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SUBROUTINE DLARGV( N, X, INCX, Y, INCY, C, INCC )
*
* -- LAPACK auxiliary routine (version 3.2) --
* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
* November 2006
*
* .. 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 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 DLARGV
*
END
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