Correct usage of euclidean distances in motmetrics.utils.compare_to_groundtruth()

[angelcarro]

Use euclidean distance instead of squared euclidean distance in motmetrics.utils.compare_to_groundtruth(). This way, the MOTP metric provides the expected mean distance.
The squared distance can still be used with option dist='seuc'.
#161

[cheind]

Thanks, looks good to me. Any expected side-effects to be expected? Backward compatibility?

[angelcarro]

There are backward compatibility issues. If someone used the method with dist='euc' and was assuming squared euclidean distance, he/she should change to dist='seuc'.

[cheind]

thanks

[cheind]

is there additional need to update the readme?

[angelcarro]

Hi. I was thinking a way to mitigate the backward compatibility issues as there are some repositories that use the squared euclidean threshold such as:
https://github.com/smidm/motutils/blob/505d8359d4856c3cda7a3cf6acd4690c2dfe32d6/motutils/io.py#L297
https://github.com/iccv2021-mmp/mmp-tracking-helper/blob/d816fd04e7c896d39ac4ddc413f59318095c566b/mmp_topdown_evaluate.py#L32

I think we should add a warning when the 'euc' distance is used, suggesting to change the parameter call to dist='euc_norm' (new option) or to dist='seuc'.