Rename pm.Constant to pm.DiracDelta (pymc-devs#5903)

docs/source/api/distributions/discrete.rst

@@ -12,7 +12,7 @@ Discrete
    DiscreteWeibull
    Poisson
    NegativeBinomial
-   Constant
+   DiracDelta
    ZeroInflatedPoisson
    ZeroInflatedBinomial
    ZeroInflatedNegativeBinomial

pymc/distributions/__init__.py

@@ -63,6 +63,7 @@
     Binomial,
     Categorical,
     Constant,
+    DiracDelta,
     DiscreteUniform,
     DiscreteWeibull,
     Geometric,
@@ -140,6 +141,7 @@
     "Bernoulli",
     "Poisson",
     "NegativeBinomial",
+    "DiracDelta",
     "Constant",
     "ZeroInflatedPoisson",
     "ZeroInflatedNegativeBinomial",

pymc/distributions/discrete.py

@@ -56,6 +56,7 @@
     "DiscreteWeibull",
     "Poisson",
     "NegativeBinomial",
+    "DiracDelta",
     "Constant",
     "ZeroInflatedPoisson",
     "ZeroInflatedBinomial",
@@ -1337,11 +1338,11 @@ def logp(value, p):
         )
 
 
-class ConstantRV(RandomVariable):
-    name = "constant"
+class DiracDeltaRV(RandomVariable):
+    name = "diracdelta"
     ndim_supp = 0
     ndims_params = [0]
-    _print_name = ("Constant", "\\operatorname{Constant}")
+    _print_name = ("DiracDelta", "\\operatorname{DiracDelta}")
 
     def make_node(self, rng, size, dtype, c):
         c = at.as_tensor_variable(c)
@@ -1354,22 +1355,22 @@ def rng_fn(cls, rng, c, size=None):
         return np.full(size, c)
 
 
-constant = ConstantRV()
+diracdelta = DiracDeltaRV()
 
 
-class Constant(Discrete):
+class DiracDelta(Discrete):
     r"""
-    Constant log-likelihood.
+    DiracDelta log-likelihood.
 
     Parameters
     ----------
     c: float or int
-        Constant parameter. The dtype of `c` determines the dtype of the distribution.
-        This can affect which sampler is assigned to Constant variables, or variables
-        that use Constant, such as Mixtures.
+        Dirac Delta parameter. The dtype of `c` determines the dtype of the distribution.
+        This can affect which sampler is assigned to DiracDelta variables, or variables
+        that use DiracDelta, such as Mixtures.
     """
 
-    rv_op = constant
+    rv_op = diracdelta
 
     @classmethod
     def dist(cls, c, *args, **kwargs):
@@ -1385,7 +1386,7 @@ def moment(rv, size, c):
 
     def logp(value, c):
         r"""
-        Calculate log-probability of Constant distribution at specified value.
+        Calculate log-probability of DiracDelta distribution at specified value.
 
         Parameters
         ----------
@@ -1411,6 +1412,23 @@ def logcdf(value, c):
         )
 
 
+class Constant:
+    def __new__(cls, *args, **kwargs):
+        warnings.warn(
+            "pm.Constant has been deprecated. Use pm.DiracDelta instead.",
+            FutureWarning,
+        )
+        return DiracDelta(*args, **kwargs)
+
+    @classmethod
+    def dist(cls, *args, **kwargs):
+        warnings.warn(
+            "pm.Constant has been deprecated. Use pm.DiracDelta instead.",
+            FutureWarning,
+        )
+        return DiracDelta.dist(*args, **kwargs)
+
+
 def _zero_inflated_mixture(*, name, nonzero_p, nonzero_dist, **kwargs):
     """Helper function to create a zero-inflated mixture
 
@@ -1419,7 +1437,7 @@ def _zero_inflated_mixture(*, name, nonzero_p, nonzero_dist, **kwargs):
     nonzero_p = at.as_tensor_variable(floatX(nonzero_p))
     weights = at.stack([1 - nonzero_p, nonzero_p], axis=-1)
     comp_dists = [
-        Constant.dist(0),
+        DiracDelta.dist(0),
         nonzero_dist,
     ]
     if name is not None:

pymc/tests/test_distributions.py

@@ -71,6 +71,7 @@ def polyagamma_cdf(*args, **kwargs):
     Cauchy,
     ChiSquared,
     Constant,
+    DiracDelta,
     Dirichlet,
     DirichletMultinomial,
     DiscreteUniform,
@@ -1729,9 +1730,9 @@ def test_poisson(self):
             {"mu": Rplus},
         )
 
