1: *> \brief <b> ZHEEVR computes the eigenvalues and, optionally, the left and/or right eigenvectors for HE matrices</b>
2: *
3: * =========== DOCUMENTATION ===========
4: *
5: * Online html documentation available at
6: * http://www.netlib.org/lapack/explore-html/
7: *
8: *> \htmlonly
9: *> Download ZHEEVR + dependencies
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11: *> [TGZ]</a>
12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/zheevr.f">
13: *> [ZIP]</a>
14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/zheevr.f">
15: *> [TXT]</a>
16: *> \endhtmlonly
17: *
18: * Definition:
19: * ===========
20: *
21: * SUBROUTINE ZHEEVR( JOBZ, RANGE, UPLO, N, A, LDA, VL, VU, IL, IU,
22: * ABSTOL, M, W, Z, LDZ, ISUPPZ, WORK, LWORK,
23: * RWORK, LRWORK, IWORK, LIWORK, INFO )
24: *
25: * .. Scalar Arguments ..
26: * CHARACTER JOBZ, RANGE, UPLO
27: * INTEGER IL, INFO, IU, LDA, LDZ, LIWORK, LRWORK, LWORK,
28: * $ M, N
29: * DOUBLE PRECISION ABSTOL, VL, VU
30: * ..
31: * .. Array Arguments ..
32: * INTEGER ISUPPZ( * ), IWORK( * )
33: * DOUBLE PRECISION RWORK( * ), W( * )
34: * COMPLEX*16 A( LDA, * ), WORK( * ), Z( LDZ, * )
35: * ..
36: *
37: *
38: *> \par Purpose:
39: * =============
40: *>
41: *> \verbatim
42: *>
43: *> ZHEEVR computes selected eigenvalues and, optionally, eigenvectors
44: *> of a complex Hermitian matrix A. Eigenvalues and eigenvectors can
45: *> be selected by specifying either a range of values or a range of
46: *> indices for the desired eigenvalues.
47: *>
48: *> ZHEEVR first reduces the matrix A to tridiagonal form T with a call
49: *> to ZHETRD. Then, whenever possible, ZHEEVR calls ZSTEMR to compute
50: *> eigenspectrum using Relatively Robust Representations. ZSTEMR
51: *> computes eigenvalues by the dqds algorithm, while orthogonal
52: *> eigenvectors are computed from various "good" L D L^T representations
53: *> (also known as Relatively Robust Representations). Gram-Schmidt
54: *> orthogonalization is avoided as far as possible. More specifically,
55: *> the various steps of the algorithm are as follows.
56: *>
57: *> For each unreduced block (submatrix) of T,
58: *> (a) Compute T - sigma I = L D L^T, so that L and D
59: *> define all the wanted eigenvalues to high relative accuracy.
60: *> This means that small relative changes in the entries of D and L
61: *> cause only small relative changes in the eigenvalues and
62: *> eigenvectors. The standard (unfactored) representation of the
63: *> tridiagonal matrix T does not have this property in general.
64: *> (b) Compute the eigenvalues to suitable accuracy.
65: *> If the eigenvectors are desired, the algorithm attains full
66: *> accuracy of the computed eigenvalues only right before
67: *> the corresponding vectors have to be computed, see steps c) and d).
68: *> (c) For each cluster of close eigenvalues, select a new
69: *> shift close to the cluster, find a new factorization, and refine
70: *> the shifted eigenvalues to suitable accuracy.
71: *> (d) For each eigenvalue with a large enough relative separation compute
72: *> the corresponding eigenvector by forming a rank revealing twisted
73: *> factorization. Go back to (c) for any clusters that remain.
74: *>
75: *> The desired accuracy of the output can be specified by the input
76: *> parameter ABSTOL.
77: *>
78: *> For more details, see ZSTEMR's documentation and:
79: *> - Inderjit S. Dhillon and Beresford N. Parlett: "Multiple representations
80: *> to compute orthogonal eigenvectors of symmetric tridiagonal matrices,"
81: *> Linear Algebra and its Applications, 387(1), pp. 1-28, August 2004.
