Small diffs during warmup in Economizer regression test

[tanaya-mankad]

During an effort to replace two independent load ratio variables with one consolidated ratio in the Unitary class, we uncovered a single regression difference in the file UnitarySystem_MultiSpeedDX_EconoStaging.idf, where humidity ratios for some systems (System 2 shown below) are off for just the warmup period.

Diffs shown can be reproduced between SHAs fe2fc3c (branch) and 31e3c33 (develop), The PR discussion is summarized below:

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@tanaya-mankad tanaya-mankad on Dec 10, 2024
Thanks @rraustad for finding that fallacy! Unfortunately it doesn't seem to affect the result. I'm attaching a couple of comparison plots - the top plot is the Max Absolute Difference, with red showing the difference on the left scale. The bottom plot is the Max Relative Difference, with red pointing to the right scale. The location is always on Jan 1.
(The second png is just zoomed way in.) In case it gives us any more info.

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@rraustad rraustad on Dec 10, 2024
Which example file is this?

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@tanaya-mankad tanaya-mankad on Dec 10, 2024
UnitarySystem_MultiSpeedDX_EconoStaging.idf
The regressions are here (please don't mind the build problems, apparently it's due to this being a branch on the Big Ladder fork.)

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@rraustad rraustad on Dec 11, 2024
Now I see the same thing you see. The question is if this is due to the changes you made. It's so small it's almost not worth looking into, almost.

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@tanaya-mankad tanaya-mankad on Dec 11, 2024
Yes, it's tiny! I'd defer to your judgement on whether it's significant. I'm not sure what counts as a "big diff" in regression testing, but 10e-5 relative difference during warmup seems quite difficult to find.

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@rraustad rraustad on Dec 11, 2024
This example file came from #9987 and is the only file with local diffs. I think these diffs come from a different OA flow rate at the beginning of the simulation, and for all 4 systems in this file, but I can't see why changing the call to the coil model would affect the calculation for economizer PLR. There are no eio diffs and no warmup diffs but diffs in the eso so it is operational.