1134 lines
36 KiB
C#
1134 lines
36 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Runtime.CompilerServices;
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namespace PerfectNumbers.Core.ByDivisor;
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/// <summary>
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/// Helper utilities for the BitContradiction divisor search. These methods implement the
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/// interval-based carry propagation described in the BitContradictions plan document.
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/// The solver itself will build on top of these primitives.
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/// </summary>
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internal static class BitContradictionSolverWithAMultiplier
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{
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private const int PingPongBlockColumns = 64;
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private const int TailCarryBatchColumns = 1024;
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private const int TailCarryBatchRepeats = 1;
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private const int ModLocalPrefilterMaxABits = 20;
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private static readonly int[] ModLocalPrefilterModuli = { 65537, 65521 };
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[ThreadStatic]
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private static TopDownPruneFailure? _lastTopDownFailure;
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private static bool _debugEnabled = true;
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private const int TopDownCacheCapacity = 16;
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private readonly struct TopDownCacheKey(long hash, int length, long maxAllowedA, long pLong)
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{
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public readonly long Hash = hash;
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public readonly int Length = length;
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public readonly long MaxAllowedA = maxAllowedA;
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public readonly long PLong = pLong;
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public bool Equals(TopDownCacheKey other) => Hash == other.Hash && Length == other.Length && MaxAllowedA == other.MaxAllowedA && PLong == other.PLong;
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public override bool Equals(object? obj) => obj is TopDownCacheKey other && Equals(other);
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public override int GetHashCode() => HashCode.Combine(Hash, Length, MaxAllowedA, PLong);
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}
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private readonly struct TopDownCacheValue(bool success, TopDownPruneFailure? failure)
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{
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public readonly bool Success = success;
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public readonly TopDownPruneFailure? Failure = failure;
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}
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[ThreadStatic]
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private static Dictionary<TopDownCacheKey, TopDownCacheValue>? _topDownCache;
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[ThreadStatic]
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private static List<TopDownCacheKey>? _topDownCacheOrder;
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private static long ComputeQOffsetsHash(ReadOnlySpan<int> qOneOffsets)
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{
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const long fnvOffset = unchecked((long)1469598103934665603);
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const long fnvPrime = 1099511628211;
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long hash = fnvOffset;
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for (int i = 0; i < qOneOffsets.Length; i++)
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{
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hash ^= qOneOffsets[i];
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hash *= fnvPrime;
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}
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return hash;
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}
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private static bool TryGetTopDownCache(in TopDownCacheKey key, out TopDownCacheValue value)
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{
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if (_topDownCache == null)
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{
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value = default;
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return false;
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}
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return _topDownCache.TryGetValue(key, out value);
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}
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private static void StoreTopDownCache(in TopDownCacheKey key, in TopDownCacheValue value)
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{
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_topDownCache ??= new Dictionary<TopDownCacheKey, TopDownCacheValue>();
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_topDownCacheOrder ??= new List<TopDownCacheKey>(TopDownCacheCapacity + 1);
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if (_topDownCache.ContainsKey(key))
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{
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_topDownCache[key] = value;
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return;
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}
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if (_topDownCacheOrder.Count >= TopDownCacheCapacity)
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{
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var evict = _topDownCacheOrder[0];
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_topDownCacheOrder.RemoveAt(0);
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_topDownCache.Remove(evict);
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}
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_topDownCache[key] = value;
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_topDownCacheOrder.Add(key);
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}
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private static int _parityZeroLogCount;
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internal static TopDownPruneFailure? LastTopDownFailure => _lastTopDownFailure;
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internal static void SetDebugEnabled(bool enabled) => _debugEnabled = enabled;
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internal static ColumnBounds ComputeColumnBounds(
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ReadOnlySpan<bool> multiplicand,
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ReadOnlySpan<bool> multiplier,
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int columnIndex)
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{
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long forced = 0;
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long possible = 0;
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int multiplicandLength = multiplicand.Length;
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int multiplierLength = multiplier.Length;
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for (int i = 0; i <= columnIndex; i++)
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{
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bool a = i < multiplicandLength && multiplicand[i];
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bool q = columnIndex - i < multiplierLength && multiplier[columnIndex - i];
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if (!a && !q)
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{
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continue;
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}
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if (a && q)
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{
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forced++;
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}
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possible++;
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}
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return new ColumnBounds(forced, possible);
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}
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internal static bool TryPropagateCarry(
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CarryRange currentCarry,
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long forcedOnes,
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long possibleOnes,
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int requiredResultBit,
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out CarryRange nextCarry,
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out ContradictionReason reason)
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{
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long minSum = currentCarry.Min + forcedOnes;
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long maxSum = currentCarry.Max + possibleOnes;
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int parity = requiredResultBit & 1;
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minSum = AlignUpToParity(minSum, parity);
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maxSum = AlignDownToParity(maxSum, parity);
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if (minSum > maxSum)
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{
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nextCarry = default;
