1: *> \brief \b ZGEBAK
2: *
3: * =========== DOCUMENTATION ===========
4: *
5: * Online html documentation available at
6: * http://www.netlib.org/lapack/explore-html/
7: *
8: *> \htmlonly
9: *> Download ZGEBAK + dependencies
10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/zgebak.f">
11: *> [TGZ]</a>
12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/zgebak.f">
13: *> [ZIP]</a>
14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/zgebak.f">
15: *> [TXT]</a>
16: *> \endhtmlonly
17: *
18: * Definition:
19: * ===========
20: *
21: * SUBROUTINE ZGEBAK( JOB, SIDE, N, ILO, IHI, SCALE, M, V, LDV,
22: * INFO )
23: *
24: * .. Scalar Arguments ..
25: * CHARACTER JOB, SIDE
26: * INTEGER IHI, ILO, INFO, LDV, M, N
27: * ..
28: * .. Array Arguments ..
29: * DOUBLE PRECISION SCALE( * )
30: * COMPLEX*16 V( LDV, * )
31: * ..
32: *
33: *
34: *> \par Purpose:
35: * =============
36: *>
37: *> \verbatim
38: *>
39: *> ZGEBAK forms the right or left eigenvectors of a complex general
40: *> matrix by backward transformation on the computed eigenvectors of the
41: *> balanced matrix output by ZGEBAL.
42: *> \endverbatim
43: *
44: * Arguments:
45: * ==========
46: *
47: *> \param[in] JOB
48: *> \verbatim
49: *> JOB is CHARACTER*1
50: *> Specifies the type of backward transformation required:
51: *> = 'N': do nothing, return immediately;
52: *> = 'P': do backward transformation for permutation only;
53: *> = 'S': do backward transformation for scaling only;
54: *> = 'B': do backward transformations for both permutation and
55: *> scaling.
56: *> JOB must be the same as the argument JOB supplied to ZGEBAL.
57: *> \endverbatim
58: *>
59: *> \param[in] SIDE
60: *> \verbatim
61: *> SIDE is CHARACTER*1
62: *> = 'R': V contains right eigenvectors;
63: *> = 'L': V contains left eigenvectors.
64: *> \endverbatim
65: *>
66: *> \param[in] N
67: *> \verbatim
68: *> N is INTEGER
69: *> The number of rows of the matrix V. N >= 0.
70: *> \endverbatim
71: *>
72: *> \param[in] ILO
73: *> \verbatim
74: *> ILO is INTEGER
75: *> \endverbatim
76: *>
77: *> \param[in] IHI
78: *> \verbatim
79: *> IHI is INTEGER
80: *> The integers ILO and IHI determined by ZGEBAL.
81: *> 1 <= ILO <= IHI <= N, if N > 0; ILO=1 and IHI=0, if N=0.
82: *> \endverbatim
83: *>
84: *> \param[in] SCALE
85: *> \verbatim
86: *> SCALE is DOUBLE PRECISION array, dimension (N)
87: *> Details of the permutation and scaling factors, as returned
88: *> by ZGEBAL.
89: *> \endverbatim
90: *>
91: *> \param[in] M
92: *> \verbatim
93: *> M is INTEGER
94: *> The number of columns of the matrix V. M >= 0.
95: *> \endverbatim
96: *>
97: *> \param[in,out] V
98: *> \verbatim
99: *> V is COMPLEX*16 array, dimension (LDV,M)
100: *> On entry, the matrix of right or left eigenvectors to be
101: *> transformed, as returned by ZHSEIN or ZTREVC.
102: *> On exit, V is overwritten by the transformed eigenvectors.
103: *> \endverbatim
104: *>
105: *> \param[in] LDV
106: *> \verbatim
107: *> LDV is INTEGER
108: *> The leading dimension of the array V. LDV >= max(1,N).
109: *> \endverbatim
110: *>
111: *> \param[out] INFO
112: *> \verbatim
113: *> INFO is INTEGER
114: *> = 0: successful exit
115: *> < 0: if INFO = -i, the i-th argument had an illegal value.
116: *> \endverbatim
117: *
118: * Authors:
119: * ========
120: *
121: *> \author Univ. of Tennessee
122: *> \author Univ. of California Berkeley
123: *> \author Univ. of Colorado Denver
124: *> \author NAG Ltd.
125: *
126: *> \ingroup complex16GEcomputational
127: *
128: * =====================================================================
129: SUBROUTINE ZGEBAK( JOB, SIDE, N, ILO, IHI, SCALE, M, V, LDV,
130: $ INFO )
131: *
132: * -- LAPACK computational routine --
133: * -- LAPACK is a software package provided by Univ. of Tennessee, --
134: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
135: *
136: * .. Scalar Arguments ..
137: CHARACTER JOB, SIDE
138: INTEGER IHI, ILO, INFO, LDV, M, N
139: * ..
140: * .. Array Arguments ..