-    def test_constantdist(self):
-        check_logp(Constant, I, {"c": I}, lambda value, c: np.log(c == value))
-        check_logcdf(Constant, I, {"c": I}, lambda value, c: np.log(value >= c))
+    def test_diracdeltadist(self):
+        check_logp(DiracDelta, I, {"c": I}, lambda value, c: np.log(c == value))
+        check_logcdf(DiracDelta, I, {"c": I}, lambda value, c: np.log(value >= c))
 
     def test_zeroinflatedpoisson(self):
         def logp_fn(value, psi, mu):
@@ -3065,7 +3066,7 @@ def test_issue_4499(self):
         assert_almost_equal(m.compile_logp()({"x": np.ones(10)}), -np.log(2) * 10)
 
         with pm.Model(check_bounds=False) as m:
-            x = pm.Constant("x", 1, size=10)
+            x = pm.DiracDelta("x", 1, size=10)
         assert_almost_equal(m.compile_logp()({"x": np.ones(10)}), 0 * 10)
 
 
@@ -3328,3 +3329,10 @@ def test_zero_inflated_dists_dtype_and_broadcast(dist, non_psi_args):
     x = dist([0.5, 0.5, 0.5], *non_psi_args)
     assert x.dtype in discrete_types
     assert x.eval().shape == (3,)
+
+
+def test_constantdist_deprecated():
+    with pytest.warns(FutureWarning, match="DiracDelta"):
+        with Model() as m:
+            x = Constant("x", c=1)
+            assert isinstance(x.owner.op, pm.distributions.discrete.DiracDeltaRV)

pymc/tests/test_distributions_moments.py

@@ -18,8 +18,8 @@
     Categorical,
     Cauchy,
     ChiSquared,
-    Constant,
     DensityDist,
+    DiracDelta,
     Dirichlet,
     DirichletMultinomial,
     DiscreteUniform,
@@ -617,9 +617,9 @@ def test_negative_binomial_moment(n, p, size, expected):
         (np.arange(1, 6), None, np.arange(1, 6)),
     ],
 )
-def test_constant_moment(c, size, expected):
+def test_diracdelta_moment(c, size, expected):
     with Model() as model:
-        Constant("x", c=c, size=size)
+        DiracDelta("x", c=c, size=size)
     assert_moment_is_expected(model, expected)
 
 

pymc/tests/test_distributions_random.py

@@ -1501,17 +1501,17 @@ def discrete_uniform_rng_fn(self, size, lower, upper, rng):
     ]
 
 
-class TestConstant(BaseTestDistributionRandom):
-    def constant_rng_fn(self, size, c):
+class TestDiracDelta(BaseTestDistributionRandom):
+    def diracdelta_rng_fn(self, size, c):
         if size is None:
             return c
         return np.full(size, c)
 
-    pymc_dist = pm.Constant
+    pymc_dist = pm.DiracDelta
     pymc_dist_params = {"c": 3}
     expected_rv_op_params = {"c": 3}
     reference_dist_params = {"c": 3}
-    reference_dist = lambda self: self.constant_rng_fn
+    reference_dist = lambda self: self.diracdelta_rng_fn
     checks_to_run = [
         "check_pymc_params_match_rv_op",
         "check_pymc_draws_match_reference",
@@ -1524,10 +1524,10 @@ def constant_rng_fn(self, size, c):
     )
     def test_dtype(self, floatX):
         with aesara.config.change_flags(floatX=floatX):
-            assert pm.Constant.dist(2**4).dtype == "int8"
-            assert pm.Constant.dist(2**16).dtype == "int32"
-            assert pm.Constant.dist(2**32).dtype == "int64"
-            assert pm.Constant.dist(2.0).dtype == floatX
+            assert pm.DiracDelta.dist(2**4).dtype == "int8"
+            assert pm.DiracDelta.dist(2**16).dtype == "int32"
+            assert pm.DiracDelta.dist(2**32).dtype == "int64"
+            assert pm.DiracDelta.dist(2.0).dtype == floatX
 
 
 class TestOrderedLogistic(BaseTestDistributionRandom):
@@ -1860,8 +1860,8 @@ def ref_rand(size, n, eta):
 
