* make LU::kernel() and LU::image() also use ReturnByValue

* make them return zero vector in the degenerate case, instead of asserting
  (let's stick to the principle that we only assert on memory errors)
This commit is contained in:
Benoit Jacob 2009-09-22 00:16:51 -04:00
parent 0ad3494bd3
commit 4f9e270343
3 changed files with 229 additions and 211 deletions

View File

@ -51,9 +51,9 @@ struct ei_nested<ReturnByValue<Derived>, n, PlainMatrixType>
template<typename Derived>
class ReturnByValue : public MatrixBase<ReturnByValue<Derived> >
{
typedef typename ei_traits<Derived>::ReturnMatrixType ReturnMatrixType;
public:
EIGEN_GENERIC_PUBLIC_INTERFACE(ReturnByValue)
typedef typename ei_traits<Derived>::ReturnMatrixType ReturnMatrixType;
template<typename Dest>
inline void evalTo(Dest& dst) const
{ static_cast<const Derived* const>(this)->evalTo(dst); }

View File

@ -26,88 +26,8 @@
#define EIGEN_LU_H
template<typename MatrixType, typename Rhs> struct ei_lu_solve_impl;
template<typename MatrixType,typename Rhs>
struct ei_traits<ei_lu_solve_impl<MatrixType,Rhs> >
{
typedef Matrix<typename Rhs::Scalar,
MatrixType::ColsAtCompileTime,
Rhs::ColsAtCompileTime,
Rhs::PlainMatrixType::Options,
MatrixType::MaxColsAtCompileTime,
Rhs::MaxColsAtCompileTime> ReturnMatrixType;
};
template<typename MatrixType, typename Rhs>
struct ei_lu_solve_impl : public ReturnByValue<ei_lu_solve_impl<MatrixType, Rhs> >
{
typedef typename ei_cleantype<typename Rhs::Nested>::type RhsNested;
typedef LU<MatrixType> LUType;
ei_lu_solve_impl(const LUType& lu, const Rhs& rhs)
: m_lu(lu), m_rhs(rhs)
{}
inline int rows() const { return m_lu.matrixLU().cols(); }
inline int cols() const { return m_rhs.cols(); }
template<typename Dest> void evalTo(Dest& dst) const
{
dst.resize(m_lu.matrixLU().cols(), m_rhs.cols());
if(m_lu.rank()==0)
{
dst.setZero();
return;
}
/* The decomposition PAQ = LU can be rewritten as A = P^{-1} L U Q^{-1}.
* So we proceed as follows:
* Step 1: compute c = P * rhs.
* Step 2: replace c by the solution x to Lx = c. Exists because L is invertible.
* Step 3: replace c by the solution x to Ux = c. May or may not exist.
* Step 4: result = Q * c;
*/
const int rows = m_lu.matrixLU().rows(),
cols = m_lu.matrixLU().cols(),
rank = m_lu.rank();
ei_assert(m_rhs.rows() == rows);
const int smalldim = std::min(rows, cols);
typename Rhs::PlainMatrixType c(m_rhs.rows(), m_rhs.cols());
// Step 1
for(int i = 0; i < rows; ++i)
c.row(m_lu.permutationP().coeff(i)) = m_rhs.row(i);
// Step 2
m_lu.matrixLU()
.corner(Eigen::TopLeft,smalldim,smalldim)
.template triangularView<UnitLowerTriangular>()
.solveInPlace(c.corner(Eigen::TopLeft, smalldim, c.cols()));
if(rows>cols)
{
c.corner(Eigen::BottomLeft, rows-cols, c.cols())
-= m_lu.matrixLU().corner(Eigen::BottomLeft, rows-cols, cols)
* c.corner(Eigen::TopLeft, cols, c.cols());
}
// Step 3
m_lu.matrixLU()
.corner(TopLeft, rank, rank)
.template triangularView<UpperTriangular>()
.solveInPlace(c.corner(TopLeft, rank, c.cols()));
// Step 4
for(int i = 0; i < rank; ++i)
dst.row(m_lu.permutationQ().coeff(i)) = c.row(i);
for(int i = rank; i < m_lu.matrixLU().cols(); ++i)
dst.row(m_lu.permutationQ().coeff(i)).setZero();
}
const LUType& m_lu;
const typename Rhs::Nested m_rhs;
};
template<typename MatrixType> struct ei_lu_kernel_impl;
template<typename MatrixType> struct ei_lu_image_impl;
/** \ingroup LU_Module
*
@ -156,25 +76,6 @@ template<typename MatrixType> class LU
MatrixType::MaxRowsAtCompileTime)
};
typedef Matrix<typename MatrixType::Scalar,
MatrixType::ColsAtCompileTime, // the number of rows in the "kernel matrix" is the number of cols of the original matrix
// so that the product "matrix * kernel = zero" makes sense
Dynamic, // we don't know at compile-time the dimension of the kernel
MatrixType::Options,
MatrixType::MaxColsAtCompileTime, // see explanation for 2nd template parameter
MatrixType::MaxColsAtCompileTime // the kernel is a subspace of the domain space, whose dimension is the number
// of columns of the original matrix
> KernelResultType;
typedef Matrix<typename MatrixType::Scalar,
MatrixType::RowsAtCompileTime, // the image is a subspace of the destination space, whose
// dimension is the number of rows of the original matrix
Dynamic, // we don't know at compile time the dimension of the image (the rank)
MatrixType::Options,
MatrixType::MaxRowsAtCompileTime, // the image matrix will consist of columns from the original matrix,
MatrixType::MaxColsAtCompileTime // so it has the same number of rows and at most as many columns.
