Bug 15482

Summary: oe-build-perf-report: Stdev displayed as 'nan'
Product: [Build System, Metadata & Runtime] OE-Core Reporter: ninette
Component: Scripts and ToolsAssignee: Randy MacLeod <randy.macleod>
Status: NEW --- QA Contact:
Severity: normal    
Priority: Medium CC: randy.macleod, ross.burton
Version: unspecified   
Target Milestone: 6.2   
Hardware: x86   
OS: Multiple   
Whiteboard:
OS type for building Yocto: --- Type of Regression: ---
Verified: Documentation change: No (bug/feature does not impact docs)
Attachments:
Description Flags
Build time chart showing Stdev as 'nan' and minus/plus as 0.00 none

Description ninette 2024-05-13 14:23:21 UTC 
Created attachment 5045 [details]
Build time chart showing Stdev as 'nan' and minus/plus as 0.00

For the charts in the html report generated by oe-build-perf-report, some of the commits show the value of standard deviation (Stdev) as 'nan' and the minus, plus as zero.

I think this is where the 'nan' error is being generated. https://git.yoctoproject.org/poky/tree/scripts/lib/build_perf/report.py#n331

Here is an example of the report which shows the incorrect values:

Performance test report HTML: https://autobuilder.yocto.io/pub/non-release/20240502-21/testresults/buildperf-alma8/perf-alma8_master_20240502150054_632e317059.html

Expectation is to show the correct values for Stdev and minus/plus instead of 'nan' and zeroes.
Comment 1 Randy MacLeod 2024-05-16 14:41:00 UTC 
The NaN seems to be a case where there is only one datapoint.
We can lie and claim that the StdDev is 0.