Three examples showing three of the main methods of Ruby's Benchmark class that's used to profile your code. Benchmark.measure at the most basic, Benchmark.benchmark allows you to run trials of different code blocks, and Benchmark.bmbm that helps you establish a baseline for your tests.

ruby_benchmark_examples.rb

# http://www.ruby-doc.org/stdlib-2.0/libdoc/benchmark/rdoc/Benchmark.html
require 'benchmark'
# http://www.ruby-doc.org/stdlib-2.0.0/libdoc/bigdecimal/rdoc/BigMath.html
require 'bigdecimal/math'


# Set the number of iterations to run. The underscore here is used as a substitute for normal comma so Ruby interprets the number correctly.
iterations = 10
puts "\nCalculating pi #{iterations} times.\n\n"

# Calculate pi to specified number of digits.
puts Benchmark.measure("test") { BigMath.PI(iterations) }
puts "\n\n"


# =================
# .benchmark: Benchmark several blocks of code at once to see which is faster.
# =================

iterations = 10

caption = "String joining #{iterations} times.\n\n"

Benchmark.benchmark(caption, 30, nil) do |bm|
  bm.report("Joining array of strings: ") do
    iterations.times do
      ["The", "current", "time", "is", Time.now, ":"].join(" ")
    end
  end

  bm.report("Joining strings with plus signs") do
    iterations.times do
      "The" + "current" + "time" + "is" + "#{Time.now}" + ":"
    end
  end

  bm.report("Using string interpolation") do
    iterations.times do
      "The current time is #{Time.now}:"
    end
  end
end

# =================
# .bmbm: Establish baseline numbers for your tests by running them twice.
# =================

iterations = 1000
puts "\n\nSorting arrays #{iterations} times.\n\n"

array = (1..iterations).map { rand }

Benchmark.bmbm do |x|
  x.report("sort!") { array.dup.sort! }
  x.report("sort")  { array.dup.sort  }
end