Require at least one Epoch in a Deme

[jeromekelleher]

Currently we're implicitly defining a single epoch via some attributes of the Deme class. From a specification/parser writing perspective, it would be considerably simpler to just required the existence of at least one epoch. So, from the examples:

demes:
  constant_size_deme:
    initial_size: 1000

demes:
  constant_size_deme:
    epochs:
    - initial_size: 1000
      end_time: 0

Is the first that much more readable than the second? Are we the models that people will be writing down to contain many demes with just one epoch?

[grahamgower]

There was some discussion, sorry, I forgot. popsim-consortium/demes-python#133

[grahamgower]

Are we [expecting] the models that people will be writing down to contain many demes with just one epoch?

That will probably be a frequent occurrence, if these two examples are anything to go by.
https://github.com/popsim-consortium/demes-python/blob/main/examples/gutenkunst_ooa.yml
https://github.com/popsim-consortium/demes-python/blob/main/examples/jacobs_papuans.yml

[jeromekelleher]

Thanks @grahamgower, very helpful.

So, I think the earlier discussion was conflating the demes-python implementation and the definition of the specification. There's nothing stopping an implementation keeping start/end time attributes per deme (and I agree this is a useful thing), but it's not necessary from the specification perspective.

The question is, is the slightly more concise yaml description worth the extra complexity? I'm leaning towards "no".

[grahamgower]

The question is, is the slightly more concise yaml description worth the extra complexity? I'm leaning towards "no".

100% agreed! Having to write epochs: and indent another level doesn't make the yaml any harder to write, nor does it make mistakes any more likely.

[jeromekelleher]

@apragsdale, thoughts?

[apragsdale]

I go back and forth on that issue. To me, the extra lines and indentation are noticeable, but I also think there's something to be said for having the YAML description be more explicit: it forces the user to think in terms of epochs which I think will reduce confusion and implementation errors.

I'm more worried about human-readability and reducing implementation errors than the complexity of the code to parse the reduced representation. But I think we can have both by requiring epochs.

[jeromekelleher]

OK, sounds like unanimity so far - @molpopgen, any dissent?

[molpopgen]

No objection. Sorry, I'd missed this notification.

…

On Fri, Dec 4, 2020, 8:11 AM Jerome Kelleher ***@***.***> wrote: OK, sounds like unanimity so far - @molpopgen <https://github.com/molpopgen>, any dissent? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#25 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABQ6OH755WMAL7N6OXQ6HWTSTECT7ANCNFSM4UNE6ETQ> .