// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2010 Benoit Jacob <jacob.benoit.1@gmail.com>
// Copyright (C) 2013-2014 Gael Guennebaud <gael.guennebaud@inria.fr>
//
// 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 EIGEN_BIDIAGONALIZATION_H
#define EIGEN_BIDIAGONALIZATION_H
namespace Eigen {
namespace internal {
// UpperBidiagonalization will probably be replaced by a Bidiagonalization class, don't want to make it stable API.
// At the same time, it's useful to keep for now as it's about the only thing that is testing the BandMatrix class.
template<typename _MatrixType> class UpperBidiagonalization
{
public:
typedef _MatrixType MatrixType;
enum {
RowsAtCompileTime = MatrixType::RowsAtCompileTime,
ColsAtCompileTime = MatrixType::ColsAtCompileTime,
ColsAtCompileTimeMinusOne = internal::decrement_size<ColsAtCompileTime>::ret
};
typedef typename MatrixType::Scalar Scalar;
typedef typename MatrixType::RealScalar RealScalar;
typedef Eigen::Index Index; ///< \deprecated since Eigen 3.3
typedef Matrix<Scalar, 1, ColsAtCompileTime> RowVectorType;
typedef Matrix<Scalar, RowsAtCompileTime, 1> ColVectorType;
typedef BandMatrix<RealScalar, ColsAtCompileTime, ColsAtCompileTime, 1, 0, RowMajor> BidiagonalType;
typedef Matrix<Scalar, ColsAtCompileTime, 1> DiagVectorType;
typedef Matrix<Scalar, ColsAtCompileTimeMinusOne, 1> SuperDiagVectorType;
typedef HouseholderSequence<
const MatrixType,
const typename internal::remove_all<typename Diagonal<const MatrixType,0>::ConjugateReturnType>::type
> HouseholderUSequenceType;
typedef HouseholderSequence<
const typename internal::remove_all<typename MatrixType::ConjugateReturnType>::type,
Diagonal<const MatrixType,1>,
OnTheRight
> HouseholderVSequenceType;
/**
* \brief Default Constructor.
*
* The default constructor is useful in cases in which the user intends to
* perform decompositions via Bidiagonalization::compute(const MatrixType&).
*/
UpperBidiagonalization() : m_householder(), m_bidiagonal(), m_isInitialized(false) {}
explicit UpperBidiagonalization(const MatrixType& matrix)
: m_householder(matrix.rows(), matrix.cols()),
m_bidiagonal(matrix.cols(), matrix.cols()),
m_isInitialized(false)
{
compute(matrix);
}
UpperBidiagonalization& compute(const MatrixType& matrix);
UpperBidiagonalization& computeUnblocked(const MatrixType& matrix);
const MatrixType& householder() const { return m_householder; }
const BidiagonalType& bidiagonal() const { return m_bidiagonal; }
const HouseholderUSequenceType householderU() const
{
eigen_assert(m_isInitialized && "UpperBidiagonalization is not initialized.");
return HouseholderUSequenceType(m_householder, m_householder.diagonal().conjugate());
}
const HouseholderVSequenceType householderV() // const here gives nasty errors and i'm lazy
{
eigen_assert(m_isInitialized && "UpperBidiagonalization is not initialized.");
return HouseholderVSequenceType(m_householder.conjugate(), m_householder.const_derived().template diagonal<1>())
.setLength(m_householder.cols()-1)
.setShift(1);
}
protected:
MatrixType m_householder;
BidiagonalType m_bidiagonal;
bool m_isInitialized;
};
