LAPACK  3.6.1
LAPACK: Linear Algebra PACKage
subroutine slaqtr ( logical  LTRAN,
logical  LREAL,
integer  N,
real, dimension( ldt, * )  T,
integer  LDT,
real, dimension( * )  B,
real  W,
real  SCALE,
real, dimension( * )  X,
real, dimension( * )  WORK,
integer  INFO 
)

SLAQTR solves a real quasi-triangular system of equations, or a complex quasi-triangular system of special form, in real arithmetic.

Download SLAQTR + dependencies [TGZ] [ZIP] [TXT]

Purpose: 
 SLAQTR solves the real quasi-triangular system

              op(T)*p = scale*c,               if LREAL = .TRUE.

 or the complex quasi-triangular systems

            op(T + iB)*(p+iq) = scale*(c+id),  if LREAL = .FALSE.

 in real arithmetic, where T is upper quasi-triangular.
 If LREAL = .FALSE., then the first diagonal block of T must be
 1 by 1, B is the specially structured matrix

                B = [ b(1) b(2) ... b(n) ]
                    [       w            ]
                    [           w        ]
                    [              .     ]
                    [                 w  ]

 op(A) = A or A**T, A**T denotes the transpose of
 matrix A.

 On input, X = [ c ].  On output, X = [ p ].
               [ d ]                  [ q ]

 This subroutine is designed for the condition number estimation
 in routine STRSNA.
Parameters
[in]LTRAN
          LTRAN is LOGICAL
          On entry, LTRAN specifies the option of conjugate transpose:
             = .FALSE.,    op(T+i*B) = T+i*B,
             = .TRUE.,     op(T+i*B) = (T+i*B)**T.
[in]LREAL
          LREAL is LOGICAL
          On entry, LREAL specifies the input matrix structure:
             = .FALSE.,    the input is complex
             = .TRUE.,     the input is real
[in]N
          N is INTEGER
          On entry, N specifies the order of T+i*B. N >= 0.
[in]T
          T is REAL array, dimension (LDT,N)
          On entry, T contains a matrix in Schur canonical form.
          If LREAL = .FALSE., then the first diagonal block of T must
          be 1 by 1.
[in]LDT
          LDT is INTEGER
          The leading dimension of the matrix T. LDT >= max(1,N).
[in]B
          B is REAL array, dimension (N)
          On entry, B contains the elements to form the matrix
          B as described above.
          If LREAL = .TRUE., B is not referenced.
[in]W
          W is REAL
          On entry, W is the diagonal element of the matrix B.
          If LREAL = .TRUE., W is not referenced.
[out]SCALE
          SCALE is REAL
          On exit, SCALE is the scale factor.
[in,out]X
          X is REAL array, dimension (2*N)
          On entry, X contains the right hand side of the system.
          On exit, X is overwritten by the solution.
[out]WORK
          WORK is REAL array, dimension (N)
[out]INFO
          INFO is INTEGER
          On exit, INFO is set to
             0: successful exit.
               1: the some diagonal 1 by 1 block has been perturbed by
                  a small number SMIN to keep nonsingularity.
               2: the some diagonal 2 by 2 block has been perturbed by
                  a small number in SLALN2 to keep nonsingularity.
          NOTE: In the interests of speed, this routine does not
                check the inputs for errors.
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date
September 2012

Definition at line 167 of file slaqtr.f.

