Annotation of rpl/lapack/lapack/dstevr.f, revision 1.17
1.8 bertrand 1: *> \brief <b> DSTEVR computes the eigenvalues and, optionally, the left and/or right eigenvectors for OTHER matrices</b>
2: *
3: * =========== DOCUMENTATION ===========
4: *
1.16 bertrand 5: * Online html documentation available at
6: * http://www.netlib.org/lapack/explore-html/
1.8 bertrand 7: *
8: *> \htmlonly
1.16 bertrand 9: *> Download DSTEVR + dependencies
10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dstevr.f">
11: *> [TGZ]</a>
12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dstevr.f">
13: *> [ZIP]</a>
14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dstevr.f">
1.8 bertrand 15: *> [TXT]</a>
1.16 bertrand 16: *> \endhtmlonly
1.8 bertrand 17: *
18: * Definition:
19: * ===========
20: *
21: * SUBROUTINE DSTEVR( JOBZ, RANGE, N, D, E, VL, VU, IL, IU, ABSTOL,
22: * M, W, Z, LDZ, ISUPPZ, WORK, LWORK, IWORK,
23: * LIWORK, INFO )
1.16 bertrand 24: *
1.8 bertrand 25: * .. Scalar Arguments ..
26: * CHARACTER JOBZ, RANGE
27: * INTEGER IL, INFO, IU, LDZ, LIWORK, LWORK, M, N
28: * DOUBLE PRECISION ABSTOL, VL, VU
29: * ..
30: * .. Array Arguments ..
31: * INTEGER ISUPPZ( * ), IWORK( * )
32: * DOUBLE PRECISION D( * ), E( * ), W( * ), WORK( * ), Z( LDZ, * )
33: * ..
1.16 bertrand 34: *
1.8 bertrand 35: *
36: *> \par Purpose:
37: * =============
38: *>
39: *> \verbatim
40: *>
41: *> DSTEVR computes selected eigenvalues and, optionally, eigenvectors
42: *> of a real symmetric tridiagonal matrix T. Eigenvalues and
43: *> eigenvectors can be selected by specifying either a range of values
44: *> or a range of indices for the desired eigenvalues.
45: *>
46: *> Whenever possible, DSTEVR calls DSTEMR to compute the
47: *> eigenspectrum using Relatively Robust Representations. DSTEMR
48: *> computes eigenvalues by the dqds algorithm, while orthogonal
49: *> eigenvectors are computed from various "good" L D L^T representations
50: *> (also known as Relatively Robust Representations). Gram-Schmidt
51: *> orthogonalization is avoided as far as possible. More specifically,
52: *> the various steps of the algorithm are as follows. For the i-th
53: *> unreduced block of T,
54: *> (a) Compute T - sigma_i = L_i D_i L_i^T, such that L_i D_i L_i^T
55: *> is a relatively robust representation,
56: *> (b) Compute the eigenvalues, lambda_j, of L_i D_i L_i^T to high
57: *> relative accuracy by the dqds algorithm,
58: *> (c) If there is a cluster of close eigenvalues, "choose" sigma_i
59: *> close to the cluster, and go to step (a),
60: *> (d) Given the approximate eigenvalue lambda_j of L_i D_i L_i^T,
61: *> compute the corresponding eigenvector by forming a
62: *> rank-revealing twisted factorization.
63: *> The desired accuracy of the output can be specified by the input
64: *> parameter ABSTOL.
65: *>
66: *> For more details, see "A new O(n^2) algorithm for the symmetric
67: *> tridiagonal eigenvalue/eigenvector problem", by Inderjit Dhillon,
68: *> Computer Science Division Technical Report No. UCB//CSD-97-971,
69: *> UC Berkeley, May 1997.
70: *>
71: *>
72: *> Note 1 : DSTEVR calls DSTEMR when the full spectrum is requested
73: *> on machines which conform to the ieee-754 floating point standard.
74: *> DSTEVR calls DSTEBZ and DSTEIN on non-ieee machines and
75: *> when partial spectrum requests are made.
76: *>
77: *> Normal execution of DSTEMR may create NaNs and infinities and
78: *> hence may abort due to a floating point exception in environments
79: *> which do not handle NaNs and infinities in the ieee standard default
80: *> manner.
