diff --git a/wit/meaning_dataset.py b/wit/meaning_dataset.py
index c79f408..65a85db 100644
--- a/wit/meaning_dataset.py
+++ b/wit/meaning_dataset.py
@@ -85,6 +85,9 @@ class MeaningMap:
                 ms_start[i] = index
                 ms_end[i] = index + 1
                 ms_len[i] = 1
+                ms_level[i] = 0
+                ms_rank_idx[i] = 0xFFFFFFF
+                ms_rank_all[i] = 0xFFFFFFF
                 ms_height[i] = 0
                 ms_weight[i] = 1
                 index = index + 1
@@ -95,8 +98,13 @@ class MeaningMap:
                 m_len = len(m)
                 m_list = m.tolist()
                 assert m_list, "map list can not be empty list"
-                ma = np.concatenate([ms_data[ms_start[newm] : ms_end[newm]] for newm in m_list])
-                len_ma = len(ma)
+
+                idx = np.concatenate([np.arange(ms_start[m], ms_end[m]) for m in m_list])
+                idxidx = np.concatenate(
+                    [np.ones(l, dtype=np.uint32) * i for i, l in enumerate(ms_end[m_list] - ms_start[m_list])]
+                )
+                len_ma = len(idx)
+
                 end = index + len_ma
                 if ms_data.size < end:
                     ms_data = np.concatenate([ms_data, np.zeros((268435456), dtype=np.int32)])
@@ -104,33 +112,16 @@ class MeaningMap:
                     ms_rank_idx = np.concatenate([ms_rank_idx, np.zeros((268435456), dtype=np.uint32)])
                     ms_rank_all = np.concatenate([ms_rank_all, np.zeros((268435456), dtype=np.uint32)])
 
-                ms_data[index:end] = ma
-                ms_level[index:end] = np.concatenate([ms_level[ms_start[newm] : ms_end[newm]] + 1 for newm in m_list])
-                ms_rank_idx[index:end] = np.concatenate(
-                    [
-                        (
-                            [0xFFFFFFF0 + i]
-                            if newm < self.vocab_size
-                            else ms_rank_idx[ms_start[newm] : ms_end[newm]] * 16 + i
-                        )
-                        for i, newm in enumerate(m_list)
-                    ]
-                ).astype(np.uint32)
-                ms_rank_all[index:end] = np.concatenate(
-                    [
-                        (
-                            [0xFFFFFFF0 + m_len]
-                            if newm < self.vocab_size
-                            else ms_rank_all[ms_start[newm] : ms_end[newm]] * 16 + m_len
-                        )
-                        for i, newm in enumerate(m_list)
-                    ]
-                ).astype(np.uint32)
+                ms_data[index:end] = ms_data[idx]
+                ms_level[index:end] = ms_level[idx] + 1
+                ms_rank_idx[index:end] = (ms_rank_idx[idx] * 16 + idxidx).astype(np.uint32)
+                ms_rank_all[index:end] = (ms_rank_all[idx] * 16 + m_len).astype(np.uint32)
+
                 ms_start[i] = index
                 ms_end[i] = end
                 ms_len[i] = len_ma
-                ms_height[i] = max([ms_height[sub_m] for sub_m in m_list]) + 1
-                ms_weight[i] = sum(ms_weight[sub_m] for sub_m in m_list)
+                ms_height[i] = max(ms_height[m_list]) + 1
+                ms_weight[i] = sum(ms_weight[m_list])
                 index = index + len_ma
                 if i % 10000 == 0:
                     print(i)
@@ -139,6 +130,7 @@ class MeaningMap:
 
             d = np.ones(ms_rank_idx.shape, dtype=np.uint32)
             d = ((d * 0xFFFFFFFF) << (ms_level * 4)).astype(np.uint32)
+            shift = (8 - ms_level) * 4
             ms_rank_idx = (
                 ((ms_rank_idx & 0xF) << 28)
                 + ((ms_rank_idx & 0xF0) << 20)
@@ -149,7 +141,7 @@ class MeaningMap:
                 + ((ms_rank_idx & 0xF000000) >> 20)
                 + ((ms_rank_idx & 0xF0000000) >> 28)
             )
-            ms_rank_idx = ((ms_rank_idx >> ((8 - ms_level) * 4)) + d).astype(np.uint32)
+            ms_rank_idx = ((ms_rank_idx >> shift) + d).astype(np.uint32)
             ms_rank_all = (
                 ((ms_rank_all & 0xF) << 28)
                 + ((ms_rank_all & 0xF0) << 20)
@@ -160,7 +152,7 @@ class MeaningMap:
                 + ((ms_rank_all & 0xF000000) >> 20)
                 + ((ms_rank_all & 0xF0000000) >> 28)
             )
-            ms_rank_all = ((ms_rank_all >> ((8 - ms_level) * 4)) + d).astype(np.uint32)
+            ms_rank_all = ((ms_rank_all >> shift) + d).astype(np.uint32)
 
             ms_start = np.array(ms_start).astype(np.int32)
             ms_height = np.array(ms_height).astype(np.int32)