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83 lines
2.7 KiB
83 lines
2.7 KiB
1 year ago
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// This file is part of libigl, a simple c++ geometry processing library.
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//
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// Copyright (C) 2017 Daniele Panozzo <daniele.panozzo@gmail.com>
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//
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// This Source Code Form is subject to the terms of the Mozilla Public License
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// v. 2.0. If a copy of the MPL was not distributed with this file, You can
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// obtain one at http://mozilla.org/MPL/2.0/.
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#ifndef IGL_ATA_CACHED_H
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#define IGL_ATA_CACHED_H
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#include "igl_inline.h"
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#define EIGEN_YES_I_KNOW_SPARSE_MODULE_IS_NOT_STABLE_YET
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#include <Eigen/Dense>
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#include <Eigen/Sparse>
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namespace igl
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{
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/// Hold precomputed data for AtA_cached
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struct AtA_cached_data
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{
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/// Weights (diagonal of W)
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Eigen::VectorXd W;
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// Flatten composition rules
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/// @private
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std::vector<int> I_row;
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/// @private
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std::vector<int> I_col;
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/// @private
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std::vector<int> I_w;
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// For each entry of AtA, points to the beginning
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// of the composition rules
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/// @private
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std::vector<int> I_outer;
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};
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/// Computes At * W * A, where A is sparse and W is diagonal.
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///
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/// Divides the construction in two phases, one for fixing the sparsity
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/// pattern, and one to populate it with values. Compared to evaluating it
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/// directly, this version is slower for the first time (since it requires a
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/// precomputation), but faster to the subsequent evaluations.
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///
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/// @param[in] A m x n sparse matrix
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/// @param[in,out] data stores the precomputed sparsity pattern, data.W contains the optional diagonal weights (stored as a dense vector). If W is not provided, it is replaced by the identity.
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/// @param[out] AtA m by m matrix computed as AtA * W * A
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///
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/// #### Example:
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///
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/// \code{cpp}
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/// AtA_data = igl::AtA_cached_data();
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/// AtA_data.W = W;
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/// if (s.AtA.rows() == 0)
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/// igl::AtA_cached_precompute(s.A,s.AtA_data,s.AtA);
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/// else
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/// igl::AtA_cached(s.A,s.AtA_data,s.AtA);
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/// \endcode
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template <typename Scalar>
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IGL_INLINE void AtA_cached_precompute(
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const Eigen::SparseMatrix<Scalar>& A,
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AtA_cached_data& data,
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Eigen::SparseMatrix<Scalar>& AtA
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);
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/// Computes At * W * A, where A is sparse and W is diagonal precomputed into data.
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///
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/// @param[in] A m x n sparse matrix
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/// @param[in] data stores the precomputed sparsity pattern, data.W contains the optional diagonal weights (stored as a dense vector). If W is not provided, it is replaced by the identity.
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/// @param[out] AtA m by m matrix computed as AtA * W * A
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template <typename Scalar>
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IGL_INLINE void AtA_cached(
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const Eigen::SparseMatrix<Scalar>& A,
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const AtA_cached_data& data,
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Eigen::SparseMatrix<Scalar>& AtA
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);
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}
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#ifndef IGL_STATIC_LIBRARY
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# include "AtA_cached.cpp"
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#endif
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#endif
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