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