Fix bug in thor_worker_t::build_trace on wrong edge_index assignment

[mahdihasnat]

Issue

#fixes #3633

Tasklist

• Add tests
• Add #fixes with the issue number that this PR addresses
• Update the docs with any new request parameters or changes to behavior described
• Update the changelog
• If you made changes to the lua files, update the taginfo too.

Requirements / Relations

Link any requirements here. Other pull requests this PR is based on?

[nilsnolde]

Your fork was 60 commits behind ;)

[mahdihasnat]

Yes, I tested it on top of release 3.4.0. I will merge this with master and push here.

Thanks you merged already

[nilsnolde]

Ah ok. Always always test with master, never a release.

[mahdihasnat]

I have tested current master with the around 2000 trace_attribute request. Didn't face the issue.

[nilsnolde]

Great thanks for the feedback! Just needs a quick look by someone more familiar with map matching than me, I’m sure it’s fine:)

Could you do a quick changelog entry as well? At the bottom of the unreleased FIXED section would be great

[mahdihasnat]

I have updated the changelog.
Thanks a lot.

[mahdihasnat]

Hi @nilsnolde ,
I found another issue around edge_index assignment.
Lets say we have a path having edgeid = (0,0,0,1,1,2,3)
Current flow for edge_index calculation:

last_id = invalid id
edge_index = 0
for segment in paths
  // assign match_results array with current edge_index
  if (last_id != segment.edgeid)
    edge_index ++
  last_id = segment.edgeid

Following is the edge_index assigned for each segment:

edgeId	0	0	0	1	1	2	3
mismatch with previous edgeid at end of the loop	1	0	0	1	0	1	1
edge_index at beginning of the loop	0	1	1	1	2	2	3
correct edge_index at beginning of the loop	0	0	0	1	1	2	3

I propose the following logic for edge_index assignment:

last_id = invalid id
edge_index = 0
for segment in paths
  if (last_id != segment.edgeid && last_id.Is_Valid())
    edge_index ++
  // assign match_results array with current edge_index
  last_id = segment.edgeid

[mahdihasnat]

Or even more performant logic:

last_id = invalid id
edge_index = -1
for segment in paths
  if (last_id != segment.edgeid)
    edge_index ++
  // assign match_results array with current edge_index
  last_id = segment.edgeid

[kevinkreiser]

feel free to apply your other change as well and i can give you a review in the next few days

[kevinkreiser]

this looks good to me, can you change that edge_index variable back to size_t and we can merge

[mahdihasnat]

Yes, working on it