Files
lerobot/tests/datasets/test_sampler.py
T
Pepijn 81f0ca9ce4 test(sampler): drain resumed trillion-frame sampler via iter() to avoid list() prealloc
list(sampler) calls PyObject_LengthHint -> __len__ (the full 10**12 epoch length) and
preallocates that many slots before iterating, OOMing even though the resumed epoch only
yields 3 frames. Collect through the iterator (no length hint) so the test exercises the
real O(1) seek/drain instead of CPython's list growth heuristic.
2026-06-11 10:39:13 +00:00

294 lines
12 KiB
Python

#!/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.
import logging
import pytest
import torch
pytest.importorskip("datasets", reason="datasets is required (install lerobot[dataset])")
from datasets import Dataset # noqa: E402
from lerobot.datasets.io_utils import (
hf_transform_to_torch,
)
from lerobot.datasets.sampler import EpisodeAwareSampler
def calculate_episode_data_index(hf_dataset: Dataset) -> dict[str, torch.Tensor]:
"""Calculate episode data index for testing. Returns {"from": Tensor, "to": Tensor}."""
episode_data_index: dict[str, list[int]] = {"from": [], "to": []}
current_episode = None
if len(hf_dataset) == 0:
return {"from": torch.tensor([]), "to": torch.tensor([])}
for idx, episode_idx in enumerate(hf_dataset["episode_index"]):
if episode_idx != current_episode:
episode_data_index["from"].append(idx)
if current_episode is not None:
episode_data_index["to"].append(idx)
current_episode = episode_idx
episode_data_index["to"].append(idx + 1)
return {k: torch.tensor(v) for k, v in episode_data_index.items()}
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["from"], episode_data_index["to"], 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["from"], episode_data_index["to"], 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["from"], episode_data_index["to"], 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["from"], episode_data_index["to"], 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["from"], episode_data_index["to"], shuffle=True)
assert sampler.indices == [0, 1, 2, 3, 4, 5]
assert len(sampler) == 6
assert set(sampler) == {0, 1, 2, 3, 4, 5}
def test_shuffle_with_generator_is_deterministic():
# Two samplers shuffling with same-seed generators must yield identical permutations.
# This is what keeps batch shards disjoint across ranks in distributed training, where
# accelerate synchronizes the sampler's generator state instead of the global torch RNG.
sampler_a = EpisodeAwareSampler(
[0], [6], shuffle=True, deterministic=False, generator=torch.Generator().manual_seed(42)
)
sampler_b = EpisodeAwareSampler(
[0], [6], shuffle=True, deterministic=False, generator=torch.Generator().manual_seed(42)
)
assert list(sampler_a) == list(sampler_b)
# Desyncing the global RNG must not affect the permutation.
sampler_c = EpisodeAwareSampler(
[0], [6], shuffle=True, deterministic=False, generator=torch.Generator().manual_seed(42)
)
order_before = list(sampler_c)
sampler_c.generator.manual_seed(42)
torch.randperm(1000) # consume global RNG, as rank-asymmetric code (e.g. eval) would
assert list(sampler_c) == order_before
def test_generator_attribute_defaults_to_none():
# accelerate detects synchronizable samplers via `hasattr(sampler, "generator")`,
# so the attribute must exist even when no generator is passed.
sampler = EpisodeAwareSampler([0], [6], shuffle=True, deterministic=False)
assert sampler.generator is None
assert set(sampler) == {0, 1, 2, 3, 4, 5}
def test_negative_drop_first_frames_raises():
with pytest.raises(ValueError, match="drop_n_first_frames must be >= 0"):
EpisodeAwareSampler([0], [10], drop_n_first_frames=-1)
def test_negative_drop_last_frames_raises():
with pytest.raises(ValueError, match="drop_n_last_frames must be >= 0"):
EpisodeAwareSampler([0], [10], drop_n_last_frames=-1)
def test_all_episodes_dropped_raises():
# All episodes have 1 frame, drop_n_first_frames=1 removes all
with pytest.raises(ValueError, match="No valid frames remain"):
EpisodeAwareSampler([0, 1, 2], [1, 2, 3], drop_n_first_frames=1)
def test_partial_episode_drop_warns(caplog):
# Episode 0: 1 frame (dropped), Episode 1: 5 frames (kept)
with caplog.at_level(logging.WARNING, logger="lerobot.datasets.sampler"):
sampler = EpisodeAwareSampler([0, 1], [1, 6], drop_n_first_frames=1)
# Episode 0 is skipped (1 frame, drop 1), Episode 1 keeps frames 2-5
assert sampler.indices == [2, 3, 4, 5]
assert "Episode 0" in caplog.text
# --- deterministic mode (seeded Feistel permutation) ---
from functools import partial # noqa: E402
from lerobot.datasets.sampler import compute_sampler_state # noqa: E402
deterministic_sampler = partial(EpisodeAwareSampler, deterministic=True)
