dget31.f - Man Page

subroutine dget31 (rmax, lmax, ninfo, knt)
DGET31

DGET31

Purpose:

 DGET31 tests DLALN2, a routine for solving

    (ca A - w D)X = sB

 where A is an NA by NA matrix (NA=1 or 2 only), w is a real (NW=1) or
 complex (NW=2) constant, ca is a real constant, D is an NA by NA real
 diagonal matrix, and B is an NA by NW matrix (when NW=2 the second
 column of B contains the imaginary part of the solution).  The code
 returns X and s, where s is a scale factor, less than or equal to 1,
 which is chosen to avoid overflow in X.

 If any singular values of ca A-w D are less than another input
 parameter SMIN, they are perturbed up to SMIN.

 The test condition is that the scaled residual

     norm( (ca A-w D)*X - s*B ) /
           ( max( ulp*norm(ca A-w D), SMIN )*norm(X) )

 should be on the order of 1.  Here, ulp is the machine precision.
 Also, it is verified that SCALE is less than or equal to 1, and that
 XNORM = infinity-norm(X).

Parameters

RMAX

          RMAX is DOUBLE PRECISION
          Value of the largest test ratio.

LMAX

          LMAX is INTEGER
          Example number where largest test ratio achieved.

NINFO

          NINFO is INTEGER array, dimension (2)
          NINFO(1) = number of examples with INFO less than 0
          NINFO(2) = number of examples with INFO greater than 0

KNT

          KNT is INTEGER
          Total number of examples tested.

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 90 of file dget31.f.