Re: More help with odeset()

[Nicholas Jankowski]

On Oct 19, 2016 8:23 AM, "c." <address@hidden> wrote:
>
> Hi,
>
> On 18 Oct 2016, at 21:16, Rik <address@hidden> wrote:
>
> > Could someone run the following test under Matlab?
> >
> > x = odeset ('MassConstant', true)
> >
> > According to the documentation in Octave,
> >
> > ## @item MassConstant
> > ## Specify whether the mass matrix is a constant matrix or depends on
> > ## the state.
> >
> > but this option doesn't appear in the Matlab documentation for odeset.
>
> > It's probably unnecessary because when the Mass property is a matrix, it is
> > constant, if Mass is a function handle, it has the possibility of depending
> > on state.
>
> Indeed, but I think the idea behind the MassConstant is that the Mass matrix
> can depend on time but not on state or be completely constant and even a constant
> matrix could be passed as a function that builds the matrix.
>
> This option is not available in Matlab now but was present in previous versions
> as can be seen from old sites discussing the matlab odesuite, e.g.:
>
> http://cens.ioc.ee/local/man/matlab/techdoc/ref/odeset.html
>
> It is hard to determine in what version it was removed.
>
> We decided to keep other functionalities of odepkg for backward compatibility
> with cruft matlab code, we may decide to keep this one as well, I do not have any
> strong feeling about this.
>
> > If it isn't necessary it can be deleted and the FIXME in the code for
> > odeset closed.  I tried 'grep -r MassConstant' in scripts/ode and the
> > property isn't used in any calculating solver.
>
>
> I can't seem to find any use of this in odepkg either.
>
> > --Rik
>
>
> c.
>
>

So we left it in to be compatible with old matlab code, but it doesn't actually get used. If it doesn't present any warning to a user who might expect it to have an effect, seems like it would be best to remove it. Don't know how it would ever get functional unless someone has an older version of MATLAB to use for compatibility checking.

Nickj