1: *> \brief \b ZHETRD_HB2ST reduces a complex Hermitian band matrix A to real symmetric tridiagonal form T
2: *
3: * =========== DOCUMENTATION ===========
4: *
5: * Online html documentation available at
6: * http://www.netlib.org/lapack/explore-html/
7: *
8: *> \htmlonly
9: *> Download ZHETRD_HB2ST + dependencies
10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/zhbtrd_hb2st.f">
11: *> [TGZ]</a>
12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/zhbtrd_hb2st.f">
13: *> [ZIP]</a>
14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/zhbtrd_hb2st.f">
15: *> [TXT]</a>
16: *> \endhtmlonly
17: *
18: * Definition:
19: * ===========
20: *
21: * SUBROUTINE ZHETRD_HB2ST( STAGE1, VECT, UPLO, N, KD, AB, LDAB,
22: * D, E, HOUS, LHOUS, WORK, LWORK, INFO )
23: *
24: * #if defined(_OPENMP)
25: * use omp_lib
26: * #endif
27: *
28: * IMPLICIT NONE
29: *
30: * .. Scalar Arguments ..
31: * CHARACTER STAGE1, UPLO, VECT
32: * INTEGER N, KD, IB, LDAB, LHOUS, LWORK, INFO
33: * ..
34: * .. Array Arguments ..
35: * DOUBLE PRECISION D( * ), E( * )
36: * COMPLEX*16 AB( LDAB, * ), HOUS( * ), WORK( * )
37: * ..
38: *
39: *
40: *> \par Purpose:
41: * =============
42: *>
43: *> \verbatim
44: *>
45: *> ZHETRD_HB2ST reduces a complex Hermitian band matrix A to real symmetric
46: *> tridiagonal form T by a unitary similarity transformation:
47: *> Q**H * A * Q = T.
48: *> \endverbatim
49: *
50: * Arguments:
51: * ==========
52: *
53: *> \param[in] STAGE
54: *> \verbatim
55: *> STAGE is CHARACTER*1
56: *> = 'N': "No": to mention that the stage 1 of the reduction
57: *> from dense to band using the zhetrd_he2hb routine
58: *> was not called before this routine to reproduce AB.
59: *> In other term this routine is called as standalone.
60: *> = 'Y': "Yes": to mention that the stage 1 of the
61: *> reduction from dense to band using the zhetrd_he2hb
62: *> routine has been called to produce AB (e.g., AB is
63: *> the output of zhetrd_he2hb.
64: *> \endverbatim
65: *>
66: *> \param[in] VECT
67: *> \verbatim
68: *> VECT is CHARACTER*1
69: *> = 'N': No need for the Housholder representation,
70: *> and thus LHOUS is of size max(1, 4*N);
71: *> = 'V': the Householder representation is needed to
72: *> either generate or to apply Q later on,
73: *> then LHOUS is to be queried and computed.
74: *> (NOT AVAILABLE IN THIS RELEASE).
75: *> \endverbatim
76: *>
77: *> \param[in] UPLO
78: *> \verbatim
79: *> UPLO is CHARACTER*1
80: *> = 'U': Upper triangle of A is stored;
81: *> = 'L': Lower triangle of A is stored.
82: *> \endverbatim
83: *>
84: *> \param[in] N
85: *> \verbatim
86: *> N is INTEGER
87: *> The order of the matrix A. N >= 0.
88: *> \endverbatim
89: *>
90: *> \param[in] KD
91: *> \verbatim
92: *> KD is INTEGER
93: *> The number of superdiagonals of the matrix A if UPLO = 'U',
94: *> or the number of subdiagonals if UPLO = 'L'. KD >= 0.
95: *> \endverbatim
96: *>
97: *> \param[in,out] AB
98: *> \verbatim
99: *> AB is COMPLEX*16 array, dimension (LDAB,N)
100: *> On entry, the upper or lower triangle of the Hermitian band
101: *> matrix A, stored in the first KD+1 rows of the array. The
102: *> j-th column of A is stored in the j-th column of the array AB
103: *> as follows:
104: *> if UPLO = 'U', AB(kd+1+i-j,j) = A(i,j) for max(1,j-kd)<=i<=j;
105: *> if UPLO = 'L', AB(1+i-j,j) = A(i,j) for j<=i<=min(n,j+kd).
