Class: RerankerRuby::Ensemble

Inherits:
Base
  • Object
show all
Defined in:
lib/reranker_ruby/ensemble.rb

Overview

Combines results from multiple rerankers using weighted score aggregation.

Usage:

ensemble = RerankerRuby::Ensemble.new(
rerankers: [cohere_reranker, jina_reranker],
weights: [0.6, 0.4],
normalize: :min_max
)
results = ensemble.rerank(query, documents, top_k: 5)

Instance Method Summary collapse

Constructor Details

#initialize(rerankers:, weights: nil, normalize: :min_max, **options) ⇒ Ensemble

Returns a new instance of Ensemble.

Parameters:

  • rerankers (Array<Base>) —

    list of reranker instances

  • weights (Array<Float>, nil) (defaults to: nil) —

    weights for each reranker (default: equal)

  • normalize (Symbol) (defaults to: :min_max) —

    normalization strategy (:min_max, :softmax, :sigmoid, or :none)



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# File 'lib/reranker_ruby/ensemble.rb', line 18

def initialize(rerankers:, weights: nil, normalize: :min_max, **options)
  super(**options)
  @rerankers = rerankers
  @weights = weights || Array.new(rerankers.length, 1.0 / rerankers.length)
  @normalize = normalize

  if @weights.length != @rerankers.length
    raise ArgumentError, "weights length (#{@weights.length}) must match rerankers length (#{@rerankers.length})"
  end
end

Instance Method Details

#rerank(query, documents, top_k: 10) ⇒ Object 



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# File 'lib/reranker_ruby/ensemble.rb', line 29

def rerank(query, documents, top_k: 10)
  validate_inputs!(query, documents, top_k)
  with_cache(query, documents, top_k: top_k) do
    texts = extract_texts(documents)

    # Collect and normalize results from each reranker
    all_results = @rerankers.map do |reranker|
      raw = reranker.rerank(query, documents, top_k: texts.length)
      normalize_results(raw)
    end

    # Aggregate scores by original document index
    aggregated = Hash.new(0.0)
    all_results.each_with_index do |results, reranker_idx|
      weight = @weights[reranker_idx]
      results.each do |result|
        aggregated[result.index] += result.score * weight
      end
    end

    # Build final results sorted by aggregated score
    aggregated.map do |idx, score|
      Result.new(
        text: texts[idx],
        score: score,
        index: idx,
        metadata: extract_metadata(documents[idx])
      )
    end.sort.first(top_k)
  end
end