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76 lines
2.4 KiB
Python
76 lines
2.4 KiB
Python
"""Map-reduce chain.
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Splits up a document, sends the smaller parts to the LLM with one prompt,
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then combines the results with another one.
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"""
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from typing import Dict, List
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from pydantic import BaseModel, Extra
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from langchain.chains.base import Chain
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from langchain.chains.llm import LLMChain
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from langchain.llms.base import LLM
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from langchain.prompts.base import BasePromptTemplate
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from langchain.text_splitter import TextSplitter
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class MapReduceChain(Chain, BaseModel):
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"""Map-reduce chain."""
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map_llm: LLMChain
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"""LLM wrapper to use for the map step."""
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reduce_llm: LLMChain
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"""LLM wrapper to use for the reduce step."""
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text_splitter: TextSplitter
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"""Text splitter to use."""
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input_key: str = "input_text" #: :meta private:
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output_key: str = "output_text" #: :meta private:
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@classmethod
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def from_params(
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cls, llm: LLM, prompt: BasePromptTemplate, text_splitter: TextSplitter
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) -> "MapReduceChain":
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"""Construct a map-reduce chain that uses the chain for map and reduce."""
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llm_chain = LLMChain(llm=llm, prompt=prompt)
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return cls(map_llm=llm_chain, reduce_llm=llm_chain, text_splitter=text_splitter)
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class Config:
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"""Configuration for this pydantic object."""
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extra = Extra.forbid
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arbitrary_types_allowed = True
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@property
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def input_keys(self) -> List[str]:
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"""Expect input key.
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:meta private:
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"""
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return [self.input_key]
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@property
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def output_keys(self) -> List[str]:
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"""Return output key.
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:meta private:
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"""
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return [self.output_key]
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def _call(self, inputs: Dict[str, str]) -> Dict[str, str]:
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# Split the larger text into smaller chunks.
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docs = self.text_splitter.split_text(inputs[self.input_key])
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# Now that we have the chunks, we send them to the LLM and track results.
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# This is the "map" part.
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input_list = [{self.map_llm.prompt.input_variables[0]: d} for d in docs]
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summary_results = self.map_llm.apply(input_list)
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summaries = [res[self.map_llm.output_key] for res in summary_results]
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# We then need to combine these individual parts into one.
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# This is the reduce part.
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summary_str = "\n".join(summaries)
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inputs = {self.reduce_llm.prompt.input_variables[0]: summary_str}
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output = self.reduce_llm.predict(**inputs)
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return {self.output_key: output}
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