From d97bce0d64e1c1764e6fc0ca06c64682d57ccf9e Mon Sep 17 00:00:00 2001
From: Robert Nishihara <robertnishihara@gmail.com>
Date: Sun, 26 Jun 2016 13:43:54 -0700
Subject: [PATCH] allow driver to run in PYTHON_MODE, which is equivalent to
 serial Python

---
 lib/python/ray/__init__.py |  1 +
 lib/python/ray/services.py |  3 ++-
 lib/python/ray/worker.py   | 10 ++++++++++
 test/runtest.py            | 21 +++++++++++++++++++++
 test/test_functions.py     | 10 ++++++++++
 5 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/lib/python/ray/__init__.py b/lib/python/ray/__init__.py
index 5a43889bd..3fdecd489 100644
--- a/lib/python/ray/__init__.py
+++ b/lib/python/ray/__init__.py
@@ -4,6 +4,7 @@
 SCRIPT_MODE = 0
 WORKER_MODE = 1
 SHELL_MODE = 2
+PYTHON_MODE = 2
 
 import libraylib as lib
 import serialization
diff --git a/lib/python/ray/services.py b/lib/python/ray/services.py
index 264ed63c2..9b621fc91 100644
--- a/lib/python/ray/services.py
+++ b/lib/python/ray/services.py
@@ -105,7 +105,8 @@ def start_node(scheduler_address, node_ip_address, num_workers, worker_path=None
   time.sleep(0.5)
 
 # driver_mode should equal ray.SCRIPT_MODE if this is being run in a script and
-# ray.SHELL_MODE if it is being used interactively in a shell.
+# ray.SHELL_MODE if it is being used interactively in a shell. It can also equal
+# ray.PYTHON_MODE to run things in a manner equivalent to serial Python code.
 def start_singlenode_cluster(return_drivers=False, num_objstores=1, num_workers_per_objstore=0, worker_path=None, driver_mode=ray.SCRIPT_MODE):
   global drivers
   if num_workers_per_objstore > 0 and worker_path is None:
diff --git a/lib/python/ray/worker.py b/lib/python/ray/worker.py
index db3522d58..4099d712a 100644
--- a/lib/python/ray/worker.py
+++ b/lib/python/ray/worker.py
@@ -7,6 +7,7 @@ import typing
 import funcsigs
 import numpy as np
 import colorama
+import copy
 
 import ray
 from ray.config import LOG_DIRECTORY, LOG_TIMESTAMP
@@ -170,6 +171,8 @@ def disconnect(worker=global_worker):
   ray.lib.disconnect(worker.handle)
 
 def get(objref, worker=global_worker):
+  if worker.mode == ray.PYTHON_MODE:
+    return objref # In ray.PYTHON_MODE, ray.get is the identity operation (the input will actually be a value not an objref)
   ray.lib.request_object(worker.handle, objref)
   if worker.mode == ray.SHELL_MODE or worker.mode == ray.SCRIPT_MODE:
     print_task_info(ray.lib.task_info(worker.handle), worker.mode)
@@ -179,6 +182,8 @@ def get(objref, worker=global_worker):
   return value
 
 def put(value, worker=global_worker):
+  if worker.mode == ray.PYTHON_MODE:
+    return value # In ray.PYTHON_MODE, ray.put is the identity operation
   objref = ray.lib.get_objref(worker.handle)
   worker.put_object(objref, value)
   if worker.mode == ray.SHELL_MODE or worker.mode == ray.SCRIPT_MODE:
@@ -225,6 +230,11 @@ def remote(arg_types, return_types, worker=global_worker):
       """This is what gets run immediately when a worker calls a remote function."""
       args = list(args)
       args.extend([kwargs[keyword] if kwargs.has_key(keyword) else default for keyword, default in func_call.keyword_defaults[len(args):]]) # fill in the remaining arguments
+      if worker.mode == ray.PYTHON_MODE:
+        # In ray.PYTHON_MODE, remote calls simply execute the function. We copy
+        # the arguments to prevent the function call from mutating them and to
+        # match the usual behavior of immutable remote objects.
+        return func(*copy.deepcopy(args))
       check_arguments(func_call, args) # throws an exception if args are invalid
       objrefs = worker.submit_task(func_call.func_name, args)
       if len(objrefs) == 1:
diff --git a/test/runtest.py b/test/runtest.py
index a0994840d..e35d17bfc 100644
--- a/test/runtest.py
+++ b/test/runtest.py
@@ -377,5 +377,26 @@ class ReferenceCountingTest(unittest.TestCase):
 
     services.cleanup()
 
+class PythonModeTest(unittest.TestCase):
+
+  def testObjRefAliasing(self):
+    services.start_singlenode_cluster(driver_mode=ray.PYTHON_MODE)
+
+    xref = test_functions.test_alias_h()
+    self.assertTrue(np.alltrue(xref == np.ones([3, 4, 5]))) # remote functions should return by value
+    self.assertTrue(np.alltrue(xref == ray.get(xref))) # ray.get should be the identity
+    y = np.random.normal(size=[11, 12])
+    self.assertTrue(np.alltrue(y == ray.put(y))) # ray.put should be the identity
+
+    # make sure objects are immutable, this example is why we need to copy
+    # arguments before passing them into remote functions in python mode
+    aref = test_functions.python_mode_f()
+    self.assertTrue(np.alltrue(aref == np.array([0, 0])))
+    bref = test_functions.python_mode_g(aref)
+    self.assertTrue(np.alltrue(aref == np.array([0, 0]))) # python_mode_g should not mutate aref
+    self.assertTrue(np.alltrue(bref == np.array([1, 0])))
+
+    services.cleanup()
+
 if __name__ == "__main__":
     unittest.main()
diff --git a/test/test_functions.py b/test/test_functions.py
index 7e75671af..dfe8a6b2a 100644
--- a/test/test_functions.py
+++ b/test/test_functions.py
@@ -85,3 +85,13 @@ def throw_exception_fct2():
 @ray.remote([float], [int, str, np.ndarray])
 def throw_exception_fct3(x):
   raise Exception("Test function 3 intentionally failed.")
+
+# test Python mode
+@ray.remote([], [np.ndarray])
+def python_mode_f():
+  return np.array([0, 0])
+
+@ray.remote([np.ndarray], [np.ndarray])
+def python_mode_g(x):
+  x[0] = 1
+  return x