 LAPACK  3.8.0 LAPACK: Linear Algebra PACKage

## ◆ ilaenv()

 integer function ilaenv ( integer ISPEC, character*( * ) NAME, character*( * ) OPTS, integer N1, integer N2, integer N3, integer N4 )

ILAENV

Purpose:
``` ILAENV returns problem-dependent parameters for the local
environment.  See ISPEC for a description of the parameters.

In this version, the problem-dependent parameters are contained in
the integer array IPARMS in the common block CLAENV and the value
with index ISPEC is copied to ILAENV.  This version of ILAENV is
to be used in conjunction with XLAENV in TESTING and TIMING.```
Parameters
 [in] ISPEC ``` ISPEC is INTEGER Specifies the parameter to be returned as the value of ILAENV. = 1: the optimal blocksize; if this value is 1, an unblocked algorithm will give the best performance. = 2: the minimum block size for which the block routine should be used; if the usable block size is less than this value, an unblocked routine should be used. = 3: the crossover point (in a block routine, for N less than this value, an unblocked routine should be used) = 4: the number of shifts, used in the nonsymmetric eigenvalue routines = 5: the minimum column dimension for blocking to be used; rectangular blocks must have dimension at least k by m, where k is given by ILAENV(2,...) and m by ILAENV(5,...) = 6: the crossover point for the SVD (when reducing an m by n matrix to bidiagonal form, if max(m,n)/min(m,n) exceeds this value, a QR factorization is used first to reduce the matrix to a triangular form.) = 7: the number of processors = 8: the crossover point for the multishift QR and QZ methods for nonsymmetric eigenvalue problems. = 9: maximum size of the subproblems at the bottom of the computation tree in the divide-and-conquer algorithm =10: ieee NaN arithmetic can be trusted not to trap =11: infinity arithmetic can be trusted not to trap 12 <= ISPEC <= 16: xHSEQR or one of its subroutines, see IPARMQ for detailed explanation Other specifications (up to 100) can be added later.``` [in] NAME ``` NAME is CHARACTER*(*) The name of the calling subroutine.``` [in] OPTS ``` OPTS is CHARACTER*(*) The character options to the subroutine NAME, concatenated into a single character string. For example, UPLO = 'U', TRANS = 'T', and DIAG = 'N' for a triangular routine would be specified as OPTS = 'UTN'.``` [in] N1 ` N1 is INTEGER` [in] N2 ` N2 is INTEGER` [in] N3 ` N3 is INTEGER` [in] N4 ``` N4 is INTEGER Problem dimensions for the subroutine NAME; these may not all be required.```
Returns
ILAENV
```          ILAENV is INTEGER
>= 0: the value of the parameter specified by ISPEC
< 0:  if ILAENV = -k, the k-th argument had an illegal value.```
Date
November 2017
Further Details:
```  The following conventions have been used when calling ILAENV from the
LAPACK routines:
1)  OPTS is a concatenation of all of the character options to
subroutine NAME, in the same order that they appear in the
argument list for NAME, even if they are not used in determining
the value of the parameter specified by ISPEC.
2)  The problem dimensions N1, N2, N3, N4 are specified in the order
that they appear in the argument list for NAME.  N1 is used
first, N2 second, and so on, and unused problem dimensions are
passed a value of -1.
3)  The parameter value returned by ILAENV is checked for validity in
the calling subroutine.  For example, ILAENV is used to retrieve
the optimal blocksize for STRTRI as follows:

NB = ILAENV( 1, 'STRTRI', UPLO // DIAG, N, -1, -1, -1 )
IF( NB.LE.1 ) NB = MAX( 1, N )```

Definition at line 83 of file tstiee.f.

83 *
84 * -- LAPACK auxiliary routine (version 3.7.0) --
85 * Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
86 * November 2006
87 *
88 * .. Scalar Arguments ..
89  CHARACTER*( * ) name, opts
90  INTEGER ispec, n1, n2, n3, n4
91 * ..
92 *
93 * Purpose
94 * =======
95 *
96 * ILAENV is called from the LAPACK routines to choose problem-dependent
97 * parameters for the local environment. See ISPEC for a description of
98 * the parameters.
