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Informed search

As explained in Grokking AI Algorithms, Second Edition

Informed search is a search technique that uses domain knowledge or heuristic guidance to direct exploration toward promising solutions.

Informed search uses knowledge about a problem to guide exploration toward promising solutions instead of searching blindly. That knowledge is expressed through heuristics: rules of thumb that evaluate how promising a state appears. A heuristic is an educated guess, not a guaranteed truth. section 3.1 section 3.2

A guided search typically works by:

  • Representing possible situations as states or branches that can be explored. section 3.1
  • Scoring or ranking states with a heuristic based on problem-specific knowledge. section 3.1
  • Choosing an informed search algorithm suited to the problem, such as greedy search or A*. section 3.2

Choosing a useful route heuristic

For GPS routing, a useful heuristic might favor shorter travel time, less traffic, lower tolls, or better road conditions. Straight-line distance alone can be misleading because roads rarely follow a direct line between destinations. section 3.1

From exhaustive comparison to guided matching

Checking whether an uploaded audio clip appears in a copyrighted library could compare every time slice with every stored clip. Frequency-based comparisons provide problem-specific information that can guide a more focused search. section 3.1

Common applications include:

  • Finding paths for autonomous game characters. section 3.5
  • Generating and decoding text by looking ahead across multiple possible word sequences. section 3.5
  • Routing traffic through telecommunications networks represented as graphs. section 3.5
  • Solving single-player games and puzzles by exploring decision trees. section 3.5
Figure 3.1 Comparison of two audio clips using frequency distribution
03_01

Compare audio clips through their frequency distributions when considering guided audio matching. section 3.1

How Grokking AI Algorithms, Second Edition covers it

How deep it goes
Defines heuristics and names greedy search and A*, but stops short of detailed algorithm mechanics or proofs.
Examples
Uses pizza preferences, GPS routing, audio matching, game characters, language generation, networks, and puzzles.
What it assumes
Assumes familiarity with breadth-first and depth-first search while introducing heuristics through everyday examples.
What you can do after
Evaluate when domain knowledge can guide search and select a suitable heuristic-search approach.
How it connects
Connects heuristics with breadth-first search, depth-first search, greedy search, A*, beam search, and graph search.

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This explainer was generated by Manning's knowledge graph from the text of Grokking AI Algorithms, Second Edition. The section links point to the parts of the book it draws on.