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reason = ContradictionReason.ParityUnreachable;
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return false;
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}
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nextCarry = new CarryRange((minSum - requiredResultBit) >> 1, (maxSum - requiredResultBit) >> 1);
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reason = ContradictionReason.None;
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return true;
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}
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private static bool TryModularPrefilter(
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ReadOnlySpan<int> qOneOffsets,
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ulong p,
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long maxAllowedA)
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{
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if (maxAllowedA < 0 || maxAllowedA > ModLocalPrefilterMaxABits)
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{
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return true;
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}
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int bitCount = (int)(maxAllowedA + 1);
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if (bitCount <= 0 || bitCount >= 62)
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{
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return true;
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}
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long maxAValue = (1L << bitCount) - 1L;
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for (int i = 0; i < ModLocalPrefilterModuli.Length; i++)
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{
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int mod = ModLocalPrefilterModuli[i];
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int qMod = ComputeQMod(qOneOffsets, mod);
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int target = ModPow2Minus1(p, mod);
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if (qMod == 0)
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{
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if (target != 0)
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{
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return false;
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}
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continue;
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}
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int inverse = ModPow(qMod, mod - 2, mod);
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long x = (long)((long)target * inverse % mod);
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if (x > maxAValue)
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{
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return false;
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}
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}
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return true;
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}
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private static int ComputeQMod(ReadOnlySpan<int> qOneOffsets, int mod)
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{
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long sum = 0;
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for (int i = 0; i < qOneOffsets.Length; i++)
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{
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sum += PowMod2((ulong)qOneOffsets[i], mod);
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if (sum >= mod)
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{
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sum %= mod;
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}
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}
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return (int)(sum % mod);
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}
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private static int ModPow2Minus1(ulong p, int mod)
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{
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int pow = PowMod2(p, mod);
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int result = pow - 1;
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return result < 0 ? result + mod : result;
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}
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private static int PowMod2(ulong exp, int mod)
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{
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long result = 1 % mod;
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long baseVal = 2 % mod;
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ulong value = exp;
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while (value > 0)
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{
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if ((value & 1) != 0)
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{
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result = (result * baseVal) % mod;
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}
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baseVal = (baseVal * baseVal) % mod;
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value >>= 1;
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}
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return (int)result;
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}
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private static int ModPow(int value, int exp, int mod)
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{
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long result = 1 % mod;
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long baseVal = value % mod;
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int e = exp;
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while (e > 0)
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{
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if ((e & 1) != 0)
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{
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result = (result * baseVal) % mod;
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}
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baseVal = (baseVal * baseVal) % mod;
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e >>= 1;
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}
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return (int)result;
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}
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/// <summary>
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/// Full column-wise propagation for a given set of q one-bit offsets (LSB=0) and exponent p.
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/// Returns true if the solver could decide locally (divides or contradiction).
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/// </summary>
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internal static bool TryCheckDivisibilityFromOneOffsets(
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ReadOnlySpan<int> qOneOffsets,
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ulong p,
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out bool divides,
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out ContradictionReason reason)
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{
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divides = false;
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_lastTopDownFailure = null;
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// These conditions will never be true on EvenPerfectBitScanner execution path.
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// if (p == 0 || qOneOffsets.Length == 0)
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// {
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// reason = ContradictionReason.ParityUnreachable;
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// return true;
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// }
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// While the scanner supports p >= 31, it's a tiny subset of all checked exponents. No need to support it.
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// Exact small-case evaluation to short-circuit both success and failure deterministically.
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// int highestBit = qOneOffsets[^1];
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// if (p <= 64 && highestBit < 63)
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// {
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// ulong q = 0;
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// foreach (int bit in qOneOffsets)
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// {
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// q |= 1UL << bit;
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// }
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// ulong mersenne = (1UL << (int)p) - 1UL;
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// divides = q != 0 && (mersenne % q == 0);
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// reason = divides ? ContradictionReason.None : ContradictionReason.ParityUnreachable;
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// return true;
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// }
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int qOneOffsetsLength = qOneOffsets.Length;
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int maxOffset = qOneOffsets[qOneOffsetsLength - 1];
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if ((ulong)(maxOffset + 1) >= p)
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{
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reason = ContradictionReason.TruncatedLength;
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return true;
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}
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// q from EvenPerfectBitScanner will always have the correct 2kp+1 form.
