Boost logo

Ublas :

From: Gunter Winkler (guwi17_at_[hidden])
Date: 2006-03-06 04:27:21

Markus Werle wrote:

>This is a problem with boost-1.33.1.
>I am using axpy_prod in my code and got an error with
>a failed assertion in boost\numeric\ublas\operation.hpp at line 486.
>Could you please explain what kind of error could have raised this error?
>My harmless looking code called ublas functions like this
> ublas::vector<value_type> minus_g(ncols(Jacobian));
> ublas::axpy_prod(-f, J, minus_g, true);
Most probably this error is raised, when the data of minus_g is very
small compared to f and round off errors dominate the result. axpy_prod
uses a different order of operations than prod. Thus an exception can be
raised if the data is bad. If you are sure that your data is correct and
want to disable this test, then you can define

#define BOOST_UBLAS_TYPE_CHECK_MIN (real_type(1))

(replace the 1 by a another value if you want at least some checks.
Usually it is 1.0E-14)

I got this error while computing residuals of linear equations in the
last iteration (where the residual is essentially zero an the numerical
result is only "white noise").