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% 10 operations replaces with UInt128/ulong.Mod10 methods

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Marek Lemańczyk committed 2025-09-21 07:42:25 +02:00
1 parent 3e0102a404
commit 412ce4fd50
13 files changed
+256 -195
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PerfectNumbers.Core/ModuloAutomata.cs
+4 -19
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@@ -30,12 +30,12 @@ public sealed class MersenneResidueAutomaton
_currentQ = _step + 1UL; // start at k = 1
// init residues
Mod10R = Mod10(_currentQ);
Mod10R = _currentQ.Mod10();
Mod8R = Mod8(_currentQ);
Mod3R = Mod3(_currentQ);
Mod5R = Mod5(_currentQ);
_step10 = Mod10((ulong)(_step % 10UL));
_step10 = _step.Mod10().Mod10();
_step8 = (ulong)(_step & 7UL); // % 8
_step3 = Mod3(_step);
_step5 = Mod5(_step);
@@ -72,21 +72,6 @@ public sealed class MersenneResidueAutomaton
Mod5R = r5;
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static ulong Mod10(UInt128 value)
{
// Split and fold under mod 10: 2^64 ≡ 6 (mod 10)
ulong high = (ulong)(value >> 64);
ulong low = (ulong)value;
ulong highRem = Mod10(high);
ulong lowRem = Mod10(low);
ulong combined = lowRem + highRem * 6UL;
return Mod10(combined);
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static ulong Mod10(ulong value) => value % 10UL;
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static ulong Mod8(UInt128 value) => (ulong)value & 7UL;
@@ -196,8 +181,8 @@ public sealed class Ending7Automaton
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static ulong AlignTo7(ulong start)
{
ulong r = start % 10UL;
ulong add = (7UL + 10UL - r) % 10UL;
ulong r = start.Mod10();
ulong add = (7UL + 10UL - r).Mod10();
return start + add;
}