visualizing_effect_of_gvl.rb

# frozen_string_literal: true

require 'bundler/inline'
require 'benchmark'

gemfile do
  source 'https://rubygems.org'
  gem 'gvl-tracing'
  gem 'parallel'
end

def cpu_intensive(n)
  result = 0
  n.times do |i|
    n.times do |j|
      result += i * j
    end
  end
  result
end

def benchmark(thread_count, type, &block)
  puts "\nStarting demo with #{thread_count} threads doing #{type} work"

  time = Benchmark.realtime do
    Parallel.each(Array.new(8) { |i| [i] },
                                 in_threads: thread_count) do |chunk|
      yield
    end
  end

  puts "Time elapsed: #{time.round(4)} seconds"
end


puts "Running demonstrations with GVL tracing..."

GvlTracing.start("cpu_bound_single.json") do
  benchmark(1, 'CPU-bound') { cpu_intensive(5000) }
end

GvlTracing.start("cpu_bound_multi.json") do
  benchmark(3, 'CPU-bound') { cpu_intensive(5000) }
end

def mixed_workload(n)
  sleep(0.05)
  cpu_intensive(n)
end

GvlTracing.start("mixed_single.json") do
  benchmark(1, 'Mixed I/O and CPU') { mixed_workload(5000) }
end

GvlTracing.start("mixed_multi.json") do
  benchmark(3, 'Mixed I/O and CPU') { mixed_workload(5000) }
end