Define C API for eigenvector centrality

cpp/CMakeLists.txt

@@ -355,6 +355,8 @@ add_library(cugraph_c SHARED
         src/c_api/graph_sg.cpp
         src/c_api/graph_mg.cpp
         src/c_api/pagerank.cpp
+        src/c_api/centrality_result.cpp
+        src/c_api/eigenvector_centrality.cpp
         src/c_api/hits.cpp
         src/c_api/bfs.cpp
         src/c_api/sssp.cpp

cpp/include/cugraph_c/algorithms.h

@@ -25,36 +25,36 @@ extern "C" {
 #endif
 
 /**
- * @brief     Opaque pagerank result type
+ * @brief     Opaque centrality result type
  */
 typedef struct {
   int32_t align_;
-} cugraph_pagerank_result_t;
+} cugraph_centrality_result_t;
 
 /**
- * @brief     Get the vertex ids from the pagerank result
+ * @brief     Get the vertex ids from the centrality result
  *
- * @param [in]   result   The result from pagerank
+ * @param [in]   result   The result from a centrality algorithm
  * @return type erased array of vertex ids
  */
-cugraph_type_erased_device_array_view_t* cugraph_pagerank_result_get_vertices(
-  cugraph_pagerank_result_t* result);
+cugraph_type_erased_device_array_view_t* cugraph_centrality_result_get_vertices(
+  cugraph_centrality_result_t* result);
 
 /**
- * @brief     Get the pagerank values from the pagerank result
+ * @brief     Get the centrality values from a centrality algorithm result
  *
- * @param [in]   result   The result from pagerank
- * @return type erased array of pagerank values
+ * @param [in]   result   The result from a centrality algorithm
+ * @return type erased array view of centrality values
  */
-cugraph_type_erased_device_array_view_t* cugraph_pagerank_result_get_pageranks(
-  cugraph_pagerank_result_t* result);
+cugraph_type_erased_device_array_view_t* cugraph_centrality_result_get_values(
+  cugraph_centrality_result_t* result);
 
 /**
- * @brief     Free pagerank result
+ * @brief     Free centrality result
  *
- * @param [in]   result   The result from pagerank
+ * @param [in]   result   The result from a centrality algorithm
  */
-void cugraph_pagerank_result_free(cugraph_pagerank_result_t* result);
+void cugraph_centrality_result_free(cugraph_centrality_result_t* result);
 
 /**
  * @brief     Compute pagerank
@@ -90,7 +90,7 @@ cugraph_error_code_t cugraph_pagerank(
   size_t max_iterations,
   bool_t has_initial_guess,
   bool_t do_expensive_check,
-  cugraph_pagerank_result_t** result,
+  cugraph_centrality_result_t** result,
   cugraph_error_t** error);
 
 /**
@@ -136,9 +136,35 @@ cugraph_error_code_t cugraph_personalized_pagerank(
   size_t max_iterations,
   bool_t has_initial_guess,
   bool_t do_expensive_check,
-  cugraph_pagerank_result_t** result,
+  cugraph_centrality_result_t** result,
   cugraph_error_t** error);
 
+/**
+ * @brief     Compute eigenvector centrality
+ *
+ * Computed using the power method.
+ *
+ * @param [in]  handle      Handle for accessing resources
+ * @param [in]  graph       Pointer to graph
+ * @param [in]  epsilon     Error tolerance to check convergence. Convergence is measured
+ *                          comparing the L1 norm until it is less than epsilon
+ * @param [in]  max_iterations Maximum number of power iterations, will not exceed this number
+ *                          of iterations even if we haven't converged
+ * @param [in]  do_expensive_check A flag to run expensive checks for input arguments (if set to
+ * `true`).
+ * @param [out] result      Opaque pointer to eigenvector centrality results
+ * @param [out] error       Pointer to an error object storing details of any error.  Will
+ *                          be populated if error code is not CUGRAPH_SUCCESS
+ * @return error code
+ */
+cugraph_error_code_t cugraph_eigenvector_centrality(const cugraph_resource_handle_t* handle,
+                                                    cugraph_graph_t* graph,
+                                                    double epsilon,
+                                                    size_t max_iterations,
+                                                    bool_t do_expensive_check,
+                                                    cugraph_centrality_result_t** result,
+                                                    cugraph_error_t** error);
+
 /**
  * @brief     Opaque hits result type
  */

cpp/src/c_api/centrality_result.cpp

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2022, NVIDIA CORPORATION.
+ *
+ * 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.
+ */
+
+#include <cugraph_c/algorithms.h>
+
+#include <c_api/centrality_result.hpp>
+
+extern "C" cugraph_type_erased_device_array_view_t* cugraph_centrality_result_get_vertices(
+  cugraph_centrality_result_t* result)
+{
+  auto internal_pointer = reinterpret_cast<cugraph::c_api::cugraph_centrality_result_t*>(result);
+  return reinterpret_cast<cugraph_type_erased_device_array_view_t*>(
+    internal_pointer->vertex_ids_->view());
+}
+
+extern "C" cugraph_type_erased_device_array_view_t* cugraph_centrality_result_get_values(
+  cugraph_centrality_result_t* result)
+{
+  auto internal_pointer = reinterpret_cast<cugraph::c_api::cugraph_centrality_result_t*>(result);
+  return reinterpret_cast<cugraph_type_erased_device_array_view_t*>(
+    internal_pointer->values_->view());
+}
+
+extern "C" void cugraph_centrality_result_free(cugraph_centrality_result_t* result)
+{
+  auto internal_pointer = reinterpret_cast<cugraph::c_api::cugraph_centrality_result_t*>(result);
+  delete internal_pointer->vertex_ids_;
+  delete internal_pointer->values_;
+  delete internal_pointer;
+}

