add mixup variant of batchize

onn/utility.py

@@ -63,6 +63,36 @@ def batchize(inputs, outputs, batch_size, shuffle=True):
     return gen(), batch_count
 
 
+def mixup(inputs, outputs, batch_size, p=0.1):
+    # paper: https://arxiv.org/abs/1710.09412
+
+    if p == 0:
+        return batchize(inputs, outputs, batch_size)
+
+    batch_count = np.ceil(len(inputs) / batch_size).astype(int)
+
+    def lerp(a, b, t):
+        t = t.reshape([len(t)] + [1] * (a.ndim - t.ndim))
+        return (1 - t) * a + t * b
+
+    def gen():
+        indices0 = np.arange(len(inputs))
+        indices1 = np.arange(len(inputs))
+        np.random.shuffle(indices0)
+        np.random.shuffle(indices1)
+
+        for b in range(batch_count):
+            bi = b * batch_size
+            ind0 = indices0[bi:bi + batch_size]
+            ind1 = indices1[bi:bi + batch_size]
+            ps = np.random.beta(p, p, size=batch_size)
+            batch_inputs = lerp(inputs[ind0], inputs[ind1], ps)
+            batch_outputs = lerp(outputs[ind0], outputs[ind1], ps)
+            yield batch_inputs, batch_outputs
+
+    return gen(), batch_count
+
+
 # more
 
 _log_was_update = False