141: DOUBLE PRECISION SCALE( * )
142: COMPLEX*16 V( LDV, * )
143: * ..
144: *
145: * =====================================================================
146: *
147: * .. Parameters ..
148: DOUBLE PRECISION ONE
149: PARAMETER ( ONE = 1.0D+0 )
150: * ..
151: * .. Local Scalars ..
152: LOGICAL LEFTV, RIGHTV
153: INTEGER I, II, K
154: DOUBLE PRECISION S
155: * ..
156: * .. External Functions ..
157: LOGICAL LSAME
158: EXTERNAL LSAME
159: * ..
160: * .. External Subroutines ..
161: EXTERNAL XERBLA, ZDSCAL, ZSWAP
162: * ..
163: * .. Intrinsic Functions ..
164: INTRINSIC MAX, MIN
165: * ..
166: * .. Executable Statements ..
167: *
168: * Decode and Test the input parameters
169: *
170: RIGHTV = LSAME( SIDE, 'R' )
171: LEFTV = LSAME( SIDE, 'L' )
172: *
173: INFO = 0
174: IF( .NOT.LSAME( JOB, 'N' ) .AND. .NOT.LSAME( JOB, 'P' ) .AND.
175: $ .NOT.LSAME( JOB, 'S' ) .AND. .NOT.LSAME( JOB, 'B' ) ) THEN
176: INFO = -1
177: ELSE IF( .NOT.RIGHTV .AND. .NOT.LEFTV ) THEN
178: INFO = -2
179: ELSE IF( N.LT.0 ) THEN
180: INFO = -3
181: ELSE IF( ILO.LT.1 .OR. ILO.GT.MAX( 1, N ) ) THEN
182: INFO = -4
183: ELSE IF( IHI.LT.MIN( ILO, N ) .OR. IHI.GT.N ) THEN
184: INFO = -5
185: ELSE IF( M.LT.0 ) THEN
186: INFO = -7
187: ELSE IF( LDV.LT.MAX( 1, N ) ) THEN
188: INFO = -9
189: END IF
190: IF( INFO.NE.0 ) THEN
191: CALL XERBLA( 'ZGEBAK', -INFO )
192: RETURN
193: END IF
194: *
195: * Quick return if possible
196: *
197: IF( N.EQ.0 )
198: $ RETURN
199: IF( M.EQ.0 )
200: $ RETURN
201: IF( LSAME( JOB, 'N' ) )
202: $ RETURN
203: *
204: IF( ILO.EQ.IHI )
205: $ GO TO 30
206: *
207: * Backward balance
208: *
209: IF( LSAME( JOB, 'S' ) .OR. LSAME( JOB, 'B' ) ) THEN
210: *
211: IF( RIGHTV ) THEN
212: DO 10 I = ILO, IHI
213: S = SCALE( I )
214: CALL ZDSCAL( M, S, V( I, 1 ), LDV )
215: 10 CONTINUE
216: END IF
217: *
218: IF( LEFTV ) THEN
219: DO 20 I = ILO, IHI
220: S = ONE / SCALE( I )
221: CALL ZDSCAL( M, S, V( I, 1 ), LDV )
222: 20 CONTINUE
223: END IF
224: *
225: END IF
226: *
227: * Backward permutation
228: *
229: * For I = ILO-1 step -1 until 1,
230: * IHI+1 step 1 until N do --
231: *
232: 30 CONTINUE
233: IF( LSAME( JOB, 'P' ) .OR. LSAME( JOB, 'B' ) ) THEN
234: IF( RIGHTV ) THEN
235: DO 40 II = 1, N
236: I = II
237: IF( I.GE.ILO .AND. I.LE.IHI )
238: $ GO TO 40
239: IF( I.LT.ILO )
240: $ I = ILO - II
241: K = INT( SCALE( I ) )
242: IF( K.EQ.I )
243: $ GO TO 40
244: CALL ZSWAP( M, V( I, 1 ), LDV, V( K, 1 ), LDV )
245: 40 CONTINUE
246: END IF
247: *
248: IF( LEFTV ) THEN
249: DO 50 II = 1, N
250: I = II
251: IF( I.GE.ILO .AND. I.LE.IHI )
252: $ GO TO 50
253: IF( I.LT.ILO )
254: $ I = ILO - II
255: K = INT( SCALE( I ) )
256: IF( K.EQ.I )
257: $ GO TO 50
258: CALL ZSWAP( M, V( I, 1 ), LDV, V( K, 1 ), LDV )
259: 50 CONTINUE
260: END IF
261: END IF
262: *
263: RETURN
264: *
265: * End of ZGEBAK
266: *
267: END
CVSweb interface <joel.bertrand@systella.fr>
![[BACK]](/cvsweb/icons/back.gif){kind=icon}
Return to zgebak.f CVS log ![[TXT]](/cvsweb/icons/text.gif){kind=icon}
![[DIR]](/cvsweb/icons/dir.gif){kind=icon}
Up to [local] / rpl / lapack / lapack