LAPACK  3.5.0
LAPACK: Linear Algebra PACKage
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sget39.f File Reference

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Functions/Subroutines

subroutine sget39 (RMAX, LMAX, NINFO, KNT)
 SGET39

Function/Subroutine Documentation

subroutine sget39 ( real  RMAX,
integer  LMAX,
integer  NINFO,
integer  KNT 
)

SGET39

Purpose:
 SGET39 tests SLAQTR, a routine for solving the real or
 special complex quasi upper triangular system

      op(T)*p = scale*c,
 or
      op(T + iB)*(p+iq) = scale*(c+id),

 in real arithmetic. T is upper quasi-triangular.
 If it is complex, then the first diagonal block of T must be
 1 by 1, B has the special structure

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

 op(A) = A or A', where A' denotes the conjugate transpose of
 the matrix A.

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

 Scale is an output less than or equal to 1, chosen to avoid
 overflow in X.
 This subroutine is specially designed for the condition number
 estimation in the eigenproblem routine STRSNA.

 The test code verifies that the following residual is order 1:

      ||(T+i*B)*(x1+i*x2) - scale*(d1+i*d2)||
    -----------------------------------------
        max(ulp*(||T||+||B||)*(||x1||+||x2||),
            (||T||+||B||)*smlnum/ulp,
            smlnum)

 (The (||T||+||B||)*smlnum/ulp term accounts for possible
  (gradual or nongradual) underflow in x1 and x2.)
Parameters
[out]RMAX
          RMAX is REAL
          Value of the largest test ratio.
[out]LMAX
          LMAX is INTEGER
          Example number where largest test ratio achieved.
[out]NINFO
          NINFO is INTEGER
          Number of examples where INFO is nonzero.
[out]KNT
          KNT is INTEGER
          Total number of examples tested.
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date
November 2011

Definition at line 104 of file sget39.f.

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