// Standard upper bidiagonalization without fancy optimizations
// This version should be faster for small matrix size
template<typename MatrixType>
void upperbidiagonalization_inplace_unblocked(MatrixType& mat,
typename MatrixType::RealScalar *diagonal,
typename MatrixType::RealScalar *upper_diagonal,
typename MatrixType::Scalar* tempData = 0)
{
typedef typename MatrixType::Scalar Scalar;
Index rows = mat.rows();
Index cols = mat.cols();
typedef Matrix<Scalar,Dynamic,1,ColMajor,MatrixType::MaxRowsAtCompileTime,1> TempType;
TempType tempVector;
if(tempData==0)
{
tempVector.resize(rows);
tempData = tempVector.data();
}
for (Index k = 0; /* breaks at k==cols-1 below */ ; ++k)
{
Index remainingRows = rows - k;
Index remainingCols = cols - k - 1;
// construct left householder transform in-place in A
mat.col(k).tail(remainingRows)
.makeHouseholderInPlace(mat.coeffRef(k,k), diagonal[k]);
// apply householder transform to remaining part of A on the left
mat.bottomRightCorner(remainingRows, remainingCols)
.applyHouseholderOnTheLeft(mat.col(k).tail(remainingRows-1), mat.coeff(k,k), tempData);
if(k == cols-1) break;
// construct right householder transform in-place in mat
mat.row(k).tail(remainingCols)
.makeHouseholderInPlace(mat.coeffRef(k,k+1), upper_diagonal[k]);
// apply householder transform to remaining part of mat on the left
mat.bottomRightCorner(remainingRows-1, remainingCols)
.applyHouseholderOnTheRight(mat.row(k).tail(remainingCols-1).transpose(), mat.coeff(k,k+1), tempData);
}
}
/** \internal
* Helper routine for the block reduction to upper bidiagonal form.
*
* Let's partition the matrix A:
*
* | A00 A01 |
* A = | |
* | A10 A11 |
*
* This function reduces to bidiagonal form the left \c rows x \a blockSize vertical panel [A00/A10]
* and the \a blockSize x \c cols horizontal panel [A00 A01] of the matrix \a A. The bottom-right block A11
* is updated using matrix-matrix products:
* A22 -= V * Y^T - X * U^T
* where V and U contains the left and right Householder vectors. U and V are stored in A10, and A01
* respectively, and the update matrices X and Y are computed during the reduction.
*
*/
template<typename MatrixType>
void upperbidiagonalization_blocked_helper(MatrixType& A,
typename MatrixType::RealScalar *diagonal,
typename MatrixType::RealScalar *upper_diagonal,
Index bs,
Ref<Matrix<typename MatrixType::Scalar, Dynamic, Dynamic,
traits<MatrixType>::Flags & RowMajorBit> > X,
Ref<Matrix<typename MatrixType::Scalar, Dynamic, Dynamic,
traits<MatrixType>::Flags & RowMajorBit> > Y)
{
typedef typename MatrixType::Scalar Scalar;
enum { StorageOrder = traits<MatrixType>::Flags & RowMajorBit };
typedef InnerStride<int(StorageOrder) == int(ColMajor) ? 1 : Dynamic> ColInnerStride;
typedef InnerStride<int(StorageOrder) == int(ColMajor) ? Dynamic : 1> RowInnerStride;
typedef Ref<Matrix<Scalar, Dynamic, 1>, 0, ColInnerStride> SubColumnType;
typedef Ref<Matrix<Scalar, 1, Dynamic>, 0, RowInnerStride> SubRowType;
typedef Ref<Matrix<Scalar, Dynamic, Dynamic, StorageOrder > > SubMatType;
Index brows = A.rows();
Index bcols = A.cols();
Scalar tau_u, tau_u_prev(0), tau_v;
for(Index k = 0; k < bs; ++k)
{
