[tune] Add util function to broadcast objects (#1845)

* add util

* Fri Apr  6 15:09:20 PDT 2018

* doc

* Fri Apr  6 15:21:42 PDT 2018

* Fri Apr  6 15:28:07 PDT 2018

* Fri Apr  6 15:28:26 PDT 2018

* Update tune-config.rst

* Update tune-config.rst

python/ray/tune/test/trial_runner_test.py

@@ -13,6 +13,7 @@ from ray.tune import Trainable, TuneError
 from ray.tune import register_env, register_trainable, run_experiments
 from ray.tune.registry import _default_registry, TRAINABLE_CLASS
 from ray.tune.result import DEFAULT_RESULTS_DIR
+from ray.tune.util import pin_in_object_store, get_pinned_object
 from ray.tune.experiment import Experiment
 from ray.tune.trial import Trial, Resources
 from ray.tune.trial_runner import TrialRunner
@@ -28,6 +29,15 @@ class TrainableFunctionApiTest(unittest.TestCase):
         ray.worker.cleanup()
         _register_all()  # re-register the evicted objects
 
+    def testPinObject(self):
+        X = pin_in_object_store("hello")
+
+        @ray.remote
+        def f():
+            return get_pinned_object(X)
+
+        self.assertEqual(ray.get(f.remote()), "hello")
+
     def testRegisterEnv(self):
         register_env("foo", lambda: None)
         self.assertRaises(TypeError, lambda: register_env("foo", 2))

python/ray/tune/util.py

@@ -0,0 +1,33 @@
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+
+import base64
+
+import ray
+from ray.tune.registry import _to_pinnable, _from_pinnable
+
+
+_pinned_objects = []
+PINNED_OBJECT_PREFIX = "ray.tune.PinnedObject:"
+
+
+def pin_in_object_store(obj):
+    obj_id = ray.put(_to_pinnable(obj))
+    _pinned_objects.append(ray.get(obj_id))
+    return "{}{}".format(
+        PINNED_OBJECT_PREFIX, base64.b64encode(obj_id.id()).decode("utf-8"))
+
+
+def get_pinned_object(pinned_id):
+    from ray.local_scheduler import ObjectID
+    return _from_pinnable(ray.get(ObjectID(
+        base64.b64decode(pinned_id[len(PINNED_OBJECT_PREFIX):]))))
+
+
+if __name__ == '__main__':
+    ray.init()
+    X = pin_in_object_store("hello")
+    print(X)
+    result = get_pinned_object(X)
+    print(result)