81: *> \endverbatim
82: *
83: * Arguments:
84: * ==========
85: *
86: *> \param[in] JOBZ
87: *> \verbatim
88: *> JOBZ is CHARACTER*1
89: *> = 'N': Compute eigenvalues only;
90: *> = 'V': Compute eigenvalues and eigenvectors.
91: *> \endverbatim
92: *>
93: *> \param[in] RANGE
94: *> \verbatim
95: *> RANGE is CHARACTER*1
96: *> = 'A': all eigenvalues will be found.
97: *> = 'V': all eigenvalues in the half-open interval (VL,VU]
98: *> will be found.
99: *> = 'I': the IL-th through IU-th eigenvalues will be found.
100: *> For RANGE = 'V' or 'I' and IU - IL < N - 1, DSTEBZ and
101: *> DSTEIN are called
102: *> \endverbatim
103: *>
104: *> \param[in] N
105: *> \verbatim
106: *> N is INTEGER
107: *> The order of the matrix. N >= 0.
108: *> \endverbatim
109: *>
110: *> \param[in,out] D
111: *> \verbatim
112: *> D is DOUBLE PRECISION array, dimension (N)
113: *> On entry, the n diagonal elements of the tridiagonal matrix
114: *> A.
115: *> On exit, D may be multiplied by a constant factor chosen
116: *> to avoid over/underflow in computing the eigenvalues.
117: *> \endverbatim
118: *>
119: *> \param[in,out] E
120: *> \verbatim
121: *> E is DOUBLE PRECISION array, dimension (max(1,N-1))
122: *> On entry, the (n-1) subdiagonal elements of the tridiagonal
123: *> matrix A in elements 1 to N-1 of E.
124: *> On exit, E may be multiplied by a constant factor chosen
125: *> to avoid over/underflow in computing the eigenvalues.
126: *> \endverbatim
127: *>
128: *> \param[in] VL
129: *> \verbatim
130: *> VL is DOUBLE PRECISION
1.14 bertrand 131: *> If RANGE='V', the lower bound of the interval to
132: *> be searched for eigenvalues. VL < VU.
133: *> Not referenced if RANGE = 'A' or 'I'.
1.8 bertrand 134: *> \endverbatim
135: *>
136: *> \param[in] VU
137: *> \verbatim
138: *> VU is DOUBLE PRECISION
1.14 bertrand 139: *> If RANGE='V', the upper bound of the interval to
1.8 bertrand 140: *> be searched for eigenvalues. VL < VU.
141: *> Not referenced if RANGE = 'A' or 'I'.
142: *> \endverbatim
143: *>
144: *> \param[in] IL
145: *> \verbatim
146: *> IL is INTEGER
1.14 bertrand 147: *> If RANGE='I', the index of the
148: *> smallest eigenvalue to be returned.
149: *> 1 <= IL <= IU <= N, if N > 0; IL = 1 and IU = 0 if N = 0.
150: *> Not referenced if RANGE = 'A' or 'V'.
1.8 bertrand 151: *> \endverbatim
152: *>
153: *> \param[in] IU
154: *> \verbatim
155: *> IU is INTEGER
1.14 bertrand 156: *> If RANGE='I', the index of the
157: *> largest eigenvalue to be returned.
1.8 bertrand 158: *> 1 <= IL <= IU <= N, if N > 0; IL = 1 and IU = 0 if N = 0.
159: *> Not referenced if RANGE = 'A' or 'V'.
160: *> \endverbatim
161: *>
162: *> \param[in] ABSTOL
163: *> \verbatim
164: *> ABSTOL is DOUBLE PRECISION
165: *> The absolute error tolerance for the eigenvalues.
166: *> An approximate eigenvalue is accepted as converged
167: *> when it is determined to lie in an interval [a,b]
168: *> of width less than or equal to
169: *>
170: *> ABSTOL + EPS * max( |a|,|b| ) ,
171: *>
172: *> where EPS is the machine precision. If ABSTOL is less than
173: *> or equal to zero, then EPS*|T| will be used in its place,
174: *> where |T| is the 1-norm of the tridiagonal matrix obtained
175: *> by reducing A to tridiagonal form.
176: *>
177: *> See "Computing Small Singular Values of Bidiagonal Matrices
178: *> with Guaranteed High Relative Accuracy," by Demmel and
179: *> Kahan, LAPACK Working Note #3.
