archit 2026.1.1

ArchIt: A framework for base-and-head language models, and toolkit for converting in-place modifications of PyTorch objects into class code.

ArchIt: Automatic PyTorch architectures

ArchIt helps you rewrite PyTorch code for base models augmented at runtime, and lets you put heads on top of models without having to write dedicated task classes again and again.

archit.declaration: Convert a PyTorch instance into PyTorch architecture classes.

Recursively rewrite a class hierarchy (i.e. generate Python code of PyTorch architectures) so that in-place modifications are now defined explicitly.

As an example of this: I'm involved in two projects where I replace the embedding matrix of a RobertaForMaskedLM by a new class. If I want to load a checkpoint of that model, I need to write a new class definition for the RobertaEmbeddings that uses my replacement of the Embedding, a new RobertaModel using the new embeddings, and a new RobertaForMaskedLM using that new model. ArchIt writes that code for you.

archit.instantiation: Add heads to a base model, without needing to write YourModelForThatTask classes

Why in the heavens do we need separate classes for RobertaForTokenClassification and DebertaForTokenclassification? The base model encodes tokens into embeddings, and the head, which only cares about the resulting embeddings, converts them to logits. Separation of concerns. There is no need to rewrite "model-with-head" classes over and over again for each model augmentation.

Installation

pip install "archit @ git+https://github.com/bauwenst/ArchIt"

Usage

Minimal working example to show what ArchIt does:

from transformers import RobertaForMaskedLM
import torch

class CoolNewEmbeddingMatrix(torch.nn.Module):
    def forward(self, input_ids):
        pass

model_with_head = RobertaForMaskedLM.from_pretrained("roberta-base")
model_with_head.roberta.embeddings.word_embeddings = CoolNewEmbeddingMatrix()
# ^--- This works, but there is no class definition declaring word_embeddings as a CoolNewEmbeddingMatrix.


from archit import printDifference
printDifference(model_with_head, RobertaForMaskedLM)  # Outputs Python code for 3 new classes.