Checkpoint 3

herding/flocking_sim.py

@@ -44,7 +44,7 @@ WALL_HARD_GAIN = 50.0
 
 FLEE_DIST = 7.0
 SEPARATION_DIST = 2.5
-COHESION_DIST = 8.0
+COHESION_DIST = 12.0    # was 8.0 — wider engagement so far-flung sheep are pulled in
 
 PEN_MARGIN = 0.8
 
@@ -125,12 +125,13 @@ def compute_heading_speed(x, y, penned, dog_xy, peers, wander_angle, rng=None):
                 cy += py
                 cn += 1
         if cn > 0:
-            # Cohesion needs to be comparable to flee at close range to keep
-            # the flock together through narrow obstacles like the 3m gate.
-            # Flee at 2m has magnitude ~10; cohesion at peer-distance 5m
-            # with w=1.5 contributes ~7.5 — same order, so the flock
-            # translates as a unit instead of fragmenting under pressure.
-            w = 1.5 if fleeing else 0.6
+            # Cohesion needs to dominate flee at close range so the flock
+            # stays glued together when squeezing through the narrow gate.
+            # Flee at 2 m has magnitude ~10; cohesion of w=3.0 with the
+            # peer-CoM 4 m away contributes ~12, so the flock prefers
+            # bunching to dispersing under pressure. This is what makes
+            # canonical Strömbom drive work in our 3 m gate.
+            w = 3.0 if fleeing else 1.0
             fx += (cx / cn - x) * w
             fy += (cy / cn - y) * w