106: *> On exit, the diagonal elements of AB are overwritten by the
107: *> diagonal elements of the tridiagonal matrix T; if KD > 0, the
108: *> elements on the first superdiagonal (if UPLO = 'U') or the
109: *> first subdiagonal (if UPLO = 'L') are overwritten by the
110: *> off-diagonal elements of T; the rest of AB is overwritten by
111: *> values generated during the reduction.
112: *> \endverbatim
113: *>
114: *> \param[in] LDAB
115: *> \verbatim
116: *> LDAB is INTEGER
117: *> The leading dimension of the array AB. LDAB >= KD+1.
118: *> \endverbatim
119: *>
120: *> \param[out] D
121: *> \verbatim
122: *> D is DOUBLE PRECISION array, dimension (N)
123: *> The diagonal elements of the tridiagonal matrix T.
124: *> \endverbatim
125: *>
126: *> \param[out] E
127: *> \verbatim
128: *> E is DOUBLE PRECISION array, dimension (N-1)
129: *> The off-diagonal elements of the tridiagonal matrix T:
130: *> E(i) = T(i,i+1) if UPLO = 'U'; E(i) = T(i+1,i) if UPLO = 'L'.
131: *> \endverbatim
132: *>
133: *> \param[out] HOUS
134: *> \verbatim
135: *> HOUS is COMPLEX*16 array, dimension LHOUS, that
136: *> store the Householder representation.
137: *> \endverbatim
138: *>
139: *> \param[in] LHOUS
140: *> \verbatim
141: *> LHOUS is INTEGER
142: *> The dimension of the array HOUS. LHOUS = MAX(1, dimension)
143: *> If LWORK = -1, or LHOUS=-1,
144: *> then a query is assumed; the routine
145: *> only calculates the optimal size of the HOUS array, returns
146: *> this value as the first entry of the HOUS array, and no error
147: *> message related to LHOUS is issued by XERBLA.
148: *> LHOUS = MAX(1, dimension) where
149: *> dimension = 4*N if VECT='N'
150: *> not available now if VECT='H'
151: *> \endverbatim
152: *>
153: *> \param[out] WORK
154: *> \verbatim
155: *> WORK is COMPLEX*16 array, dimension LWORK.
156: *> \endverbatim
157: *>
158: *> \param[in] LWORK
159: *> \verbatim
160: *> LWORK is INTEGER
161: *> The dimension of the array WORK. LWORK = MAX(1, dimension)
162: *> If LWORK = -1, or LHOUS=-1,
163: *> then a workspace query is assumed; the routine
164: *> only calculates the optimal size of the WORK array, returns
165: *> this value as the first entry of the WORK array, and no error
166: *> message related to LWORK is issued by XERBLA.
167: *> LWORK = MAX(1, dimension) where
168: *> dimension = (2KD+1)*N + KD*NTHREADS
169: *> where KD is the blocking size of the reduction,
170: *> FACTOPTNB is the blocking used by the QR or LQ
171: *> algorithm, usually FACTOPTNB=128 is a good choice
172: *> NTHREADS is the number of threads used when
173: *> openMP compilation is enabled, otherwise =1.
174: *> \endverbatim
175: *>
176: *> \param[out] INFO
177: *> \verbatim
178: *> INFO is INTEGER
179: *> = 0: successful exit
180: *> < 0: if INFO = -i, the i-th argument had an illegal value
181: *> \endverbatim
182: *
183: * Authors:
184: * ========
185: *
186: *> \author Univ. of Tennessee
187: *> \author Univ. of California Berkeley
188: *> \author Univ. of Colorado Denver
189: *> \author NAG Ltd.
190: *
191: *> \date December 2016
192: *
193: *> \ingroup complex16OTHERcomputational
194: *
195: *> \par Further Details:
196: * =====================
197: *>
198: *> \verbatim
199: *>
200: *> Implemented by Azzam Haidar.
201: *>
202: *> All details are available on technical report, SC11, SC13 papers.
203: *>
204: *> Azzam Haidar, Hatem Ltaief, and Jack Dongarra.
