DH12(3)

SYNOPSIS
SUBROUTINE DH12 (MODE, LPIVOT, L1, M, U, IUE, UP, C, ICE, ICV, + NCV)

NAME
dh12 - Subsidiary to DHFTI, DLSEI and DWNNLS

LIBRARY
SLATEC

TYPE
DOUBLE PRECISION (H12-S, DH12-D)

AUTHOR
(UNKNOWN)

DESCRIPTION
*** DOUBLE PRECISION VERSION OF H12 ****** C.L.Lawson and R.J.Hanson, Jet Propulsion Laboratory, 1973 Jun 12 to appear in 'Solving Least Squares Problems', Prentice-Hall, 1974 Construction and/or application of a single Householder transformation.. Q = I + U*(U**T)/B MODE = 1 or 2 to select algorithm H1 or H2 . LPIVOT is the index of the pivot element. L1,M If L1 .LE. M the transformation will be constructed to zero elements indexed from L1 through M. If L1 GT. M THE SUBROUTINE DOES AN IDENTITY TRANSFORMATION. U(),IUE,UP On entry to H1 U() contains the pivot vector. IUE is the storage increment between elements. On exit from H1 U() and UP contain quantities defining the vector U of the Householder transformation. On entry to H2 U() and UP should contain quantities previously computed by H1. These will not be modified by H2. C() On entry to H1 or H2 C() contains a matrix which will be regarded as a set of vectors to which the Householder transformation is to be applied. On exit C() contains the set of transformed vectors. ICE Storage increment between elements of vectors in C(). ICV Storage increment between vectors in C(). NCV Number of vectors in C() to be transformed. If NCV .LE. 0 no operations will be done on C().

SEE ALSO
DHFTI, DLSEI, DWNNLS

ROUTINES CALLED
DAXPY, DDOT, DSWAP

REVISION HISTORY (YYMMDD)
790101 DATE WRITTEN
890531 Changed all specific intrinsics to generic. (WRB)
890831 Modified array declarations. (WRB)
891214 Prologue converted to Version 4.0 format. (BAB)
900328 Added TYPE section. (WRB)
900911 Added DDOT to DOUBLE PRECISION statement. (WRB)