1: *> \brief \b ZLA_PORFSX_EXTENDED
2: *
3: * =========== DOCUMENTATION ===========
4: *
5: * Online html documentation available at
6: * http://www.netlib.org/lapack/explore-html/
7: *
8: *> \htmlonly
9: *> Download ZLA_PORFSX_EXTENDED + dependencies
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11: *> [TGZ]</a>
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13: *> [ZIP]</a>
14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/zla_porfsx_extended.f">
15: *> [TXT]</a>
16: *> \endhtmlonly
17: *
18: * Definition:
19: * ===========
20: *
21: * SUBROUTINE ZLA_PORFSX_EXTENDED( PREC_TYPE, UPLO, N, NRHS, A, LDA,
22: * AF, LDAF, COLEQU, C, B, LDB, Y,
23: * LDY, BERR_OUT, N_NORMS,
24: * ERR_BNDS_NORM, ERR_BNDS_COMP, RES,
25: * AYB, DY, Y_TAIL, RCOND, ITHRESH,
26: * RTHRESH, DZ_UB, IGNORE_CWISE,
27: * INFO )
28: *
29: * .. Scalar Arguments ..
30: * INTEGER INFO, LDA, LDAF, LDB, LDY, N, NRHS, PREC_TYPE,
31: * $ N_NORMS, ITHRESH
32: * CHARACTER UPLO
33: * LOGICAL COLEQU, IGNORE_CWISE
34: * DOUBLE PRECISION RTHRESH, DZ_UB
35: * ..
36: * .. Array Arguments ..
37: * COMPLEX*16 A( LDA, * ), AF( LDAF, * ), B( LDB, * ),
38: * $ Y( LDY, * ), RES( * ), DY( * ), Y_TAIL( * )
39: * DOUBLE PRECISION C( * ), AYB( * ), RCOND, BERR_OUT( * ),
40: * $ ERR_BNDS_NORM( NRHS, * ),
41: * $ ERR_BNDS_COMP( NRHS, * )
42: * ..
43: *
44: *
45: *> \par Purpose:
46: * =============
47: *>
48: *> \verbatim
49: *>
50: *> ZLA_PORFSX_EXTENDED improves the computed solution to a system of
51: *> linear equations by performing extra-precise iterative refinement
52: *> and provides error bounds and backward error estimates for the solution.
53: *> This subroutine is called by ZPORFSX to perform iterative refinement.
54: *> In addition to normwise error bound, the code provides maximum
55: *> componentwise error bound if possible. See comments for ERR_BNDS_NORM
56: *> and ERR_BNDS_COMP for details of the error bounds. Note that this
57: *> subroutine is only resonsible for setting the second fields of
58: *> ERR_BNDS_NORM and ERR_BNDS_COMP.
59: *> \endverbatim
60: *
61: * Arguments:
62: * ==========
63: *
64: *> \param[in] PREC_TYPE
65: *> \verbatim
66: *> PREC_TYPE is INTEGER
67: *> Specifies the intermediate precision to be used in refinement.
68: *> The value is defined by ILAPREC(P) where P is a CHARACTER and
69: *> P = 'S': Single
70: *> = 'D': Double
71: *> = 'I': Indigenous
72: *> = 'X', 'E': Extra
73: *> \endverbatim
74: *>
75: *> \param[in] UPLO
76: *> \verbatim
77: *> UPLO is CHARACTER*1
78: *> = 'U': Upper triangle of A is stored;
79: *> = 'L': Lower triangle of A is stored.
80: *> \endverbatim
81: *>
82: *> \param[in] N
83: *> \verbatim
84: *> N is INTEGER
85: *> The number of linear equations, i.e., the order of the
86: *> matrix A. N >= 0.
87: *> \endverbatim
88: *>
89: *> \param[in] NRHS
90: *> \verbatim
91: *> NRHS is INTEGER
92: *> The number of right-hand-sides, i.e., the number of columns of the
93: *> matrix B.