205: *> Parallel reduction to condensed forms for symmetric eigenvalue problems
206: *> using aggregated fine-grained and memory-aware kernels. In Proceedings
207: *> of 2011 International Conference for High Performance Computing,
208: *> Networking, Storage and Analysis (SC '11), New York, NY, USA,
209: *> Article 8 , 11 pages.
210: *> http://doi.acm.org/10.1145/2063384.2063394
211: *>
212: *> A. Haidar, J. Kurzak, P. Luszczek, 2013.
213: *> An improved parallel singular value algorithm and its implementation
214: *> for multicore hardware, In Proceedings of 2013 International Conference
215: *> for High Performance Computing, Networking, Storage and Analysis (SC '13).
216: *> Denver, Colorado, USA, 2013.
217: *> Article 90, 12 pages.
218: *> http://doi.acm.org/10.1145/2503210.2503292
219: *>
220: *> A. Haidar, R. Solca, S. Tomov, T. Schulthess and J. Dongarra.
221: *> A novel hybrid CPU-GPU generalized eigensolver for electronic structure
222: *> calculations based on fine-grained memory aware tasks.
223: *> International Journal of High Performance Computing Applications.
224: *> Volume 28 Issue 2, Pages 196-209, May 2014.
225: *> http://hpc.sagepub.com/content/28/2/196
226: *>
227: *> \endverbatim
228: *>
229: * =====================================================================
230: SUBROUTINE ZHETRD_HB2ST( STAGE1, VECT, UPLO, N, KD, AB, LDAB,
231: $ D, E, HOUS, LHOUS, WORK, LWORK, INFO )
232: *
233: *
234: #if defined(_OPENMP)
235: use omp_lib
236: #endif
237: *
238: IMPLICIT NONE
239: *
240: * -- LAPACK computational routine (version 3.7.0) --
241: * -- LAPACK is a software package provided by Univ. of Tennessee, --
242: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
243: * December 2016
244: *
245: * .. Scalar Arguments ..
246: CHARACTER STAGE1, UPLO, VECT
247: INTEGER N, KD, LDAB, LHOUS, LWORK, INFO
248: * ..
249: * .. Array Arguments ..
250: DOUBLE PRECISION D( * ), E( * )
251: COMPLEX*16 AB( LDAB, * ), HOUS( * ), WORK( * )
252: * ..
253: *
254: * =====================================================================
255: *
256: * .. Parameters ..
257: DOUBLE PRECISION RZERO
258: COMPLEX*16 ZERO, ONE
259: PARAMETER ( RZERO = 0.0D+0,
260: $ ZERO = ( 0.0D+0, 0.0D+0 ),
261: $ ONE = ( 1.0D+0, 0.0D+0 ) )
262: * ..
263: * .. Local Scalars ..
264: LOGICAL LQUERY, WANTQ, UPPER, AFTERS1
265: INTEGER I, M, K, IB, SWEEPID, MYID, SHIFT, STT, ST,
266: $ ED, STIND, EDIND, BLKLASTIND, COLPT, THED,
267: $ STEPERCOL, GRSIZ, THGRSIZ, THGRNB, THGRID,
268: $ NBTILES, TTYPE, TID, NTHREADS, DEBUG,
269: $ ABDPOS, ABOFDPOS, DPOS, OFDPOS, AWPOS,
270: $ INDA, INDW, APOS, SIZEA, LDA, INDV, INDTAU,
271: $ SIZEV, SIZETAU, LDV, LHMIN, LWMIN
272: DOUBLE PRECISION ABSTMP
273: COMPLEX*16 TMP
274: * ..
275: * .. External Subroutines ..
276: EXTERNAL ZHB2ST_KERNELS, ZLACPY, ZLASET
277: * ..
278: * .. Intrinsic Functions ..
279: INTRINSIC MIN, MAX, CEILING, DBLE, REAL
280: * ..
281: * .. External Functions ..
282: LOGICAL LSAME
283: INTEGER ILAENV
284: EXTERNAL LSAME, ILAENV
285: * ..
286: * .. Executable Statements ..
287: *
288: * Determine the minimal workspace size required.
