Stable Diffusion 2.x: Xformers
Date: 12/26/2022
Introduction to Xformers!
Intro
I have written a guide for setting up AUTOMATIC1111's stable diffusion locally over here. This is a quick tutorial on enabling Xformers how it can speed up image generation and lower VRAM usage.
AUTOMATIC1111's WEB UI with Xformers Enabled
To enable the Xformers usage on modern nVidia GPUs, all you have to do now is add a command line argument that will get called by your user BAT file.
webui-user.bat
@echo off
...
set COMMANDLINE_ARGS=--xformers
...
Everything after the = is treated a string so to add more command line parameters just add a space
between command line arguments.
Example.) Also hide progress bars.
set COMMANDLINE_ARGS=--xformers --no-progressbar-hiding
Here is a full list of COMMANDLINE_ARGS supported here.
What Is Xformers?
Flexible Transformers, defined by interoperable and optimized building blocks. You can read everything at Facebook.
The main advantage here is for people with slightly weaker GPUs to get more results quicker and in my humble opinion seems more stable.
There is a Cost
Due to the optimizations made, you do lose a bit of determinism which means replay/repeatability. This means that if you adjust the settings to re-render you can get a difference in the outputs even with a seed. It may not be radically different but I find this extremely useful if I want to lock something in but constantly re-render variations quicklys.
Orange Cat 01 - Without Xformers
This is a baseline image.
Text Prompt
An ((orange cat)) sitting on the roof of a (skyscraper) in a (cyberpunk city)
at night while its ((raining)), photo realistic, 8k
Negative Prompt
bad-artist
Settings
Steps: 100
Sampler: Euler a
CFG scale: 9
Seed: 3562015388
Size: 768x768
Model hash: 2c02b20a
Usage Details
GPU: RTX 3090
Render Time: 16 seconds
VRAM @ Idle: 5440 MB
VRAM @ Max: 9860 MB
Actual MAX VRAM Usage: 4420 MB
Orange Cat 02 - Without Xformers
The expectation is that there is no change on re-run.
Text Prompt
An ((orange cat)) sitting on the roof of a (skyscraper) in a (cyberpunk city)
at night while its ((raining)), photo realistic, 8k
Negative Prompt
bad-artist
Settings
Steps: 100
Sampler: Euler a
CFG scale: 9
Seed: 3562015388
Size: 768x768
Model hash: 2c02b20a
Usage Details
GPU: RTX 3090
Render Time: 16 seconds
VRAM @ Idle: 5420 MB
VRAM @ Max: 9860 MB
Actual MAX VRAM Usage: 4440 MB
Orange Cat 03 - With Xformers
There maybe expected small changes but used significantly lower VRAM amount and should have rendered faster.
Text Prompt
An ((orange cat)) sitting on the roof of a (skyscraper) in a (cyberpunk city)
at night while its ((raining)), photo realistic, 8k
Negative Prompt
bad-artist
Settings
Steps: 100
Sampler: Euler a
CFG scale: 9
Seed: 3562015388
Size: 768x768
Model hash: 2c02b20a
Usage Details
GPU: RTX 3090
Render Time: 14 seconds
VRAM @ Idle: 5422 MB
VRAM @ Max: 6076 MB
Actual MAX VRAM Usage: 654 MB
Orange Cat 04 - With Xformers
Text Prompt
An ((orange cat)) sitting on the roof of a (skyscraper) in a (cyberpunk city) at night while its ((raining)), photo realistic, 8k
Settings
Steps: 100
Sampler: Euler a
CFG scale: 9
Seed: 3562015388
Size: 768x768
Model hash: 2c02b20a
Usage Details
GPU: RTX 3090
Render Time: 13 seconds
VRAM @ Idle: 5422 MB
VRAM @ Max: 6077 MB
Actual MAX VRAM Usage: 655 MB
Usage Summary
There weren't variations this time around, but it doesn't mean they couldn't have happened with slightly different settings.
Shaved 3 seconds off of render time but the real highlight is that with Xformers, it used ~650 MB of VRAM vs. ~4400 MB of VRAM to output nearly identical images. This is a huge saving in VRAM!
Links
- Automatic1111 - Xformers Guide
- Facebook - Xformers