evalWithMemoization: Evaluates an R expression with memoization

In R.cache: Fast and Light-Weight Caching (Memoization) of Objects and Results to Speed Up Computations

Evaluates an R expression with memoization

Description

Evaluates an R expression with memoization such that the same objects are assigned to the current environment and the same result is returned, if any.

Usage

evalWithMemoization(expr, key=NULL, ..., envir=parent.frame(),
  drop=c("srcref", "srcfile", "wholeSrcref"), force=FALSE)

Arguments

expr	The expression to be evaluated.
key	Additional objects to uniquely identify the evaluation.
...	Additional arguments passed to loadCache() and saveCache().
envir	The environment in which the expression should be evaluated.
drop	character vector of expr attributes to drop. The default is to drop all source-reference information.
force	If TRUE, existing cached results are ignored.

Value

Returns the value of the evaluated expr expression, if any.

Author(s)

Henrik Bengtsson

See Also

Internally, eval() is used to evaluate the expression.

Examples

for (kk in 1:5) {
  cat(sprintf("Iteration #%d:\n", kk))
  res <- evalWithMemoization({
    cat("Evaluating expression...")
    a <- 1
    b <- 2
    c <- 4
    Sys.sleep(1)
    cat("done\n")
    b
  })
  print(res)

  # Sanity checks
  stopifnot(a == 1 && b == 2 && c == 4)

  # Clean up
  rm(a, b, c)
} # for (kk ...)


## OUTPUTS:
## Iteration #1:
## Evaluating expression...done
## [1] 2
## Iteration #2:
## [1] 2
## Iteration #3:
## [1] 2
## Iteration #4:
## [1] 2
## Iteration #5:
## [1] 2


############################################################
# WARNING
############################################################
# If the expression being evaluated depends on
# "input" objects, then these must be be specified
# explicitly as "key" objects.
for (ii in 1:2) {
  for (kk in 1:3) {
    cat(sprintf("Iteration #%d:\n", kk))
    res <- evalWithMemoization({
      cat("Evaluating expression...")
      a <- kk
      Sys.sleep(1)
      cat("done\n")
      a
    }, key=list(kk=kk))
    print(res)

    # Sanity checks
    stopifnot(a == kk)

    # Clean up
    rm(a)
  } # for (kk ...)
} # for (ii ...)

## OUTPUTS:
## Iteration #1:
## Evaluating expression...done
## [1] 1
## Iteration #2:
## Evaluating expression...done
## [1] 2
## Iteration #3:
## Evaluating expression...done
## [1] 3
## Iteration #1:
## [1] 1
## Iteration #2:
## [1] 2
## Iteration #3:
## [1] 3

R.cache documentation built on July 21, 2022, 5:11 p.m.