mlemanczyk/even-perfect-numbers-scanner
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Modulo operators replaced with steppers, where possible.

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mlemanczyk committed 2025-12-08 20:57:47 +01:00
1 parent 475507ce0c
commit f7dbc017a9
15 files changed
+531 -151
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PerfectNumbers.Core/PrimeOrderCalculator.Cpu.cs
+10 -11
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@@ -266,7 +266,7 @@ internal static partial class PrimeOrderCalculator
int exponent = entries[i].Value;
for (int iteration = 0; iteration < exponent; iteration++)
{
if ((order % primeFactor) != UInt128.Zero)
if (order.ReduceCycleRemainder(primeFactor) != UInt128.Zero)
{
UInt128 candidate = order / primeFactor;
if (Pow2ModWideCpu(candidate, prime, divisorData) == UInt128.One)
@@ -339,14 +339,13 @@ internal static partial class PrimeOrderCalculator
buffer[..length].Sort(static (a, b) => a.Value.CompareTo(b.Value));
// TODO: Investigating using stepper to replace modulo operation
for (int i = 0; i < length; i++)
{
UInt128 primeFactor = buffer[i].Value;
int exponent = buffer[i].Exponent;
for (int iteration = 0; iteration < exponent; iteration++)
{
if ((order % primeFactor) == UInt128.Zero)
if (order.ReduceCycleRemainder(primeFactor) == UInt128.Zero)
{
UInt128 reduced = order / primeFactor;
if (Pow2ModWideCpu(reduced, prime, divisorData) == UInt128.One)
@@ -405,7 +404,7 @@ internal static partial class PrimeOrderCalculator
UInt128 reduced = order;
for (int iteration = 0; iteration < span[i].Exponent; iteration++)
{
if ((reduced % primeFactor) != UInt128.Zero)
if (reduced.ReduceCycleRemainder(primeFactor) != UInt128.Zero)
{
break;
}
@@ -2583,7 +2582,7 @@ internal static partial class PrimeOrderCalculator
// continue;
// }
if ((remainingLocal % primeValue) != 0UL)
if (remainingLocal.ReduceCycleRemainder(primeValue) != 0UL)
{
continue;
}
@@ -2745,16 +2744,16 @@ internal static partial class PrimeOrderCalculator
private static ulong AdvancePolynomialCpu(ulong x, ulong c, ulong modulus)
{
UInt128 value = (UInt128)x * x + c;
return (ulong)(value % modulus);
return (ulong)value.ReduceCycleRemainder(modulus);
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static ulong AdvancePolynomialTwiceCpu(ulong x, ulong c, ulong modulus)
{
UInt128 value = (UInt128)x * x + c;
var remainder = (ulong)(value % modulus);
var remainder = (ulong)value.ReduceCycleRemainder(modulus);
value = (UInt128)remainder * remainder + c;
return (ulong)(value % modulus);
return (ulong)value.ReduceCycleRemainder(modulus);
}
private static ulong BinaryGcd(ulong a, ulong b)
@@ -2897,7 +2896,7 @@ internal static partial class PrimeOrderCalculator
int exponent = entries[i].Value;
for (int iteration = 0; iteration < exponent; iteration++)
{
ulong remainder = order % primeFactor;
ulong remainder = order.ReduceCycleRemainder(primeFactor);
if (remainder != 0UL)
{
break;
@@ -2951,7 +2950,7 @@ internal static partial class PrimeOrderCalculator
{
int exponent = 1;
ulong remaining = quotient;
while ((remaining % factor) == 0UL)
while (remaining.ReduceCycleRemainder(factor) == 0UL)
{
remaining /= factor;
exponent++;
@@ -3062,7 +3061,7 @@ internal static partial class PrimeOrderCalculator
UInt128 reduced = candidate;
for (int iteration = 0; iteration < span[i].Exponent; iteration++)
{
if ((reduced % primeFactor) != UInt128.Zero)
if (reduced.ReduceCycleRemainder(primeFactor) != UInt128.Zero)
{
break;
}