Add optional name parameter to PyMCStateSpace for multiple models

[opherdonchin]

Summary

As discussed in [#602](#602), this PR adds an optional name parameter to PyMCStateSpace. When provided, it is used to prefix all variables and registered data created by that state-space model. This makes it possible to use multiple state-space models inside one PyMC model without name collisions.

What this changes

• Add name: str | None = None to PyMCStateSpace.__init__.

• Add _prefix_name(self, var_name: str) -> str, which:

  • returns var_name unchanged if self.name is None
  • otherwise returns "{name}_{var_name}".

• Apply _prefix_name when:

  • creating pm.Deterministic variables,
  • registering Kalman filter and likelihood outputs,
  • constructing names in SequenceMvNormal,
  • naming H_jittered, x0_slice, P0_slice, forecast_*, irf, initial_shock,
  • building names for posterior predictive variables.

• Update data helpers (add_data_to_active_model, register_data_with_pymc) so that state-space models can optionally pass prefixed data names.

Backwards compatibility

• If name is not provided, everything behaves exactly as before.
• Existing code that uses a single PyMCStateSpace should work without any changes.

Example

ssm1 = PyMCStateSpace(..., name="vision")
ssm2 = PyMCStateSpace(..., name="motor")

This results in variables such as "vision_obs", "motor_obs", "vision_data", etc., allowing both models to coexist cleanly in the same PyMC model.

Testing

• Added tests/statespace/test_register_variable.py to check the basic naming and variable-registration behavior.
• Attempted to run pytest tests/statespace in a clean pip install -e ".[dev]" environment.
• Test collection currently stops with FutureWarning errors from pytensor.graph.basic.* imports (these have moved to pytensor.graph.traversal.*). This appears unrelated to this PR and originates from existing imports in the codebase and test suite.

[opherdonchin]

Friendly ping for review when someone has a moment — this PR implements the naming support requested in #602. Thanks!

[jessegrabowski]

Thanks for the poke, this one slipped past me. Will review asap.

Looks like pre-commit is failing though, start by clearing that.

[opherdonchin]

I’ve cleared the pre-commit.ci formatting issue (ruff-format is now clean).

The remaining required check (all_tests) is currently awaiting maintainer approval, since this PR comes from a fork. Please let me know when you’d like the workflows to be approved/run.

[opherdonchin]

Read the Docs failure is due to pymc_extras.prior.getattr attempting to resolve mro during Sphinx introspection. I pushed a small guard so dunder attributes raise AttributeError (no distribution lookup). RTD should now build cleanly.

all_tests is still awaiting maintainer approval because this PR is from a fork.

[opherdonchin]

Bumping this.

[jessegrabowski]

I like this idea a lot, but I think the implementation will be a lot cleaner after we merge #607 . I have two issues with this PR as it stands:

1. I'm hesitant about the register_variable method. It adds another bookkeeping dictionary, and I'm not 100% sure what the intended use-case is. I suspect we can accomplish what you want to without it, for example using deterministics, as in:

with pm.Model() as m:
    x_for_model_1 = pm.Normal('x_for_model_1', ...)
    x_for_model_2 = pm.Deterministic('x_for_model_2')

If you really think it's necessary, let's talk about it in another PR.

2. It's a heavy PR -- every single usage of every single named object (matrix, parameter, data, prediction, etc) needs to be wrapped with prefixed_name. What I would prefer is to intervene on the names themselves. I think this will be facilitated by #607. Maybe have a look at that PR and propose a way to work a model name into that framework, then we can revisit this in a few days once it's done?

[jessegrabowski]

Can you give an example of a workflow where you want to use this? I'm hesitant because it breaks the pattern assumed by statespace, in which the statespace model and the pymc model are totally independent.

[jessegrabowski]

revert this, it's unrelated this to PR (cherry pick it if you want to fix the issue)

[jessegrabowski]

Clear away all these comments everywhere in the PR, they don't add helpful context to future devs.

[opherdonchin]

Thanks! I agree waiting for #607 and building on the refactor seems like the cleanest path.

My current thinking is to keep all semantic metadata unscoped (parameters/states/data roles remain “base names”) and apply scoping only at the PyMC/PyTensor graph boundary, where collisions actually occur. Concretely I think that means adding an optional name/namespace to PyMCStateSpace plus a single graph_name(base: str) helper, and then using it in three places:

• Symbolic placeholder creation/registration (e.g., make_and_register_variable / make_and_register_data): accept base names, but create/register placeholders under graph_name(base).
• Hard-coded graph literals (e.g., "data", "x0_slice", "irf"): replace with graph_name("data"), etc.
• PyMC model-namespace interactions (e.g., pm.set_data, membership checks, model[...], named_vars_to_dims): translate base → graph name at the boundary.

I don’t currently see a need for a reverse base_name(...) mapping in the statespace code (we don’t seem to parse arbitrary model vars back into semantics), but can add it later if a concrete use-case emerges.

This should let me drop the extra register_variable bookkeeping from the current PR and re-implement with a much smaller diff after #607. Functionally it’s orthogonal, but #607 should make it easier to keep the change localized and reviewable.

Do you think this could be a good way forward?

Opher