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+/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#ifndef TENSORFLOW_COMPILER_XLA_SERVICE_GPU_BUFFER_COMPARATOR_H_
+#define TENSORFLOW_COMPILER_XLA_SERVICE_GPU_BUFFER_COMPARATOR_H_
+
+#include "tensorflow/compiler/xla/service/compiler.h"
+#include "tensorflow/compiler/xla/service/device_memory_allocator.h"
+#include "tensorflow/compiler/xla/service/gpu/gpu_executable.h"
+#include "tensorflow/core/platform/stream_executor_no_cuda.h"
+
+namespace xla {
+namespace gpu {
+
+// A fp16 comparator that internally keeps a reference buffer, and compares it
+// against other test buffers.
+class F16BufferComparator {
+ public:
+  F16BufferComparator(const F16BufferComparator&) = delete;
+  F16BufferComparator(F16BufferComparator&&) = default;
+
+  // Creates a new comparator. It internally allocates a buffer initialized by
+  // ref_buffer.
+  static StatusOr<F16BufferComparator> Create(
+      se::DeviceMemory<Eigen::half> ref_buffer, Compiler* compiler,
+      DeviceMemoryAllocator* allocator, se::Stream* stream);
+
+  // Returns true if the internally allocated buffer "compares equal" to
+  // test_buffer. The definition of "equal" is:
+  // * All NaNs equal.
+  // * All infs are treated as 65505 or -65505, so that this checker is tolerant
+  //   to fp16 overflows.
+  // * With NaNs and infs taken care of, a and b compare equal iff:
+  //     abs(a - b) / (max(abs(a), abs(b)) + 1) < tolerance
+  //
+  // See the implementation for the tolerance value.
+  StatusOr<bool> CompareEqual(se::DeviceMemory<Eigen::half> test_buffer);
+
+ private:
+  F16BufferComparator(se::Stream* stream, DeviceMemoryAllocator* allocator,
+                      std::unique_ptr<Executable> exec,
+                      ScopedShapedBuffer ref_buffer)
+      : stream_(stream),
+        allocator_(allocator),
+        exec_(std::move(exec)),
+        ref_buffer_(std::move(ref_buffer)) {}
+
+  StatusOr<bool> CompareEqualImpl(se::DeviceMemory<Eigen::half> test_buffer);
+
+  se::Stream* stream_;
+  DeviceMemoryAllocator* allocator_;
+  std::unique_ptr<Executable> exec_;
+  ScopedShapedBuffer ref_buffer_;
+};
+
+}  // namespace gpu
+}  // namespace xla
+
+#endif  // TENSORFLOW_COMPILER_XLA_SERVICE_GPU_BUFFER_COMPARATOR_H_