Add uniform symdiff selection and store symdiff in graph edges

- Add symdiff to edge tuple in _find_valid_edges() and store in graph
- Add --uniform-symdiff CLI option to make symdiff selection uniform
- Implement uniform selection in pathfinder by grouping edges by symdiff
- With uniform: path uses symdiff 2 and 4 roughly equally
- Without uniform: path uses mostly symdiff 4 (most common)

src/harmonic_space.py

@@ -160,6 +160,7 @@ class HarmonicSpace:
                     cent_diffs,
                     voice_crossing,
                     is_directly_tunable,
+                    symdiff,
                 ) = edge_data
                 graph.add_edge(
                     c1,
@@ -170,6 +171,7 @@ class HarmonicSpace:
                     cent_diffs=cent_diffs,
                     voice_crossing=voice_crossing,
                     is_directly_tunable=is_directly_tunable,
+                    symdiff=symdiff,
                 )
 
             # Compute c2 -> c1 independently
@@ -182,6 +184,7 @@ class HarmonicSpace:
                     cent_diffs,
                     voice_crossing,
                     is_directly_tunable,
+                    symdiff,
                 ) = edge_data
                 graph.add_edge(
                     c2,
@@ -192,6 +195,7 @@ class HarmonicSpace:
                     cent_diffs=cent_diffs,
                     voice_crossing=voice_crossing,
                     is_directly_tunable=is_directly_tunable,
+                    symdiff=symdiff,
                 )
 
         return graph
@@ -318,6 +322,7 @@ class HarmonicSpace:
                         cent_diffs,
                         voice_crossing,
                         is_directly_tunable,
+                        symdiff,
                     )
                 )
 

src/io.py

@@ -408,6 +408,11 @@ def main():
         default=1,
         help="Weight for target register factor (0=disabled, default: 1)",
     )
+    parser.add_argument(
+        "--uniform-symdiff",
+        action="store_true",
+        help="Make symdiff selection uniform across range (ignore weight differences)",
+    )
     parser.add_argument(
         "--dims", type=int, default=7, help="Number of prime dimensions (4, 5, 7, or 8)"
     )
@@ -614,6 +619,9 @@ def main():
     else:
         weights_config["weight_target_register"] = 0  # disabled
 
+    # Uniform symdiff selection
+    weights_config["uniform_symdiff"] = args.uniform_symdiff
+
     weights_config["max_path"] = args.max_path
 
     path_obj = path_finder.find_stochastic_path(

src/pathfinder.py

@@ -54,6 +54,21 @@ class PathFinder:
             if not out_edges:
                 break
 
+            # Group edges by symdiff for uniform selection
+            edges_by_symdiff = {}
+            for edge in out_edges:
+                symdiff = edge[2].get("symdiff", 0)
+                if symdiff not in edges_by_symdiff:
+                    edges_by_symdiff[symdiff] = []
+                edges_by_symdiff[symdiff].append(edge)
+
+            # If uniform_symdiff, pick symdiff uniformly then use those edges
+            if weights_config.get("uniform_symdiff") and edges_by_symdiff:
+                import random
+
+                chosen_symdiff = random.choice(list(edges_by_symdiff.keys()))
+                out_edges = edges_by_symdiff[chosen_symdiff]
+
             # Build candidates using Path's state and factor methods
             candidates = path_obj.get_candidates(out_edges, path_obj.output_chords)