🔄 From Aesara: 1362: "Add HalfNormalRV JAX implementation" (#129)

* Add `HalfNormalRV` JAX implementation (#1362)

Co-authored-by: theorashid <theoaorashid@gmail.com>
Co-authored-by: Ricardo Vieira <28983449+ricardoV94@users.noreply.github.com>

Author: 3 people

pytensor/link/jax/dispatch/random.py

@@ -260,6 +260,23 @@ def sample_fn(rng, size, dtype, *parameters):
     return sample_fn
 
 
+@jax_sample_fn.register(aer.HalfNormalRV)
+def jax_sample_fn_halfnormal(op):
+    """JAX implementation of `HalfNormalRV`."""
+
+    def sample_fn(rng, size, dtype, *parameters):
+        rng_key = rng["jax_state"]
+        rng_key, sampling_key = jax.random.split(rng_key, 2)
+        loc, scale = parameters
+        sample = (
+            loc + jax.numpy.abs(jax.random.normal(sampling_key, size, dtype)) * scale
+        )
+        rng["jax_state"] = rng_key
+        return (rng, sample)
+
+    return sample_fn
+
+
 @jax_sample_fn.register(aer.ChoiceRV)
 def jax_funcify_choice(op):
     """JAX implementation of `ChoiceRV`."""

tests/link/jax/test_random.py

@@ -280,6 +280,22 @@ def test_random_updates(rng_ctor):
             "uniform",
             lambda *args: args,
         ),
+        (
+            aer.halfnormal,
+            [
+                set_test_value(
+                    at.dvector(),
+                    np.array([-1.0, 2.0], dtype=np.float64),
+                ),
+                set_test_value(
+                    at.dscalar(),
+                    np.array(1000.0, dtype=np.float64),
+                ),
+            ],
+            (2,),
+            "halfnorm",
+            lambda *args: args,
+        ),
     ],
 )
 def test_random_RandomVariable(rv_op, dist_params, base_size, cdf_name, params_conv):