i < length; i++)
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{
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ulong primeFactor = buffer[i].Value;
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int exponent = buffer[i].Exponent;
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for (int iteration = 0; iteration < exponent; iteration++)
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{
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if ((order % primeFactor) != 0UL)
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{
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break;
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}
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factorSpan.CopyTo(buffer);
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ulong reduced = order / primeFactor;
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if (Pow2EqualsOneCpu(reduced, prime, divisorData))
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{
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order = reduced;
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continue;
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}
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bool isPrime = Open.Numeric.Primes.Prime.Numbers.IsPrime(factors.Cofactor);
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// bool isPrime = PrimeTester.IsPrimeInternal(factors.Cofactor, CancellationToken.None);
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if (!factors.FullyFactored && factors.Cofactor > 1UL && isPrime)
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{
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buffer[length] = new FactorEntry(factors.Cofactor);
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length++;
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}
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break;
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}
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}
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buffer = buffer.Slice(0, length); // Reuse the same span restricted to populated entries.
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buffer.Sort(static (a, b) => a.Value.CompareTo(b.Value));
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return order;
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}
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finally
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{
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if (tempArray is not null)
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{
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factorPool.Return(tempArray, clearArray: false);
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}
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}
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}
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for (int i = 0; i < buffer.Length; i++)
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{
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FactorEntry entry = buffer[i];
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ulong primeFactor = entry.Value;
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int exponent = entry.Exponent;
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for (int iteration = 0; iteration < exponent; iteration++)
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{
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if ((order % primeFactor) != 0UL)
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{
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break;
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}
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ulong reduced = order / primeFactor;
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if (Pow2EqualsOneCpu(reduced, prime, divisorData))
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{
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order = reduced;
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continue;
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}
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break;
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}
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}
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return order;
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}
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finally
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{
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if (tempArray is not null)
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{
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factorPool.Return(tempArray, clearArray: false);
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}
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}
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}
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private static bool TryConfirmOrderCpu(ulong prime, ulong order, in MontgomeryDivisorData divisorData, ref PartialFactorResult orderFactors)
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{
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