multiprocess {future} | R Documentation |
A multiprocess future is a future that uses multicore evaluation
if supported, otherwise it uses multisession evaluation.
Regardless, its value is computed and resolved in
parallel in another process.
WARNING: Consider the 'multiprocess' future plan deprecated.
Instead, explicitly specify 'multisession' or 'multicore'. The former works
everywhere and is the recommended one between the two. Forked processing,
which 'multicore' uses, is unstable in various environment and setups.
The 'multiprocess' alias is therefore being phased out.
multiprocess( expr, envir = parent.frame(), substitute = TRUE, lazy = FALSE, seed = NULL, globals = TRUE, workers = availableCores(), gc = FALSE, earlySignal = FALSE, label = NULL, ... )
expr |
An R expression. |
envir |
The environment from where global objects should be identified. |
substitute |
If TRUE, argument |
lazy |
If FALSE (default), the future is resolved eagerly (starting immediately), otherwise not. |
seed |
(optional) If TRUE, the random seed, that is, the state of the
random number generator (RNG) will be set such that statistically sound
random numbers are produced (also during parallelization).
If FALSE, it is assumed that the future expression does neither need nor
use random numbers generation.
To use a fixed random seed, specify a L'Ecuyer-CMRG seed (seven integer)
or a regular RNG seed (a single integer).
Furthermore, if FALSE, then the future will be monitored to make sure it
does not use random numbers. If it does and depending on the value of
option |
globals |
(optional) a logical, a character vector, or a named list
to control how globals are handled.
For details, see section 'Globals used by future expressions'
in the help for |
workers |
A positive numeric scalar or a function specifying the maximum number of parallel futures that can be active at the same time before blocking. If a function, it is called without arguments when the future is created and its value is used to configure the workers. The function should return a numeric scalar. |
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 |
Specified whether conditions should be signaled as soon as possible or not. |
label |
An optional character string label attached to the future. |
... |
Additional named elements passed to |
A MultiprocessFuture implemented as either a MulticoreFuture or a MultisessionFuture.
Internally multicore()
and multisession()
are used.
## Use multiprocess futures plan(multiprocess) ## A global variable a <- 0 ## Create future (explicitly) f <- future({ b <- 3 c <- 2 a * b * c }) ## A multiprocess future is evaluated in a separate R process. ## Changing the value of a global variable will not affect ## the result of the future. a <- 7 print(a) v <- value(f) print(v) stopifnot(v == 0) ## Explicitly close multisession workers, if they were used plan(sequential)