> ImageResultType;
/**
* \brief Default Constructor.
*
@ -210,7 +111,15 @@ template<typename MatrixType> class LU
ei_assert(m_originalMatrix != 0 && "LU is not initialized.");
return m_lu;
}
/** \returns a pointer to the matrix of which *this is the LU decomposition.
*/
inline const MatrixType* originalMatrix() const
{
ei_assert(m_originalMatrix != 0 && "LU is not initialized.");
return m_originalMatrix;
}
/** \returns a vector of integers, whose size is the number of rows of the matrix being decomposed,
* representing the P permutation i.e. the permutation of the rows. For its precise meaning,
* see the examples given in the documentation of class LU.
@ -235,69 +144,37 @@ template<typename MatrixType> class LU
return m_q;
}
/** Computes a basis of the kernel of the matrix, also called the null-space of the matrix.
*
* \note This method is only allowed on non-invertible matrices, as determined by
* isInvertible(). Calling it on an invertible matrix will make an assertion fail.
*
* \param result a pointer to the matrix in which to store the kernel. The columns of this
* matrix will be set to form a basis of the kernel (it will be resized
* if necessary).
*
* Example: \include LU_computeKernel.cpp
* Output: \verbinclude LU_computeKernel.out
*
* \sa kernel(), computeImage(), image()
*/
template<typename KernelMatrixType>
void computeKernel(KernelMatrixType *result) const;
/** Computes a basis of the image of the matrix, also called the column-space or range of he matrix.
*
* \note Calling this method on the zero matrix will make an assertion fail.
*
* \param result a pointer to the matrix in which to store the image. The columns of this
* matrix will be set to form a basis of the image (it will be resized
* if necessary).
*
* Example: \include LU_computeImage.cpp
* Output: \verbinclude LU_computeImage.out
*
* \sa image(), computeKernel(), kernel()
*/
template<typename ImageMatrixType>
void computeImage(ImageMatrixType *result) const;
/** \returns the kernel of the matrix, also called its null-space. The columns of the returned matrix
* will form a basis of the kernel.
*
* \note: this method is only allowed on non-invertible matrices, as determined by
* isInvertible(). Calling it on an invertible matrix will make an assertion fail.
*
* \note: this method returns a matrix by value, which induces some inefficiency.
* If you prefer to avoid this overhead, use computeKernel() instead.
* \note If the kernel has dimension zero, then the returned matrix is a column-vector filled with zeros.
*
* Example: \include LU_kernel.cpp
* Output: \verbinclude LU_kernel.out
*
* \sa computeKernel(), image()
* \sa image()
*/
const KernelResultType kernel() const;
inline const ei_lu_kernel_impl<MatrixType> kernel() const
{
ei_assert(m_originalMatrix != 0 && "LU is not initialized.");
return ei_lu_kernel_impl<MatrixType>(*this);
}
/** \returns the image of the matrix, also called its column-space. The columns of the returned matrix
* will form a basis of the kernel.
*
* \note: Calling this method on the zero matrix will make an assertion fail.
*
* \note: this method returns a matrix by value, which induces some inefficiency.
* If you prefer to avoid this overhead, use computeImage() instead.
* \note If the image has dimension zero, then the returned matrix is a column-vector filled with zeros.
