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2026-10-07 06:13:43 -07:00

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Python

# SPDX-License-Identifier: Apache-2.0
"""Low-overhead performance accounting for modular training.
The monitor counts logical Transformer invocations at the role boundary. This
is important for distillation: one optimizer step may contain several student
rollouts plus critic and teacher forwards. FLOPs are an analytic estimate of
the Transformer core; measured step and sample throughput remain exact wall
clock metrics.
"""
from __future__ import annotations
import math
from collections import defaultdict
from dataclasses import dataclass
from typing import Any
import torch
from fastvideo.attention.backends.video_sparse_attn import compute_topk
from fastvideo.forward_context import get_forward_context
_FLOPS_PER_TFLOP = 1.0e12
@dataclass(slots=True)
class _ForwardWork:
role: str
forward_flops: float
useful_flops: float
causal_chunks: int
query_frames: int
query_tokens: int
attention_pairs: float
dense_attention_pairs: float
def infer_peak_bf16_tflops(device_name: str) -> float | None:
"""Infer dense BF16 tensor-core peak TFLOP/s from a CUDA device name.
Values intentionally exclude structured sparsity. Explicit configuration
should be used when board form factor or clocks differ from the common
data-center variant.
"""
name = device_name.upper()
# Order matters: GB200 contains B200.
peaks = (
("GB200", 2500.0),
("B200", 2250.0),
("H200", 989.5),
("H100", 989.5),
("L40S", 362.05),
("A100", 312.0),
("A40", 149.7),
)
return next((peak for token, peak in peaks if token in name), None)
def _arch_config(module: torch.nn.Module) -> Any | None:
config = getattr(module, "config", None)
return getattr(config, "arch_config", config)
def _first_tensor(value: Any) -> torch.Tensor | None:
if isinstance(value, torch.Tensor):
return value
if isinstance(value, list | tuple):
return next((item for item in value if isinstance(item, torch.Tensor)), None)
return None
def _output_requires_grad(output: Any) -> bool:
if isinstance(output, torch.Tensor):
return bool(output.requires_grad)
if isinstance(output, dict):
return any(_output_requires_grad(value) for value in output.values())
if isinstance(output, list | tuple):
return any(_output_requires_grad(value) for value in output)
return False
def _blockwise_causal_frame_pairs(
num_frames: int,
frames_per_block: int,
local_attn_size: int,
) -> int:
"""Frame-level pairs used by full-sequence block-causal training."""
total = 0
block = max(1, frames_per_block)
for start in range(0, num_frames, block):
end = min(start + block, num_frames)
attended_start = 0 if local_attn_size < 0 else max(0, end - local_attn_size)
total += (end - start) * (end - attended_start)
return total
def _teacher_forcing_frame_pairs(
num_frames: int,
frames_per_block: int,
) -> int:
"""Pairs for causal Wan's concatenated ``[clean | noisy]`` mask.
Clean and noisy query blocks each attend every frame, which is the same
count as a full block-causal mask with no local window.
"""
return 2 * _blockwise_causal_frame_pairs(num_frames, frames_per_block, -1)
def _vsa_attention_pairs(
seq_len: int,
metadata: Any,
) -> tuple[float, int]:
"""Return nominal sparse token pairs and tile count.
The kernel keeps a clamped top-k of key tiles per query tile; the nominal
pair count scales the dense count by that tile fraction.
"""
block_sizes = getattr(metadata, "variable_block_sizes", None)
num_blocks = int(block_sizes.numel()) if block_sizes is not None else 0
if num_blocks <= 0:
return float(seq_len * seq_len), 0
sparsity = float(getattr(metadata, "VSA_sparsity", 0.0))
topk = compute_topk(sparsity, num_blocks)
return float(seq_len * seq_len) * topk / num_blocks, num_blocks
def estimate_transformer_forward(
module: torch.nn.Module,
kwargs: dict[str, Any],
output: Any,
*,
role: str,
attention_metadata: Any | None,
cross_attention_cached: bool = False,
) -> _ForwardWork | None:
"""Estimate one Wan-style Transformer invocation from its logical input."""
