[tune] Rename 'repeat' to 'num_samples' (#2698)

Deprecates the `repeat` argument and introduces `num_samples`. Also updates docs accordingly.

python/ray/rllib/train.py

@@ -91,7 +91,7 @@ def run(args, parser):
                 "stop": args.stop,
                 "config": dict(args.config, env=args.env),
                 "restore": args.restore,
-                "repeat": args.repeat,
+                "num_samples": args.num_samples,
                 "upload_dir": args.upload_dir,
             }
         }

python/ray/rllib/tuned_examples/hyperband-cartpole.yaml

@@ -1,7 +1,7 @@
 cartpole-ppo:
     env: CartPole-v0
     run: PPO
-    repeat: 3
+    num_samples: 3
     stop:
         episode_reward_mean: 200
         time_total_s: 180

python/ray/rllib/tuned_examples/regression_tests/regression_test.py

@@ -22,7 +22,7 @@ def _evaulate_config(filename):
     with open(os.path.join(CONFIG_DIR, filename)) as f:
         experiments = yaml.load(f)
         for _, config in experiments.items():
-            config["repeat"] = 3
+            config["num_samples"] = 3
     ray.init()
     trials = tune.run_experiments(experiments)
     results = defaultdict(list)