@article {17710,
	title = {On an Inexpensive Triangular Approximation to the Singular Value Decomposition},
	volume = {UMIACS-TR-97-75},
	year = {1998},
	month = {1998/10/15/},
	institution = {Instititue for Advanced Computer Studies, Univ of Maryland, College Park},
	abstract = {In this paper we introduce a new decomposition called the pivotedQLP~decomposition.  It is computed by applying pivoted orthogonal
triangularization to the columns of the matrix $X$ in question to get
an upper triangular factor $R$ and then applying the same procedure to
the rows of $R$ to get a lower triangular matrix $L$.  The diagonal
elements of $R$ are called the R-values of $X$; those of $L$ are
called the L-values.  Numerical examples show that the L-values track
the singular values of $X$ with considerable fidelity\,---\,far better
than the R-values.  At a gap in the L-values the decomposition
provides orthonormal bases of analogues of row, column, and null
spaces provided of $X$.  The decomposition requires no more than twice
the work required for a pivoted QR~decomposition.  The computation of
$R$ and $L$ can be interleaved, so that the computation can be
the rows of $R$ to get a lower triangular matrix $L$.  The diagonal
elements of $R$ are called the R-values of $X$; those of $L$ are
called the L-values.  Numerical examples show that the L-values track
the singular values of $X$ with considerable fidelity\,---\,far better
than the R-values.  At a gap in the L-values the decomposition
provides orthonormal bases of analogues of row, column, and null
spaces provided of $X$.  The decomposition requires no more than twice
the work required for a pivoted QR~decomposition.  The computation of
$R$ and $L$ can be interleaved, so that the computation can be
terminated at any suitable point, which makes the decomposition
especially suitable for low-rank determination problems.  The
interleaved algorithm also suggests a new, efficient 2-norm estimator.
(Also cross-referenced as UMIACS-TR-97-75)
},
	keywords = {Technical Report},
	url = {http://drum.lib.umd.edu/handle/1903/920},
	author = {Stewart, G.W.}
}