94: *> \endverbatim
95: *>
96: *> \param[in] A
97: *> \verbatim
98: *> A is COMPLEX*16 array, dimension (LDA,N)
99: *> On entry, the N-by-N matrix A.
100: *> \endverbatim
101: *>
102: *> \param[in] LDA
103: *> \verbatim
104: *> LDA is INTEGER
105: *> The leading dimension of the array A. LDA >= max(1,N).
106: *> \endverbatim
107: *>
108: *> \param[in] AF
109: *> \verbatim
110: *> AF is COMPLEX*16 array, dimension (LDAF,N)
111: *> The triangular factor U or L from the Cholesky factorization
112: *> A = U**T*U or A = L*L**T, as computed by ZPOTRF.
113: *> \endverbatim
114: *>
115: *> \param[in] LDAF
116: *> \verbatim
117: *> LDAF is INTEGER
118: *> The leading dimension of the array AF. LDAF >= max(1,N).
119: *> \endverbatim
120: *>
121: *> \param[in] COLEQU
122: *> \verbatim
123: *> COLEQU is LOGICAL
124: *> If .TRUE. then column equilibration was done to A before calling
125: *> this routine. This is needed to compute the solution and error
126: *> bounds correctly.
127: *> \endverbatim
128: *>
129: *> \param[in] C
130: *> \verbatim
131: *> C is DOUBLE PRECISION array, dimension (N)
132: *> The column scale factors for A. If COLEQU = .FALSE., C
133: *> is not accessed. If C is input, each element of C should be a power
134: *> of the radix to ensure a reliable solution and error estimates.
135: *> Scaling by powers of the radix does not cause rounding errors unless
136: *> the result underflows or overflows. Rounding errors during scaling
137: *> lead to refining with a matrix that is not equivalent to the
138: *> input matrix, producing error estimates that may not be
139: *> reliable.
140: *> \endverbatim
141: *>
142: *> \param[in] B
143: *> \verbatim
144: *> B is COMPLEX*16 array, dimension (LDB,NRHS)
145: *> The right-hand-side matrix B.
146: *> \endverbatim
147: *>
148: *> \param[in] LDB
149: *> \verbatim
150: *> LDB is INTEGER
151: *> The leading dimension of the array B. LDB >= max(1,N).
152: *> \endverbatim
153: *>
154: *> \param[in,out] Y
155: *> \verbatim
156: *> Y is COMPLEX*16 array, dimension
157: *> (LDY,NRHS)
158: *> On entry, the solution matrix X, as computed by ZPOTRS.
159: *> On exit, the improved solution matrix Y.
160: *> \endverbatim
161: *>
162: *> \param[in] LDY
163: *> \verbatim
164: *> LDY is INTEGER
165: *> The leading dimension of the array Y. LDY >= max(1,N).
166: *> \endverbatim
167: *>
168: *> \param[out] BERR_OUT
169: *> \verbatim
170: *> BERR_OUT is DOUBLE PRECISION array, dimension (NRHS)
171: *> On exit, BERR_OUT(j) contains the componentwise relative backward
172: *> error for right-hand-side j from the formula
173: *> max(i) ( abs(RES(i)) / ( abs(op(A_s))*abs(Y) + abs(B_s) )(i) )
174: *> where abs(Z) is the componentwise absolute value of the matrix
175: *> or vector Z. This is computed by ZLA_LIN_BERR.
176: *> \endverbatim
177: *>
178: *> \param[in] N_NORMS
179: *> \verbatim
180: *> N_NORMS is INTEGER
181: *> Determines which error bounds to return (see ERR_BNDS_NORM
182: *> and ERR_BNDS_COMP).
183: *> If N_NORMS >= 1 return normwise error bounds.
184: *> If N_NORMS >= 2 return componentwise error bounds.
