Explicit memory

As explained in Optimization Algorithms: AI techniques for design, planning, and control problems

Explicit memory is a search mechanism that records previously visited moves or solutions.

Explicit memory records moves visited during a search, giving tabu search a history that memoryless local search lacks. It helps prevent cycling and guides future choices. section 6.2.1

A simple tabu search uses two adaptive memory mechanisms:

• Recency-based or short-term memory tracks recently visited moves and prevents their immediate reuse. section 6.2.1
• Frequency-based or long-term memory counts how often moves occur and penalizes frequently used or less promising moves. section 6.2.1

Tabu structure for a four-city TSP

A tabu structure can record remaining tabu iterations for recently used moves alongside frequency counts for moves used throughout the search. section 6.2.1

Figure 6.5 Tabu structure for the 4-city TSP. The numbers in recency-based memory represent the number of iterations remaining for tabu-active moves; the numbers in long-term memory represent the frequency count of using the move.

Visualizes recency-based tabu status and long-term frequency counts in a four-city traveling-salesperson search. section 6.2.1

How Optimization Algorithms: AI techniques for design, planning, and control problems covers it

How deep it goes

Defines recency and frequency mechanisms, but stops short of pseudocode, parameter guidance, or implementation detail.

Examples

Uses a four-city traveling-salesperson problem and memory analogies involving working memory and customer orders.

What you can do after

Apply it via tabu search to prevent recent revisits and penalize frequently used, less promising moves.

How it connects

Connects local search with tabu search, short-term memory, and long-term memory.

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Related concepts

• tabu searchused by · Tabu search is a memory-guided local search technique that restricts recently used moves or solutions to discourage cycling and escape local optima.
• memorykind of · Memory is a storage resource or mechanism that retains data or computational state for access during computation or later use.

This explainer was generated by Manning's knowledge graph from the text of Optimization Algorithms: AI techniques for design, planning, and control problems. The section links point to the parts of the book it draws on.