Caching Computations
The cacher package for R evaluates code written in files and stores intermediate results in a key-value database.
R expressions are given a SHA-1 hash value so that changes can be tracked and code reevaluated if necessary.
Others can ‘clone’ analysis and evaluate subsets of code or inspect data objects.
TO use as an author, the package parses the source file and creates the necessary cache directories and sub-directories.
It then cycles through each expression in the source file and:
- If an expression has never been evaluated, evaluate and store in the cache DB.
- If a cache result exists, lazy-load the results from the cache DB.
- If an expression does not create any R objects, add the expression to a list of expressions where evaluation needs to be forced.
- Write out metadata for this expression.
The cachepackage() function creates a cacher package storing:
- Source file
- Cached data objects
- Metadata
Package file is zipped and can be distributed, readers can unzip the file and immediately investigate its contents.
Running Code
The runcode() function executes code in the source file. By default, expressions that result in an object being created are not run. Expressions not results in objects are evaluated.
The checkcode() function evaluates all expressions from scratch - no lazy loading. Results are compared against the stored results to see if they are the same.