Andreas Stefl

after looking into this I think this problem is produced by the vertex fitting if we have a bunch of similar tracks. in our full chain example we do not...

should we close @paulgessinger ?

If we want to track the documentation in this PR we should at least link it in the code since git history is a bit loose after a following change...

this seems to have some impact on https://github.com/acts-project/acts/issues/1385#issuecomment-1217968896 do you think we can get this in in the near future? @beomki-yeo @paulgessinger it looks like some reference tests are failing...

I can look into this next week

I lately made the effort of compiling it so I would like to try running it as long as my CPU does not throttle :smile:

> FATRAS: > 16:54:01 FatrasSimula ERROR event 571 particle id=(82|134|591|0|0)|pdg=0|q=-1|m=0|p=11.5181 failed to simulate with error PropagatorError:3: Propagation reached the configured maximum number of steps. > This could be a navigation...

> 16:51:54 TrackFinding ERROR Propapation failed: EigenStepperError:3 Step size adjustment exceeds maximum trials with the initial parameters 33554 : the "good" news is that all of them seem to have...

after running fatras again I see particles without `pdg != 0`. actually didn't spot any with `0` ``` 11:51:27 FatrasSimula ERROR event 2 particle id=(80|0|14|0|0)|pdg=pi-|q=-1|m=0.13957|p=15.0429 failed to simulate with error...

the propagation in fatras is flip-flopping between +/- some small value `EigenStepper: updateStepSize` corresponds to https://github.com/acts-project/acts/blob/main/Core/include/Acts/Propagator/EigenStepper.hpp#L262 `EigenStepper: step` corresponds to https://github.com/acts-project/acts/blob/main/Core/include/Acts/Propagator/EigenStepper.ipp#L117 ``` EigenStepper: updateStepSize -0.0289624 EigenStepper: step (748.218, -0.0289624, 76816.8,...