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317 changes: 317 additions & 0 deletions scripts/checkpoint_conversion/numerical_tests_kimi.py
Original file line number Diff line number Diff line change
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# Copyright (c) Meta Platforms, Inc. and affiliates.
# All rights reserved.
#
# This source code is licensed under the BSD-style license found in the
# LICENSE file in the root directory of this source tree.

"""Full text+image e2e logit parity: torchtitan Kimi-VL vs the released HF model.

Runs the released HF Kimi-VL (``trust_remote_code``) and torchtitan in ONE
process on the same text+image prompt and compares last-token logits. torchtitan
does its OWN Kimi image processing (``process_image`` + ``vision_to_patches``,
raster order), so the full pipeline is exercised (preprocessing + vision +
projector + scatter + DeepSeek-V3 text tower), not just the forward.

The released remote code targets transformers ~4.50.x and does NOT import on 5.x,
so run this in an env with ``transformers==4.50.3`` + ``tiktoken`` + ``blobfile``.

Precision: the HF reference runs at ``--hf_dtype`` (default float32, the model's
"true" output); torchtitan runs at ``--dtype`` (text) with ``--vision_dtype``
overriding only its vision encoder. ``--dtype float32`` is the correctness gate;
``--dtype bfloat16 --vision_dtype float16`` is the realistic config (~1e-2 KL).

Usage:
CUDA_VISIBLE_DEVICES=0 python -m \\
scripts.checkpoint_conversion.numerical_tests_kimi \\
--hf_model_path ~/hf_assets/moonshotai/Kimi-VL-A3B-Instruct \\
--tt_checkpoint_path outputs/kimi/kimi_vl_a3b_dcp --dtype float32

Add ``--force-hf-routing`` to make titan use HF's exact per-token expert
selections (diagnostic: removes the MoE routing-flip divergence).
"""

import argparse
import os

import torch
import torch.distributed.checkpoint as dcp
import torch.nn as nn
import torch.nn.functional as F
from PIL import Image

from torchtitan.components.checkpoint import ModelWrapper
from torchtitan.hf_datasets.multimodal.utils.image import (
process_image,
resize_to_patch_budget,
vision_to_patches,
)
from torchtitan.models.common.attention import ScaledDotProductAttention
from torchtitan.models.kimi_k2_7 import model_registry
from transformers import AutoModelForCausalLM, AutoProcessor

_MEDIA_TOKEN_ID = 163605
_PATCH_SIZE = 14
_MERGE_SIZE = 2
_PROMPT = "<|media_pad|>\nWhat is shown in this image? Describe it briefly."


class _VisionSDPA(nn.Module):
"""Bidirectional SDPA for one image (no padding -> full attention is exact)."""

def forward(self, q, k, v, **kwargs):
q, k, v = q.transpose(1, 2), k.transpose(1, 2), v.transpose(1, 2)
out = F.scaled_dot_product_attention(q, k, v, is_causal=False)
return out.transpose(1, 2)


@torch.no_grad()
def run_hf(hf_model_path, image_size, dtype, device):
"""Released HF Kimi-VL (trust_remote_code) on a text+image prompt.

Returns the raw image, tokenized input_ids, last-token logits, the projector
output (scattered vision features), and per-MoE-layer top-k expert indices.
"""
print(f"Loading released HF Kimi-VL on {device} ...")
proc = AutoProcessor.from_pretrained(hf_model_path, trust_remote_code=True)
model = (
AutoModelForCausalLM.from_pretrained(
hf_model_path, trust_remote_code=True, torch_dtype=dtype
)
.to(device)
.eval()
)

raw_image = (
torch.linspace(0, 255, image_size * image_size * 3)
.reshape(image_size, image_size, 3)
.to(torch.uint8)
)
# pyrefly: ignore [not-callable]
batch = proc(
text=[_PROMPT], images=[Image.fromarray(raw_image.numpy())], return_tensors="pt"
)

vis = {}
model.multi_modal_projector.register_forward_hook(
lambda m, i, o: vis.__setitem__("f", o.detach().float().cpu())
)
# MoE layers have a ``gate`` (MoEGate) whose forward returns
# (topk_idx, topk_weight, aux_loss); ``experts`` is a ModuleList (never
# called directly). Hook the gate to record the per-token expert selection.
expert_indices: dict[int, torch.Tensor] = {}
for i, layer in enumerate(model.language_model.model.layers):
if hasattr(layer.mlp, "gate"):
layer.mlp.gate.register_forward_hook(
lambda m, inp, out, i=i: expert_indices.__setitem__(
i, out[0].detach().cpu()
)
)

inputs = {
k: (v.to(device) if isinstance(v, torch.Tensor) else v)
for k, v in batch.items()
}
inputs["pixel_values"] = inputs["pixel_values"].to(dtype)
out = model(**inputs)
ref = {
"input_ids": batch["input_ids"].cpu(),
"raw_image": raw_image,
"last_logits": out.logits[:, -1, :].float().cpu(),
"vision_features": vis["f"],
"expert_indices": expert_indices,
}
del model
torch.cuda.empty_cache()
return ref


def _force_hf_routing(model, expert_indices, device):
"""Monkeypatch each MoE router to use HF's recorded top-k experts.

