memoise
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.
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) # TRUEis.memoised(f) # FALSEInstallation
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 cachemrunif(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.News
Version 1.1.0
- Caches now hash the function body along with the arguments, to ensure functions with identical arguments use a separate file-system cache. (#38)
- Handle missing arguments in memoised functions for simple cases not using non-standard-evaluation (#19).
memoise()gains acache=argument to specify an external cache. Two types of caches are available,cache_s3()for amazon S3 andcache_filesystem()for a file system cache (#25, @danielecook).
Version 1.0.0
memoise()now signals an error if an already memoised function is used as input (#4, @richierocks).has_cache()function added which returns a boolean depending on if the given call is cached or not (#10, @dkesh).- Memoised functions now have a print method which displays the original function definition, rather than the memoisation code (#15, @jimhester).
- A memoised function now has the same interface as the original function,
if the original function is known when
memoiseis called. (Otherwise, the old behavior is invoked, with a warning.) (#14, @krlmlr) - The enclosing environment of the memoised function is specified explicitly,
defaults to
parent.frame(). is.memoisednow checks if the argument is a function.- Testing infrastructure, full test coverage.
Version 0.2.1
- Update to fix outstanding R CMD check issues.
Version 0.2 (2010-11-11)
New features
- Memoised functions now have an attribute memoised=TRUE, and is.memoised() tests whether a function is memoised. (Contributed by Sietse Brouwer.)
Improvements
- Documentation is now more elaborate, and hopefully more accessible to newcomers. Thanks to Sietse Brouwer for the verbosity.