Here's how it summarizes big documents:

Map Reduce

This method involves an initial prompt on each chunk of data (for summarization tasks, this could be a summary of that chunk; for question-answering tasks, it could be an answer based solely on that chunk). Then a different prompt is run to combine all the initial outputs. This is implemented in the LangChain as the MapReduceDocumentsChain.

Pros: Can scale to larger documents (and more documents) than StuffDocumentsChain. The calls to the LLM on individual documents are independent and can therefore be parallelized.

Cons: Requires many more calls to the LLM than StuffDocumentsChain. Loses some information during the final combining call.

Here's how a separate Wikipedia agent chain works:

Agents use an LLM to determine which actions to take and in what order. An action can either be using a tool and observing its output, or returning to the user.

It uses agent based modeling, basically asking itself a series of questions until it gets to the right answer. sorta looks like wikipedia racing.

Here's a sample LangChain agent based React-Act modeling on Wikipedia/TMDB:

Log

Entering new AgentExecutor chain...

Thought 1: I need to search for a romantic comedy film about a Senatorial candidate falling for a hotel maid, thinking she is a socialite, when he sees her trying on a wealthy woman's dress.

Action 1: Search[romantic comedy film Senatorial candidate hotel maid socialite wealthy woman's dress]

Observation 1: Maid in Manhattan is a 2002 American romantic comedy-drama film directed by Wayne Wang and based on a story by John Hughes, who is credited using a pseudonym. It stars Jennifer Lopez, Ralph Fiennes, and Natasha Richardson. In the film, a hotel maid and a high-profile politician fall in love. The film was released on December 13, 2002, by Columbia Pictures and was a box office success, grossing $154 million against its $55 million budget, while receiving mixed reviews.

Thought 2: Maid in Manhattan is a romantic comedy film about a Senatorial candidate falling for a hotel maid, thinking she is a socialite, when he sees her trying on a wealthy woman's dress.

Action 2: Finish[Maid in Manhattan]

From: https://langchain.readthedocs.io/en/latest/modules/agents/getting_started.html

Here's the sample notebook for the wikipedia agent: https://langchain.readthedocs.io/en/latest/modules/agents/implementations/react.html