From c697a7e127f822b01cbc6336aad73985005a8273 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marek=20Lema=C5=84czyk?= <marek@lemanczyk.eu>
Date: Thu, 23 Oct 2025 01:48:11 +0200
Subject: [PATCH] Throw when divisor cycle resolution fails

---
 PerfectNumbers.Core/Cpu/MersenneCpuDivisorScanSession.cs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/PerfectNumbers.Core/Cpu/MersenneCpuDivisorScanSession.cs b/PerfectNumbers.Core/Cpu/MersenneCpuDivisorScanSession.cs
index 1dcd49b..1279369 100644
--- a/PerfectNumbers.Core/Cpu/MersenneCpuDivisorScanSession.cs
+++ b/PerfectNumbers.Core/Cpu/MersenneCpuDivisorScanSession.cs
@@ -35,8 +35,8 @@ internal sealed class MersenneCpuDivisorScanSession : IMersenneNumberDivisorByDi
             divisorCycle = DivisorCycleCache.Shared.GetCycleLength(divisor);
             if (divisorCycle == 0UL)
             {
-                hits.Clear();
-                return;
+                // DivisorCycleCache guarantees a positive cycle for divisors greater than one.
+                throw new InvalidOperationException($"Divisor cycle solver returned zero for divisor {divisor}.");
             }
         }