82: *> - Inderjit Dhillon and Beresford Parlett: "Orthogonal Eigenvectors and
83: *> Relative Gaps," SIAM Journal on Matrix Analysis and Applications, Vol. 25,
84: *> 2004. Also LAPACK Working Note 154.
85: *> - Inderjit Dhillon: "A new O(n^2) algorithm for the symmetric
86: *> tridiagonal eigenvalue/eigenvector problem",
87: *> Computer Science Division Technical Report No. UCB/CSD-97-971,
88: *> UC Berkeley, May 1997.
89: *>
90: *>
91: *> Note 1 : ZHEEVR calls ZSTEMR when the full spectrum is requested
92: *> on machines which conform to the ieee-754 floating point standard.
93: *> ZHEEVR calls DSTEBZ and ZSTEIN on non-ieee machines and
94: *> when partial spectrum requests are made.
95: *>
96: *> Normal execution of ZSTEMR may create NaNs and infinities and
97: *> hence may abort due to a floating point exception in environments
98: *> which do not handle NaNs and infinities in the ieee standard default
99: *> manner.
100: *> \endverbatim
101: *
102: * Arguments:
103: * ==========
104: *
105: *> \param[in] JOBZ
106: *> \verbatim
107: *> JOBZ is CHARACTER*1
108: *> = 'N': Compute eigenvalues only;
109: *> = 'V': Compute eigenvalues and eigenvectors.
110: *> \endverbatim
111: *>
112: *> \param[in] RANGE
113: *> \verbatim
114: *> RANGE is CHARACTER*1
115: *> = 'A': all eigenvalues will be found.
116: *> = 'V': all eigenvalues in the half-open interval (VL,VU]
117: *> will be found.
118: *> = 'I': the IL-th through IU-th eigenvalues will be found.
119: *> For RANGE = 'V' or 'I' and IU - IL < N - 1, DSTEBZ and
120: *> ZSTEIN are called
121: *> \endverbatim
122: *>
123: *> \param[in] UPLO
124: *> \verbatim
125: *> UPLO is CHARACTER*1
126: *> = 'U': Upper triangle of A is stored;
127: *> = 'L': Lower triangle of A is stored.
128: *> \endverbatim
129: *>
130: *> \param[in] N
131: *> \verbatim
132: *> N is INTEGER
133: *> The order of the matrix A. N >= 0.
134: *> \endverbatim
135: *>
136: *> \param[in,out] A
137: *> \verbatim
138: *> A is COMPLEX*16 array, dimension (LDA, N)
139: *> On entry, the Hermitian matrix A. If UPLO = 'U', the
140: *> leading N-by-N upper triangular part of A contains the
141: *> upper triangular part of the matrix A. If UPLO = 'L',
142: *> the leading N-by-N lower triangular part of A contains
143: *> the lower triangular part of the matrix A.
144: *> On exit, the lower triangle (if UPLO='L') or the upper
145: *> triangle (if UPLO='U') of A, including the diagonal, is
146: *> destroyed.
147: *> \endverbatim
148: *>
149: *> \param[in] LDA
150: *> \verbatim
151: *> LDA is INTEGER
152: *> The leading dimension of the array A. LDA >= max(1,N).
153: *> \endverbatim
154: *>
155: *> \param[in] VL
156: *> \verbatim
157: *> VL is DOUBLE PRECISION
158: *> If RANGE='V', the lower bound of the interval to
159: *> be searched for eigenvalues. VL < VU.
160: *> Not referenced if RANGE = 'A' or 'I'.
161: *> \endverbatim
162: *>
163: *> \param[in] VU
164: *> \verbatim
165: *> VU is DOUBLE PRECISION
166: *> If RANGE='V', the upper bound of the interval to
167: *> be searched for eigenvalues. VL < VU.
168: *> Not referenced if RANGE = 'A' or 'I'.
169: *> \endverbatim
170: *>
171: *> \param[in] IL
172: *> \verbatim
173: *> IL is INTEGER
174: *> If RANGE='I', the index of the
175: *> smallest eigenvalue to be returned.
176: *> 1 <= IL <= IU <= N, if N > 0; IL = 1 and IU = 0 if N = 0.
177: *> Not referenced if RANGE = 'A' or 'V'.