99 *
100 * This version provides a set of parameters which should give good,
101 * but not optimal, performance on many of the currently available
102 * computers. Users are encouraged to modify this subroutine to set
103 * the tuning parameters for their particular machine using the option
104 * and problem size information in the arguments.
105 *
106 * This routine will not function correctly if it is converted to all
107 * lower case. Converting it to all upper case is allowed.
108 *
109 * Arguments:
110 * ==========
111 *
112 * ISPEC (input) INTEGER
113 * Specifies the parameter to be returned as the value of
114 * ILAENV.
115 * = 1: the optimal blocksize; if this value is 1, an unblocked
116 * algorithm will give the best performance.
117 * = 2: the minimum block size for which the block routine
118 * should be used; if the usable block size is less than
119 * this value, an unblocked routine should be used.
120 * = 3: the crossover point (in a block routine, for N less
121 * than this value, an unblocked routine should be used)
122 * = 4: the number of shifts, used in the nonsymmetric
123 * eigenvalue routines
124 * = 5: the minimum column dimension for blocking to be used;
125 * rectangular blocks must have dimension at least k by m,
126 * where k is given by ILAENV(2,...) and m by ILAENV(5,...)
127 * = 6: the crossover point for the SVD (when reducing an m by n
128 * matrix to bidiagonal form, if max(m,n)/min(m,n) exceeds
129 * this value, a QR factorization is used first to reduce
130 * the matrix to a triangular form.)
131 * = 7: the number of processors
132 * = 8: the crossover point for the multishift QR and QZ methods
133 * for nonsymmetric eigenvalue problems.
134 * = 9: maximum size of the subproblems at the bottom of the
135 * computation tree in the divide-and-conquer algorithm
136 * (used by xGELSD and xGESDD)
137 * =10: ieee NaN arithmetic can be trusted not to trap
138 * =11: infinity arithmetic can be trusted not to trap
139 *
140 * NAME (input) CHARACTER*(*)
141 * The name of the calling subroutine, in either upper case or
142 * lower case.
143 *
144 * OPTS (input) CHARACTER*(*)
145 * The character options to the subroutine NAME, concatenated
146 * into a single character string. For example, UPLO = 'U',
147 * TRANS = 'T', and DIAG = 'N' for a triangular routine would
148 * be specified as OPTS = 'UTN'.
149 *
150 * N1 (input) INTEGER
151 * N2 (input) INTEGER
152 * N3 (input) INTEGER
153 * N4 (input) INTEGER
154 * Problem dimensions for the subroutine NAME; these may not all
155 * be required.
156 *
157 * (ILAENV) (output) INTEGER
158 * >= 0: the value of the parameter specified by ISPEC
159 * < 0: if ILAENV = -k, the k-th argument had an illegal value.
160 *
161 * Further Details
162 * ===============
163 *
164 * The following conventions have been used when calling ILAENV from the
165 * LAPACK routines:
166 * 1) OPTS is a concatenation of all of the character options to
167 * subroutine NAME, in the same order that they appear in the
168 * argument list for NAME, even if they are not used in determining
169 * the value of the parameter specified by ISPEC.
170 * 2) The problem dimensions N1, N2, N3, N4 are specified in the order
171 * that they appear in the argument list for NAME. N1 is used
172 * first, N2 second, and so on, and unused problem dimensions are
173 * passed a value of -1.
174 * 3) The parameter value returned by ILAENV is checked for validity in
175 * the calling subroutine. For example, ILAENV is used to retrieve
176 * the optimal blocksize for STRTRI as follows:
177 *
178 * NB = ILAENV( 1, 'STRTRI', UPLO // DIAG, N, -1, -1, -1 )
179 * IF( NB.LE.1 ) NB = MAX( 1, N )
180 *
181 * =====================================================================
182 *
183 * .. Local Scalars ..
184  LOGICAL cname, sname
185  CHARACTER*1 c1
186  CHARACTER*2 c2, c4
187  CHARACTER*3 c3
188  CHARACTER*6 subnam
189  INTEGER i, ic, iz, nb, nbmin, nx
190 * ..
191 * .. Intrinsic Functions ..
192  INTRINSIC char, ichar, int, min, real
193 * ..
194 * .. External Functions ..
195  INTEGER ieeeck
196  EXTERNAL ieeeck
197 * ..
