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SUBROUTINE DROTMG(DD1,DD2,DX1,DY1,DPARAM)* .. Scalar Arguments .. DOUBLE PRECISION DD1,DD2,DX1,DY1* ..* .. Array Arguments .. DOUBLE PRECISION DPARAM(5)* ..** Purpose* =======** CONSTRUCT THE MODIFIED GIVENS TRANSFORMATION MATRIX H WHICH ZEROS* THE SECOND COMPONENT OF THE 2-VECTOR (DSQRT(DD1)*DX1,DSQRT(DD2)** DY2)**T.* WITH DPARAM(1)=DFLAG, H HAS ONE OF THE FOLLOWING FORMS..** DFLAG=-1.D0 DFLAG=0.D0 DFLAG=1.D0 DFLAG=-2.D0** (DH11 DH12) (1.D0 DH12) (DH11 1.D0) (1.D0 0.D0)* H=( ) ( ) ( ) ( )* (DH21 DH22), (DH21 1.D0), (-1.D0 DH22), (0.D0 1.D0).* LOCATIONS 2-4 OF DPARAM CONTAIN DH11, DH21, DH12, AND DH22* RESPECTIVELY. (VALUES OF 1.D0, -1.D0, OR 0.D0 IMPLIED BY THE* VALUE OF DPARAM(1) ARE NOT STORED IN DPARAM.)** 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 DD1 AND DD2. ALL ACTUAL SCALING OF DATA IS DONE USING GAM.*** Arguments* =========** DD1 (input/output) DOUBLE PRECISION** DD2 (input/output) DOUBLE PRECISION ** DX1 (input/output) DOUBLE PRECISION ** DY1 (input) DOUBLE PRECISION** DPARAM (input/output) DOUBLE PRECISION array, dimension 5* DPARAM(1)=DFLAG* DPARAM(2)=DH11* DPARAM(3)=DH21* DPARAM(4)=DH12* DPARAM(5)=DH22** =====================================================================** .. Local Scalars .. DOUBLE PRECISION DFLAG,DH11,DH12,DH21,DH22,DP1,DP2,DQ1,DQ2,DTEMP, + DU,GAM,GAMSQ,ONE,RGAMSQ,TWO,ZERO INTEGER IGO* ..* .. Intrinsic Functions .. INTRINSIC DABS* ..* .. Data statements ..* DATA ZERO,ONE,TWO/0.D0,1.D0,2.D0/ DATA GAM,GAMSQ,RGAMSQ/4096.D0,16777216.D0,5.9604645D-8/* ..
IF (.NOT.DD1.LT.ZERO) GO TO 10* GO ZERO-H-D-AND-DX1.. GO TO 60 10 CONTINUE* CASE-DD1-NONNEGATIVE DP2 = DD2*DY1 IF (.NOT.DP2.EQ.ZERO) GO TO 20 DFLAG = -TWO GO TO 260* REGULAR-CASE.. 20 CONTINUE DP1 = DD1*DX1 DQ2 = DP2*DY1 DQ1 = DP1*DX1* IF (.NOT.DABS(DQ1).GT.DABS(DQ2)) GO TO 40 DH21 = -DY1/DX1 DH12 = DP2/DP1* DU = ONE - DH12*DH21* IF (.NOT.DU.LE.ZERO) GO TO 30* GO ZERO-H-D-AND-DX1.. GO TO 60 30 CONTINUE DFLAG = ZERO DD1 = DD1/DU DD2 = DD2/DU DX1 = DX1*DU* GO SCALE-CHECK.. GO TO 100 40 CONTINUE IF (.NOT.DQ2.LT.ZERO) GO TO 50* GO ZERO-H-D-AND-DX1.. GO TO 60 50 CONTINUE DFLAG = ONE DH11 = DP1/DP2 DH22 = DX1/DY1 DU = ONE + DH11*DH22 DTEMP = DD2/DU DD2 = DD1/DU DD1 = DTEMP DX1 = DY1*DU* GO SCALE-CHECK GO TO 100* PROCEDURE..ZERO-H-D-AND-DX1.. 60 CONTINUE DFLAG = -ONE DH11 = ZERO DH12 = ZERO DH21 = ZERO DH22 = ZERO* DD1 = ZERO DD2 = ZERO DX1 = ZERO* RETURN.. GO TO 220* PROCEDURE..FIX-H.. 70 CONTINUE IF (.NOT.DFLAG.GE.ZERO) GO TO 90* IF (.NOT.DFLAG.EQ.ZERO) GO TO 80 DH11 = ONE DH22 = ONE DFLAG = -ONE GO TO 90 80 CONTINUE DH21 = -ONE DH12 = ONE DFLAG = -ONE 90 CONTINUE GO TO IGO(120,150,180,210)* PROCEDURE..SCALE-CHECK 100 CONTINUE 110 CONTINUE IF (.NOT.DD1.LE.RGAMSQ) GO TO 130 IF (DD1.EQ.ZERO) GO TO 160 ASSIGN 120 TO IGO* FIX-H.. GO TO 70 120 CONTINUE DD1 = DD1*GAM**2 DX1 = DX1/GAM DH11 = DH11/GAM DH12 = DH12/GAM GO TO 110 130 CONTINUE 140 CONTINUE IF (.NOT.DD1.GE.GAMSQ) GO TO 160 ASSIGN 150 TO IGO* FIX-H.. GO TO 70 150 CONTINUE DD1 = DD1/GAM**2 DX1 = DX1*GAM DH11 = DH11*GAM DH12 = DH12*GAM GO TO 140 160 CONTINUE 170 CONTINUE IF (.NOT.DABS(DD2).LE.RGAMSQ) GO TO 190 IF (DD2.EQ.ZERO) GO TO 220 ASSIGN 180 TO IGO* FIX-H.. GO TO 70 180 CONTINUE DD2 = DD2*GAM**2 DH21 = DH21/GAM DH22 = DH22/GAM GO TO 170 190 CONTINUE 200 CONTINUE IF (.NOT.DABS(DD2).GE.GAMSQ) GO TO 220 ASSIGN 210 TO IGO* FIX-H.. GO TO 70 210 CONTINUE DD2 = DD2/GAM**2 DH21 = DH21*GAM DH22 = DH22*GAM GO TO 200 220 CONTINUE IF (DFLAG) 250,230,240 230 CONTINUE DPARAM(3) = DH21 DPARAM(4) = DH12 GO TO 260 240 CONTINUE DPARAM(2) = DH11 DPARAM(5) = DH22 GO TO 260 250 CONTINUE DPARAM(2) = DH11 DPARAM(3) = DH21 DPARAM(4) = DH12 DPARAM(5) = DH22 260 CONTINUE DPARAM(1) = DFLAG RETURN END
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