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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.
*/
/*! \file diagonal.inl
* \brief Inline file for diagonal.h
*/
#include <cusp/blas.h>
#include <cusp/detail/format_utils.h>
#include <thrust/functional.h>
#include <thrust/transform.h>
namespace cusp
{
namespace precond
{
namespace detail
{
template <typename T>
struct reciprocal : public thrust::unary_function<T,T>
{
__host__ __device__
T operator()(const T& v)
{
return T(1.0) / v;
}
};
} // end namespace detail
// constructor
template <typename ValueType, typename MemorySpace>
template<typename MatrixType>
diagonal<ValueType,MemorySpace>
::diagonal(const MatrixType& A)
: linear_operator<ValueType,MemorySpace>(A.num_rows, A.num_cols, A.num_rows)
{
// extract the main diagonal
cusp::detail::extract_diagonal(A, diagonal_reciprocals);
// invert the entries
thrust::transform(diagonal_reciprocals.begin(), diagonal_reciprocals.end(),
diagonal_reciprocals.begin(), detail::reciprocal<ValueType>());
}
// linear operator
template <typename ValueType, typename MemorySpace>
template <typename VectorType1, typename VectorType2>
void diagonal<ValueType, MemorySpace>
::operator()(const VectorType1& x, VectorType2& y) const
{
cusp::blas::xmy(diagonal_reciprocals, x, y);
}
} // end namespace precond
} // end namespace cusp
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