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SUBROUTINE SROTG(SA,SB,C,S)
* .. Scalar Arguments ..
REAL C,S,SA,SB
* ..
*
* Purpose
* =======
*
* construct givens plane rotation.
* jack dongarra, linpack, 3/11/78.
*
*
* .. Local Scalars ..
REAL R,ROE,SCALE,Z
* ..
* .. Intrinsic Functions ..
INTRINSIC ABS,SIGN,SQRT
* ..
ROE = SB
IF (ABS(SA).GT.ABS(SB)) ROE = SA
SCALE = ABS(SA) + ABS(SB)
IF (SCALE.NE.0.0) GO TO 10
C = 1.0
S = 0.0
R = 0.0
Z = 0.0
GO TO 20
10 R = SCALE*SQRT((SA/SCALE)**2+ (SB/SCALE)**2)
R = SIGN(1.0,ROE)*R
C = SA/R
S = SB/R
Z = 1.0
IF (ABS(SA).GT.ABS(SB)) Z = S
IF (ABS(SB).GE.ABS(SA) .AND. C.NE.0.0) Z = 1.0/C
20 SA = R
SB = Z
RETURN
END
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