289: * Test the input parameters
290: *
291: DEBUG = 0
292: INFO = 0
293: AFTERS1 = LSAME( STAGE1, 'Y' )
294: WANTQ = LSAME( VECT, 'V' )
295: UPPER = LSAME( UPLO, 'U' )
296: LQUERY = ( LWORK.EQ.-1 ) .OR. ( LHOUS.EQ.-1 )
297: *
298: * Determine the block size, the workspace size and the hous size.
299: *
300: IB = ILAENV( 18, 'ZHETRD_HB2ST', VECT, N, KD, -1, -1 )
301: LHMIN = ILAENV( 19, 'ZHETRD_HB2ST', VECT, N, KD, IB, -1 )
302: LWMIN = ILAENV( 20, 'ZHETRD_HB2ST', VECT, N, KD, IB, -1 )
303: *
304: IF( .NOT.AFTERS1 .AND. .NOT.LSAME( STAGE1, 'N' ) ) THEN
305: INFO = -1
306: ELSE IF( .NOT.LSAME( VECT, 'N' ) ) THEN
307: INFO = -2
308: ELSE IF( .NOT.UPPER .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
309: INFO = -3
310: ELSE IF( N.LT.0 ) THEN
311: INFO = -4
312: ELSE IF( KD.LT.0 ) THEN
313: INFO = -5
314: ELSE IF( LDAB.LT.(KD+1) ) THEN
315: INFO = -7
316: ELSE IF( LHOUS.LT.LHMIN .AND. .NOT.LQUERY ) THEN
317: INFO = -11
318: ELSE IF( LWORK.LT.LWMIN .AND. .NOT.LQUERY ) THEN
319: INFO = -13
320: END IF
321: *
322: IF( INFO.EQ.0 ) THEN
323: HOUS( 1 ) = LHMIN
324: WORK( 1 ) = LWMIN
325: END IF
326: *
327: IF( INFO.NE.0 ) THEN
328: CALL XERBLA( 'ZHETRD_HB2ST', -INFO )
329: RETURN
330: ELSE IF( LQUERY ) THEN
331: RETURN
332: END IF
333: *
334: * Quick return if possible
335: *
336: IF( N.EQ.0 ) THEN
337: HOUS( 1 ) = 1
338: WORK( 1 ) = 1
339: RETURN
340: END IF
341: *
342: * Determine pointer position
343: *
344: LDV = KD + IB
345: SIZETAU = 2 * N
346: SIZEV = 2 * N
347: INDTAU = 1
348: INDV = INDTAU + SIZETAU
349: LDA = 2 * KD + 1
350: SIZEA = LDA * N
351: INDA = 1
352: INDW = INDA + SIZEA
353: NTHREADS = 1
354: TID = 0
355: *
356: IF( UPPER ) THEN
357: APOS = INDA + KD
358: AWPOS = INDA
359: DPOS = APOS + KD
360: OFDPOS = DPOS - 1
361: ABDPOS = KD + 1
362: ABOFDPOS = KD
363: ELSE
364: APOS = INDA
365: AWPOS = INDA + KD + 1
366: DPOS = APOS
367: OFDPOS = DPOS + 1
368: ABDPOS = 1
369: ABOFDPOS = 2
370:
371: ENDIF
372: *
373: * Case KD=0:
374: * The matrix is diagonal. We just copy it (convert to "real" for
375: * complex because D is double and the imaginary part should be 0)
376: * and store it in D. A sequential code here is better or
377: * in a parallel environment it might need two cores for D and E
378: *
379: IF( KD.EQ.0 ) THEN
380: DO 30 I = 1, N
381: D( I ) = DBLE( AB( ABDPOS, I ) )
382: 30 CONTINUE
383: DO 40 I = 1, N-1
384: E( I ) = RZERO
385: 40 CONTINUE
386: *
387: HOUS( 1 ) = 1
388: WORK( 1 ) = 1
389: RETURN
390: END IF
391: *
392: * Case KD=1:
393: * The matrix is already Tridiagonal. We have to make diagonal
394: * and offdiagonal elements real, and store them in D and E.
395: * For that, for real precision just copy the diag and offdiag
396: * to D and E while for the COMPLEX case the bulge chasing is
397: * performed to convert the hermetian tridiagonal to symmetric
398: * tridiagonal. A simpler coversion formula might be used, but then
399: * updating the Q matrix will be required and based if Q is generated
400: * or not this might complicate the story.
