Beam search is a memory-restricted version of breadth-first search.

Beam search commonly appears in machine translation or other literature where sequence-to-sequence learning is common. In this domain, beam search allows the neural network to consider many candidate responses instead of selecting the highest-scoring token at each step.

Google’s blog post announcing SyntaxNet explains the advantages of beam search for sequence-to-sequence learning in greater detail: > At each point in processing many decisions may be possible—due to ambiguity—and a neural network gives scores for competing decisions based on their plausibility. For this reason, it is very important to use beam search in the model. Instead of simply taking the first-best decision at each point, multiple partial hypotheses are kept at each step, with hypotheses only being discarded when there are several other higher-ranked hypotheses under consideration.