167 *
168 * -- LAPACK auxiliary routine (version 3.4.2) --
169 * -- LAPACK is a software package provided by Univ. of Tennessee, --
170 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
171 * September 2012
172 *
173 * .. Scalar Arguments ..
174  LOGICAL lreal, ltran
175  INTEGER info, ldt, n
176  REAL scale, w
177 * ..
178 * .. Array Arguments ..
179  REAL b( * ), t( ldt, * ), work( * ), x( * )
180 * ..
181 *
182 * =====================================================================
183 *
184 * .. Parameters ..
185  REAL zero, one
186  parameter ( zero = 0.0e+0, one = 1.0e+0 )
187 * ..
188 * .. Local Scalars ..
189  LOGICAL notran
190  INTEGER i, ierr, j, j1, j2, jnext, k, n1, n2
191  REAL bignum, eps, rec, scaloc, si, smin, sminw,
192  $ smlnum, sr, tjj, tmp, xj, xmax, xnorm, z
193 * ..
194 * .. Local Arrays ..
195  REAL d( 2, 2 ), v( 2, 2 )
196 * ..
197 * .. External Functions ..
198  INTEGER isamax
199  REAL sasum, sdot, slamch, slange
200  EXTERNAL isamax, sasum, sdot, slamch, slange
201 * ..
202 * .. External Subroutines ..
203  EXTERNAL saxpy, sladiv, slaln2, sscal
204 * ..
205 * .. Intrinsic Functions ..
206  INTRINSIC abs, max
207 * ..
208 * .. Executable Statements ..
209 *
210 * Do not test the input parameters for errors
211 *
212  notran = .NOT.ltran
213  info = 0
214 *
215 * Quick return if possible
216 *
217  IF( n.EQ.0 )
218  $ RETURN
219 *
220 * Set constants to control overflow
221 *
222  eps = slamch( 'P' )
223  smlnum = slamch( 'S' ) / eps
224  bignum = one / smlnum
225 *
226  xnorm = slange( 'M', n, n, t, ldt, d )
227  IF( .NOT.lreal )
228  $ xnorm = max( xnorm, abs( w ), slange( 'M', n, 1, b, n, d ) )
229  smin = max( smlnum, eps*xnorm )
230 *
231 * Compute 1-norm of each column of strictly upper triangular
232 * part of T to control overflow in triangular solver.
233 *
234  work( 1 ) = zero
235  DO 10 j = 2, n
236  work( j ) = sasum( j-1, t( 1, j ), 1 )
237  10 CONTINUE
238 *
239  IF( .NOT.lreal ) THEN
240  DO 20 i = 2, n
241  work( i ) = work( i ) + abs( b( i ) )
242  20 CONTINUE
243  END IF
244 *
245  n2 = 2*n
246  n1 = n
247  IF( .NOT.lreal )
248  $ n1 = n2
249  k = isamax( n1, x, 1 )
250  xmax = abs( x( k ) )
251  scale = one
252 *
253  IF( xmax.GT.bignum ) THEN
254  scale = bignum / xmax
255  CALL sscal( n1, scale, x, 1 )
256  xmax = bignum
257  END IF
258 *
259  IF( lreal ) THEN
260 *
261  IF( notran ) THEN
262 *
263 * Solve T*p = scale*c
264 *
265  jnext = n
266  DO 30 j = n, 1, -1
267  IF( j.GT.jnext )
268  $ GO TO 30
269  j1 = j
270  j2 = j
271  jnext = j - 1
272  IF( j.GT.1 ) THEN
273  IF( t( j, j-1 ).NE.zero ) THEN
274  j1 = j - 1
275  jnext = j - 2
276  END IF
277  END IF
278 *
279  IF( j1.EQ.j2 ) THEN
280 *
281 * Meet 1 by 1 diagonal block
282 *
283 * Scale to avoid overflow when computing
284 * x(j) = b(j)/T(j,j)
285 *
286  xj = abs( x( j1 ) )
287  tjj = abs( t( j1, j1 ) )
288  tmp = t( j1, j1 )
289  IF( tjj.LT.smin ) THEN
290  tmp = smin
