1: *> \brief \b ZLACRT performs a linear transformation of a pair of complex vectors.
2: *
3: * =========== DOCUMENTATION ===========
4: *
5: * Online html documentation available at
6: * http://www.netlib.org/lapack/explore-html/
7: *
8: *> \htmlonly
9: *> Download ZLACRT + dependencies
10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/zlacrt.f">
11: *> [TGZ]</a>
12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/zlacrt.f">
13: *> [ZIP]</a>
14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/zlacrt.f">
15: *> [TXT]</a>
16: *> \endhtmlonly
17: *
18: * Definition:
19: * ===========
20: *
21: * SUBROUTINE ZLACRT( N, CX, INCX, CY, INCY, C, S )
22: *
23: * .. Scalar Arguments ..
24: * INTEGER INCX, INCY, N
25: * COMPLEX*16 C, S
26: * ..
27: * .. Array Arguments ..
28: * COMPLEX*16 CX( * ), CY( * )
29: * ..
30: *
31: *
32: *> \par Purpose:
33: * =============
34: *>
35: *> \verbatim
36: *>
37: *> ZLACRT performs the operation
38: *>
39: *> ( c s )( x ) ==> ( x )
40: *> ( -s c )( y ) ( y )
41: *>
42: *> where c and s are complex and the vectors x and y are complex.
43: *> \endverbatim
44: *
45: * Arguments:
46: * ==========
47: *
48: *> \param[in] N
49: *> \verbatim
50: *> N is INTEGER
51: *> The number of elements in the vectors CX and CY.
52: *> \endverbatim
53: *>
54: *> \param[in,out] CX
55: *> \verbatim
56: *> CX is COMPLEX*16 array, dimension (N)
57: *> On input, the vector x.
58: *> On output, CX is overwritten with c*x + s*y.
59: *> \endverbatim
60: *>
61: *> \param[in] INCX
62: *> \verbatim
63: *> INCX is INTEGER
64: *> The increment between successive values of CX. INCX <> 0.
65: *> \endverbatim
66: *>
67: *> \param[in,out] CY
68: *> \verbatim
69: *> CY is COMPLEX*16 array, dimension (N)
70: *> On input, the vector y.
71: *> On output, CY is overwritten with -s*x + c*y.
72: *> \endverbatim
73: *>
74: *> \param[in] INCY
75: *> \verbatim
76: *> INCY is INTEGER
77: *> The increment between successive values of CY. INCY <> 0.
78: *> \endverbatim
79: *>
80: *> \param[in] C
81: *> \verbatim
82: *> C is COMPLEX*16
83: *> \endverbatim
84: *>
85: *> \param[in] S
86: *> \verbatim
87: *> S is COMPLEX*16
88: *> C and S define the matrix
89: *> [ C S ].
90: *> [ -S C ]
91: *> \endverbatim
92: *
93: * Authors:
94: * ========
95: *
96: *> \author Univ. of Tennessee
97: *> \author Univ. of California Berkeley
98: *> \author Univ. of Colorado Denver
99: *> \author NAG Ltd.
100: *
101: *> \ingroup complex16OTHERauxiliary
102: *
103: * =====================================================================
104: SUBROUTINE ZLACRT( N, CX, INCX, CY, INCY, C, S )
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
157: END
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