TESTING/EIG/dget53.f(3)

NAME
TESTING/EIG/dget53.f

SYNOPSIS

  Functions/Subroutines
subroutine dget53 (a, lda, b, ldb, scale, wr, wi, result, info)
DGET53

Function/Subroutine Documentation

  subroutine dget53 (double precision, dimension( lda, * ) a, integer lda, double precision, dimension( ldb, * ) b, integer ldb, double precision scale, double precision wr, double precision wi, double precision result, integer info)

DGET53

Purpose:

     DGET53  checks the generalized eigenvalues computed by DLAG2.
     The basic test for an eigenvalue is:
                                  | det( s A - w B ) |
         RESULT =  ---------------------------------------------------
                   ulp max( s norm(A), |w| norm(B) )*norm( s A - w B )
     Two 'safety checks' are performed:
     (1)  ulp*max( s*norm(A), |w|*norm(B) )  must be at least
          safe_minimum.  This insures that the test performed is
          not essentially  det(0*A + 0*B)=0.
     (2)  s*norm(A) + |w|*norm(B) must be less than 1/safe_minimum.
          This insures that  s*A - w*B  will not overflow.
     If these tests are not passed, then  s  and  w  are scaled and
     tested anyway, if this is possible.

Parameters
    A

              A is DOUBLE PRECISION array, dimension (LDA, 2)
              The 2x2 matrix A.

    LDA

              LDA is INTEGER
              The leading dimension of A.  It must be at least 2.

    B

              B is DOUBLE PRECISION array, dimension (LDB, N)
              The 2x2 upper-triangular matrix B.

    LDB

              LDB is INTEGER
              The leading dimension of B.  It must be at least 2.

    SCALE

              SCALE is DOUBLE PRECISION
              The 'scale factor' s in the formula  s A - w B .  It is
              assumed to be non-negative.

    WR

              WR is DOUBLE PRECISION
              The real part of the eigenvalue  w  in the formula
              s A - w B .

    WI

              WI is DOUBLE PRECISION
              The imaginary part of the eigenvalue  w  in the formula
              s A - w B .

    RESULT

              RESULT is DOUBLE PRECISION
              If INFO is 2 or less, the value computed by the test
                 described above.
              If INFO=3, this will just be 1/ulp.

    INFO

              INFO is INTEGER
              =0:  The input data pass the 'safety checks'.
              =1:  s*norm(A) + |w|*norm(B) > 1/safe_minimum.
              =2:  ulp*max( s*norm(A), |w|*norm(B) ) < safe_minimum
              =3:  same as INFO=2, but  s  and  w  could not be scaled so
                   as to compute the test.

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Definition at line 125 of file dget53.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.