Benchmarks for replace-megaparsec and replace-attoparsec.

To run the benchmarks,

nix run github:jamesdbrock/replace-benchmark 

These benchmarks are intended to measure the wall-clock speed of everything except the actual pattern-matching. Speed of the pattern-matching is the responsibility of the megaparsec and attoparsec libraries.

The benchmark task is to find all of the one-character patterns x in a text stream and replace them by a function which returns the constant string oo. So, like the regex s/x/oo/g.

We have two benchmark input cases, which we call dense and sparse.

The dense case is ten megabytes of alternating spaces and xs like

x x x x x x x x x x x x x x x x x x x x x x x x x x x x 

The sparse case is ten megabytes of spaces with a single x in the middle like

 x 

Each benchmark program reads the input from stdin, replaces x with oo, and writes the result to stdout. The time elapsed is measured in milliseconds by perf stat, and the best observed time is recorded.

In milliseconds. Smaller is better.

Here is a comparison of replacement methods which can use an arbitrary function to calculate the replacement string.

For reference, here is a comparison of replacement methods which can only replace with a constant string or a templated string.