sgl-project/sglang · error · ValueError

manual_divisions must have {expected} entries, but got {len(

Error message

manual_divisions must have {expected} entries, but got {len(manual_divisions)}

What it means

When manual SM division boundaries are supplied, they must partition the SM range into exactly sm_group_num-1 boundaries (sm_group_num groups). A mismatched list length means the partition count won't equal the requested group count.

Source

Thrown at python/sglang/srt/multiplex/pdmux_context.py:42

def load_pdmux_config(config_path: str) -> PDMuxConfig:
    """Load pdmux configuration from YAML file into a dataclass."""
    if not config_path:
        return PDMuxConfig()

    with open(config_path, "r") as f:
        raw = yaml.safe_load(f)

    if "sm_group_num" not in raw:
        raise ValueError("Missing required field: sm_group_num")

    if raw["sm_group_num"] < 3:
        raise ValueError("sm_group_num must be >= 3")

    manual_divisions = raw.get("manual_divisions", [])

    expected = raw["sm_group_num"] - 2
    if manual_divisions and len(manual_divisions) != expected:
        raise ValueError(
            f"manual_divisions must have {expected} entries, "
            f"but got {len(manual_divisions)}"
        )

    return PDMuxConfig(
        sm_group_num=raw["sm_group_num"],
        manual_divisions=manual_divisions,
        split_forward_token_budget=raw.get("split_forward_token_budget", 65536),
        decode_bs_divisor=raw.get("decode_bs_divisor", 36),
    )


def get_arch_constraints(compute_capability):
    major, minor = compute_capability
    # green context constraints for different architectures
    if major == 6:
        return 1, 1  # min_per_part, multiple
    elif major == 7:

View on GitHub (pinned to 0132848349)

Solutions

1. Make len(manual_divisions) == sm_group_num - 2
2. Or drop manual_divisions entirely to let divide_sm pick partitions automatically
3. Double-check off-by-one: N groups need N-2 manual boundaries in this scheme

Example fix

# before
sm_group_num: 5
manual_divisions: [40, 60]
# after
sm_group_num: 5
manual_divisions: [30, 45, 60]

if manual_divisions:
    assert len(manual_divisions) == raw['sm_group_num'] - 2, 'manual_divisions length mismatch'

When it happens

Trigger: Providing manual_divisions with len != sm_group_num - 2... specifically != sm_group_num - 2 entries per the computed 'expected' value, e.g. 2 entries with sm_group_num=6.

Common situations: Editing the YAML to add/remove a boundary while forgetting to update sm_group_num; copying a manual_divisions list from a config with a different group count.

Related errors

• Missing required field: sm_group_num
• sm_group_num must be >= 3
• No valid partitions found for total SMs {total_sms} with con
• This browser cannot encode H.264 MP4
• H.264 encoder did not return MP4 decoder config

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/5259aaece113a73f. Report an issue: GitHub.