185: *> \endverbatim
186: *>
187: *> \param[in,out] ERR_BNDS_NORM
188: *> \verbatim
189: *> ERR_BNDS_NORM is DOUBLE PRECISION array, dimension
190: *> (NRHS, N_ERR_BNDS)
191: *> For each right-hand side, this array contains information about
192: *> various error bounds and condition numbers corresponding to the
193: *> normwise relative error, which is defined as follows:
194: *>
195: *> Normwise relative error in the ith solution vector:
196: *> max_j (abs(XTRUE(j,i) - X(j,i)))
197: *> ------------------------------
198: *> max_j abs(X(j,i))
199: *>
200: *> The array is indexed by the type of error information as described
201: *> below. There currently are up to three pieces of information
202: *> returned.
203: *>
204: *> The first index in ERR_BNDS_NORM(i,:) corresponds to the ith
205: *> right-hand side.
206: *>
207: *> The second index in ERR_BNDS_NORM(:,err) contains the following
208: *> three fields:
209: *> err = 1 "Trust/don't trust" boolean. Trust the answer if the
210: *> reciprocal condition number is less than the threshold
211: *> sqrt(n) * slamch('Epsilon').
212: *>
213: *> err = 2 "Guaranteed" error bound: The estimated forward error,
214: *> almost certainly within a factor of 10 of the true error
215: *> so long as the next entry is greater than the threshold
216: *> sqrt(n) * slamch('Epsilon'). This error bound should only
217: *> be trusted if the previous boolean is true.
218: *>
219: *> err = 3 Reciprocal condition number: Estimated normwise
220: *> reciprocal condition number. Compared with the threshold
221: *> sqrt(n) * slamch('Epsilon') to determine if the error
222: *> estimate is "guaranteed". These reciprocal condition
223: *> numbers are 1 / (norm(Z^{-1},inf) * norm(Z,inf)) for some
224: *> appropriately scaled matrix Z.
225: *> Let Z = S*A, where S scales each row by a power of the
226: *> radix so all absolute row sums of Z are approximately 1.
227: *>
228: *> This subroutine is only responsible for setting the second field
229: *> above.
230: *> See Lapack Working Note 165 for further details and extra
231: *> cautions.
232: *> \endverbatim
233: *>
234: *> \param[in,out] ERR_BNDS_COMP
235: *> \verbatim
236: *> ERR_BNDS_COMP is DOUBLE PRECISION array, dimension
237: *> (NRHS, N_ERR_BNDS)
238: *> For each right-hand side, this array contains information about
239: *> various error bounds and condition numbers corresponding to the
240: *> componentwise relative error, which is defined as follows:
241: *>
242: *> Componentwise relative error in the ith solution vector:
243: *> abs(XTRUE(j,i) - X(j,i))
244: *> max_j ----------------------
245: *> abs(X(j,i))
246: *>
247: *> The array is indexed by the right-hand side i (on which the
248: *> componentwise relative error depends), and the type of error
249: *> information as described below. There currently are up to three
250: *> pieces of information returned for each right-hand side. If
251: *> componentwise accuracy is not requested (PARAMS(3) = 0.0), then
252: *> ERR_BNDS_COMP is not accessed. If N_ERR_BNDS .LT. 3, then at most
253: *> the first (:,N_ERR_BNDS) entries are returned.
254: *>
255: *> The first index in ERR_BNDS_COMP(i,:) corresponds to the ith
256: *> right-hand side.
257: *>
258: *> The second index in ERR_BNDS_COMP(:,err) contains the following
259: *> three fields:
260: *> err = 1 "Trust/don't trust" boolean. Trust the answer if the
261: *> reciprocal condition number is less than the threshold
262: *> sqrt(n) * slamch('Epsilon').
263: *>
264: *> err = 2 "Guaranteed" error bound: The estimated forward error,
265: *> almost certainly within a factor of 10 of the true error
266: *> so long as the next entry is greater than the threshold
267: *> sqrt(n) * slamch('Epsilon'). This error bound should only
268: *> be trusted if the previous boolean is true.
269: *>
270: *> err = 3 Reciprocal condition number: Estimated componentwise
271: *> reciprocal condition number. Compared with the threshold
272: *> sqrt(n) * slamch('Epsilon') to determine if the error
273: *> estimate is "guaranteed". These reciprocal condition
274: *> numbers are 1 / (norm(Z^{-1},inf) * norm(Z,inf)) for some
275: *> appropriately scaled matrix Z.
