DeepInfer/scripts/ref_next_token.py
loopyt 1e04aea7ea feat: add SM90 (Hopper) support for DeepSeek-V4.1 inference
DeepInfer targets Blackwell: the vendored FlashMLA fork only ships SM100 kernels
(`CUDA_ARCHS = ["sm_100a", "sm_103a"]`, every entry point asserts `arch.is_sm100f()`),
and several DeepGEMM attention APIs plus the whole quantization recipe assume
FP4 tensor cores, packed UE8M0 scales and per-32 blocks. None of that exists on
Hopper, so this branch adds an SM90 backend and gets an 8x H20 node to produce
tokens end to end.

Scope and status: the pipeline runs (prefill, decode, sampling) and matches the
reference on the first token, but numerics still diverge from position ~12 onward,
so the output is not yet correct. H20-DEBUG-PLAN.md tracks the remaining work with
the exact reproduction case; see H20-SM90-FINDINGS.md for the analysis.

Quantization
- `Platform.sf_pack_factor` separates two meanings that `fp8_sf_type` conflated:
  the GEMM scale type (FP32 on SM90) and the number of scales packed per element
  (1, instead of 4 UE8M0 exponents per int32). KV caches keep the ue8m0 byte layout.
- Requantize FP4 experts and ue8m0 dense weights to FP8 E4M3 with FP32 per-128
  scales while loading (`hugging_face/weights.py`, `h20_ops/quant.py`), so the
  runtime sees a plain FP8 checkpoint: `mxfp4` is disabled at runtime, expert
  weights are repacked as 2D, and `use_fp4_sparse_kv` is off since the FP4 cache
  kernels do not exist on Hopper.
- GEMM recipes switch to `(1, 128, 128)` with `disable_ue8m0_cast=True`, which is
  the only shape SM90 DeepGEMM accepts.

Attention
- `h20_ops/sparse_mla_sm90.py` adapts TileLang's `examples/deepseek_v32` sparse MLA
  kernel (which is Hopper-targeted) to the V4.1 layout: RoPE lives inside the
  512-wide latent, so the V3.2 `dim`/`tail` split is removed and QK/PV are both 512.
  Measured on H20: 104 TFLOP/s, bf16-noise accuracy. It takes no causal mask,
  because the indices are already causal -- deriving causality from the row number
  drops every index once the KV buffer is offset, which produced an all-NaN layer 0.
- `h20_ops/attn_sm90.py` re-implements `prefill_attn_varlen_sparse` and
  `decode_mla_mqa_sparse` with the same signatures as `attention_backend.py`, and
  registers them through `patch_imports`, so call sites are untouched and the
  FlashMLA-only module is never imported.
- Softmax normalisation clamps `sumexp`, so a padded row with no valid index yields
  zeros instead of 0/0 and cannot poison the whole hidden state.

Engram
- `h20_ops/engram_local.py` replaces `deep_ep.EngramBuffer.fetch`, which needs
  NCCL GIN (RDMA) and is unavailable on a single node, with a distributed gather
  over NVLink built from two `all_to_all`s. Row ownership follows the C++ layout
  (`owner = idx // num_local`). Verified against a full reference table on 8 ranks.

Other Blackwell assumptions removed
- DeepSelect's top-k kernel faults at launch on SM90, so `h20_ops/deep_select_sm90.py`
  reproduces its contract with `torch.topk` (end truncation, OOB fill, in-place
  output views). The shared-layer candidate-block optimisation is disabled because
  `fp8_fp4_sparse_mqa_logits` has no SM90 implementation, and the dense MQA-logits
  path is used instead; its fp32 output is narrowed for the block-max kernel.
- Decode-time index scoring uses `_decode_p_sum_sm90`: Hopper's paged kernel
  hard-requires 64-token pages while the cache uses 128, and the pages are strided
  views that cannot be split without a copy.
- `mega_mhc` / `mega_moe`, the FlashAttention-4 CuTe DSL kernels and the fused
  norm+rope+cast kernel are all SM100-only and take a Hopper fallback.
- `allow_cuda_sync()` is used for the few places that genuinely need a host read
  (all-to-all sizing, the ViT fallback, the NaN diagnostic) instead of disabling
  the sync guard globally.

