From 4809ea777c02583ce4689d038645ee1ba773a261 Mon Sep 17 00:00:00 2001
From: Tanay Sanghvi <tsanghv1@jh.edu>
Date: Mon, 10 Aug 2026 10:57:04 +0530
Subject: [PATCH 1/2] Fix multimer interface residue detection with memory
 optimization

---
 openfold/data/data_transforms_multimer.py | 53 ++++++++++++++++++-----
 1 file changed, 41 insertions(+), 12 deletions(-)

diff --git a/openfold/data/data_transforms_multimer.py b/openfold/data/data_transforms_multimer.py
index fcdfb3d7b..e500b113f 100644
--- a/openfold/data/data_transforms_multimer.py
+++ b/openfold/data/data_transforms_multimer.py
@@ -318,19 +318,48 @@ def randint(lower, upper, generator, device):
 
 
 def get_interface_residues(positions, atom_mask, asym_id, interface_threshold):
-    coord_diff = positions[..., None, :, :] - positions[..., None, :, :, :]
-    pairwise_dists = torch.sqrt(torch.sum(coord_diff ** 2, dim=-1))
-
-    diff_chain_mask = (asym_id[..., None, :] != asym_id[..., :, None]).float()
-    pair_mask = atom_mask[..., None, :] * atom_mask[..., None, :, :]
-    mask = (diff_chain_mask[..., None] * pair_mask).bool()
-
-    min_dist_per_res, _ = torch.where(mask, pairwise_dists, torch.inf).min(dim=-1)
-
-    valid_interfaces = torch.sum((min_dist_per_res < interface_threshold).float(), dim=-1)
-    interface_residues_idxs = torch.nonzero(valid_interfaces, as_tuple=True)[0]
+    num_res = positions.shape[0]
+    chunk_size = 64
+    atom_mask = atom_mask.bool()
+    interface_mask = torch.zeros(
+        num_res,
+        dtype=torch.bool,
+        device=positions.device,
+    )
 
-    return interface_residues_idxs
+    for query_start in range(0, num_res, chunk_size):
+        query_end = min(query_start + chunk_size, num_res)
+        query_positions = positions[query_start:query_end]
+        query_atom_mask = atom_mask[query_start:query_end]
+        query_asym_id = asym_id[query_start:query_end]
+
+        for key_start in range(0, num_res, chunk_size):
+            key_end = min(key_start + chunk_size, num_res)
+            key_positions = positions[key_start:key_end]
+            key_atom_mask = atom_mask[key_start:key_end]
+            key_asym_id = asym_id[key_start:key_end]
+
+            pairwise_dists = torch.cdist(
+                query_positions[:, None, :, :],
+                key_positions[None, :, :, :],
+            )
+            diff_chain_mask = (
+                query_asym_id[:, None] != key_asym_id[None, :]
+            )[:, :, None, None]
+            pair_mask = (
+                query_atom_mask[:, None, :, None]
+                & key_atom_mask[None, :, None, :]
+            )
+            contacts = (
+                (pairwise_dists < interface_threshold)
+                & diff_chain_mask
+                & pair_mask
+            )
+            interface_mask[query_start:query_end] |= contacts.any(
+                dim=(1, 2, 3)
+            )
+
+    return torch.nonzero(interface_mask, as_tuple=True)[0]
 
 
 def get_spatial_crop_idx(protein, crop_size, interface_threshold, generator):

From 2939f87263defcb747b97ac977feca4e47842bbc Mon Sep 17 00:00:00 2001
From: Tanay Sanghvi <tsanghv1@jh.edu>
Date: Mon, 10 Aug 2026 11:43:51 +0530
Subject: [PATCH 2/2] Add unit regression test for multimer interface detection

---
 tests/test_data_transforms.py | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/tests/test_data_transforms.py b/tests/test_data_transforms.py
index 7da735654..c7e12c09c 100644
--- a/tests/test_data_transforms.py
+++ b/tests/test_data_transforms.py
@@ -9,6 +9,8 @@
     correct_msa_restypes, squeeze_features, randomly_replace_msa_with_unknown, MSA_FEATURE_NAMES, sample_msa, \
     crop_extra_msa, delete_extra_msa, nearest_neighbor_clusters, make_msa_mask, make_hhblits_profile, make_masked_msa, \
     make_msa_feat, crop_templates, make_atom14_masks
+from openfold.data.data_transforms_multimer import get_interface_residues
+from openfold.np import residue_constants as rc
 from tests.config import config
 
 
@@ -221,6 +223,39 @@ def test_make_atom14_masks(self):
         assert 'residx_atom37_to_atom14' in protein
         assert 'atom37_atom_exists' in protein
 
+    def test_get_interface_residues(self):
+        positions = torch.zeros((2, rc.atom_type_num, 3))
+        atom_mask = torch.zeros((2, rc.atom_type_num))
+        asym_id = torch.tensor([0, 1])
+
+        lys_nz_idx = rc.atom_order["NZ"]
+        asp_od1_idx = rc.atom_order["OD1"]
+        positions[0, lys_nz_idx] = torch.tensor([0., 0., 0.])
+        positions[1, asp_od1_idx] = torch.tensor([1., 0., 0.])
+        atom_mask[0, lys_nz_idx] = 1.
+        atom_mask[1, asp_od1_idx] = 1.
+
+        interface_residues = get_interface_residues(
+            positions,
+            atom_mask,
+            asym_id,
+            interface_threshold=2.,
+        )
+
+        self.assertTrue(
+            torch.equal(interface_residues, torch.tensor([0, 1]))
+        )
+
+        positions[1, asp_od1_idx] = torch.tensor([3., 0., 0.])
+        interface_residues = get_interface_residues(
+            positions,
+            atom_mask,
+            asym_id,
+            interface_threshold=2.,
+        )
+
+        self.assertEqual(interface_residues.numel(), 0)
+
 
 if __name__ == '__main__':
     unittest.main()