hidden_states = _first_tensor(kwargs.get("hidden_states"))
if hidden_states is None or hidden_states.ndim != 5:
return None
arch = _arch_config(module)
if arch is None:
return None
required = ("hidden_size", "ffn_dim", "num_layers", "patch_size")
if any(not hasattr(arch, name) for name in required):
return None
batch_size = int(hidden_states.shape[0])
raw_frames = int(hidden_states.shape[2])
raw_height = int(hidden_states.shape[3])
raw_width = int(hidden_states.shape[4])
patch_size = arch.patch_size
patch: tuple[int,
...] = ((1, patch_size,
patch_size) if isinstance(patch_size, int) else tuple(int(value) for value in patch_size))
if len(patch) != 3 or any(value <= 0 for value in patch):
return None
frames = raw_frames // patch[0]
spatial_tokens = (raw_height // patch[1]) * (raw_width // patch[2])
seq_len = frames * spatial_tokens
if seq_len <= 0:
return None
hidden_size = int(arch.hidden_size)
ffn_dim = int(arch.ffn_dim)
num_layers = int(arch.num_layers)
context = _first_tensor(kwargs.get("encoder_hidden_states"))
context_tokens = int(context.shape[-2]) if context is not None and context.ndim >= 2 else 0
image_context = _first_tensor(kwargs.get("encoder_hidden_states_image"))
if image_context is not None and image_context.ndim >= 2:
context_tokens += int(image_context.shape[-2])
is_causal = hasattr(module, "num_frame_per_block")
teacher_forcing = is_causal and _first_tensor(kwargs.get("clean_x")) is not None
query_tokens = seq_len
dense_pairs = float(seq_len * seq_len)
vsa_tiles = 0
causal_chunks = 0
if is_causal:
frames_per_block = int(getattr(module, "num_frame_per_block", 1))
causal_chunks = math.ceil(frames / max(1, frames_per_block))
local_attn_size = int(getattr(module, "local_attn_size", -1))
kv_cache = kwargs.get("kv_cache")
if kv_cache is not None:
current_start = int(kwargs.get("current_start", 0))
# Causal Wan caps the KV window at
# GLOBAL_ATTN_COMPAT_MAX_LATENT_FRAMES (21) frames when
# local_attn_size is unset; sliding_window_num_frames only
# sizes the streaming KV cache. MatrixGame2's 15-frame
# compatibility window is not modeled here.
max_frames = local_attn_size if local_attn_size >= 0 else 21
key_tokens = min(current_start + seq_len, max_frames * spatial_tokens)
attention_pairs = float(seq_len * key_tokens)
dense_pairs = float(seq_len * (current_start + seq_len))
elif teacher_forcing:
query_tokens = 2 * seq_len
attention_pairs = float(_teacher_forcing_frame_pairs(frames, frames_per_block) * spatial_tokens**2)
dense_pairs = float(query_tokens * query_tokens)
else:
attention_pairs = float(
_blockwise_causal_frame_pairs(frames, frames_per_block, local_attn_size) * spatial_tokens**2)
else:
attention_pairs, vsa_tiles = _vsa_attention_pairs(seq_len, attention_metadata)
# Causal Wan pads text to ``text_len`` before every cross-attention block.
if is_causal:
context_tokens = max(context_tokens, int(getattr(module, "text_len", 0)))
b = batch_size
seq_length = query_tokens
dim = hidden_size
# Four self-attention projections, two MLP projections, cross-attention
# Q/K/V/out projections, and the two attention matmuls.
per_layer = (8.0 * b * seq_length * dim * dim + 4.0 * b * seq_length * dim * ffn_dim +
4.0 * b * seq_length * dim * dim +
(0.0 if cross_attention_cached else 4.0 * b * context_tokens * dim * dim) +
4.0 * b * seq_length * context_tokens * dim + 4.0 * b * attention_pairs * dim)
if vsa_tiles:
# Wan VSA adds one gate projection and dense pooled QK/AV matmuls.
per_layer += 2.0 * b * seq_length * dim * dim
per_layer += 4.0 * b * vsa_tiles * vsa_tiles * dim
forward_flops = per_layer * num_layers
backward_expected = _output_requires_grad(output)
# Standard MFU counts model-algorithm FLOPs, excluding activation
# checkpoint recompute: training is approximately F + 2B = 3F.
useful_flops = forward_flops * (3.0 if backward_expected else 1.0)
return _ForwardWork(
role=role,
forward_flops=forward_flops,
useful_flops=useful_flops,
causal_chunks=causal_chunks,
query_frames=b * (2 * frames if teacher_forcing else frames),
query_tokens=b * query_tokens,
attention_pairs=b * attention_pairs,
dense_attention_pairs=b * dense_pairs,
)
class TrainingPerformanceMonitor:
"""Count per-role Transformer work for one optimizer step at a time."""