Vendored submodules (not part of this commit; submodule gitlinks are unchanged)
- `vendor/DeepSelect/setup.py`: re-enable the `sm_90a` gencode that is commented
  out, otherwise top-k fails with "no kernel image".

Scripts: `h20_attn_check.py`, `h20_engram_check.py`, `h20_topk_check.py`,
`h20_smoke_check.py`, `h20_real_requant_check.py` are unit checks that run on 8x
H20; `h20_ask.py` is a one-prompt harness and `ref_next_token.py` produces the
official reference next-token for arbitrary ids, so both sides can be compared on
identical input.
2026-10-21 15:18:56 +08:00

89 lines
3.1 KiB
Python

"""Reference next-token prediction from the official V4.1 inference code.
`generate.py` always wraps text in a chat template, so its outputs are not directly comparable
with a raw-token harness. This script takes explicit token ids and prints the greedy next token
(plus the top-5), which makes the comparison exact regardless of prompt formatting.
torchrun --nproc-per-node 8 ref_next_token.py --ids 0,128803,2056,... --ckpt-path ...
Writes `<out>.json` with the ids, the chosen token and the top-5 so a harness can diff it.
"""
import argparse
import json
import os
import sys
import torch
import torch.distributed as dist
sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
from safetensors.torch import load_model # noqa: E402
from model import ModelArgs, Transformer # noqa: E402
def main() -> None:
parser = argparse.ArgumentParser()
parser.add_argument("--ckpt-path", required=True)
parser.add_argument("--config", required=True)
parser.add_argument("--ids", required=True, help="comma-separated prompt token ids")
parser.add_argument("--out", default="/data/deepinfer-h20/ref/next_token.json")
parser.add_argument("--topk", type=int, default=5)
args = parser.parse_args()
ids = [int(x) for x in args.ids.replace(" ", "").split(",") if x]
rank = int(os.getenv("RANK", "0"))
local_rank = int(os.getenv("LOCAL_RANK", "0"))
world_size = int(os.getenv("WORLD_SIZE", "1"))
torch.cuda.set_device(local_rank)
if world_size > 1:
dist.init_process_group("nccl")
torch.set_default_dtype(torch.bfloat16)
torch.set_num_threads(8)
with open(args.config) as f:
model_args = ModelArgs(**json.load(f))
model_args.temperature = 0.0
model_args.max_batch_size = 1
model_args.max_seq_len = 4096
# The engram hash table is built from the tokenizer's compressed token map, so it is not
# optional even for a text-only forward.
from transformers import AutoTokenizer
tokenizer = AutoTokenizer.from_pretrained(args.ckpt_path)
with torch.device("cuda"):
model = Transformer(model_args, tokenizer)
load_model(model, os.path.join(args.ckpt_path, f"model{rank}-mp{world_size}.safetensors"))
torch.set_default_device("cuda")
tokens = torch.tensor([ids], dtype=torch.long)
with torch.inference_mode():
# `Transformer.forward` returns (output_ids, logits, main_hidden).
output_ids, logits, _ = model.forward(tokens, 0)
row = logits[0, -1].float()
top = torch.topk(row, args.topk)
assert int(top.indices[0]) == int(output_ids[0, -1]), "argmax disagrees with the sampled id"
payload = {
"prompt_ids": ids,
"next_token": int(top.indices[0]),
"top_tokens": [int(x) for x in top.indices],
"top_logits": [round(float(x), 4) for x in top.values],
}
if rank == 0:
print(json.dumps(payload, ensure_ascii=False), flush=True)
os.makedirs(os.path.dirname(args.out), exist_ok=True)
with open(args.out, "w") as f:
json.dump(payload, f, ensure_ascii=False, indent=2)
if world_size > 1:
dist.destroy_process_group()
if __name__ == "__main__":
main()