slasq3 (l)  Linux Man Pages
slasq3: checks for deflation, computes a shift (TAU) and calls dqds
Command to display slasq3
manual in Linux: $ man l slasq3
NAME
SLASQ3  checks for deflation, computes a shift (TAU) and calls dqds
SYNOPSIS
 SUBROUTINE SLASQ3(

I0, N0, Z, PP, DMIN, SIGMA, DESIG, QMAX, NFAIL,
ITER, NDIV, IEEE, TTYPE, DMIN1, DMIN2, DN, DN1,
DN2, G, TAU )

LOGICAL
IEEE

INTEGER
I0, ITER, N0, NDIV, NFAIL, PP

REAL
DESIG, DMIN, DMIN1, DMIN2, DN, DN1, DN2, G,
QMAX, SIGMA, TAU

REAL
Z( * )
PURPOSE
SLASQ3 checks for deflation, computes a shift (TAU) and calls dqds.
In case of failure it changes shifts, and tries again until output
is positive.
ARGUMENTS
 I0 (input) INTEGER

First index.
 N0 (input) INTEGER

Last index.
 Z (input) REAL array, dimension ( 4*N )

Z holds the qd array.
 PP (input/output) INTEGER

PP=0 for ping, PP=1 for pong.
PP=2 indicates that flipping was applied to the Z array
and that the initial tests for deflation should not be
performed.
 DMIN (output) REAL

Minimum value of d.
 SIGMA (output) REAL

Sum of shifts used in current segment.
 DESIG (input/output) REAL

Lower order part of SIGMA
 QMAX (input) REAL

Maximum value of q.
 NFAIL (output) INTEGER

Number of times shift was too big.
 ITER (output) INTEGER

Number of iterations.
 NDIV (output) INTEGER

Number of divisions.
 IEEE (input) LOGICAL

Flag for IEEE or non IEEE arithmetic (passed to SLASQ5).
 TTYPE (input/output) INTEGER

Shift type.
DMIN1, DMIN2, DN, DN1, DN2, G, TAU (input/output) REAL
These are passed as arguments in order to save their values
between calls to SLASQ3.
Pages related to slasq3
 slasq3 (3)
 slasq1 (l)  computes the singular values of a real NbyN bidiagonal matrix with diagonal D and offdiagonal E
 slasq2 (l)  computes all the eigenvalues of the symmetric positive definite tridiagonal matrix associated with the qd array Z to high relative accuracy are computed to high relative accuracy, in the absence of denormalization, underflow and overflow
 slasq4 (l)  computes an approximation TAU to the smallest eigenvalue using values of d from the previous transform
 slasq5 (l)  computes one dqds transform in pingpong form, one version for IEEE machines another for non IEEE machines
 slasq6 (l)  computes one dqd (shift equal to zero) transform in pingpong form, with protection against underflow and overflow
 slas2 (l)  computes the singular values of the 2by2 matrix [ F G ] [ 0 H ]
 slascl (l)  multiplies the M by N real matrix A by the real scalar CTO/CFROM
 slascl2 (l)  performs a diagonal scaling on a vector
 slasd0 (l)  a divide and conquer approach, SLASD0 computes the singular value decomposition (SVD) of a real upper bidiagonal NbyM matrix B with diagonal D and offdiagonal E, where M = N + SQRE