Files
effectcraft/tools/sam2_video_reference.py
T
Kristian MyramandClaude Sonnet 5.5 e4f4fea0f2 S2.21: memory encoder matches PyTorch
Mask down-sampler, feature fuser and projection, sine position encoding,
occlusion embedding and bfloat16 rounding of stored memories. Max abs error
3.5e-6 on the memory features, 6e-8 on the position encoding.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
2026-10-30 08:43:30 +01:00

113 lines
4.9 KiB
Python

#!/usr/bin/env python
"""Dump SAM 2 video reference tensors (CPU, float32) for the Rust port's reference tests.
Usage: python -I tools/sam2_video_reference.py MODEL_DIR OUT.safetensors
Runs `Sam2VideoModel` on a 7-frame synthetic clip (a textured disc moving right, hidden behind a bar on
frames 4 and 5), prompted with one click on frame 2, then tracks forward (2..6) and backward (2..0).
Saves the preprocessed frames, every frame's low-resolution mask and object score, the stored memory
features and object pointers, and the inputs/outputs of the memory encoder and memory attention.
"""
import sys
import numpy as np
import torch
import torch.nn.functional as F
from safetensors.torch import save_file
from transformers import Sam2VideoModel
from transformers.models.sam2_video.modeling_sam2_video import Sam2VideoInferenceSession
T, SIZE, PROMPT_FRAME = 7, 256, 2
def clip():
rng = np.random.default_rng(3)
yy, xx = np.mgrid[0:SIZE, 0:SIZE].astype(np.float32)
bg = 0.3 + 0.2 * np.sin(xx / 9.0) * np.cos(yy / 7.0)
frames = []
for t in range(T):
cx, cy = 80 + 12 * t, 128
disc = np.hypot(xx - cx, yy - cy) < 34
img = np.stack([bg, bg * 0.8 + 0.1, bg * 0.6 + 0.3], -1)
tex = 0.85 + 0.1 * np.sin((xx - cx) / 5)
img[disc] = np.stack([tex, 0.4 + 0.1 * np.cos((yy - cy) / 5), 0.15 + 0 * xx], -1)[disc]
if t in (4, 5): # a bar hides the disc
img[:, int(cx) - 50 : int(cx) + 50] = 0.2
img += rng.normal(0, 0.01, img.shape).astype(np.float32)
frames.append((img.clip(0, 1) * 255).astype(np.uint8))
return frames, (80 + 12 * PROMPT_FRAME, 128)
def main(model_dir, out):
torch.manual_seed(0)
torch.set_num_threads(4)
model = Sam2VideoModel.from_pretrained(model_dir).eval()
frames, click = clip()
mean = torch.tensor([0.485, 0.456, 0.406]).view(1, 3, 1, 1)
std = torch.tensor([0.229, 0.224, 0.225]).view(1, 3, 1, 1)
x = torch.from_numpy(np.stack(frames)).permute(0, 3, 1, 2).float() / 255.0
x = F.interpolate(x, size=(1024, 1024), mode="bilinear", align_corners=False)
pixels = (x - mean) / std
taps = {"clip.pixel_values": pixels}
first = {"enc": True, "attn": True}
def enc_hook(_m, args, kwargs, out):
if first["enc"]:
first["enc"] = False
vf = args[0] if args else kwargs["vision_features"]
masks = args[1] if len(args) > 1 else kwargs["masks"]
taps["mem.enc.vision_features"] = vf.detach().float().clone()
taps["mem.enc.masks"] = masks.detach().float().clone()
taps["mem.enc.out_features"] = out[0].detach().float().clone()
taps["mem.enc.out_pos"] = out[1].detach().float().clone()
def attn_hook(_m, args, kwargs, out):
if first["attn"]:
first["attn"] = False
for k in ("current_vision_features", "memory", "current_vision_position_embeddings", "memory_posision_embeddings"):
taps[f"mem.attn.{k}"] = kwargs[k].detach().float().clone()
taps["mem.attn.num_pointers"] = torch.tensor([float(kwargs["num_object_pointer_tokens"])])
taps["mem.attn.out"] = out.detach().float().clone()
model.memory_encoder.register_forward_hook(enc_hook, with_kwargs=True)
model.memory_attention.register_forward_hook(attn_hook, with_kwargs=True)
sess = Sam2VideoInferenceSession(video=pixels, video_height=SIZE, video_width=SIZE, dtype=torch.float32)
obj_idx = sess.obj_id_to_idx(1)
scale = 1024.0 / SIZE
sess.add_point_inputs(
obj_idx,
PROMPT_FRAME,
{
"point_coords": torch.tensor([[[[click[0] * scale, click[1] * scale]]]], dtype=torch.float32),
"point_labels": torch.tensor([[[1]]], dtype=torch.int32),
},
)
sess.obj_with_new_inputs = [1]
def record(tag, o):
taps[f"video.{tag}.{o.frame_idx}.pred_masks"] = o.pred_masks.detach().float().clone()
taps[f"video.{tag}.{o.frame_idx}.score"] = o.object_score_logits.detach().float().clone()
with torch.no_grad():
record("prompt", model(sess, frame_idx=PROMPT_FRAME))
for o in model.propagate_in_video_iterator(sess, start_frame_idx=PROMPT_FRAME):
record("fwd", o)
for o in model.propagate_in_video_iterator(sess, start_frame_idx=PROMPT_FRAME, reverse=True):
record("rev", o)
d = sess.output_dict_per_obj[obj_idx]
for kind in ("cond_frame_outputs", "non_cond_frame_outputs"):
for f, o in d[kind].items():
taps[f"state.{f}.maskmem_features"] = o["maskmem_features"].detach().float().clone()
taps[f"state.{f}.maskmem_pos_enc"] = o["maskmem_pos_enc"].detach().float().clone()
taps[f"state.{f}.object_pointer"] = o["object_pointer"].detach().float().clone()
save_file({k: v.contiguous() for k, v in taps.items()}, out)
print(f"wrote {len(taps)} tensors to {out}")
if __name__ == "__main__":
if len(sys.argv) != 3:
sys.exit(__doc__)
main(sys.argv[1], sys.argv[2])