Add hyperpe caching

bilby/hyper/model.py

@@ -16,13 +16,24 @@ class Model(object):
             List of functions to compute.
         """
         self.models = model_functions
+        self._cached_parameters = {model: None for model in self.models}
+        self._cached_probability = {model: None for model in self.models}
 
         self.parameters = dict()
 
     def prob(self, data, **kwargs):
         probability = 1.0
         for ii, function in enumerate(self.models):
-            probability *= function(data, **self._get_function_parameters(function))
+            function_parameters = self._get_function_parameters(function)
+            if self._cached_parameters[function] == function_parameters:
+                new_probability = self._cached_probability[function]
+            else:
+                new_probability = function(
+                    data, **self._get_function_parameters(function)
+                )
+                self._cached_parameters[function] = function_parameters
+                self._cached_probability[function] = new_probability
+            probability *= new_probability
         return probability
 
     def _get_function_parameters(self, func):