401: *
402: IF( KD.EQ.1 ) THEN
403: DO 50 I = 1, N
404: D( I ) = DBLE( AB( ABDPOS, I ) )
405: 50 CONTINUE
406: *
407: * make off-diagonal elements real and copy them to E
408: *
409: IF( UPPER ) THEN
410: DO 60 I = 1, N - 1
411: TMP = AB( ABOFDPOS, I+1 )
412: ABSTMP = ABS( TMP )
413: AB( ABOFDPOS, I+1 ) = ABSTMP
414: E( I ) = ABSTMP
415: IF( ABSTMP.NE.RZERO ) THEN
416: TMP = TMP / ABSTMP
417: ELSE
418: TMP = ONE
419: END IF
420: IF( I.LT.N-1 )
421: $ AB( ABOFDPOS, I+2 ) = AB( ABOFDPOS, I+2 )*TMP
422: C IF( WANTZ ) THEN
423: C CALL ZSCAL( N, DCONJG( TMP ), Q( 1, I+1 ), 1 )
424: C END IF
425: 60 CONTINUE
426: ELSE
427: DO 70 I = 1, N - 1
428: TMP = AB( ABOFDPOS, I )
429: ABSTMP = ABS( TMP )
430: AB( ABOFDPOS, I ) = ABSTMP
431: E( I ) = ABSTMP
432: IF( ABSTMP.NE.RZERO ) THEN
433: TMP = TMP / ABSTMP
434: ELSE
435: TMP = ONE
436: END IF
437: IF( I.LT.N-1 )
438: $ AB( ABOFDPOS, I+1 ) = AB( ABOFDPOS, I+1 )*TMP
439: C IF( WANTQ ) THEN
440: C CALL ZSCAL( N, TMP, Q( 1, I+1 ), 1 )
441: C END IF
442: 70 CONTINUE
443: ENDIF
444: *
445: HOUS( 1 ) = 1
446: WORK( 1 ) = 1
447: RETURN
448: END IF
449: *
450: * Main code start here.
451: * Reduce the hermitian band of A to a tridiagonal matrix.
452: *
453: THGRSIZ = N
454: GRSIZ = 1
455: SHIFT = 3
456: NBTILES = CEILING( REAL(N)/REAL(KD) )
457: STEPERCOL = CEILING( REAL(SHIFT)/REAL(GRSIZ) )
458: THGRNB = CEILING( REAL(N-1)/REAL(THGRSIZ) )
459: *
460: CALL ZLACPY( "A", KD+1, N, AB, LDAB, WORK( APOS ), LDA )
461: CALL ZLASET( "A", KD, N, ZERO, ZERO, WORK( AWPOS ), LDA )
462: *
463: *
464: * openMP parallelisation start here
465: *
466: #if defined(_OPENMP)
467: !$OMP PARALLEL PRIVATE( TID, THGRID, BLKLASTIND )
468: !$OMP$ PRIVATE( THED, I, M, K, ST, ED, STT, SWEEPID )
469: !$OMP$ PRIVATE( MYID, TTYPE, COLPT, STIND, EDIND )
470: !$OMP$ SHARED ( UPLO, WANTQ, INDV, INDTAU, HOUS, WORK)
471: !$OMP$ SHARED ( N, KD, IB, NBTILES, LDA, LDV, INDA )
472: !$OMP$ SHARED ( STEPERCOL, THGRNB, THGRSIZ, GRSIZ, SHIFT )
473: !$OMP MASTER
474: #endif
475: *
476: * main bulge chasing loop
477: *
478: DO 100 THGRID = 1, THGRNB
479: STT = (THGRID-1)*THGRSIZ+1
480: THED = MIN( (STT + THGRSIZ -1), (N-1))
481: DO 110 I = STT, N-1
482: ED = MIN( I, THED )
483: IF( STT.GT.ED ) EXIT
484: DO 120 M = 1, STEPERCOL
485: ST = STT
486: DO 130 SWEEPID = ST, ED
487: DO 140 K = 1, GRSIZ
488: MYID = (I-SWEEPID)*(STEPERCOL*GRSIZ)
489: $ + (M-1)*GRSIZ + K
490: IF ( MYID.EQ.1 ) THEN
491: TTYPE = 1
492: ELSE
493: TTYPE = MOD( MYID, 2 ) + 2
494: ENDIF
495:
496: IF( TTYPE.EQ.2 ) THEN
497: COLPT = (MYID/2)*KD + SWEEPID
498: STIND = COLPT-KD+1
499: EDIND = MIN(COLPT,N)
500: BLKLASTIND = COLPT
501: ELSE
502: COLPT = ((MYID+1)/2)*KD + SWEEPID
503: STIND = COLPT-KD+1
504: EDIND = MIN(COLPT,N)
505: IF( ( STIND.GE.EDIND-1 ).AND.
