01: Úvod do vědeckého počítání

*        ==== Hope for the best. ====
*
         INFO = 0
*
*        ==== Set up job flags for ILAENV. ====
*
         IF( WANTT ) THEN
            JBCMPZ( 1: 1 ) = 'S'
         ELSE
            JBCMPZ( 1: 1 ) = 'E'
         END IF
         IF( WANTZ ) THEN
            JBCMPZ( 2: 2 ) = 'V'
         ELSE
            JBCMPZ( 2: 2 ) = 'N'
         END IF
*
*        ==== NWR = recommended deflation window size.  At this
*        .    point,  N .GT. NTINY = 11, so there is enough
*        .    subdiagonal workspace for NWR.GE.2 as required.
*        .    (In fact, there is enough subdiagonal space for
*        .    NWR.GE.3.) ====
*
         NWR = ILAENV( 13, 'ZLAQR4', JBCMPZ, N, ILO, IHI, LWORK )
         NWR = MAX( 2, NWR )
         NWR = MIN( IHI-ILO+1, ( N-1 ) / 3, NWR )
*
*        ==== NSR = recommended number of simultaneous shifts.
*        .    At this point N .GT. NTINY = 11, so there is at
*        .    enough subdiagonal workspace for NSR to be even
*        .    and greater than or equal to two as required. ====
*
         NSR = ILAENV( 15, 'ZLAQR4', JBCMPZ, N, ILO, IHI, LWORK )
         NSR = MIN( NSR, ( N+6 ) / 9, IHI-ILO )
         NSR = MAX( 2, NSR-MOD( NSR, 2 ) )

*           ==== Select deflation window size:
*           .    Typical Case:
*           .      If possible and advisable, nibble the entire
*           .      active block.  If not, use size MIN(NWR,NWMAX)
*           .      or MIN(NWR+1,NWMAX) depending upon which has
*           .      the smaller corresponding subdiagonal entry
*           .      (a heuristic).
*           .
*           .    Exceptional Case:
*           .      If there have been no deflations in KEXNW or
*           .      more iterations, then vary the deflation window
*           .      size.   At first, because, larger windows are,
*           .      in general, more powerful than smaller ones,
*           .      rapidly increase the window to the maximum possible.
*           .      Then, gradually reduce the window size. ====
*
            NH = KBOT - KTOP + 1
            NWUPBD = MIN( NH, NWMAX )
            IF( NDFL.LT.KEXNW ) THEN
               NW = MIN( NWUPBD, NWR )
            ELSE
               NW = MIN( NWUPBD, 2*NW )
            END IF
            IF( NW.LT.NWMAX ) THEN
               IF( NW.GE.NH-1 ) THEN
                  NW = NH
               ELSE
                  KWTOP = KBOT - NW + 1
                  IF( CABS1( H( KWTOP, KWTOP-1 ) ).GT.
     $                CABS1( H( KWTOP-1, KWTOP-2 ) ) )NW = NW + 1
               END IF
            END IF
            IF( NDFL.LT.KEXNW ) THEN
               NDEC = -1
            ELSE IF( NDEC.GE.0 .OR. NW.GE.NWUPBD ) THEN
               NDEC = NDEC + 1
               IF( NW-NDEC.LT.2 )
     $            NDEC = 0
               NW = NW - NDEC
            END IF