276: *> Let Z = S*(A*diag(x)), where x is the solution for the
277: *> current right-hand side and S scales each row of
278: *> A*diag(x) by a power of the radix so all absolute row
279: *> sums of Z are approximately 1.
280: *>
281: *> This subroutine is only responsible for setting the second field
282: *> above.
283: *> See Lapack Working Note 165 for further details and extra
284: *> cautions.
285: *> \endverbatim
286: *>
287: *> \param[in] RES
288: *> \verbatim
289: *> RES is COMPLEX*16 array, dimension (N)
290: *> Workspace to hold the intermediate residual.
291: *> \endverbatim
292: *>
293: *> \param[in] AYB
294: *> \verbatim
295: *> AYB is DOUBLE PRECISION array, dimension (N)
296: *> Workspace.
297: *> \endverbatim
298: *>
299: *> \param[in] DY
300: *> \verbatim
301: *> DY is COMPLEX*16 PRECISION array, dimension (N)
302: *> Workspace to hold the intermediate solution.
303: *> \endverbatim
304: *>
305: *> \param[in] Y_TAIL
306: *> \verbatim
307: *> Y_TAIL is COMPLEX*16 array, dimension (N)
308: *> Workspace to hold the trailing bits of the intermediate solution.
309: *> \endverbatim
310: *>
311: *> \param[in] RCOND
312: *> \verbatim
313: *> RCOND is DOUBLE PRECISION
314: *> Reciprocal scaled condition number. This is an estimate of the
315: *> reciprocal Skeel condition number of the matrix A after
316: *> equilibration (if done). If this is less than the machine
317: *> precision (in particular, if it is zero), the matrix is singular
318: *> to working precision. Note that the error may still be small even
319: *> if this number is very small and the matrix appears ill-
320: *> conditioned.
321: *> \endverbatim
322: *>
323: *> \param[in] ITHRESH
324: *> \verbatim
325: *> ITHRESH is INTEGER
326: *> The maximum number of residual computations allowed for
327: *> refinement. The default is 10. For 'aggressive' set to 100 to
328: *> permit convergence using approximate factorizations or
329: *> factorizations other than LU. If the factorization uses a
330: *> technique other than Gaussian elimination, the guarantees in
331: *> ERR_BNDS_NORM and ERR_BNDS_COMP may no longer be trustworthy.
332: *> \endverbatim
333: *>
334: *> \param[in] RTHRESH
335: *> \verbatim
336: *> RTHRESH is DOUBLE PRECISION
337: *> Determines when to stop refinement if the error estimate stops
338: *> decreasing. Refinement will stop when the next solution no longer
339: *> satisfies norm(dx_{i+1}) < RTHRESH * norm(dx_i) where norm(Z) is
340: *> the infinity norm of Z. RTHRESH satisfies 0 < RTHRESH <= 1. The
341: *> default value is 0.5. For 'aggressive' set to 0.9 to permit
342: *> convergence on extremely ill-conditioned matrices. See LAWN 165
343: *> for more details.
344: *> \endverbatim
345: *>
346: *> \param[in] DZ_UB
347: *> \verbatim
348: *> DZ_UB is DOUBLE PRECISION
349: *> Determines when to start considering componentwise convergence.
350: *> Componentwise convergence is only considered after each component
351: *> of the solution Y is stable, which we definte as the relative
352: *> change in each component being less than DZ_UB. The default value
353: *> is 0.25, requiring the first bit to be stable. See LAWN 165 for
354: *> more details.
355: *> \endverbatim
356: *>
357: *> \param[in] IGNORE_CWISE
358: *> \verbatim
359: *> IGNORE_CWISE is LOGICAL
360: *> If .TRUE. then ignore componentwise convergence. Default value
361: *> is .FALSE..
362: *> \endverbatim
363: *>
364: *> \param[out] INFO
365: *> \verbatim
366: *> INFO is INTEGER
367: *> = 0: Successful exit.
