Expose CopyToRemoteDevice and MakeCrossHostReceiveBuffer in Python bindings.

PiperOrigin-RevId: 441746248

tests/remote_transfer_test.py

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+# Copyright 2021 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Tests for cross host device transfer."""
+
+from absl.testing import absltest
+import unittest
+import numpy as np
+
+import jax
+from jax._src import test_util as jtu
+
+from jax.config import config
+
+config.parse_flags_with_absl()
+
+
+class RemoteTransferTest(jtu.JaxTestCase):
+
+  def test_remote_transfer(self):
+    if jax.device_count() < 2:
+      raise unittest.SkipTest("Remote transfer requires at lest 2 devices")
+    dev_a, dev_b = jax.local_devices()[:2]
+    if not hasattr(dev_a.client, "make_cross_host_receive_buffers"):
+      # TODO(jheek) remove this once a new version of JAX lib is released
+      raise unittest.SkipTest("jax-lib doesn't include cross host APIs")
+    send_buf = jax.device_put(np.ones((32,)), dev_a)
+    shapes = [send_buf.xla_shape()]
+    (tag, recv_buf), = dev_b.client.make_cross_host_receive_buffers(
+        shapes, dev_b)
+    status, dispatched = send_buf.copy_to_remote_device(tag)
+    self.assertIsNone(status)
+    self.assertTrue(dispatched)
+    self.assertArraysEqual(send_buf, recv_buf)
+
+
+if __name__ == '__main__':
+  absltest.main(testLoader=jtu.JaxTestLoader())