LAPACK  3.10.0
LAPACK: Linear Algebra PACKage

◆ csrot()

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

CSROT

Purpose:
 CSROT applies a plane rotation, where the cos and sin (c and s) are real
 and the vectors cx and cy are complex.
 jack dongarra, linpack, 3/11/78.
Parameters
[in]N
          N is INTEGER
           On entry, N specifies the order of the vectors cx and cy.
           N must be at least zero.
[in,out]CX
          CX is COMPLEX array, dimension at least
           ( 1 + ( N - 1 )*abs( INCX ) ).
           Before entry, the incremented array CX must contain the n
           element vector cx. On exit, CX is overwritten by the updated
           vector cx.
[in]INCX
          INCX is INTEGER
           On entry, INCX specifies the increment for the elements of
           CX. INCX must not be zero.
[in,out]CY
          CY is COMPLEX array, dimension at least
           ( 1 + ( N - 1 )*abs( INCY ) ).
           Before entry, the incremented array CY must contain the n
           element vector cy. On exit, CY is overwritten by the updated
           vector cy.
[in]INCY
          INCY is INTEGER
           On entry, INCY specifies the increment for the elements of
           CY. INCY must not be zero.
[in]C
          C is REAL
           On entry, C specifies the cosine, cos.
[in]S
          S is REAL
           On entry, S specifies the sine, sin.
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.

Definition at line 97 of file csrot.f.

98 *
99 * -- Reference BLAS level1 routine --
100 * -- Reference BLAS is a software package provided by Univ. of Tennessee, --
101 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
102 *
103 * .. Scalar Arguments ..
104  INTEGER INCX, INCY, N
105  REAL C, S
106 * ..
107 * .. Array Arguments ..
108  COMPLEX CX( * ), CY( * )
109 * ..
110 *
111 * =====================================================================
112 *
113 * .. Local Scalars ..
114  INTEGER I, IX, IY
115  COMPLEX CTEMP
116 * ..
117 * .. Executable Statements ..
118 *
119  IF( n.LE.0 )
120  $ RETURN
121  IF( incx.EQ.1 .AND. incy.EQ.1 ) THEN
122 *
123 * code for both increments equal to 1
124 *
125  DO i = 1, n
126  ctemp = c*cx( i ) + s*cy( i )
127  cy( i ) = c*cy( i ) - s*cx( i )
128  cx( i ) = ctemp
129  END DO
130  ELSE
131 *
132 * code for unequal increments or equal increments not equal
133 * 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 i = 1, n
142  ctemp = c*cx( ix ) + s*cy( iy )
143  cy( iy ) = c*cy( iy ) - s*cx( ix )
144  cx( ix ) = ctemp
145  ix = ix + incx
146  iy = iy + incy
147  END DO
148  END IF
149  RETURN
150 *
151 * End of CSROT
152 *
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