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

Inline single-use modulo helpers

Browse Source
This commit is contained in:
Marek Lemańczyk committed 2025-09-22 19:54:54 +02:00
1 parent 3598f88aaf
commit 3b8a10a20b
5 files changed
+33 -35
Download Patch File Download Diff File Expand all files Collapse all files

No files matched your search

PerfectNumbers.Core/Cpu/MersenneNumberLucasLehmerCpuTester.cs
+10 -14
View File
@@ -4,20 +4,16 @@ public class MersenneNumberLucasLehmerCpuTester
{
public bool IsPrime(ulong exponent)
{
// Early rejections aligned with incremental/order sieves, but safe for small p:
// - If 3 | p and p != 3, then 7 | M_p -> composite.
// - If p ≡ 1 (mod 4) and p shares a factor with (p-1), reject fast.
// - If p is divisible by divisors specific to numbers ending with 1 or 7, reject fast.
ulong mod3 = exponent.Mod3();
ulong mod5 = exponent.Mod5();
ulong mod7 = exponent.Mod7();
ulong mod11 = exponent.Mod11();
if (
(mod3 == 0UL && exponent != 3UL) ||
(mod5 == 0UL && exponent != 5UL) ||
(mod7 == 0UL && exponent != 7UL) ||
(mod11 == 0UL && exponent != 11UL)
)
// Early rejections aligned with incremental/order sieves, but safe for small p:
// - If 3 | p and p != 3, then 7 | M_p -> composite.
// - If p ≡ 1 (mod 4) and p shares a factor with (p-1), reject fast.
// - If p is divisible by divisors specific to numbers ending with 1 or 7, reject fast.
if (
(exponent.Mod3() == 0UL && exponent != 3UL) ||
(exponent.Mod5() == 0UL && exponent != 5UL) ||
(exponent.Mod7() == 0UL && exponent != 7UL) ||
(exponent.Mod11() == 0UL && exponent != 11UL)
)
{
return false;
}