180: *>
181: *> If high relative accuracy is important, set ABSTOL to
182: *> DLAMCH( 'Safe minimum' ). Doing so will guarantee that
183: *> eigenvalues are computed to high relative accuracy when
184: *> possible in future releases. The current code does not
185: *> make any guarantees about high relative accuracy, but
186: *> future releases will. See J. Barlow and J. Demmel,
187: *> "Computing Accurate Eigensystems of Scaled Diagonally
188: *> Dominant Matrices", LAPACK Working Note #7, for a discussion
189: *> of which matrices define their eigenvalues to high relative
190: *> accuracy.
191: *> \endverbatim
192: *>
193: *> \param[out] M
194: *> \verbatim
195: *> M is INTEGER
196: *> The total number of eigenvalues found. 0 <= M <= N.
197: *> If RANGE = 'A', M = N, and if RANGE = 'I', M = IU-IL+1.
198: *> \endverbatim
199: *>
200: *> \param[out] W
201: *> \verbatim
202: *> W is DOUBLE PRECISION array, dimension (N)
203: *> The first M elements contain the selected eigenvalues in
204: *> ascending order.
205: *> \endverbatim
206: *>
207: *> \param[out] Z
208: *> \verbatim
209: *> Z is DOUBLE PRECISION array, dimension (LDZ, max(1,M) )
210: *> If JOBZ = 'V', then if INFO = 0, the first M columns of Z
211: *> contain the orthonormal eigenvectors of the matrix A
212: *> corresponding to the selected eigenvalues, with the i-th
213: *> column of Z holding the eigenvector associated with W(i).
214: *> Note: the user must ensure that at least max(1,M) columns are
215: *> supplied in the array Z; if RANGE = 'V', the exact value of M
216: *> is not known in advance and an upper bound must be used.
217: *> \endverbatim
218: *>
219: *> \param[in] LDZ
220: *> \verbatim
221: *> LDZ is INTEGER
222: *> The leading dimension of the array Z. LDZ >= 1, and if
223: *> JOBZ = 'V', LDZ >= max(1,N).
224: *> \endverbatim
225: *>
226: *> \param[out] ISUPPZ
227: *> \verbatim
228: *> ISUPPZ is INTEGER array, dimension ( 2*max(1,M) )
229: *> The support of the eigenvectors in Z, i.e., the indices
230: *> indicating the nonzero elements in Z. The i-th eigenvector
231: *> is nonzero only in elements ISUPPZ( 2*i-1 ) through
232: *> ISUPPZ( 2*i ).
233: *> Implemented only for RANGE = 'A' or 'I' and IU - IL = N - 1
234: *> \endverbatim
235: *>
236: *> \param[out] WORK
237: *> \verbatim
238: *> WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK))
239: *> On exit, if INFO = 0, WORK(1) returns the optimal (and
240: *> minimal) LWORK.
241: *> \endverbatim
242: *>
243: *> \param[in] LWORK
244: *> \verbatim
245: *> LWORK is INTEGER
246: *> The dimension of the array WORK. LWORK >= max(1,20*N).
247: *>
248: *> If LWORK = -1, then a workspace query is assumed; the routine
249: *> only calculates the optimal sizes of the WORK and IWORK
250: *> arrays, returns these values as the first entries of the WORK
251: *> and IWORK arrays, and no error message related to LWORK or
252: *> LIWORK is issued by XERBLA.
253: *> \endverbatim
254: *>
255: *> \param[out] IWORK
256: *> \verbatim
257: *> IWORK is INTEGER array, dimension (MAX(1,LIWORK))
258: *> On exit, if INFO = 0, IWORK(1) returns the optimal (and
259: *> minimal) LIWORK.
260: *> \endverbatim
261: *>
262: *> \param[in] LIWORK
263: *> \verbatim
264: *> LIWORK is INTEGER
265: *> The dimension of the array IWORK. LIWORK >= max(1,10*N).
266: *>
267: *> If LIWORK = -1, then a workspace query is assumed; the
268: *> routine only calculates the optimal sizes of the WORK and
269: *> IWORK arrays, returns these values as the first entries of
270: *> the WORK and IWORK arrays, and no error message related to
271: *> LWORK or LIWORK is issued by XERBLA.
