LAPACK 3.12.0
LAPACK: Linear Algebra PACKage
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◆ slasq6()

subroutine slasq6 ( integer  i0,
integer  n0,
real, dimension( * )  z,
integer  pp,
real  dmin,
real  dmin1,
real  dmin2,
real  dn,
real  dnm1,
real  dnm2 
)

SLASQ6 computes one dqd transform in ping-pong form. Used by sbdsqr and sstegr.

Download SLASQ6 + dependencies [TGZ] [ZIP] [TXT]

Purpose:
 SLASQ6 computes one dqd (shift equal to zero) transform in
 ping-pong form, with protection against underflow and overflow.
Parameters
[in]I0
          I0 is INTEGER
        First index.
[in]N0
          N0 is INTEGER
        Last index.
[in]Z
          Z is REAL array, dimension ( 4*N )
        Z holds the qd array. EMIN is stored in Z(4*N0) to avoid
        an extra argument.
[in]PP
          PP is INTEGER
        PP=0 for ping, PP=1 for pong.
[out]DMIN
          DMIN is REAL
        Minimum value of d.
[out]DMIN1
          DMIN1 is REAL
        Minimum value of d, excluding D( N0 ).
[out]DMIN2
          DMIN2 is REAL
        Minimum value of d, excluding D( N0 ) and D( N0-1 ).
[out]DN
          DN is REAL
        d(N0), the last value of d.
[out]DNM1
          DNM1 is REAL
        d(N0-1).
[out]DNM2
          DNM2 is REAL
        d(N0-2).
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.