178: *> \endverbatim
179: *>
180: *> \param[in] IU
181: *> \verbatim
182: *> IU is INTEGER
183: *> If RANGE='I', the index of the
184: *> largest eigenvalue to be returned.
185: *> 1 <= IL <= IU <= N, if N > 0; IL = 1 and IU = 0 if N = 0.
186: *> Not referenced if RANGE = 'A' or 'V'.
187: *> \endverbatim
188: *>
189: *> \param[in] ABSTOL
190: *> \verbatim
191: *> ABSTOL is DOUBLE PRECISION
192: *> The absolute error tolerance for the eigenvalues.
193: *> An approximate eigenvalue is accepted as converged
194: *> when it is determined to lie in an interval [a,b]
195: *> of width less than or equal to
196: *>
197: *> ABSTOL + EPS * max( |a|,|b| ) ,
198: *>
199: *> where EPS is the machine precision. If ABSTOL is less than
200: *> or equal to zero, then EPS*|T| will be used in its place,
201: *> where |T| is the 1-norm of the tridiagonal matrix obtained
202: *> by reducing A to tridiagonal form.
203: *>
204: *> See "Computing Small Singular Values of Bidiagonal Matrices
205: *> with Guaranteed High Relative Accuracy," by Demmel and
206: *> Kahan, LAPACK Working Note #3.
207: *>
208: *> If high relative accuracy is important, set ABSTOL to
209: *> DLAMCH( 'Safe minimum' ). Doing so will guarantee that
210: *> eigenvalues are computed to high relative accuracy when
211: *> possible in future releases. The current code does not
212: *> make any guarantees about high relative accuracy, but
213: *> future releases will. See J. Barlow and J. Demmel,
214: *> "Computing Accurate Eigensystems of Scaled Diagonally
215: *> Dominant Matrices", LAPACK Working Note #7, for a discussion
216: *> of which matrices define their eigenvalues to high relative
217: *> accuracy.
218: *> \endverbatim
219: *>
220: *> \param[out] M
221: *> \verbatim
222: *> M is INTEGER
223: *> The total number of eigenvalues found. 0 <= M <= N.
224: *> If RANGE = 'A', M = N, and if RANGE = 'I', M = IU-IL+1.
225: *> \endverbatim
226: *>
227: *> \param[out] W
228: *> \verbatim
229: *> W is DOUBLE PRECISION array, dimension (N)
230: *> The first M elements contain the selected eigenvalues in
231: *> ascending order.
232: *> \endverbatim
233: *>
234: *> \param[out] Z
235: *> \verbatim
236: *> Z is COMPLEX*16 array, dimension (LDZ, max(1,M))
237: *> If JOBZ = 'V', then if INFO = 0, the first M columns of Z
238: *> contain the orthonormal eigenvectors of the matrix A
239: *> corresponding to the selected eigenvalues, with the i-th
240: *> column of Z holding the eigenvector associated with W(i).
241: *> If JOBZ = 'N', then Z is not referenced.
242: *> Note: the user must ensure that at least max(1,M) columns are
243: *> supplied in the array Z; if RANGE = 'V', the exact value of M
244: *> is not known in advance and an upper bound must be used.
245: *> \endverbatim
246: *>
247: *> \param[in] LDZ
248: *> \verbatim
249: *> LDZ is INTEGER
250: *> The leading dimension of the array Z. LDZ >= 1, and if
251: *> JOBZ = 'V', LDZ >= max(1,N).
252: *> \endverbatim
253: *>
254: *> \param[out] ISUPPZ
255: *> \verbatim
256: *> ISUPPZ is INTEGER array, dimension ( 2*max(1,M) )
257: *> The support of the eigenvectors in Z, i.e., the indices
258: *> indicating the nonzero elements in Z. The i-th eigenvector
259: *> is nonzero only in elements ISUPPZ( 2*i-1 ) through
260: *> ISUPPZ( 2*i ). This is an output of ZSTEMR (tridiagonal
261: *> matrix). The support of the eigenvectors of A is typically
262: *> 1:N because of the unitary transformations applied by ZUNMTR.
