core(metrics): add lantern speed index #4695
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This was referenced Mar 9, 2018
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OK folks FYI I've updated this and it's ready for review! |
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friendly reminder here that I/O-Expedite policy has this currently auto-merging at 2pm today folks ;) |
paulirish
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| * @param {number} fcpTimeInMs | ||
| * @return {number} | ||
| */ | ||
| static computeLayoutBasedSpeedIndex(nodeTiming, fcpTimeInMs) { |
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can you add some documentation that explains the approach here?
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closes #4639
blocked from merging on #4966
predicts speed index by using the real speed index as the optimistic estimate and a layout-based speed index approximation from the pessimistic TTI graph as the pessimistic estimate
accuracy is decent. probably wouldn't recommend making it a headline metric as-is, but correlates slightly better than FCP (less than TTI/TTFCPUI)
spearman's rho ~.78, MAPE ~47%