v4.0 update. (#2371)

examples/77_blackwell_fmha/reference/reference_abs_error.hpp

@@ -75,6 +75,8 @@ struct DeviceAllocation {
 
   size_t size() const { return size_; }
 
+  size_t get_storage_size() const { return (size_ + offset_) * sizeof(T); }
+
   void copy_from_host(const T* ptr, size_t sz) {
     auto ret = cudaMemcpy(ptr_, ptr, sz * sizeof(T), cudaMemcpyDefault);
     assert(ret == cudaSuccess);