The Benchmark module provides methods to measure and report the time used to execute Ruby code.
Measure the time to construct the string given by the expression
"a"*1_000_000
:
require 'benchmark' puts Benchmark.measure { "a"*1_000_000 }
On my machine (FreeBSD 3.2 on P5, 100MHz) this generates:
1.166667 0.050000 1.216667 ( 0.571355)
This report shows the user CPU time, system CPU time, the sum of the user and system CPU times, and the elapsed real time. The unit of time is seconds.
Do some experiments sequentially using the bm method:
require 'benchmark' n = 50000 Benchmark.bm do |x| x.report { for i in 1..n; a = "1"; end } x.report { n.times do ; a = "1"; end } x.report { 1.upto(n) do ; a = "1"; end } end
The result:
user system total real 1.033333 0.016667 1.016667 ( 0.492106) 1.483333 0.000000 1.483333 ( 0.694605) 1.516667 0.000000 1.516667 ( 0.711077)
Continuing the previous example, put a label in each report:
require 'benchmark' n = 50000 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
The result:
user system total real for: 1.050000 0.000000 1.050000 ( 0.503462) times: 1.533333 0.016667 1.550000 ( 0.735473) upto: 1.500000 0.016667 1.516667 ( 0.711239)
The times for some benchmarks depend on the order in which items are run. These differences are due to the cost of memory allocation and garbage collection. To avoid these discrepancies, the bmbm method is provided. For example, to compare ways to sort an array of floats:
require 'benchmark' array = (1..1000000).map { rand } Benchmark.bmbm do |x| x.report("sort!") { array.dup.sort! } x.report("sort") { array.dup.sort } end
The result:
Rehearsal ----------------------------------------- sort! 11.928000 0.010000 11.938000 ( 12.756000) sort 13.048000 0.020000 13.068000 ( 13.857000) ------------------------------- total: 25.006000sec user system total real sort! 12.959000 0.010000 12.969000 ( 13.793000) sort 12.007000 0.000000 12.007000 ( 12.791000)
Report statistics of sequential experiments with unique labels, using the benchmark method:
require 'benchmark' include Benchmark # we need the CAPTION and FMTSTR constants n = 50000 Benchmark.benchmark(" "*7 + CAPTION, 7, FMTSTR, ">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
The result:
user system total real for: 1.016667 0.016667 1.033333 ( 0.485749) times: 1.450000 0.016667 1.466667 ( 0.681367) upto: 1.533333 0.000000 1.533333 ( 0.722166) >total: 4.000000 0.033333 4.033333 ( 1.889282) >avg: 1.333333 0.011111 1.344444 ( 0.629761)
The default caption string (heading above the output times).
The default format string used to display times. See also Benchmark::Tms#format.
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 fmt to
format each line. If the block returns an array of
Benchmark::Tms
objects, these will be used to format
additional lines of output. If label parameters 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 FMTSTR constants n = 50000 Benchmark.benchmark(" "*7 + CAPTION, 7, FMTSTR, ">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: 1.016667 0.016667 1.033333 ( 0.485749) times: 1.450000 0.016667 1.466667 ( 0.681367) upto: 1.533333 0.000000 1.533333 ( 0.722166) >total: 4.000000 0.033333 4.033333 ( 1.889282) >avg: 1.333333 0.011111 1.344444 ( 0.629761)
# File benchmark.rb, line 171 def benchmark(caption = "", label_width = nil, fmtstr = nil, *labels) # :yield: report sync = STDOUT.sync STDOUT.sync = true label_width ||= 0 fmtstr ||= FMTSTR raise ArgumentError, "no block" unless iterator? print caption results = yield(Report.new(label_width, fmtstr)) Array === results and results.grep(Tms).each {|t| print((labels.shift || t.label || "").ljust(label_width), t.format(fmtstr)) } STDOUT.sync = sync end
A simple interface to the benchmark method, bm is generates sequential reports with labels. The parameters have the same meaning as for benchmark.
require 'benchmark' n = 50000 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: 1.050000 0.000000 1.050000 ( 0.503462) times: 1.533333 0.016667 1.550000 ( 0.735473) upto: 1.500000 0.016667 1.516667 ( 0.711239)
# File benchmark.rb, line 207 def bm(label_width = 0, *labels, &blk) # :yield: report benchmark(" "*label_width + CAPTION, label_width, FMTSTR, *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! 11.928000 0.010000 11.938000 ( 12.756000) sort 13.048000 0.020000 13.068000 ( 13.857000) ------------------------------- total: 25.006000sec user system total real sort! 12.959000 0.010000 12.969000 ( 13.793000) sort 12.007000 0.000000 12.007000 ( 12.791000)
bmbm yields a Benchmark::Job object and returns an array of Benchmark::Tms objects.
# File benchmark.rb, line 249 def bmbm(width = 0, &blk) # :yield: job job = Job.new(width) yield(job) width = job.width sync = STDOUT.sync STDOUT.sync = true # rehearsal print "Rehearsal " puts '-'*(width+CAPTION.length - "Rehearsal ".length) list = [] job.list.each{|label,item| print(label.ljust(width)) res = Benchmark::measure(&item) print res.format() list.push res } sum = Tms.new; list.each{|i| sum += i} ets = sum.format("total: %tsec") printf("%s %s\n\n", "-"*(width+CAPTION.length-ets.length-1), ets) # take print ' '*width, CAPTION list = [] ary = [] job.list.each{|label,item| GC::start print label.ljust(width) res = Benchmark::measure(&item) print res.format() ary.push res list.push [label, res] } STDOUT.sync = sync ary end
Returns the time used to execute the given block as a Benchmark::Tms object.
# File benchmark.rb, line 292 def measure(label = "") # :yield: t0, r0 = Benchmark.times, Time.now yield t1, r1 = Benchmark.times, Time.now Benchmark::Tms.new(t1.utime - t0.utime, t1.stime - t0.stime, t1.cutime - t0.cutime, t1.cstime - t0.cstime, r1.to_f - r0.to_f, label) end