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Fix Hodges-Lehmann distribution ratio calculation #111

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@mgrzaslewicz mgrzaslewicz commented Jul 22, 2024

I hoped to see classification change for added distribution. As it should be detected as an improvement, while in production we have no impact:
image

However previous classification was fine for default tolerance. We're just using a different production tolerance in RegressionCheckIT and improvement is below threshold.
So at least we have a properly calculated Hodges-Lehmann coming with this change.

@@ -2,7 +2,7 @@ package com.atlassian.performance.tools.report.api.judge

import com.atlassian.performance.tools.jiraactions.api.ActionType
import com.atlassian.performance.tools.report.ActionMetricsReader
import com.atlassian.performance.tools.report.api.ShiftedDistributionRegressionTest
import com.atlassian.performance.tools.report.api.distribution.DistributionComparator
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No difference detected by RelativeNonparametricPerformanceJudgeTest?

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No diff here

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So we don't see why the new one is better.

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How do you define better? Classification has not changed for unit tested cases and as stated in first PR comment, it's expected

values[k++] = func(baseline[i], experiment[j])
}
}
return Median().withNaNStrategy(NaNStrategy.MINIMAL).evaluate(values)
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When used on a set of latency measurements, why would we inject fake negative infinities?

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@mgrzaslewicz mgrzaslewicz Jul 22, 2024

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It's needed for cases when part of the distribution is the same and other part is different. Without it small difference will be calculated as whole distribution difference and instead of NaN you will get -0.45623836126629425 in attached example
image

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@dagguh dagguh Jul 22, 2024

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Yes, but the workaround injects fake extreme values. Both "before" and "after" seem wrong.
PS. this case is untested, right?

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The only value of this PR is to have a relativeShift correctly calculated, it does not improve classification as I hoped. I will prepare a small PR to fix ShiftedDistributionRegressionTest and decline this one

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2 participants