add EpisodeAwareSampler (#217)

Co-authored-by: Alexander Soare <alexander.soare159@gmail.com>

tests/test_sampler.py

@@ -0,0 +1,90 @@
+#!/usr/bin/env python
+
+# Copyright 2024 The HuggingFace Inc. team. All rights reserved.
+#
+# 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
+#
+#     http://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.
+from datasets import Dataset
+
+from lerobot.common.datasets.sampler import EpisodeAwareSampler
+from lerobot.common.datasets.utils import (
+    calculate_episode_data_index,
+    hf_transform_to_torch,
+)
+
+
+def test_drop_n_first_frames():
+    dataset = Dataset.from_dict(
+        {
+            "timestamp": [0.1, 0.2, 0.3, 0.4, 0.5, 0.6],
+            "index": [0, 1, 2, 3, 4, 5],
+            "episode_index": [0, 0, 1, 2, 2, 2],
+        },
+    )
+    dataset.set_transform(hf_transform_to_torch)
+    episode_data_index = calculate_episode_data_index(dataset)
+    sampler = EpisodeAwareSampler(episode_data_index, drop_n_first_frames=1)
+    assert sampler.indices == [1, 4, 5]
+    assert len(sampler) == 3
+    assert list(sampler) == [1, 4, 5]
+
+
+def test_drop_n_last_frames():
+    dataset = Dataset.from_dict(
+        {
+            "timestamp": [0.1, 0.2, 0.3, 0.4, 0.5, 0.6],
+            "index": [0, 1, 2, 3, 4, 5],
+            "episode_index": [0, 0, 1, 2, 2, 2],
+        },
+    )
+    dataset.set_transform(hf_transform_to_torch)
+    episode_data_index = calculate_episode_data_index(dataset)
+    sampler = EpisodeAwareSampler(episode_data_index, drop_n_last_frames=1)
+    assert sampler.indices == [0, 3, 4]
+    assert len(sampler) == 3
+    assert list(sampler) == [0, 3, 4]
+
+
+def test_episode_indices_to_use():
+    dataset = Dataset.from_dict(
+        {
+            "timestamp": [0.1, 0.2, 0.3, 0.4, 0.5, 0.6],
+            "index": [0, 1, 2, 3, 4, 5],
+            "episode_index": [0, 0, 1, 2, 2, 2],
+        },
+    )
+    dataset.set_transform(hf_transform_to_torch)
+    episode_data_index = calculate_episode_data_index(dataset)
+    sampler = EpisodeAwareSampler(episode_data_index, episode_indices_to_use=[0, 2])
+    assert sampler.indices == [0, 1, 3, 4, 5]
+    assert len(sampler) == 5
+    assert list(sampler) == [0, 1, 3, 4, 5]
+
+
+def test_shuffle():
+    dataset = Dataset.from_dict(
+        {
+            "timestamp": [0.1, 0.2, 0.3, 0.4, 0.5, 0.6],
+            "index": [0, 1, 2, 3, 4, 5],
+            "episode_index": [0, 0, 1, 2, 2, 2],
+        },
+    )
+    dataset.set_transform(hf_transform_to_torch)
+    episode_data_index = calculate_episode_data_index(dataset)
+    sampler = EpisodeAwareSampler(episode_data_index, shuffle=False)
+    assert sampler.indices == [0, 1, 2, 3, 4, 5]
+    assert len(sampler) == 6
+    assert list(sampler) == [0, 1, 2, 3, 4, 5]
+    sampler = EpisodeAwareSampler(episode_data_index, shuffle=True)
+    assert sampler.indices == [0, 1, 2, 3, 4, 5]
+    assert len(sampler) == 6
+    assert set(sampler) == {0, 1, 2, 3, 4, 5}