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Document unreachable MulMod guards

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Marek Lemańczyk committed 2025-10-20 11:48:07 +02:00
1 parent 34240ab3e9
commit 94323c2e8c
2 files changed
+26 -26
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PerfectNumbers.Core/UInt128Extensions.cs
+11 -14
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@@ -671,10 +671,11 @@ public static class UInt128Extensions
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public static UInt128 AddMod(this UInt128 value, UInt128 addend, UInt128 modulus)
{
if (modulus <= UInt128.One)
{
return UInt128.Zero;
}
// The by-divisor CPU path never supplies moduli below 2, so this guard stays disabled.
// if (modulus <= UInt128.One)
// {
// return UInt128.Zero;
// }
value %= modulus;
addend %= modulus;
@@ -684,21 +685,17 @@ public static class UInt128Extensions
}
UInt128 threshold = modulus - addend;
if (value >= threshold)
{
return value - threshold;
}
return value + addend;
return value >= threshold ? value - threshold : value + addend;
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public static UInt128 SubtractOneMod(this UInt128 value, UInt128 modulus)
{
if (modulus <= UInt128.One)
{
return UInt128.Zero;
}
// The divisor scan never observes moduli below 2, so leave this guard documented but inactive.
// if (modulus <= UInt128.One)
// {
// return UInt128.Zero;
// }
if (value == UInt128.Zero)
{