mlemanczyk/even-perfect-numbers-scanner
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Use LastDigit enum across Mersenne scanners

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Marek Lemańczyk committed 2025-10-26 16:04:05 +01:00
1 parent 43c7bafd5d
commit a83ae56caf
15 files changed
+83 -49
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PerfectNumbers.Core/MersenneNumberTester.cs
+13 -13
View File
@@ -58,7 +58,7 @@ public sealed class MersenneNumberTester(
}
UInt128 twoP = (UInt128)exponent << 1; // 2 * p
bool lastIsSeven = (exponent & 3UL) == 3UL;
LastDigit lastDigit = (exponent & 3UL) == 3UL ? LastDigit.Seven : LastDigit.One;
// CPU path: compute orders directly and cache
if (!_useGpuOrder)
{
@@ -71,7 +71,7 @@ public sealed class MersenneNumberTester(
remainder = q.Mod10();
// TODO: Replace these repeated Mod10/Mod8/Mod3/Mod5 calls with a residue automaton walk so
// order warmups reuse the optimized cycle stepping validated in the residue benchmarks.
bool shouldCheck = lastIsSeven
bool shouldCheck = lastDigit == LastDigit.Seven
? remainder == 7UL || remainder == 9UL || remainder == 3UL
: remainder == 1UL || remainder == 3UL || remainder == 9UL;
@@ -112,7 +112,7 @@ public sealed class MersenneNumberTester(
remainder2 = q2.Mod10();
// TODO: Reuse the same residue-automaton fast path here so the GPU warmup staging avoids `%` and
// branches the benchmarks showed slower than the tracked stepping helper.
bool shouldCheck2 = lastIsSeven
bool shouldCheck2 = lastDigit == LastDigit.Seven
? remainder2 == 7UL || remainder2 == 9UL || remainder2 == 3UL
: remainder2 == 1UL || remainder2 == 3UL || remainder2 == 9UL;
@@ -230,7 +230,7 @@ public sealed class MersenneNumberTester(
UInt128 twoP = (UInt128)exponent << 1; // 2 * p
// UInt128 maxDivisor = new(ulong.MaxValue, ulong.MaxValue);
UInt128 maxK = UInt128Numbers.Two.Pow(exponent) / 2 + 1;
bool lastIsSeven = (exponent & 3UL) == 3UL;
LastDigit lastDigit = (exponent & 3UL) == 3UL ? LastDigit.Seven : LastDigit.One;
// In residue mode the residue scan is the final primality check.
if (_useResidue)
@@ -242,11 +242,11 @@ public sealed class MersenneNumberTester(
if (_useGpuScan)
{
_residueGpuTester!.Scan(exponent, twoP, lastIsSeven, maxK, ref prePrime);
_residueGpuTester!.Scan(exponent, twoP, lastDigit, maxK, ref prePrime);
}
else
{
_residueCpuTester!.Scan(exponent, twoP, lastIsSeven, maxK, ref prePrime);
_residueCpuTester!.Scan(exponent, twoP, lastDigit, maxK, ref prePrime);
}
return prePrime;
@@ -258,14 +258,14 @@ public sealed class MersenneNumberTester(
// Scan a limited range of k to quickly reject obvious cases.
UInt128 twoPPre = (UInt128)exponent << 1;
UInt128 maxKPre = (UInt128)PreLucasPreScanK;
bool lastIsSevenPre = (exponent & 3UL) == 3UL;
LastDigit lastDigitPre = (exponent & 3UL) == 3UL ? LastDigit.Seven : LastDigit.One;
if (_useGpuScan)
{
_incrementalGpuTester.Scan(exponent, twoPPre, lastIsSevenPre, maxKPre, ref prePrime);
_incrementalGpuTester.Scan(exponent, twoPPre, lastDigitPre, maxKPre, ref prePrime);
}
else
{
_incrementalCpuTester.Scan(exponent, twoPPre, lastIsSevenPre, maxKPre, ref prePrime);
_incrementalCpuTester.Scan(exponent, twoPPre, lastDigitPre, maxKPre, ref prePrime);
}
if (!prePrime)
@@ -284,22 +284,22 @@ public sealed class MersenneNumberTester(
{
if (_useGpuOrder)
{
_orderGpuTester.Scan(exponent, twoP, lastIsSeven, maxK, ref isPrime);
_orderGpuTester.Scan(exponent, twoP, lastDigit, maxK, ref isPrime);
}
else
{
_orderCpuTester.Scan(exponent, twoP, lastIsSeven, maxK, ref isPrime);
_orderCpuTester.Scan(exponent, twoP, lastDigit, maxK, ref isPrime);
}
}
else
{
if (_useGpuScan)
{
_incrementalGpuTester.Scan(exponent, twoP, lastIsSeven, maxK, ref isPrime);
_incrementalGpuTester.Scan(exponent, twoP, lastDigit, maxK, ref isPrime);
}
else
{
_incrementalCpuTester.Scan(exponent, twoP, lastIsSeven, maxK, ref isPrime);
_incrementalCpuTester.Scan(exponent, twoP, lastDigit, maxK, ref isPrime);
}
}