flat_map + compact VS filter_map + flatten

flat_map_compact_VS_filter_map_flatten.rb

require 'benchmark/ips'

Benchmark.ips do |bm|
  # Create a list with 10_000 elements and some nil values
  list = (0..10_000).to_a

  fn = ->(x) { [x, x * x] if x.even? }

  bm.report "flat_map + compact" do
    list.flat_map(&fn).compact
  end

  bm.report "filter_map + flatten" do
    list.filter_map(&fn).flatten
  end

  bm.compare!
end

ruby 3.3.1 (2024-04-23 revision c56cd86388) [arm64-darwin23]
Warming up --------------------------------------
  flat_map + compact   123.000 i/100ms
filter_map + flatten    85.000 i/100ms
Calculating -------------------------------------
  flat_map + compact      1.240k (± 1.5%) i/s  (806.50 μs/i) -      6.273k in   5.060373s
filter_map + flatten    863.176 (± 2.4%) i/s    (1.16 ms/i) -      4.335k in   5.025297s

Comparison:
  flat_map + compact:     1239.9 i/s
filter_map + flatten:      863.2 i/s - 1.44x  slower