R furrr plan在尝试调整多会话计划时返回错误？

Question

我正在尝试设置所需的计划，但遇到以下错误：

no_cores <- availableCores() - 2
plan(multisession, workers = no_cores, lazy = T, gc = T)

错误是：

Error in MultisessionFuture(expr = expr, envir = envir, substitute = FALSE,  : 
  argument "expr" is missing, with no default

或者：

plan(multisession, workers = no_cores, lazy = T, gc = T)
Error in tweak.future(function (expr, envir = parent.frame(), substitute = TRUE,  : 
  Future argument 'lazy' must not be tweaked / set via plan()

请告诉我如何设置multisession/multicore计划的workers、lazy、gc等参数。

我的R版本是：

R.Version()
$platform
[1] "x86_64-pc-linux-gnu"

$arch
[1] "x86_64"

$os
[1] "linux-gnu"

$system
[1] "x86_64, linux-gnu"

$status
[1] ""

$major
[1] "4"

$minor
[1] "0.2"

$year
[1] "2020"

$month
[1] "06"

$day
[1] "22"

$`svn rev`
[1] "78730"

$language
[1] "R"

$version.string
[1] "R version 4.0.2 (2020-06-22)"

$nickname
[1] "Taking Off Again"

Answer 1

尝试您的示例时，我得到了第二条错误消息。我基本上遵循了给出的建议:在plan中设置参数lazy = T，这是不允许的。但是，您可以直接在furrr函数调用中设置此参数：

library(furrr)
no_cores <- availableCores() - 2
plan(multisession, workers = no_cores, gc = T)

future_map(c("hello", "world"), ~.x,
           .options = future_options(lazy = TRUE))
[[1]]
[1] "hello"

[[2]]
[1] "world"