LAPACK 3.11.0
LAPACK: Linear Algebra PACKage
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◆ iparmq()

integer function iparmq ( integer  ISPEC,
character, dimension( * )  NAME,
character, dimension( * )  OPTS,
integer  N,
integer  ILO,
integer  IHI,
integer  LWORK 
)

Definition at line 301 of file ilaenv.f.

302*
303 INTEGER INMIN, INWIN, INIBL, ISHFTS, IACC22
304 parameter( inmin = 12, inwin = 13, inibl = 14,
305 $ ishfts = 15, iacc22 = 16 )
306 INTEGER NMIN, K22MIN, KACMIN, NIBBLE, KNWSWP
307 parameter( nmin = 11, k22min = 14, kacmin = 14,
308 $ nibble = 14, knwswp = 500 )
309 REAL TWO
310 parameter( two = 2.0 )
311* ..
312* .. Scalar Arguments ..
313 INTEGER IHI, ILO, ISPEC, LWORK, N
314 CHARACTER NAME*( * ), OPTS*( * )
315* ..
316* .. Local Scalars ..
317 INTEGER NH, NS
318* ..
319* .. Intrinsic Functions ..
320 INTRINSIC log, max, mod, nint, real
321* ..
322* .. Executable Statements ..
323 IF( ( ispec.EQ.ishfts ) .OR. ( ispec.EQ.inwin ) .OR.
324 $ ( ispec.EQ.iacc22 ) ) THEN
325*
326* ==== Set the number simultaneous shifts ====
327*
328 nh = ihi - ilo + 1
329 ns = 2
330 IF( nh.GE.30 )
331 $ ns = 4
332 IF( nh.GE.60 )
333 $ ns = 10
334 IF( nh.GE.150 )
335 $ ns = max( 10, nh / nint( log( real( nh ) ) / log( two ) ) )
336 IF( nh.GE.590 )
337 $ ns = 64
338 IF( nh.GE.3000 )
339 $ ns = 128
340 IF( nh.GE.6000 )
341 $ ns = 256
342 ns = max( 2, ns-mod( ns, 2 ) )
343 END IF
344*
345 IF( ispec.EQ.inmin ) THEN
346*
347*
348* ===== Matrices of order smaller than NMIN get sent
349* . to LAHQR, the classic double shift algorithm.
350* . This must be at least 11. ====
351*
352 iparmq = nmin
353*
354 ELSE IF( ispec.EQ.inibl ) THEN
355*
356* ==== INIBL: skip a multi-shift qr iteration and
357* . whenever aggressive early deflation finds
358* . at least (NIBBLE*(window size)/100) deflations. ====
359*
360 iparmq = nibble
361*
362 ELSE IF( ispec.EQ.ishfts ) THEN
363*
364* ==== NSHFTS: The number of simultaneous shifts =====
365*
366 iparmq = ns
367*
368 ELSE IF( ispec.EQ.inwin ) THEN
369*
370* ==== NW: deflation window size. ====
371*
372 IF( nh.LE.knwswp ) THEN
373 iparmq = ns
374 ELSE
375 iparmq = 3*ns / 2
376 END IF
377*
378 ELSE IF( ispec.EQ.iacc22 ) THEN
379*
380* ==== IACC22: Whether to accumulate reflections
381* . before updating the far-from-diagonal elements
382* . and whether to use 2-by-2 block structure while
383* . doing it. A small amount of work could be saved
384* . by making this choice dependent also upon the
385* . NH=IHI-ILO+1.
386*
387 iparmq = 0
388 IF( ns.GE.kacmin )
389 $ iparmq = 1
390 IF( ns.GE.k22min )
391 $ iparmq = 2
392*
393 ELSE
394* ===== invalid value of ispec =====
395 iparmq = -1
396*
397 END IF
398*
399* ==== End of IPARMQ ====
400*
integer function iparmq(ISPEC, NAME, OPTS, N, ILO, IHI, LWORK)
IPARMQ
Definition: iparmq.f:230
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