def init(self) -> None:
"""This method carries out the initialization phase of sampling
from the posterior predictive distribution. Notably it initializes the
``_DrawValuesContext`` bookkeeping object and evaluates the "fast drawable"
parts of the model."""
vars: List[Any] = self.vars
trace: _TraceDict = self.trace
samples: int = self.samples
leaf_nodes: Dict[str, Any]
named_nodes_parents: Dict[str, Any]
named_nodes_children: Dict[str, Any]
# initialization phase
context = _DrawValuesContext.get_context()
assert isinstance(context, _DrawValuesContext)
with context:
drawn = context.drawn_vars
evaluated: Dict[int, Any] = {}
symbolic_params = []
for i, var in enumerate(vars):
if is_fast_drawable(var):
evaluated[i] = self.draw_value(var)
continue
name = getattr(var, "name", None)
if (var, samples) in drawn:
evaluated[i] = drawn[(var, samples)]
# We filter out Deterministics by checking for `model` attribute
elif name is not None and hasattr(var, "model") and name in trace.varnames:
# param.name is in the trace. Record it as drawn and evaluated
drawn[(var, samples)] = evaluated[i] = trace[cast(str, name)]
else:
# param still needs to be drawn
symbolic_params.append((i, var))
self.evaluated = evaluated
self.symbolic_params = symbolic_params
def test_mixed_contexts():
modelA = Model()
modelB = Model()
with raises((ValueError, TypeError)):
modelcontext(None)
with modelA:
with modelB:
assert Model.get_context() == modelB
assert modelcontext(None) == modelB
dvc = _DrawValuesContext()
with dvc:
assert Model.get_context() == modelB
assert modelcontext(None) == modelB
assert _DrawValuesContext.get_context() == dvc
dvcb = _DrawValuesContextBlocker()
with dvcb:
assert _DrawValuesContext.get_context() == dvcb
assert _DrawValuesContextBlocker.get_context() == dvcb
assert _DrawValuesContext.get_context() == dvc
assert _DrawValuesContextBlocker.get_context() is dvc
assert Model.get_context() == modelB
assert modelcontext(None) == modelB
assert _DrawValuesContext.get_context(error_if_none=False) is None
with raises(TypeError):
_DrawValuesContext.get_context()
assert Model.get_context() == modelB
assert modelcontext(None) == modelB
assert Model.get_context() == modelA
assert modelcontext(None) == modelA
assert Model.get_context(error_if_none=False) is None
with raises(TypeError):
Model.get_context(error_if_none=True)
with raises((ValueError, TypeError)):
modelcontext(None)