Index remainingRows = brows - k;
Index remainingCols = bcols - k - 1;
SubMatType X_k1( X.block(k,0, remainingRows,k) );
SubMatType V_k1( A.block(k,0, remainingRows,k) );
// 1 - update the k-th column of A
SubColumnType v_k = A.col(k).tail(remainingRows);
v_k -= V_k1 * Y.row(k).head(k).adjoint();
if(k) v_k -= X_k1 * A.col(k).head(k);
// 2 - construct left Householder transform in-place
v_k.makeHouseholderInPlace(tau_v, diagonal[k]);
if(k+1<bcols)
{
SubMatType Y_k ( Y.block(k+1,0, remainingCols, k+1) );
SubMatType U_k1 ( A.block(0,k+1, k,remainingCols) );
// this eases the application of Householder transforAions
// A(k,k) will store tau_v later
A(k,k) = Scalar(1);
// 3 - Compute y_k^T = tau_v * ( A^T*v_k - Y_k-1*V_k-1^T*v_k - U_k-1*X_k-1^T*v_k )
{
SubColumnType y_k( Y.col(k).tail(remainingCols) );
// let's use the begining of column k of Y as a temporary vector
SubColumnType tmp( Y.col(k).head(k) );
y_k.noalias() = A.block(k,k+1, remainingRows,remainingCols).adjoint() * v_k; // bottleneck
tmp.noalias() = V_k1.adjoint() * v_k;
y_k.noalias() -= Y_k.leftCols(k) * tmp;
tmp.noalias() = X_k1.adjoint() * v_k;
y_k.noalias() -= U_k1.adjoint() * tmp;
y_k *= numext::conj(tau_v);
}
// 4 - update k-th row of A (it will become u_k)
SubRowType u_k( A.row(k).tail(remainingCols) );
u_k = u_k.conjugate();
{
u_k -= Y_k * A.row(k).head(k+1).adjoint();
if(k) u_k -= U_k1.adjoint() * X.row(k).head(k).adjoint();
}
// 5 - construct right Householder transform in-place
u_k.makeHouseholderInPlace(tau_u, upper_diagonal[k]);
// this eases the application of Householder transformations
// A(k,k+1) will store tau_u later
A(k,k+1) = Scalar(1);
// 6 - Compute x_k = tau_u * ( A*u_k - X_k-1*U_k-1^T*u_k - V_k*Y_k^T*u_k )
{
SubColumnType x_k ( X.col(k).tail(remainingRows-1) );
// let's use the begining of column k of X as a temporary vectors
// note that tmp0 and tmp1 overlaps
SubColumnType tmp0 ( X.col(k).head(k) ),
tmp1 ( X.col(k).head(k+1) );
x_k.noalias() = A.block(k+1,k+1, remainingRows-1,remainingCols) * u_k.transpose(); // bottleneck
tmp0.noalias() = U_k1 * u_k.transpose();
x_k.noalias() -= X_k1.bottomRows(remainingRows-1) * tmp0;
tmp1.noalias() = Y_k.adjoint() * u_k.transpose();
x_k.noalias() -= A.block(k+1,0, remainingRows-1,k+1) * tmp1;
x_k *= numext::conj(tau_u);
tau_u = numext::conj(tau_u);
u_k = u_k.conjugate();
}
if(k>0) A.coeffRef(k-1,k) = tau_u_prev;
tau_u_prev = tau_u;
}
else
A.coeffRef(k-1,k) = tau_u_prev;
A.coeffRef(k,k) = tau_v;
}
if(bs<bcols)
A.coeffRef(bs-1,bs) = tau_u_prev;
// update A22
if(bcols>bs && brows>bs)
{
SubMatType A11( A.bottomRightCorner(brows-bs,bcols-bs) );
SubMatType A10( A.block(bs,0, brows-bs,bs) );
SubMatType A01( A.block(0,bs, bs,bcols-bs) );
Scalar tmp = A01(bs-1,0);
A01(bs-1,0) = 1;
A11.noalias() -= A10 * Y.topLeftCorner(bcols,bs).bottomRows(bcols-bs).adjoint();
A11.noalias() -= X.topLeftCorner(brows,bs).bottomRows(brows-bs) * A01;
A01(bs-1,0) = tmp;
}
}
/** \internal
*
* Implementation of a block-bidiagonal reduction.
* It is based on the following paper:
* The Design of a Parallel Dense Linear Algebra Software Library: Reduction to Hessenberg, Tridiagonal, and Bidiagonal Form.