263: *> Implemented only for RANGE = 'A' or 'I' and IU - IL = N - 1
264: *> \endverbatim
265: *>
266: *> \param[out] WORK
267: *> \verbatim
268: *> WORK is COMPLEX*16 array, dimension (MAX(1,LWORK))
269: *> On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
270: *> \endverbatim
271: *>
272: *> \param[in] LWORK
273: *> \verbatim
274: *> LWORK is INTEGER
275: *> The length of the array WORK. LWORK >= max(1,2*N).
276: *> For optimal efficiency, LWORK >= (NB+1)*N,
277: *> where NB is the max of the blocksize for ZHETRD and for
278: *> ZUNMTR as returned by ILAENV.
279: *>
280: *> If LWORK = -1, then a workspace query is assumed; the routine
281: *> only calculates the optimal sizes of the WORK, RWORK and
282: *> IWORK arrays, returns these values as the first entries of
283: *> the WORK, RWORK and IWORK arrays, and no error message
284: *> related to LWORK or LRWORK or LIWORK is issued by XERBLA.
285: *> \endverbatim
286: *>
287: *> \param[out] RWORK
288: *> \verbatim
289: *> RWORK is DOUBLE PRECISION array, dimension (MAX(1,LRWORK))
290: *> On exit, if INFO = 0, RWORK(1) returns the optimal
291: *> (and minimal) LRWORK.
292: *> \endverbatim
293: *>
294: *> \param[in] LRWORK
295: *> \verbatim
296: *> LRWORK is INTEGER
297: *> The length of the array RWORK. LRWORK >= max(1,24*N).
298: *>
299: *> If LRWORK = -1, then a workspace query is assumed; the
300: *> routine only calculates the optimal sizes of the WORK, RWORK
301: *> and IWORK arrays, returns these values as the first entries
302: *> of the WORK, RWORK and IWORK arrays, and no error message
303: *> related to LWORK or LRWORK or LIWORK is issued by XERBLA.
304: *> \endverbatim
305: *>
306: *> \param[out] IWORK
307: *> \verbatim
308: *> IWORK is INTEGER array, dimension (MAX(1,LIWORK))
309: *> On exit, if INFO = 0, IWORK(1) returns the optimal
310: *> (and minimal) LIWORK.
311: *> \endverbatim
312: *>
313: *> \param[in] LIWORK
314: *> \verbatim
315: *> LIWORK is INTEGER
316: *> The dimension of the array IWORK. LIWORK >= max(1,10*N).
317: *>
318: *> If LIWORK = -1, then a workspace query is assumed; the
319: *> routine only calculates the optimal sizes of the WORK, RWORK
320: *> and IWORK arrays, returns these values as the first entries
321: *> of the WORK, RWORK and IWORK arrays, and no error message
322: *> related to LWORK or LRWORK or LIWORK is issued by XERBLA.
323: *> \endverbatim
324: *>
325: *> \param[out] INFO
326: *> \verbatim
327: *> INFO is INTEGER
328: *> = 0: successful exit
329: *> < 0: if INFO = -i, the i-th argument had an illegal value
330: *> > 0: Internal error
331: *> \endverbatim
332: *
333: * Authors:
334: * ========
335: *
336: *> \author Univ. of Tennessee
337: *> \author Univ. of California Berkeley
338: *> \author Univ. of Colorado Denver
339: *> \author NAG Ltd.
340: *
341: *> \ingroup complex16HEeigen
342: *
343: *> \par Contributors:
344: * ==================
345: *>
346: *> Inderjit Dhillon, IBM Almaden, USA \n
347: *> Osni Marques, LBNL/NERSC, USA \n
348: *> Ken Stanley, Computer Science Division, University of
349: *> California at Berkeley, USA \n
350: *> Jason Riedy, Computer Science Division, University of
351: *> California at Berkeley, USA \n
352: *>
353: * =====================================================================
354: SUBROUTINE ZHEEVR( JOBZ, RANGE, UPLO, N, A, LDA, VL, VU, IL, IU,
355: $ ABSTOL, M, W, Z, LDZ, ISUPPZ, WORK, LWORK,
356: $ RWORK, LRWORK, IWORK, LIWORK, INFO )
357: *
358: * -- LAPACK driver routine --
359: * -- LAPACK is a software package provided by Univ. of Tennessee, --
360: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
361: *
362: * .. Scalar Arguments ..
