Benchmarks for different types of "unsorting"

unsort-benchmarks.R

library(tidyverse)
library(microbenchmark)

unsort_prealloc <- function(xo, ord) {
  xu <- character(length(xo))
  xu[ord] <- xo
  
  xu
}

unsort_reorder <- function(xo, ord) {
  xo[order(ord)]
}

bench_unsort <- function(n) {
  x <- sample(letters, n, replace = TRUE)
  ord <- order(x)
  xo <- x[ord]
  
  microbenchmark(
    prealloc = unsort_prealloc(xo, ord),
    reorder = unsort_reorder(xo, ord),
    times = 1000
  ) %>%
    group_by(expr) %>%
    summarise(med_time = median(time / 1e3))
}

set.seed(101)
benches <- tibble(n = floor(seq(10, 10000, length.out = 100))) %>%
  mutate(bench = map(n, bench_unsort)) %>%
  unnest(bench)

benches %>%
  ggplot(aes(n, med_time, color = expr)) +
    geom_line() +
    labs(x = "Vector length", y = "Median time (microseconds)") +
    guides(color = guide_legend(title = NULL)) +
    theme_bw()