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 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 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 164
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. The 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 203
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 245
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.

 
 # File benchmark.rb, line 286
def measure(label = "") # :yield:
 t0, r0 = Process.times, Process.clock_gettime(BENCHMARK_CLOCK)
 yield
 t1, r1 = Process.times, Process.clock_gettime(BENCHMARK_CLOCK)
 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 301
def realtime # :yield:
 r0 = Process.clock_gettime(BENCHMARK_CLOCK)
 yield
 Process.clock_gettime(BENCHMARK_CLOCK) - r0
end