SUBROUTINE DLAR2V( N, X, Y, Z, INCX, C, S, INCC ) * * -- LAPACK auxiliary routine (version 3.2) -- * -- LAPACK is a software package provided by Univ. of Tennessee, -- * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- * November 2006 * * .. Scalar Arguments .. INTEGER INCC, INCX, N * .. * .. Array Arguments .. DOUBLE PRECISION C( * ), S( * ), X( * ), Y( * ), Z( * ) * .. * * Purpose * ======= * * DLAR2V applies a vector of real plane rotations from both sides to * a sequence of 2-by-2 real symmetric matrices, defined by the elements * of the vectors x, y and z. For i = 1,2,...,n * * ( x(i) z(i) ) := ( c(i) s(i) ) ( x(i) z(i) ) ( c(i) -s(i) ) * ( z(i) y(i) ) ( -s(i) c(i) ) ( z(i) y(i) ) ( s(i) c(i) ) * * Arguments * ========= * * N (input) INTEGER * The number of plane rotations to be applied. * * X (input/output) DOUBLE PRECISION array, * dimension (1+(N-1)*INCX) * The vector x. * * Y (input/output) DOUBLE PRECISION array, * dimension (1+(N-1)*INCX) * The vector y. * * Z (input/output) DOUBLE PRECISION array, * dimension (1+(N-1)*INCX) * The vector z. * * INCX (input) INTEGER * The increment between elements of X, Y and Z. INCX > 0. * * C (input) DOUBLE PRECISION array, dimension (1+(N-1)*INCC) * The cosines of the plane rotations. * * S (input) DOUBLE PRECISION array, dimension (1+(N-1)*INCC) * The sines of the plane rotations. * * INCC (input) INTEGER * The increment between elements of C and S. INCC > 0. * * ===================================================================== * * .. Local Scalars .. INTEGER I, IC, IX DOUBLE PRECISION CI, SI, T1, T2, T3, T4, T5, T6, XI, YI, ZI * .. * .. Executable Statements .. * IX = 1 IC = 1 DO 10 I = 1, N XI = X( IX ) YI = Y( IX ) ZI = Z( IX ) CI = C( IC ) SI = S( IC ) T1 = SI*ZI T2 = CI*ZI T3 = T2 - SI*XI T4 = T2 + SI*YI T5 = CI*XI + T1 T6 = CI*YI - T1 X( IX ) = CI*T5 + SI*T4 Y( IX ) = CI*T6 - SI*T3 Z( IX ) = CI*T4 - SI*T5 IX = IX + INCX IC = IC + INCC 10 CONTINUE * * End of DLAR2V * RETURN END