ComfyUI Model Quantizer

A comprehensive custom node pack for ComfyUI that provides advanced tools for quantizing model weights to lower precision formats like FP16, BF16, and true FP8 types, with specialized support for ControlNet models.

Overview

This node pack provides powerful quantization tools directly within ComfyUI, including:

Standard Quantization Nodes

1. Model To State Dict: Extracts the state dictionary from a model object and attempts to normalize keys.
2. Quantize Model to FP8 Format: Converts model weights directly to float8_e4m3fn or float8_e5m2 format (requires CUDA).
3. Quantize Model Scaled: Applies simulated FP8 scaling (per-tensor or per-channel) and then casts the model to float16, bfloat16, or keeps the original format.
4. Save As SafeTensor: Saves the processed state dictionary to a .safetensors file at a specified path.

NEW: ControlNet FP8 Quantization Nodes

5. ControlNet FP8 Quantizer: Advanced FP8 quantization specifically designed for ControlNet models with precision-aware quantization, tensor calibration, and ComfyUI folder integration.
6. ControlNet Metadata Viewer: Analyzes and displays ControlNet model metadata, tensor information, and structure for debugging and optimization.

Installation

1. Clone or download this repository into your ComfyUI's custom_nodes directory.

   • Example using git:

     cd ComfyUI/custom_nodes
     git clone [https://github.com/YourUsername/YourRepoName.git](https://github.com/YourUsername/YourRepoName.git) ComfyUI-ModelQuantizer
     # Replace with your actual repo URL and desired folder name

   • Alternatively, download the ZIP and extract it into ComfyUI/custom_nodes/ComfyUI-ModelQuantizer.

2. Install dependencies:

   cd ComfyUI/custom_nodes/ComfyUI-ModelQuantizer
   pip install -r requirements.txt

3. For ControlNet quantization, ensure your ControlNet models are in the correct folder:

   ComfyUI/models/controlnet/
   ├── control_v11p_sd15_canny.safetensors
   ├── control_v11p_sd15_openpose.safetensors
   └── ...
   

4. Restart ComfyUI.

Usage

Model To State Dict

• Category: Model Quantization/Utils
• Function: Extracts state dict from a MODEL object, stripping common prefixes.
• Inputs:
  • model: The input MODEL object.
• Outputs:
  • model_state_dict: The extracted state dictionary.

Quantize Model to FP8 Format

• Category: Model Quantization/FP8 Direct
• Function: Converts model weights directly to a specific FP8 format. Requires CUDA.
• Inputs:
  • model_state_dict: The state dictionary to quantize.
  • fp8_format: The target FP8 format (float8_e5m2 or float8_e4m3fn).
• Outputs:
  • quantized_model_state_dict: The state dictionary with FP8 tensors.

Quantize Model Scaled

• Category: Model Quantization
• Function: Applies simulated FP8 value scaling and then casts to FP16, BF16, or keeps the original dtype. Useful for size reduction with good compatibility.
• Inputs:
  • model_state_dict: The state dictionary to quantize.
  • scaling_strategy: How to simulate scaling (per_tensor or per_channel).
  • processing_device: Where to perform calculations (Auto, CPU, GPU).
  • output_dtype: Final data type (Original, float16, bfloat16). Defaults to float16.
• Outputs:
  • quantized_model_state_dict: The processed state dictionary.

Save As SafeTensor

• Category: Model Quantization/Save
• Function: Saves the processed state dictionary to a .safetensors file.
• Inputs:
  • quantized_model_state_dict: The state dictionary to save.
  • absolute_save_path: The full path (including filename) where the model will be saved.
• Outputs: None (Output node).

ControlNet FP8 Quantizer

• Category: Model Quantization/ControlNet
• Function: Advanced FP8 quantization specifically designed for ControlNet models with precision-aware quantization and tensor calibration.
• Inputs:
  • controlnet_model: Dropdown selection of ControlNet models from models/controlnet/ folder
  • fp8_format: FP8 format (float8_e4m3fn recommended, or float8_e5m2)
  • quantization_strategy: per_tensor (faster) or per_channel (better quality)
  • activation_clipping: Enable percentile-based outlier handling (recommended)
  • custom_output_name: Optional custom filename for output
  • calibration_samples: Number of samples for tensor calibration (10-1000, default: 100)
  • preserve_metadata: Preserve original metadata in output file
• Outputs:
  • status: Operation status and result message
  • metadata_info: JSON-formatted metadata information
  • quantization_stats: Detailed compression statistics and ratios

