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jnke2016jnke2016
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add C implementation of MST (#5044)
This PR adds the C, PLC and python API for Minimum Spanning Tree closes #4882 Authors: - Joseph Nke (https://github.com/jnke2016) Approvers: - Rick Ratzel (https://github.com/rlratzel) - Chuck Hastings (https://github.com/ChuckHastings) URL: #5044
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‎cpp/CMakeLists.txt‎

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@@ -554,6 +554,7 @@ add_library(cugraph_c
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src/c_api/edgelist.cpp
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src/c_api/renumber_arbitrary_edgelist.cu
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src/c_api/legacy_fa2.cpp
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src/c_api/legacy_mst.cpp
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)
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add_library(cugraph::cugraph_c ALIAS cugraph_c)
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‎cpp/include/cugraph_c/algorithms.h‎

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/*
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* Copyright (c) 2024, NVIDIA CORPORATION.
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* Copyright (c) 2024-2025, NVIDIA CORPORATION.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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#include <cugraph_c/sampling_algorithms.h>
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#include <cugraph_c/similarity_algorithms.h>
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#include <cugraph_c/traversal_algorithms.h>
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#include <cugraph_c/tree_algorithms.h>
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/**
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* @}
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*/

‎cpp/include/cugraph_c/tree_algorithms.h‎

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/*
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* Copyright (c) 2025, NVIDIA CORPORATION.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <cugraph_c/error.h>
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#include <cugraph_c/graph.h>
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#include <cugraph_c/graph_functions.h>
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#include <cugraph_c/random.h>
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#include <cugraph_c/resource_handle.h>
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/** @defgroup layout Layout algorithms
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*/
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* @brief Opaque layout output
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*/
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typedef struct {
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int32_t align_;
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} cugraph_layout_result_t;
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/**
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* @brief Minimum Spanning Tree
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*
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* NOTE: This currently wraps the legacy minimum implementation and is only
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* available in Single GPU implementation.
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*
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* @param [in] handle Handle for accessing resources
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* @param [in] graph Pointer to graph. NOTE: Graph might be modified if the storage
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* needs to be transposed
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* @param [in] do_expensive_check
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* A flag to run expensive checks for input arguments (if set to true)
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* @param [out] result Opaque object containing the extracted subgraph
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* @param [out] error Pointer to an error object storing details of any error. Will
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* be populated if error code is not CUGRAPH_SUCCESS
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* @return error code
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*/
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cugraph_error_code_t cugraph_minimum_spanning_tree(const cugraph_resource_handle_t* handle,
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cugraph_graph_t* graph,
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bool_t do_expensive_check,
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cugraph_induced_subgraph_result_t** result,
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cugraph_error_t** error);
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#ifdef __cplusplus
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}
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#endif

