Train for the Worst, Plan for the Best: Understanding Token Ordering in Masked Diffusions

Fuente: arXiv
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Hauptverfasser: Kim, Jaeyeon, Shah, Kulin, Kontonis, Vasilis, Kakade, Sham, Chen, Sitan
Format: Preprint
Veröffentlicht: 2025
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author Kim, Jaeyeon
Shah, Kulin
Kontonis, Vasilis
Kakade, Sham
Chen, Sitan
author_facet Kim, Jaeyeon
Shah, Kulin
Kontonis, Vasilis
Kakade, Sham
Chen, Sitan
contents In recent years, masked diffusion models (MDMs) have emerged as a promising alternative approach for generative modeling over discrete domains. Compared to autoregressive models (ARMs), MDMs trade off complexity at training time with flexibility at inference time. At training time, they must learn to solve an exponentially large number of infilling problems, but at inference time, they can decode tokens in essentially arbitrary order. In this work, we closely examine these two competing effects. On the training front, we theoretically and empirically demonstrate that MDMs indeed train on computationally intractable subproblems compared to their autoregressive counterparts. On the inference front, we show that a suitable strategy for adaptively choosing the token decoding order significantly enhances the capabilities of MDMs, allowing them to sidestep hard subproblems. On logic puzzles like Sudoku, we show that adaptive inference can boost solving accuracy in pretrained MDMs from $<7$% to $\approx 90$%, even outperforming ARMs with $7\times$ as many parameters and that were explicitly trained via teacher forcing to learn the right order of decoding.
format Preprint
id arxiv_https___arxiv_org_abs_2502_06768
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Train for the Worst, Plan for the Best: Understanding Token Ordering in Masked Diffusions
Kim, Jaeyeon
Shah, Kulin
Kontonis, Vasilis
Kakade, Sham
Chen, Sitan
Machine Learning
In recent years, masked diffusion models (MDMs) have emerged as a promising alternative approach for generative modeling over discrete domains. Compared to autoregressive models (ARMs), MDMs trade off complexity at training time with flexibility at inference time. At training time, they must learn to solve an exponentially large number of infilling problems, but at inference time, they can decode tokens in essentially arbitrary order. In this work, we closely examine these two competing effects. On the training front, we theoretically and empirically demonstrate that MDMs indeed train on computationally intractable subproblems compared to their autoregressive counterparts. On the inference front, we show that a suitable strategy for adaptively choosing the token decoding order significantly enhances the capabilities of MDMs, allowing them to sidestep hard subproblems. On logic puzzles like Sudoku, we show that adaptive inference can boost solving accuracy in pretrained MDMs from $<7$% to $\approx 90$%, even outperforming ARMs with $7\times$ as many parameters and that were explicitly trained via teacher forcing to learn the right order of decoding.
title Train for the Worst, Plan for the Best: Understanding Token Ordering in Masked Diffusions
topic Machine Learning
url https://arxiv.org/abs/2502.06768