dlaic1 (l)  Linux Man Pages
dlaic1: applies one step of incremental condition estimation in its simplest version
NAME
DLAIC1  applies one step of incremental condition estimation in its simplest versionSYNOPSIS
 SUBROUTINE DLAIC1(
 JOB, J, X, SEST, W, GAMMA, SESTPR, S, C )
 INTEGER J, JOB
 DOUBLE PRECISION C, GAMMA, S, SEST, SESTPR
 DOUBLE PRECISION W( J ), X( J )
PURPOSE
DLAIC1 applies one step of incremental condition estimation in its simplest version: Let x, twonorm(x) = 1, be an approximate singular vector of an jbyj lower triangular matrix L, such thatThen DLAIC1 computes sestpr, s, c such that
the vector
is an approximate singular vector of
in the sense that
Depending on JOB, an estimate for the largest or smallest singular value is computed.
Note that [s c]aq and sestpr**2 is an eigenpair of the system
where alpha = xaq*w.
ARGUMENTS
 JOB (input) INTEGER

= 1: an estimate for the largest singular value is computed.
= 2: an estimate for the smallest singular value is computed.  J (input) INTEGER
 Length of X and W
 X (input) DOUBLE PRECISION array, dimension (J)
 The jvector x.
 SEST (input) DOUBLE PRECISION
 Estimated singular value of j by j matrix L
 W (input) DOUBLE PRECISION array, dimension (J)
 The jvector w.
 GAMMA (input) DOUBLE PRECISION
 The diagonal element gamma.
 SESTPR (output) DOUBLE PRECISION
 Estimated singular value of (j+1) by (j+1) matrix Lhat.
 S (output) DOUBLE PRECISION
 Sine needed in forming xhat.
 C (output) DOUBLE PRECISION

Cosine needed in forming xhat.