Fix RelationCache on Windows 10 compiles

Windows 10 is missing the GroupMasks and GroupCount members, this breaks compiles on Windows 10.
Windows 11 builds, including the official ones, run fine on Windows 10/11.
To support developers/testers on Windows 10, fallback conditionally to the Windows 10 struct definition.

closes https://github.com/official-stockfish/Stockfish/pull/6538

No functional change

src/numa.h

@@ -371,6 +371,50 @@ inline WindowsAffinity get_process_affinity() {
     return affinity;
 }
 
+// Type machinery used to emulate Cache->GroupCount
+
+template<typename T, typename = void>
+struct HasGroupCount: std::false_type {};
+
+template<typename T>
+struct HasGroupCount<T, std::void_t<decltype(std::declval<T>().Cache.GroupCount)>>: std::true_type {
+};
+
+template<typename T, typename Pred, std::enable_if_t<HasGroupCount<T>::value, bool> = true>
+std::set<CpuIndex> readCacheMembers(const T* info, Pred&& is_cpu_allowed) {
+    std::set<CpuIndex> cpus;
+    // On Windows 10 this will read a 0 because GroupCount doesn't exist
+    int groupCount = std::max(info->Cache.GroupCount, WORD(1));
+    for (WORD procGroup = 0; procGroup < groupCount; ++procGroup)
+    {
+        for (BYTE number = 0; number < WIN_PROCESSOR_GROUP_SIZE; ++number)
+        {
+            WORD           groupNumber = info->Cache.GroupMasks[procGroup].Group;
+            const CpuIndex c = static_cast<CpuIndex>(groupNumber) * WIN_PROCESSOR_GROUP_SIZE
+                             + static_cast<CpuIndex>(number);
+            if (!(info->Cache.GroupMasks[procGroup].Mask & (1ULL << number)) || !is_cpu_allowed(c))
+                continue;
+            cpus.insert(c);
+        }
+    }
+    return cpus;
+}
+
+template<typename T, typename Pred, std::enable_if_t<!HasGroupCount<T>::value, bool> = true>
+std::set<CpuIndex> readCacheMembers(const T* info, Pred&& is_cpu_allowed) {
+    std::set<CpuIndex> cpus;
+    for (BYTE number = 0; number < WIN_PROCESSOR_GROUP_SIZE; ++number)
+    {
+        WORD           groupNumber = info->Cache.GroupMask.Group;
+        const CpuIndex c           = static_cast<CpuIndex>(groupNumber) * WIN_PROCESSOR_GROUP_SIZE
+                         + static_cast<CpuIndex>(number);
+        if (!(info->Cache.GroupMask.Mask & (1ULL << number)) || !is_cpu_allowed(c))
+            continue;
+        cpus.insert(c);
+    }
+    return cpus;
+}
+
 #endif
 
 #if defined(__linux__) && !defined(__ANDROID__)
@@ -1174,29 +1218,17 @@ class NumaConfig {
             if (info->Relationship == RelationCache && info->Cache.Level == 3)
             {
                 L3Domain domain{};
-                for (WORD procGroup = 0; procGroup < info->Cache.GroupCount; ++procGroup)
+                domain.cpus = readCacheMembers(info, is_cpu_allowed);
-                {
-                    for (BYTE number = 0; number < WIN_PROCESSOR_GROUP_SIZE; ++number)
-                    {
-                        WORD           groupNumber = info->Cache.GroupMasks[procGroup].Group;
-                        const CpuIndex c =
-                          static_cast<CpuIndex>(groupNumber) * WIN_PROCESSOR_GROUP_SIZE
-                          + static_cast<CpuIndex>(number);
-                        if (!(info->Cache.GroupMasks[procGroup].Mask & (1ULL << number))
-                            || !is_cpu_allowed(c))
-                            continue;
-                        domain.systemNumaIndex = systemConfig.nodeByCpu.at(c);
-                        domain.cpus.insert(c);
-                    }
-                }
                 if (!domain.cpus.empty())
+                {
+                    domain.systemNumaIndex = systemConfig.nodeByCpu.at(*domain.cpus.begin());
                     l3Domains.push_back(std::move(domain));
                 }
+            }
             // Variable length data structure, advance to next
             info = reinterpret_cast<PSYSTEM_LOGICAL_PROCESSOR_INFORMATION_EX>(
               reinterpret_cast<char*>(info) + info->Size);
         }
-
 #endif
 
         if (!l3Domains.empty())