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// if (qOneOffsets[0] != 0)
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// {
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// reason = ContradictionReason.ParityUnreachable;
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// return true;
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// }
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int windowSize = maxOffset + 1;
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var segmentState0 = new sbyte[windowSize];
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var segmentState1 = new sbyte[windowSize];
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long segmentBase = 0;
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long maxKnownA = -1L;
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long pLong = (long)p;
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long maxAllowedA = pLong - (maxOffset + 1L);
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if (maxAllowedA < 0)
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{
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reason = ContradictionReason.TruncatedLength;
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return true;
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}
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long topIndex0 = maxAllowedA;
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long topIndex1 = maxAllowedA - 1L;
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bool top0KnownOne = topIndex0 == 0L;
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bool top1KnownOne = topIndex1 == 0L;
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bool top0KnownZero = false;
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bool top1KnownZero = false;
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if (!TryModularPrefilter(qOneOffsets, p, maxAllowedA))
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{
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reason = ContradictionReason.ParityUnreachable;
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return true;
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}
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long qHash = ComputeQOffsetsHash(qOneOffsets);
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var cacheKey = new TopDownCacheKey(qHash, qOneOffsetsLength, maxAllowedA, pLong);
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if (TryGetTopDownCache(in cacheKey, out var cached))
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{
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_lastTopDownFailure = cached.Failure;
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if (!cached.Success)
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{
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reason = ContradictionReason.ParityUnreachable;
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return true;
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}
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}
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else
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{
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if (!TryTopDownCarryPrune(qOneOffsets, qOneOffsetsLength, pLong, maxAllowedA, out _lastTopDownFailure))
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{
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StoreTopDownCache(in cacheKey, new TopDownCacheValue(false, _lastTopDownFailure));
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reason = ContradictionReason.ParityUnreachable;
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return true;
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}
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StoreTopDownCache(in cacheKey, new TopDownCacheValue(true, null));
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}
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long lowColumn = 0;
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long highColumn = pLong - 1;
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CarryRange carryLow = CarryRange.Zero;
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CarryRange carryHigh = CarryRange.Zero;
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int bottomWindowStart = 0;
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int bottomWindowEnd = 0;
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int topWindowStart = qOneOffsetsLength;
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int topWindowEnd = qOneOffsetsLength;
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bool processTop = true;
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while (lowColumn <= highColumn)
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{
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int remaining = (int)(highColumn - lowColumn + 1);
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int blockSize = remaining < PingPongBlockColumns ? remaining : PingPongBlockColumns;
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if (processTop)
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{
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if (!TryProcessTopDownBlock(qOneOffsets, qOneOffsetsLength, maxAllowedA, highColumn, blockSize, carryHigh, ref topWindowStart, ref topWindowEnd, out carryHigh, out _lastTopDownFailure))
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{
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reason = ContradictionReason.ParityUnreachable;
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return true;
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}
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highColumn -= blockSize;
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}
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else
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{
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if (!TryProcessBottomUpBlock(qOneOffsets, maxAllowedA, lowColumn, blockSize, ref carryLow, ref maxKnownA, ref segmentBase, ref bottomWindowStart, ref bottomWindowEnd, segmentState0, segmentState1, topIndex0, topIndex1, ref top0KnownOne, ref top1KnownOne, ref top0KnownZero, ref top1KnownZero, out reason))
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{
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return true;
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}
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lowColumn += blockSize;
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}
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processTop = !processTop;
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}
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long carryMin = carryLow.Min > carryHigh.Min ? carryLow.Min : carryHigh.Min;
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long carryMax = carryLow.Max < carryHigh.Max ? carryLow.Max : carryHigh.Max;
