unsloth/studio/backend/tests/test_diffusion_cache.py
Daniel Han b6b507c48b Key the auto step-cache on the pipe's default strength when the request omits it
The auto FBCache policy keyed on the full step count whenever strength was omitted, but the
loader only passes the strength kwarg when it is set, so an img2img/inpaint pipe then runs its
OWN signature default (< 1, e.g. FluxImg2ImgPipeline's 0.6). FBCache would engage on the full
28 steps while the pipe actually denoises ~16, degrading the image on exactly the short
trajectory the policy exists to keep uncached. Thread the pipe's signature default into the
policy via a new effective_request_strength helper (unit-tested), so the effective denoise count
matches what the pipe runs.
2026-07-06 14:49:47 +00:00

323 lines
12 KiB
Python

# SPDX-License-Identifier: AGPL-3.0-only
# Copyright 2026-present the Unsloth AI Inc. team. All rights reserved. See /studio/LICENSE.AGPL-3.0
"""Hermetic CPU tests for opt-in step caching (First-Block-Cache).
``diffusers`` is stubbed via ``sys.modules`` (the module under test imports
``FirstBlockCacheConfig`` lazily), and the pipeline is a fake that records the engaged config.
So normalisation, the CacheMixin (``enable_cache``) gating, threshold selection, and the
best-effort failure handling are all exercised without torch or a real diffusers model.
"""
from __future__ import annotations
import sys
import types
import pytest
from core.inference.diffusion_cache import (
DEFAULT_FBCACHE_THRESHOLD,
QUANT_FBCACHE_THRESHOLD,
TC_FBCACHE,
apply_step_cache,
normalize_transformer_cache,
)
# ── normalize_transformer_cache ────────────────────────────────────────────────────
def test_normalize_disabled_values_are_none():
for value in (None, "", " ", "none", "off", "OFF", "None"):
assert normalize_transformer_cache(value) is None
def test_normalize_fbcache_and_casing():
assert normalize_transformer_cache("fbcache") == TC_FBCACHE
assert normalize_transformer_cache("FBCache") == TC_FBCACHE
assert normalize_transformer_cache(" fbcache ") == TC_FBCACHE
def test_normalize_rejects_unknown():
with pytest.raises(ValueError):
normalize_transformer_cache("deepcache")
# ── apply_step_cache ───────────────────────────────────────────────────────────────
class _Config:
def __init__(self, threshold):
self.threshold = threshold
class _MixinTransformer:
"""A CacheMixin-style transformer: exposes ``enable_cache``."""
def __init__(self, *, fail = False):
self.fail = fail
self.enabled_with = None
def enable_cache(self, config):
if self.fail:
raise RuntimeError("block signature not recognised")
self.enabled_with = config
class _NonCacheMixinTransformer:
"""A transformer with no ``enable_cache`` (not a CacheMixin) -> must run uncached.
Its pipeline opens no ``cache_context``, so installing FBCache would crash at generation;
the load runs uncached instead (e.g. Z-Image)."""
def _pipe(transformer):
return types.SimpleNamespace(transformer = transformer)
def _stub_diffusers(monkeypatch, *, hook_recorder = None):
diffusers = types.ModuleType("diffusers")
diffusers.FirstBlockCacheConfig = _Config
monkeypatch.setitem(sys.modules, "diffusers", diffusers)
hooks = types.ModuleType("diffusers.hooks")
def _apply_first_block_cache(transformer, config):
if hook_recorder is not None:
hook_recorder["transformer"] = transformer
hook_recorder["config"] = config
hooks.apply_first_block_cache = _apply_first_block_cache
monkeypatch.setitem(sys.modules, "diffusers.hooks", hooks)
def test_disabled_mode_is_noop(monkeypatch):
_stub_diffusers(monkeypatch)
t = _MixinTransformer()
assert apply_step_cache(_pipe(t), mode = None) is None
assert apply_step_cache(_pipe(t), mode = "off") is None
assert t.enabled_with is None
def test_enable_cache_path_default_threshold(monkeypatch):
_stub_diffusers(monkeypatch)
t = _MixinTransformer()
engaged = apply_step_cache(_pipe(t), mode = "fbcache")
assert engaged == TC_FBCACHE
assert t.enabled_with.threshold == DEFAULT_FBCACHE_THRESHOLD
assert t._unsloth_step_cache == f"fbcache@{DEFAULT_FBCACHE_THRESHOLD}"
def test_quant_active_raises_default_threshold(monkeypatch):
_stub_diffusers(monkeypatch)
t = _MixinTransformer()
apply_step_cache(_pipe(t), mode = "fbcache", quant_active = True)
assert t.enabled_with.threshold == QUANT_FBCACHE_THRESHOLD
def test_explicit_threshold_overrides_quant(monkeypatch):
_stub_diffusers(monkeypatch)
t = _MixinTransformer()
apply_step_cache(_pipe(t), mode = "fbcache", threshold = 0.2, quant_active = True)
assert t.enabled_with.threshold == 0.2
def test_non_cachemixin_runs_uncached(monkeypatch):
