srotmg

SROTMG(1)                        BLAS routine                        SROTMG(1)



NAME
       SROTMG - CONSTRUCT THE MODIFIED GIVENS TRANSFORMATION MATRIX H WHICH
       ZEROS  THE SECOND COMPONENT OF THE 2-VECTOR (SQRT(SD1)*SX1,SQRT(SD2)*

SYNOPSIS
       SUBROUTINE SROTMG(SD1,SD2,SX1,SY1,SPARAM)

           REAL                                  SD1,SD2,SX1,SY1

           REAL                                  SPARAM(5)

PURPOSE
          CONSTRUCT THE MODIFIED GIVENS TRANSFORMATION MATRIX H WHICH ZEROS
          THE SECOND COMPONENT OF THE 2-VECTOR  (SQRT(SD1)*SX1,SQRT(SD2)*
          SY2)**T.
          WITH SPARAM(1)=SFLAG, H HAS ONE OF THE FOLLOWING FORMS..

          SFLAG=-1.E0     SFLAG=0.E0        SFLAG=1.E0     SFLAG=-2.E0

            (SH11  SH12)    (1.E0  SH12)    (SH11  1.E0)    (1.E0  0.E0)
          H=(          )    (          )    (          )    (          )
            (SH21  SH22),   (SH21  1.E0),   (-1.E0 SH22),   (0.E0  1.E0).
          LOCATIONS 2-4 OF SPARAM CONTAIN SH11,SH21,SH12, AND SH22
          RESPECTIVELY. (VALUES OF 1.E0, -1.E0, OR 0.E0 IMPLIED BY THE
          VALUE OF SPARAM(1) ARE NOT STORED IN SPARAM.)

          THE VALUES OF GAMSQ AND RGAMSQ SET IN THE DATA STATEMENT MAY BE
          INEXACT.  THIS IS OK AS THEY ARE ONLY USED FOR TESTING THE SIZE
          OF SD1 AND SD2.  ALL ACTUAL SCALING OF DATA IS DONE USING GAM.



ARGUMENTS
       SD1    (input/output) REAL

       SD2    (input/output) REAL

       SX1    (input/output) REAL

       SY1    (input) REAL

              SPARAM (input/output)  REAL array, dimension 5 SPARAM(1)=SFLAG
              SPARAM(2)=SH11 SPARAM(3)=SH21 SPARAM(4)=SH12 SPARAM(5)=SH22



BLAS routine                     November 2008                       SROTMG(1)