Cache function results — lru

Decorators that remember a function's results, keyed on the matched arguments (including defaults).

Usage

lru_cache(f, maxsize = 1024 * 1024^2)

cache(f)

disk_cache(f, dir, maxsize = 1024 * 1024^2, format = c("rds", "qs2"))

Arguments

f: The function to decorate. Usually supplied by %@% rather than directly.
maxsize: Maximum cache size in bytes. Defaults to 1 GiB.
format: File format for disk_cache(): "rds" (the default) or "qs2", which needs the qs2 package.
dir: Directory for disk_cache() to keep its files in. It is created if needed. There is no default, so persistence is always a choice.

Value

A decorator.

Details

lru_cache() evicts the least recently used entries when the cache is full. Port of Python's functools.lru_cache.
cache() never evicts. Port of Python's functools.cache.
disk_cache() stores results as files in dir, so they survive the R session and can be shared between sessions. Like joblib.Memory.cache.

Entries are keyed on the function's formals and body as well as its arguments, so editing the function invalidates them. Changes to anything it calls do not. disk_cache() saves results with saveRDS(), or with the qs2 package when format = "qs2", which is usually faster and smaller for large objects. Neither round-trips environments or external pointers. Files from the two formats are not shared, so changing format for an existing dir starts with an empty cache.

Call lru_cache(maxsize) to build a decorator, then apply it with %@% or by calling it on a function. cache takes no parameters, so it is applied directly.

Examples

slow_square <- lru_cache() %@% function(x) {
  Sys.sleep(0.1)
  x^2
}
slow_square(4) # slow
#> [1] 16
slow_square(4) # cached
#> [1] 16

slow_cube <- cache %@% function(x) {
  Sys.sleep(0.1)
  x^3
}
slow_cube(2) # slow
#> [1] 8
slow_cube(2) # cached
#> [1] 8

dir <- tempfile("cache")
slow_cube <- disk_cache(dir) %@% function(x) {
  Sys.sleep(0.1)
  x^3
}
slow_cube(2) # slow, and saved to `dir`
#> [1] 8
slow_cube(2) # cached
#> [1] 8