Filter disallowed divisors when scanning by divisor
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Marek Lemańczyk committed
1 parent
5b2995c8a5
commit
c28e36cbe5
1 file changed
+98
-57
@@ -1014,72 +1014,113 @@ internal static class Program
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private static void RunByDivisorMode(List<ulong> primes, ulong divisorCyclesSearchLimit, int threadCount) => ByDivisorScanner.Run(primes, divisorCyclesSearchLimit, threadCount);
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private static ulong AcquireNextDivisor(ref ulong nextDivisor, ulong divisorLimit, ref int divisorsExhaustedFlag, ref long finalDivisorBits, out bool exhausted, ref ulong localDivisorCursor, ref int localDivisorsRemaining)
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{
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ref long nextDivisorBits = ref Unsafe.As<ulong, long>(ref nextDivisor);
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ulong blockStride = unchecked(DivisorAllocationBlockSize * 2);
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private static ulong AcquireNextDivisor(ref ulong nextDivisor, ulong divisorLimit, ref int divisorsExhaustedFlag, ref long finalDivisorBits, out bool exhausted, ref ulong localDivisorCursor, ref int localDivisorsRemaining)
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{
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ref long nextDivisorBits = ref Unsafe.As<ulong, long>(ref nextDivisor);
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ulong blockStride = unchecked(DivisorAllocationBlockSize * 2);
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if (localDivisorsRemaining > 0)
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{
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ulong currentValue = localDivisorCursor;
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localDivisorCursor += 2UL;
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localDivisorsRemaining--;
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exhausted = false;
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return currentValue;
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}
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if (TryAcquireLocalDivisor(ref localDivisorCursor, ref localDivisorsRemaining, out ulong localDivisor))
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{
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exhausted = false;
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return localDivisor;
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}
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while (true)
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{
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if (Volatile.Read(ref divisorsExhaustedFlag) != 0)
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{
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exhausted = true;
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return 0UL;
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}
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while (true)
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{
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if (Volatile.Read(ref divisorsExhaustedFlag) != 0)
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{
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exhausted = true;
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return 0UL;
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}
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long currentBits = Volatile.Read(ref nextDivisorBits);
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ulong currentValue = unchecked((ulong)currentBits);
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if (currentValue > divisorLimit)
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{
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if (Interlocked.CompareExchange(ref divisorsExhaustedFlag, 1, 0) == 0)
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{
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Volatile.Write(ref finalDivisorBits, currentBits);
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}
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long currentBits = Volatile.Read(ref nextDivisorBits);
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ulong currentValue = unchecked((ulong)currentBits);
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if (currentValue > divisorLimit)
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{
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if (Interlocked.CompareExchange(ref divisorsExhaustedFlag, 1, 0) == 0)
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{
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Volatile.Write(ref finalDivisorBits, currentBits);
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}
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exhausted = true;
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return 0UL;
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}
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exhausted = true;
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return 0UL;
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}
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ulong maximumNext = divisorLimit >= ulong.MaxValue - 1UL ? ulong.MaxValue : divisorLimit + 2UL;
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ulong requestedNext = currentValue > ulong.MaxValue - blockStride ? ulong.MaxValue : currentValue + blockStride;
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if (requestedNext > maximumNext)
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{
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requestedNext = maximumNext;
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}
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ulong maximumNext = divisorLimit >= ulong.MaxValue - 1UL ? ulong.MaxValue : divisorLimit + 2UL;
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ulong requestedNext = currentValue > ulong.MaxValue - blockStride ? ulong.MaxValue : currentValue + blockStride;
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if (requestedNext > maximumNext)
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{
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requestedNext = maximumNext;
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}
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long nextBits = unchecked((long)requestedNext);
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if (Interlocked.CompareExchange(ref nextDivisorBits, nextBits, currentBits) != currentBits)
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{
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continue;
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}
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long nextBits = unchecked((long)requestedNext);
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if (Interlocked.CompareExchange(ref nextDivisorBits, nextBits, currentBits) != currentBits)
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{
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continue;
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}
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ulong available = requestedNext - currentValue;
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if (available == 0UL)
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{
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continue;
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}
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ulong available = requestedNext - currentValue;
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if (available == 0UL)
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{
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continue;
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}
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int count = (int)(available >> 1);
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if (count <= 0)
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{
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continue;
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}
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int count = (int)(available >> 1);
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if (count <= 0)
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{
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continue;
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}
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localDivisorCursor = currentValue + 2UL;
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localDivisorsRemaining = count - 1;
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exhausted = false;
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return currentValue;
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}
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}
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localDivisorCursor = currentValue;
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localDivisorsRemaining = count;
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if (TryAcquireLocalDivisor(ref localDivisorCursor, ref localDivisorsRemaining, out ulong candidate))
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{
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exhausted = false;
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return candidate;
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}
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// No valid divisor was found in this range; attempt to acquire the next block.
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localDivisorCursor = 0UL;
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localDivisorsRemaining = 0;
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}
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}
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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private static bool TryAcquireLocalDivisor(ref ulong cursor, ref int remaining, out ulong divisor)
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{
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while (remaining > 0)
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{
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ulong candidate = cursor;
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cursor += 2UL;
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remaining--;
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if (IsAllowedDivisorCandidate(candidate))
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{
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divisor = candidate;
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return true;
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}
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}
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divisor = 0UL;
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return false;
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}
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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private static bool IsAllowedDivisorCandidate(ulong divisor)
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{
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if ((divisor & 1UL) == 0UL)
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{
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return false;
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}
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if ((divisor % 3UL) == 0UL || (divisor % 5UL) == 0UL || (divisor % 7UL) == 0UL || (divisor % 11UL) == 0UL)
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{
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return false;
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}
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return true;
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}
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private static int BuildPrimeBuffer(ulong divisor, in ulong[] primeValues, in ulong[] allowedMaxValues, int[] stateFlags, ulong[] primeBuffer, int[] indexBuffer, PendingResult[] completionsBuffer, ref int completionsCount, ref int remainingStates, long[] activeStateMask, ref int activeStartIndex)
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{
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