Diagnostic: titan routes every token to exactly the experts HF chose (still
computing its own gating weights at those experts via the real scores), so the
discrete routing-flip divergence is removed and any residual is the non-routing
math (attention / expert FFN / fp). ``expert_indices`` maps the HF layer index
to a ``(num_tokens, top_k)`` LongTensor.
"""
forced = 0
for key, layer in model.layers.items():
if not getattr(layer, "moe_enabled", False) or int(key) not in expert_indices:
continue
ids = expert_indices[int(key)]
ids = ids.view(1, ids.shape[0], ids.shape[-1]).to(device) # (1, L, K)
router = layer.moe.router
orig = router.forward

def forced_forward(x_BLD, expert_bias_E=None, _r=router, _o=orig, _ids=ids):
# Reuse the real score computation; override only the selection.
_, _, scores_BLE = _o(x_BLD, expert_bias_E)
topk = scores_BLE.gather(dim=-1, index=_ids)
if _r.route_norm:
topk = topk / (topk.sum(dim=-1, keepdim=True) + 1e-20)
topk = topk * _r.route_scale
return topk, _ids, scores_BLE

router.forward = forced_forward
forced += 1
return forced


@torch.no_grad()
def run_tt(model_flavor, checkpoint_path, ref, dtype, vision_dtype, force_hf_routing):
"""torchtitan Kimi-VL: its own image processing + forward on the same image."""
device = torch.device("cuda")
print(f"Loading torchtitan Kimi-VL ({model_flavor}) on {device} ...")
model_config = model_registry(model_flavor).model
with torch.device("meta"):
model = model_config.build()
model.to_empty(device="cpu")
# Cast before init_states so the complex64 ComplexRoPE cache survives.
model.to(dtype)
model.init_states(buffer_device=torch.device("cpu"))
state_dict = ModelWrapper(model)._get_state_dict()
dcp.load(state_dict, checkpoint_id=checkpoint_path)
model.to(device)

model.vision_encoder.to(vision_dtype) # mixed precision: ViT in vision_dtype
for layer in model.layers.values():
layer.attention.inner_attention = ScaledDotProductAttention.Config().build()
for layer in model.vision_encoder.layers.values():
layer.attn.flex_attention = _VisionSDPA()
model.eval()

if force_hf_routing:
n = _force_hf_routing(model, ref["expert_indices"], device)
print(f"forced HF routing on {n} MoE layers")

# titan's OWN Kimi image processing on the raw image (the real data path).
img = process_image(
Image.fromarray(ref["raw_image"].numpy()),
patch_size=_PATCH_SIZE,
merge_size=_MERGE_SIZE,
resize_fn=resize_to_patch_budget,
max_patches=4096,
max_patches_per_side=512,
image_mean=(0.5, 0.5, 0.5),
image_std=(0.5, 0.5, 0.5),
)
# MoonViT3d consumes raster-order patches (matching the released processor).
patches, grid = vision_to_patches(
img, # pyrefly: ignore [bad-argument-type]
patch_size=_PATCH_SIZE,
temporal_patch_size=1,
merge_size=_MERGE_SIZE,
patch_order="raster",
)
pixel_values = patches.unsqueeze(0).to(device=device, dtype=vision_dtype)
grid_thw = grid.unsqueeze(0).to(device)
tokens = ref["input_ids"].to(device)

# Sanity: titan's grid must yield the same vision-token count as HF produced
# (the placeholder run in input_ids), else the scatter compares different seqs.
n_titan = ((grid_thw[0, 1] // _MERGE_SIZE) * (grid_thw[0, 2] // _MERGE_SIZE)).item()
n_placeholders = (tokens == _MEDIA_TOKEN_ID).sum().item()
print(
f"tokens={tuple(tokens.shape)} pixel_values={tuple(pixel_values.shape)} "
f"grid_thw={grid_thw.tolist()} titan_vis_tokens={n_titan} "
f"hf_placeholders={n_placeholders}"
)
assert n_titan == n_placeholders, (
f"titan produced {n_titan} vision tokens but HF input_ids has "
f"{n_placeholders} placeholders -- preprocessing grids differ"
)

# Localize: titan's vision features (projector output) vs HF's, pre-scatter.
tt_feats = model.vision_encoder(pixel_values, grid_thw=grid_thw)
ref_feats = ref["vision_features"].float().reshape(-1, tt_feats.shape[-1])
tt_feats = tt_feats.float().cpu().reshape(-1, tt_feats.shape[-1])
vcos = F.cosine_similarity(ref_feats.flatten(), tt_feats.flatten(), dim=0).item()
vmax = (ref_feats - tt_feats).abs().max().item()
print(
f"vision features (pre-scatter): shape={tuple(tt_feats.shape)} "
f"cos={vcos:.6f} max_diff={vmax:.3e}"
)

