diff --git a/paddle/framework/ddim.h b/paddle/framework/ddim.h
index 48e14d16e3ef4c04ec5c6a1a4f3fcd997b9672c0..ca29e7e8c7776de6adf3e3b0e8f11f0d4d8487c3 100644
--- a/paddle/framework/ddim.h
+++ b/paddle/framework/ddim.h
@@ -116,7 +116,7 @@ int arity(const DDim& ddim);
 std::ostream& operator<<(std::ostream&, const DDim&);
 
 // Reshape a tensor to a matrix. The matrix's first dimension(column length)
-// will be the product of tensor's first `num_col_dims` dimensions
+// will be the product of tensor's first `num_col_dims` dimensions.
 DDim flatten_to_2d(const DDim& src, int num_col_dims);
 
 DDim flatten_to_1d(const DDim& src);