update the split logic for uniform (#47670)

python/paddle/distributed/fleet/meta_parallel/parallel_layers/pp_layers.py

@@ -171,8 +171,10 @@ class SegmentLayers(object):
     def uniform(self, num_items, num_parts):
         result = [0 for _ in range(num_parts + 1)]
         part_size = math.floor(num_items / num_parts)
-        for i in range(num_parts):
-            result[i] = int(min(part_size * i, num_items))
+        extra_layers = num_items % num_parts
+        for i in range(1, num_parts):
+            offset = 1 if i > (num_parts - extra_layers) else 0
+            result[i] = int(min(result[i - 1] + part_size + offset, num_items))
         result[num_parts] = num_items
         return result