198 * .. Executable Statements ..
199 *
200  GO TO ( 100, 100, 100, 400, 500, 600, 700, 800, 900, 1000,
201  \$ 1100 ) ispec
202 *
203 * Invalid value for ISPEC
204 *
205  ilaenv = -1
206  RETURN
207 *
208  100 CONTINUE
209 *
210 * Convert NAME to upper case if the first character is lower case.
211 *
212  ilaenv = 1
213  subnam = name
214  ic = ichar( subnam( 1:1 ) )
215  iz = ichar( 'Z' )
216  IF( iz.EQ.90 .OR. iz.EQ.122 ) THEN
217 *
218 * ASCII character set
219 *
220  IF( ic.GE.97 .AND. ic.LE.122 ) THEN
221  subnam( 1:1 ) = char( ic-32 )
222  DO 10 i = 2, 6
223  ic = ichar( subnam( i:i ) )
224  IF( ic.GE.97 .AND. ic.LE.122 )
225  \$ subnam( i:i ) = char( ic-32 )
226  10 CONTINUE
227  END IF
228 *
229  ELSE IF( iz.EQ.233 .OR. iz.EQ.169 ) THEN
230 *
231 * EBCDIC character set
232 *
233  IF( ( ic.GE.129 .AND. ic.LE.137 ) .OR.
234  \$ ( ic.GE.145 .AND. ic.LE.153 ) .OR.
235  \$ ( ic.GE.162 .AND. ic.LE.169 ) ) THEN
236  subnam( 1:1 ) = char( ic+64 )
237  DO 20 i = 2, 6
238  ic = ichar( subnam( i:i ) )
239  IF( ( ic.GE.129 .AND. ic.LE.137 ) .OR.
240  \$ ( ic.GE.145 .AND. ic.LE.153 ) .OR.
241  \$ ( ic.GE.162 .AND. ic.LE.169 ) )
242  \$ subnam( i:i ) = char( ic+64 )
243  20 CONTINUE
244  END IF
245 *
246  ELSE IF( iz.EQ.218 .OR. iz.EQ.250 ) THEN
247 *
248 * Prime machines: ASCII+128
249 *
250  IF( ic.GE.225 .AND. ic.LE.250 ) THEN
251  subnam( 1:1 ) = char( ic-32 )
252  DO 30 i = 2, 6
253  ic = ichar( subnam( i:i ) )
254  IF( ic.GE.225 .AND. ic.LE.250 )
255  \$ subnam( i:i ) = char( ic-32 )
256  30 CONTINUE
257  END IF
258  END IF
259 *
260  c1 = subnam( 1:1 )
261  sname = c1.EQ.'S' .OR. c1.EQ.'D'
262  cname = c1.EQ.'C' .OR. c1.EQ.'Z'
263  IF( .NOT.( cname .OR. sname ) )
264  \$ RETURN
265  c2 = subnam( 2:3 )
266  c3 = subnam( 4:6 )
267  c4 = c3( 2:3 )
268 *
269  GO TO ( 110, 200, 300 ) ispec
270 *
271  110 CONTINUE
272 *
273 * ISPEC = 1: block size
274 *
275 * In these examples, separate code is provided for setting NB for
276 * real and complex. We assume that NB will take the same value in
277 * single or double precision.
