getOption benchmark

bench.R

getOptionOld <- function(x, default = NULL) {
    ## To avoid always performing the %in%,
    ## we use the original code if default is not specified.
    ## if(missing(default)) return(options(x)[[1L]])
    if(missing(default) || x %in% names(.Options))
      .Internal(getOption(x))
    else
      default
}

getOptionNew <- function(x, default = NULL) {
  ans <- .Internal(getOption(x))
  ## not distinguishing an option that's NULL from a non-existing option
  if(is.null(ans)) default else ans
}

bench <- microbenchmark::microbenchmark(
  old_found = getOptionOld("width"),
  old_missing = getOptionOld("blah"),
  old_missing_default = getOptionOld("blah", "foo"),
  new_found = getOptionNew("width"),
  new_missing = getOptionNew("blah"),
  new_missing_default = getOptionNew("blah", "foo")
)
bench
#> Unit: nanoseconds
#>                 expr  min     lq     mean median     uq     max neval cld
#>            old_found  406  450.0   536.53  493.0  570.0     925   100   a
#>          old_missing  559  625.5 23613.27  707.0  829.5 2282638   100   a
#>  old_missing_default 2138 2324.0  2507.76 2394.5 2517.0    8430   100   a
#>            new_found  413  469.0   568.09  529.0  601.5    1588   100   a
#>          new_missing  575  620.0   739.83  690.5  799.0    1416   100   a
#>  new_missing_default  581  647.5 21285.04  746.5  865.5 2029400   100   a

# Would need to lookup a missing option with a default 1 million times before this
# would take more than 1 second.
system.time({ i <- 1; while((i <- i + 1) <= 1000000) getOptionOld("blah", "foo") })
#>    user  system elapsed 
#>   3.026   0.270   3.304

# Created on 2018-03-29 by the [reprex package](http://reprex.tidyverse.org) (v0.2.0).