Note: BenchmarkTools now prints very pretty histograms automatically for @benchmark. This package is therefore obsolete.
Wraps BenchmarkTools.jl to provide a unicode histogram show method for @benchmark. This is accomplished by a custom @benchmark method which wraps the output in a BenchmarkPlot struct with a custom show method.
This means one should not call using on both BenchmarkHistograms and BenchmarkTools in the same namespace, or else these @benchmark macros will conflict ("WARNING: using BenchmarkTools.@benchmark in module Main conflicts with an existing identifier.")
However, BenchmarkHistograms re-exports all the export of BenchmarkTools, so you can simply call using BenchmarkHistograms.
Providing this functionality in BenchmarkTools itself was discussed in JuliaCI/BenchmarkTools.jl#180. Thanks to @brenhinkeller for providing the initial plotting code there.
Use the setting BenchmarkHistograms.NBINS to change the number of histogram bins used, e.g. BenchmarkHistograms.NBINS[] = 10 for 10 bins.
Likewise use the setting BenchmarkHistograms.OUTLIER_QUANTILE to tweak which values count as outliers and may be grouped into a single bin.
For example, BenchmarkHistograms.OUTLIER_QUANTILE[] = 0.99 counts any values past the 99 percentile as possible outliers. This value defaults to 0.999 and is disabled by setting it to 1.0.
One just uses BenchmarkHistograms instead of BenchmarkTools, e.g.
using BenchmarkHistograms
@benchmark sin(x) setup=(x=rand())samples: 10000; evals/sample: 1000; memory estimate: 0 bytes; allocs estimate: 0
ns
(8.04 - 8.53 ] ██████████████████████████████▏7673
(8.53 - 9.02 ] ▌109
(9.02 - 9.51 ] ▏3
(9.51 - 10.01] 0
(10.01 - 10.5 ] 0
(10.5 - 10.99] █████▋1431
(10.99 - 11.48] ██▌624
(11.48 - 11.97] ▍70
(11.97 - 12.46] ▎38
(12.46 - 12.95] ▏4
(12.95 - 13.44] ▏1
(13.44 - 13.93] ▏2
(13.93 - 14.42] ▏7
(14.42 - 14.92] ▏22
(14.92 - 21.88] ▏16
Counts
min: 8.041 ns (0.00% GC); mean: 8.812 ns (0.00% GC); median: 8.166 ns (0.00% GC); max: 21.875 ns (0.00% GC).
That benchmark does not have a very interesting distribution, but it's not hard to find more interesting cases.
@benchmark 5 ∈ v setup=(v = sort(rand(1:10000, 10000)))samples: 3110; evals/sample: 1000; memory estimate: 0 bytes; allocs estimate: 0
ns
(0.0 - 280.0 ] ██████████████████████████████ 1964
(280.0 - 570.0 ] 0
(570.0 - 850.0 ] 0
(850.0 - 1130.0] 0
(1130.0 - 1410.0] 0
(1410.0 - 1690.0] 0
(1690.0 - 1970.0] 0
(1970.0 - 2250.0] 0
(2250.0 - 2540.0] 0
(2540.0 - 2820.0] 0
(2820.0 - 3100.0] 0
(3100.0 - 3380.0] █████████████████1105
(3380.0 - 3660.0] ▊41
Counts
min: 2.500 ns (0.00% GC); mean: 1.181 μs (0.00% GC); median: 5.334 ns (0.00% GC); max: 3.663 μs (0.00% GC).
Here, we see a bimodal distribution; in the case 5 is indeed in the vector, we find it very quickly, in the 0-1000 ns range (thanks to sort which places it at the front). In the case 5 is not present, we need to check every entry to be sure, and we end up in the 3000-4000 ns range.
Without the sort, we end up with more of a uniform distribution:
@benchmark 5 ∈ v setup=(v = rand(1:10000, 10000))samples: 2393; evals/sample: 1000; memory estimate: 0 bytes; allocs estimate: 0
ns
(0.0 - 310.0 ] ███████▏214
(310.0 - 610.0 ] ██████▍191
(610.0 - 910.0 ] █████▊173
(910.0 - 1220.0] █████▊174
(1220.0 - 1520.0] █████▏155
(1520.0 - 1830.0] ████▍133
(1830.0 - 2130.0] ████119
(2130.0 - 2430.0] ███▍100
(2430.0 - 2740.0] ██▉86
(2740.0 - 3040.0] ███▍102
(3040.0 - 3350.0] ██████████████████████████████ 912
(3350.0 - 3650.0] █30
(3650.0 - 5870.0] ▎4
Counts
min: 2.334 ns (0.00% GC); mean: 2.037 μs (0.00% GC); median: 2.236 μs (0.00% GC); max: 5.869 μs (0.00% GC).
This function gives a somewhat more Gaussian distribution of times, kindly supplied by Mason Protter:
f() = sum((sin(i) for i in 1:round(Int, 1000 + 100*randn())))
@benchmark f()samples: 10000; evals/sample: 3; memory estimate: 0 bytes; allocs estimate: 0
ns
(7030.0 - 7480.0 ] ▏11
(7480.0 - 7930.0 ] █▍128
(7930.0 - 8380.0 ] ████████▏788
(8380.0 - 8830.0 ] █████████████████████▏2044
(8830.0 - 9280.0 ] ██████████████████████████████ 2916
(9280.0 - 9730.0 ] ███████████████████████▉2309
(9730.0 - 10180.0] ████████████▎1182
(10180.0 - 10630.0] ████▎413
(10630.0 - 11080.0] █▌140
(11080.0 - 11530.0] ▌44
(11530.0 - 11980.0] ▏6
(11980.0 - 12430.0] ▏3
(12430.0 - 12880.0] 0
(12880.0 - 13330.0] ▏5
(13330.0 - 18330.0] ▏11
Counts
min: 7.028 μs (0.00% GC); mean: 9.184 μs (0.00% GC); median: 9.153 μs (0.00% GC); max: 18.333 μs (0.00% GC).
See also https://tratt.net/laurie/blog/entries/minimum_times_tend_to_mislead_when_benchmarking.html for another example of where looking at the whole histogram can be useful in benchmarking.
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