*
* Example: \include LU_image.cpp
* Output: \verbinclude LU_image.out
*
* \sa computeImage(), kernel()
* \sa kernel()
*/
const ImageResultType image() const;
inline const ei_lu_image_impl<MatrixType> image() const
{
ei_assert(m_originalMatrix != 0 && "LU is not initialized.");
return ei_lu_image_impl<MatrixType>(*this);
}
/** This method returns a solution x to the equation Ax=b, where A is the matrix of which
* *this is the LU decomposition.
@ -316,7 +193,7 @@ template<typename MatrixType> class LU
* Example: \include LU_solve.cpp
* Output: \verbinclude LU_solve.out
*
* \sa TriangularView::solve(), kernel(), computeKernel(), inverse(), computeInverse()
* \sa TriangularView::solve(), kernel(), inverse(), computeInverse()
*/
template<typename Rhs>
inline const ei_lu_solve_impl<MatrixType, Rhs>
@ -547,71 +424,213 @@ typename ei_traits<MatrixType>::Scalar LU<MatrixType>::determinant() const
return Scalar(m_det_pq) * m_lu.diagonal().prod();
}
template<typename MatrixType>
template<typename KernelMatrixType>
void LU<MatrixType>::computeKernel(KernelMatrixType *result) const
{
ei_assert(m_originalMatrix != 0 && "LU is not initialized.");
const int dimker = dimensionOfKernel(), cols = m_lu.cols();
result->resize(cols, dimker);
/********* Implementation of kernel() **************************************************/
/* Let us use the following lemma:
*
* Lemma: If the matrix A has the LU decomposition PAQ = LU,
* then Ker A = Q(Ker U).
*
* Proof: trivial: just keep in mind that P, Q, L are invertible.
template<typename MatrixType>
struct ei_traits<ei_lu_kernel_impl<MatrixType> >
{
typedef Matrix<
typename MatrixType::Scalar,
MatrixType::ColsAtCompileTime, // the number of rows in the "kernel matrix"
// is the number of cols of the original matrix
// so that the product "matrix * kernel = zero" makes sense
Dynamic, // we don't know at compile-time the dimension of the kernel
MatrixType::Options,
MatrixType::MaxColsAtCompileTime, // see explanation for 2nd template parameter
MatrixType::MaxColsAtCompileTime // the kernel is a subspace of the domain space,
// whose dimension is the number of columns of the original matrix
> ReturnMatrixType;
};
template<typename MatrixType>
struct ei_lu_kernel_impl : public ReturnByValue<ei_lu_kernel_impl<MatrixType> >
{
typedef LU<MatrixType> LUType;
const LUType& m_lu;
int m_dimKer;
ei_lu_kernel_impl(const LUType& lu) : m_lu(lu), m_dimKer(lu.dimensionOfKernel()) {}
inline int rows() const { return m_lu.matrixLU().cols(); }
inline int cols() const { return m_dimKer; }
template<typename Dest> void evalTo(Dest& dst) const
{
typedef typename MatrixType::Scalar Scalar;
const int rank = m_lu.rank(),
cols = m_lu.matrixLU().cols();
if(m_dimKer == 0)
{
// The Kernel is just {0}, so it doesn't have a basis properly speaking, but let's
// avoid crashing/asserting as that depends on floating point calculations. Let's
// just return a single column vector filled with zeros.
dst.resize(cols,1);
dst.setZero();
return;
}
/* Let us use the following lemma:
*
* Lemma: If the matrix A has the LU decomposition PAQ = LU,
* then Ker A = Q(Ker U).
*
* Proof: trivial: just keep in mind that P, Q, L are invertible.
*/
/* Thus, all we need to do is to compute Ker U, and then apply Q.
*
* U is upper triangular, with eigenvalues sorted so that any zeros appear at the end.
* Thus, the diagonal of U ends with exactly
* m_dimKer zero's. Let us use that to construct dimKer linearly
* independent vectors in Ker U.
