mathiasbynens / jsperf.com

jsPerf.com source code
http://jsperf.com/
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Wrong “fastest” labels #195

Closed RubenVerborgh closed 9 years ago

RubenVerborgh commented 9 years ago

A recent test gave me the following result:

while that should have been

screen shot 2014-10-03 at 20 04 37

jdalton commented 9 years ago

The margin of errors are what make the difference here. The ones highlighted are the fastest discounting their margin of errors.

RubenVerborgh commented 9 years ago

Thanks for explaining, but that doesn't explain everything I think. I subtracted the margin of errors:

So seems it should still be A & B.

jdalton commented 9 years ago

Hmm, I'll review that bit in the code. Would you share the jsperf test you saw this on.

RubenVerborgh commented 9 years ago

It was this one: http://jsperf.com/unknown-hash-key/2

jdalton commented 9 years ago

For some insight into our process we sort based on mean + moe but then run them through compare to perform a Mann-Whitney U test on them.

jdalton commented 9 years ago

If you can reproduce this again after your run would you open your web console and do ui.benchmarks.map(function(b){return JSON.stringify(b.stats,null,2)}) then paste the output into a gist and report back.

RubenVerborgh commented 9 years ago

Tried a few times but haven't been able to reproduce… I suppose the above numbers and percentages are insufficient to make this into a unit test?

jdalton commented 9 years ago

Tried a few times but haven't been able to reproduce…

If you see it show up again then, no worries.

I suppose the above numbers and percentages are insufficient to make this into a unit test?

Right, we'd need the full stats record to be able to dig into it and see what's up.