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Annotation of rpl/lapack/lapack/dlar2v.f, revision 1.7

1.1       bertrand    1:       SUBROUTINE DLAR2V( N, X, Y, Z, INCX, C, S, INCC )
                      2: *
                      3: *  -- LAPACK auxiliary routine (version 3.2) --
                      4: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
                      5: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
                      6: *     November 2006
                      7: *
                      8: *     .. Scalar Arguments ..
                      9:       INTEGER            INCC, INCX, N
                     10: *     ..
                     11: *     .. Array Arguments ..
                     12:       DOUBLE PRECISION   C( * ), S( * ), X( * ), Y( * ), Z( * )
                     13: *     ..
                     14: *
                     15: *  Purpose
                     16: *  =======
                     17: *
                     18: *  DLAR2V applies a vector of real plane rotations from both sides to
                     19: *  a sequence of 2-by-2 real symmetric matrices, defined by the elements
                     20: *  of the vectors x, y and z. For i = 1,2,...,n
                     21: *
                     22: *     ( x(i)  z(i) ) := (  c(i)  s(i) ) ( x(i)  z(i) ) ( c(i) -s(i) )
                     23: *     ( z(i)  y(i) )    ( -s(i)  c(i) ) ( z(i)  y(i) ) ( s(i)  c(i) )
                     24: *
                     25: *  Arguments
                     26: *  =========
                     27: *
                     28: *  N       (input) INTEGER
                     29: *          The number of plane rotations to be applied.
                     30: *
                     31: *  X       (input/output) DOUBLE PRECISION array,
                     32: *                         dimension (1+(N-1)*INCX)
                     33: *          The vector x.
                     34: *
                     35: *  Y       (input/output) DOUBLE PRECISION array,
                     36: *                         dimension (1+(N-1)*INCX)
                     37: *          The vector y.
                     38: *
                     39: *  Z       (input/output) DOUBLE PRECISION array,
                     40: *                         dimension (1+(N-1)*INCX)
                     41: *          The vector z.
                     42: *
                     43: *  INCX    (input) INTEGER
                     44: *          The increment between elements of X, Y and Z. INCX > 0.
                     45: *
                     46: *  C       (input) DOUBLE PRECISION array, dimension (1+(N-1)*INCC)
                     47: *          The cosines of the plane rotations.
                     48: *
                     49: *  S       (input) DOUBLE PRECISION array, dimension (1+(N-1)*INCC)
                     50: *          The sines of the plane rotations.
                     51: *
                     52: *  INCC    (input) INTEGER
                     53: *          The increment between elements of C and S. INCC > 0.
                     54: *
                     55: *  =====================================================================
                     56: *
                     57: *     .. Local Scalars ..
                     58:       INTEGER            I, IC, IX
                     59:       DOUBLE PRECISION   CI, SI, T1, T2, T3, T4, T5, T6, XI, YI, ZI
                     60: *     ..
                     61: *     .. Executable Statements ..
                     62: *
                     63:       IX = 1
                     64:       IC = 1
                     65:       DO 10 I = 1, N
                     66:          XI = X( IX )
                     67:          YI = Y( IX )
                     68:          ZI = Z( IX )
                     69:          CI = C( IC )
                     70:          SI = S( IC )
                     71:          T1 = SI*ZI
                     72:          T2 = CI*ZI
                     73:          T3 = T2 - SI*XI
                     74:          T4 = T2 + SI*YI
                     75:          T5 = CI*XI + T1
                     76:          T6 = CI*YI - T1
                     77:          X( IX ) = CI*T5 + SI*T4
                     78:          Y( IX ) = CI*T6 - SI*T3
                     79:          Z( IX ) = CI*T4 - SI*T5
                     80:          IX = IX + INCX
                     81:          IC = IC + INCC
                     82:    10 CONTINUE
                     83: *
                     84: *     End of DLAR2V
                     85: *
                     86:       RETURN
                     87:       END