SLATEC Routines --- DH12 ---

*DECK DH12
      SUBROUTINE DH12 (MODE, LPIVOT, L1, M, U, IUE, UP, C, ICE, ICV,
     +   NCV)
C***BEGIN PROLOGUE  DH12
C***SUBSIDIARY
C***PURPOSE  Subsidiary to DHFTI, DLSEI and DWNNLS
C***LIBRARY   SLATEC
C***TYPE      DOUBLE PRECISION (H12-S, DH12-D)
C***AUTHOR  (UNKNOWN)
C***DESCRIPTION
C
C      *** DOUBLE PRECISION VERSION OF H12 ******
C
C     C.L.Lawson and R.J.Hanson, Jet Propulsion Laboratory, 1973 Jun 12
C     to appear in 'Solving Least Squares Problems', Prentice-Hall, 1974
C
C     Construction and/or application of a single
C     Householder transformation..     Q = I + U*(U**T)/B
C
C     MODE    = 1 or 2   to select algorithm  H1  or  H2 .
C     LPIVOT is the index of the pivot element.
C     L1,M   If L1 .LE. M   the transformation will be constructed to
C            zero elements indexed from L1 through M.   If L1 GT. M
C            THE SUBROUTINE DOES AN IDENTITY TRANSFORMATION.
C     U(),IUE,UP    On entry to H1 U() contains the pivot vector.
C                   IUE is the storage increment between elements.
C                                       On exit from H1 U() and UP
C                   contain quantities defining the vector U of the
C                   Householder transformation.   On entry to H2 U()
C                   and UP should contain quantities previously computed
C                   by H1.  These will not be modified by H2.
C     C()    On entry to H1 or H2 C() contains a matrix which will be
C            regarded as a set of vectors to which the Householder
C            transformation is to be applied.  On exit C() contains the
C            set of transformed vectors.
C     ICE    Storage increment between elements of vectors in C().
C     ICV    Storage increment between vectors in C().
C     NCV    Number of vectors in C() to be transformed. If NCV .LE. 0
C            no operations will be done on C().
C
C***SEE ALSO  DHFTI, DLSEI, DWNNLS
C***ROUTINES CALLED  DAXPY, DDOT, DSWAP
C***REVISION HISTORY  (YYMMDD)
C   790101  DATE WRITTEN
C   890531  Changed all specific intrinsics to generic.  (WRB)
C   890831  Modified array declarations.  (WRB)
C   891214  Prologue converted to Version 4.0 format.  (BAB)
C   900328  Added TYPE section.  (WRB)
C   900911  Added DDOT to DOUBLE PRECISION statement.  (WRB)
C***END PROLOGUE  DH12