Adding mxnet components to rl_coach/architectures (#60)

Adding mxnet components to rl_coach architectures.

- Supports PPO and DQN
- Tested with CartPole_PPO and CarPole_DQN
- Normalizing filters don't work right now (see #49) and are disabled in CartPole_PPO preset
- Checkpointing is disabled for MXNet

rl_coach/tests/architectures/mxnet_components/middlewares/test_fc_middleware.py

@@ -0,0 +1,22 @@
+import mxnet as mx
+import os
+import pytest
+import sys
+sys.path.append(os.path.dirname(os.path.dirname(os.path.dirname(__file__))))
+
+
+from rl_coach.base_parameters import MiddlewareScheme
+from rl_coach.architectures.middleware_parameters import FCMiddlewareParameters
+from rl_coach.architectures.mxnet_components.middlewares.fc_middleware import FCMiddleware
+
+
+@pytest.mark.unit_test
+def test_fc_middleware():
+    params = FCMiddlewareParameters(scheme=MiddlewareScheme.Medium)
+    mid = FCMiddleware(params=params)
+    mid.initialize()
+    embedded_data = mx.nd.random.uniform(low=0, high=1, shape=(10, 100))
+    output = mid(embedded_data)
+    assert output.ndim == 2  # since last block was flatten
+    assert output.shape[0] == 10  # since batch_size is 10
+    assert output.shape[1] == 512  # since last layer of middleware (middle scheme) had 512 units

rl_coach/tests/architectures/mxnet_components/middlewares/test_lstm_middleware.py

@@ -0,0 +1,25 @@
+import mxnet as mx
+import os
+import pytest
+import sys
+sys.path.append(os.path.dirname(os.path.dirname(os.path.dirname(__file__))))
+
+
+from rl_coach.base_parameters import MiddlewareScheme
+from rl_coach.architectures.middleware_parameters import LSTMMiddlewareParameters
+from rl_coach.architectures.mxnet_components.middlewares.lstm_middleware import LSTMMiddleware
+
+
+@pytest.mark.unit_test
+def test_lstm_middleware():
+    params = LSTMMiddlewareParameters(number_of_lstm_cells=25, scheme=MiddlewareScheme.Medium)
+    mid = LSTMMiddleware(params=params)
+    mid.initialize()
+    # NTC
+    embedded_data = mx.nd.random.uniform(low=0, high=1, shape=(10, 15, 20))
+    # NTC -> TNC
+    output = mid(embedded_data)
+    assert output.ndim == 3  # since last block was flatten
+    assert output.shape[0] == 15  # since t is 15
+    assert output.shape[1] == 10  # since batch_size is 10
+    assert output.shape[2] == 25  # since number_of_lstm_cells is 25