368: *> < 0: if INFO = -i, the ith argument to ZPOTRS had an illegal
369: *> value
370: *> \endverbatim
371: *
372: * Authors:
373: * ========
374: *
375: *> \author Univ. of Tennessee
376: *> \author Univ. of California Berkeley
377: *> \author Univ. of Colorado Denver
378: *> \author NAG Ltd.
379: *
380: *> \date November 2011
381: *
382: *> \ingroup complex16POcomputational
383: *
384: * =====================================================================
385: SUBROUTINE ZLA_PORFSX_EXTENDED( PREC_TYPE, UPLO, N, NRHS, A, LDA,
386: $ AF, LDAF, COLEQU, C, B, LDB, Y,
387: $ LDY, BERR_OUT, N_NORMS,
388: $ ERR_BNDS_NORM, ERR_BNDS_COMP, RES,
389: $ AYB, DY, Y_TAIL, RCOND, ITHRESH,
390: $ RTHRESH, DZ_UB, IGNORE_CWISE,
391: $ INFO )
392: *
393: * -- LAPACK computational routine (version 3.4.0) --
394: * -- LAPACK is a software package provided by Univ. of Tennessee, --
395: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
396: * November 2011
397: *
398: * .. Scalar Arguments ..
399: INTEGER INFO, LDA, LDAF, LDB, LDY, N, NRHS, PREC_TYPE,
400: $ N_NORMS, ITHRESH
401: CHARACTER UPLO
402: LOGICAL COLEQU, IGNORE_CWISE
403: DOUBLE PRECISION RTHRESH, DZ_UB
404: * ..
405: * .. Array Arguments ..
406: COMPLEX*16 A( LDA, * ), AF( LDAF, * ), B( LDB, * ),
407: $ Y( LDY, * ), RES( * ), DY( * ), Y_TAIL( * )
408: DOUBLE PRECISION C( * ), AYB( * ), RCOND, BERR_OUT( * ),
409: $ ERR_BNDS_NORM( NRHS, * ),
410: $ ERR_BNDS_COMP( NRHS, * )
411: * ..
412: *
413: * =====================================================================
414: *
415: * .. Local Scalars ..
416: INTEGER UPLO2, CNT, I, J, X_STATE, Z_STATE,
417: $ Y_PREC_STATE
418: DOUBLE PRECISION YK, DYK, YMIN, NORMY, NORMX, NORMDX, DXRAT,
419: $ DZRAT, PREVNORMDX, PREV_DZ_Z, DXRATMAX,
420: $ DZRATMAX, DX_X, DZ_Z, FINAL_DX_X, FINAL_DZ_Z,
421: $ EPS, HUGEVAL, INCR_THRESH
422: LOGICAL INCR_PREC
423: COMPLEX*16 ZDUM
424: * ..
425: * .. Parameters ..
426: INTEGER UNSTABLE_STATE, WORKING_STATE, CONV_STATE,
427: $ NOPROG_STATE, BASE_RESIDUAL, EXTRA_RESIDUAL,
428: $ EXTRA_Y
429: PARAMETER ( UNSTABLE_STATE = 0, WORKING_STATE = 1,
430: $ CONV_STATE = 2, NOPROG_STATE = 3 )
431: PARAMETER ( BASE_RESIDUAL = 0, EXTRA_RESIDUAL = 1,
432: $ EXTRA_Y = 2 )
433: INTEGER FINAL_NRM_ERR_I, FINAL_CMP_ERR_I, BERR_I
434: INTEGER RCOND_I, NRM_RCOND_I, NRM_ERR_I, CMP_RCOND_I
435: INTEGER CMP_ERR_I, PIV_GROWTH_I
436: PARAMETER ( FINAL_NRM_ERR_I = 1, FINAL_CMP_ERR_I = 2,
437: $ BERR_I = 3 )
438: PARAMETER ( RCOND_I = 4, NRM_RCOND_I = 5, NRM_ERR_I = 6 )
439: PARAMETER ( CMP_RCOND_I = 7, CMP_ERR_I = 8,
440: $ PIV_GROWTH_I = 9 )
441: INTEGER LA_LINRX_ITREF_I, LA_LINRX_ITHRESH_I,
442: $ LA_LINRX_CWISE_I
443: PARAMETER ( LA_LINRX_ITREF_I = 1,
444: $ LA_LINRX_ITHRESH_I = 2 )
445: PARAMETER ( LA_LINRX_CWISE_I = 3 )
446: INTEGER LA_LINRX_TRUST_I, LA_LINRX_ERR_I,
447: $ LA_LINRX_RCOND_I
448: PARAMETER ( LA_LINRX_TRUST_I = 1, LA_LINRX_ERR_I = 2 )
449: PARAMETER ( LA_LINRX_RCOND_I = 3 )
450: * ..
