Use double for cpnest parameter

bilby/core/sampler/cpnest.py

@@ -89,8 +89,8 @@ class Cpnest(NestedSampler):
                 prior_samples = self.priors.sample()
                 self._update_bounds()
                 point = LivePoint(
-                    self.names, array.array(
-                        'f', [prior_samples[name] for name in self.names]))
+                    self.names, array.array('d', [prior_samples[name] for name in self.names])
+                )
                 return point
 
         self._resolve_proposal_functions()