def __init__(self) -> None:
self._handles: list[Any] = []
self._work: list[_ForwardWork] = []
self._forward_calls: dict[str, int] = defaultdict(int)
self._backward_forwards: dict[str, int] = defaultdict(int)
def attach(self, role_models: dict[str, Any]) -> None:
self.close()
for role, model in role_models.items():
transformer = getattr(model, "transformer", None)
if not isinstance(transformer, torch.nn.Module):
continue
cached_cross_attention: list[bool] = []
def pre_hook(
module: torch.nn.Module,
args: tuple[Any, ...],
kwargs: dict[str, Any],
*,
cache_state: list[bool] = cached_cross_attention,
) -> None:
del module, args
cache = kwargs.get("crossattn_cache")
initialized = (isinstance(cache, list) and bool(cache)
and all(isinstance(item, dict) and bool(item.get("is_init", False)) for item in cache))
cache_state.append(initialized)
def hook(
module: torch.nn.Module,
args: tuple[Any, ...],
kwargs: dict[str, Any],
output: Any,
*,
role_name: str = role,
cache_state: list[bool] = cached_cross_attention,
) -> None:
del args
self._forward_calls[role_name] += 1
if _output_requires_grad(output):
self._backward_forwards[role_name] += 1
try:
metadata = get_forward_context().attn_metadata
except AssertionError:
metadata = None
try:
work = estimate_transformer_forward(
module,
kwargs,
output,
role=role_name,
attention_metadata=metadata,
cross_attention_cached=(cache_state.pop() if cache_state else False),
)
except Exception:
# Metrics must never abort a training run.
work = None
if work is not None:
self._work.append(work)
self._handles.append(transformer.register_forward_pre_hook(pre_hook, with_kwargs=True))
self._handles.append(transformer.register_forward_hook(hook, with_kwargs=True))
def reset(self) -> None:
self._work.clear()
self._forward_calls.clear()
self._backward_forwards.clear()
def close(self) -> None:
for handle in self._handles:
handle.remove()
self._handles.clear()
def metrics(
self,
*,
step_time_sec: float,
local_batch_size: int,
grad_accum: int,
world_size: int,
sp_size: int,
peak_tflops_per_gpu: float | None,
) -> dict[str, float]:
if step_time_sec <= 0.0:
return {}
world_size = max(1, int(world_size))
sp_size = max(1, int(sp_size))
data_parallel_size = max(1, world_size // sp_size)
accumulation = max(1, int(grad_accum))
sample_scale_to_world = data_parallel_size * accumulation
work_scale_to_world = data_parallel_size
metrics = {
"perf/steps_per_sec": 1.0 / step_time_sec,
"perf/samples_per_sec": (max(0, int(local_batch_size)) * sample_scale_to_world / step_time_sec),
"perf/model_forward_calls": float(sum(self._forward_calls.values())),
}
for role, calls in self._forward_calls.items():
prefix = f"perf/role/{role}"
metrics[f"{prefix}/forward_calls"] = float(calls)
metrics[f"{prefix}/backward_forwards"] = float(self._backward_forwards[role])
if not self._work:
return metrics
useful_flops = sum(item.useful_flops for item in self._work) * work_scale_to_world
query_frames = sum(item.query_frames for item in self._work) * work_scale_to_world
query_tokens = sum(item.query_tokens for item in self._work) * work_scale_to_world
attention_pairs = sum(item.attention_pairs for item in self._work)
dense_pairs = sum(item.dense_attention_pairs for item in self._work)
achieved_tflops_per_gpu = useful_flops / step_time_sec / world_size / _FLOPS_PER_TFLOP
metrics.update({
"perf/causal_chunks": float(sum(item.causal_chunks for item in self._work)),
"perf/query_latent_frames_per_sec": query_frames / step_time_sec,
"perf/query_tokens_per_sec": query_tokens / step_time_sec,
"perf/attention_density": (attention_pairs / dense_pairs if dense_pairs > 0.0 else 1.0),
"perf/estimated_tflops_per_gpu": achieved_tflops_per_gpu,
})
if peak_tflops_per_gpu is not None:
metrics["perf/peak_tflops_per_gpu"] = peak_tflops_per_gpu
metrics["perf/estimated_mfu"] = achieved_tflops_per_gpu / peak_tflops_per_gpu
by_role: dict[str, list[_ForwardWork]] = defaultdict(list)
for item in self._work:
by_role[item.role].append(item)
for role, items in by_role.items():
prefix = f"perf/role/{role}"
metrics[f"{prefix}/causal_chunks"] = float(sum(item.causal_chunks for item in items))
role_flops = sum(item.useful_flops for item in items) * work_scale_to_world
metrics[f"{prefix}/estimated_tflops_per_gpu"] = (role_flops / step_time_sec / world_size / _FLOPS_PER_TFLOP)
return metrics