require'benchmark'

Benchmark

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_000:

    require'benchmark'putsBenchmark.measure{"a"*1_000_000_000}

    On my machine (OSX 10.8.3 on i5 1.7 GHz) this generates:

    0.350000 0.400000 0.750000 ( 0.835234)

    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=5000000Benchmark.bmdo|x|x.report{foriin1..n;a="1";end}x.report{n.timesdo;a="1";end}x.report{1.upto(n)do;a="1";end}end

    The result:

     user system total real 1.010000 0.000000 1.010000 ( 1.014479) 1.000000 0.000000 1.000000 ( 0.998261) 0.980000 0.000000 0.980000 ( 0.981335)

  • Continuing the previous example, put a label in each report:

    require'benchmark'n=5000000Benchmark.bm(7)do|x|x.report("for:"){foriin1..n;a="1";end}x.report("times:"){n.timesdo;a="1";end}x.report("upto:"){1.upto(n)do;a="1";end}end

The result:

 user system total real for: 1.010000 0.000000 1.010000 ( 1.015688) times: 1.000000 0.000000 1.000000 ( 1.003611) upto: 1.030000 0.000000 1.030000 ( 1.028098)

  • 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.bmbmdo|x|x.report("sort!"){array.dup.sort!}x.report("sort"){array.dup.sort}end

    The result:

    Rehearsal ----------------------------------------- sort! 1.490000 0.010000 1.500000 ( 1.490520) sort 1.460000 0.000000 1.460000 ( 1.463025) -------------------------------- total: 2.960000sec user system total real sort! 1.460000 0.000000 1.460000 ( 1.460465) sort 1.450000 0.010000 1.460000 ( 1.448327)

  • Report statistics of sequential experiments with unique labels, using the #benchmark method:

    require'benchmark'includeBenchmark# we need the CAPTION and FORMAT constantsn=5000000Benchmark.benchmark(CAPTION,7,FORMAT,">total:",">avg:")do|x|tf=x.report("for:"){foriin1..n;a="1";end}tt=x.report("times:"){n.timesdo;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: 0.950000 0.000000 0.950000 ( 0.952039) times: 0.980000 0.000000 0.980000 ( 0.984938) upto: 0.950000 0.000000 0.950000 ( 0.946787) >total: 2.880000 0.000000 2.880000 ( 2.883764) >avg: 0.960000 0.000000 0.960000 ( 0.961255)

Benchmark Reference

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