Deepmind does chat

Read an article this week on Deepmind’s latest research into developing a chat agent (Improving alignment of dialogue agents via targeted human judgements). Lot’s of interesting approaches have been applied to chat but even today, most chat model’s are rife with problems, that include being bigoted, profane, incorrect, etc.

Reinforcement learning vs. deep neural networks in Sparrow Chat

Deepmind specializes in the use of Reinforcement Learning (RL) as applied to master Atari, chess and go games but they have also been known to use dNN’s (deep neural networks) for their AlphaFold and other models. Indeed, Atari and the other game playing work that Deepmind has released has been a hybrid which included a dNNs as well as RL models.

Deepmind’s version of chat is currently called Sparrow and it uses models trained with the help of RL with human feedback (RLHF). RLs are used to create policy models which select actions to be taken in a specific state.

In Sparrow’s case, state is given by the most recent chat input plus the context (prior chat input and replies) of the dialogue up to this time and actions (our guess) is the set of possible replies to that input.

Sparrow is able to generate replies that are 82% mostly true or true and are 69% trustworthy or very trustworthy as rated by the authors of the model. Deepmind’s DPC (Dialogue Prompted Chinchilla, which is Deepmind’s current competitor to GPT-3 NLP transformer) model only managed 63% and 54%, respectively for the same metrics

It should be noted that human feedback was only used to train the two Preference RMs and the one Rule RM. In combination, these RMs provide the reward signal to train the Sparrow RL policy model which drives its chat responses.

Sparrow’s 5 models are built onto of DPC. And the 5 models use a portion of DPC which is frozen (layers not being trained) and a portion which is specifically trained for each of the 5 models (learning enabled layers. The end (output) layers are on top, input layers are after the embedding layer(s). Note, the value function is not a model and is just a calculation based on the RMs used to generate the reward signal for Sparrow’s policy model training.

Rules for Sparrow chats

Notably, Deepmind’s Sparrow model has a separate model specifically trained to determine if a particular chat response is breaking a rule. Deepmind identified 23 rules which their chat model is trained not to break.

Some of these rules include don’t provide financial advice, don’t provide medical advice, don’t pretend it is a human, etc.

In the above chart the RL@8 is the fully trained (if it can ever be considered fully trained) Sparrow chat model. One can see that Sparrow rated against DPC, both using (Google) search or not. For most rules, Sparrow is considerably better than DPC alone.

Another thing that Deepmind did which was interesting was that in training the Rule RM they used adversarial attacks (red teaming) to see if they could cause Sparrow to violate specific rules.

Preference ranking

Deepmind also created (two) Preference RMs (reward models). Sparrow generates a series of (2 or 8) responses for every chat query and the Preference RMs (and Rule RM) are used to select which one is actually sent back to the user. Human feedback was used to train the two Preference RMs

Two Preference RMs were found to perform better than a single Preference RM. The two Preference RMs were trained as follows:

  • One was trained on all Sparrow replies (with and without [Google] search results)
  • One was trained on Sparrow replies without search results.

Sparrow uses search results to provide evidence for some replies. It turns out that some chat questions are fact based questions and for these Sparrow actually uses search results to generate evidence for its chat replies. Sparrow automatically generates search requests and scrapes replies using 500 characters surrounding the snippet returned from the search.

Sparrow uses a re-ranking approach to selecting a response to a chat query. In this case, Sparrow generates a list of responses, 2 (RL@2) or 8 (called RL@8) and then using the two Preference RMs and the single Rule RM ranks them to see which is best and uses the best to reply to the chat user.

Sparrow actually generates two replies for every search query (Google Search API call), probably selecting two top search responses (we guess). So in the RL@8 version of Sparrow these 8 replies are submitted to the two Preference RMs and the Rule RM and are ranked accordion to which is best and then the best one is used to reply to the query.

In the above chart, higher shows that the ranking preference of the various models vs. human preferences and to the right indicates less rule breaking responses. We assume this is with RL@8 Sparrow models. One can see that taking into consideration rule breaking (not violating rules) reduces the preference rankings of Sparrow’s replies. But we would prefer to have no rule breaking so the Sparrow that has both Preference RMs and Rule RM (trained with adversarial training) shows the least amount of rule breaking (~7%) with an almost 70% ranking vs human preferences. The error bars on the points in the chart above show 68% interval around the model responses.

Sparrow in action

It’s somewhat intriguing that Deepmind (with all of Google’s resources) tried to optimize Sparrow for both computation and memory considerations. Almost like they were planning on releasing it on an IoT or phone device.

There’s plenty more to say about what Deepmind has done with Sparrow. The report cited above goes into some detail discussing just where the human input is done, how they tried to control for various considerations when using human input, and what some of the pitfalls were.

I’d certainly like to see this be deployed in the open and available to use as an alternative to Google Search.

You can see more examples of Sparrow chat sessions in Deepmind’s Sparrow chat repository and they include author’s ranking for truth, supportiveness and other metrics.

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