291  tjj = smin
292  info = 1
293  END IF
294 *
295  IF( xj.EQ.zero )
296  $ GO TO 30
297 *
298  IF( tjj.LT.one ) THEN
299  IF( xj.GT.bignum*tjj ) THEN
300  rec = one / xj
301  CALL sscal( n, rec, x, 1 )
302  scale = scale*rec
303  xmax = xmax*rec
304  END IF
305  END IF
306  x( j1 ) = x( j1 ) / tmp
307  xj = abs( x( j1 ) )
308 *
309 * Scale x if necessary to avoid overflow when adding a
310 * multiple of column j1 of T.
311 *
312  IF( xj.GT.one ) THEN
313  rec = one / xj
314  IF( work( j1 ).GT.( bignum-xmax )*rec ) THEN
315  CALL sscal( n, rec, x, 1 )
316  scale = scale*rec
317  END IF
318  END IF
319  IF( j1.GT.1 ) THEN
320  CALL saxpy( j1-1, -x( j1 ), t( 1, j1 ), 1, x, 1 )
321  k = isamax( j1-1, x, 1 )
322  xmax = abs( x( k ) )
323  END IF
324 *
325  ELSE
326 *
327 * Meet 2 by 2 diagonal block
328 *
329 * Call 2 by 2 linear system solve, to take
330 * care of possible overflow by scaling factor.
331 *
332  d( 1, 1 ) = x( j1 )
333  d( 2, 1 ) = x( j2 )
334  CALL slaln2( .false., 2, 1, smin, one, t( j1, j1 ),
335  $ ldt, one, one, d, 2, zero, zero, v, 2,
336  $ scaloc, xnorm, ierr )
337  IF( ierr.NE.0 )
338  $ info = 2
339 *
340  IF( scaloc.NE.one ) THEN
341  CALL sscal( n, scaloc, x, 1 )
342  scale = scale*scaloc
343  END IF
344  x( j1 ) = v( 1, 1 )
345  x( j2 ) = v( 2, 1 )
346 *
347 * Scale V(1,1) (= X(J1)) and/or V(2,1) (=X(J2))
348 * to avoid overflow in updating right-hand side.
349 *
350  xj = max( abs( v( 1, 1 ) ), abs( v( 2, 1 ) ) )
351  IF( xj.GT.one ) THEN
352  rec = one / xj
353  IF( max( work( j1 ), work( j2 ) ).GT.
354  $ ( bignum-xmax )*rec ) THEN
355  CALL sscal( n, rec, x, 1 )
356  scale = scale*rec
357  END IF
358  END IF
359 *
360 * Update right-hand side
361 *
362  IF( j1.GT.1 ) THEN
363  CALL saxpy( j1-1, -x( j1 ), t( 1, j1 ), 1, x, 1 )
364  CALL saxpy( j1-1, -x( j2 ), t( 1, j2 ), 1, x, 1 )
365  k = isamax( j1-1, x, 1 )
366  xmax = abs( x( k ) )
367  END IF
368 *
369  END IF
370 *
371  30 CONTINUE
372 *
373  ELSE
374 *
375 * Solve T**T*p = scale*c
376 *
377  jnext = 1
378  DO 40 j = 1, n
379  IF( j.LT.jnext )
380  $ GO TO 40
381  j1 = j
382  j2 = j
383  jnext = j + 1
384  IF( j.LT.n ) THEN
385  IF( t( j+1, j ).NE.zero ) THEN
386  j2 = j + 1
387  jnext = j + 2
388  END IF
389  END IF
390 *
391  IF( j1.EQ.j2 ) THEN
392 *
393 * 1 by 1 diagonal block
394 *
395 * Scale if necessary to avoid overflow in forming the
396 * right-hand side element by inner product.
397 *
398  xj = abs( x( j1 ) )
399  IF( xmax.GT.one ) THEN
400  rec = one / xmax
401  IF( work( j1 ).GT.( bignum-xj )*rec ) THEN
402  CALL sscal( n, rec, x, 1 )
403  scale = scale*rec
404  xmax = xmax*rec
405  END IF
406  END IF
407 *
408  x( j1 ) = x( j1 ) - sdot( j1-1, t( 1, j1 ), 1, x, 1 )
409 *
410  xj = abs( x( j1 ) )
411  tjj = abs( t( j1, j1 ) )
412  tmp = t( j1, j1 )
413  IF( tjj.LT.smin ) THEN
414  tmp = smin
415  tjj = smin
416  info = 1
417  END IF
418 *
419  IF( tjj.LT.one ) THEN
420  IF( xj.GT.bignum*tjj ) THEN
