Code Pretraining Models

This repo contains code pretraining models in the CodeBERT series from Microsoft, including six models as of June 2023.

• CodeBERT (EMNLP 2020)
• GraphCodeBERT (ICLR 2021)
• UniXcoder (ACL 2022)
• CodeReviewer (ESEC/FSE 2022)
• CodeExecutor (ACL 2023)
• LongCoder (ICML 2023)

CodeBERT

This repo provides the code for reproducing the experiments in CodeBERT: A Pre-Trained Model for Programming and Natural Languages. CodeBERT is a pre-trained model for programming language, which is a multi-programming-lingual model pre-trained on NL-PL pairs in 6 programming languages (Python, Java, JavaScript, PHP, Ruby, Go).

Dependency

• pip install torch
• pip install transformers

Quick Tour

We use huggingface/transformers framework to train the model. You can use our model like the pre-trained Roberta base. Now, We give an example on how to load the model.

import torch
from transformers import RobertaTokenizer, RobertaConfig, RobertaModel

device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
tokenizer = RobertaTokenizer.from_pretrained("microsoft/codebert-base")
model = RobertaModel.from_pretrained("microsoft/codebert-base")
model.to(device)

NL-PL Embeddings

Here, we give an example to obtain embedding from CodeBERT.

>>> from transformers import AutoTokenizer, AutoModel
>>> import torch
>>> tokenizer = AutoTokenizer.from_pretrained("microsoft/codebert-base")
>>> model = AutoModel.from_pretrained("microsoft/codebert-base")
>>> nl_tokens=tokenizer.tokenize("return maximum value")
['return', 'Ġmaximum', 'Ġvalue']
>>> code_tokens=tokenizer.tokenize("def max(a,b): if a>b: return a else return b")
['def', 'Ġmax', '(', 'a', ',', 'b', '):', 'Ġif', 'Ġa', '>', 'b', ':', 'Ġreturn', 'Ġa', 'Ġelse', 'Ġreturn', 'Ġb']
>>> tokens=[tokenizer.cls_token]+nl_tokens+[tokenizer.sep_token]+code_tokens+[tokenizer.eos_token]
['<s>', 'return', 'Ġmaximum', 'Ġvalue', '</s>', 'def', 'Ġmax', '(', 'a', ',', 'b', '):', 'Ġif', 'Ġa', '>', 'b', ':', 'Ġreturn', 'Ġa', 'Ġelse', 'Ġreturn', 'Ġb', '</s>']
>>> tokens_ids=tokenizer.convert_tokens_to_ids(tokens)
[0, 30921, 4532, 923, 2, 9232, 19220, 1640, 102, 6, 428, 3256, 114, 10, 15698, 428, 35, 671, 10, 1493, 671, 741, 2]
>>> context_embeddings=model(torch.tensor(tokens_ids)[None,:])[0]
torch.Size([1, 23, 768])
tensor([[-0.1423,  0.3766,  0.0443,  ..., -0.2513, -0.3099,  0.3183],
        [-0.5739,  0.1333,  0.2314,  ..., -0.1240, -0.1219,  0.2033],
        [-0.1579,  0.1335,  0.0291,  ...,  0.2340, -0.8801,  0.6216],
        ...,
        [-0.4042,  0.2284,  0.5241,  ..., -0.2046, -0.2419,  0.7031],
        [-0.3894,  0.4603,  0.4797,  ..., -0.3335, -0.6049,  0.4730],
        [-0.1433,  0.3785,  0.0450,  ..., -0.2527, -0.3121,  0.3207]],
       grad_fn=<SelectBackward>)

Probing

As stated in the paper, CodeBERT is not suitable for mask prediction task, while CodeBERT (MLM) is suitable for mask prediction task.

We give an example on how to use CodeBERT(MLM) for mask prediction task.

from transformers import RobertaConfig, RobertaTokenizer, RobertaForMaskedLM, pipeline

model = RobertaForMaskedLM.from_pretrained("microsoft/codebert-base-mlm")
tokenizer = RobertaTokenizer.from_pretrained("microsoft/codebert-base-mlm")

CODE = "if (x is not None) <mask> (x>1)"
fill_mask = pipeline('fill-mask', model=model, tokenizer=tokenizer)

outputs = fill_mask(CODE)
print(outputs)

Results

'and', 'or', 'if', 'then', 'AND'

The detailed outputs are as follows:

{'sequence': '<s> if (x is not None) and (x>1)</s>', 'score': 0.6049249172210693, 'token': 8}
{'sequence': '<s> if (x is not None) or (x>1)</s>', 'score': 0.30680200457572937, 'token': 50}
{'sequence': '<s> if (x is not None) if (x>1)</s>', 'score': 0.02133703976869583, 'token': 114}
{'sequence': '<s> if (x is not None) then (x>1)</s>', 'score': 0.018607674166560173, 'token': 172}
{'sequence': '<s> if (x is not None) A