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/*
* Copyright 2008-2009 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 <cusp/exception.h>
#include <cusp/array1d.h>
#include <cusp/graph/breadth_first_search.h>
#include <thrust/scatter.h>
#include <thrust/iterator/constant_iterator.h>
namespace cusp
{
namespace graph
{
namespace detail
{
namespace device
{
template<typename MatrixType, typename ArrayType>
size_t connected_components(const MatrixType& G, ArrayType& components)
{
using namespace thrust::placeholders;
typedef typename MatrixType::index_type VertexId;
const VertexId UNSET = -1;
size_t num_components = 0;
VertexId num_rows = G.num_rows;
thrust::fill(components.begin(), components.end(), UNSET);
ArrayType levels(G.num_rows, UNSET);
VertexId src = rand() % G.num_rows;
while(src < num_rows) {
cusp::graph::breadth_first_search<false>(G, src, levels);
thrust::transform_if( thrust::constant_iterator<VertexId>(num_components),
thrust::constant_iterator<VertexId>(num_components) + G.num_rows,
levels.begin(), components.begin(), thrust::identity<VertexId>(), _1 != UNSET );
thrust::fill(levels.begin(), levels.end(), UNSET);
src = thrust::find(components.begin(), components.end(), UNSET) - components.begin();
num_components++;
}
return num_components;
}
} // end namespace device
} // end namespace detail
} // end namespace graph
} // end namespace cusp
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