421  rec = one / xj
422  CALL sscal( n, rec, x, 1 )
423  scale = scale*rec
424  xmax = xmax*rec
425  END IF
426  END IF
427  x( j1 ) = x( j1 ) / tmp
428  xmax = max( xmax, abs( x( j1 ) ) )
429 *
430  ELSE
431 *
432 * 2 by 2 diagonal block
433 *
434 * Scale if necessary to avoid overflow in forming the
435 * right-hand side elements by inner product.
436 *
437  xj = max( abs( x( j1 ) ), abs( x( j2 ) ) )
438  IF( xmax.GT.one ) THEN
439  rec = one / xmax
440  IF( max( work( j2 ), work( j1 ) ).GT.( bignum-xj )*
441  $ rec ) THEN
442  CALL sscal( n, rec, x, 1 )
443  scale = scale*rec
444  xmax = xmax*rec
445  END IF
446  END IF
447 *
448  d( 1, 1 ) = x( j1 ) - sdot( j1-1, t( 1, j1 ), 1, x,
449  $ 1 )
450  d( 2, 1 ) = x( j2 ) - sdot( j1-1, t( 1, j2 ), 1, x,
451  $ 1 )
452 *
453  CALL slaln2( .true., 2, 1, smin, one, t( j1, j1 ),
454  $ ldt, one, one, d, 2, zero, zero, v, 2,
455  $ scaloc, xnorm, ierr )
456  IF( ierr.NE.0 )
457  $ info = 2
458 *
459  IF( scaloc.NE.one ) THEN
460  CALL sscal( n, scaloc, x, 1 )
461  scale = scale*scaloc
462  END IF
463  x( j1 ) = v( 1, 1 )
464  x( j2 ) = v( 2, 1 )
465  xmax = max( abs( x( j1 ) ), abs( x( j2 ) ), xmax )
466 *
467  END IF
468  40 CONTINUE
469  END IF
470 *
471  ELSE
472 *
473  sminw = max( eps*abs( w ), smin )
474  IF( notran ) THEN
475 *
476 * Solve (T + iB)*(p+iq) = c+id
477 *
478  jnext = n
479  DO 70 j = n, 1, -1
480  IF( j.GT.jnext )
481  $ GO TO 70
482  j1 = j
483  j2 = j
484  jnext = j - 1
485  IF( j.GT.1 ) THEN
486  IF( t( j, j-1 ).NE.zero ) THEN
487  j1 = j - 1
488  jnext = j - 2
489  END IF
490  END IF
491 *
492  IF( j1.EQ.j2 ) THEN
493 *
494 * 1 by 1 diagonal block
495 *
496 * Scale if necessary to avoid overflow in division
497 *
498  z = w
499  IF( j1.EQ.1 )
500  $ z = b( 1 )
501  xj = abs( x( j1 ) ) + abs( x( n+j1 ) )
502  tjj = abs( t( j1, j1 ) ) + abs( z )
503  tmp = t( j1, j1 )
504  IF( tjj.LT.sminw ) THEN
505  tmp = sminw
506  tjj = sminw
507  info = 1
508  END IF
509 *
510  IF( xj.EQ.zero )
511  $ GO TO 70
512 *
513  IF( tjj.LT.one ) THEN
514  IF( xj.GT.bignum*tjj ) THEN
515  rec = one / xj
516  CALL sscal( n2, rec, x, 1 )
517  scale = scale*rec
518  xmax = xmax*rec
519  END IF
520  END IF
521  CALL sladiv( x( j1 ), x( n+j1 ), tmp, z, sr, si )
522  x( j1 ) = sr
523  x( n+j1 ) = si
524  xj = abs( x( j1 ) ) + abs( x( n+j1 ) )
525 *
526 * Scale x if necessary to avoid overflow when adding a
527 * multiple of column j1 of T.
528 *
529  IF( xj.GT.one ) THEN
530  rec = one / xj
531  IF( work( j1 ).GT.( bignum-xmax )*rec ) THEN
532  CALL sscal( n2, rec, x, 1 )
533  scale = scale*rec
534  END IF
535  END IF
536 *
537  IF( j1.GT.1 ) THEN
538  CALL saxpy( j1-1, -x( j1 ), t( 1, j1 ), 1, x, 1 )
539  CALL saxpy( j1-1, -x( n+j1 ), t( 1, j1 ), 1,
540  $ x( n+1 ), 1 )
541 *
542  x( 1 ) = x( 1 ) + b( j1 )*x( n+j1 )
543  x( n+1 ) = x( n+1 ) - b( j1 )*x( j1 )
544 *
545  xmax = zero
546  DO 50 k = 1, j1 - 1
547  xmax = max( xmax, abs( x( k ) )+