363: CHARACTER JOBZ, RANGE, UPLO
364: INTEGER IL, INFO, IU, LDA, LDZ, LIWORK, LRWORK, LWORK,
365: $ M, N
366: DOUBLE PRECISION ABSTOL, VL, VU
367: * ..
368: * .. Array Arguments ..
369: INTEGER ISUPPZ( * ), IWORK( * )
370: DOUBLE PRECISION RWORK( * ), W( * )
371: COMPLEX*16 A( LDA, * ), WORK( * ), Z( LDZ, * )
372: * ..
373: *
374: * =====================================================================
375: *
376: * .. Parameters ..
377: DOUBLE PRECISION ZERO, ONE, TWO
378: PARAMETER ( ZERO = 0.0D+0, ONE = 1.0D+0, TWO = 2.0D+0 )
379: * ..
380: * .. Local Scalars ..
381: LOGICAL ALLEIG, INDEIG, LOWER, LQUERY, TEST, VALEIG,
382: $ WANTZ, TRYRAC
383: CHARACTER ORDER
384: INTEGER I, IEEEOK, IINFO, IMAX, INDIBL, INDIFL, INDISP,
385: $ INDIWO, INDRD, INDRDD, INDRE, INDREE, INDRWK,
386: $ INDTAU, INDWK, INDWKN, ISCALE, ITMP1, J, JJ,
387: $ LIWMIN, LLWORK, LLRWORK, LLWRKN, LRWMIN,
388: $ LWKOPT, LWMIN, NB, NSPLIT
389: DOUBLE PRECISION ABSTLL, ANRM, BIGNUM, EPS, RMAX, RMIN, SAFMIN,
390: $ SIGMA, SMLNUM, TMP1, VLL, VUU
391: * ..
392: * .. External Functions ..
393: LOGICAL LSAME
394: INTEGER ILAENV
395: DOUBLE PRECISION DLAMCH, ZLANSY
396: EXTERNAL LSAME, ILAENV, DLAMCH, ZLANSY
397: * ..
398: * .. External Subroutines ..
399: EXTERNAL DCOPY, DSCAL, DSTEBZ, DSTERF, XERBLA, ZDSCAL,
400: $ ZHETRD, ZSTEMR, ZSTEIN, ZSWAP, ZUNMTR
401: * ..
402: * .. Intrinsic Functions ..
403: INTRINSIC DBLE, MAX, MIN, SQRT
404: * ..
405: * .. Executable Statements ..
406: *
407: * Test the input parameters.
408: *
409: IEEEOK = ILAENV( 10, 'ZHEEVR', 'N', 1, 2, 3, 4 )
410: *
411: LOWER = LSAME( UPLO, 'L' )
412: WANTZ = LSAME( JOBZ, 'V' )
413: ALLEIG = LSAME( RANGE, 'A' )
414: VALEIG = LSAME( RANGE, 'V' )
415: INDEIG = LSAME( RANGE, 'I' )
416: *
417: LQUERY = ( ( LWORK.EQ.-1 ) .OR. ( LRWORK.EQ.-1 ) .OR.
