Fix build compatibility with older PyTorch versions

Differential Revision: D88671081

Author: tanquer

comms/torchcomms/ncclx/TorchCommNCCLXCCA.cpp

@@ -7,46 +7,20 @@
 // Helper to detect if c10::CachingAllocator constants exist
 namespace {
 
-// Helper to get kLargeBuffer from c10::CachingAllocator if it exists
-template <typename = void>
-struct LargeBufferGetter {
-  static constexpr size_t get() {
-    return 20971520; // 20MB (20 * 1024 * 1024) - fallback
-  }
-};
-
-// Specialization when c10::CachingAllocator::kLargeBuffer exists
-template <>
-struct LargeBufferGetter<
-    std::void_t<decltype(c10::CachingAllocator::kLargeBuffer)>> {
-  static constexpr size_t get() {
-    return c10::CachingAllocator::kLargeBuffer;
-  }
-};
-
-// Helper to get kSmallBuffer from c10::CachingAllocator if it exists
-template <typename = void>
-struct SmallBufferGetter {
-  static constexpr size_t get() {
-    return 2097152; // 2MB (2 * 1024 * 1024) - fallback
-  }
-};
-
-// Specialization when c10::CachingAllocator::kSmallBuffer exists
-template <>
-struct SmallBufferGetter<
-    std::void_t<decltype(c10::CachingAllocator::kSmallBuffer)>> {
-  static constexpr size_t get() {
-    return c10::CachingAllocator::kSmallBuffer;
-  }
-};
-
-inline size_t getLargeBufferSize() {
-  return LargeBufferGetter<>::get();
+size_t getLargeBufferSize() {
+#if __has_include(<c10/core/AllocatorConfig.h>)
+  return c10::CachingAllocator::kLargeBuffer;
+#else
+  return 20971520; // 20MB (20 * 1024 * 1024) - fallback
+#endif
 }
 
-inline size_t getSmallBufferSize() {
-  return SmallBufferGetter<>::get();
+size_t getSmallBufferSize() {
+#if __has_include(<c10/core/AllocatorConfig.h>)
+  return c10::CachingAllocator::kSmallBuffer;
+#else
+  return 2097152; // 2MB (2 * 1024 * 1024) - fallback
+#endif
 }
 } // namespace