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127 lines
3.4 KiB
Markdown
127 lines
3.4 KiB
Markdown
## Caching
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Caching methods accelerate diffusion inference by reusing intermediate computations when changes between steps are small.
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### Cache Modes
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| Mode | Target | Description |
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|------|--------|-------------|
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| `ucache` | UNET models | Condition-level caching with error tracking |
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| `easycache` | DiT models | Condition-level cache |
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| `dbcache` | DiT models | Block-level L1 residual threshold |
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| `taylorseer` | DiT models | Taylor series approximation |
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| `cache-dit` | DiT models | Combined DBCache + TaylorSeer |
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### UCache (UNET Models)
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UCache caches the residual difference (output - input) and reuses it when input changes are below threshold.
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```bash
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sd-cli -m model.safetensors -p "a cat" --cache-mode ucache --cache-option "threshold=1.5"
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```
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#### Parameters
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| Parameter | Description | Default |
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|-----------|-------------|---------|
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| `threshold` | Error threshold for reuse decision | 1.0 |
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| `start` | Start caching at this percent of steps | 0.15 |
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| `end` | Stop caching at this percent of steps | 0.95 |
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| `decay` | Error decay rate (0-1) | 1.0 |
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| `relative` | Scale threshold by output norm (0/1) | 1 |
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| `reset` | Reset error after computing (0/1) | 1 |
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#### Reset Parameter
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The `reset` parameter controls error accumulation behavior:
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- `reset=1` (default): Resets accumulated error after each computed step. More aggressive caching, works well with most samplers.
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- `reset=0`: Keeps error accumulated. More conservative, recommended for `euler_a` sampler.
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### EasyCache (DiT Models)
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Condition-level caching for DiT models. Caches and reuses outputs when input changes are below threshold.
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```bash
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--cache-mode easycache --cache-option "threshold=0.3"
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```
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#### Parameters
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| Parameter | Description | Default |
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|-----------|-------------|---------|
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| `threshold` | Input change threshold for reuse | 0.2 |
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| `start` | Start caching at this percent of steps | 0.15 |
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| `end` | Stop caching at this percent of steps | 0.95 |
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### Cache-DIT (DiT Models)
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For DiT models like FLUX and QWEN, use block-level caching modes.
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#### DBCache
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Caches blocks based on L1 residual difference threshold:
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```bash
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--cache-mode dbcache --cache-option "threshold=0.25,warmup=4"
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```
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#### TaylorSeer
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Uses Taylor series approximation to predict block outputs:
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```bash
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--cache-mode taylorseer
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```
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#### Cache-DIT (Combined)
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Combines DBCache and TaylorSeer:
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```bash
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--cache-mode cache-dit --cache-preset fast
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```
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#### Parameters
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| Parameter | Description | Default |
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|-----------|-------------|---------|
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| `Fn` | Front blocks to always compute | 8 |
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| `Bn` | Back blocks to always compute | 0 |
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| `threshold` | L1 residual difference threshold | 0.08 |
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| `warmup` | Steps before caching starts | 8 |
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#### Presets
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Available presets: `slow`, `medium`, `fast`, `ultra` (or `s`, `m`, `f`, `u`).
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```bash
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--cache-mode cache-dit --cache-preset fast
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```
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#### SCM Options
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Steps Computation Mask controls which steps can be cached:
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```bash
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--scm-mask "1,1,1,1,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,1"
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```
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Mask values: `1` = compute, `0` = can cache.
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| Policy | Description |
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|--------|-------------|
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| `dynamic` | Check threshold before caching |
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| `static` | Always cache on cacheable steps |
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```bash
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--scm-policy dynamic
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```
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### Performance Tips
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- Start with default thresholds and adjust based on output quality
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- Lower threshold = better quality, less speedup
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- Higher threshold = more speedup, potential quality loss
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- More steps generally means more caching opportunities
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