418: $ ( LIWORK.EQ.-1 ) )
419: *
420: LRWMIN = MAX( 1, 24*N )
421: LIWMIN = MAX( 1, 10*N )
422: LWMIN = MAX( 1, 2*N )
423: *
424: INFO = 0
425: IF( .NOT.( WANTZ .OR. LSAME( JOBZ, 'N' ) ) ) THEN
426: INFO = -1
427: ELSE IF( .NOT.( ALLEIG .OR. VALEIG .OR. INDEIG ) ) THEN
428: INFO = -2
429: ELSE IF( .NOT.( LOWER .OR. LSAME( UPLO, 'U' ) ) ) THEN
430: INFO = -3
431: ELSE IF( N.LT.0 ) THEN
432: INFO = -4
433: ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
434: INFO = -6
435: ELSE
436: IF( VALEIG ) THEN
437: IF( N.GT.0 .AND. VU.LE.VL )
438: $ INFO = -8
439: ELSE IF( INDEIG ) THEN
440: IF( IL.LT.1 .OR. IL.GT.MAX( 1, N ) ) THEN
441: INFO = -9
442: ELSE IF( IU.LT.MIN( N, IL ) .OR. IU.GT.N ) THEN
443: INFO = -10
444: END IF
445: END IF
446: END IF
447: IF( INFO.EQ.0 ) THEN
448: IF( LDZ.LT.1 .OR. ( WANTZ .AND. LDZ.LT.N ) ) THEN
449: INFO = -15
450: END IF
451: END IF
452: *
453: IF( INFO.EQ.0 ) THEN
454: NB = ILAENV( 1, 'ZHETRD', UPLO, N, -1, -1, -1 )
455: NB = MAX( NB, ILAENV( 1, 'ZUNMTR', UPLO, N, -1, -1, -1 ) )
456: LWKOPT = MAX( ( NB+1 )*N, LWMIN )
457: WORK( 1 ) = LWKOPT
458: RWORK( 1 ) = LRWMIN
459: IWORK( 1 ) = LIWMIN
460: *
461: IF( LWORK.LT.LWMIN .AND. .NOT.LQUERY ) THEN
462: INFO = -18
463: ELSE IF( LRWORK.LT.LRWMIN .AND. .NOT.LQUERY ) THEN
464: INFO = -20
465: ELSE IF( LIWORK.LT.LIWMIN .AND. .NOT.LQUERY ) THEN
466: INFO = -22
467: END IF
468: END IF
469: *
470: IF( INFO.NE.0 ) THEN
471: CALL XERBLA( 'ZHEEVR', -INFO )
472: RETURN
473: ELSE IF( LQUERY ) THEN
474: RETURN
475: END IF
476: *
477: * Quick return if possible
478: *
479: M = 0
480: IF( N.EQ.0 ) THEN
481: WORK( 1 ) = 1
482: RETURN
483: END IF
484: *
485: IF( N.EQ.1 ) THEN
486: WORK( 1 ) = 2
487: IF( ALLEIG .OR. INDEIG ) THEN
488: M = 1
489: W( 1 ) = DBLE( A( 1, 1 ) )
490: ELSE
491: IF( VL.LT.DBLE( A( 1, 1 ) ) .AND. VU.GE.DBLE( A( 1, 1 ) ) )
492: $ THEN
493: M = 1
494: W( 1 ) = DBLE( A( 1, 1 ) )
495: END IF
496: END IF
497: IF( WANTZ ) THEN
498: Z( 1, 1 ) = ONE
499: ISUPPZ( 1 ) = 1
500: ISUPPZ( 2 ) = 1
501: END IF
502: RETURN
503: END IF
504: *
505: * Get machine constants.
506: *
507: SAFMIN = DLAMCH( 'Safe minimum' )
508: EPS = DLAMCH( 'Precision' )
509: SMLNUM = SAFMIN / EPS
510: BIGNUM = ONE / SMLNUM
511: RMIN = SQRT( SMLNUM )
512: RMAX = MIN( SQRT( BIGNUM ), ONE / SQRT( SQRT( SAFMIN ) ) )
513: *
514: * Scale matrix to allowable range, if necessary.
515: *
516: ISCALE = 0
517: ABSTLL = ABSTOL
518: IF (VALEIG) THEN
519: VLL = VL
520: VUU = VU
521: END IF
522: ANRM = ZLANSY( 'M', UPLO, N, A, LDA, RWORK )
523: IF( ANRM.GT.ZERO .AND. ANRM.LT.RMIN ) THEN
524: ISCALE = 1
525: SIGMA = RMIN / ANRM
526: ELSE IF( ANRM.GT.RMAX ) THEN
527: ISCALE = 1
528: SIGMA = RMAX / ANRM
529: END IF
530: IF( ISCALE.EQ.1 ) THEN
531: IF( LOWER ) THEN
532: DO 10 J = 1, N
533: CALL ZDSCAL( N-J+1, SIGMA, A( J, J ), 1 )
534: 10 CONTINUE
535: ELSE
536: DO 20 J = 1, N
537: CALL ZDSCAL( J, SIGMA, A( 1, J ), 1 )
538: 20 CONTINUE
539: END IF
540: IF( ABSTOL.GT.0 )
541: $ ABSTLL = ABSTOL*SIGMA
542: IF( VALEIG ) THEN
543: VLL = VL*SIGMA
544: VUU = VU*SIGMA
545: END IF
546: END IF
547:
548: * Initialize indices into workspaces. Note: The IWORK indices are
549: * used only if DSTERF or ZSTEMR fail.
