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Annotation of rpl/lapack/lapack/zrot.f, revision 1.4

1.1       bertrand    1:       SUBROUTINE ZROT( N, CX, INCX, CY, INCY, C, S )
                      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            INCX, INCY, N
                     10:       DOUBLE PRECISION   C
                     11:       COMPLEX*16         S
                     12: *     ..
                     13: *     .. Array Arguments ..
                     14:       COMPLEX*16         CX( * ), CY( * )
                     15: *     ..
                     16: *
                     17: *  Purpose
                     18: *  =======
                     19: *
                     20: *  ZROT   applies a plane rotation, where the cos (C) is real and the
                     21: *  sin (S) is complex, and the vectors CX and CY are complex.
                     22: *
                     23: *  Arguments
                     24: *  =========
                     25: *
                     26: *  N       (input) INTEGER
                     27: *          The number of elements in the vectors CX and CY.
                     28: *
                     29: *  CX      (input/output) COMPLEX*16 array, dimension (N)
                     30: *          On input, the vector X.
                     31: *          On output, CX is overwritten with C*X + S*Y.
                     32: *
                     33: *  INCX    (input) INTEGER
                     34: *          The increment between successive values of CY.  INCX <> 0.
                     35: *
                     36: *  CY      (input/output) COMPLEX*16 array, dimension (N)
                     37: *          On input, the vector Y.
                     38: *          On output, CY is overwritten with -CONJG(S)*X + C*Y.
                     39: *
                     40: *  INCY    (input) INTEGER
                     41: *          The increment between successive values of CY.  INCX <> 0.
                     42: *
                     43: *  C       (input) DOUBLE PRECISION
                     44: *  S       (input) COMPLEX*16
                     45: *          C and S define a rotation
                     46: *             [  C          S  ]
                     47: *             [ -conjg(S)   C  ]
                     48: *          where C*C + S*CONJG(S) = 1.0.
                     49: *
                     50: * =====================================================================
                     51: *
                     52: *     .. Local Scalars ..
                     53:       INTEGER            I, IX, IY
                     54:       COMPLEX*16         STEMP
                     55: *     ..
                     56: *     .. Intrinsic Functions ..
                     57:       INTRINSIC          DCONJG
                     58: *     ..
                     59: *     .. Executable Statements ..
                     60: *
                     61:       IF( N.LE.0 )
                     62:      $   RETURN
                     63:       IF( INCX.EQ.1 .AND. INCY.EQ.1 )
                     64:      $   GO TO 20
                     65: *
                     66: *     Code for unequal increments or equal increments not equal to 1
                     67: *
                     68:       IX = 1
                     69:       IY = 1
                     70:       IF( INCX.LT.0 )
                     71:      $   IX = ( -N+1 )*INCX + 1
                     72:       IF( INCY.LT.0 )
                     73:      $   IY = ( -N+1 )*INCY + 1
                     74:       DO 10 I = 1, N
                     75:          STEMP = C*CX( IX ) + S*CY( IY )
                     76:          CY( IY ) = C*CY( IY ) - DCONJG( S )*CX( IX )
                     77:          CX( IX ) = STEMP
                     78:          IX = IX + INCX
                     79:          IY = IY + INCY
                     80:    10 CONTINUE
                     81:       RETURN
                     82: *
                     83: *     Code for both increments equal to 1
                     84: *
                     85:    20 CONTINUE
                     86:       DO 30 I = 1, N
                     87:          STEMP = C*CX( I ) + S*CY( I )
                     88:          CY( I ) = C*CY( I ) - DCONJG( S )*CX( I )
                     89:          CX( I ) = STEMP
                     90:    30 CONTINUE
                     91:       RETURN
                     92:       END