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if (carryMin > carryMax)
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{
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divides = false;
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reason = ContradictionReason.ParityUnreachable;
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return true;
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}
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divides = true;
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reason = ContradictionReason.None;
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return true;
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}
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internal static bool TryCheckDivisibilityFromOneOffsets(
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ReadOnlySpan<int> qOneOffsets,
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ulong p,
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out bool divides) => TryCheckDivisibilityFromOneOffsets(qOneOffsets, p, out divides, out _);
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[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
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private static bool TryAdvanceZeroColumns(ref CarryRange carry, int columnCount)
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{
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long carryMin = carry.Min;
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long carryMax = carry.Max;
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while (columnCount > 0)
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{
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int step = columnCount > 62 ? 62 : columnCount;
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long add = (1L << step) - 1L;
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long nextMin = (carryMin + add) >> step;
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long nextMax = carryMax >> step;
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if (nextMin > nextMax)
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{
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return false;
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}
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carryMin = nextMin;
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carryMax = nextMax;
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columnCount -= step;
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}
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carry = new CarryRange(carryMin, carryMax);
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return true;
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}
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[ThreadStatic]
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private static Dictionary<int, int[]>? _stableUnknownDelta8;
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private static int[] GetStableUnknownDelta8(int unknown)
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{
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_stableUnknownDelta8 ??= new Dictionary<int, int[]>();
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if (_stableUnknownDelta8.TryGetValue(unknown, out int[]? cached))
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{
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return cached;
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}
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int[] delta = new int[256];
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for (int low = 0; low < 256; low++)
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{
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long value = low;
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for (int i = 0; i < 8; i++)
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{
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int sMax = (((unknown ^ (int)value) & 1) != 0) ? unknown : unknown - 1;
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value = (value + sMax - 1) >> 1;
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}
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delta[low] = (int)((value << 8) - low);
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}
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_stableUnknownDelta8[unknown] = delta;
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return delta;
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}
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private static bool TryAdvanceStableUnknown(ref CarryRange carry, int unknown, int columnCount, out ContradictionReason reason)
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{
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if (columnCount <= 0)
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{
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reason = ContradictionReason.None;
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return true;
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}
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if (unknown <= 0)
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{
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if (!TryAdvanceZeroColumns(ref carry, columnCount))
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{
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reason = ContradictionReason.ParityUnreachable;
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return false;
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}
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reason = ContradictionReason.None;
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return true;
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}
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long carryMin = carry.Min >> columnCount;
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long carryMax = carry.Max;
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int remaining = columnCount;
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int[] delta = GetStableUnknownDelta8(unknown);
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while (remaining >= 8)
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{
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int low = (int)(carryMax & 255);
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carryMax = (carryMax + delta[low]) >> 8;
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remaining -= 8;
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}
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while (remaining > 0)
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{
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int sMax = (((unknown ^ (int)carryMax) & 1) != 0) ? unknown : unknown - 1;
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carryMax = (carryMax + sMax - 1) >> 1;
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remaining--;
