vbalazs / array_intersection_experiments

This repository just contains my experiments with different array intersection algorithms and their benchmarks.

Benchmarking array intersection algos

This repository just contains my experiments with different array intersection algorithms and their benchmarks.

There are two benchmarks in the repository:

• benchmark.rb: runs algorithms against unsorted arrays
• benchmark_presorted.rb: runs algorithms against pre-sorted arrays to see what is the difference if we know the input arrays are already sorted.

Results

I ran the benchmarks on my MacBook Pro (Retina, 13-inch, Early 2015, 2,7 GHz Intel Core i5). Comparing two arrays both with ~10k random elements.

To replicate the results, do the followings:

$ gem install bundler
$ bundle install
$ ruby intersections_test.rb # make sure the tests pass
$ ruby benchmark.rb

Unsorted arrays

Comparison:
         ruby stdlib:      434.7 i/s
double_elevators_with_sort:      213.1 i/s - 2.04x  slower
        hash_storage:      165.3 i/s - 2.63x  slower
               naive:        0.2 i/s - 2322.68x  slower

Pre-sorted arrays

Comparison:
double_elevators_on_sorted:      530.2 i/s
         ruby stdlib:      491.3 i/s - 1.08x  slower
double_elevators_with_sort:      317.0 i/s - 1.67x  slower
        hash_storage:      184.8 i/s - 2.87x  slower
               naive:        0.2 i/s - 2884.84x  slower