R tips: Determine if function is called from specific package
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I like the “multicore” library for a particular task. I can easily write a combination of if(require("multicore",...))
that means that my function will automatically use the parallel mclapply()
instead of lapply()
where it is available. Which is grand 99% of the time, except when my function is called from mclapply()
(or one of the lower level functions) in which case much CPU trashing and grinding of teeth will result.
So, I needed a function to determine if my function was called from any function in the “multicore” library. Here it is.
First define a generally useful function:
is.in.namespace < function (ns) { for ( frame in seq(1, sys.nframe(), 1) ) { fun < sys.function(frame); env < environment(fun) n < environmentName(env) if ( n == ns ) return(TRUE); } return(FALSE); }
Then we use it for our purpose:
is.in.multicore < function (...) { return(is.in.namespace("multicore")) } library("multicore") stopifnot( mclapply(as.list(1), is.in.multicore)[[1]] == TRUE ) stopifnot( lapply(as.list(1), is.in.multicore)[[1]] == FALSE ) stopifnot( local( {mclapply < function(x) return(x); mclapply(is.in.multicore())} ) == FALSE )
Easy when you know how.
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