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}
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if (carryMax < carryMin)
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{
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reason = ContradictionReason.ParityUnreachable;
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return false;
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}
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carry = new CarryRange(carryMin, carryMax);
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reason = ContradictionReason.None;
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return true;
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}
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private static bool TryProcessBottomUpBlock(
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ReadOnlySpan<int> qOneOffsets,
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long maxAllowedA,
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long startColumn,
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int columnCount,
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ref CarryRange carry,
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ref long maxKnownA,
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ref long segmentBase,
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ref int windowStartIdx,
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ref int windowEndIdx,
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sbyte[] segmentState0,
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sbyte[] segmentState1,
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long topIndex0,
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long topIndex1,
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ref bool top0KnownOne,
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ref bool top1KnownOne,
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ref bool top0KnownZero,
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ref bool top1KnownZero,
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out ContradictionReason reason)
|
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{
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long endColumn = startColumn + columnCount;
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int qOneOffsetsLength = qOneOffsets.Length;
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int windowSize = segmentState0.Length;
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int maxOffset = qOneOffsets[qOneOffsetsLength - 1];
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long stableUnknown = qOneOffsetsLength;
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long column = startColumn;
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while (column < endColumn)
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{
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if (column >= maxOffset && column <= maxAllowedA && maxKnownA < column - maxOffset)
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{
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long batchEnd = endColumn - 1;
|
|
if (batchEnd > maxAllowedA)
|
|
{
|
|
batchEnd = maxAllowedA;
|
|
}
|
|
|
|
long remaining = batchEnd - column + 1;
|
|
if (remaining > 0)
|
|
{
|
|
windowStartIdx = 0;
|
|
windowEndIdx = qOneOffsetsLength;
|
|
while (remaining > 0)
|
|
{
|
|
int step = remaining > TailCarryBatchColumns ? TailCarryBatchColumns : (int)remaining;
|
|
if (!TryAdvanceStableUnknown(ref carry, (int)stableUnknown, step, out var propagateReason))
|
|
{
|
|
reason = propagateReason;
|
|
return false;
|
|
}
|
|
|
|
column += step;
|
|
remaining -= step;
|
|
}
|
|
|
|
long batchBase = (column / windowSize) * windowSize;
|
|
if (batchBase != segmentBase)
|
|
{
|
|
Array.Clear(segmentState0);
|
|
Array.Clear(segmentState1);
|
|
segmentBase = batchBase;
|
|
}
|
|
|
|
continue;
|
|
}
|
|
}
|
|
long forced = 0L;
|
|
long unknown = 0L;
|
|
long chosenIndex = -1L;
|
|
long newBase = (column / windowSize) * windowSize;
|
|
if (newBase != segmentBase)
|
|
{
|
|
if (newBase == segmentBase + windowSize)
|
|
{
|
|
(segmentState0, segmentState1) = (segmentState1, segmentState0);
|
|
Array.Clear(segmentState0);
|
|
}
|
|
else
|
|
{
|
|
Array.Clear(segmentState0);
|
|
Array.Clear(segmentState1);
|
|
}
|
|
|
|
segmentBase = newBase;
|
|
}
|
|
|
|
while (windowEndIdx < qOneOffsetsLength && qOneOffsets[windowEndIdx] <= column)
|
|
{
|
|
windowEndIdx++;
|
|
}
|
|
|
|
long lowerBound = column - maxAllowedA;
|
|
while (windowStartIdx < windowEndIdx && qOneOffsets[windowStartIdx] < lowerBound)
|
|
{
|
|
windowStartIdx++;
|
|
}
|
|
|
|
for (int offsetIndex = windowStartIdx; offsetIndex < windowEndIdx; offsetIndex++)
|
|
{
|
|
int offset = qOneOffsets[offsetIndex];
|
|
long aIndex = column - offset;
|
|
if (aIndex < 0)
|
|
{
|
|
break;
|
|
}
|
|
|
|
if (aIndex > maxAllowedA)
|
|
{
|
|
continue; // a must be zero here
|
|
}
|
|
|
|
if (aIndex >= segmentBase)
|
|
{
|
|
int slot = (int)(aIndex - segmentBase);
|
|
sbyte state = segmentState0[slot];
|
|
if (state == 1)
|
|
{
|
|
forced++;
|
|
}
|
|
else if (state == 0)
|
|
{
|
|
unknown++;
|
|
if (chosenIndex == -1L)
|
|
{
|
|
chosenIndex = aIndex;
|
|
}
|
|
}
|
|
}
|
|
else if (aIndex >= segmentBase - windowSize)
|
|
{
|
|
int slot = (int)(aIndex - (segmentBase - windowSize));
|
|
sbyte state = segmentState1[slot];
|
|
if (state == 1)
|
|
{
|
|
forced++;
|
|
}
|
|
else if (state == 0)
|
|
{
|
|
unknown++;
|
|
if (chosenIndex == -1L)
|
|
{
|
|
chosenIndex = aIndex;
|
|
}
|
|
}
|
|
}
|
|
else
|
|
{
|
|
unknown++;
|
|
if (chosenIndex == -1L)
|
|
{
|
|
chosenIndex = aIndex;
|
|
}
|
|
}
|
|
}
|
|
|
|
long minSum = carry.Min;
|
|
long maxSum = carry.Max;
|
|
if (unknown == 1 && ((minSum ^ maxSum) & 1) == 0)
|
|
{
|
|
int requiredUnknownParity = 1 ^ ((int)minSum & 1) ^ ((int)forced & 1);
|
|
if (requiredUnknownParity != 0)
|
|
{
|
|
if (chosenIndex >= 0)
|
|
{
|
|
if (chosenIndex >= segmentBase)
|
|
{
|
|
int slot = (int)(chosenIndex - segmentBase);
|
|
segmentState0[slot] = 1;
|
|
}
|
|
else
|
|
{
|
|
int slot = (int)(chosenIndex - (segmentBase - windowSize));
|
|
segmentState1[slot] = 1;
|
|
}
|
|
forced++;
|
|
unknown = 0;
|
|
if (chosenIndex > maxKnownA)
|
|
{
|
|
maxKnownA = chosenIndex;
|
|
}
|
|
if (chosenIndex == topIndex0)
|
|
{
|
|
if (top0KnownZero)
|
|
{
|
|
reason = ContradictionReason.ParityUnreachable;
|
|
return false;
|
|
}
|
|
|
|
top0KnownOne = true;
|
|
}
|
|
else if (chosenIndex == topIndex1)
|
|
{
|
|
if (top1KnownZero)
|
|
{
|
|
reason = ContradictionReason.ParityUnreachable;
|
|
return false;
|
|
}
|
|
|
|
top1KnownOne = true;
|
|
}
|
|
}
|
|
}
|
|
else
|
|
{
|
|
// if (_debugEnabled && _parityZeroLogCount < 8)
|
|
// {
|
|
// _parityZeroLogCount++;
|
|
// Console.WriteLine($"[bit-contradiction] unknown==1 parity forces zero at column={column} carry=[{minSum},{maxSum}] forced={forced} chosenIndex={chosenIndex}");
|
|
// }
|
|
|
|
// Treat the single unknown as 0 for parity.