*/
dst.resize(cols, m_dimKer);
Matrix<typename MatrixType::Scalar, Dynamic, Dynamic, MatrixType::Options,
MatrixType::MaxColsAtCompileTime, MatrixType::MaxColsAtCompileTime>
y(-m_lu.matrixLU().corner(TopRight, rank, m_dimKer));
m_lu.matrixLU()
.corner(TopLeft, rank, rank)
.template triangularView<UpperTriangular>().solveInPlace(y);
for(int i = 0; i < rank; ++i) dst.row(m_lu.permutationQ().coeff(i)) = y.row(i);
for(int i = rank; i < cols; ++i) dst.row(m_lu.permutationQ().coeff(i)).setZero();
for(int k = 0; k < m_dimKer; ++k) dst.coeffRef(m_lu.permutationQ().coeff(rank+k), k) = Scalar(1);
}
};
/***** Implementation of image() *****************************************************/
template<typename MatrixType>
struct ei_traits<ei_lu_image_impl<MatrixType> >
{
typedef Matrix<
typename MatrixType::Scalar,
MatrixType::RowsAtCompileTime, // the image is a subspace of the destination space, whose
// dimension is the number of rows of the original matrix
Dynamic, // we don't know at compile time the dimension of the image (the rank)
MatrixType::Options,
MatrixType::MaxRowsAtCompileTime, // the image matrix will consist of columns from the original matrix,
MatrixType::MaxColsAtCompileTime // so it has the same number of rows and at most as many columns.
> ReturnMatrixType;
};
template<typename MatrixType>
struct ei_lu_image_impl : public ReturnByValue<ei_lu_image_impl<MatrixType> >
{
typedef LU<MatrixType> LUType;
const LUType& m_lu;
ei_lu_image_impl(const LUType& lu) : m_lu(lu) {}
inline int rows() const { return m_lu.matrixLU().cols(); }
inline int cols() const { return m_lu.rank(); }
template<typename Dest> void evalTo(Dest& dst) const
{
int rank = m_lu.rank();
if(rank == 0)
{
// The Image is just {0}, so it doesn't have a basis properly speaking, but let's
// avoid crashing/asserting as that depends on floating point calculations. Let's
// just return a single column vector filled with zeros.
dst.resize(m_lu.originalMatrix()->rows(), 1);
dst.setZero();
return;
}
dst.resize(m_lu.originalMatrix()->rows(), rank);
for(int i = 0; i < rank; ++i)
dst.col(i) = m_lu.originalMatrix()->col(m_lu.permutationQ().coeff(i));
}
};
/***** Implementation of solve() *****************************************************/
template<typename MatrixType,typename Rhs>
struct ei_traits<ei_lu_solve_impl<MatrixType,Rhs> >
{
typedef Matrix<typename Rhs::Scalar,
MatrixType::ColsAtCompileTime,
Rhs::ColsAtCompileTime,
Rhs::PlainMatrixType::Options,
MatrixType::MaxColsAtCompileTime,
Rhs::MaxColsAtCompileTime> ReturnMatrixType;
};
template<typename MatrixType, typename Rhs>
struct ei_lu_solve_impl : public ReturnByValue<ei_lu_solve_impl<MatrixType, Rhs> >
{
typedef typename ei_cleantype<typename Rhs::Nested>::type RhsNested;
typedef LU<MatrixType> LUType;
const LUType& m_lu;
const typename Rhs::Nested m_rhs;
ei_lu_solve_impl(const LUType& lu, const Rhs& rhs)
: m_lu(lu), m_rhs(rhs)
{}
inline int rows() const { return m_lu.matrixLU().cols(); }
inline int cols() const { return m_rhs.cols(); }
template<typename Dest> void evalTo(Dest& dst) const
{
dst.resize(m_lu.matrixLU().cols(), m_rhs.cols());
if(m_lu.rank()==0)
{
dst.setZero();
return;
}
/* The decomposition PAQ = LU can be rewritten as A = P^{-1} L U Q^{-1}.
* So we proceed as follows:
* Step 1: compute c = P * rhs.
* Step 2: replace c by the solution x to Lx = c. Exists because L is invertible.
* Step 3: replace c by the solution x to Ux = c. May or may not exist.
* Step 4: result = Q * c;
*/
/* Thus, all we need to do is to compute Ker U, and then apply Q.
*
* U is upper triangular, with eigenvalues sorted so that any zeros appear at the end.
* Thus, the diagonal of U ends with exactly
* m_dimKer zero's. Let us use that to construct m_dimKer linearly
* independent vectors in Ker U.