278 *
279  nb = 1
280 *
281  IF( c2.EQ.'GE' ) THEN
282  IF( c3.EQ.'TRF' ) THEN
283  IF( sname ) THEN
284  nb = 64
285  ELSE
286  nb = 64
287  END IF
288  ELSE IF( c3.EQ.'QRF' .OR. c3.EQ.'RQF' .OR. c3.EQ.'LQF' .OR.
289  \$ c3.EQ.'QLF' ) THEN
290  IF( sname ) THEN
291  nb = 32
292  ELSE
293  nb = 32
294  END IF
295  ELSE IF( c3.EQ.'HRD' ) THEN
296  IF( sname ) THEN
297  nb = 32
298  ELSE
299  nb = 32
300  END IF
301  ELSE IF( c3.EQ.'BRD' ) THEN
302  IF( sname ) THEN
303  nb = 32
304  ELSE
305  nb = 32
306  END IF
307  ELSE IF( c3.EQ.'TRI' ) THEN
308  IF( sname ) THEN
309  nb = 64
310  ELSE
311  nb = 64
312  END IF
313  END IF
314  ELSE IF( c2.EQ.'PO' ) THEN
315  IF( c3.EQ.'TRF' ) THEN
316  IF( sname ) THEN
317  nb = 64
318  ELSE
319  nb = 64
320  END IF
321  END IF
322  ELSE IF( c2.EQ.'SY' ) THEN
323  IF( c3.EQ.'TRF' ) THEN
324  IF( sname ) THEN
325  nb = 64
326  ELSE
327  nb = 64
328  END IF
329  ELSE IF( sname .AND. c3.EQ.'TRD' ) THEN
330  nb = 32
331  ELSE IF( sname .AND. c3.EQ.'GST' ) THEN
332  nb = 64
333  END IF
334  ELSE IF( cname .AND. c2.EQ.'HE' ) THEN
335  IF( c3.EQ.'TRF' ) THEN
336  nb = 64
337  ELSE IF( c3.EQ.'TRD' ) THEN
338  nb = 32
339  ELSE IF( c3.EQ.'GST' ) THEN
340  nb = 64
341  END IF
342  ELSE IF( sname .AND. c2.EQ.'OR' ) THEN
343  IF( c3( 1:1 ).EQ.'G' ) THEN
344  IF( c4.EQ.'QR' .OR. c4.EQ.'RQ' .OR. c4.EQ.'LQ' .OR.
345  \$ c4.EQ.'QL' .OR. c4.EQ.'HR' .OR. c4.EQ.'TR' .OR.
346  \$ c4.EQ.'BR' ) THEN
347  nb = 32
348  END IF
349  ELSE IF( c3( 1:1 ).EQ.'M' ) THEN
350  IF( c4.EQ.'QR' .OR. c4.EQ.'RQ' .OR. c4.EQ.'LQ' .OR.
351  \$ c4.EQ.'QL' .OR. c4.EQ.'HR' .OR. c4.EQ.'TR' .OR.
352  \$ c4.EQ.'BR' ) THEN
353  nb = 32
354  END IF
355  END IF
356  ELSE IF( cname .AND. c2.EQ.'UN' ) THEN
357  IF( c3( 1:1 ).EQ.'G' ) THEN
358  IF( c4.EQ.'QR' .OR. c4.EQ.'RQ' .OR. c4.EQ.'LQ' .OR.
359  \$ c4.EQ.'QL' .OR. c4.EQ.'HR' .OR. c4.EQ.'TR' .OR.
360  \$ c4.EQ.'BR' ) THEN
361  nb = 32
362  END IF
363  ELSE IF( c3( 1:1 ).EQ.'M' ) THEN
364  IF( c4.EQ.'QR' .OR. c4.EQ.'RQ' .OR. c4.EQ.'LQ' .OR.
365  \$ c4.EQ.'QL' .OR. c4.EQ.'HR' .OR. c4.EQ.'TR' .OR.