|
|
unknown = 0;
|
|
|
|
if (chosenIndex == topIndex0)
|
|
{
|
|
if (top0KnownOne)
|
|
{
|
|
reason = ContradictionReason.ParityUnreachable;
|
|
return false;
|
|
}
|
|
|
|
top0KnownZero = true;
|
|
}
|
|
else if (chosenIndex == topIndex1)
|
|
{
|
|
if (top1KnownOne)
|
|
{
|
|
reason = ContradictionReason.ParityUnreachable;
|
|
return false;
|
|
}
|
|
|
|
top1KnownZero = true;
|
|
}
|
|
}
|
|
}
|
|
|
|
if ((top0KnownZero && top0KnownOne) || (top1KnownZero && top1KnownOne))
|
|
{
|
|
reason = ContradictionReason.ParityUnreachable;
|
|
return false;
|
|
}
|
|
|
|
if (topIndex1 < 0)
|
|
{
|
|
if (top0KnownZero)
|
|
{
|
|
reason = ContradictionReason.ParityUnreachable;
|
|
return false;
|
|
}
|
|
}
|
|
else if (top0KnownZero && top1KnownZero)
|
|
{
|
|
reason = ContradictionReason.ParityUnreachable;
|
|
return false;
|
|
}
|
|
|
|
if (unknown == 0)
|
|
{
|
|
int requiredCarryParity = 1 ^ ((int)forced & 1);
|
|
long carryMin = AlignUpToParity(carry.Min, requiredCarryParity);
|
|
long carryMax = AlignDownToParity(carry.Max, requiredCarryParity);
|
|
if (carryMin > carryMax)
|
|
{
|
|
reason = ContradictionReason.ParityUnreachable;
|
|
return false;
|
|
}
|
|
|
|
carry = new CarryRange(carryMin, carryMax);
|
|
minSum = carry.Min;
|
|
maxSum = carry.Max;
|
|
}
|
|
|
|
minSum += forced;
|
|
maxSum += forced + unknown;
|
|
const int requiredParity = 1;
|
|
|
|
if (minSum == maxSum)
|
|
{
|
|
if ((minSum & 1) != requiredParity)
|
|
{
|
|
reason = ContradictionReason.ParityUnreachable;
|
|
return false;
|
|
}
|
|
|
|
long nextCarry = (minSum - requiredParity) >> 1;
|
|
carry = CarryRange.Single(nextCarry);
|
|
}
|
|
else
|
|
{
|
|
if ((minSum & 1) != requiredParity && unknown == 0)
|
|
{
|
|
reason = ContradictionReason.ParityUnreachable;
|
|
return false;
|
|
}
|
|
|
|
if (!TryPropagateCarry(
|
|
carry,
|
|
forced,
|
|
forced + unknown,
|
|
requiredParity,
|
|
out var next,
|
|
out var propagateReason))
|
|
{
|
|
reason = propagateReason;
|
|
return false;
|
|
}
|
|
|
|
carry = next;
|
|
}
|
|
|
|
column++;
|
|
}
|
|
|
|
reason = ContradictionReason.None;
|
|
return true;
|
|
}
|
|
|
|
private static bool TryProcessTopDownBlock(
|
|
ReadOnlySpan<int> qOneOffsets,
|
|
int qOneOffsetsLength,
|
|
long maxAllowedA,
|
|
long startHighColumn,
|
|
int columnCount,
|
|
CarryRange carryOut,
|
|
ref int windowStart,
|
|
ref int windowEnd,
|
|
out CarryRange nextCarryOut,
|
|
out TopDownPruneFailure? failure)
|
|
{
|
|
failure = null;
|
|
long carryOutMin = carryOut.Min,
|
|
carryOutMax = carryOut.Max,
|
|
value;
|
|
long endColumn = startHighColumn - columnCount + 1;
|
|
|
|
long column = startHighColumn;
|
|
while (column >= endColumn)
|
|
{
|
|
// value is used as high column index
|
|
value = column;
|
|
while (windowEnd > 0 && qOneOffsets[windowEnd - 1] > value)
|
|
{
|
|
windowEnd--;
|
|
}
|
|
|
|
// value is used as low column index
|
|
value = column - maxAllowedA;
|
|
if (value < 0)
|
|
{
|
|
value = 0;
|
|
}
|
|
|
|
while (windowStart > 0 && qOneOffsets[windowStart - 1] >= value)
|
|
{
|
|
windowStart--;
|
|
}
|
|
|
|
if (windowStart > windowEnd)
|
|
{
|
|
windowStart = windowEnd;
|
|
}
|
|
|
|
// value is unknown bits count here
