In: |
benchmark.rb
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The Benchmark module provides methods to measure and report the time used to execute Ruby code. Read on for illustrative examples.
To 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 P5100MHz) this reported as follows:
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.
To do some experiments sequentially, the bm method is useful:
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, to 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 argument to bm (7) specifies the offset of each report according to the longest label.
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 for 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)
To report statistics of sequential experiments with unique labels, benchmark is available:
require 'benchmark' 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)
BENCHMARK_VERSION | = | "2002-04-25" |
BENCHMARK_VERSION is version string containing the last modification date (YYYY-MM-DD). | ||
CAPTION | = | Benchmark::Tms::CAPTION |
The default caption string (heading above the output times). | ||
FMTSTR | = | Benchmark::Tms::FMTSTR |
The default format string used to display times. See also Benchmark::Tms#format. |
Reports the time required to execute one or more blocks of code.
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
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 parameters accepted are as follows:
caption: | A string printed once before execution of the given block. |
label_width: | An integer used as an offset in each report. |
fmtstr: | A string used to format each measurement. See Benchmark::Tms#format. |
labels: | The remaining parameters are used as prefix of the format to the value of block; see the example above. |
This method yields a Benchmark::Report object.
# File benchmark.rb, line 198 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 benchmark, bm is suitable for sequential reports with labels. For example:
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 argument to bm (7) specifies the offset of each report according to the longest label.
This reports as follows:
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 labels are optional.
# File benchmark.rb, line 239 def bm(label_width = 0, *labels, &blk) # :yield: report benchmark(" "*label_width + CAPTION, label_width, FMTSTR, *labels, &blk) end
Similar to bm, but designed to prevent memory allocation and garbage collection from influencing the result. It works like this:
If the specified label_width is less than the width of the widest label passed as an argument to item, the latter is used. (Because bmbm is a 2-pass procedure, this is possible.) Therefore you do not really need to specify a label width.
For example:
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)
bmbm yields a Benchmark::Job object and returns an array of one Benchmark::Tms objects.
# File benchmark.rb, line 283 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 326 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