diff --git a/requirements.txt b/requirements.txt
index f16aacc2..8e407161 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,4 @@
-Jinja2==2.10.3
+Jinja2==2.11.3
 numpy==1.17.4
 tensorboardX==1.6
 torch==1.4.0
diff --git a/spert/sampling.py b/spert/sampling.py
index 26386b2c..0256c6a0 100644
--- a/spert/sampling.py
+++ b/spert/sampling.py
@@ -19,12 +19,26 @@ def create_train_sample(doc, neg_entity_count: int, neg_rel_count: int, max_span
         pos_entity_sizes.append(len(e.tokens))
 
     # positive relations
-    pos_rels, pos_rel_spans, pos_rel_types, pos_rel_masks = [], [], [], []
+
+    # collect relations between entity pairs
+    entity_pair_relations = dict()
     for rel in doc.relations:
-        s1, s2 = rel.head_entity.span, rel.tail_entity.span
+        pair = (rel.head_entity, rel.tail_entity)
+        if pair not in entity_pair_relations:
+            entity_pair_relations[pair] = []
+        entity_pair_relations[pair].append(rel)
+
+    # build positive relation samples
+    pos_rels, pos_rel_spans, pos_rel_types, pos_rel_masks = [], [], [], []
+    for pair, rels in entity_pair_relations.items():
+        head_entity, tail_entity = pair
+        s1, s2 = head_entity.span, tail_entity.span
         pos_rels.append((pos_entity_spans.index(s1), pos_entity_spans.index(s2)))
         pos_rel_spans.append((s1, s2))
-        pos_rel_types.append(rel.relation_type)
+
+        pair_rel_types = [r.relation_type.index for r in rels]
+        pair_rel_types = [int(t in pair_rel_types) for t in range(1, rel_type_count)]
+        pos_rel_types.append(pair_rel_types)
         pos_rel_masks.append(create_rel_mask(s1, s2, context_size))
 
     # negative entities
@@ -50,14 +64,10 @@ def create_train_sample(doc, neg_entity_count: int, neg_rel_count: int, max_span
 
     for i1, s1 in enumerate(pos_entity_spans):
         for i2, s2 in enumerate(pos_entity_spans):
-            rev = (s2, s1)
-            rev_symmetric = rev in pos_rel_spans and pos_rel_types[pos_rel_spans.index(rev)].symmetric
-
             # do not add as negative relation sample:
             # neg. relations from an entity to itself
             # entity pairs that are related according to gt
-            # entity pairs whose reverse exists as a symmetric relation in gt
-            if s1 != s2 and (s1, s2) not in pos_rel_spans and not rev_symmetric:
+            if s1 != s2 and (s1, s2) not in pos_rel_spans:
                 neg_rel_spans.append((s1, s2))
 
     # sample negative relations
@@ -65,7 +75,7 @@ def create_train_sample(doc, neg_entity_count: int, neg_rel_count: int, max_span
 
     neg_rels = [(pos_entity_spans.index(s1), pos_entity_spans.index(s2)) for s1, s2 in neg_rel_spans]
     neg_rel_masks = [create_rel_mask(*spans, context_size) for spans in neg_rel_spans]
-    neg_rel_types = [0] * len(neg_rel_spans)
+    neg_rel_types = [(0,) * (rel_type_count-1)] * len(neg_rel_spans)
 
     # merge
     entity_types = pos_entity_types + neg_entity_types
@@ -73,7 +83,7 @@ def create_train_sample(doc, neg_entity_count: int, neg_rel_count: int, max_span
     entity_sizes = pos_entity_sizes + list(neg_entity_sizes)
 
     rels = pos_rels + neg_rels
-    rel_types = [r.index for r in pos_rel_types] + neg_rel_types
+    rel_types = pos_rel_types + neg_rel_types
     rel_masks = pos_rel_masks + neg_rel_masks
 
     assert len(entity_masks) == len(entity_sizes) == len(entity_types)
@@ -105,23 +115,18 @@ def create_train_sample(doc, neg_entity_count: int, neg_rel_count: int, max_span
     if rels:
         rels = torch.tensor(rels, dtype=torch.long)
         rel_masks = torch.stack(rel_masks)
-        rel_types = torch.tensor(rel_types, dtype=torch.long)
+        rel_types = torch.tensor(rel_types, dtype=torch.float32)
         rel_sample_masks = torch.ones([rels.shape[0]], dtype=torch.bool)
     else:
         # corner case handling (no pos/neg relations)
         rels = torch.zeros([1, 2], dtype=torch.long)
-        rel_types = torch.zeros([1], dtype=torch.long)
+        rel_types = torch.zeros([1, rel_type_count-1], dtype=torch.float32)
         rel_masks = torch.zeros([1, context_size], dtype=torch.bool)
         rel_sample_masks = torch.zeros([1], dtype=torch.bool)
 
-    # relation types to one-hot encoding
-    rel_types_onehot = torch.zeros([rel_types.shape[0], rel_type_count], dtype=torch.float32)
-    rel_types_onehot.scatter_(1, rel_types.unsqueeze(1), 1)
-    rel_types_onehot = rel_types_onehot[:, 1:]  # all zeros for 'none' relation
-
     return dict(encodings=encodings, context_masks=context_masks, entity_masks=entity_masks,
                 entity_sizes=entity_sizes, entity_types=entity_types,
-                rels=rels, rel_masks=rel_masks, rel_types=rel_types_onehot,
+                rels=rels, rel_masks=rel_masks, rel_types=rel_types,
                 entity_sample_masks=entity_sample_masks, rel_sample_masks=rel_sample_masks)