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Parallelize 'purrr' functions

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The futurize package allows you to easily turn sequential code into parallel code by piping the sequential code to the futurize() function. Easy!

TL;DR

library(futurize)
plan(multisession)
library(purrr)

slow_fcn <- function(x) {
  Sys.sleep(0.1)  # emulate work
  x^2
}

xs <- 1:1000
ys <- xs |> map(slow_fcn) |> futurize()

Introduction

This vignette demonstrates how to use this approach to parallelize purrr functions such as map(), map_dbl(), and walk().

The purrr map() function is commonly used to apply a function to the elements of a vector or a list. For example,

library(purrr)
xs <- 1:1000
ys <- map(xs, slow_fcn)

or equivalently using pipe syntax

library(purrr)
xs <- 1:1000
ys <- xs |> map(slow_fcn)

Here map() evaluates sequentially, but we can easily make it evaluate in parallel, by using:

library(futurize)
library(purrr)
xs <- 1:1000
ys <- xs |> map(slow_fcn) |> futurize()

This will distribute the calculations across the available parallel workers, given that we have set parallel workers, e.g.

plan(multisession)

The built-in multisession backend parallelizes on your local computer and it works on all operating systems. There are [other parallel backends] to choose from, including alternatives to parallelize locally as well as distributed across remote machines, e.g.

plan(future.mirai::mirai_multisession)

and

plan(future.batchtools::batchtools_slurm)

Another example is:

library(purrr)
library(futurize)
plan(future.mirai::mirai_multisession)

ys <- 1:10 |>
        map(rnorm, n = 10) |> futurize(seed = TRUE) |>
        map_dbl(mean) |> futurize()

Supported Functions

The futurize() function supports parallelization of the following purrr functions:

• map(), map_chr(), map_dbl(), map_int(), map_lgl(), map_raw(), map_dfr(), map_dfc(), walk()
• map2(), map2_chr(), map2_dbl(), map2_int(), map2_lgl(), map2_raw(), map2_dfr(), map2_dfc(), walk2()
• pmap(), pmap_chr(), pmap_dbl(), pmap_int(), pmap_lgl(), pmap_raw(), pmap_dfr(), pmap_dfc(), pwalk() imap(), imap_chr(), imap_dbl(), imap_int(), imap_lgl(), imap_raw(), imap_dfr(), imap_dfc(), iwalk()
• modify(), modify_if(), modify_at()
• map_if(), map_at()
• invoke_map(), invoke_map_chr(), invoke_map_dbl(), invoke_map_int(), invoke_map_lgl(), invoke_map_raw(), invoke_map_dfr(), invoke_map_dfc()

These binaries (installable software) and packages are in development.
They may not be fully stable and should be used with caution. We make no claims about them.
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