# A transformer without enable_cache (e.g. Z-Image) must NOT install the standalone hook
# -- its pipeline opens no cache_context, so it runs uncached instead of crashing at gen.
rec: dict = {}
_stub_diffusers(monkeypatch, hook_recorder = rec)
t = _NonCacheMixinTransformer()
assert apply_step_cache(_pipe(t), mode = "fbcache") is None
assert rec == {} # the standalone hook was never called
def test_incompatible_model_runs_uncached(monkeypatch):
# enable_cache raising (e.g. unrecognised block signature) must not fail the load.
_stub_diffusers(monkeypatch)
t = _MixinTransformer(fail = True)
assert apply_step_cache(_pipe(t), mode = "fbcache") is None
def test_enable_cache_failure_rolls_back_partial_hooks(monkeypatch):
# enable_cache can raise after hooking some blocks; the reported-uncached model
# must not actually run half-cached, so the failure path calls disable_cache.
_stub_diffusers(monkeypatch)
t = _MixinTransformer(fail = True)
t.disabled = False
t.disable_cache = lambda: setattr(t, "disabled", True)
assert apply_step_cache(_pipe(t), mode = "fbcache") is None
assert t.disabled is True
def test_config_import_falls_back_to_hooks_module(monkeypatch):
# Older diffusers exports FirstBlockCacheConfig only from diffusers.hooks.
diffusers = types.ModuleType("diffusers") # no FirstBlockCacheConfig attribute
monkeypatch.setitem(sys.modules, "diffusers", diffusers)
hooks = types.ModuleType("diffusers.hooks")
hooks.FirstBlockCacheConfig = _Config
monkeypatch.setitem(sys.modules, "diffusers.hooks", hooks)
t = _MixinTransformer()
assert apply_step_cache(_pipe(t), mode = "fbcache") == TC_FBCACHE
assert t.enabled_with.threshold == DEFAULT_FBCACHE_THRESHOLD
def test_missing_transformer_is_none(monkeypatch):
_stub_diffusers(monkeypatch)
pipe = types.SimpleNamespace(transformer = None)
assert apply_step_cache(pipe, mode = "fbcache") is None
def test_diffusers_unavailable_runs_uncached(monkeypatch):
# no diffusers import -> best-effort returns None, load proceeds uncached. Block the
# hooks module too: the config import falls back to diffusers.hooks, which a REAL
# earlier import in the test session may have left cached in sys.modules.
monkeypatch.setitem(sys.modules, "diffusers", None)
monkeypatch.setitem(sys.modules, "diffusers.hooks", None)
t = _MixinTransformer()
assert apply_step_cache(_pipe(t), mode = "fbcache") is None
# ── the auto policy: normalize("auto") + generation-time toggling ──────────────────
from core.inference.diffusion_cache import ( # noqa: E402
FBCACHE_MIN_STEPS,
TC_AUTO,
effective_denoise_steps,
effective_request_strength,
maybe_toggle_step_cache,
)
# ── effective_denoise_steps (strength-aware step count for the auto policy) ─────────
def test_effective_steps_txt2img_is_full_count():
# No strength (txt2img / reference) -> the full requested step count.
assert effective_denoise_steps(28, None) == 28
assert effective_denoise_steps(28, 1.0) == 28 # full redraw denoises every step
def test_effective_steps_low_strength_shrinks_below_the_bar():
# A 28-step upscale at strength 0.35 denoises int(9.8) = 9 steps (diffusers get_timesteps
# floors the product), which is below FBCACHE_MIN_STEPS -> the auto policy must NOT engage
# FBCache there.
eff = effective_denoise_steps(28, 0.35)
assert eff == 9
assert eff < FBCACHE_MIN_STEPS
def test_effective_request_strength_uses_pipe_default_when_omitted():
