From 85c6eaece7615dd85aafedc52cfb333d537b8ef5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marek=20Lema=C5=84czyk?= <marek@lemanczyk.eu>
Date: Sat, 4 Oct 2025 22:40:02 +0200
Subject: [PATCH] Persist GPU capability snapshot without volatile

---
 .../Gpu/PrimeOrderGpuHeuristics.cs               | 16 +++++-----------
 todo.txt                                         |  2 ++
 2 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/PerfectNumbers.Core/Gpu/PrimeOrderGpuHeuristics.cs b/PerfectNumbers.Core/Gpu/PrimeOrderGpuHeuristics.cs
index 21583db..9138697 100644
--- a/PerfectNumbers.Core/Gpu/PrimeOrderGpuHeuristics.cs
+++ b/PerfectNumbers.Core/Gpu/PrimeOrderGpuHeuristics.cs
@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Concurrent;
 using System.Numerics;
-using System.Threading;
 
 namespace PerfectNumbers.Core.Gpu;
 
@@ -15,23 +14,18 @@ internal enum GpuPow2ModStatus
 internal static class PrimeOrderGpuHeuristics
 {
     private static readonly ConcurrentDictionary<ulong, byte> OverflowedPrimes = new();
-    private static int s_modulusBitLimit = PrimeOrderGpuCapability.Default.ModulusBits;
-    private static int s_exponentBitLimit = PrimeOrderGpuCapability.Default.ExponentBits;
+    private static PrimeOrderGpuCapability s_capability = PrimeOrderGpuCapability.Default;
 
     internal static void OverrideCapabilitiesForTesting(PrimeOrderGpuCapability capability)
     {
-        Volatile.Write(ref s_modulusBitLimit, capability.ModulusBits);
-        Volatile.Write(ref s_exponentBitLimit, capability.ExponentBits);
+        s_capability = capability;
     }
 
     internal static void ResetCapabilitiesForTesting()
     {
-        OverrideCapabilitiesForTesting(PrimeOrderGpuCapability.Default);
+        s_capability = PrimeOrderGpuCapability.Default;
     }
 
-    private static PrimeOrderGpuCapability Capabilities
-        => new(Volatile.Read(ref s_modulusBitLimit), Volatile.Read(ref s_exponentBitLimit));
-
     internal static void MarkOverflow(ulong prime) => OverflowedPrimes[prime] = 0;
 
     internal static void ClearOverflow(ulong prime) => OverflowedPrimes.TryRemove(prime, out _);
@@ -51,7 +45,7 @@ internal static class PrimeOrderGpuHeuristics
             return GpuPow2ModStatus.Overflow;
         }
 
-        PrimeOrderGpuCapability capability = Capabilities;
+        PrimeOrderGpuCapability capability = s_capability;
 
         if (!SupportsPrime(prime, capability))
         {
@@ -92,7 +86,7 @@ internal static class PrimeOrderGpuHeuristics
             return GpuPow2ModStatus.Overflow;
         }
 
-        PrimeOrderGpuCapability capability = Capabilities;
+        PrimeOrderGpuCapability capability = s_capability;
 
         if (!SupportsPrime(prime, capability))
         {
diff --git a/todo.txt b/todo.txt
index 5f09bfc..c898b2f 100644
--- a/todo.txt
+++ b/todo.txt
@@ -1,2 +1,4 @@
+- Inline the overflow tracking helpers in PrimeOrderGpuHeuristics so call sites can cache the dictionary locally and reduce delegate indirection.
+- Move the ulong bit-length helper into ULongExtensions and update PrimeOrderGpuHeuristics (and any other callers) to reuse it.
 - Implement the GPU heuristics for PrimeOrderCalculator using ILGPU. Reuse the numeric type compatibility probe results to select between EInteger, ERational, GpuUInt128, or any new GPU-specific big-integer representations, guarantee parity with the CPU heuristic algorithm (including 128-bit primes), prefer the shift-first multiply/shift variant to stay within device ranges, and wire the calculator through the accelerator path.
 - Extend the GPU numeric type probe to cover proposed custom types such as GpuUInt256 and GpuUInt512 once their definitions are available so we can plan the wide-order heuristics on the device.