[yorwba]

Backtracking to edit the response is theoretically easily solved by training on a masked language modeling objective instead of an autoregressive one, but using it to actually generate text is a bit expensive because you can't just generate one token at a time and be done, you might have to reevaluate each output token every time another token is changed. So I expect autoregressive generation to remain the default until the recomputation effort can be significantly reduced or hardware advances make the cost bearable.

[YeGoblynQueenne]

>> Backtracking to edit the response is theoretically easily solved by training on a masked language modeling objective instead of an autoregressive one, but using it to actually generate text is a bit expensive because you can't just generate one token at a time and be done, you might have to reevaluate each output token every time another token is changed.

I can't imagine how training on masked tokens can "easily" solve backtracking, even in theory. Do you have some literature I could read on this?

[kastnerkyle]

Discrete diffusion with rewriting can work well. It feels loosely similar to backtracking, if you assume n_steps large enough - need to be able to rewrite any non-provided position though I think (not all setups do this). Downside is the noise in discrete diffusion (in simplest case randomizing over all vocabulary space) is pretty harsh and makes things very difficult practically. Don't have an exact reference on the relationship, but feels similar to backtracking type mechanics in my experience. I found things tend to "lock in" quickly once a good path is found, which feels a lot like pathfinding to me.

Some early personal experiments with adding "prefix-style" context by a cross-attention (in the vein of PerceiverAR) seemed like it really helped things along, which would kind of point to search-like behavior as well.

Probably the closest theory I can think of is orderless NADE, which builds on the "all orders" training of https://arxiv.org/abs/1310.1757 , which in my opinion closely relates to BERT and all kinds of other masked language work. There's a lot of other NAR language work I'm skipping here that may be more relevant...

On discrete diffusion:

Continuous diffusion for categorical data shows some promise "walking the boundary" between discrete and continuous diffusion https://arxiv.org/abs/2211.15089 , personally like this direction a lot.

If you have a pre-made embedding space, SSD-LM is a straightforward method https://arxiv.org/abs/2210.17432

SUNDAE worked well for translation https://arxiv.org/abs/2112.06749 and many other tasks.

My own contribution, SUNMASK, worked reasonably well for symbolic music/small datasets (https://openreview.net/forum?id=GIZlheqznkT), but really struggled with anything text or moderately large vocabulary, maybe due to training/compute/arch issues. Personally think large vocabulary discrete diffusion (thinking of the huge vocabs in modern universal LM work) will continue to be a challenge.

Decoding strategies:

As a general aside, I still don't understand how many of the large generative tools aren't exposing more decoding strategies, or hooks to implement them. Beam search with stochastic/diverse group objectives, per-step temperature/top-k/top-p, hooks for things like COLD decoding https://arxiv.org/abs/2202.11705, minimum Bayes risk https://medium.com/mlearning-ai/mbr-decoding-get-better-resu..., check/correct systems during decode based on simple domain rules and previous outputs, etc.

These kinds of decoding tools have always been a huge boost to model performance for me, and having access to add in these hooks to "big API models" would be really nice... though I guess you would need to limit/lock compute use since a full backtracking search would pretty swiftly crash most systems. Maybe the new "plugins" access from OpenAI will allow some of this.

[mirker]

Backtracking is easily solved with a shortest path algorithm. I don’t see any need for masking if you are simply maximizing likelihood of the entire sequence.