Pyro enum bugfix [WIP] (#2226)

pyro/infer/traceenum_elbo.py

@@ -98,7 +98,7 @@ def _compute_model_factors(model_trace, guide_trace):
         if site["type"] == "sample":
             if name in guide_trace.nodes:
                 cost_sites.setdefault(ordering[name], []).append(site)
-                non_enum_dims.update(site["packed"]["log_prob"]._pyro_dims)
+                non_enum_dims.update(guide_trace.nodes[name]["packed"]["log_prob"]._pyro_dims)
             elif site["infer"].get("_enumerate_dim") is None:
                 cost_sites.setdefault(ordering[name], []).append(site)
             else:

tests/infer/test_enum.py

@@ -13,6 +13,7 @@
 import pyro.distributions as dist
 import pyro.optim
 import pyro.poutine as poutine
+from pyro import infer
 from pyro.distributions.testing.rejection_gamma import ShapeAugmentedGamma
 from pyro.infer import SVI, config_enumerate
 from pyro.infer.enum import iter_discrete_traces
@@ -3248,3 +3249,38 @@ def guide():
     elbo = Trace_ELBO(vectorize_particles=True, num_particles=num_samples).loss(model, guide)
 
     assert_equal(vectorized_weights.sum().item() / num_samples, -elbo, prec=0.02)
+
+
+def test_multi_dependence_enumeration():
+    """
+    This test checks whether enumeration works correctly in the case where multiple downstream
+    variables are coupled to the same random discrete variable.
+    This is based on [issue 2223](https://github.com/pyro-ppl/pyro/issues/2223), and should
+    pass when it has been resolved
+    """
+    K = 5
+    d = 2
+    N_obs = 3
+
+    @config_enumerate
+    def model(N=1):
+        with pyro.plate('data_plate', N, dim=-2):
+            mixing_weights = pyro.param('pi', torch.ones(K) / K, constraint=constraints.simplex)
+            means = pyro.sample('mu', dist.Normal(torch.zeros(K, d), torch.ones(K, d)).to_event(2))
+
+            with pyro.plate('observations', N_obs, dim=-1):
+                s = pyro.sample('s', dist.Categorical(mixing_weights))
+
+                pyro.sample('x', dist.Normal(Vindex(means)[..., s, :], 0.1).to_event(1))
+                pyro.sample('y', dist.Normal(Vindex(means)[..., s, :], 0.1).to_event(1))
+
+    x = poutine.trace(model).get_trace(N=2).nodes['x']['value']
+
+    pyro.clear_param_store()
+    conditioned_model = pyro.condition(model, data={'x': x})
+    guide = infer.autoguide.AutoDelta(poutine.block(conditioned_model, hide=['s']))
+
+    elbo = infer.TraceEnum_ELBO(max_plate_nesting=2)
+
+    elbo.loss_and_grads(conditioned_model, guide, x.size(0))
+    assert pyro.get_param_store()._params['pi'].grad is not None