|
|
value = windowEnd - windowStart;
|
|
if (value == 0)
|
|
{
|
|
long lastEnd = windowEnd > 0 ? qOneOffsets[windowEnd - 1] : long.MinValue;
|
|
long lastStart = windowStart > 0 ? qOneOffsets[windowStart - 1] + maxAllowedA : long.MinValue;
|
|
long chunkEnd = lastEnd > lastStart ? lastEnd : lastStart;
|
|
if (chunkEnd < endColumn)
|
|
{
|
|
chunkEnd = endColumn;
|
|
}
|
|
|
|
int steps = (int)(column - chunkEnd + 1);
|
|
if (steps > 1)
|
|
{
|
|
if (!AdvanceTopDownUnknown0(ref carryOutMin, ref carryOutMax, steps))
|
|
{
|
|
failure = new TopDownPruneFailure(column, carryOutMin, carryOutMax, value);
|
|
nextCarryOut = default;
|
|
return false;
|
|
}
|
|
|
|
column = chunkEnd - 1;
|
|
continue;
|
|
}
|
|
}
|
|
else if (value == 1)
|
|
{
|
|
long lastEnd = windowEnd > 0 ? qOneOffsets[windowEnd - 1] : long.MinValue;
|
|
long lastStart = windowStart > 0 ? qOneOffsets[windowStart - 1] + maxAllowedA : long.MinValue;
|
|
long chunkEnd = lastEnd > lastStart ? lastEnd : lastStart;
|
|
if (chunkEnd < endColumn)
|
|
{
|
|
chunkEnd = endColumn;
|
|
}
|
|
|
|
int steps = (int)(column - chunkEnd + 1);
|
|
if (steps > 1)
|
|
{
|
|
if (!AdvanceTopDownUnknown1(ref carryOutMin, ref carryOutMax, steps))
|
|
{
|
|
failure = new TopDownPruneFailure(column, carryOutMin, carryOutMax, value);
|
|
nextCarryOut = default;
|
|
return false;
|
|
}
|
|
|
|
column = chunkEnd - 1;
|
|
continue;
|
|
}
|
|
}
|
|
|
|
// carryOutMin now becomes nextCarryMin to limit registry pressure
|
|
carryOutMin = (carryOutMin << 1) + 1 - value;
|
|
// carryOutMax now becomes nextCarryMax to limit registry pressure
|
|
carryOutMax = (carryOutMax << 1) + 1;
|
|
if (carryOutMin < 0)
|
|
{
|
|
carryOutMin = 0;
|
|
}
|
|
|
|
if (carryOutMax < 0)
|
|
{
|
|
carryOutMax = 0;
|
|
}
|
|
|
|
if (carryOutMin > carryOutMax)
|
|
{
|
|
failure = new TopDownPruneFailure(column, carryOutMin, carryOutMax, value);
|
|
nextCarryOut = default;
|
|
return false;
|
|
}
|
|
|
|
column--;
|
|
}
|
|
|
|
nextCarryOut = new CarryRange(carryOutMin, carryOutMax);
|
|
return true;
|
|
}
|
|
|
|
private static long AlignUpToParity(long value, int parity) => (value & 1) == parity ? value : value + 1;
|
|
|
|
private static long AlignDownToParity(long value, int parity) => (value & 1) == parity ? value : value - 1;
|
|
|
|
private static bool TryTopDownCarryPrune(
|
|
ReadOnlySpan<int> qOneOffsets,
|
|
int qOneOffsetsLength,
|
|
long pLong,
|
|
long maxAllowedA,
|
|
out TopDownPruneFailure? failure)
|
|
{
|
|
failure = null;
|
|
int windowStart = qOneOffsetsLength;
|
|
int windowEnd = qOneOffsetsLength;
|
|
long carryOutMin = 0,
|
|
carryOutMax = 0,
|
|
value;
|
|
|
|
long column = pLong - 1;
|
|
while (column >= 0)
|
|
{
|
|
// value is used as high column index
|
|
value = column;
|
|
while (windowEnd > 0 && qOneOffsets[windowEnd - 1] > value)
|
|
{
|
|
windowEnd--;
|
|
}
|
|
|
|
// value is used as low column index
|
|
value = column - maxAllowedA;
|
|
if (value < 0)
|
|
{
|
|
value = 0;
|
|
}
|
|
|
|
while (windowStart > 0 && qOneOffsets[windowStart - 1] >= value)
|
|
{
|
|
windowStart--;
|
|
}
|
|
|
|
if (windowStart > windowEnd)
|
|
{
|
|
windowStart = windowEnd;
|
|
}
