Thanks, this can get indeed a better description. Let me try and ask if still unclear:
max_weight_factor – the maximum weight of the return routes, in comparison to the best route.
Valid values >=1
Default value = 1.4
Exactly, ie. how much larger can the alternatives be?
max_share_factor – The max overlap between returned routes
Valid values between 0 and 1
Default value = 0.6
max_share_factor is the maximum allowed distance (in reality it is the more generic ‘weight’) that alternative paths can share with the best route
max_paths – the maximum number of returned path
Valid values >=2
Default value = 2
Exactly. Valid >= 2 because if just 1 the user should not use alternative route calculation due to the overhead
min_plateau_factor - ???
Default value = 0.2
Similar to the max_share_factor this is also special to the algorithm and defines the minimum distance (again better: ‘weight’) that a branch from the source SPT must share with the destination SPT. See this image and the blog post with some more insights about ‘SPTs’ (shortest path trees)
max_exploration_factor - ???
Default value = 1
When the best path is found the algorithm could theoretically stop immediately but you can increase this value and more (but potentially worse) alternatives could be found
Also note that in the latest master (and since RC1) the default value has changed for this to 0.8, as we use bidirectional A* and alternatives of the same quality are found with less exploration