Add extra batch util

spacy/util.py

@@ -722,6 +722,50 @@ def minibatch(items, size=8):
         yield list(batch)
 
 
+def minibatch_by_padded_size(docs, size, buffer=256, discard_oversize=False):
+    if isinstance(size, int):
+        size_ = itertools.repeat(size)
+    else:
+        size_ = size
+    for outer_batch in minibatch(docs, buffer):
+        outer_batch = list(outer_batch)
+        target_size = next(size_)
+        for indices in _batch_by_length(outer_batch, target_size):
+            subbatch = [outer_batch[i] for i in indices]
+            padded_size = max(len(seq) for seq in subbatch) * len(subbatch)
+            if discard_oversize and padded_size >= target_size:
+                pass
+            else:
+                yield subbatch
+ 
+
+def _batch_by_length(seqs, max_words):
+    """Given a list of sequences, return a batched list of indices into the 
+    list, where the batches are grouped by length, in descending order.
+    
+    Batches may be at most max_words in size, defined as max sequence length * size.
+    """
+    # Use negative index so we can get sort by position ascending.
+    lengths_indices = [(len(seq), i) for i, seq in enumerate(seqs)]
+    lengths_indices.sort()
+    batches = []
+    batch = []
+    for length, i in lengths_indices:
+        if not batch:
+            batch.append(i)
+        elif length * (len(batch) + 1) <= max_words:
+            batch.append(i)
+        else:
+            batches.append(batch)
+            batch = [i]
+    if batch:
+        batches.append(batch)
+    # Check lengths match
+    assert sum(len(b) for b in batches) == len(seqs)
+    batches = [list(sorted(batch)) for batch in batches]
+    batches.reverse()
+    return batches
+
 def minibatch_by_words(docs, size, tolerance=0.2, discard_oversize=False):
     """Create minibatches of roughly a given number of words. If any examples
     are longer than the specified batch length, they will appear in a batch by
@@ -768,7 +812,8 @@ def minibatch_by_words(docs, size, tolerance=0.2, discard_oversize=False):
 
         # yield the previous batch and start a new one. The new one gets the overflow examples.
         else:
-            yield batch
+            if batch:
+                yield batch
             target_size = next(size_)
             tol_size = target_size * tolerance
             batch = overflow
@@ -788,15 +833,15 @@ def minibatch_by_words(docs, size, tolerance=0.2, discard_oversize=False):
 
             # this example does not fit with the previous overflow: start another new batch
             else:
-                yield batch
+                if batch:
+                    yield batch
                 target_size = next(size_)
                 tol_size = target_size * tolerance
                 batch = [doc]
                 batch_size = n_words
 
-    # yield the final batch
+    batch.extend(overflow)
     if batch:
-        batch.extend(overflow)
         yield batch