*/
const int rows = m_lu.matrixLU().rows(),
cols = m_lu.matrixLU().cols(),
rank = m_lu.rank();
ei_assert(m_rhs.rows() == rows);
const int smalldim = std::min(rows, cols);
Matrix<Scalar, Dynamic, Dynamic, MatrixType::Options,
MatrixType::MaxColsAtCompileTime, MatrixType::MaxColsAtCompileTime>
y(-m_lu.corner(TopRight, m_rank, dimker));
typename Rhs::PlainMatrixType c(m_rhs.rows(), m_rhs.cols());
m_lu.corner(TopLeft, m_rank, m_rank)
.template triangularView<UpperTriangular>().solveInPlace(y);
// Step 1
for(int i = 0; i < rows; ++i)
c.row(m_lu.permutationP().coeff(i)) = m_rhs.row(i);
for(int i = 0; i < m_rank; ++i) result->row(m_q.coeff(i)) = y.row(i);
for(int i = m_rank; i < cols; ++i) result->row(m_q.coeff(i)).setZero();
for(int k = 0; k < dimker; ++k) result->coeffRef(m_q.coeff(m_rank+k), k) = Scalar(1);
}
// Step 2
m_lu.matrixLU()
.corner(Eigen::TopLeft,smalldim,smalldim)
.template triangularView<UnitLowerTriangular>()
.solveInPlace(c.corner(Eigen::TopLeft, smalldim, c.cols()));
if(rows>cols)
{
c.corner(Eigen::BottomLeft, rows-cols, c.cols())
-= m_lu.matrixLU().corner(Eigen::BottomLeft, rows-cols, cols)
* c.corner(Eigen::TopLeft, cols, c.cols());
}
template<typename MatrixType>
const typename LU<MatrixType>::KernelResultType
LU<MatrixType>::kernel() const
{
ei_assert(m_originalMatrix != 0 && "LU is not initialized.");
KernelResultType result(m_lu.cols(), dimensionOfKernel());
computeKernel(&result);
return result;
}
// Step 3
m_lu.matrixLU()
.corner(TopLeft, rank, rank)
.template triangularView<UpperTriangular>()
.solveInPlace(c.corner(TopLeft, rank, c.cols()));
template<typename MatrixType>
template<typename ImageMatrixType>
void LU<MatrixType>::computeImage(ImageMatrixType *result) const
{
ei_assert(m_originalMatrix != 0 && "LU is not initialized.");
result->resize(m_originalMatrix->rows(), m_rank);
for(int i = 0; i < m_rank; ++i)
result->col(i) = m_originalMatrix->col(m_q.coeff(i));
}
// Step 4
for(int i = 0; i < rank; ++i)
dst.row(m_lu.permutationQ().coeff(i)) = c.row(i);
for(int i = rank; i < m_lu.matrixLU().cols(); ++i)
dst.row(m_lu.permutationQ().coeff(i)).setZero();
}
};
template<typename MatrixType>
const typename LU<MatrixType>::ImageResultType
LU<MatrixType>::image() const
{
ei_assert(m_originalMatrix != 0 && "LU is not initialized.");
ImageResultType result(m_originalMatrix->rows(), m_rank);
computeImage(&result);
return result;
}
/******* MatrixBase methods *****************************************************************/
/** \lu_module
*

View File

@ -1,7 +1,7 @@
// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2008 Benoit Jacob <jacob.benoit.1@gmail.com>
// Copyright (C) 2008-2009 Benoit Jacob <jacob.benoit.1@gmail.com>
//
// Eigen is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
@ -37,9 +37,10 @@ template<typename MatrixType> void lu_non_invertible()
createRandomMatrixOfRank(rank, rows, cols, m1);
LU<MatrixType> lu(m1);
typename LU<MatrixType>::KernelResultType m1kernel = lu.kernel();
typename LU<MatrixType>::ImageResultType m1image = lu.image();
typename ei_lu_kernel_impl<MatrixType>::ReturnMatrixType m1kernel = lu.kernel();
typename ei_lu_image_impl <MatrixType>::ReturnMatrixType m1image = lu.image();
std::cout << "rows:" << rows << " cols:" << cols << " | " << rank << " ----- " << lu.rank() << std::endl;
VERIFY(rank == lu.rank());
VERIFY(cols - lu.rank() == lu.dimensionOfKernel());
VERIFY(!lu.isInjective());
@ -101,8 +102,6 @@ template<typename MatrixType> void lu_verify_assert()
VERIFY_RAISES_ASSERT(lu.matrixLU())
VERIFY_RAISES_ASSERT(lu.permutationP())
VERIFY_RAISES_ASSERT(lu.permutationQ())
VERIFY_RAISES_ASSERT(lu.computeKernel(&tmp))
VERIFY_RAISES_ASSERT(lu.computeImage(&tmp))
VERIFY_RAISES_ASSERT(lu.kernel())
VERIFY_RAISES_ASSERT(lu.image())
VERIFY_RAISES_ASSERT(lu.solve(tmp))