ControlNet Metadata Viewer

• Category: Model Quantization/ControlNet
• Function: Analyzes and displays ControlNet model metadata, tensor information, and structure.
• Inputs:
  • controlnet_model: Dropdown selection of ControlNet models from models/controlnet/ folder
• Outputs:
  • metadata: JSON-formatted original metadata
  • tensor_info: Detailed tensor information including shapes, dtypes, and sizes
  • model_analysis: Model structure analysis including layer types and statistics

Example Workflows

Standard Model Quantization

1. Load a model using a standard loader (e.g., Load Checkpoint).
2. Connect the MODEL output to the Model To State Dict node.
3. Connect the model_state_dict output from Model To State Dict to Quantize Model Scaled.
4. In Quantize Model Scaled, select your desired scaling_strategy and set output_dtype to float16 (for size reduction).
5. Connect the quantized_model_state_dict output from Quantize Model Scaled to the Save Model as SafeTensor node.
6. Specify the absolute_save_path in the Save Model as SafeTensor node.
7. Queue the prompt.
8. Restart ComfyUI or refresh loaders to find the saved model.

ControlNet FP8 Quantization

1. Add ControlNet FP8 Quantizer node to your workflow.
2. Select your ControlNet model from the dropdown (automatically populated from models/controlnet/).
3. Configure settings:
   • FP8 Format: float8_e4m3fn (recommended for most cases)
   • Strategy: per_channel (better quality) or per_tensor (faster)
   • Activation Clipping: True (recommended for better quality)
4. Execute the workflow - quantized model automatically saved to models/controlnet/quantized/.
5. Use ControlNet Metadata Viewer to analyze original vs quantized models.

Batch ControlNet Processing

1. Add multiple ControlNet FP8 Quantizer nodes.
2. Select different ControlNet models in each node.
3. Use consistent settings across all nodes.
4. Execute to process multiple models simultaneously.

Features

Advanced ControlNet Quantization

• Precision-aware quantization with tensor calibration and percentile-based scaling
• Two FP8 formats: float8_e4m3fn (recommended) and float8_e5m2
• Quantization strategies: per-tensor (faster) and per-channel (better quality)
• Automatic ComfyUI integration with dropdown model selection
• Smart output management - quantized models saved to models/controlnet/quantized/
• Comprehensive analysis with metadata viewer and detailed statistics
• Fallback logic for compatibility across different PyTorch versions

Technical Capabilities

• ~50% size reduction with maintained quality
• Advanced tensor calibration using statistical analysis
• Activation clipping with outlier handling
• Metadata preservation with quantization information
• Error handling with graceful fallbacks
• Progress tracking and detailed logging

ComfyUI Integration

• Automatic model detection from models/controlnet/ folder
• Dropdown selection - no manual path entry needed
• Auto-generated filenames with format and strategy information
• Organized output in dedicated quantized subfolder
• Seamless workflow integration with existing ControlNet nodes

Requirements

Core Dependencies

• PyTorch 2.0+ (for FP8 support, usually included with ComfyUI)
• safetensors >= 0.3.1
• tqdm >= 4.65.0

Additional Dependencies (for ControlNet nodes)

• tensorflow >= 2.13.0 (optional, for advanced optimization)
• tensorflow-model-optimization >= 0.7.0 (optional)

Hardware

• CUDA-enabled GPU recommended for FP8 operations
• CPU fallback available for compatibility

Troubleshooting

ControlNet Nodes Not Appearing

1. Ensure all dependencies are installed: pip install -r requirements.txt
2. Check that ControlNet models are in ComfyUI/models/controlnet/ folder
3. Restart ComfyUI completely
4. Check console for import errors

"No models found" in Dropdown

1. Place ControlNet models in ComfyUI/models/controlnet/ folder
2. Supported formats: .safetensors, .pth
3. Check file permissions
4. Use manual path input as fallback if needed

Quantization Errors

• "quantile() input tensor must be either float or double dtype": Fixed in latest version
• CUDA out of memory: Use CPU processing or reduce batch size
• FP8 not supported: Upgrade PyTorch to 2.0+ or use CPU fallback

Performance Tips

• For best quality: Use per_channel + activation_clipping + float8_e4m3fn
• For speed: Use per_tensor + reduce calibration_samples
• Memory issues: Process models one at a time

License

MIT