LAPACK  3.10.0
LAPACK: Linear Algebra PACKage

◆ crot()

subroutine crot ( integer  N,
complex, dimension( * )  CX,
integer  INCX,
complex, dimension( * )  CY,
integer  INCY,
real  C,
complex  S 
)

CROT applies a plane rotation with real cosine and complex sine to a pair of complex vectors.

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

Purpose:
 CROT   applies a plane rotation, where the cos (C) is real and the
 sin (S) is complex, and the vectors CX and CY are complex.
Parameters
[in]N
          N is INTEGER
          The number of elements in the vectors CX and CY.
[in,out]CX
          CX is COMPLEX 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 array, dimension (N)
          On input, the vector Y.
          On output, CY is overwritten with -CONJG(S)*X + C*Y.
[in]INCY
          INCY is INTEGER
          The increment between successive values of CY.  INCX <> 0.
[in]C
          C is REAL
[in]S
          S is COMPLEX
          C and S define a rotation
             [  C          S  ]
             [ -conjg(S)   C  ]
          where C*C + S*CONJG(S) = 1.0.
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.

Definition at line 102 of file crot.f.

103 *
104 * -- LAPACK auxiliary routine --
105 * -- LAPACK is a software package provided by Univ. of Tennessee, --
106 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
107 *
108 * .. Scalar Arguments ..
109  INTEGER INCX, INCY, N
110  REAL C
111  COMPLEX S
112 * ..
113 * .. Array Arguments ..
114  COMPLEX CX( * ), CY( * )
115 * ..
116 *
117 * =====================================================================
118 *
119 * .. Local Scalars ..
120  INTEGER I, IX, IY
121  COMPLEX STEMP
122 * ..
123 * .. Intrinsic Functions ..
124  INTRINSIC conjg
125 * ..
126 * .. Executable Statements ..
127 *
128  IF( n.LE.0 )
129  $ RETURN
130  IF( incx.EQ.1 .AND. incy.EQ.1 )
131  $ GO TO 20
132 *
133 * Code for unequal increments or equal increments not equal to 1
134 *
135  ix = 1
136  iy = 1
137  IF( incx.LT.0 )
138  $ ix = ( -n+1 )*incx + 1
139  IF( incy.LT.0 )
140  $ iy = ( -n+1 )*incy + 1
141  DO 10 i = 1, n
142  stemp = c*cx( ix ) + s*cy( iy )
143  cy( iy ) = c*cy( iy ) - conjg( s )*cx( ix )
144  cx( ix ) = stemp
145  ix = ix + incx
146  iy = iy + incy
147  10 CONTINUE
148  RETURN
149 *
150 * Code for both increments equal to 1
151 *
152  20 CONTINUE
153  DO 30 i = 1, n
154  stemp = c*cx( i ) + s*cy( i )
155  cy( i ) = c*cy( i ) - conjg( s )*cx( i )
156  cx( i ) = stemp
157  30 CONTINUE
158  RETURN
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