cpp/src/c_api/centrality_result.hpp

@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2022, NVIDIA CORPORATION.
+ *
+ * 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 <c_api/array.hpp>
+
+namespace cugraph {
+namespace c_api {
+
+struct cugraph_centrality_result_t {
+  cugraph_type_erased_device_array_t* vertex_ids_{};
+  cugraph_type_erased_device_array_t* values_{};
+};
+
+}  // namespace c_api
+}  // namespace cugraph

cpp/src/c_api/eigenvector_centrality.cpp

@@ -0,0 +1,125 @@
+/*
+ * Copyright (c) 2022, NVIDIA CORPORATION.
+ *
+ * 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.
+ */
+
+#include <cugraph_c/algorithms.h>
+
+#include <c_api/abstract_functor.hpp>
+#include <c_api/centrality_result.hpp>
+#include <c_api/graph.hpp>
+#include <c_api/resource_handle.hpp>
+#include <c_api/utils.hpp>
+
+#include <cugraph/algorithms.hpp>
+#include <cugraph/detail/utility_wrappers.hpp>
+#include <cugraph/graph_functions.hpp>
+
+#include <optional>
+
+namespace {
+
+struct eigenvector_centrality_functor : public cugraph::c_api::abstract_functor {
+  raft::handle_t const& handle_;
+  cugraph::c_api::cugraph_graph_t* graph_{};
+  double epsilon_{};
+  size_t max_iterations_{};
+  bool do_expensive_check_{};
+  cugraph::c_api::cugraph_centrality_result_t* result_{};
+
+  eigenvector_centrality_functor(cugraph_resource_handle_t const* handle,
+                                 cugraph_graph_t* graph,
+                                 double epsilon,
+                                 size_t max_iterations,
+                                 bool do_expensive_check)
+    : abstract_functor(),
+      handle_(*reinterpret_cast<cugraph::c_api::cugraph_resource_handle_t const*>(handle)->handle_),
+      graph_(reinterpret_cast<cugraph::c_api::cugraph_graph_t*>(graph)),
+      epsilon_(epsilon),
+      max_iterations_(max_iterations),
+      do_expensive_check_(do_expensive_check)
+  {
+  }
+
+  template <typename vertex_t,
+            typename edge_t,
+            typename weight_t,
+            bool store_transposed,
+            bool multi_gpu>
+  void operator()()
+  {
+    // FIXME: Think about how to handle SG vice MG
+    if constexpr (!cugraph::is_candidate<vertex_t, edge_t, weight_t>::value) {
+      unsupported();
+    } else {
+      // Eigenvector Centrality expects store_transposed == true
+      if constexpr (!store_transposed) {
+        error_code_ = cugraph::c_api::
+          transpose_storage<vertex_t, edge_t, weight_t, store_transposed, multi_gpu>(
+            handle_, graph_, error_.get());
+        if (error_code_ != CUGRAPH_SUCCESS) return;
+      }
+
+      auto graph = reinterpret_cast<cugraph::graph_t<vertex_t, edge_t, weight_t, true, multi_gpu>*>(
+        graph_->graph_);
+
+      auto graph_view = graph->view();
+
+      auto number_map = reinterpret_cast<rmm::device_uvector<vertex_t>*>(graph_->number_map_);
+
+      rmm::device_uvector<weight_t> centralities(graph_view.get_number_of_local_vertices(),
+                                                 handle_.get_stream());
+
+      // FIXME:  For now we'll call pagerank which returns a similarly formatted thing
+      cugraph::pagerank<vertex_t, edge_t, weight_t, weight_t, multi_gpu>(
+        handle_,
+        graph_view,
+        std::nullopt,
+        std::nullopt,
+        std::nullopt,
+        std::nullopt,
+        centralities.data(),
+        weight_t{0.95},
+        static_cast<weight_t>(epsilon_),
+        max_iterations_,
+        false,
+        do_expensive_check_);
+
+      rmm::device_uvector<vertex_t> vertex_ids(graph_view.get_number_of_local_vertices(),
+                                               handle_.get_stream());
+      raft::copy(vertex_ids.data(), number_map->data(), vertex_ids.size(), handle_.get_stream());
+
+      result_ = new cugraph::c_api::cugraph_centrality_result_t{
+        new cugraph::c_api::cugraph_type_erased_device_array_t(vertex_ids, graph_->vertex_type_),
+        new cugraph::c_api::cugraph_type_erased_device_array_t(centralities, graph_->weight_type_)};
+    }
+  }
+};
+
+}  // namespace
+
+extern "C" cugraph_error_code_t cugraph_eigenvector_centrality(
+  const cugraph_resource_handle_t* handle,
+  cugraph_graph_t* graph,
+  double epsilon,
+  size_t max_iterations,
+  bool_t do_expensive_check,
+  cugraph_centrality_result_t** result,
+  cugraph_error_t** error)
+{
+  eigenvector_centrality_functor functor(
+    handle, graph, epsilon, max_iterations, do_expensive_check);
+
+  return cugraph::c_api::run_algorithm(graph, functor, result, error);
+}