uninas 1.3.0

model <> string conversions with json

uninas

This repository provides a framework for creating model instances from the UNINas search space and exploring (walking through) that space programmatically. It supports JSON-defined architectures, conversion between JSON and model objects, and search workflows over valid configurations.

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Model JSON Format

The model description JSON defines the structural and hyperparameter configuration of a model architecture within the UniNAS search space.

Reference papers:

• UniNAS search space — https://arxiv.org/abs/2510.06035
• CoAtNet — https://arxiv.org/abs/2106.04803

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Example — CoAtNet-like Configuration

{
  "img_size": 224,
  "num_classes": 1000,
  "drop_rate": 0.0,
  "embed_dim": [96, 192, 384, 768],
  "depths": [2, 3, 5, 2],
  "model_str": "[[\"E\", \"E\"], [\"E\", \"E\", \"E\"], [\"T\", \"T\", \"T\", \"T\", \"T\"], [\"T\", \"T\"]]",
  "stem_width": [32, 64]
}

Field Meaning

The following fields define standard architectural parameters:

• img_size — input image resolution (square)
• num_classes — number of output classes
• drop_rate — dropout rate
• embed_dim — per-stage embedding/channel dimensions
• depths — number of blocks per stage
• stem_width — channel widths of stem layers

The model_str field encodes the stage-by-stage, block-by-block layout as a stringified nested array.

In the example above "[[\"E\", \"E\"], [\"E\", \"E\", \"E\"], [\"T\", \"T\", \"T\", \"T\", \"T\"], [\"T\", \"T\"]]" stands for:

• Stage 1: 2 EfficientNet-like blocks
• Stage 2: 3 EfficientNet-like blocks
• Stage 3: 5 Transformer-like blocks
• Stage 4: 2 Transformer-like blocks

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Block Type Codes in model_str

Each character represents a block type:

• T — Transformer block
• E — EfficientNet-like block
• R — ResNet-like block

Moreover, instead of single characters, we can specify a fully custom block from the UniNAS search space via a structured block definition: {"subblock1": XXX, "subblock2": YYY}, where XXX and YYY are recursive graph representations produced via each Node’s .to_string() method.

Additional examples can be found in examples/

• model_coatnet.json -- CoAtNet,
• model_efficientnet.json -- EfficientNet,
• model_resnet.json -- ResNet,
• model_transformer.json -- Transformer
• model_example.json -- Custom model

Code

json-to-model (and back) is performed via

from uninas import UNIModel, UNIModelCfg
import json

# Json to model
model_path_in = 'examples/model_example.json'
model_path_out = 'examples/model_example_out.json'
with open(model_path_in, "r") as f:
    model_string = f.read()
model_cfg = UNIModelCfg.from_string(model_string)
model = UNIModel(model_cfg)

# Model to json
model_str = model.to_string()
with open(model_path_out, "w") as f:
    json.dump(json.loads(model_str), f, indent=2)

You can load an initial model from JSON, perform a search in the UniNAS search space with specific search parameters, and save the resulting model configuration in examples/train.py:

python examples/test.py --model-init <MODEL_JSON_PATH>