chore: import upstream snapshot with attribution

dgl_sparse/include/sparse/reduction.h

@@ -0,0 +1,64 @@
+/**
+ *  Copyright (c) 2022 by Contributors
+ * @file sparse/reduction.h
+ * @brief DGL C++ sparse matrix reduction operators.
+ */
+#ifndef SPARSE_REDUCTION_H_
+#define SPARSE_REDUCTION_H_
+
+#include <sparse/sparse_matrix.h>
+
+#include <string>
+
+namespace dgl {
+namespace sparse {
+
+/**
+ * @brief Reduces a sparse matrix along the specified sparse dimension.
+ *
+ * @param A The sparse matrix.
+ * @param dim The sparse dimension to reduce along.  Must be either 0 (rows) or
+ * 1 (columns).
+ * @param reduce The reduce operator.  Must be either "sum", "smin", "smax",
+ * "mean", or "sprod".
+ *
+ * @return Tensor
+ */
+torch::Tensor Reduce(
+    const c10::intrusive_ptr<SparseMatrix>& A, const std::string& reduce,
+    const torch::optional<int64_t>& dim = torch::nullopt);
+
+inline torch::Tensor ReduceSum(
+    const c10::intrusive_ptr<SparseMatrix>& A,
+    const torch::optional<int64_t>& dim = torch::nullopt) {
+  return Reduce(A, "sum", dim);
+}
+
+inline torch::Tensor ReduceMin(
+    const c10::intrusive_ptr<SparseMatrix>& A,
+    const torch::optional<int64_t>& dim = torch::nullopt) {
+  return Reduce(A, "smin", dim);
+}
+
+inline torch::Tensor ReduceMax(
+    const c10::intrusive_ptr<SparseMatrix>& A,
+    const torch::optional<int64_t>& dim = torch::nullopt) {
+  return Reduce(A, "smax", dim);
+}
+
+inline torch::Tensor ReduceMean(
+    const c10::intrusive_ptr<SparseMatrix>& A,
+    const torch::optional<int64_t>& dim = torch::nullopt) {
+  return Reduce(A, "smean", dim);
+}
+
+inline torch::Tensor ReduceProd(
+    const c10::intrusive_ptr<SparseMatrix>& A,
+    const torch::optional<int64_t>& dim = torch::nullopt) {
+  return Reduce(A, "sprod", dim);
+}
+
+}  // namespace sparse
+}  // namespace dgl
+
+#endif  // SPARSE_REDUCTION_H_