Enable Caching of the Function Results with the use of Archivist

cache function stores all results of function calls in local Repository. All results are stored together with md5 hashes of the function calls. If a function is called with the same arguments, then its results can be loaded from the repository.

One may specify expiration date for live objects. It may be useful for objects that can be changed externally (like queries to database).

cache(cacheRepo = NULL, FUN, ..., notOlderThan = NULL)

Arguments

cacheRepo	A repository used for storing cached objects.
FUN	A function to be called.
...	Arguments of FUN function .
notOlderThan	load an artifact from the database only if it was created after notOlderThan.

Value

Result of the function call with additional attributes: tags - md5 hash of the function call and call - "".

Details

cache function stores all results of function calls in local Repository specified by the cacheRepo argument. The md5 hash of FUN and it's arguments is added as a Tag to the repository. This Tag has the following structure "cacheId:md5hash". Note that cache is a good solution if objects are not that big but calculations are time consuming (see Examples). If objects are big and calculations are easy, then disk input-output operations may take more time than calculations itself.

Contact

Bug reports and feature requests can be sent to https://github.com/pbiecek/archivist/issues

References

Biecek P and Kosinski M (2017). "archivist: An R Package for Managing, Recording and Restoring Data Analysis Results." _Journal of Statistical Software_, *82*(11), pp. 1-28. doi: 10.18637/jss.v082.i11 (URL: http://doi.org/10.18637/jss.v082.i11). URL https://github.com/pbiecek/archivist

See also

For more detailed information, check the archivist package Use Cases.

Other archivist: Repository, Tags, %a%, addHooksToPrint, addTagsRepo, aformat, ahistory, alink, aoptions, archivist-package, areadLocal, aread, asearchLocal, asearch, asession, atrace, copyLocalRepo, createLocalRepo, createMDGallery, deleteLocalRepo, getRemoteHook, getTagsLocal, loadFromLocalRepo, md5hash, removeTagsRepo, restoreLibs, rmFromLocalRepo, saveToLocalRepo, searchInLocalRepo, setLocalRepo, shinySearchInLocalRepo, showLocalRepo, splitTagsLocal, summaryLocalRepo, zipLocalRepo

Examples

# NOT RUN {
# objects preparation
library("lubridate")
cacheRepo <- tempfile()
createLocalRepo( cacheRepo )

## Example 1:
# cache is useful when objects used by FUN are not that big but calculations
# are time-comsuming. Take a look at this example:
fun <- function(n) {replicate(n, summary(lm(Sepal.Length~Species, iris))$r.squared)}

# let's check time of two evaluations of cache function
system.time( res <- cache(cacheRepo, fun, 1000) )
system.time( res <- cache(cacheRepo, fun, 1000) )
# The second call is much faster. Why is it so? Because the result of fun
# function evaluation has been stored in local cacheRepo during the first evaluation
# of cache. In the second call of cache we are simply loading the result of fun
# from local cacheRepo Repository.

## Example 2:
testFun <- function(x) {cat(x);x}

# testFun will be executed and saved to cacheRepo
tmp <- cache(cacheRepo, testFun, "Say hallo!")

# testFun execution will be loaded from repository
tmp <- cache(cacheRepo, testFun, "Say hallo!")

# testFun will be executed once again as it fails with expiration date. It will
# be saved to cacheRepo.
tmp <- cache(cacheRepo, testFun, "Say hallo!", notOlderThan = now())

# testFun execution will be loaded from repository as it
# passes with expiration date [within hour]
tmp <- cache(cacheRepo, testFun, "Say hallo!", notOlderThan = now() - hours(1))

deleteLocalRepo( cacheRepo, TRUE)
rm( cacheRepo )

# }