AF Analysis returns "List of supplied times must be monotonic"

Discussion created by VCampus-METCO on Sep 12, 2020

I have a PIPoint triggered analysis which takes as input a formula Data Reference result, and writes that result to an output PIPoint if the value is > x. The trigger tag writes a value every 15 minutes.


The input formula in turn refers to an attribute which is a PIPoint Summary and which calculates a time-weighted average using a relative time of -15m.


When I try to do a preview/backill, for say 1 hour, I get a result row for each trigger time, i.e. at 00:00, 00:15, 00:30, 00:45, but an error when getting the result of my input formula "The list of supplied times must be monotonic".


I have looked in Tech Support to see what this means but cannot see anything. I am assuming that it means the timestamps provided to evaluate the formula are not in ascending order. Would this be correct?


In AFTrace I see calls to GetEvents for two separate streams, the trigger tag and formula attribute. Then 11 calls to GetSummary for the same stream (presumably my formula attribute). I am not sure why there are 11 calls when there are only 4 trigger events. And then finally another GetEvents call for a different stream altogether - possibly the output PIPoint?


So my expectation is that when I ask to backfill 1 hour of my analysis and there are 4 trigger events that the input formula will be evaluated using the trigger time as its context.


Can anyone please confirm whether my understading is correct? I realise that a formula in itself is not historised but that when it is evaluated it must be given a time context of some sort for evaluation.