366  \$ c4.EQ.'BR' ) THEN
367  nb = 32
368  END IF
369  END IF
370  ELSE IF( c2.EQ.'GB' ) THEN
371  IF( c3.EQ.'TRF' ) THEN
372  IF( sname ) THEN
373  IF( n4.LE.64 ) THEN
374  nb = 1
375  ELSE
376  nb = 32
377  END IF
378  ELSE
379  IF( n4.LE.64 ) THEN
380  nb = 1
381  ELSE
382  nb = 32
383  END IF
384  END IF
385  END IF
386  ELSE IF( c2.EQ.'PB' ) THEN
387  IF( c3.EQ.'TRF' ) THEN
388  IF( sname ) THEN
389  IF( n2.LE.64 ) THEN
390  nb = 1
391  ELSE
392  nb = 32
393  END IF
394  ELSE
395  IF( n2.LE.64 ) THEN
396  nb = 1
397  ELSE
398  nb = 32
399  END IF
400  END IF
401  END IF
402  ELSE IF( c2.EQ.'TR' ) THEN
403  IF( c3.EQ.'TRI' ) THEN
404  IF( sname ) THEN
405  nb = 64
406  ELSE
407  nb = 64
408  END IF
409  END IF
410  ELSE IF( c2.EQ.'LA' ) THEN
411  IF( c3.EQ.'UUM' ) THEN
412  IF( sname ) THEN
413  nb = 64
414  ELSE
415  nb = 64
416  END IF
417  END IF
418  ELSE IF( sname .AND. c2.EQ.'ST' ) THEN
419  IF( c3.EQ.'EBZ' ) THEN
420  nb = 1
421  END IF
422  END IF
423  ilaenv = nb
424  RETURN
425 *
426  200 CONTINUE
427 *
428 * ISPEC = 2: minimum block size
429 *
430  nbmin = 2
431  IF( c2.EQ.'GE' ) THEN
432  IF( c3.EQ.'QRF' .OR. c3.EQ.'RQF' .OR. c3.EQ.'LQF' .OR.
433  \$ c3.EQ.'QLF' ) THEN
434  IF( sname ) THEN
435  nbmin = 2
436  ELSE
437  nbmin = 2
438  END IF
439  ELSE IF( c3.EQ.'HRD' ) THEN
440  IF( sname ) THEN
441  nbmin = 2
442  ELSE
443  nbmin = 2
444  END IF
445  ELSE IF( c3.EQ.'BRD' ) THEN
446  IF( sname ) THEN
447  nbmin = 2
448  ELSE
449  nbmin = 2
450  END IF
451  ELSE IF( c3.EQ.'TRI' ) THEN
452  IF( sname ) THEN
453  nbmin = 2
454  ELSE
455  nbmin = 2
456  END IF
457  END IF
458  ELSE IF( c2.EQ.'SY' ) THEN
459  IF( c3.EQ.'TRF' ) THEN
460  IF( sname ) THEN
461  nbmin = 8
462  ELSE
463  nbmin = 8
464  END IF
465  ELSE IF( sname .AND. c3.EQ.'TRD' ) THEN
466  nbmin = 2
467  END IF
468  ELSE IF( cname .AND. c2.EQ.'HE' ) THEN
469  IF( c3.EQ.'TRD' ) THEN
470  nbmin = 2
471  END IF
472  ELSE IF( sname .AND. c2.EQ.'OR' ) THEN
473  IF( c3( 1:1 ).EQ.'G' ) THEN
474  IF( c4.EQ.'QR' .OR. c4.EQ.'RQ' .OR. c4.EQ.'LQ' .OR.
475  \$ c4.EQ.'QL' .OR. c4.EQ.'HR' .OR. c4.EQ.'TR' .OR.
476  \$ c4.EQ.'BR' ) THEN
477  nbmin = 2
478  END IF
479  ELSE IF( c3( 1:1 ).EQ.'M' ) THEN
480  IF( c4.EQ.'QR' .OR. c4.EQ.'RQ' .OR. c4.EQ.'LQ' .OR.
481  \$ c4.EQ.'QL' .OR. c4.EQ.'HR' .OR. c4.EQ.'TR' .OR.
482  \$ c4.EQ.'BR' ) THEN
483  nbmin = 2
484  END IF
485  END IF
486  ELSE IF( cname .AND. c2.EQ.'UN' ) THEN
487  IF( c3( 1:1 ).EQ.'G' ) THEN
488  IF( c4.EQ.'QR' .OR. c4.EQ.'RQ' .OR. c4.EQ.'LQ' .OR.
489  \$ c4.EQ.'QL' .OR. c4.EQ.'HR' .OR. c4.EQ.'TR' .OR.
490  \$ c4.EQ.'BR' ) THEN
491  nbmin = 2
492  END IF
493  ELSE IF( c3( 1:1 ).EQ.'M' ) THEN
494  IF( c4.EQ.'QR' .OR. c4.EQ.'RQ' .OR. c4.EQ.'LQ' .OR.
495  \$ c4.EQ.'QL' .OR. c4.EQ.'HR' .OR. c4.EQ.'TR' .OR.
