Topic: Losses of synchronisation with mismatching convoy debug sums

[freddyhayward]

In my record of desyncs currently from 12/9/20-17/9/20, nearly ~60% (currently 17) have had the convoy debug sums mismatching (and all other checklist records matching perfectly).
The first (debug_sum[0]) is updated by adding the mantissa of some floating point value when each convoy is processed.
The second (debug_sum[1]) is the same but multiplied with the internal ID of the convoy. In all cases, the first and the second were mismatched together, but I wasn't able to discern the internal ID of the offending convoy(s) in any case.

https://docs.google.com/spreadsheets/d/1Jwa-5G6aXfkrCrPYLQvDbYt7LqYMgYapW8hyOF9IB3s/edit#gid=0

[freddyhayward]

As of now, there have been 35 recorded desyncs (of the total 70) with debug_sum[0] mismatching. What I have found is that these sums overflow so frequently between each check that it is almost always impossible to determine the unsynchronised convoy, assuming there is only one. I've made a change that significantly reduces the size of these sums so that they should be easier to investigate, here: https://github.com/jamespetts/simutrans-extended/pull/285

[jamespetts]

Thank you for your work on this: I have now incorporated your debugging change.

There are such a wide range of things that might cause a code divergence first to manifest itself in a difference in convoy movement that any additional information or precision is likely to be useful.