README.txt
Miscellaneous info for all versions of LSQR

Last modified: 23 Sep 2001
               Michael Saunders
               SOL, Stanford University


RELATED REFERENCES:

M. A. Saunders,
Solution of sparse rectangular systems using LSQR and CRAIG,
BIT 35, 588--604 (1995).

Relates CGM, MINRES and SYMMLQ for symmetric systems.
Gives analogous view of LSQR and CRAIG for regularized
least squares problems.  Introduces augmented system
K = [ (delta*I)     A
         A'    (- delta*I)]
whose condition number is approximately  norm(A)/delta.
------------------------------------------------------------

M. A. Saunders,
Computing projections with LSQR,
BIT 37(1), 96--104 (1997).

Uses Golub-Kahan bidiagonalization to compute projections
associated with least squares problems with and without
regularization.
------------------------------------------------------------

Bruce Hendrickson and Tamara G. Kolda,
Partitioning rectangular and structurally unsymmetric
sparse matrices for parallel processing,
SISC 21(6), 2048--2072 (2000).

Permutes rows and columns of rectangular A so that
the nonzeros of PAQ are clustered into rectangular
diagonal blocks, with relatively few nonzeros
outside the blocks.  The matrix of diagonal blocks
should be useful as a preconditioner.
------------------------------------------------------------