272: *> \endverbatim
273: *>
274: *> \param[out] INFO
275: *> \verbatim
276: *> INFO is INTEGER
277: *> = 0: successful exit
278: *> < 0: if INFO = -i, the i-th argument had an illegal value
279: *> > 0: Internal error
280: *> \endverbatim
281: *
282: * Authors:
283: * ========
284: *
1.16 bertrand 285: *> \author Univ. of Tennessee
286: *> \author Univ. of California Berkeley
287: *> \author Univ. of Colorado Denver
288: *> \author NAG Ltd.
1.8 bertrand 289: *
1.14 bertrand 290: *> \date June 2016
1.8 bertrand 291: *
292: *> \ingroup doubleOTHEReigen
293: *
294: *> \par Contributors:
295: * ==================
296: *>
297: *> Inderjit Dhillon, IBM Almaden, USA \n
298: *> Osni Marques, LBNL/NERSC, USA \n
299: *> Ken Stanley, Computer Science Division, University of
300: *> California at Berkeley, USA \n
301: *>
302: * =====================================================================
1.1 bertrand 303: SUBROUTINE DSTEVR( JOBZ, RANGE, N, D, E, VL, VU, IL, IU, ABSTOL,
304: $ M, W, Z, LDZ, ISUPPZ, WORK, LWORK, IWORK,
305: $ LIWORK, INFO )
306: *
1.16 bertrand 307: * -- LAPACK driver routine (version 3.7.0) --
1.1 bertrand 308: * -- LAPACK is a software package provided by Univ. of Tennessee, --
309: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
1.14 bertrand 310: * June 2016
1.1 bertrand 311: *
312: * .. Scalar Arguments ..
313: CHARACTER JOBZ, RANGE
314: INTEGER IL, INFO, IU, LDZ, LIWORK, LWORK, M, N
315: DOUBLE PRECISION ABSTOL, VL, VU
316: * ..
317: * .. Array Arguments ..
318: INTEGER ISUPPZ( * ), IWORK( * )
319: DOUBLE PRECISION D( * ), E( * ), W( * ), WORK( * ), Z( LDZ, * )
320: * ..
321: *
322: * =====================================================================
323: *
324: * .. Parameters ..
325: DOUBLE PRECISION ZERO, ONE, TWO
326: PARAMETER ( ZERO = 0.0D+0, ONE = 1.0D+0, TWO = 2.0D+0 )
327: * ..
328: * .. Local Scalars ..
329: LOGICAL ALLEIG, INDEIG, TEST, LQUERY, VALEIG, WANTZ,
330: $ TRYRAC
331: CHARACTER ORDER
332: INTEGER I, IEEEOK, IMAX, INDIBL, INDIFL, INDISP,
333: $ INDIWO, ISCALE, ITMP1, J, JJ, LIWMIN, LWMIN,
334: $ NSPLIT
335: DOUBLE PRECISION BIGNUM, EPS, RMAX, RMIN, SAFMIN, SIGMA, SMLNUM,
336: $ TMP1, TNRM, VLL, VUU
337: * ..
338: * .. External Functions ..
339: LOGICAL LSAME
340: INTEGER ILAENV
341: DOUBLE PRECISION DLAMCH, DLANST
342: EXTERNAL LSAME, ILAENV, DLAMCH, DLANST
343: * ..
344: * .. External Subroutines ..
345: EXTERNAL DCOPY, DSCAL, DSTEBZ, DSTEMR, DSTEIN, DSTERF,
346: $ DSWAP, XERBLA
347: * ..
348: * .. Intrinsic Functions ..
349: INTRINSIC MAX, MIN, SQRT
350: * ..
351: * .. Executable Statements ..
352: *
353: *
354: * Test the input parameters.
