Add test of NNX with orbax.checkpoint

jax_ml_stack/tests/test_nnx_with_optax.py

@@ -51,3 +51,7 @@ def loss(model, x=x, y=y):
     final_loss = loss(model)
 
     self.assertNotAlmostEqual(initial_loss, final_loss)
+
+
+if __name__ == '__main__':
+  unittest.main()

jax_ml_stack/tests/test_nnx_with_orbax.py

@@ -0,0 +1,80 @@
+# Copyright 2024 The JAX Authors.
+#
+# 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.
+
+
+import contextlib
+import platform
+import tempfile
+import unittest
+
+from flax import nnx
+import jax
+import numpy as np
+import orbax.checkpoint
+
+
+class SimpleModel(nnx.Module):
+
+  def __init__(self, rngs):
+    self.layer1 = nnx.Linear(2, 5, rngs=rngs)
+    self.layer2 = nnx.Linear(5, 3, rngs=rngs)
+
+  def __call__(self, x):
+    for layer in [self.layer1, self.layer2]:
+      x = layer(x)
+    return x
+
+
+class NNXOrbaxTest(unittest.TestCase):
+
+  def setUp(self):
+    self.tmp_dir = tempfile.TemporaryDirectory()
+
+    if hasattr(self, 'enterContext'):  # Python 3.11 or newer
+      self.enterContext(self.tmp_dir)
+    else:
+      with contextlib.ExitStack() as stack:
+        stack.enter_context(self.tmp_dir)
+        self.addCleanup(stack.pop_all().close)
+
+  # TODO(jakevdp): https://github.com/google/orbax/pull/1087
+  @unittest.skipIf(
+      platform.system() == 'Windows', 'orbax divide-by-zero error on Windows'
+  )
+  def test_nnx_orbax_checkpoint(self):
+    model = SimpleModel(nnx.Rngs(0))
+
+    # Create the checkpoint
+    state = nnx.state(model)
+    checkpointer = orbax.checkpoint.PyTreeCheckpointer()
+    checkpointer.save(f'{self.tmp_dir.name}/state', item=state)
+    restore_args = orbax.checkpoint.checkpoint_utils.construct_restore_args(
+        state
+    )
+
+    # update the model with the loaded state
+    restored_model = nnx.eval_shape(SimpleModel, nnx.Rngs(1))
+    restored_state = checkpointer.restore(
+        f'{self.tmp_dir.name}/state',
+        item=nnx.state(restored_model),
+        restore_args=restore_args,
+    )
+    nnx.update(restored_model, restored_state)
+
+    self.assertEqual(type(model), type(restored_model))
+    jax.tree.map(np.testing.assert_array_equal, state, restored_state)
+
+
+if __name__ == '__main__':
+  unittest.main()