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SUBROUTINE DLARGV( N, X, INCX, Y, INCY, C, INCC )
*
* -- LAPACK auxiliary routine (version 2.0) --
* Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
* Courant Institute, Argonne National Lab, and Rice University
* February 29, 1992
*
* .. Scalar Arguments ..
INTEGER INCC, INCX, INCY, N
* ..
* .. Array Arguments ..
DOUBLE PRECISION C( * ), X( * ), Y( * )
* ..
*
* Purpose
* =======
*
* DLARGV 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 )
*
* Arguments
* =========
*
* N (input) INTEGER
* The number of plane rotations to be generated.
*
* X (input/output) DOUBLE PRECISION array,
* dimension (1+(N-1)*INCX)
* On entry, the vector x.
* On exit, x(i) is overwritten by a(i), for i = 1,...,n.
*
* INCX (input) INTEGER
* The increment between elements of X. INCX > 0.
*
* Y (input/output) DOUBLE PRECISION array,
* dimension (1+(N-1)*INCY)
* On entry, the vector y.
* On exit, the sines of the plane rotations.
*
* INCY (input) INTEGER
* The increment between elements of Y. INCY > 0.
*
* C (output) DOUBLE PRECISION array, dimension (1+(N-1)*INCC)
* The cosines of the plane rotations.
*
* INCC (input) INTEGER
* The increment between elements of C. INCC > 0.
*
* =====================================================================
*
* .. Parameters ..
DOUBLE PRECISION ZERO, ONE
PARAMETER ( ZERO = 0.0D+0, ONE = 1.0D+0 )
* ..
* .. Local Scalars ..
INTEGER I, IC, IX, IY
DOUBLE PRECISION TT, W, XI, YI
* ..
* .. Intrinsic Functions ..
INTRINSIC ABS, MAX, SQRT
* ..
* .. Executable Statements ..
*
IX = 1
IY = 1
IC = 1
DO 10 I = 1, N
XI = X( IX )
YI = Y( IY )
IF( XI.EQ.ZERO ) THEN
C( IC ) = ZERO
Y( IY ) = ONE
X( IX ) = YI
ELSE
W = MAX( ABS( XI ), ABS( YI ) )
XI = XI / W
YI = YI / W
TT = SQRT( XI*XI+YI*YI )
C( IC ) = XI / TT
Y( IY ) = YI / TT
X( IX ) = W*TT
END IF
IX = IX + INCX
IY = IY + INCY
IC = IC + INCC
10 CONTINUE
RETURN
*
* End of DLARGV
*
END
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