From 949b5f891c6b39d3ac3310e970a67ba84f8468e5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marek=20Lema=C5=84czyk?= <marek@lemanczyk.eu>
Date: Thu, 16 Oct 2025 04:52:22 +0200
Subject: [PATCH] Return windowed Montgomery odd powers to pooling

---
 PerfectNumbers.Core/ULongExtensions.cs | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/PerfectNumbers.Core/ULongExtensions.cs b/PerfectNumbers.Core/ULongExtensions.cs
index 0271021..c09ce8e 100644
--- a/PerfectNumbers.Core/ULongExtensions.cs
+++ b/PerfectNumbers.Core/ULongExtensions.cs
@@ -346,7 +346,8 @@ public static class ULongExtensions
         ulong result = divisor.MontgomeryOne;
         ulong nPrime = divisor.NPrime;
 
-        Span<ulong> oddPowers = stackalloc ulong[oddPowerCount];
+        ulong[] oddPowersArray = ThreadStaticPools.UlongPool.Rent(oddPowerCount);
+        Span<ulong> oddPowers = oddPowersArray.AsSpan(0, oddPowerCount);
         InitializeMontgomeryOddPowersCpu(divisor, modulus, nPrime, oddPowers);
 
         int index = bitLength - 1;
@@ -385,13 +386,14 @@ public static class ULongExtensions
             index = windowStart - 1;
         }
 
+        ThreadStaticPools.UlongPool.Return(oddPowersArray);
 
-        if (keepMontgomery)
+        if (!keepMontgomery)
         {
-            return result;
+            result = result.MontgomeryMultiply(1UL, modulus, nPrime);
         }
 
-        return result.MontgomeryMultiply(1UL, modulus, nPrime);
+        return result;
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]