*> \brief \b SLARGV generates a vector of plane rotations with real cosines and real sines. * * =========== DOCUMENTATION =========== * * Online html documentation available at * http://www.netlib.org/lapack/explore-html/ * *> \htmlonly *> Download SLARGV + dependencies *> *> [TGZ] *> *> [ZIP] *> *> [TXT] *> \endhtmlonly * * Definition: * =========== * * SUBROUTINE SLARGV( N, X, INCX, Y, INCY, C, INCC ) * * .. Scalar Arguments .. * INTEGER INCC, INCX, INCY, N * .. * .. Array Arguments .. * REAL C( * ), X( * ), Y( * ) * .. * * *> \par Purpose: * ============= *> *> \verbatim *> *> SLARGV generates a vector of real plane rotations, determined by *> elements of the real vectors x and y. For i = 1,2,...,n *> *> ( c(i) s(i) ) ( x(i) ) = ( a(i) ) *> ( -s(i) c(i) ) ( y(i) ) = ( 0 ) *> \endverbatim * * Arguments: * ========== * *> \param[in] N *> \verbatim *> N is INTEGER *> The number of plane rotations to be generated. *> \endverbatim *> *> \param[in,out] X *> \verbatim *> X is REAL array, *> dimension (1+(N-1)*INCX) *> On entry, the vector x. *> On exit, x(i) is overwritten by a(i), for i = 1,...,n. *> \endverbatim *> *> \param[in] INCX *> \verbatim *> INCX is INTEGER *> The increment between elements of X. INCX > 0. *> \endverbatim *> *> \param[in,out] Y *> \verbatim *> Y is REAL array, *> dimension (1+(N-1)*INCY) *> On entry, the vector y. *> On exit, the sines of the plane rotations. *> \endverbatim *> *> \param[in] INCY *> \verbatim *> INCY is INTEGER *> The increment between elements of Y. INCY > 0. *> \endverbatim *> *> \param[out] C *> \verbatim *> C is REAL array, dimension (1+(N-1)*INCC) *> The cosines of the plane rotations. *> \endverbatim *> *> \param[in] INCC *> \verbatim *> INCC is INTEGER *> The increment between elements of C. INCC > 0. *> \endverbatim * * Authors: * ======== * *> \author Univ. of Tennessee *> \author Univ. of California Berkeley *> \author Univ. of Colorado Denver *> \author NAG Ltd. * *> \ingroup realOTHERauxiliary * * ===================================================================== SUBROUTINE SLARGV( N, X, INCX, Y, INCY, C, INCC ) * * -- LAPACK auxiliary routine -- * -- LAPACK is a software package provided by Univ. of Tennessee, -- * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- * * .. Scalar Arguments .. INTEGER INCC, INCX, INCY, N * .. * .. Array Arguments .. REAL C( * ), X( * ), Y( * ) * .. * * ===================================================================== * * .. Parameters .. REAL ZERO, ONE PARAMETER ( ZERO = 0.0E+0, ONE = 1.0E+0 ) * .. * .. Local Scalars .. INTEGER I, IC, IX, IY REAL F, G, T, TT * .. * .. Intrinsic Functions .. INTRINSIC ABS, SQRT * .. * .. Executable Statements .. * IX = 1 IY = 1 IC = 1 DO 10 I = 1, N F = X( IX ) G = Y( IY ) IF( G.EQ.ZERO ) THEN C( IC ) = ONE ELSE IF( F.EQ.ZERO ) THEN C( IC ) = ZERO Y( IY ) = ONE X( IX ) = G ELSE IF( ABS( F ).GT.ABS( G ) ) THEN T = G / F TT = SQRT( ONE+T*T ) C( IC ) = ONE / TT Y( IY ) = T*C( IC ) X( IX ) = F*TT ELSE T = F / G TT = SQRT( ONE+T*T ) Y( IY ) = ONE / TT C( IC ) = T*Y( IY ) X( IX ) = G*TT END IF IC = IC + INCC IY = IY + INCY IX = IX + INCX 10 CONTINUE RETURN * * End of SLARGV * END