Implement InvGamma and Multinomial in Numba

pytensor/link/numba/dispatch/random.py

@@ -64,7 +64,6 @@ def numba_core_rv_funcify(op: Op, node: Apply) -> Callable:
 @numba_core_rv_funcify.register(ptr.LaplaceRV)
 @numba_core_rv_funcify.register(ptr.BinomialRV)
 @numba_core_rv_funcify.register(ptr.NegBinomialRV)
-@numba_core_rv_funcify.register(ptr.MultinomialRV)
 @numba_core_rv_funcify.register(ptr.PermutationRV)
 @numba_core_rv_funcify.register(ptr.IntegersRV)
 def numba_core_rv_default(op, node):
@@ -132,6 +131,15 @@ def numba_core_ParetoRV(op, node):
     return random
 
 
+@numba_core_rv_funcify.register(ptr.InvGammaRV)
+def numba_core_InvGammaRV(op, node):
+    @numba_basic.numba_njit
+    def random(rng, shape, scale):
+        return 1 / rng.gamma(shape, 1 / scale)
+
+    return random
+
+
 @numba_core_rv_funcify.register(ptr.CategoricalRV)
 def core_CategoricalRV(op, node):
     @numba_basic.numba_njit
@@ -142,6 +150,29 @@ def core_CategoricalRV(op, node):
     return random_fn
 
 
+@numba_core_rv_funcify.register(ptr.MultinomialRV)
+def core_MultinomialRV(op, node):
+    dtype = op.dtype
+
+    @numba_basic.numba_njit
+    def random_fn(rng, n, p):
+        n_cat = p.shape[0]
+        draws = np.zeros(n_cat, dtype=dtype)
+        remaining_p = np.float64(1.0)
+        remaining_n = n
+        for i in range(n_cat - 1):
+            draws[i] = rng.binomial(remaining_n, p[i] / remaining_p)
+            remaining_n -= draws[i]
+            if remaining_n <= 0:
+                break
+            remaining_p -= p[i]
+        if remaining_n > 0:
+            draws[n_cat - 1] = remaining_n
+        return draws
+
+    return random_fn
+
+
 @numba_core_rv_funcify.register(ptr.MvNormalRV)
 def core_MvNormalRV(op, node):
     method = op.method

tests/link/numba/test_random.py

@@ -514,6 +514,31 @@ test_mvnormal_cov_decomposition_method = create_mvnormal_cov_decomposition_metho
             ],
             (pt.as_tensor([2, 1])),
         ),
+        (
+            ptr.invgamma,
+            [
+                (
+                    pt.dvector("shape"),
+                    np.array([1.0, 2.0], dtype=np.float64),
+                ),
+                (
+                    pt.dvector("scale"),
+                    np.array([0.5, 3.0], dtype=np.float64),
+                ),
+            ],
+            (2,),
+        ),
+        (
+            ptr.multinomial,
+            [
+                (
+                    pt.lvector("n"),
+                    np.array([1, 10, 1000], dtype=np.int64),
+                ),
+                (pt.dvector("p"), np.array([0.3, 0.7], dtype=np.float64)),
+            ],
+            None,
+        ),
     ],
     ids=str,
 )