Simplify tree with leaves error

[Florent Guiotte]

From time to time, depending on the criterion used, simplify_tree operating on leaves will trigger an assertion in tree constructor :

t = hg.Tree((7, 7, 8, 8, 8, 9, 9, 11, 10, 10, 11, 11))
criterion = np.zeros(t.num_vertices(), dtype=np.bool)
criterion[[5,6]] = True

new_tree, node_map = hg.simplify_tree(t, criterion, True)

RuntimeError: tree in file /tmp/pip-req-build-_gvhjvcf/include/higra/algo/../structure/tree_graph.hpp(line:135): leaves nodes are not before internal nodes

It may come from the tree remapping but I can't find any mistakes.

Higra/include/higra/hierarchy/hierarchy_core.hpp

Lines 175 to 186 in ec275ed

 for (auto i: leaves_to_root_iterator(t, leaves_it::include, root_it::exclude)) { 
     if (!criterion(i) || (!process_leaves && is_leaf(i, t))) { 
         auto par = copy_parent(i); 
         auto new_par = par - deleted_map(par); 
         node_map(count) = i; 
         new_parent(count) = new_par; 
         count++; 
     } 
 } 
  
 node_map(node_map.size() - 1) = root(t); 
 return make_remapped_tree(tree(new_parent, t.category()), std::move(node_map)); 

[Benjamin Perret]

OK, I see what is happening: the parent relation which is created by simplify_tree is valid but it does not satisfy a precondition of the Tree constructor (leaves must come first). This means that some reordering may append when some leaves are deleted.

I'll work on a patch asap. Thx for the clear bug report.

[Benjamin Perret]

@Karamaz0V1 If you need this urgently I can make a new release. Otherwise, I will wait a bit to add more things before creating version 0.4.3

[Florent Guiotte]

No problem, I build the latest version myself. Thank you very much for the quick fix!

[Florent Guiotte]

Sorry to report again!
Some cases are corrected by the last fix but there are still some problems. I was able to produce two RuntimeError:

t = hg.Tree((7, 7, 8, 8, 8, 9, 9, 11, 10, 10, 11, 11))
criterion = np.zeros(t.num_vertices(), dtype=np.bool)
criterion[:8] = True
new_tree, node_map = hg.simplify_tree(t, criterion, process_leaves=True)

RuntimeError: tree in file /tmp/pip-req-build-ag8hxpfh/include/higra/algo/../structure/tree_graph.hpp(line:126): several root nodes detected

and

criterion[:9] = True
new_tree, node_map = hg.simplify_tree(t, criterion, process_leaves=True)

RuntimeError: tree in file /tmp/pip-req-build-ag8hxpfh/include/higra/algo/../structure/tree_graph.hpp(line:122): nodes are not in a topological order (last node is not a root)

On the bright side, there is no problem when we first simplify the tree without the leaves, then remove the leaves as a second step.

[Benjamin Perret]

Sorry, you are right, leaves removal are tricky and I missed a case !