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Cohérence Blas.

    1: *> \brief \b ZROTG
    2: *
    3: *  =========== DOCUMENTATION ===========
    4: *
    5: * Online html documentation available at 
    6: *            http://www.netlib.org/lapack/explore-html/ 
    7: *
    8: *  Definition:
    9: *  ===========
   10: *
   11: *       SUBROUTINE ZROTG(CA,CB,C,S)
   12: * 
   13: *       .. Scalar Arguments ..
   14: *       COMPLEX*16 CA,CB,S
   15: *       DOUBLE PRECISION C
   16: *       ..
   17: *  
   18: *
   19: *> \par Purpose:
   20: *  =============
   21: *>
   22: *> \verbatim
   23: *>
   24: *>    ZROTG determines a double complex Givens rotation.
   25: *> \endverbatim
   26: *
   27: *  Authors:
   28: *  ========
   29: *
   30: *> \author Univ. of Tennessee 
   31: *> \author Univ. of California Berkeley 
   32: *> \author Univ. of Colorado Denver 
   33: *> \author NAG Ltd. 
   34: *
   35: *> \date November 2011
   36: *
   37: *> \ingroup complex16_blas_level1
   38: *
   39: *  =====================================================================
   40:       SUBROUTINE ZROTG(CA,CB,C,S)
   41: *
   42: *  -- Reference BLAS level1 routine (version 3.4.0) --
   43: *  -- Reference BLAS is a software package provided by Univ. of Tennessee,    --
   44: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
   45: *     November 2011
   46: *
   47: *     .. Scalar Arguments ..
   48:       COMPLEX*16 CA,CB,S
   49:       DOUBLE PRECISION C
   50: *     ..
   51: *
   52: *  =====================================================================
   53: *
   54: *     .. Local Scalars ..
   55:       COMPLEX*16 ALPHA
   56:       DOUBLE PRECISION NORM,SCALE
   57: *     ..
   58: *     .. Intrinsic Functions ..
   59:       INTRINSIC CDABS,DCMPLX,DCONJG,DSQRT
   60: *     ..
   61:       IF (CDABS(CA).EQ.0.0d0) THEN
   62:          C = 0.0d0
   63:          S = (1.0d0,0.0d0)
   64:          CA = CB
   65:       ELSE
   66:          SCALE = CDABS(CA) + CDABS(CB)
   67:          NORM = SCALE*DSQRT((CDABS(CA/DCMPLX(SCALE,0.0d0)))**2+
   68:      $       (CDABS(CB/DCMPLX(SCALE,0.0d0)))**2)
   69:          ALPHA = CA/CDABS(CA)
   70:          C = CDABS(CA)/NORM
   71:          S = ALPHA*DCONJG(CB)/NORM
   72:          CA = ALPHA*NORM
   73:       END IF
   74:       RETURN
   75:       END