logits = model(
tokens,
pixel_values=pixel_values,
grid_thw=grid_thw,
special_tokens={"image_id": _MEDIA_TOKEN_ID, "video_id": _MEDIA_TOKEN_ID},
)
return logits[:, -1, :].float().cpu().squeeze()


def compare(ref_logits, tt_logits) -> bool:
ref, tt = ref_logits.squeeze(), tt_logits.squeeze()
pq = F.log_softmax(ref, dim=-1)
qq = F.log_softmax(tt, dim=-1)
kl = F.kl_div(qq, pq, log_target=True, reduction="sum").item()
cos = F.cosine_similarity(ref, tt, dim=-1).item()
max_diff = (ref - tt).abs().max().item()
top1 = (ref.argmax() == tt.argmax()).item()
ov5 = len(set(ref.topk(5).indices.tolist()) & set(tt.topk(5).indices.tolist())) / 5
print(f"\n{'=' * 60}\nFull MM logit parity (torchtitan vs HF Kimi-VL)\n{'=' * 60}")
print(
f" KL={kl:.4e} cos={cos:.6f} max_diff={max_diff:.4e} "
f"top1={'Y' if top1 else 'N'} top5={ov5:.0%}"
)
passed = abs(kl) < 1e-3 # pyrefly: ignore [bad-argument-type]
print(
"RESULT: PASS (KL < 1e-3 -- fp noise)."
if passed
else "RESULT: FAIL (KL >= 1e-3)."
)
return passed


@torch.no_grad()
def main():
p = argparse.ArgumentParser()
p.add_argument(
"--hf_model_path",
default=os.path.expanduser("~/hf_assets/moonshotai/Kimi-VL-A3B-Instruct"),
)
p.add_argument("--tt_checkpoint_path", default="outputs/kimi/kimi_vl_a3b_dcp")
p.add_argument("--model_flavor", default="Kimi-VL-A3B")
p.add_argument("--image_size", type=int, default=336)
p.add_argument(
"--hf_dtype", default="float32", choices=["float32", "bfloat16", "float16"]
)
p.add_argument(
"--dtype", default="float32", choices=["float32", "bfloat16", "float16"]
)
# Mixed precision: bf16 is poor for the ViT's high-dynamic-range activations,
# so fp16 is the usual choice. Defaults to --dtype. (titan side only.)
p.add_argument(
"--vision_dtype", default=None, choices=["float32", "bfloat16", "float16"]
)
p.add_argument(
"--force-hf-routing",
action="store_true",
help="Force titan MoE routers to use HF's recorded expert selections "
"(diagnostic: removes routing-flip divergence to isolate the rest).",
)
args = p.parse_args()
device, dtype = torch.device("cuda"), getattr(torch, args.dtype)
vision_dtype = getattr(torch, args.vision_dtype) if args.vision_dtype else dtype
hf_dtype = getattr(torch, args.hf_dtype)
print(
f"hf_dtype={args.hf_dtype} titan text={args.dtype} "
f"titan vision={args.vision_dtype or args.dtype}"
)

ref = run_hf(args.hf_model_path, args.image_size, hf_dtype, device)
tt_logits = run_tt(
args.model_flavor,
args.tt_checkpoint_path,
ref,
dtype,
vision_dtype,
args.force_hf_routing,
)
if not compare(ref["last_logits"], tt_logits):
raise SystemExit(1)


if __name__ == "__main__":
main()
6 changes: 5 additions & 1 deletion tests/assets/tokenizer/tokenizer.json
Original file line number Diff line number Diff line change
Expand Up @@ -2047,7 +2047,11 @@
"</tool_call>": 2012,
"<tool_response>": 2013,
"</tool_response>": 2014,
"</think>": 2015
"</think>": 2015,
"<|media_pad|>": 2016,
"<|media_begin|>": 2017,
"<|media_end|>": 2018,
"[PAD]": 2019
Comment on lines +2051 to +2054

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add a comment on for which model they are introduced

Would be good to backfill the info for previous tokens (e.g. Qwen 3.5, RL, etc.)

@shuhuayu shuhuayu Jul 29, 2026

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agreed, but met a mechanical issue that this json file is loaded by a strict parser and does not allow inline comments starting with // and i tested it locally.

},
"merges": []
}
Expand Down
32 changes: 32 additions & 0 deletions tests/assets/tokenizer/tokenizer_config.json
Original file line number Diff line number Diff line change
Expand Up @@ -143,6 +143,38 @@
"rstrip": false,
"single_word": false,
"special": true
},
"2016": {
"content": "<|media_pad|>",
"lstrip": false,
"normalized": false,
"rstrip": false,
"single_word": false,
"special": true
},
"2017": {
"content": "<|media_begin|>",
"lstrip": false,
"normalized": false,
"rstrip": false,
"single_word": false,
"special": true
},
"2018": {
"content": "<|media_end|>",
"lstrip": false,
"normalized": false,
"rstrip": false,
"single_word": false,
"special": true
},
"2019": {
"content": "[PAD]",
"lstrip": false,
"normalized": false,
"rstrip": false,
"single_word": false,
"special": true
}
},
"bos_token": "<|begin_of_text|>",
Expand Down
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