bench.rb

require "benchmark"

srand(42)
ARRAY = 1_000_000.times.map { rand }.freeze

Benchmark.bmbm do |b|
  b.report("combined")  { ARRAY.select{|val| val < 500 && val > -500 && !val.zero?}.map{|val| -2 * val}.select{|val| val / 2 < 1}.to_a }
  b.report("separate")  { ARRAY.select{|val| val < 500}.select{|val| val > -500}.reject(&:zero?).map{|val| -2 * val}.select{|val| val / 2 < 1}.to_a }
  b.report("lazy-sep")  { ARRAY.lazy.select{|val| val < 500}.select{|val| val > -500}.reject(&:zero?).map{|val| -2 * val}.select{|val| val / 2 < 1}.to_a }
  b.report("lazy-comb") { ARRAY.lazy.select{|val| val < 500 && val > -500 && !val.zero?}.map{|val| -2 * val}.select{|val| val / 2 < 1}.to_a }
  b.report("in-place")  { x = ARRAY.dup ; x.select!{|val| val < 500 && val > -500 && !val.zero?} ; x.map!{|val| -2 * val} ; x.select{|val| val / 2 < 1} ; x.to_a }
end

result.txt

Rehearsal ---------------------------------------------
combined    0.279523   0.008966   0.288489 (  0.290051)
separate    0.337086   0.011403   0.348489 (  0.349970)
lazy-sep    0.490321   0.006044   0.496365 (  0.498582)
lazy-comb   0.409920   0.005352   0.415272 (  0.416394)
in-place    0.255416   0.003981   0.259397 (  0.260249)
------------------------------------ total: 1.808012sec

                user     system      total        real
combined    0.255729   0.000469   0.256198 (  0.256833)
separate    0.327413   0.007568   0.334981 (  0.336166)
lazy-sep    0.486621   0.002601   0.489222 (  0.490811)
lazy-comb   0.402537   0.001565   0.404102 (  0.405677)
in-place    0.260623   0.005263   0.265886 (  0.267473)

ruby-version.txt

ruby 2.7.3p183 (2021-04-05 revision 6847ee089d) [x86_64-darwin20]