Generalising class names

[daffidwilde]

When defining classes of individuals in the system, their names must be of the form "Class <i>" where i is an integer. For example:

>>> import ciw
>>> N = ciw.create_network(
...     arrival_distributions={
...         "child": [ciw.dists.Exponential(0.2)],
...         "adult": [ciw.dists.Exponential(0.3)],
...     },
...     service_distributions={
...         "child": [ciw.dists.Exponential(0.3)],
...         "adult": [ciw.dists.Exponential(0.3)],
...     },
...     number_of_servers=[5],
... )

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-93-0eddbdb2b06e> in <module>
      8         "adult": [ciw.dists.Exponential(0.3)],
      9     },
---> 10     number_of_servers=[5],
     11 )

~/anaconda3/lib/python3.7/site-packages/ciw/import_params.py in create_network(arrival_distributions, baulking_functions, class_change_matrices, number_of_servers, priority_classes, queue_capacities, service_distributions, routing, batching_distributions)
     68         params['batching_distributions'] = batching_distributions
     69 
---> 70     return create_network_from_dictionary(params)
     71 
     72 

~/anaconda3/lib/python3.7/site-packages/ciw/import_params.py in create_network_from_dictionary(params_input)
    109     """
    110     params = fill_out_dictionary(params_input)
--> 111     validify_dictionary(params)
    112     # Then make the Network object
    113     arrivals = [params['arrival_distributions']['Class ' + str(clss)]

~/anaconda3/lib/python3.7/site-packages/ciw/import_params.py in validify_dictionary(params)
    266             set(['Class ' + str(i) for i in range(params['number_of_classes'])]))
    267     if not consistant_class_names:
--> 268         raise ValueError('Ensure correct names for customer classes.')
    269     if all(isinstance(f, types.FunctionType) for f in params['routing']):
    270         num_nodes_count = [

ValueError: Ensure correct names for customer classes.

Is this a necessary condition for ciw to function as it stands? If not, I don't see why the class names can't be recorded when the network is created and then placed when a record is created.

It isn't a major problem except when you have a number of external classes that you'd like to extract from ciw.

[geraintpalmer]

Hi @daffidwilde yes currently Ciw needs classes to be called 'Class 0', 'Class 1' etc. in order to force an ordering (unfortunatelt I think ciw's insides rely on this currently). I agree it would be much nicer to define own names, and would be more than happy for this to be changed.

[drvinceknight]

Remind me @geraintpalmer, is there a purpose to class names?

What about not having names at all and instead of dictionaries you'd just have lists? (Essentially the names just become the indices of the list)

[geraintpalmer]

I think lists of lists were the original idea, but became difficult to read. Compare the current (from the tutorial:

>>> import ciw
>>> N = ciw.create_network(
...     arrival_distributions={'Class 0': [ciw.dists.Exponential(1.0),
...                                        ciw.dists.NoArrivals(),
...                                        ciw.dists.NoArrivals()],
...                            'Class 1': [ciw.dists.Exponential(2.0),
...                                        ciw.dists.NoArrivals(),
...                                        ciw.dists.NoArrivals()]},
...     service_distributions={'Class 0': [ciw.dists.Exponential(4.0),
...                                        ciw.dists.Exponential(1.0),
...                                        ciw.dists.Deterministic(0.0)],
...                            'Class 1': [ciw.dists.Exponential(6.0),
...                                        ciw.dists.Deterministic(0.0),
...                                        ciw.dists.Exponential(1.0)]},
...     routing={'Class 0': [[0.0, 1.0, 0.0],
...                          [0.0, 0.0, 0.0],
...                          [0.0, 0.0, 0.0]],
...              'Class 1': [[0.0, 0.0, 1.0],
...                          [0.0, 0.0, 0.0],
...                          [0.0, 0.0, 0.0]]},
...     number_of_servers=[1, 2, 3],
... )

To the possibility of lists of lists (there may be a better way to present this, but I think it does reduce readability):

>>> import ciw
>>> N = ciw.create_network(
...     arrival_distributions=[[ciw.dists.Exponential(1.0),
...                             ciw.dists.NoArrivals(),
...                             ciw.dists.NoArrivals()],
...                            [ciw.dists.Exponential(2.0),
...                             ciw.dists.NoArrivals(),
...                             ciw.dists.NoArrivals()]],
...     service_distributions=[[ciw.dists.Exponential(4.0),
...                             ciw.dists.Exponential(1.0),
...                             ciw.dists.Deterministic(0.0)],
...                            [ciw.dists.Exponential(6.0),
...                             ciw.dists.Deterministic(0.0),
...                             ciw.dists.Exponential(1.0)]],
...     routing=[[[0.0, 1.0, 0.0],
...               [0.0, 0.0, 0.0],
...               [0.0, 0.0, 0.0]],
...              [[0.0, 0.0, 1.0],
...               [0.0, 0.0, 0.0],
...               [0.0, 0.0, 0.0]]],
...     number_of_servers=[1, 2, 3],
... )

It also makes setting priority classes more readable:

priority_classes={'Class 0': 0,
                  'Class 1': 1,
                  'Class 2': 1}

I think the idea of strings to represent customer classes. I like @daffidwilde's idea of allowing any string to represent a customer class, I think thta would make things much more reabable and meaningful to the user.

What do you both think @daffidwilde? @drvinceknight?

[daffidwilde]

What about not having names at all and instead of dictionaries you'd just have lists? (Essentially the names just become the indices of the list)

I prefer — from a usability perspective — to have a dictionary rather than nested lists.

Internally, if the names are just being treated like indices then I imagine the dictionary could be iterated over in another way so ciw is completely class name invariant.

[daffidwilde]

Sorry @geraintpalmer, it appears we replied at the same time. I concur with everything you’ve said.

[geraintpalmer]

Internally, if the names are just being treated like indices then I imagine the dictionary could be iterated over in another way so ciw is completely class name invariant.

Yes I like this. Shouldn't be too many changes - and would still be back compatible 👍

[drvinceknight]

I'm not sure I see the improved readability using dictionaries but:

would still be back compatible

👍

(FYI, depending on how it's implemented given that internally lists are in fact just dictionaries it could be possible to do this in such a way where you could pass lists without it actually needing special consideration.)

[daffidwilde]

it could be possible to do this in such a way where you could pass lists without it actually needing special consideration.

That would be jolly nice to have both. I suspect that my suggestion would be implemented in a very similar way.