DiffuSeq: Sequence to Sequence Text Generation with Diffusion Models
Pith reviewed 2026-05-20 06:45 UTC · model grok-4.3
The pith
DiffuSeq adapts diffusion processes to discrete text tokens for conditional sequence generation.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
DiffuSeq is a diffusion model for sequence-to-sequence text generation that adapts continuous diffusion to discrete tokens. Extensive tests on a wide range of Seq2Seq tasks show it matches or exceeds six baselines, including state-of-the-art pre-trained language models, while generating outputs with high diversity. Theoretical analysis further reveals connections between this approach and both autoregressive and non-autoregressive models.
What carries the argument
DiffuSeq, a diffusion model that performs conditional generation by reversing a gradual noising process applied to text token sequences.
If this is right
- Diffusion models become a practical option for conditional text tasks that value output variety alongside accuracy.
- Sequence generation can proceed without the sequential decoding constraints typical of autoregressive models.
- Theoretical links to autoregressive and non-autoregressive families enable hybrid modeling strategies.
- High diversity in generations offers a direct advantage for applications such as dialogue or paraphrasing.
Where Pith is reading between the lines
- The same discretization technique might transfer to other structured discrete domains like source code or molecular sequences.
- Greater output diversity could reduce the need for post-hoc sampling techniques in creative text applications.
- Combining the diffusion backbone with large-scale pre-training might further close any remaining quality gaps.
Load-bearing premise
The continuous diffusion process can be adapted to discrete text tokens in a way that avoids artifacts and preserves strong performance on real conditional generation benchmarks.
What would settle it
If DiffuSeq produces markedly lower quality or less diverse outputs than the autoregressive baselines on standard benchmarks such as machine translation or summarization datasets, the central performance claim would be refuted.
read the original abstract
Recently, diffusion models have emerged as a new paradigm for generative models. Despite the success in domains using continuous signals such as vision and audio, adapting diffusion models to natural language is under-explored due to the discrete nature of texts, especially for conditional generation. We tackle this challenge by proposing DiffuSeq: a diffusion model designed for sequence-to-sequence (Seq2Seq) text generation tasks. Upon extensive evaluation over a wide range of Seq2Seq tasks, we find DiffuSeq achieving comparable or even better performance than six established baselines, including a state-of-the-art model that is based on pre-trained language models. Apart from quality, an intriguing property of DiffuSeq is its high diversity during generation, which is desired in many Seq2Seq tasks. We further include a theoretical analysis revealing the connection between DiffuSeq and autoregressive/non-autoregressive models. Bringing together theoretical analysis and empirical evidence, we demonstrate the great potential of diffusion models in complex conditional language generation tasks. Code is available at \url{https://github.com/Shark-NLP/DiffuSeq}
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper introduces DiffuSeq, a diffusion model for conditional sequence-to-sequence text generation that performs the diffusion process in continuous embedding space before mapping back to discrete tokens via rounding or argmax. It reports empirical results across multiple Seq2Seq tasks showing performance comparable to or better than six baselines (including a pre-trained LM-based SOTA), highlights high generation diversity as an advantage, and provides a theoretical analysis connecting the approach to autoregressive and non-autoregressive models. Code is released publicly.
Significance. If the central empirical claims hold after addressing discretization effects, the work would establish diffusion models as a viable alternative paradigm for conditional text generation, with strengths in diversity and a reproducible implementation that enables further exploration. The theoretical connection to AR/NAR models is a useful framing, though its independence from the empirical results would benefit from clearer separation.
major comments (2)
- [§3.2 and Algorithm 1] §3.2 and Algorithm 1: the reverse diffusion process maps continuous embeddings back to discrete tokens via argmax/rounding at each step; without reported analysis of embedding-to-token distances or ablations showing that this mapping does not systematically degrade conditional generation quality, it is unclear whether the performance gains over AR/NAR baselines are attributable to diffusion or to artifacts of the discretization procedure.
- [§4] §4 (experimental results): the claim of comparable or superior performance to a pre-trained LM baseline requires explicit confirmation that data splits, hyperparameter tuning, and evaluation protocols match those of the baselines exactly; any post-hoc adjustments could affect the central performance comparison.
minor comments (2)
- [§3] Notation for the forward and reverse processes could be aligned more consistently with standard diffusion literature to aid readability.