550:
551: * WORK(INDTAU:INDTAU+N-1) stores the complex scalar factors of the
552: * elementary reflectors used in ZHETRD.
553: INDTAU = 1
554: * INDWK is the starting offset of the remaining complex workspace,
555: * and LLWORK is the remaining complex workspace size.
556: INDWK = INDTAU + N
557: LLWORK = LWORK - INDWK + 1
558:
559: * RWORK(INDRD:INDRD+N-1) stores the real tridiagonal's diagonal
560: * entries.
561: INDRD = 1
562: * RWORK(INDRE:INDRE+N-1) stores the off-diagonal entries of the
563: * tridiagonal matrix from ZHETRD.
564: INDRE = INDRD + N
565: * RWORK(INDRDD:INDRDD+N-1) is a copy of the diagonal entries over
566: * -written by ZSTEMR (the DSTERF path copies the diagonal to W).
567: INDRDD = INDRE + N
568: * RWORK(INDREE:INDREE+N-1) is a copy of the off-diagonal entries over
569: * -written while computing the eigenvalues in DSTERF and ZSTEMR.
570: INDREE = INDRDD + N
571: * INDRWK is the starting offset of the left-over real workspace, and
572: * LLRWORK is the remaining workspace size.
573: INDRWK = INDREE + N
574: LLRWORK = LRWORK - INDRWK + 1
575:
576: * IWORK(INDIBL:INDIBL+M-1) corresponds to IBLOCK in DSTEBZ and
577: * stores the block indices of each of the M<=N eigenvalues.
578: INDIBL = 1
579: * IWORK(INDISP:INDISP+NSPLIT-1) corresponds to ISPLIT in DSTEBZ and
580: * stores the starting and finishing indices of each block.
581: INDISP = INDIBL + N
582: * IWORK(INDIFL:INDIFL+N-1) stores the indices of eigenvectors
583: * that corresponding to eigenvectors that fail to converge in
584: * DSTEIN. This information is discarded; if any fail, the driver
585: * returns INFO > 0.
586: INDIFL = INDISP + N
587: * INDIWO is the offset of the remaining integer workspace.
588: INDIWO = INDIFL + N
589:
590: *
591: * Call ZHETRD to reduce Hermitian matrix to tridiagonal form.
592: *
593: CALL ZHETRD( UPLO, N, A, LDA, RWORK( INDRD ), RWORK( INDRE ),
594: $ WORK( INDTAU ), WORK( INDWK ), LLWORK, IINFO )
595: *
596: * If all eigenvalues are desired
597: * then call DSTERF or ZSTEMR and ZUNMTR.
598: *
599: TEST = .FALSE.
600: IF( INDEIG ) THEN
601: IF( IL.EQ.1 .AND. IU.EQ.N ) THEN
602: TEST = .TRUE.
603: END IF
604: END IF
605: IF( ( ALLEIG.OR.TEST ) .AND. ( IEEEOK.EQ.1 ) ) THEN
606: IF( .NOT.WANTZ ) THEN
607: CALL DCOPY( N, RWORK( INDRD ), 1, W, 1 )
608: CALL DCOPY( N-1, RWORK( INDRE ), 1, RWORK( INDREE ), 1 )
609: CALL DSTERF( N, W, RWORK( INDREE ), INFO )
610: ELSE
611: CALL DCOPY( N-1, RWORK( INDRE ), 1, RWORK( INDREE ), 1 )
612: CALL DCOPY( N, RWORK( INDRD ), 1, RWORK( INDRDD ), 1 )
613: *
614: IF (ABSTOL .LE. TWO*N*EPS) THEN
615: TRYRAC = .TRUE.
616: ELSE
617: TRYRAC = .FALSE.