451: * .. External Functions ..
452: LOGICAL LSAME
453: EXTERNAL ILAUPLO
454: INTEGER ILAUPLO
455: * ..
456: * .. External Subroutines ..
457: EXTERNAL ZAXPY, ZCOPY, ZPOTRS, ZHEMV, BLAS_ZHEMV_X,
458: $ BLAS_ZHEMV2_X, ZLA_HEAMV, ZLA_WWADDW,
459: $ ZLA_LIN_BERR, DLAMCH
460: DOUBLE PRECISION DLAMCH
461: * ..
462: * .. Intrinsic Functions ..
463: INTRINSIC ABS, DBLE, DIMAG, MAX, MIN
464: * ..
465: * .. Statement Functions ..
466: DOUBLE PRECISION CABS1
467: * ..
468: * .. Statement Function Definitions ..
469: CABS1( ZDUM ) = ABS( DBLE( ZDUM ) ) + ABS( DIMAG( ZDUM ) )
470: * ..
471: * .. Executable Statements ..
472: *
473: IF (INFO.NE.0) RETURN
474: EPS = DLAMCH( 'Epsilon' )
475: HUGEVAL = DLAMCH( 'Overflow' )
476: * Force HUGEVAL to Inf
477: HUGEVAL = HUGEVAL * HUGEVAL
478: * Using HUGEVAL may lead to spurious underflows.
479: INCR_THRESH = DBLE(N) * EPS
480:
481: IF (LSAME (UPLO, 'L')) THEN
482: UPLO2 = ILAUPLO( 'L' )
483: ELSE
484: UPLO2 = ILAUPLO( 'U' )
485: ENDIF
486:
487: DO J = 1, NRHS
488: Y_PREC_STATE = EXTRA_RESIDUAL
489: IF (Y_PREC_STATE .EQ. EXTRA_Y) THEN
490: DO I = 1, N
491: Y_TAIL( I ) = 0.0D+0
492: END DO
493: END IF
494:
495: DXRAT = 0.0D+0
496: DXRATMAX = 0.0D+0
497: DZRAT = 0.0D+0
498: DZRATMAX = 0.0D+0
499: FINAL_DX_X = HUGEVAL
500: FINAL_DZ_Z = HUGEVAL
501: PREVNORMDX = HUGEVAL
502: PREV_DZ_Z = HUGEVAL
503: DZ_Z = HUGEVAL
504: DX_X = HUGEVAL
505:
506: X_STATE = WORKING_STATE
507: Z_STATE = UNSTABLE_STATE
508: INCR_PREC = .FALSE.
509:
510: DO CNT = 1, ITHRESH
511: *
512: * Compute residual RES = B_s - op(A_s) * Y,
513: * op(A) = A, A**T, or A**H depending on TRANS (and type).
