Files
lerobot/tests/distributed/test_policy_surface.py
T
Haoming Song ef88d4e52b feat(train): parallel training framework — FSDP2, HSDP, gradient accumulation, and DCP checkpoints (#4010)
* feat(train): parallel training engine with FSDP2, HSDP, and DCP checkpoints

Replace the FSDP1 training path with a config-owned parallel-training
engine:

- Topology and runtime configs (--parallelism.*, --accelerator.*):
  dp_replicate x dp_shard degrees select single-process, DDP (unchanged
  default), FSDP2, or HSDP; mixed precision, first-class gradient
  accumulation, and FSDP/DDP tuning knobs are mirrored as plain
  dataclasses that build the accelerate objects at runtime, so every
  run is reproducible from its train_config.json alone. Accelerate env
  vars are guarded against configuring the engine behind the config
  system's back.
- Declarative policy surface: policies declare FSDP2 wrap units
  (_fsdp_wrap_modules) and non-forward entry points
  (_fsdp_forward_methods); a shared engine resolves them around
  accelerator.prepare(). Context-parallel fields are reserved and
  validated to 1.
- Checkpoints: selectable --checkpoint_format (safetensors | dcp |
  safetensors_dcp); the sharded optimizer channel is always DCP;
  two-phase resume (step+RNG before prepare, DCP model/optimizer after)
  reshards across GPU-topology changes; lerobot-convert-dcp merges DCP
  shards into a distributable model.safetensors offline.
- Publishing: PreTrainedPolicy.push_model_to_hub is replaced by the
  free publish_trained_model (model + processors + card + train config,
  all-ranks gather with main-rank writes);
  PreTrainedPolicy._save_pretrained gathers state dicts internally,
  removing the state_dict= threading from save_pretrained.
- lerobot_train is restructured around the engine: optimizer built
  before the single prepare() call, deferred weight load on DCP
  resumes, collective save_checkpoint with no call-site rank branches,
  dp-world-size-based sample accounting.

Breaking changes: FSDP checkpoints from lerobot <= 0.6.x are not
resumable (weights stay loadable via from_pretrained; pin
lerobot==0.6.x to finish old runs); the `accelerate launch
--config_file` yaml flow is superseded by the config flags; training
autocast is owned exclusively by --accelerator.mixed_precision
(policy.dtype only casts parameters).

Also fixes: reward-model hub publishing crash (TypeError on extra
kwargs).

Verified by ~200 new CPU tests (config round-trips, checkpoint
round-trips per format, two-phase resume, publisher contracts,
converter equivalence, accelerate canaries), a 5-test 4-GPU suite
(FSDP2 save/resume bit-exactness, HSDP/DDP loss parity,
changed-topology resume, all-ranks save_pretrained, grad-accum
equivalence), and end-to-end ACT (1/4/8 GPUs) + FastWAM 6B
(FSDP2 + HSDP) training runs.
2026-08-06 19:16:41 +08:00

127 lines
5.0 KiB
Python

#!/usr/bin/env python
# Copyright 2026 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.
"""The declarative policy surface and its distributed-side consumers."""
from types import SimpleNamespace
import pytest
import torch
from torch import nn
from lerobot.configs.accelerator import FSDPConfig
from lerobot.distributed import set_fsdp_wrap_modules, strip_accelerate_cp_hooks
from lerobot.policies.pretrained import PreTrainedPolicy
class TestDeclarativeAttributes:
def test_base_defaults(self):
assert PreTrainedPolicy._fsdp_wrap_modules is None
assert PreTrainedPolicy._fsdp_forward_methods == ("select_action", "predict_action_chunk")
assert PreTrainedPolicy.supports_gradient_checkpointing is False
assert PreTrainedPolicy._cp_plan is None
def test_act_wrap_units_name_real_classes(self):
"""The declared class names must track the modeling code — this test pins the drift."""
from lerobot.policies.act import modeling_act
for name in modeling_act.ACTPolicy._fsdp_wrap_modules:
assert isinstance(getattr(modeling_act, name), type), name
def test_fastwam_wrap_units_name_real_classes(self):
from lerobot.policies.fastwam import modeling_fastwam
from lerobot.policies.fastwam.wan import modular
for name in modeling_fastwam.FastWAMPolicy._fsdp_wrap_modules:
assert isinstance(getattr(modular, name), type), name
class _SelfAttn(nn.Module):
def forward(self, x, attention_mask=None, is_causal=False):
return x, attention_mask, is_causal
class _TinyModel(nn.Module):
def __init__(self):
super().__init__()
self.self_attn = _SelfAttn()
class TestStripAccelerateCpHooks:
def test_strips_the_real_accelerate_hook_and_restores_mask_semantics(self):
"""Attach accelerate's actual mask-stripping hook, strip it, verify masks survive."""
pytest.importorskip("accelerate", reason="accelerate is required (install lerobot[training])")
from accelerate.big_modeling import _attach_context_parallel_hooks
model = _TinyModel()
mask = torch.ones(2, 2)
_attach_context_parallel_hooks(model)
_, hooked_mask, hooked_causal = model.self_attn(torch.zeros(1), attention_mask=mask)
assert hooked_mask is None and hooked_causal is True # the hazard is real
assert strip_accelerate_cp_hooks(model) == 1
_, clean_mask, clean_causal = model.self_attn(torch.zeros(1), attention_mask=mask)
assert clean_mask is mask and clean_causal is False
assert not model.self_attn._forward_pre_hooks
assert not model.self_attn._forward_pre_hooks_with_kwargs
def test_user_hooks_survive(self):
model = _TinyModel()
model.self_attn.register_forward_pre_hook(lambda m, args: None)
assert strip_accelerate_cp_hooks(model) == 0
assert len(model.self_attn._forward_pre_hooks) == 1
class _DeclaredPolicy:
_fsdp_wrap_modules = ["DeclaredBlock"]
class _UndeclaredPolicy:
_fsdp_wrap_modules = None
def _accelerator_with(plugin) -> SimpleNamespace:
return SimpleNamespace(state=SimpleNamespace(fsdp_plugin=plugin))
class TestSetFsdpWrapModules:
@pytest.fixture(autouse=True)
def _requires_accelerate(self):
pytest.importorskip("accelerate", reason="accelerate is required (install lerobot[training])")
def test_policy_declaration_fills_plugin(self):
plugin = FSDPConfig().build_plugin()
set_fsdp_wrap_modules(_accelerator_with(plugin), _DeclaredPolicy())
assert plugin.transformer_cls_names_to_wrap == ["DeclaredBlock"]
def test_user_override_wins(self):
plugin = FSDPConfig(wrap_modules=["UserBlock"]).build_plugin()
set_fsdp_wrap_modules(_accelerator_with(plugin), _DeclaredPolicy())
assert plugin.transformer_cls_names_to_wrap == ["UserBlock"]
def test_no_wrap_source_fails_loudly(self):
plugin = FSDPConfig().build_plugin()
with pytest.raises(ValueError, match="_fsdp_wrap_modules"):
set_fsdp_wrap_modules(_accelerator_with(plugin), _UndeclaredPolicy())
def test_size_based_policy_needs_no_names(self):
plugin = FSDPConfig(min_num_params=1024).build_plugin()
set_fsdp_wrap_modules(_accelerator_with(plugin), _UndeclaredPolicy())
assert plugin.transformer_cls_names_to_wrap is None
def test_non_sharded_run_is_noop(self):
set_fsdp_wrap_modules(_accelerator_with(None), _UndeclaredPolicy())