|
|
|
|
// value is used as unknown bits count here
|
|
value = windowEnd - windowStart;
|
|
if (value == 0)
|
|
{
|
|
long lastEnd = windowEnd > 0 ? qOneOffsets[windowEnd - 1] : long.MinValue;
|
|
long lastStart = windowStart > 0 ? qOneOffsets[windowStart - 1] + maxAllowedA : long.MinValue;
|
|
long chunkEnd = lastEnd > lastStart ? lastEnd : lastStart;
|
|
if (chunkEnd < 0)
|
|
{
|
|
chunkEnd = 0;
|
|
}
|
|
|
|
int steps = (int)(column - chunkEnd + 1);
|
|
if (steps > 1)
|
|
{
|
|
if (!AdvanceTopDownUnknown0(ref carryOutMin, ref carryOutMax, steps))
|
|
{
|
|
failure = new TopDownPruneFailure(column, carryOutMin, carryOutMax, value);
|
|
return false;
|
|
}
|
|
|
|
column = chunkEnd - 1;
|
|
continue;
|
|
}
|
|
}
|
|
else if (value == 1)
|
|
{
|
|
long lastEnd = windowEnd > 0 ? qOneOffsets[windowEnd - 1] : long.MinValue;
|
|
long lastStart = windowStart > 0 ? qOneOffsets[windowStart - 1] + maxAllowedA : long.MinValue;
|
|
long chunkEnd = lastEnd > lastStart ? lastEnd : lastStart;
|
|
if (chunkEnd < 0)
|
|
{
|
|
chunkEnd = 0;
|
|
}
|
|
|
|
int steps = (int)(column - chunkEnd + 1);
|
|
if (steps > 1)
|
|
{
|
|
if (!AdvanceTopDownUnknown1(ref carryOutMin, ref carryOutMax, steps))
|
|
{
|
|
failure = new TopDownPruneFailure(column, carryOutMin, carryOutMax, value);
|
|
return false;
|
|
}
|
|
|
|
column = chunkEnd - 1;
|
|
continue;
|
|
}
|
|
}
|
|
|
|
// carryOutMin now becomes nextCarryMin to limit registry pressure
|
|
carryOutMin = (carryOutMin << 1) + 1 - value;
|
|
// carryOutMax now becomes nextCarryMax to limit registry pressure
|
|
carryOutMax = (carryOutMax << 1) + 1;
|
|
if (carryOutMin < 0)
|
|
{
|
|
carryOutMin = 0;
|
|
}
|
|
|
|
if (carryOutMax < 0)
|
|
{
|
|
carryOutMax = 0;
|
|
}
|
|
|
|
if (carryOutMin > carryOutMax)
|
|
{
|
|
failure = new TopDownPruneFailure(column, carryOutMin, carryOutMax, value);
|
|
return false;
|
|
}
|
|
|
|
column--;
|
|
}
|
|
|
|
if (carryOutMin > 0)
|
|
{
|
|
failure = new TopDownPruneFailure(0, carryOutMin, carryOutMax, 0);
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
private static bool AdvanceTopDownUnknown1(ref long carryOutMin, ref long carryOutMax, int steps)
|
|
{
|
|
while (steps > 0)
|
|
{
|
|
int step = steps > 62 ? 62 : steps;
|
|
long pow = 1L << step;
|
|
|
|
if (carryOutMin > (long.MaxValue >> step) || carryOutMax > ((long.MaxValue - (pow - 1)) >> step))
|
|
{
|
|
carryOutMin = 0;
|
|
carryOutMax = long.MaxValue;
|
|
return true;
|
|
}
|
|
|
|
carryOutMin <<= step;
|
|
carryOutMax = (carryOutMax << step) + (pow - 1);
|
|
steps -= step;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
private static bool AdvanceTopDownUnknown0(ref long carryOutMin, ref long carryOutMax, int steps)
|
|
{
|
|
while (steps > 0)
|
|
{
|
|
int step = steps > 62 ? 62 : steps;
|
|
long add = (1L << step) - 1L;
|
|
if (carryOutMin > ((long.MaxValue - add) >> step) || carryOutMax > ((long.MaxValue - add) >> step))
|
|
{
|
|
carryOutMin = 0;
|
|
carryOutMax = long.MaxValue;
|
|
return true;
|
|
}
|
|
|
|
carryOutMin = (carryOutMin << step) + add;
|
|
carryOutMax = (carryOutMax << step) + add;
|
|
steps -= step;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
}
|