514: *
515: CALL ZCOPY( N, B( 1, J ), 1, RES, 1 )
516: IF (Y_PREC_STATE .EQ. BASE_RESIDUAL) THEN
517: CALL ZHEMV(UPLO, N, DCMPLX(-1.0D+0), A, LDA, Y(1,J), 1,
518: $ DCMPLX(1.0D+0), RES, 1)
519: ELSE IF (Y_PREC_STATE .EQ. EXTRA_RESIDUAL) THEN
520: CALL BLAS_ZHEMV_X(UPLO2, N, DCMPLX(-1.0D+0), A, LDA,
521: $ Y( 1, J ), 1, DCMPLX(1.0D+0), RES, 1, PREC_TYPE)
522: ELSE
523: CALL BLAS_ZHEMV2_X(UPLO2, N, DCMPLX(-1.0D+0), A, LDA,
524: $ Y(1, J), Y_TAIL, 1, DCMPLX(1.0D+0), RES, 1,
525: $ PREC_TYPE)
526: END IF
527:
528: ! XXX: RES is no longer needed.
529: CALL ZCOPY( N, RES, 1, DY, 1 )
530: CALL ZPOTRS( UPLO, N, 1, AF, LDAF, DY, N, INFO)
531: *
532: * Calculate relative changes DX_X, DZ_Z and ratios DXRAT, DZRAT.
533: *
534: NORMX = 0.0D+0
535: NORMY = 0.0D+0
536: NORMDX = 0.0D+0
537: DZ_Z = 0.0D+0
538: YMIN = HUGEVAL
539:
540: DO I = 1, N
541: YK = CABS1(Y(I, J))
542: DYK = CABS1(DY(I))
543:
544: IF (YK .NE. 0.0D+0) THEN
545: DZ_Z = MAX( DZ_Z, DYK / YK )
546: ELSE IF (DYK .NE. 0.0D+0) THEN
547: DZ_Z = HUGEVAL
548: END IF
549:
550: YMIN = MIN( YMIN, YK )
551:
552: NORMY = MAX( NORMY, YK )
553:
554: IF ( COLEQU ) THEN
555: NORMX = MAX(NORMX, YK * C(I))
556: NORMDX = MAX(NORMDX, DYK * C(I))
557: ELSE
558: NORMX = NORMY
559: NORMDX = MAX(NORMDX, DYK)
560: END IF
561: END DO
562:
563: IF (NORMX .NE. 0.0D+0) THEN
564: DX_X = NORMDX / NORMX
565: ELSE IF (NORMDX .EQ. 0.0D+0) THEN
566: DX_X = 0.0D+0
567: ELSE
568: DX_X = HUGEVAL
569: END IF
570:
571: DXRAT = NORMDX / PREVNORMDX
572: DZRAT = DZ_Z / PREV_DZ_Z
573: *
574: * Check termination criteria.
575: *
576: IF (YMIN*RCOND .LT. INCR_THRESH*NORMY
577: $ .AND. Y_PREC_STATE .LT. EXTRA_Y)
578: $ INCR_PREC = .TRUE.
579:
580: IF (X_STATE .EQ. NOPROG_STATE .AND. DXRAT .LE. RTHRESH)
581: $ X_STATE = WORKING_STATE
582: IF (X_STATE .EQ. WORKING_STATE) THEN
583: IF (DX_X .LE. EPS) THEN
584: X_STATE = CONV_STATE
585: ELSE IF (DXRAT .GT. RTHRESH) THEN
586: IF (Y_PREC_STATE .NE. EXTRA_Y) THEN
587: INCR_PREC = .TRUE.
588: ELSE
589: X_STATE = NOPROG_STATE
590: END IF
591: ELSE
592: IF (DXRAT .GT. DXRATMAX) DXRATMAX = DXRAT
593: END IF
594: IF (X_STATE .GT. WORKING_STATE) FINAL_DX_X = DX_X
595: END IF
596:
597: IF (Z_STATE .EQ. UNSTABLE_STATE .AND. DZ_Z .LE. DZ_UB)
598: $ Z_STATE = WORKING_STATE
599: IF (Z_STATE .EQ. NOPROG_STATE .AND. DZRAT .LE. RTHRESH)
600: $ Z_STATE = WORKING_STATE
601: IF (Z_STATE .EQ. WORKING_STATE) THEN
602: IF (DZ_Z .LE. EPS) THEN
603: Z_STATE = CONV_STATE
604: ELSE IF (DZ_Z .GT. DZ_UB) THEN
605: Z_STATE = UNSTABLE_STATE
606: DZRATMAX = 0.0D+0
607: FINAL_DZ_Z = HUGEVAL
608: ELSE IF (DZRAT .GT. RTHRESH) THEN
609: IF (Y_PREC_STATE .NE. EXTRA_Y) THEN
610: INCR_PREC = .TRUE.
