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// This file is part of libigl, a simple c++ geometry processing library.
//
// Copyright (C) 2013 Alec Jacobson <alecjacobson@gmail.com>
//
// This Source Code Form is subject to the terms of the Mozilla Public License
// v. 2.0. If a copy of the MPL was not distributed with this file, You can
// obtain one at http://mozilla.org/MPL/2.0/.
#ifndef IGL_KKT_INVERSE_H
#define IGL_KKT_INVERSE_H
#include "igl_inline.h"
#include <Eigen/Dense>
//// debug
//#include <matlabinterface.h>
//Engine *g_pEngine;
namespace igl
{
/// Constructs the inverse of the KKT matrix of a convex, linear equality
/// constrained quadratic minimization problem.
///
/// Systems of the form:
///
/// / A Aeqᵀ \ / x \ = / b \
/// \ Aeq 0 / \ λ / \ beq /
/// \_____.______/\__.__/ \___.___/
/// M z c
///
/// Arise, for example, when solve convex, linear equality constrained
/// quadratic minimization problems:
///
/// min ½ xᵀ A x - xᵀb subject to Aeq x = beq
///
/// This function constructs a matrix S such that x = S c solves the system
/// above. That is:
///
/// S = [In 0] M⁻¹
///
/// so that
///
/// x = S c
///
/// @tparam T should be a eigen matrix primitive type like float or double
/// @param[in] A n by n matrix of quadratic coefficients
/// @param[in] B n by 1 column of linear coefficients
/// @param[in] Aeq m by n list of linear equality constraint coefficients
/// @param[in] Beq m by 1 list of linear equality constraint constant values
/// @param[in] use_lu_decomposition use lu rather than SVD
/// @param[out] S n by (n + m) "solve" matrix, such that S*[B', Beq'] is a solution
/// @return true on success, false on error
template <typename T>
IGL_INLINE void kkt_inverse(
const Eigen::Matrix<T, Eigen::Dynamic, Eigen::Dynamic>& A,
const Eigen::Matrix<T, Eigen::Dynamic, Eigen::Dynamic>& Aeq,
const bool use_lu_decomposition,
Eigen::Matrix<T, Eigen::Dynamic, Eigen::Dynamic>& S);
}
#ifndef IGL_STATIC_LIBRARY
# include "kkt_inverse.cpp"
#endif
#endif