dorthr.f
SUBROUTINE DORTHR (A, N, M, NRDA, IFLAG, IRANK, ISCALE, DIAG,
+ KPIVOT, SCALES, ROWS, RS)
C***BEGIN PROLOGUE DORTHR
....
....
Warning: this routine is not intended to be user-callable.
....
....
C***SUBSIDIARY
C***PURPOSE Subsidiary to DBVSUP and DSUDS
C***LIBRARY SLATEC
C***TYPE DOUBLE PRECISION (ORTHOR-S, DORTHR-D)
C***AUTHOR Watts, H. A., (SNLA)
C***DESCRIPTION
C
C Reduction of the matrix A to lower triangular form by a sequence of
C orthogonal HOUSEHOLDER transformations post-multiplying A.
C
C *********************************************************************
C INPUT
C *********************************************************************
C
C A -- Contains the matrix to be decomposed, must be dimensioned
C NRDA by N.
C N -- Number of rows in the matrix, N greater or equal to 1.
C M -- Number of columns in the matrix, M greater or equal to N.
C IFLAG -- Indicates the uncertainty in the matrix data.
C = 0 when the data is to be treated as exact.
C =-K when the data is assumed to be accurate to about
C K digits.
C ISCALE -- Scaling indicator.
C =-1 if the matrix is to be pre-scaled by
C columns when appropriate.
C Otherwise no scaling will be attempted.
C NRDA -- Row dimension of A, NRDA greater or equal to N.
C DIAG,KPIVOT,ROWS, -- Arrays of length at least N used internally
C RS,SCALES (except for SCALES which is M).
C
C *********************************************************************
C OUTPUT
C *********************************************************************
C
C IFLAG - Status indicator
C =1 for successful decomposition.
C =2 if improper input is detected.
C =3 if rank of the matrix is less than N.
C A -- Contains the reduced matrix in the strictly lower triangular
C part and transformation information.
C IRANK -- Contains the numerically determined matrix rank.
C DIAG -- Contains the diagonal elements of the reduced
C triangular matrix.
C KPIVOT -- Contains the pivotal information, the column
C interchanges performed on the original matrix are
C recorded here.
C SCALES -- Contains the column scaling parameters.
C
C *********************************************************************
C
C***SEE ALSO DBVSUP, DSUDS
C***REFERENCES G. Golub, Numerical methods for solving linear least
C squares problems, Numerische Mathematik 7, (1965),
C pp. 206-216.
C P. Businger and G. Golub, Linear least squares
C solutions by Householder transformations, Numerische
C Mathematik 7, (1965), pp. 269-276.
C***ROUTINES CALLED D1MACH, DCSCAL, DDOT, XERMSG
C***REVISION HISTORY (YYMMDD)
C 750601 DATE WRITTEN
C 890531 Changed all specific intrinsics to generic. (WRB)
C 891214 Prologue converted to Version 4.0 format. (BAB)
C 900315 CALLs to XERROR changed to CALLs to XERMSG. (THJ)
C 900328 Added TYPE section. (WRB)
C 910408 Updated the AUTHOR and REFERENCES sections. (WRB)
C 920501 Reformatted the REFERENCES section. (WRB)
C***END PROLOGUE DORTHR