names in multimin section

Ivo Alxneit-Kamber
Wed Mar 1 11:46:00 GMT 2006

On Tue, 2006-02-28 at 15:39 +0100, Giulio Bottazzi wrote:
> Hi all,
> I think that in a couple of cases the names in the multimin section
> are a little bit inconsistent (or, at least, hard to remember...).
> First: if the function with derivatives is of type
> gsl_multimin_function_fdf
> then one expects the type of the function without derivatives to be
> gsl_multimin_function_f
> rather than gsl_multimin_function.

i tend to agree here (see my previous post on the modified
initialization of nm_simplex), but i think we might get along using ONLY
gsl_multimin_function_fdf i.e. only one type of function. if a minimizer
does not use gradients you could set void * df and void * fdf to a NULL
pointer (or leave it, it is never been used). currently only nm_simplex
falls into the latter category (i do not know of any other algorithm
that does not make use of derivatives, but we should check before we
make any changes here to make sure it will not break in the future).
with this change the interface would be simpler.

in a way we have the same situations for the ODE solvers. only one type
of function that includes the jacobian but some minimizer do not use it
and you can pass a NULL pointer there.
> Second: the present value of the objective function is stored in the
> variable "f" of the structure "gsl_multimin_fdfminimizer" but in the
> variable "fval" of the structure "gsl_multimin_fminimizer".

should be fixed.

> Bye,
> 	Giulio.
Dr. Ivo Alxneit
Laboratory for Solar Technology   phone: +41 56 310 4092
Paul Scherrer Institute             fax: +41 56 310 2688
CH-5232 Villigen         
Switzerland                   gnupg key: 0x515E30C7

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