1 files changed, 10 insertions, 4 deletions
diff --git a/worldalign/anchor_bound.py b/worldalign/anchor_bound.py
index 49f4ed3..2920934 100644
--- a/worldalign/anchor_bound.py
+++ b/worldalign/anchor_bound.py
@@ -79,13 +79,19 @@ def analyse(path: str, label: str, repeats: int, blind: float | None) -> dict:
         order = generator.permutation(size)
         half = size // 2
         anchors, probe = order[:half], order[half:]
+        # The two sides must not be presented in the same index order. Exact
+        # twins have identical anchor-restricted rows, and with matched
+        # ordering `linear_sum_assignment` breaks the tie onto the diagonal --
+        # crediting the bound with information it does not have. On the
+        # caption-omitted field that inflated it from 0.920 to 0.997.
+        order = generator.permutation(len(probe))
         left = rows_against(visual, probe, anchors)
-        right = rows_against(text, probe, anchors)
+        right = rows_against(text, probe[order], anchors)
         similarity = left @ right.T / left.shape[1]
-        truth = np.arange(len(probe))
-        nearest.append(float((similarity.argmax(1) == truth).mean()))
+        truth = order
+        nearest.append(float((order[similarity.argmax(1)] == np.arange(len(probe))).mean()))
         _, columns = linear_sum_assignment(-similarity)
-        assigned.append(float((columns == truth).mean()))
+        assigned.append(float((order[columns] == np.arange(len(probe))).mean()))
 
     row = {
         "label": label,