LAPACK  3.9.1
LAPACK: Linear Algebra PACKage

◆ zlacrt()

subroutine zlacrt ( integer  N,
complex*16, dimension( * )  CX,
integer  INCX,
complex*16, dimension( * )  CY,
integer  INCY,
complex*16  C,
complex*16  S 
)

ZLACRT performs a linear transformation of a pair of complex vectors.

Download ZLACRT + dependencies [TGZ] [ZIP] [TXT]

Purpose:
 ZLACRT performs the operation

    (  c  s )( x )  ==> ( x )
    ( -s  c )( y )      ( y )

 where c and s are complex and the vectors x and y are complex.
Parameters
[in]N
          N is INTEGER
          The number of elements in the vectors CX and CY.
[in,out]CX
          CX is COMPLEX*16 array, dimension (N)
          On input, the vector x.
          On output, CX is overwritten with c*x + s*y.
[in]INCX
          INCX is INTEGER
          The increment between successive values of CX.  INCX <> 0.
[in,out]CY
          CY is COMPLEX*16 array, dimension (N)
          On input, the vector y.
          On output, CY is overwritten with -s*x + c*y.
[in]INCY
          INCY is INTEGER
          The increment between successive values of CY.  INCY <> 0.
[in]C
          C is COMPLEX*16
[in]S
          S is COMPLEX*16
          C and S define the matrix
             [  C   S  ].
             [ -S   C  ]
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.

Definition at line 104 of file zlacrt.f.

105 *
106 * -- LAPACK auxiliary routine --
107 * -- LAPACK is a software package provided by Univ. of Tennessee, --
108 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
109 *
110 * .. Scalar Arguments ..
111  INTEGER INCX, INCY, N
112  COMPLEX*16 C, S
113 * ..
114 * .. Array Arguments ..
115  COMPLEX*16 CX( * ), CY( * )
116 * ..
117 *
118 * =====================================================================
119 *
120 * .. Local Scalars ..
121  INTEGER I, IX, IY
122  COMPLEX*16 CTEMP
123 * ..
124 * .. Executable Statements ..
125 *
126  IF( n.LE.0 )
127  $ RETURN
128  IF( incx.EQ.1 .AND. incy.EQ.1 )
129  $ GO TO 20
130 *
131 * Code for unequal increments or equal increments not equal to 1
132 *
133  ix = 1
134  iy = 1
135  IF( incx.LT.0 )
136  $ ix = ( -n+1 )*incx + 1
137  IF( incy.LT.0 )
138  $ iy = ( -n+1 )*incy + 1
139  DO 10 i = 1, n
140  ctemp = c*cx( ix ) + s*cy( iy )
141  cy( iy ) = c*cy( iy ) - s*cx( ix )
142  cx( ix ) = ctemp
143  ix = ix + incx
144  iy = iy + incy
145  10 CONTINUE
146  RETURN
147 *
148 * Code for both increments equal to 1
149 *
150  20 CONTINUE
151  DO 30 i = 1, n
152  ctemp = c*cx( i ) + s*cy( i )
153  cy( i ) = c*cy( i ) - s*cx( i )
154  cx( i ) = ctemp
155  30 CONTINUE
156  RETURN