Benchmark

Invokes the block with a Benchmark::Report object, which may be used to collect and report on the results of individual benchmark tests. Reserves label_width leading spaces for labels on each line. Prints caption at the top of the report, and uses format to format each line. Returns an array of Benchmark::Tms objects.

If the block returns an array of Benchmark::Tms objects, these will be used to format additional lines of output. If labels parameter are given, these are used to label these extra lines.

Note: Other methods provide a simpler interface to this one, and are suitable for nearly all benchmarking requirements. See the examples in Benchmark, and the bm and bmbm methods.

Example:

require 'benchmark'
include Benchmark          # we need the CAPTION and FORMAT constants

n = 5000000
Benchmark.benchmark(CAPTION, 7, FORMAT, ">total:", ">avg:") do |x|
  tf = x.report("for:")   { for i in 1..n; a = "1"; end }
  tt = x.report("times:") { n.times do   ; a = "1"; end }
  tu = x.report("upto:")  { 1.upto(n) do ; a = "1"; end }
  [tf+tt+tu, (tf+tt+tu)/3]
end

Generates:

              user     system      total        real
for:      0.970000   0.000000   0.970000 (  0.970493)
times:    0.990000   0.000000   0.990000 (  0.989542)
upto:     0.970000   0.000000   0.970000 (  0.972854)
>total:   2.930000   0.000000   2.930000 (  2.932889)
>avg:     0.976667   0.000000   0.976667 (  0.977630)

 
               # File benchmark.rb, line 165
def benchmark(caption = "", label_width = nil, format = nil, *labels) # :yield: report
  sync = STDOUT.sync
  STDOUT.sync = true
  label_width ||= 0
  label_width += 1
  format ||= FORMAT
  print ' '*label_width + caption unless caption.empty?
  report = Report.new(label_width, format)
  results = yield(report)
  Array === results and results.grep(Tms).each {|t|
    print((labels.shift || t.label || "").ljust(label_width), t.format(format))
  }
  report.list
ensure
  STDOUT.sync = sync unless sync.nil?
end
            

A simple interface to the benchmark method, bm generates sequential reports with labels. label_width and labels parameters have the same meaning as for benchmark.

require 'benchmark'

n = 5000000
Benchmark.bm(7) do |x|
  x.report("for:")   { for i in 1..n; a = "1"; end }
  x.report("times:") { n.times do   ; a = "1"; end }
  x.report("upto:")  { 1.upto(n) do ; a = "1"; end }
end

Generates:

              user     system      total        real
for:      0.960000   0.000000   0.960000 (  0.957966)
times:    0.960000   0.000000   0.960000 (  0.960423)
upto:     0.950000   0.000000   0.950000 (  0.954864)

 
               # File benchmark.rb, line 204
def bm(label_width = 0, *labels, &blk) # :yield: report
  benchmark(CAPTION, label_width, FORMAT, *labels, &blk)
end
            

Sometimes benchmark results are skewed because code executed earlier encounters different garbage collection overheads than that run later. bmbm attempts to minimize this effect by running the tests twice, the first time as a rehearsal in order to get the runtime environment stable, the second time for real. GC.start is executed before the start of each of the real timings; the cost of this is not included in the timings. In reality, though, there’s only so much that bmbm can do, and the results are not guaranteed to be isolated from garbage collection and other effects.

Because bmbm takes two passes through the tests, it can calculate the required label width.

require 'benchmark'

array = (1..1000000).map { rand }

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

Generates:

Rehearsal -----------------------------------------
sort!   1.440000   0.010000   1.450000 (  1.446833)
sort    1.440000   0.000000   1.440000 (  1.448257)
-------------------------------- total: 2.890000sec

            user     system      total        real
sort!   1.460000   0.000000   1.460000 (  1.458065)
sort    1.450000   0.000000   1.450000 (  1.455963)

bmbm yields a Benchmark::Job object and returns an array of Benchmark::Tms objects.

 
               # File benchmark.rb, line 246
def bmbm(width = 0) # :yield: job
  job = Job.new(width)
  yield(job)
  width = job.width + 1
  sync = STDOUT.sync
  STDOUT.sync = true

  # rehearsal
  puts 'Rehearsal '.ljust(width+CAPTION.length,'-')
  ets = job.list.inject(Tms.new) { |sum,(label,item)|
    print label.ljust(width)
    res = Benchmark.measure(&item)
    print res.format
    sum + res
  }.format("total: %tsec")
  print " #{ets}\n\n".rjust(width+CAPTION.length+2,'-')

  # take
  print ' '*width + CAPTION
  job.list.map { |label,item|
    GC.start
    print label.ljust(width)
    Benchmark.measure(label, &item).tap { |res| print res }
  }
ensure
  STDOUT.sync = sync unless sync.nil?
end
            

Returns the time used to execute the given block as a Benchmark::Tms object. Takes label option.

require 'benchmark'

n = 1000000

time = Benchmark.measure do
  n.times { a = "1" }
end
puts time

Generates:

0.220000   0.000000   0.220000 (  0.227313)

 
               # File benchmark.rb, line 291
def measure(label = "") # :yield:
  t0, r0 = Process.times, Process.clock_gettime(Process::CLOCK_MONOTONIC)
  yield
  t1, r1 = Process.times, Process.clock_gettime(Process::CLOCK_MONOTONIC)
  Benchmark::Tms.new(t1.utime  - t0.utime,
                     t1.stime  - t0.stime,
                     t1.cutime - t0.cutime,
                     t1.cstime - t0.cstime,
                     r1 - r0,
                     label)
end
            

Returns the elapsed real time used to execute the given block.

 
               # File benchmark.rb, line 306
def realtime # :yield:
  r0 = Process.clock_gettime(Process::CLOCK_MONOTONIC)
  yield
  Process.clock_gettime(Process::CLOCK_MONOTONIC) - r0
end