548  $ abs( x( k+n ) ) )
549  50 CONTINUE
550  END IF
551 *
552  ELSE
553 *
554 * Meet 2 by 2 diagonal block
555 *
556  d( 1, 1 ) = x( j1 )
557  d( 2, 1 ) = x( j2 )
558  d( 1, 2 ) = x( n+j1 )
559  d( 2, 2 ) = x( n+j2 )
560  CALL slaln2( .false., 2, 2, sminw, one, t( j1, j1 ),
561  $ ldt, one, one, d, 2, zero, -w, v, 2,
562  $ scaloc, xnorm, ierr )
563  IF( ierr.NE.0 )
564  $ info = 2
565 *
566  IF( scaloc.NE.one ) THEN
567  CALL sscal( 2*n, scaloc, x, 1 )
568  scale = scaloc*scale
569  END IF
570  x( j1 ) = v( 1, 1 )
571  x( j2 ) = v( 2, 1 )
572  x( n+j1 ) = v( 1, 2 )
573  x( n+j2 ) = v( 2, 2 )
574 *
575 * Scale X(J1), .... to avoid overflow in
576 * updating right hand side.
577 *
578  xj = max( abs( v( 1, 1 ) )+abs( v( 1, 2 ) ),
579  $ abs( v( 2, 1 ) )+abs( v( 2, 2 ) ) )
580  IF( xj.GT.one ) THEN
581  rec = one / xj
582  IF( max( work( j1 ), work( j2 ) ).GT.
583  $ ( bignum-xmax )*rec ) THEN
584  CALL sscal( n2, rec, x, 1 )
585  scale = scale*rec
586  END IF
587  END IF
588 *
589 * Update the right-hand side.
590 *
591  IF( j1.GT.1 ) THEN
592  CALL saxpy( j1-1, -x( j1 ), t( 1, j1 ), 1, x, 1 )
593  CALL saxpy( j1-1, -x( j2 ), t( 1, j2 ), 1, x, 1 )
594 *
595  CALL saxpy( j1-1, -x( n+j1 ), t( 1, j1 ), 1,
596  $ x( n+1 ), 1 )
597  CALL saxpy( j1-1, -x( n+j2 ), t( 1, j2 ), 1,
598  $ x( n+1 ), 1 )
599 *
600  x( 1 ) = x( 1 ) + b( j1 )*x( n+j1 ) +
601  $ b( j2 )*x( n+j2 )
602  x( n+1 ) = x( n+1 ) - b( j1 )*x( j1 ) -
603  $ b( j2 )*x( j2 )
604 *
605  xmax = zero
606  DO 60 k = 1, j1 - 1
607  xmax = max( abs( x( k ) )+abs( x( k+n ) ),
608  $ xmax )
609  60 CONTINUE
610  END IF
611 *
612  END IF
613  70 CONTINUE
614 *
615  ELSE
616 *
617 * Solve (T + iB)**T*(p+iq) = c+id
618 *
619  jnext = 1
620  DO 80 j = 1, n
621  IF( j.LT.jnext )
622  $ GO TO 80
623  j1 = j
624  j2 = j
625  jnext = j + 1
626  IF( j.LT.n ) THEN
627  IF( t( j+1, j ).NE.zero ) THEN
628  j2 = j + 1
629  jnext = j + 2
630  END IF
631  END IF
632 *
633  IF( j1.EQ.j2 ) THEN
634 *
635 * 1 by 1 diagonal block
636 *
637 * Scale if necessary to avoid overflow in forming the
638 * right-hand side element by inner product.
639 *
640  xj = abs( x( j1 ) ) + abs( x( j1+n ) )
641  IF( xmax.GT.one ) THEN
642  rec = one / xmax
643  IF( work( j1 ).GT.( bignum-xj )*rec ) THEN
644  CALL sscal( n2, rec, x, 1 )
645  scale = scale*rec
646  xmax = xmax*rec
647  END IF
648  END IF
649 *
650  x( j1 ) = x( j1 ) - sdot( j1-1, t( 1, j1 ), 1, x, 1 )
651  x( n+j1 ) = x( n+j1 ) - sdot( j1-1, t( 1, j1 ), 1,
652  $ x( n+1 ), 1 )
653  IF( j1.GT.1 ) THEN
654  x( j1 ) = x( j1 ) - b( j1 )*x( n+1 )
655  x( n+j1 ) = x( n+j1 ) + b( j1 )*x( 1 )
656  END IF
657  xj = abs( x( j1 ) ) + abs( x( j1+n ) )
658 *
659  z = w
660  IF( j1.EQ.1 )
661  $ z = b( 1 )
662 *
663 * Scale if necessary to avoid overflow in
664 * complex division
665 *
666  tjj = abs( t( j1, j1 ) ) + abs( z )
667  tmp = t( j1, j1 )
668  IF( tjj.LT.sminw ) THEN
669  tmp = sminw
670  tjj = sminw
