Speed up CTC edge errors

When calculating edge errors, there is a 1-to-1 mapping between computed
graph nodes and GT graph nodes, see details below.

It is faster to use a dictionary for doing the node mapping with O(n
log(n)) runtime, compared to repeatedly iterating over a list with
np.where (O(n^2)).

Details: Potential 1-to-many matches, namely computed nodes that match multiple
GT nodes (called non-split), are not part of the induced graph.
Therefore, all edges incident to such nodes are also not part of the induced
graph, leaving us with the desired 1-to-1 mapping for all nodes that are
incident to existing edges in the induced graph, which we iterate over
in the loop for finding FP edges.

Conversely, each GT node is only matched to at most one computed node,
directly yielding the 1-1 matching for finding FN edges.

src/traccuracy/track_errors/_ctc.py

@@ -2,7 +2,6 @@
 from collections import defaultdict
 from typing import TYPE_CHECKING
 
-import numpy as np
 from tqdm import tqdm
 
 from traccuracy import EdgeAttr, NodeAttr
@@ -91,15 +90,15 @@ def get_edge_errors(matched_data: "Matched"):
     )
     gt_graph.set_edge_attribute(list(gt_graph.edges()), EdgeAttr.FALSE_NEG, False)
 
-    node_mapping_first = np.array([mp[0] for mp in node_mapping])
-    node_mapping_second = np.array([mp[1] for mp in node_mapping])
+    node_mapping_first = {mp[0]: mp[1] for mp in node_mapping}
+    node_mapping_second = {mp[1]: mp[0] for mp in node_mapping}
 
     # fp edges - edges in induced_graph that aren't in gt_graph
     for edge in tqdm(induced_graph.edges, "Evaluating FP edges"):
         source, target = edge[0], edge[1]
 
-        source_gt_id = node_mapping[np.where(node_mapping_second == source)[0][0]][0]
-        target_gt_id = node_mapping[np.where(node_mapping_second == target)[0][0]][0]
+        source_gt_id = node_mapping_second[source]
+        target_gt_id = node_mapping_second[target]
 
         expected_gt_edge = (source_gt_id, target_gt_id)
         if expected_gt_edge not in gt_graph.edges():
@@ -124,8 +123,8 @@ def get_edge_errors(matched_data: "Matched"):
             gt_graph.set_edge_attribute(edge, EdgeAttr.FALSE_NEG, True)
             continue
 
-        source_comp_id = node_mapping[np.where(node_mapping_first == source)[0][0]][1]
-        target_comp_id = node_mapping[np.where(node_mapping_first == target)[0][0]][1]
+        source_comp_id = node_mapping_first[source]
+        target_comp_id = node_mapping_first[target]
 
         expected_comp_edge = (source_comp_id, target_comp_id)
         if expected_comp_edge not in induced_graph.edges: