Eliminate the standalone pi052/pi05_backbone.py by distributing its contents:
- Generic dual-expert transformer machinery -> lerobot/policies/pi_gemma.py
(sdpa_attention_forward, compute_layer_complete, PaliGemmaWithExpertModel,
get_gemma_config; the openpi width/depth config is renamed GemmaConfig ->
GemmaVariantConfig to avoid clashing with transformers' GemmaConfig). These
sit next to the existing PiGemma layer code they already depend on.
- pi052-specific model + helpers -> pi052/modeling_pi052.py (PI05Pytorch,
ActionSelectKwargs, make_att_2d_masks, pad_vector, resize_with_pad_torch,
create_sinusoidal_pos_embedding, sample_beta, get_safe_dtype).
DEFAULT_IMAGE_SIZE is duplicated as a plain constant in pi_gemma to avoid a
pi_gemma -> pi05 import cycle. Additive to pi_gemma; pi0/pi05 unaffected.
Verified bit-exact on pepijn223/pi052_robocasa_full (embed/predict/forward
identical) and all 34 pi052 tests pass.
Co-authored-by: Cursor <cursoragent@cursor.com>
The smolvla branch had modified the shared pi0/pi05 modeling + pi05 config to
support pi052 (SDPA attention, layernorm/lm_head handling, optimizer
foreach/fused/lm_head_lr_scale, embedding scaling). Decouple pi052 instead:
- Vendor the PI0.5 backbone (PaliGemmaWithExpertModel, PI05Pytorch, helpers)
into pi052/pi05_backbone.py (verbatim copy, no PI05Policy).
- Flatten PI052Policy to subclass PreTrainedPolicy directly (no longer
PI05Policy); inline the needed PI05Policy methods.
- Restore optimizer_foreach/fused + get_optimizer_preset on PI052Config.
- Revert pi0, pi0_fast, pi05 modeling and configuration_pi05 to origin/main
(byte-identical), so the shared policies carry no smolvla modifications.
Behavior verified bit-exact on pepijn223/pi052_robocasa_full: embed_language_
tokens, predict_action_chunk, and the fused flow+text+FAST training loss are
identical before/after (max_abs_diff=0). pi052 tests pass (pre-existing
stale-name collection errors unchanged).
Co-authored-by: Cursor <cursoragent@cursor.com>
Replaces the per-layer ``modeling_gemma.eager_attention_forward`` call
with ``torch.nn.functional.scaled_dot_product_attention`` in
``compute_layer_complete`` (pi05) and ``_compute_layer_ki`` (pi052).
PyTorch SDPA picks the memory-efficient kernel for the
block-bidirectional 4D additive mask the dual-expert model uses (FA2 /
FA3 reject it because they only accept causal / sliding-window / varlen
patterns). The shared ``sdpa_attention_forward`` helper mirrors the
eager signature so the call sites are unchanged.
Selective AC: removes the redundant outer ``_apply_checkpoint(forward_func, ...)``
wrap in ``PI05Pytorch.forward``. Per-layer checkpointing inside
``PaliGemmaWithExpertModel.forward`` already handles activation
recompute; the outer wrap was double-recomputing the whole backbone.
+14% steps/sec on its own (job 22161405 vs 22161398, 1xH100).
groot: drop ``@strict`` on ``GR00TN15Config`` — newer ``huggingface_hub``
rejects ``@strict`` on non-dataclass ``PretrainedConfig`` subclasses,
which was blocking imports of any sibling policy through
``lerobot.policies.factory``.
New ``examples/benchmark/bench_pi052_step.py`` (+ slurm sweeps v1..v8)
times PI052Policy.forward+backward (optionally with AdamW) on
synthetic inputs. Headline numbers on 1xH100 with KI=True, GC=True,
L=512, 4.14 B trainable params, AdamW state in bf16:
pre-SDPA eager BS=8 610ms 19.5 GiB -> 13.1 samples/s
sdpa BS=8 + compile=default 413ms 19.5 GiB -> 19.3 samples/s
sdpa BS=16 + compile=default 715ms 37.3 GiB -> 22.4 samples/s
sdpa BS=32 + compile=default 1325ms 44.8 GiB -> 24.2 samples/s
sdpa BS=40 + compile=default 1665ms 48.6 GiB -> 24.0 samples/s
Parity tests in ``tests/policies/pi052/test_pi052_sdpa_attention.py``
cover fp32 / bf16 / GQA / MHA forward + backward — output and grads
match the eager path within bf16 tolerance.
Also ships ``examples/benchmark/fsdp_pi052.yaml`` (FSDP2 accelerate
config wrapping GemmaDecoderLayer + SiglipEncoderLayer) for the
follow-up multi-GPU memory sharding work.
Co-authored-by: Cursor <cursoragent@cursor.com>
pepijn223