496  \$ c4.EQ.'BR' ) THEN
497  nbmin = 2
498  END IF
499  END IF
500  END IF
501  ilaenv = nbmin
502  RETURN
503 *
504  300 CONTINUE
505 *
506 * ISPEC = 3: crossover point
507 *
508  nx = 0
509  IF( c2.EQ.'GE' ) THEN
510  IF( c3.EQ.'QRF' .OR. c3.EQ.'RQF' .OR. c3.EQ.'LQF' .OR.
511  \$ c3.EQ.'QLF' ) THEN
512  IF( sname ) THEN
513  nx = 128
514  ELSE
515  nx = 128
516  END IF
517  ELSE IF( c3.EQ.'HRD' ) THEN
518  IF( sname ) THEN
519  nx = 128
520  ELSE
521  nx = 128
522  END IF
523  ELSE IF( c3.EQ.'BRD' ) THEN
524  IF( sname ) THEN
525  nx = 128
526  ELSE
527  nx = 128
528  END IF
529  END IF
530  ELSE IF( c2.EQ.'SY' ) THEN
531  IF( sname .AND. c3.EQ.'TRD' ) THEN
532  nx = 32
533  END IF
534  ELSE IF( cname .AND. c2.EQ.'HE' ) THEN
535  IF( c3.EQ.'TRD' ) THEN
536  nx = 32
537  END IF
538  ELSE IF( sname .AND. c2.EQ.'OR' ) THEN
539  IF( c3( 1:1 ).EQ.'G' ) THEN
540  IF( c4.EQ.'QR' .OR. c4.EQ.'RQ' .OR. c4.EQ.'LQ' .OR.
541  \$ c4.EQ.'QL' .OR. c4.EQ.'HR' .OR. c4.EQ.'TR' .OR.
542  \$ c4.EQ.'BR' ) THEN
543  nx = 128
544  END IF
545  END IF
546  ELSE IF( cname .AND. c2.EQ.'UN' ) THEN
547  IF( c3( 1:1 ).EQ.'G' ) THEN
548  IF( c4.EQ.'QR' .OR. c4.EQ.'RQ' .OR. c4.EQ.'LQ' .OR.
549  \$ c4.EQ.'QL' .OR. c4.EQ.'HR' .OR. c4.EQ.'TR' .OR.
550  \$ c4.EQ.'BR' ) THEN
551  nx = 128
552  END IF
553  END IF
554  END IF
555  ilaenv = nx
556  RETURN
557 *
558  400 CONTINUE
559 *
560 * ISPEC = 4: number of shifts (used by xHSEQR)
561 *
562  ilaenv = 6
563  RETURN
564 *
565  500 CONTINUE
566 *
567 * ISPEC = 5: minimum column dimension (not used)
568 *
569  ilaenv = 2
570  RETURN
571 *
572  600 CONTINUE
573 *
574 * ISPEC = 6: crossover point for SVD (used by xGELSS and xGESVD)
575 *
576  ilaenv = int( REAL( MIN( N1, N2 ) )*1.6e0 )
577  RETURN
578 *
579  700 CONTINUE
580 *
581 * ISPEC = 7: number of processors (not used)
582 *
583  ilaenv = 1
584  RETURN
585 *
586  800 CONTINUE
587 *
588 * ISPEC = 8: crossover point for multishift (used by xHSEQR)
589 *
590  ilaenv = 50
591  RETURN
592 *
593  900 CONTINUE
594 *
595 * ISPEC = 9: maximum size of the subproblems at the bottom of the
596 * computation tree in the divide-and-conquer algorithm
597 * (used by xGELSD and xGESDD)
598 *
599  ilaenv = 25
600  RETURN
601 *
602  1000 CONTINUE
603 *
604 * ISPEC = 10: ieee NaN arithmetic can be trusted not to trap
605 *
606  ilaenv = 1
607  IF (ilaenv .EQ. 1) THEN
608  ilaenv = ieeeck( 0, 0.0, 1.0 )
609  ENDIF
610  RETURN
611 *
612  1100 CONTINUE
613 *
614 * ISPEC = 11: infinity arithmetic can be trusted not to trap
615 *
616  ilaenv = 1
617  IF (ilaenv .EQ. 1) THEN
618  ilaenv = ieeeck( 1, 0.0, 1.0 )
619  ENDIF
620  RETURN
621 *
622 * End of ILAENV
623 *
integer function ieeeck(ISPEC, ZERO, ONE)
Definition: tstiee.f:626
integer function ilaenv(ISPEC, NAME, OPTS, N1, N2, N3, N4)
ILAENV
Definition: tstiee.f:83
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