allow float limit to represent data portion

When `limit` is <1, limit represents the percentage of the total number of examples.
If it is >=1,  then it means the number of examples per task (only use this for testing).

lm_eval/evaluator.py

@@ -42,8 +42,8 @@ def simple_evaluate(
         PyTorch device (e.g. "cpu" or "cuda:0") for running models
     :param no_cache: bool
         Whether or not to cache
-    :param limit: int, optional
-        Limit the number of examples per task (only use this for testing)
+    :param limit: int or float, optional
+        Limit the number of examples per task (only use this for testing), If <1, limit is a percentage of the total number of examples.
     :param bootstrap_iters:
         Number of iterations for bootstrap statistics
     :param description_dict: dict[str, str]
@@ -203,6 +203,8 @@ def evaluate(
             if description_dict and task_name in description_dict
             else ""
         )
+        if limit is not None:
+            limit = int(len(task_docs) * limit) if limit < 1.0 else int(limit)
 
         for doc_id, doc in enumerate(itertools.islice(task_docs, 0, limit)):
 

main.py

@@ -35,7 +35,10 @@ def parse_args():
     parser.add_argument("--batch_size", type=str, default=None)
     parser.add_argument("--device", type=str, default=None)
     parser.add_argument("--output_path", default=None)
-    parser.add_argument("--limit", type=int, default=None)
+    parser.add_argument("--limit", type=float, default=None,
+                        help="Limit the number of examples per task. "
+                             "If <1, limit is a percentage of the total number of examples.")
+    parser.add_argument("--data_sampling", type=float, default=None)
     parser.add_argument("--no_cache", action="store_true")
     parser.add_argument("--decontamination_ngrams_path", default=None)
     parser.add_argument("--description_dict_path", default=None)