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.
eager(expr, envir = parent.frame(), substitute = TRUE, lazy = FALSE,
seed = NULL, globals = TRUE, local = TRUE, earlySignal = FALSE,
label = NULL, ...)lazy(expr, envir = parent.frame(), substitute = TRUE, lazy = TRUE,
seed = NULL, globals = TRUE, local = TRUE, earlySignal = FALSE,
label = NULL, ...)
sequential(expr, envir = parent.frame(), substitute = TRUE, lazy = FALSE,
seed = NULL, globals = TRUE, local = TRUE, earlySignal = FALSE,
label = NULL, ...)
transparent(expr, envir = parent.frame(), substitute = TRUE, lazy = FALSE,
seed = NULL, globals = FALSE, local = FALSE, earlySignal = TRUE,
label = NULL, ...)
An R expression to be evaluated.
The environment from where global
objects should be identified. Depending on the future
strategy (the evaluator
), it may also be the environment
in which the expression is evaluated.
If TRUE, argument expr
is
substitute()
:ed, otherwise not.
Specifies whether a future should be resolved lazily or eagerly (default).
(optional) A L'Ecuyer-CMRG RNG seed.
A logical, a character vector, or a named list for controlling how globals are handled. For details, see below section.
If TRUE, the expression is evaluated such that all assignments are done to local temporary environment, otherwise the assignments are done in the calling environment.
Specified whether conditions should be signaled as soon as possible or not.
An optional character string label attached to the future.
Additional arguments passed to the "evaluator".
Transparent futures are sequential futures configured to emulate how R
evaluates expressions as far as possible. For instance, errors and
warnings are signaled immediately and assignments are done to the
calling environment (without local()
as default for all other
types of futures). This makes transparent futures ideal for
troubleshooting, especially when there are errors.
The preferred way to create a sequential future is not to call these functions
directly, but to register them via plan(sequential)
such that
it becomes the default mechanism for all futures. After this
future()
and %<-%
will create
sequential futures.
# NOT RUN {
## 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)
v <- value(f)
print(v)
stopifnot(v == 0)
# }
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