618: END IF
619: CALL ZSTEMR( JOBZ, 'A', N, RWORK( INDRDD ),
620: $ RWORK( INDREE ), VL, VU, IL, IU, M, W,
621: $ Z, LDZ, N, ISUPPZ, TRYRAC,
622: $ RWORK( INDRWK ), LLRWORK,
623: $ IWORK, LIWORK, INFO )
624: *
625: * Apply unitary matrix used in reduction to tridiagonal
626: * form to eigenvectors returned by ZSTEMR.
627: *
628: IF( WANTZ .AND. INFO.EQ.0 ) THEN
629: INDWKN = INDWK
630: LLWRKN = LWORK - INDWKN + 1
631: CALL ZUNMTR( 'L', UPLO, 'N', N, M, A, LDA,
632: $ WORK( INDTAU ), Z, LDZ, WORK( INDWKN ),
633: $ LLWRKN, IINFO )
634: END IF
635: END IF
636: *
637: *
638: IF( INFO.EQ.0 ) THEN
639: M = N
640: GO TO 30
641: END IF
642: INFO = 0
643: END IF
644: *
645: * Otherwise, call DSTEBZ and, if eigenvectors are desired, ZSTEIN.
646: * Also call DSTEBZ and ZSTEIN if ZSTEMR fails.
647: *
648: IF( WANTZ ) THEN
649: ORDER = 'B'
650: ELSE
651: ORDER = 'E'
652: END IF
653:
654: CALL DSTEBZ( RANGE, ORDER, N, VLL, VUU, IL, IU, ABSTLL,
655: $ RWORK( INDRD ), RWORK( INDRE ), M, NSPLIT, W,
656: $ IWORK( INDIBL ), IWORK( INDISP ), RWORK( INDRWK ),
657: $ IWORK( INDIWO ), INFO )
658: *
659: IF( WANTZ ) THEN
660: CALL ZSTEIN( N, RWORK( INDRD ), RWORK( INDRE ), M, W,
661: $ IWORK( INDIBL ), IWORK( INDISP ), Z, LDZ,
662: $ RWORK( INDRWK ), IWORK( INDIWO ), IWORK( INDIFL ),
663: $ INFO )
664: *
665: * Apply unitary matrix used in reduction to tridiagonal
666: * form to eigenvectors returned by ZSTEIN.
667: *
668: INDWKN = INDWK
669: LLWRKN = LWORK - INDWKN + 1
670: CALL ZUNMTR( 'L', UPLO, 'N', N, M, A, LDA, WORK( INDTAU ), Z,
671: $ LDZ, WORK( INDWKN ), LLWRKN, IINFO )
672: END IF
673: *
674: * If matrix was scaled, then rescale eigenvalues appropriately.
675: *
676: 30 CONTINUE
677: IF( ISCALE.EQ.1 ) THEN
678: IF( INFO.EQ.0 ) THEN
679: IMAX = M
680: ELSE
681: IMAX = INFO - 1
682: END IF
683: CALL DSCAL( IMAX, ONE / SIGMA, W, 1 )
684: END IF
685: *
686: * If eigenvalues are not in order, then sort them, along with
687: * eigenvectors.
688: *
689: IF( WANTZ ) THEN
690: DO 50 J = 1, M - 1
691: I = 0
692: TMP1 = W( J )
693: DO 40 JJ = J + 1, M
694: IF( W( JJ ).LT.TMP1 ) THEN
695: I = JJ
696: TMP1 = W( JJ )
697: END IF
698: 40 CONTINUE
699: *
700: IF( I.NE.0 ) THEN
701: ITMP1 = IWORK( INDIBL+I-1 )
702: W( I ) = W( J )
703: IWORK( INDIBL+I-1 ) = IWORK( INDIBL+J-1 )
704: W( J ) = TMP1
705: IWORK( INDIBL+J-1 ) = ITMP1
706: CALL ZSWAP( N, Z( 1, I ), 1, Z( 1, J ), 1 )
707: END IF
708: 50 CONTINUE
709: END IF
710: *
711: * Set WORK(1) to optimal workspace size.
712: *
713: WORK( 1 ) = LWKOPT
714: RWORK( 1 ) = LRWMIN
715: IWORK( 1 ) = LIWMIN
716: *
717: RETURN
718: *
719: * End of ZHEEVR
720: *
721: END
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