mlemanczyk/even-perfect-numbers-scanner
1
0 Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Clarify cycle stepper reset inlining

Browse Source
This commit is contained in:
Marek Lemańczyk committed 2025-10-02 13:30:56 +02:00
1 parent 8b467c27f3
commit b8aa845c5c
53 files changed
+1736 -1131
Download Patch File Download Diff File Expand all files Collapse all files

No files matched your search

PerfectNumbers.Core/MersenneNumberTester.cs
+31 -24
View File
@@ -36,6 +36,9 @@ public sealed class MersenneNumberTester(
private readonly bool _useGpuScan = useGpuScan; // device for pow2mod/incremental scanning
private readonly bool _useGpuOrder = useGpuOrder; // device for order computations
private static readonly ConcurrentDictionary<UInt128, ulong> OrderCache = new();
// TODO: Swap this ConcurrentDictionary for the pooled dictionary variant highlighted in
// Pow2MontgomeryModBenchmarks once order warmups reuse deterministic divisor-cycle snapshots; the pooled approach removed
// the locking overhead when scanning p >= 138M in those benchmarks.
private readonly MersenneNumberIncrementalGpuTester _incrementalGpuTester = new(kernelType, useGpuOrder);
private readonly MersenneNumberIncrementalCpuTester _incrementalCpuTester = new(kernelType);
private readonly MersenneNumberOrderGpuTester _orderGpuTester = new(kernelType, useGpuOrder);
@@ -56,32 +59,34 @@ public sealed class MersenneNumberTester(
return;
}
UInt128 twoP = (UInt128)exponent << 1; // 2 * p
bool lastIsSeven = (exponent & 3UL) == 3UL;
// CPU path: compute orders directly and cache
if (!_useGpuOrder)
{
UInt128 k = UInt128.One;
UInt128 twoP = (UInt128)exponent << 1; // 2 * p
bool lastIsSeven = (exponent & 3UL) == 3UL;
// CPU path: compute orders directly and cache
if (!_useGpuOrder)
{
UInt128 k = UInt128.One;
UInt128 q;
ulong remainder;
for (; k <= limit; k++)
{
q = twoP * k + UInt128.One;
remainder = q.Mod10();
bool shouldCheck = lastIsSeven
? remainder == 7UL || remainder == 9UL || remainder == 3UL
: remainder == 1UL || remainder == 3UL || remainder == 9UL;
{
q = twoP * k + UInt128.One;
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
? remainder == 7UL || remainder == 9UL || remainder == 3UL
: remainder == 1UL || remainder == 3UL || remainder == 9UL;
// Early modular filters for odd order and small-prime rejections
// Early modular filters for odd order and small-prime rejections
if (shouldCheck)
{
ulong mod8 = q.Mod8();
if (mod8 != 1UL && mod8 != 7UL)
{
continue;
}
if (mod8 != 1UL && mod8 != 7UL)
{
continue;
}
else if (q.Mod3() == 0UL || q.Mod5() == 0UL)
{
{
continue;
}
}
@@ -107,13 +112,15 @@ public sealed class MersenneNumberTester(
ulong remainder2;
for (; k2 <= limit; k2++)
{
q2 = twoP * k2 + 1UL;
remainder2 = q2.Mod10();
bool shouldCheck2 = lastIsSeven
? remainder2 == 7UL || remainder2 == 9UL || remainder2 == 3UL
: remainder2 == 1UL || remainder2 == 3UL || remainder2 == 9UL;
q2 = twoP * k2 + 1UL;
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
? remainder2 == 7UL || remainder2 == 9UL || remainder2 == 3UL
: remainder2 == 1UL || remainder2 == 3UL || remainder2 == 9UL;
// Early modular filters for odd order and small-prime rejections
// Early modular filters for odd order and small-prime rejections
if (shouldCheck2)
{
ulong mod8 = q2.Mod8();