Reparameterize GammaRV so beta is not inverted at each call

Author: tvwenger

pytensor/tensor/random/basic.py

@@ -443,7 +443,7 @@ class GammaRV(ScipyRandomVariable):
     dtype = "floatX"
     _print_name = ("Gamma", "\\operatorname{Gamma}")
 
-    def __call__(self, shape, rate, size=None, **kwargs):
+    def __call__(self, alpha, beta, size=None, **kwargs):
         r"""Draw samples from a gamma distribution.
 
         Signature
@@ -464,11 +464,11 @@ def __call__(self, shape, rate, size=None, **kwargs):
             is returned.
 
         """
-        return super().__call__(shape, 1.0 / rate, size=size, **kwargs)
+        return super().__call__(alpha, beta, size=size, **kwargs)
 
     @classmethod
-    def rng_fn_scipy(cls, rng, shape, scale, size):
-        return stats.gamma.rvs(shape, scale=scale, size=size, random_state=rng)
+    def rng_fn_scipy(cls, rng, alpha, beta, size):
+        return stats.gamma.rvs(alpha, scale=1.0 / beta, size=size, random_state=rng)
 
 
 gamma = GammaRV()