furrr error

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plan(multiprocess) # on Macbook

Warning message:
[ONE-TIME WARNING] Forked processing ('multicore') is disabled in future (>= 1.13.0) when running R from RStudio, because it is considered unstable. 

Because of this, 
plan("multicore") will fall back to plan("sequential"), and plan("multiprocess") will fall back to plan("multisession") - not plan("multicore") as in the past. 

For more details, how to control forked processing or not, and how to silence this warning in future R sessions, see ?future::supportsMulticore 
> supportsMulticore()
#Sys.getenv("R_FUTURE_FORK_ENABLE")       #""

getOption("future.fork.enable")          #NULL

https://blog.seulgi.kim/2016/03/fork-in-multithread.html – 멀티 쓰레드 환경에서 fork는 조심해야 한다.

POSIX시스템(Unix…)에서는 fork를 이용해서 자신과 똑같은 프로세스를 만들 수 있다. forking means cloning everything in the process  including things like file descriptors — that means things like sockets that the rsession uses for communication with the front-end, or even possibly things like mutexes held by background threads. 

> rm(list=ls())
> options(shiny.reactlog=T)
> options(useFancyQuotes=F)  # windows error
> options(future.fork.enable=TRUE)
> library(future)
> plan(multiprocess, workers = 2, verbose=T)
Error in socketConnection("localhost", port = port, server = TRUE, blocking = TRUE,  : 
  Failed to launch and connect to R worker on local machine 'localhost' from local machine 'SIXXPC'.
 * The error produced by socketConnection() was: 'reached elapsed time limit' (which suggests that the connection timeout of 120 seconds (argument 'connectTimeout') kicked in)
 * The localhost socket connection that failed to connect to the R worker used port 11819 using a communication timeout of 2592000 seconds and a connection timeout of 120 seconds.
 * Worker launch call: "C:/PROGRA~1/R/R-36~1.1/bin/x64/Rscript" --default-packages=datasets,utils,grDevices,graphics,stats,methods -e "parallel:::.slaveRSOCK()" MASTER=localhost PORT=11819 OUT=/dev/null TIMEOUT=2592000 XDR=TRUE.
 * Failed to kill local worker because it's PID is could not be identified.
 * Troubleshooting suggestions:
   - Suggestion #1: Set 'verbose=TRUE' to see more details.
   - Suggestion #2: On Windows, output from worker when using 'outfile=NULL' is only visible when running R from a terminal (not a GUI).
In addition: Warning messages:
1: In tweak.future(function (expr, envir = parent.frame(), substitute = TRUE,  :
  Ignored 1 unknown arguments: 'verbose'
2: In system(test_cmd, intern = TRUE, input = input) :
  running command '"C:/PROGRA~1/R/R-36~1.1/bin/x64/Rscript" -e "try(suppressWarnings(cat(Sys.getpid(),file=\\"C:/Users/ADMINI~1/AppData/Local/Temp/RtmpI9b5nk/future.parent=14004.36b41e57741c.pid\\")), silent = TRUE)" -e "file.exists(\\"C:/Users/ADMINI~1/AppData/Local/Temp/RtmpI9b5nk/future.parent=14004.36b41e57741c.pid\\")"' had status 1
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