Speed up to DIC and BPIC (#2488)

Author: denadai2

pymc3/stats.py

@@ -116,12 +116,13 @@ def dic(trace, model=None):
     `float` representing the deviance information criterion of the model and trace
     """
     model = modelcontext(model)
+    logp = model.logp
 
-    mean_deviance = -2 * np.mean([model.logp(pt) for pt in trace])
+    mean_deviance = -2 * np.mean([logp(pt) for pt in trace])
 
     free_rv_means = {rv.name: trace[rv.name].mean(
         axis=0) for rv in model.free_RVs}
-    deviance_at_mean = -2 * model.logp(free_rv_means)
+    deviance_at_mean = -2 * logp(free_rv_means)
 
     return 2 * mean_deviance - deviance_at_mean
 
@@ -328,12 +329,13 @@ def bpic(trace, model=None):
         Optional model. Default None, taken from context.
     """
     model = modelcontext(model)
+    logp = model.logp
 
-    mean_deviance = -2 * np.mean([model.logp(pt) for pt in trace])
+    mean_deviance = -2 * np.mean([logp(pt) for pt in trace])
 
     free_rv_means = {rv.name: trace[rv.name].mean(
         axis=0) for rv in model.free_RVs}
-    deviance_at_mean = -2 * model.logp(free_rv_means)
+    deviance_at_mean = -2 * logp(free_rv_means)
 
     return 3 * mean_deviance - 2 * deviance_at_mean