memoise v1.1.0

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by Jim Hester

Memoisation of Functions

Cache the results of a function so that when you call it again with the same arguments it returns the pre-computed value.

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memoise

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Memoization

If a function is called multiple times with the same input, you can often speed things up by keeping a cache of known answers that it can retrieve. This is called memoisation http://en.wikipedia.org/wiki/Memoization. The memoise package provides a simple syntax

mf <- memoise(f)

to create mf(), a memoised wrapper around f(). You can clear mf's cache with

forget(mf)

and you can test whether a function is memoised with

is.memoised(mf) # TRUE
is.memoised(f)  # FALSE

Installation

devtools::install_github("hadley/memoise")

External Caches

memoise also supports external caching in addition to the default in-memory caches.

  • cache_filesystem() allows caching using files on a local filesystem. You can point this to a shared file such as dropbox or google drive to share caches between systems.
  • cache_s3() allows caching on Amazon S3

AWS S3

Use cache_s3() to cache objects using s3 storage. Requires you to specify a bucket using cache_name. When creating buckets, they must be unique among all s3 users when created.

Sys.setenv("AWS_ACCESS_KEY_ID" = "<access key>",
           "AWS_SECRET_ACCESS_KEY" = "<access secret>")

mrunif <- memoise(runif, cache = cache_s3("<unique bucket name>"))

mrunif(10) # First run, saves cache
mrunif(10) # Loads cache, results should be identical

Filesystem

cache_filesystem can be used for a file system cache. This is useful for preserving the cache between R sessions as well as sharing between systems when using a shared or synced files system such as Dropbox or Google Drive.

fc <- cache_filesystem("~/.cache")
mrunif <- memoise(runif, cache = fc)
mrunif(20) # Results stored in local file

dbc <- cache_filesystem("~/Dropbox/.rcache")
mrunif <- memoise(runif, cache = dbc)
mrunif(20) # Results stored in Dropbox .rcache folder which will be synced between computers.

gdc <- cache_filesystem("~/Google Drive/.rcache")
mrunif <- memoise(runif, cache = gdc)
mrunif(20) # Results stored in Google Drive .rcache folder which will be synced between computers.

Functions in memoise

Name Description
has_cache Test whether a memoised function has been cached for particular arguments.
is.memoised Test whether a function is a memoised copy.
cache_s3 Amazon Web Services S3 Cache
forget Forget past results.
memoise Memoise a function.
timeout Return a new number after a given number of seconds
cache_filesystem Filesystem Cache
cache_memory In Memory Cache
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Details

Encoding UTF-8
URL https://github.com/hadley/memoise
BugReports https://github.com/hadley/memoise/issues
Additional_repositories http://cloudyr.github.io/drat
License MIT + file LICENSE
RoxygenNote 6.0.1
NeedsCompilation no
Packaged 2017-04-20 17:35:47 UTC; jhester
Repository CRAN
Date/Publication 2017-04-21 05:54:22 UTC

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