Purpose
To compute the parameters for the complex Givens rotation ( C SR+SI*I ) ( XR+XI*I ) ( ZR+ZI*I ) ( ) * ( ) = ( ) ( -SR+SI*I C ) ( YR+YI*I ) ( 0 ) where C, SR, SI, XR, XI, YR, YI, ZR, ZI are real numbers, I is the imaginary unit, I = SQRT(-1), and C**2 + |SR+SI*I|**2 = 1.Specification
SUBROUTINE SG03BR( XR, XI, YR, YI, C, SR, SI, ZR, ZI ) C .. Scalar Arguments .. DOUBLE PRECISION C, SI, SR, XI, XR, YI, YR, ZI, ZRArguments
Input/Output Parameters
XR, XI, (input) DOUBLE PRECISION YR, YI (input) DOUBLE PRECISION The given real scalars XR, XI, YR, YI. C, (output) DOUBLE PRECISION SR, SI, (output) DOUBLE PRECISION ZR, ZI (output) DOUBLE PRECISION The computed real scalars C, SR, SI, ZR, ZI defining the complex Givens rotation and Z = ZR+ZI*I.Numerical Aspects
The subroutine avoids unnecessary overflow.Further Comments
In the interest of speed, this routine does not check the input for errors.Example
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