chore: import upstream snapshot with attribution

paddle/phi/kernels/trace_kernel.h

@@ -0,0 +1,48 @@
+// Copyright (c) 2022 PaddlePaddle 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.
+
+#pragma once
+
+#include "paddle/phi/core/dense_tensor.h"
+
+namespace phi {
+
+/**
+ * @brief Trace Kernel.
+ *        Return the sum along diagonals of the input tensor.
+ *        The behavior of this operator is similar to how `numpy.trace` works.
+ *
+ *        If Input is 2-D, returns the sum of diagonal.
+ *        If Input has larger dimensions, then returns an tensor of diagonals
+ *        sum, diagonals be taken from the 2-D planes specified by dim1 and
+ *        dim2.
+ * @param  ctx      device context
+ * @param  x        The input tensor, from which the diagonals are taken
+ * @param  offset   offset of the diagonal from the main diagonal.
+ *                  Can be bothpositive and negative.
+ * @param  axis1    the first axis of the 2-D planes from which the diagonals
+ *                  should be taken. Can be either positive or negative
+ * @param  axis2    the second axis of the 2-D planes from which the diagonals
+ *                  should be taken. Can be either positive or negative
+ * @param  out      the sum along diagonals of the input tensor
+ */
+template <typename T, typename Context>
+void TraceKernel(const Context& dev_ctx,
+                 const DenseTensor& x,
+                 int offset,
+                 int axis1,
+                 int axis2,
+                 DenseTensor* out);
+
+}  // namespace phi