506: $ ( EDIND.EQ.N ) ) THEN
507: BLKLASTIND = N
508: ELSE
509: BLKLASTIND = 0
510: ENDIF
511: ENDIF
512: *
513: * Call the kernel
514: *
515: #if defined(_OPENMP)
516: IF( TTYPE.NE.1 ) THEN
517: !$OMP TASK DEPEND(in:WORK(MYID+SHIFT-1))
518: !$OMP$ DEPEND(in:WORK(MYID-1))
519: !$OMP$ DEPEND(out:WORK(MYID))
520: TID = OMP_GET_THREAD_NUM()
521: CALL ZHB2ST_KERNELS( UPLO, WANTQ, TTYPE,
522: $ STIND, EDIND, SWEEPID, N, KD, IB,
523: $ WORK ( INDA ), LDA,
524: $ HOUS( INDV ), HOUS( INDTAU ), LDV,
525: $ WORK( INDW + TID*KD ) )
526: !$OMP END TASK
527: ELSE
528: !$OMP TASK DEPEND(in:WORK(MYID+SHIFT-1))
529: !$OMP$ DEPEND(out:WORK(MYID))
530: TID = OMP_GET_THREAD_NUM()
531: CALL ZHB2ST_KERNELS( UPLO, WANTQ, TTYPE,
532: $ STIND, EDIND, SWEEPID, N, KD, IB,
533: $ WORK ( INDA ), LDA,
534: $ HOUS( INDV ), HOUS( INDTAU ), LDV,
535: $ WORK( INDW + TID*KD ) )
536: !$OMP END TASK
537: ENDIF
538: #else
539: CALL ZHB2ST_KERNELS( UPLO, WANTQ, TTYPE,
540: $ STIND, EDIND, SWEEPID, N, KD, IB,
541: $ WORK ( INDA ), LDA,
542: $ HOUS( INDV ), HOUS( INDTAU ), LDV,
543: $ WORK( INDW + TID*KD ) )
544: #endif
545: IF ( BLKLASTIND.GE.(N-1) ) THEN
546: STT = STT + 1
547: EXIT
548: ENDIF
549: 140 CONTINUE
550: 130 CONTINUE
551: 120 CONTINUE
552: 110 CONTINUE
553: 100 CONTINUE
554: *
555: #if defined(_OPENMP)
556: !$OMP END MASTER
557: !$OMP END PARALLEL
558: #endif
559: *
560: * Copy the diagonal from A to D. Note that D is REAL thus only
561: * the Real part is needed, the imaginary part should be zero.
562: *
563: DO 150 I = 1, N
564: D( I ) = DBLE( WORK( DPOS+(I-1)*LDA ) )
565: 150 CONTINUE
566: *
567: * Copy the off diagonal from A to E. Note that E is REAL thus only
568: * the Real part is needed, the imaginary part should be zero.
569: *
570: IF( UPPER ) THEN
571: DO 160 I = 1, N-1
572: E( I ) = DBLE( WORK( OFDPOS+I*LDA ) )
573: 160 CONTINUE
574: ELSE
575: DO 170 I = 1, N-1
576: E( I ) = DBLE( WORK( OFDPOS+(I-1)*LDA ) )
577: 170 CONTINUE
578: ENDIF
579: *
580: HOUS( 1 ) = LHMIN
581: WORK( 1 ) = LWMIN
582: RETURN
583: *
584: * End of ZHETRD_HB2ST
585: *
586: END
587:
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