611: ELSE
612: Z_STATE = NOPROG_STATE
613: END IF
614: ELSE
615: IF (DZRAT .GT. DZRATMAX) DZRATMAX = DZRAT
616: END IF
617: IF (Z_STATE .GT. WORKING_STATE) FINAL_DZ_Z = DZ_Z
618: END IF
619:
620: IF ( X_STATE.NE.WORKING_STATE.AND.
621: $ (IGNORE_CWISE.OR.Z_STATE.NE.WORKING_STATE) )
622: $ GOTO 666
623:
624: IF (INCR_PREC) THEN
625: INCR_PREC = .FALSE.
626: Y_PREC_STATE = Y_PREC_STATE + 1
627: DO I = 1, N
628: Y_TAIL( I ) = 0.0D+0
629: END DO
630: END IF
631:
632: PREVNORMDX = NORMDX
633: PREV_DZ_Z = DZ_Z
634: *
635: * Update soluton.
636: *
637: IF (Y_PREC_STATE .LT. EXTRA_Y) THEN
638: CALL ZAXPY( N, DCMPLX(1.0D+0), DY, 1, Y(1,J), 1 )
639: ELSE
640: CALL ZLA_WWADDW(N, Y(1,J), Y_TAIL, DY)
641: END IF
642:
643: END DO
644: * Target of "IF (Z_STOP .AND. X_STOP)". Sun's f77 won't EXIT.
645: 666 CONTINUE
646: *
647: * Set final_* when cnt hits ithresh.
648: *
649: IF (X_STATE .EQ. WORKING_STATE) FINAL_DX_X = DX_X
650: IF (Z_STATE .EQ. WORKING_STATE) FINAL_DZ_Z = DZ_Z
651: *
652: * Compute error bounds.
653: *
654: IF (N_NORMS .GE. 1) THEN
655: ERR_BNDS_NORM( J, LA_LINRX_ERR_I ) =
656: $ FINAL_DX_X / (1 - DXRATMAX)
657: END IF
658: IF (N_NORMS .GE. 2) THEN
659: ERR_BNDS_COMP( J, LA_LINRX_ERR_I ) =
660: $ FINAL_DZ_Z / (1 - DZRATMAX)
661: END IF
662: *
663: * Compute componentwise relative backward error from formula
664: * max(i) ( abs(R(i)) / ( abs(op(A_s))*abs(Y) + abs(B_s) )(i) )
665: * where abs(Z) is the componentwise absolute value of the matrix
666: * or vector Z.
667: *
668: * Compute residual RES = B_s - op(A_s) * Y,
669: * op(A) = A, A**T, or A**H depending on TRANS (and type).
670: *
671: CALL ZCOPY( N, B( 1, J ), 1, RES, 1 )
672: CALL ZHEMV(UPLO, N, DCMPLX(-1.0D+0), A, LDA, Y(1,J), 1,
673: $ DCMPLX(1.0D+0), RES, 1)
674:
675: DO I = 1, N
676: AYB( I ) = CABS1( B( I, J ) )
677: END DO
678: *
679: * Compute abs(op(A_s))*abs(Y) + abs(B_s).
680: *
681: CALL ZLA_HEAMV (UPLO2, N, 1.0D+0,
682: $ A, LDA, Y(1, J), 1, 1.0D+0, AYB, 1)
683:
684: CALL ZLA_LIN_BERR (N, N, 1, RES, AYB, BERR_OUT(J))
685: *
686: * End of loop for each RHS.
687: *
688: END DO
689: *
690: RETURN
691: END
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