 class TestLKJCholeskyCov(BaseTestDistributionRandom):
     pymc_dist = _LKJCholeskyCov
-    pymc_dist_params = {"eta": 1.0, "n": 3, "sd_dist": pm.Constant.dist([0.5, 1.0, 2.0])}
-    expected_rv_op_params = {"n": 3, "eta": 1.0, "sd_dist": pm.Constant.dist([0.5, 1.0, 2.0])}
+    pymc_dist_params = {"eta": 1.0, "n": 3, "sd_dist": pm.DiracDelta.dist([0.5, 1.0, 2.0])}
+    expected_rv_op_params = {"n": 3, "eta": 1.0, "sd_dist": pm.DiracDelta.dist([0.5, 1.0, 2.0])}
     size = None
 
     sizes_to_check = [None, (), 1, (1,), 5, (4, 5), (2, 4, 2)]
@@ -1891,7 +1891,7 @@ def check_rv_size(self):
     def check_draws_match_expected(self):
         # TODO: Find better comparison:
         rng = aesara.shared(self.get_random_state(reset=True))
-        x = _LKJCholeskyCov.dist(n=2, eta=10_000, sd_dist=pm.Constant.dist([0.5, 2.0]), rng=rng)
+        x = _LKJCholeskyCov.dist(n=2, eta=10_000, sd_dist=pm.DiracDelta.dist([0.5, 2.0]), rng=rng)
         assert np.all(np.abs(x.eval() - np.array([0.5, 0, 2.0])) < 0.01)
 
 

pymc/tests/test_distributions_timeseries.py

@@ -22,7 +22,7 @@
 
 from pymc.aesaraf import floatX
 from pymc.distributions.continuous import Flat, HalfNormal, Normal
-from pymc.distributions.discrete import Constant
+from pymc.distributions.discrete import DiracDelta
 from pymc.distributions.logprob import logp
 from pymc.distributions.multivariate import Dirichlet
 from pymc.distributions.timeseries import (
@@ -100,11 +100,11 @@ class TestGaussianRandomWalkRandom(BaseTestDistributionRandom):
         size = None
 
         pymc_dist = pm.GaussianRandomWalk
-        pymc_dist_params = {"mu": 1.0, "sigma": 2, "init_dist": pm.Constant.dist(0), "steps": 4}
+        pymc_dist_params = {"mu": 1.0, "sigma": 2, "init_dist": pm.DiracDelta.dist(0), "steps": 4}
         expected_rv_op_params = {
             "mu": 1.0,
             "sigma": 2,
-            "init_dist": pm.Constant.dist(0),
+            "init_dist": pm.DiracDelta.dist(0),
             "steps": 4,
         }
 
@@ -455,7 +455,7 @@ def test_multivariate_init_dist(self):
     )
     def test_moment(self, size, expected):
         with Model() as model:
-            init_dist = Constant.dist([[1.0, 2.0], [3.0, 4.0]])
+            init_dist = DiracDelta.dist([[1.0, 2.0], [3.0, 4.0]])
             AR("x", rho=[0, 0], init_dist=init_dist, steps=5, size=size)
         assert_moment_is_expected(model, expected, check_finite_logp=False)
 

pymc/tests/test_sampling.py

@@ -1314,7 +1314,7 @@ def test_issue_4490(self):
     def test_aesara_function_kwargs(self):
         sharedvar = aesara.shared(0)
         with pm.Model() as m:
-            x = pm.Constant("x", 0)
+            x = pm.DiracDelta("x", 0)
             y = pm.Deterministic("y", x + sharedvar)
 
             prior = pm.sample_prior_predictive(
@@ -1361,7 +1361,7 @@ def test_sample_from_xarray_posterior(self, point_list_arg_bug_fixture):
     def test_aesara_function_kwargs(self):
         sharedvar = aesara.shared(0)
         with pm.Model() as m:
-            x = pm.Constant("x", 0.0)
+            x = pm.DiracDelta("x", 0.0)
             y = pm.Deterministic("y", x + sharedvar)
 
             pp = pm.sample_posterior_predictive(
@@ -1434,7 +1434,7 @@ def test_draw_different_samples(self):
 
     def test_draw_aesara_function_kwargs(self):
         sharedvar = aesara.shared(0)
-        x = pm.Constant.dist(0.0)
+        x = pm.DiracDelta.dist(0.0)
         y = x + sharedvar
         draws = pm.draw(
             y,