355: *
356: IEEEOK = ILAENV( 10, 'DSTEVR', 'N', 1, 2, 3, 4 )
357: *
358: WANTZ = LSAME( JOBZ, 'V' )
359: ALLEIG = LSAME( RANGE, 'A' )
360: VALEIG = LSAME( RANGE, 'V' )
361: INDEIG = LSAME( RANGE, 'I' )
362: *
363: LQUERY = ( ( LWORK.EQ.-1 ) .OR. ( LIWORK.EQ.-1 ) )
364: LWMIN = MAX( 1, 20*N )
365: LIWMIN = MAX( 1, 10*N )
366: *
367: *
368: INFO = 0
369: IF( .NOT.( WANTZ .OR. LSAME( JOBZ, 'N' ) ) ) THEN
370: INFO = -1
371: ELSE IF( .NOT.( ALLEIG .OR. VALEIG .OR. INDEIG ) ) THEN
372: INFO = -2
373: ELSE IF( N.LT.0 ) THEN
374: INFO = -3
375: ELSE
376: IF( VALEIG ) THEN
377: IF( N.GT.0 .AND. VU.LE.VL )
378: $ INFO = -7
379: ELSE IF( INDEIG ) THEN
380: IF( IL.LT.1 .OR. IL.GT.MAX( 1, N ) ) THEN
381: INFO = -8
382: ELSE IF( IU.LT.MIN( N, IL ) .OR. IU.GT.N ) THEN
383: INFO = -9
384: END IF
385: END IF
386: END IF
387: IF( INFO.EQ.0 ) THEN
388: IF( LDZ.LT.1 .OR. ( WANTZ .AND. LDZ.LT.N ) ) THEN
389: INFO = -14
390: END IF
391: END IF
392: *
393: IF( INFO.EQ.0 ) THEN
394: WORK( 1 ) = LWMIN
395: IWORK( 1 ) = LIWMIN
396: *
397: IF( LWORK.LT.LWMIN .AND. .NOT.LQUERY ) THEN
398: INFO = -17
399: ELSE IF( LIWORK.LT.LIWMIN .AND. .NOT.LQUERY ) THEN
400: INFO = -19
401: END IF
402: END IF
403: *
404: IF( INFO.NE.0 ) THEN
405: CALL XERBLA( 'DSTEVR', -INFO )
406: RETURN
407: ELSE IF( LQUERY ) THEN
408: RETURN
409: END IF
410: *
411: * Quick return if possible
412: *
413: M = 0
414: IF( N.EQ.0 )
415: $ RETURN
416: *
417: IF( N.EQ.1 ) THEN
418: IF( ALLEIG .OR. INDEIG ) THEN
419: M = 1
420: W( 1 ) = D( 1 )
421: ELSE
422: IF( VL.LT.D( 1 ) .AND. VU.GE.D( 1 ) ) THEN
423: M = 1
424: W( 1 ) = D( 1 )
425: END IF
426: END IF
427: IF( WANTZ )
428: $ Z( 1, 1 ) = ONE
429: RETURN
430: END IF
431: *
432: * Get machine constants.
433: *
434: SAFMIN = DLAMCH( 'Safe minimum' )
435: EPS = DLAMCH( 'Precision' )
436: SMLNUM = SAFMIN / EPS
437: BIGNUM = ONE / SMLNUM
438: RMIN = SQRT( SMLNUM )
439: RMAX = MIN( SQRT( BIGNUM ), ONE / SQRT( SQRT( SAFMIN ) ) )
440: *
441: *
442: * Scale matrix to allowable range, if necessary.
443: *
444: ISCALE = 0
1.13 bertrand 445: IF( VALEIG ) THEN
446: VLL = VL
447: VUU = VU
448: END IF
1.1 bertrand 449: *
450: TNRM = DLANST( 'M', N, D, E )
451: IF( TNRM.GT.ZERO .AND. TNRM.LT.RMIN ) THEN
452: ISCALE = 1
453: SIGMA = RMIN / TNRM
454: ELSE IF( TNRM.GT.RMAX ) THEN
455: ISCALE = 1
456: SIGMA = RMAX / TNRM
457: END IF
458: IF( ISCALE.EQ.1 ) THEN
459: CALL DSCAL( N, SIGMA, D, 1 )
460: CALL DSCAL( N-1, SIGMA, E( 1 ), 1 )
461: IF( VALEIG ) THEN
462: VLL = VL*SIGMA
463: VUU = VU*SIGMA
464: END IF
465: END IF
466:
467: * Initialize indices into workspaces. Note: These indices are used only
468: * if DSTERF or DSTEMR fail.
469:
470: * IWORK(INDIBL:INDIBL+M-1) corresponds to IBLOCK in DSTEBZ and
471: * stores the block indices of each of the M<=N eigenvalues.
472: INDIBL = 1
473: * IWORK(INDISP:INDISP+NSPLIT-1) corresponds to ISPLIT in DSTEBZ and
474: * stores the starting and finishing indices of each block.
475: INDISP = INDIBL + N
476: * IWORK(INDIFL:INDIFL+N-1) stores the indices of eigenvectors
477: * that corresponding to eigenvectors that fail to converge in
478: * DSTEIN. This information is discarded; if any fail, the driver
479: * returns INFO > 0.
