cpu_vs_io.rb

require 'benchmark/ips'
require 'open-uri'
require 'bigdecimal'
require 'bigdecimal/math'

class Contract
  DIGITS = 10_000
  URL = 'http://www.nooooooooooooooo.com/'.freeze
  
  def call(parallel_io_only:, cpu_count:, io_count:)
    threads = []

    io_count.times { threads << Thread.new { io_meth } }

    if parallel_io_only
      cpu_count.times { cpu_meth }
    else
      cpu_count.times { threads << Thread.new { cpu_meth } }
    end
    
    threads.each(&:join)
  end

  private 

  def cpu_meth
    BigMath.PI(DIGITS)
  end

  def io_meth
    open(URL)
  end
end

[
  {cpu_count: 2, io_count: 6}, 
  {cpu_count: 3, io_count: 3}, 
  {cpu_count: 6, io_count: 2}
].each do |options|
  Benchmark.ips do |x|
    x.report("parallel_io_only: true, options: #{options}") do
      ::Contract.new.call(parallel_io_only: true, **options)
    end

    x.report("parallel_io_only: false, options: #{options}") do
      ::Contract.new.call(parallel_io_only: false, **options)
    end

    x.compare!
  end
end

Warming up --------------------------------------
parallel_io_only: true, options: {:cpu_count=>2, :io_count=>6}
                         1.000  i/100ms
parallel_io_only: false, options: {:cpu_count=>2, :io_count=>6}
                         1.000  i/100ms
Calculating -------------------------------------
parallel_io_only: true, options: {:cpu_count=>2, :io_count=>6}
                          0.996  (± 0.0%) i/s -      5.000  in   5.021074s
parallel_io_only: false, options: {:cpu_count=>2, :io_count=>6}
                          0.886  (± 0.0%) i/s -      5.000  in   5.668470s

Comparison:
parallel_io_only: true, options: {:cpu_count=>2, :io_count=>6}:        1.0 i/s
parallel_io_only: false, options: {:cpu_count=>2, :io_count=>6}:        0.9 i/s - 1.12x  slower

Warming up --------------------------------------
parallel_io_only: true, options: {:cpu_count=>3, :io_count=>3}
                         1.000  i/100ms
parallel_io_only: false, options: {:cpu_count=>3, :io_count=>3}
                         1.000  i/100ms
Calculating -------------------------------------
parallel_io_only: true, options: {:cpu_count=>3, :io_count=>3}
                          0.668  (± 0.0%) i/s -      4.000  in   5.983861s
parallel_io_only: false, options: {:cpu_count=>3, :io_count=>3}
                          0.629  (± 0.0%) i/s -      4.000  in   6.371746s

Comparison:
parallel_io_only: true, options: {:cpu_count=>3, :io_count=>3}:        0.7 i/s
parallel_io_only: false, options: {:cpu_count=>3, :io_count=>3}:        0.6 i/s - 1.06x  slower

Warming up --------------------------------------
parallel_io_only: true, options: {:cpu_count=>6, :io_count=>2}
                         1.000  i/100ms
parallel_io_only: false, options: {:cpu_count=>6, :io_count=>2}
                         1.000  i/100ms
Calculating -------------------------------------
parallel_io_only: true, options: {:cpu_count=>6, :io_count=>2}
                          0.336  (± 0.0%) i/s -      2.000  in   5.959183s
parallel_io_only: false, options: {:cpu_count=>6, :io_count=>2}
                          0.332  (± 0.0%) i/s -      2.000  in   6.025768s

Comparison:
parallel_io_only: true, options: {:cpu_count=>6, :io_count=>2}:        0.3 i/s
parallel_io_only: false, options: {:cpu_count=>6, :io_count=>2}:        0.3 i/s - 1.01x  slower