Re: [h5md-user] Make "time" optional?

[Felix Höfling]

> Am 11.07.2014 16:09 schrieb "Konrad Hinsen"  
> <address@hidden>:
>
> > Hi everyone,
> >
> > Now that I have started to use H5MD seriously, I also start to notice
> > problems with it. One of them is the obligatory presence of a "time"
> > dataset. I want to store a Monte-Carlo trajectory which consists of a
> > sequence of configurations, but without any associated time values.
> > If I want to respect the H5MD specification, I have to make up
> > numbers, which is not a good habit to take.
> >
> > Is there any reason why "time" was made obligatory?
> >
> > Konrad.

Am 11.07.2014, 17:51 Uhr, schrieb Olaf Lenz <address@hidden>:

> ...and adding to that, can we also make the "step" optional? Weird as  
> this
> may sound, we would also have to invent step numbers.
>
> Olaf

Dear Konrad and Olaf,

We have had some discussion on the time dataset in the context of Monte
Carlo simulations. If I remember well the outcome was that in the case of
no physical time, time is simply identical (=linked) to step. Our
intentation was to have no optional parts in the core H5MD element---for
the sake of making reading simple.

Whether such a decision was wise or not, I don't know. But it has been
fixed now for H5MD 1.x. Making step or time optional would break
compatibility with 1.0 and would make 1.0 basically obsolete. Thus I don't
think it is a good idea. Nevertheless, I am open to extend the
interpretation of step/time (but the fields must be present). For example,
step could also just numerate the snapshots stored, without reference to
any simulation order.

Note that for a single snapshot only, the data are stored in a simple HDF5
dataset without step/time.

Best regards,

Felix