Re: [Help-gsl] overflow exception

[A J]

Thanks, that helps. However, I am not really sure what we can do for
underflows. I am doing this:

check(gsl_sf_exp(b-a))

where check = gsl_isinf, gsl_finite, or gsl_isnan.

The numbers a and b are 564.892 and -158.438, and matlab reports exp(b-a) =
7.2740e-315

Now I get the error:

gsl: exp.c:114: ERROR: underflow
Default GSL error handler invoked.
Aborted

Can anyone help?

Thanks,
A




On 6/18/06, Ralph Silva <address@hidden> wrote:
> Hi,
>
> you can test exp(a) and/or exp(b) using gsl_isnan, gsl_isinf or gsl_finite
> functions. See the GSL manual for more information.
>
> [[]]
> Ralph.
>
> On 6/18/06, A J <address@hidden> wrote:
>
> > Hey All:
>
> While trying to use gsl_sf_exp_e10_e, I get the following error:
>
> gsl: exp.c:127: ERROR: overflow
> Default GSL error handler invoked.
> Aborted
>
>
> In my application, I have two numbers a and b and I have to compute a
> quantity that's exp(a)/(exp(a)+exp(b)). Now if exp(a) overflows and exp(b)
> is in range, I can interpret this as 1. Similarly, if exp(b) overflows and
> exp(a) is in range, I can interpret this as 0.  Similar interpretations
> could be derived for the case in which there's an underflow.
>
> Therefore, it would be nice if I can figure a way in which instead of
> throwing an error, the program outputs an alternative integer which could
> be
> 0 if there's neither underflow or overflow, 1 if there's an overflow and 2
> if there's an underflow (however I am not sure what I can do when both
> overflow or both underflow). Does anyone know how to do this?
>
> Thanks,
> A
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>
> --
> #---------------------------------------------#
> Ralph dos Santos Silva
> address@hidden
> http://dme.ufrj.br/~ralph <http://dme.ufrj.br/%7Eralph>
> Departamento de Métodos Estatísticos - DME
> Instituto de Matemática - IM
> Universidade Federal do Rio de Janeiro - UFRJ
> #---------------------------------------------#