How to stop a function in R that is taking too long and give it an alternative?

Question

I'm trying to do a thing "the right way". Sometimes "the right way" takes too long, depending on the inputs. I can't really know a priori when this will be. When "the right way" is taking too long, I want to go to "the hackish way". How do I make R monitor how long a particular task as taken, and give it something else to do if a threshold has passed? I'd imagine that this will be part of the try family, but I'm not quite sure what to call it or google for.

Dummy example below. When slow.func takes too long, I want interuptor to stop it and call fast.func instead.

slow.func <- function(x){     Sys.sleep(x)         print('good morning') }  fast.func <- function(x){     Sys.sleep(x/10)      print('hit snooze') }  interuptor = function(FUN,args, time.limit, ALTFUN){ #   START MONITORING TIME HERE     do.call(FUN,args) #   IF FUN TAKES TOO LONG, STOP IT, CALL A     do.call(ALTFUN,args) }  interuptor(slow.func, list(x = 2), time.limit = 1, fast.func) 

Answer 1

The R package R.utils has a function evalWithTimeout that's pretty much exactly what you're describing. If you don't want to install a package, evalWithTimeout relies on the less user friendly R base function setTimeLimit

Your code would look something like this:

library(R.utils)  slow.func <- function(x){   Sys.sleep(10)       return(x^2) }  fast.func <- function(x){   Sys.sleep(2)  return(x*x) } interruptor = function(FUN,args, time.limit, ALTFUN){   results <- NULL   results <- evalWithTimeout({FUN(args)},timeout=time.limit,onTimeout="warning")   if(results==NULL){     results <- ALTFUN(args)   }   return(results) }    interruptor(slow.func,args=2,time.limit=3,fast.func)