h3-blackwell-runtime/tools/compare_attention_backends.py

"""Compare direct attention kernels against captured Comfy block-0 output."""

import argparse
import time

import torch

from h3_blackwell_runtime.attention import AVAILABLE_BACKENDS, run_attention
from h3_blackwell_runtime.checkpoint import H3Checkpoint
from h3_blackwell_runtime.denoiser import H3PackedDenoiser


parser = argparse.ArgumentParser()
parser.add_argument("--capture-dir", default="/artifacts/capture")
parser.add_argument("--model", default="/models/minimax_h3_ref2va_pruned_nvfp4.safetensors")
args = parser.parse_args()

payload = torch.load(f"{args.capture_dir}/block0_qkv_prepared.pt", map_location="cuda", weights_only=False)
expected = torch.load(f"{args.capture_dir}/block0_attention.pt", map_location="cuda", weights_only=False)
q, k, v = payload["q"], payload["k"], payload["v"]
model = H3PackedDenoiser.from_checkpoint(H3Checkpoint(args.model)).eval()
out_proj = model.backbone.blocks[0].attention.out_proj

for name in AVAILABLE_BACKENDS:
    torch.cuda.synchronize()
    start = time.perf_counter()
    try:
        output = run_attention(q, k, v, backend=name, is_causal=False)
        torch.cuda.synchronize()
        output = out_proj(output.transpose(1, 2).reshape(q.shape[0], q.shape[2], -1).reshape(q.shape[2], -1).contiguous())
        delta = (output.float() - expected.float()).abs()
        print(f"{name} elapsed_s={time.perf_counter() - start:.3f} max_abs={delta.max().item():.6g} mean_abs={delta.mean().item():.6g}")
    except Exception as exc:
        print(f"{name} error={type(exc).__name__}: {exc}")