EPISODE_BOUNDS = ([0, 2, 3], [2, 3, 6]) # episodes of 2, 1 and 3 frames
def test_deterministic_mode_unshuffled_matches_default_mode():
for kwargs in (
{},
{"drop_n_first_frames": 1},
{"drop_n_last_frames": 1},
{"episode_indices_to_use": [0, 2]},
):
reference = EpisodeAwareSampler(*EPISODE_BOUNDS, shuffle=False, **kwargs)
sampler = deterministic_sampler(*EPISODE_BOUNDS, shuffle=False, **kwargs)
assert list(sampler) == list(reference), kwargs
assert len(sampler) == len(reference), kwargs
def test_deterministic_mode_rejects_generator():
with pytest.raises(ValueError, match="generator is unused in deterministic mode"):
deterministic_sampler(*EPISODE_BOUNDS, shuffle=True, generator=torch.Generator())
def test_state_methods_require_deterministic_mode():
sampler = EpisodeAwareSampler(*EPISODE_BOUNDS, shuffle=True, deterministic=False)
with pytest.raises(RuntimeError, match="deterministic=True"):
sampler.set_epoch(1)
with pytest.raises(RuntimeError, match="deterministic=True"):
sampler.state_dict()
@pytest.mark.parametrize("num_frames", [1, 2, 3, 37, 64, 100])
def test_deterministic_sampler_shuffle_is_permutation(num_frames):
for seed in (0, 1, 1234):
sampler = deterministic_sampler([0], [num_frames], shuffle=True, seed=seed)
assert sorted(sampler) == list(range(num_frames))
def test_deterministic_sampler_epochs_reproduce_and_differ():
sampler_a = deterministic_sampler([0], [100], shuffle=True, seed=42)
sampler_b = deterministic_sampler([0], [100], shuffle=True, seed=42)
epoch_0 = list(sampler_a)
assert list(sampler_b) == epoch_0 # same (seed, epoch) -> same order on any process
epoch_1 = list(sampler_a) # __iter__ auto-advances the epoch
assert epoch_1 != epoch_0
assert sorted(epoch_1) == sorted(epoch_0)
sampler_a.set_epoch(0)
assert list(sampler_a) == epoch_0
assert list(deterministic_sampler([0], [100], shuffle=True, seed=7)) != epoch_0
def test_deterministic_sampler_resume_mid_epoch():
reference = deterministic_sampler(*EPISODE_BOUNDS, shuffle=True, seed=42)
epoch_0 = list(reference)
epoch_1 = list(reference)
for start in (0, 1, 4, len(epoch_0)):
resumed = deterministic_sampler(*EPISODE_BOUNDS, shuffle=True, seed=42)
resumed.load_state_dict({"epoch": 0, "start_index": start})
assert list(resumed) == epoch_0[start:]
# the resumed sampler continues into the same epoch 1 as the uninterrupted one
assert list(resumed) == epoch_1
def test_deterministic_sampler_constant_memory():
# A trillion-frame dataset must instantiate instantly and seek anywhere in O(1):
# only per-episode boundaries are stored, never per-frame indices.
num_frames = 10**12
sampler = deterministic_sampler([0], [num_frames], shuffle=True, seed=0)
assert len(sampler) == num_frames
sampler.load_state_dict({"epoch": 3, "start_index": num_frames - 3})
# Collect via the iterator: list(sampler) would call PyObject_LengthHint -> sampler.__len__
# (the full epoch length, here 10**12) and pre-allocate that many slots before iterating. The
# iterator itself exposes no length hint, so this stays O(1) like the resumed epoch it drains.
tail = list(iter(sampler))
assert len(tail) == 3
assert all(0 <= idx < num_frames for idx in tail)
def test_deterministic_sampler_validation_matches_episode_aware():
with pytest.raises(ValueError, match="drop_n_first_frames must be >= 0"):
deterministic_sampler([0], [10], drop_n_first_frames=-1)
with pytest.raises(ValueError, match="drop_n_last_frames must be >= 0"):
deterministic_sampler([0], [10], drop_n_last_frames=-1)
with pytest.raises(ValueError, match="No valid frames remain"):
deterministic_sampler([0, 1, 2], [1, 2, 3], drop_n_first_frames=1)
def test_deterministic_sampler_partial_episode_drop_warns(caplog):
with caplog.at_level(logging.WARNING, logger="lerobot.datasets.sampler"):
sampler = deterministic_sampler([0, 1], [1, 6], drop_n_first_frames=1, shuffle=False)
assert list(sampler) == [2, 3, 4, 5]
assert "Episode 0" in caplog.text
def test_compute_sampler_state():
# 100 frames, batch 10, 2 ranks -> 10 underlying batches, 5 per rank per epoch.
assert compute_sampler_state(step=0, num_frames=100, batch_size=10, num_processes=2) == {
"epoch": 0,
"start_index": 0,
}
# step 7 -> epoch 1, 2 per-rank batches in = 2 * 10 * 2 = 40 samples in
assert compute_sampler_state(step=7, num_frames=100, batch_size=10, num_processes=2) == {
"epoch": 1,
"start_index": 40,
}
# uneven epoch: 95 frames -> 10 underlying batches (last short), still 5 per rank
assert compute_sampler_state(step=12, num_frames=95, batch_size=10, num_processes=2) == {
"epoch": 2,
"start_index": 40,
}
# uneven sharding: 105 frames -> 11 underlying batches, 6 per rank (even_batches pads)
assert compute_sampler_state(step=11, num_frames=105, batch_size=10, num_processes=2) == {
"epoch": 1,
"start_index": 100,
}