[imap] create variant type of supported index maps

include/ginkgo/core/distributed/index_map_fwd.hpp

@@ -0,0 +1,30 @@
+// SPDX-FileCopyrightText: 2017 - 2024 The Ginkgo authors
+//
+// SPDX-License-Identifier: BSD-3-Clause
+
+#ifndef GINKGO_INDEX_MAP_FWD_HPP
+#define GINKGO_INDEX_MAP_FWD_HPP
+
+#include <variant>
+
+#include <ginkgo/core/base/types.hpp>
+
+
+namespace gko {
+namespace experimental {
+namespace distributed {
+
+
+template <typename LocalIndexType, typename GlobalIndexType>
+class index_map;
+
+using index_map_variant =
+    std::variant<index_map<int32, int32>, index_map<int32, int64>,
+                 index_map<int64, int64>>;
+
+
+}  // namespace distributed
+}  // namespace experimental
+}  // namespace gko
+
+#endif  // GINKGO_INDEX_MAP_FWD_HPP

include/ginkgo/ginkgo.hpp

@@ -60,6 +60,7 @@
 
 #include <ginkgo/core/distributed/base.hpp>
 #include <ginkgo/core/distributed/index_map.hpp>
+#include <ginkgo/core/distributed/index_map_fwd.hpp>
 #include <ginkgo/core/distributed/lin_op.hpp>
 #include <ginkgo/core/distributed/matrix.hpp>
 #include <ginkgo/core/distributed/partition.hpp>