LU memoization

The least-used memoization strategy (sometimes called "Least Frequently Used") is a variant of LRU that evicts items that are used least frequently once its threshold has been exceeded.

In simple terms, the LU cache will remove the element in the cache that has been accessed the least, regardless of time.

General use

To create a core.memoize LU-backed memoized function use the clojure.core.memoize/lu function with an optional seed map or a :lu/threshold parameter:

(memo/lu function <seed> <:lu/threshold number>)

Example code is as follows:

(ns your.lib
  (:require [clojure.core.memoize :as memo]))

(def memoized-fun
  (memo/lu identity {} :lu/threshold 3))

The default :lu/threshold value is 32 and refers to the number of elements in the cache required before the LU logic is applied.

Please read the clojure.core.cache information regarding LU caches for more detailed information, use cases and usage patterns.

As always, you should measure your system's characteristics to determine the best eviction strategy for your purposes.