Create a sequential future whose value will be in the current R session

A sequential future is a future that is evaluated sequentially in the current R session similarly to how R expressions are evaluated in R. The only difference to R itself is that globals are validated by default just as for all other types of futures in this package.

Usage

sequential(..., gc = FALSE, earlySignal = FALSE, envir = parent.frame())

Arguments

gc

If TRUE, the garbage collector run (in the process that evaluated the future) only after the value of the future is collected. Exactly when the values are collected may depend on various factors such as number of free workers and whether earlySignal is TRUE (more frequently) or FALSE (less frequently). Some types of futures ignore this argument.

earlySignal

Specified whether conditions should be signaled as soon as possible or not.

envir

The environment from where global objects should be identified.

...

Additional named elements to Future().

Value

A Future.

Details

This function is not meant to be called directly. Instead, the typical usages are:

# Evaluate futures sequentially in the current R process
plan(sequential)

Examples

## Use sequential futures
plan(sequential)

## A global variable
a <- 0

## Create a sequential future
f <- future({
  b <- 3
  c <- 2
  a * b * c
})

## Since 'a' is a global variable in future 'f' which
## is eagerly resolved (default), this global has already
## been resolved / incorporated, and any changes to 'a'
## at this point will _not_ affect the value of 'f'.
a <- 7
print(a)
#> [1] 7

v <- value(f)
print(v)
#> [1] 0
stopifnot(v == 0)