- [Figures in §4] Figure captions and axis labels in the diversity and quality plots should explicitly state the metrics and number of samples used.
Simulated Author's Rebuttal
We thank the referee for the constructive comments on our manuscript. We address each major comment point by point below and indicate the revisions we will make.
read point-by-point responses
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Referee: [§3.2 and Algorithm 1] §3.2 and Algorithm 1: the reverse diffusion process maps continuous embeddings back to discrete tokens via argmax/rounding at each step; without reported analysis of embedding-to-token distances or ablations showing that this mapping does not systematically degrade conditional generation quality, it is unclear whether the performance gains over AR/NAR baselines are attributable to diffusion or to artifacts of the discretization procedure.
Authors: We appreciate the referee's emphasis on the discretization step. Section 3.2 and Algorithm 1 describe the forward diffusion in continuous embedding space followed by rounding or argmax in the reverse process. The manuscript reports strong empirical results across tasks, but we agree that explicit analysis of embedding-to-token distances and ablations isolating the discretization effect would better attribute performance to the diffusion process. We will add these analyses and ablations to the revised manuscript. revision: yes
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Referee: [§4] §4 (experimental results): the claim of comparable or superior performance to a pre-trained LM baseline requires explicit confirmation that data splits, hyperparameter tuning, and evaluation protocols match those of the baselines exactly; any post-hoc adjustments could affect the central performance comparison.
Authors: We confirm that the experiments used identical data splits, hyperparameter tuning ranges, and evaluation metrics as the original baseline papers, including the pre-trained LM system. To eliminate any ambiguity, we will expand Section 4 with an explicit subsection documenting these matching protocols and citing the exact settings from each baseline. revision: yes
Circularity Check
No significant circularity: empirical results and theoretical connections remain independent of fitted inputs.
full rationale
The paper grounds its claims in external Seq2Seq benchmark evaluations against six baselines (including pre-trained models) and presents a separate theoretical analysis connecting DiffuSeq to AR/NAR models. No derivation, equation, or self-citation reduces the reported performance or diversity properties to quantities defined by the same fitted parameters or by construction. The continuous-to-discrete embedding adaptation is a methodological choice whose effects are assessed empirically rather than tautologically assumed. This is the common case of a self-contained paper whose central results do not collapse into input definitions.
Axiom & Free-Parameter Ledger
Forward citations
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13 Published as a conference paper at ICLR 2023 A O BJECTIVE DERIVATIONS OF DIFFU SEQ The diffusion model is well-known as its ability to achieve the trade-off between flexibility and tractability of the models’ probability distributions, compared with GAN, V AE and Flow-based models. Following Ho et al. (2020); Nichol & Dhariwal (2021); Song et al. (2020)...
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learn the conditional probability given independent assumption for fast inference: pfully-NAR(wy 1:n|wx) = ∏ i=1,...,n p(wy i|wx). (19) To make a better analogy to AR and NAR models, we use a lossless way to formulate iterative NAR models (Gu et al., 2019; Ghazvininejad et al.,
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This gap is mainly responsible for the performance drop from AR to NAR models
shows that there is a gap called conditional total correlation between AR and fully-NAR learning paradigms, because of the lossy decomposition of NAR mod- els. This gap is mainly responsible for the performance drop from AR to NAR models. However, when comparing iter-NAR, Eq. (20), with AR models, they both can be factorized into an initial prediction ter...
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16 Published as a conference paper at ICLR 2023
C F ROM DIFFU SEQ TO ITERATIVE NAR AND DIFFUSION MODELS From D IFFU SEQ to Iterative NAR We show how to derive D IFFU SEQ to iterative non- autoregressive model on discrete space. 16 Published as a conference paper at ICLR 2023 ... ...... ... ... AR Fully-NAR Iter-NAR DiffuSeq ...... ...... ...... ...... ...... ...... ... ... ... ...... ... ... ... ... .....
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[16]
For DIFFU SEQ, we choose trained models at different training steps to achieve different trade-off points. For other baselines, there is no explicit factor to control the diversity generation, so we leave them as single points in the figure. 4Including top-p sampling, temperature, diversity beam search (DBS) and etc. Implement using Hugging- Face Transform...
work page 2023
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