import inspect
# txt2img (no init image) or a pipe without the strength kwarg -> full trajectory (None).
assert effective_request_strength(None, False, True, 0.6) is None
assert effective_request_strength(0.5, True, False, None) is None
# img2img with an explicit strength -> that value.
assert effective_request_strength(0.2, True, True, 0.6) == 0.2
# img2img with an OMITTED strength -> the pipe's own signature default (< 1), so the auto
# policy keys on the real (short) trajectory, not the full step count. This is the fix:
# int(28 * 0.6) = 16 real steps, not 28.
s = effective_request_strength(None, True, True, 0.6)
assert s == 0.6
assert effective_denoise_steps(28, s) == 16
# A non-numeric signature default (inspect.Parameter.empty) falls back to the full count.
assert effective_request_strength(None, True, True, inspect.Parameter.empty) is None
assert effective_request_strength(None, True, True, None) is None
def test_effective_steps_matches_diffusers_get_timesteps():
# Mirror diffusers exactly: it denoises init_timestep = min(int(num_inference_steps *
# strength), num_inference_steps) steps (the product is floored, not rounded).
for steps, strength in [(28, 0.35), (28, 0.8), (50, 0.5), (20, 0.99), (30, 0.1)]:
expected = max(1, min(int(steps * strength), steps))
assert effective_denoise_steps(steps, strength) == expected
def test_toggle_stays_off_for_low_strength_workflow(monkeypatch):
# End to end: a 28-step request would engage FBCache, but at strength 0.35 the
# effective ~10 steps keep it uncached.
_stub_diffusers(monkeypatch)
t = _ToggleTransformer()
mode = maybe_toggle_step_cache(_pipe(t), steps = effective_denoise_steps(28, 0.35))
assert mode is None and t.enables == 0
class _ToggleTransformer(_MixinTransformer):
"""CacheMixin-style fake with the disable side too, counting transitions."""
def __init__(self):
super().__init__()
self.enables = 0
self.disables = 0
def enable_cache(self, config):
super().enable_cache(config)
self.enables += 1
def disable_cache(self):
self.disables += 1
def test_normalize_auto_is_a_distinct_state():
assert normalize_transformer_cache("auto") == TC_AUTO
assert normalize_transformer_cache(" AUTO ") == TC_AUTO
def test_apply_treats_stray_auto_as_off(monkeypatch):
# AUTO must be resolved by the loader; if it ever reaches the engage call the
# load runs uncached instead of crashing.
_stub_diffusers(monkeypatch)
t = _MixinTransformer()
assert apply_step_cache(_pipe(t), mode = "auto") is None
assert t.enabled_with is None
def test_toggle_engages_at_the_step_bar(monkeypatch):
_stub_diffusers(monkeypatch)
t = _ToggleTransformer()
mode = maybe_toggle_step_cache(_pipe(t), steps = FBCACHE_MIN_STEPS)
assert mode == TC_FBCACHE and t.enables == 1
assert t.enabled_with.threshold == DEFAULT_FBCACHE_THRESHOLD
assert t._unsloth_step_cache
def test_toggle_uses_quant_threshold(monkeypatch):
_stub_diffusers(monkeypatch)
t = _ToggleTransformer()
maybe_toggle_step_cache(_pipe(t), steps = 28, quant_active = True)
assert t.enabled_with.threshold == QUANT_FBCACHE_THRESHOLD
def test_toggle_is_idempotent_when_engaged(monkeypatch):
_stub_diffusers(monkeypatch)
t = _ToggleTransformer()
maybe_toggle_step_cache(_pipe(t), steps = 28)
mode = maybe_toggle_step_cache(_pipe(t), steps = 28)
assert mode == TC_FBCACHE and t.enables == 1 and t.disables == 0
def test_toggle_disengages_below_the_bar(monkeypatch):
_stub_diffusers(monkeypatch)
t = _ToggleTransformer()
maybe_toggle_step_cache(_pipe(t), steps = 28)
mode = maybe_toggle_step_cache(_pipe(t), steps = 8)
assert mode is None and t.disables == 1
assert not t._unsloth_step_cache
# and it stays off on repeat calls (no flapping disable calls).
assert maybe_toggle_step_cache(_pipe(t), steps = 8) is None
assert t.disables == 1
def test_toggle_reengages_after_a_disable(monkeypatch):
_stub_diffusers(monkeypatch)
t = _ToggleTransformer()
maybe_toggle_step_cache(_pipe(t), steps = 28)
maybe_toggle_step_cache(_pipe(t), steps = 8)
mode = maybe_toggle_step_cache(_pipe(t), steps = 24)
assert mode == TC_FBCACHE and t.enables == 2
def test_toggle_noop_without_cache_support(monkeypatch):
_stub_diffusers(monkeypatch)
t = _NonCacheMixinTransformer()
assert maybe_toggle_step_cache(_pipe(t), steps = 28) is None
assert maybe_toggle_step_cache(_pipe(t), steps = 8) is None
def test_toggle_noop_without_transformer():
assert maybe_toggle_step_cache(types.SimpleNamespace(), steps = 28) is None