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UL2

GoogleOpen WeightsPending Human Review

UL2 is a research and open-weight text-to-text language model using a mixture-of-denoisers pretraining objective. It combines regular span corruption, sequential denoising, and extreme corruption to unify language-understanding and generation tasks. The released 20B model uses a T5-style encoder-decoder and mode tokens that select the desired learning behavior. It became a foundation for instruction tuning and chain-of-thought research.

2022-05-10
20B
T5-style encoder-decoder Transformer trained with a mixture-of-denoisers objective
Apache-2.0

Specifications

Parameters
20B
Architecture
T5-style encoder-decoder Transformer trained with a mixture-of-denoisers objective
License
Apache-2.0
Context Window
512 tokens
Type
text
Modalities
text

Benchmark Scores

Advanced Specifications

Model Family
UL2
API Access
Not Available
Chat Interface
Not Available
Hardware Support
GPUTPUCPU

Capabilities & Limitations

Capabilities
text-to-text generationquestion answeringsummarizationreasoning
Known Limitations
The original checkpoint was trained with 512-token input and target sequences.Mode-token handling and task prompting affect quality.
Notable Use Cases
NLP researchtask fine-tuningencoder-decoder experimentation

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