* by Jaeyoung Choi, Jack J. Dongarra, David W. Walker. (1995)
* section 3.3
*/
template<typename MatrixType, typename BidiagType>
void upperbidiagonalization_inplace_blocked(MatrixType& A, BidiagType& bidiagonal,
Index maxBlockSize=32,
typename MatrixType::Scalar* /*tempData*/ = 0)
{
typedef typename MatrixType::Scalar Scalar;
typedef Block<MatrixType,Dynamic,Dynamic> BlockType;
Index rows = A.rows();
Index cols = A.cols();
Index size = (std::min)(rows, cols);
// X and Y are work space
enum { StorageOrder = traits<MatrixType>::Flags & RowMajorBit };
Matrix<Scalar,
MatrixType::RowsAtCompileTime,
Dynamic,
StorageOrder,
MatrixType::MaxRowsAtCompileTime> X(rows,maxBlockSize);
Matrix<Scalar,
MatrixType::ColsAtCompileTime,
Dynamic,
StorageOrder,
MatrixType::MaxColsAtCompileTime> Y(cols,maxBlockSize);
Index blockSize = (std::min)(maxBlockSize,size);
Index k = 0;
for(k = 0; k < size; k += blockSize)
{
Index bs = (std::min)(size-k,blockSize); // actual size of the block
Index brows = rows - k; // rows of the block
Index bcols = cols - k; // columns of the block
// partition the matrix A:
//
// | A00 A01 A02 |
// | |
// A = | A10 A11 A12 |
// | |
// | A20 A21 A22 |
//
// where A11 is a bs x bs diagonal block,
// and let:
// | A11 A12 |
// B = | |
// | A21 A22 |
BlockType B = A.block(k,k,brows,bcols);
// This stage performs the bidiagonalization of A11, A21, A12, and updating of A22.
// Finally, the algorithm continue on the updated A22.
//
// However, if B is too small, or A22 empty, then let's use an unblocked strategy
if(k+bs==cols || bcols<48) // somewhat arbitrary threshold
{
upperbidiagonalization_inplace_unblocked(B,
&(bidiagonal.template diagonal<0>().coeffRef(k)),
&(bidiagonal.template diagonal<1>().coeffRef(k)),
X.data()
);
break; // We're done
}
else
{
upperbidiagonalization_blocked_helper<BlockType>( B,
&(bidiagonal.template diagonal<0>().coeffRef(k)),
&(bidiagonal.template diagonal<1>().coeffRef(k)),
bs,
X.topLeftCorner(brows,bs),
Y.topLeftCorner(bcols,bs)
);
}
}
}
template<typename _MatrixType>
UpperBidiagonalization<_MatrixType>& UpperBidiagonalization<_MatrixType>::computeUnblocked(const _MatrixType& matrix)
{
Index rows = matrix.rows();
Index cols = matrix.cols();
EIGEN_ONLY_USED_FOR_DEBUG(cols);
eigen_assert(rows >= cols && "UpperBidiagonalization is only for Arices satisfying rows>=cols.");
m_householder = matrix;
ColVectorType temp(rows);
upperbidiagonalization_inplace_unblocked(m_householder,
&(m_bidiagonal.template diagonal<0>().coeffRef(0)),
&(m_bidiagonal.template diagonal<1>().coeffRef(0)),
temp.data());
m_isInitialized = true;
return *this;
}
template<typename _MatrixType>
UpperBidiagonalization<_MatrixType>& UpperBidiagonalization<_MatrixType>::compute(const _MatrixType& matrix)
{
Index rows = matrix.rows();
Index cols = matrix.cols();
EIGEN_ONLY_USED_FOR_DEBUG(rows);
EIGEN_ONLY_USED_FOR_DEBUG(cols);
eigen_assert(rows >= cols && "UpperBidiagonalization is only for Arices satisfying rows>=cols.");
m_householder = matrix;
upperbidiagonalization_inplace_blocked(m_householder, m_bidiagonal);
m_isInitialized = true;
return *this;
}
#if 0
/** \return the Householder QR decomposition of \c *this.
*
* \sa class Bidiagonalization
*/
template<typename Derived>
const UpperBidiagonalization<typename MatrixBase<Derived>::PlainObject>
MatrixBase<Derived>::bidiagonalization() const
{
return UpperBidiagonalization<PlainObject>(eval());
}
#endif
} // end namespace internal
} // end namespace Eigen
#endif // EIGEN_BIDIAGONALIZATION_H