NAME

dlasq4 - DLASQ4 estimates TAU, the smallest eigenvalue of a matrix

SYNOPSIS

SUBROUTINE DLASQ4( N, Q, E, TAU, SUP )

INTEGER N

DOUBLE PRECISION SUP, TAU

DOUBLE PRECISION E( ∗ ), Q( ∗ )

#include <sunperf.h>

void dlasq4(int n, double ∗q, double ∗e, double ∗tau, double ∗sup) ;

PURPOSE

   DLASQ4 estimates TAU, the smallest eigenvalue of a matrix. This
   routine improves the input value of SUP which is an upper bound
   for the smallest eigenvalue for this matrix .
 

ARGUMENTS

N (input) INTEGER
On entry, N specifies the number of rows and columns in the matrix. N must be at least 0.

Q (input) DOUBLE PRECISION array, dimension (N)
Q array

E (input) DOUBLE PRECISION array, dimension (N)
E array

TAU (output) DOUBLE PRECISION
Estimate of the shift

SUP (input/output) DOUBLE PRECISION
Upper bound for the smallest singular value

SunOS 5.0  —  Last change: 10 Dec 1998