480: INDIFL = INDISP + N
481: * INDIWO is the offset of the remaining integer workspace.
482: INDIWO = INDISP + N
483: *
484: * If all eigenvalues are desired, then
485: * call DSTERF or DSTEMR. If this fails for some eigenvalue, then
486: * try DSTEBZ.
487: *
488: *
489: TEST = .FALSE.
490: IF( INDEIG ) THEN
491: IF( IL.EQ.1 .AND. IU.EQ.N ) THEN
492: TEST = .TRUE.
493: END IF
494: END IF
495: IF( ( ALLEIG .OR. TEST ) .AND. IEEEOK.EQ.1 ) THEN
496: CALL DCOPY( N-1, E( 1 ), 1, WORK( 1 ), 1 )
497: IF( .NOT.WANTZ ) THEN
498: CALL DCOPY( N, D, 1, W, 1 )
499: CALL DSTERF( N, W, WORK, INFO )
500: ELSE
501: CALL DCOPY( N, D, 1, WORK( N+1 ), 1 )
502: IF (ABSTOL .LE. TWO*N*EPS) THEN
503: TRYRAC = .TRUE.
504: ELSE
505: TRYRAC = .FALSE.
506: END IF
507: CALL DSTEMR( JOBZ, 'A', N, WORK( N+1 ), WORK, VL, VU, IL,
508: $ IU, M, W, Z, LDZ, N, ISUPPZ, TRYRAC,
509: $ WORK( 2*N+1 ), LWORK-2*N, IWORK, LIWORK, INFO )
510: *
511: END IF
512: IF( INFO.EQ.0 ) THEN
513: M = N
514: GO TO 10
515: END IF
516: INFO = 0
517: END IF
518: *
519: * Otherwise, call DSTEBZ and, if eigenvectors are desired, DSTEIN.
520: *
521: IF( WANTZ ) THEN
522: ORDER = 'B'
523: ELSE
524: ORDER = 'E'
525: END IF
526:
527: CALL DSTEBZ( RANGE, ORDER, N, VLL, VUU, IL, IU, ABSTOL, D, E, M,
528: $ NSPLIT, W, IWORK( INDIBL ), IWORK( INDISP ), WORK,
529: $ IWORK( INDIWO ), INFO )
530: *
531: IF( WANTZ ) THEN
532: CALL DSTEIN( N, D, E, M, W, IWORK( INDIBL ), IWORK( INDISP ),
533: $ Z, LDZ, WORK, IWORK( INDIWO ), IWORK( INDIFL ),
534: $ INFO )
535: END IF
536: *
537: * If matrix was scaled, then rescale eigenvalues appropriately.
538: *
539: 10 CONTINUE
540: IF( ISCALE.EQ.1 ) THEN
541: IF( INFO.EQ.0 ) THEN
542: IMAX = M
543: ELSE
544: IMAX = INFO - 1
545: END IF
546: CALL DSCAL( IMAX, ONE / SIGMA, W, 1 )
547: END IF
548: *
549: * If eigenvalues are not in order, then sort them, along with
550: * eigenvectors.
551: *
552: IF( WANTZ ) THEN
553: DO 30 J = 1, M - 1
554: I = 0
555: TMP1 = W( J )
556: DO 20 JJ = J + 1, M
557: IF( W( JJ ).LT.TMP1 ) THEN
558: I = JJ
559: TMP1 = W( JJ )
560: END IF
561: 20 CONTINUE
562: *
563: IF( I.NE.0 ) THEN
564: ITMP1 = IWORK( I )
565: W( I ) = W( J )
566: IWORK( I ) = IWORK( J )
567: W( J ) = TMP1
568: IWORK( J ) = ITMP1
569: CALL DSWAP( N, Z( 1, I ), 1, Z( 1, J ), 1 )
570: END IF
571: 30 CONTINUE
572: END IF
573: *
574: * Causes problems with tests 19 & 20:
575: * IF (wantz .and. INDEIG ) Z( 1,1) = Z(1,1) / 1.002 + .002
576: *
577: *
578: WORK( 1 ) = LWMIN
579: IWORK( 1 ) = LIWMIN
580: RETURN
581: *
582: * End of DSTEVR
583: *
584: END
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