671  info = 1
672  END IF
673 *
674  IF( tjj.LT.one ) THEN
675  IF( xj.GT.bignum*tjj ) THEN
676  rec = one / xj
677  CALL sscal( n2, rec, x, 1 )
678  scale = scale*rec
679  xmax = xmax*rec
680  END IF
681  END IF
682  CALL sladiv( x( j1 ), x( n+j1 ), tmp, -z, sr, si )
683  x( j1 ) = sr
684  x( j1+n ) = si
685  xmax = max( abs( x( j1 ) )+abs( x( j1+n ) ), xmax )
686 *
687  ELSE
688 *
689 * 2 by 2 diagonal block
690 *
691 * Scale if necessary to avoid overflow in forming the
692 * right-hand side element by inner product.
693 *
694  xj = max( abs( x( j1 ) )+abs( x( n+j1 ) ),
695  $ abs( x( j2 ) )+abs( x( n+j2 ) ) )
696  IF( xmax.GT.one ) THEN
697  rec = one / xmax
698  IF( max( work( j1 ), work( j2 ) ).GT.
699  $ ( bignum-xj ) / xmax ) THEN
700  CALL sscal( n2, rec, x, 1 )
701  scale = scale*rec
702  xmax = xmax*rec
703  END IF
704  END IF
705 *
706  d( 1, 1 ) = x( j1 ) - sdot( j1-1, t( 1, j1 ), 1, x,
707  $ 1 )
708  d( 2, 1 ) = x( j2 ) - sdot( j1-1, t( 1, j2 ), 1, x,
709  $ 1 )
710  d( 1, 2 ) = x( n+j1 ) - sdot( j1-1, t( 1, j1 ), 1,
711  $ x( n+1 ), 1 )
712  d( 2, 2 ) = x( n+j2 ) - sdot( j1-1, t( 1, j2 ), 1,
713  $ x( n+1 ), 1 )
714  d( 1, 1 ) = d( 1, 1 ) - b( j1 )*x( n+1 )
715  d( 2, 1 ) = d( 2, 1 ) - b( j2 )*x( n+1 )
716  d( 1, 2 ) = d( 1, 2 ) + b( j1 )*x( 1 )
717  d( 2, 2 ) = d( 2, 2 ) + b( j2 )*x( 1 )
718 *
719  CALL slaln2( .true., 2, 2, sminw, one, t( j1, j1 ),
720  $ ldt, one, one, d, 2, zero, w, v, 2,
721  $ scaloc, xnorm, ierr )
722  IF( ierr.NE.0 )
723  $ info = 2
724 *
725  IF( scaloc.NE.one ) THEN
726  CALL sscal( n2, scaloc, x, 1 )
727  scale = scaloc*scale
728  END IF
729  x( j1 ) = v( 1, 1 )
730  x( j2 ) = v( 2, 1 )
731  x( n+j1 ) = v( 1, 2 )
732  x( n+j2 ) = v( 2, 2 )
733  xmax = max( abs( x( j1 ) )+abs( x( n+j1 ) ),
734  $ abs( x( j2 ) )+abs( x( n+j2 ) ), xmax )
735 *
736  END IF
737 *
738  80 CONTINUE
739 *
740  END IF
741 *
742  END IF
743 *
744  RETURN
745 *
746 * End of SLAQTR
747 *
sdot
real function sdot(N, SX, INCX, SY, INCY)
SDOT
Definition: sdot.f:53
isamax
integer function isamax(N, SX, INCX)
ISAMAX
Definition: isamax.f:53
sladiv
subroutine sladiv(A, B, C, D, P, Q)
SLADIV performs complex division in real arithmetic, avoiding unnecessary overflow.
Definition: sladiv.f:93
slaln2
subroutine slaln2(LTRANS, NA, NW, SMIN, CA, A, LDA, D1, D2, B, LDB, WR, WI, X, LDX, SCALE, XNORM, INFO)
SLALN2 solves a 1-by-1 or 2-by-2 linear system of equations of the specified form.
Definition: slaln2.f:220
slange
real function slange(NORM, M, N, A, LDA, WORK)
SLANGE returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value ...
Definition: slange.f:116
sasum
real function sasum(N, SX, INCX)
SASUM
Definition: sasum.f:54
saxpy
subroutine saxpy(N, SA, SX, INCX, SY, INCY)
SAXPY
Definition: saxpy.f:54
sscal
subroutine sscal(N, SA, SX, INCX)
SSCAL
Definition: sscal.f:55
slamch
real function slamch(CMACH)
SLAMCH
Definition: slamch.f:69

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