@@ -170,11 +170,10 @@ class BaseRunner(metaclass=abc.ABCMeta):

         return self.log is not None

     def _ask(self, n):

-        pids = [

-            pid

-            for pid in self._to_retry.keys()

-            if pid not in self._pending_points.values()

-        ][:n]

+        pending_ids = self._pending_points.values()

+        pids_gen = (pid for pid in self._to_retry.keys() if pid not in pending_ids)

+        pids = list(itertools.islice(pids_gen, n))

+

         loss_improvements = len(pids) * [float("inf")]

         if len(pids) < n: