### Comparing Performance in R Using Microbenchmark

This post is a very simple display of how to use microbenchmark in R. Other sites might have longer and more detailed posts, but this post is primarily to 'spread the word' about this useful function, and show how to plot it. An alternative version of this post exists in Microsoft's Azure Notebooks, as Performance Testing Results with Microbenchmark

### Load Libraries

Memoise as part of the code to test, microbenchmark to show usage, and ggplot2 to plot the result.```
library(memoise)
library(microbenchmark)
library(ggplot2)
```

### Create Functions

Generate several functions with varied performance times, a base function plus functions that leverage vectorization and memoisation.```
# base function
monte_carlo = function(N) {
hits = 0
for (i in seq_len(N)) {
u1 = runif(1)
u2 = runif(1)
if (u1 ^ 2 > u2)
hits = hits + 1
}
return(hits / N)
}
# memoise test function
monte_carlo_memo <- memoise(monte_carlo)
# vectorize function
monte_carlo_vec <- function(N) mean(runif(N) ^ 2 > runif(N))
# memoise vectorized function
monte_carlo_vec_memo <- memoise(monte_carlo_vec)
```

### Run Tests

Using microbenchmark, loop 100 times through each function.```
n <- 999999
comparison <- microbenchmark(times = 100
, memoised = system.time(monte_carlo_memo(n))
, vectorised = system.time(monte_carlo_vec(n))
, both = system.time(monte_carlo_vec_memo(n)))
comparison
```

### Display Results:

Display the results of the microbenchmark run.```
Unit: milliseconds
expr min lq mean median uq max neval
memoised 45.88 51.55 109.45 57.93 63.04 5027.95 100
vectorised 176.18 226.01 235.94 236.47 248.78 332.85 100
both 46.23 50.67 59.60 54.74 62.86 224.50 100
```

### Plot

Using autoplot, display the results.```
autoplot(comparison)
```

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