‎cpp/src/c_api/legacy_mst.cpp‎

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/*
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* Copyright (c) 2025, NVIDIA CORPORATION.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "c_api/abstract_functor.hpp"
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#include "c_api/capi_helper.hpp"
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#include "c_api/graph.hpp"
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#include "c_api/induced_subgraph_result.hpp"
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#include "c_api/random.hpp"
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#include "c_api/resource_handle.hpp"
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#include "c_api/utils.hpp"
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#include <cugraph_c/algorithms.h>
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#include <cugraph/algorithms.hpp>
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#include <cugraph/detail/utility_wrappers.hpp>
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#include <cugraph/graph_functions.hpp>
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#include <optional>
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namespace {
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struct minimum_spanning_tree_functor : public cugraph::c_api::abstract_functor {
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raft::handle_t const& handle_;
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cugraph::c_api::cugraph_graph_t* graph_{nullptr};
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bool do_expensive_check_{};
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cugraph::c_api::cugraph_induced_subgraph_result_t* result_{};
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;
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minimum_spanning_tree_functor(::cugraph_resource_handle_t const* handle,
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::cugraph_graph_t* graph,
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bool do_expensive_check)
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: abstract_functor(),
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handle_(*reinterpret_cast<cugraph::c_api::cugraph_resource_handle_t const*>(handle)->handle_),
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graph_(reinterpret_cast<cugraph::c_api::cugraph_graph_t*>(graph)),
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do_expensive_check_(do_expensive_check)
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{
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}
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template <typename vertex_t,
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typename edge_t,
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typename weight_t,
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typename edge_type_type_t,
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bool store_transposed,
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bool multi_gpu>
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void operator()()
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{
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if constexpr (!cugraph::is_candidate<vertex_t, edge_t, weight_t>::value) {
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unsupported();
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} else if constexpr (multi_gpu) {
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unsupported();
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} else if constexpr (!std::is_same_v<edge_t, int32_t>) {
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unsupported();
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} else {
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auto graph =
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reinterpret_cast<cugraph::graph_t<vertex_t, edge_t, false, false>*>(graph_->graph_);
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auto edge_weights =
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reinterpret_cast<cugraph::edge_property_t<edge_t, weight_t>*>(graph_->edge_weights_);
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auto number_map = reinterpret_cast<rmm::device_uvector<vertex_t>*>(graph_->number_map_);
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auto graph_view = graph->view();
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auto edge_partition_view = graph_view.local_edge_partition_view();
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rmm::device_uvector<weight_t> tmp_weights(0, handle_.get_stream());
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if (edge_weights == nullptr) {
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tmp_weights.resize(edge_partition_view.indices().size(), handle_.get_stream());
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cugraph::detail::scalar_fill(handle_, tmp_weights.data(), tmp_weights.size(), weight_t{1});
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}
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cugraph::legacy::GraphCSRView<vertex_t, edge_t, weight_t> legacy_csr_graph_view(
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const_cast<edge_t*>(edge_partition_view.offsets().data()),
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const_cast<vertex_t*>(edge_partition_view.indices().data()),
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(edge_weights == nullptr)
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? tmp_weights.data()
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: const_cast<weight_t*>(edge_weights->view().value_firsts().front()),
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edge_partition_view.offsets().size() - 1,
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edge_partition_view.indices().size());
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auto result_legacy_coo_graph =
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cugraph::minimum_spanning_tree<vertex_t, edge_t, weight_t>(handle_, legacy_csr_graph_view);
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const size_t num_edges = result_legacy_coo_graph->view().number_of_edges;
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// FIXME: Add new constructor for cugraph_type_erased_host_array_t that takes an
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// rmm::device_buffer with the goa of skipping copies
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rmm::device_uvector<vertex_t> result_src(num_edges, handle_.get_stream());
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raft::copy(result_src.data(),
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result_legacy_coo_graph->view().src_indices,
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result_src.size(),
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handle_.get_stream());
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rmm::device_uvector<vertex_t> result_dst(num_edges, handle_.get_stream());
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raft::copy(result_dst.data(),
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result_legacy_coo_graph->view().dst_indices,
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result_dst.size(),
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handle_.get_stream());
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std::optional<rmm::device_uvector<weight_t>> result_wgt{std::nullopt};
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result_wgt = rmm::device_uvector<weight_t>{num_edges, handle_.get_stream()};
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raft::copy(result_wgt->data(),
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result_legacy_coo_graph->view().edge_data,
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result_wgt->size(),
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handle_.get_stream());
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cugraph::unrenumber_int_vertices<vertex_t, multi_gpu>(
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handle_,
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result_src.data(),
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result_src.size(),
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number_map->data(),
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graph_view.vertex_partition_range_lasts(),
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do_expensive_check_);
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cugraph::unrenumber_int_vertices<vertex_t, multi_gpu>(
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handle_,
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result_dst.data(),
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result_dst.size(),
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number_map->data(),
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graph_view.vertex_partition_range_lasts(),
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do_expensive_check_);
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rmm::device_uvector<size_t> edge_offsets(2, handle_.get_stream());
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std::vector<size_t> h_edge_offsets{{0, num_edges}};
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raft::update_device(
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edge_offsets.data(), h_edge_offsets.data(), h_edge_offsets.size(), handle_.get_stream());
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// FIXME: Add support for edge_id and edge_type_id.
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result_ = new cugraph::c_api::cugraph_induced_subgraph_result_t{
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new cugraph::c_api::cugraph_type_erased_device_array_t(result_src, graph_->vertex_type_),
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new cugraph::c_api::cugraph_type_erased_device_array_t(result_dst, graph_->vertex_type_),
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result_wgt ? new cugraph::c_api::cugraph_type_erased_device_array_t(*result_wgt,
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graph_->weight_type_)
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: NULL,
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NULL,
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NULL,
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new cugraph::c_api::cugraph_type_erased_device_array_t(edge_offsets,
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cugraph_data_type_id_t::SIZE_T)};
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}
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}
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};
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} // namespace
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extern "C" cugraph_error_code_t cugraph_minimum_spanning_tree(
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const cugraph_resource_handle_t* handle,
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cugraph_graph_t* graph,
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bool_t do_expensive_check,
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cugraph_induced_subgraph_result_t** result,
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cugraph_error_t** error)
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{
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minimum_spanning_tree_functor functor(handle, graph, do_expensive_check);
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return cugraph::c_api::run_algorithm(graph, functor, result, error);
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}

‎cpp/tests/CMakeLists.txt‎

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ConfigureCTest(CAPI_EGONET_TEST c_api/egonet_test.c)
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ConfigureCTest(CAPI_TWO_HOP_NEIGHBORS_TEST c_api/two_hop_neighbors_test.c)
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ConfigureCTest(CAPI_K_TRUSS_TEST c_api/k_truss_test.c)
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ConfigureCTest(CAPI_MST_TEST c_api/legacy_mst_test.c)
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if (BUILD_CUGRAPH_MTMG_TESTS)
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###################################################################################################

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