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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/detail/config.h>
#include <cusp/array1d.h>
#include <cusp/exception.h>
#include <cusp/graph/pseudo_peripheral.h>
#include <thrust/copy.h>
#include <thrust/gather.h>
#include <thrust/iterator/counting_iterator.h>
namespace cusp
{
namespace graph
{
namespace detail
{
template<typename MatrixType, typename ArrayType>
void symmetric_rcm(MatrixType& G, ArrayType& permutation, cusp::csr_format)
{
typedef typename MatrixType::index_type IndexType;
typedef typename MatrixType::value_type ValueType;
typedef typename MatrixType::memory_space MemorySpace;
// find peripheral vertex and return BFS levels from vertex
cusp::graph::pseudo_peripheral_vertex(G, permutation);
// sort vertices by level in BFS traversal
cusp::array1d<IndexType,MemorySpace> levels(G.num_rows);
thrust::sequence(levels.begin(), levels.end());
thrust::sort_by_key(permutation.begin(), permutation.end(), levels.begin());
// form RCM permutation matrix
thrust::scatter(thrust::counting_iterator<IndexType>(0),
thrust::counting_iterator<IndexType>(G.num_rows),
levels.begin(), permutation.begin());
// expand offsets to indices
cusp::array1d<IndexType,MemorySpace> row_indices(G.num_entries);
cusp::detail::offsets_to_indices(G.row_offsets, row_indices);
// reorder rows and column according to permutation
thrust::gather(row_indices.begin(), row_indices.end(), permutation.begin(), row_indices.begin());
thrust::gather(G.column_indices.begin(), G.column_indices.end(), permutation.begin(), G.column_indices.begin());
// order COO matrix
cusp::detail::sort_by_row_and_column(row_indices, G.column_indices, G.values);
// update row_offsets to match reordering
cusp::detail::indices_to_offsets(row_indices, G.row_offsets);
}
//////////////////
// General Path //
//////////////////
template<typename MatrixType, typename ArrayType, typename Format>
void symmetric_rcm(MatrixType& G, ArrayType& permutation, Format& format)
{
typedef typename MatrixType::index_type IndexType;
typedef typename MatrixType::value_type ValueType;
typedef typename MatrixType::memory_space MemorySpace;
// convert matrix to CSR format and compute on the host
cusp::csr_matrix<IndexType,ValueType,MemorySpace> G_csr(G);
G = cusp::graph::symmetric_rcm(G_csr, permutation);
}
} // end namespace detail
/////////////////
// Entry Point //
/////////////////
template<typename MatrixType>
void symmetric_rcm(MatrixType& G)
{
typedef typename MatrixType::index_type IndexType;
typedef typename MatrixType::memory_space MemorySpace;
CUSP_PROFILE_SCOPED();
cusp::array1d<IndexType,MemorySpace> permutation(G.num_rows);
cusp::graph::symmetric_rcm(G, permutation);
}
template<typename MatrixType, typename ArrayType>
void symmetric_rcm(MatrixType& G, ArrayType& permutation)
{
CUSP_PROFILE_SCOPED();
if(G.num_rows != G.num_cols)
throw cusp::invalid_input_exception("matrix must be square");
cusp::graph::detail::symmetric_rcm(G, permutation, typename MatrixType::format());
}
} // end namespace graph
} // end namespace cusp
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