一些小修改，应该不影响结果

src/fold.cpp

@@ -11,15 +11,17 @@ void ufo::fold(std::string config_file)
 
   auto fold = []
   (
-    Eigen::Vector3d qpoint_in_reciprocal_primitive_cell_by_reciprocal_primitive_cell,
-    Eigen::Matrix3d super_cell_transformation
+    Eigen::Matrix3d super_cell_deformation,
+    Eigen::Vector3i super_cell_multiplier,
+    Eigen::Vector3d qpoint_in_reciprocal_primitive_cell_by_reciprocal_primitive_cell
   ) -> Eigen::Vector3d
   {
     /*
       首先需要将 q 点坐标的单位转换为 ModifiedSuperCell 的格矢，可知：
-      QpointByReciprocalModifiedSuperCell = SuperCellMultiplier * QpointByReciprocalPrimitiveCell;
+      QpointByReciprocalModifiedSuperCell =
+        SuperCellMultiplier.cast<double>().asDiagonal() * QpointByReciprocalPrimitiveCell;
       接下来考虑将 q 点坐标的单位转换为 SuperCell 的格矢
-      ModifiedSuperCell = SuperCellMultiplier * PrimativeCell;
+      ModifiedSuperCell = SuperCellMultiplier.transpose() * PrimativeCell;
       SuperCell = SuperCellDeformation * ModifiedSuperCell;
       ReciprocalModifiedSuperCell = ModifiedSuperCell.inverse().transpose();
       ReciprocalSuperCell = SuperCell.inverse().transpose();
@@ -28,17 +30,20 @@ void ufo::fold(std::string config_file)
       整理可以得到:
       QpointByReciprocalSuperCell = SuperCellDeformation * QpointByReciprocalModifiedSuperCell;
       两个式子结合，可以得到：
-      QpointByReciprocalSuperCell = SuperCellDeformation * SuperCellMultiplier * QpointByReciprocalPrimitiveCell;
+      QpointByReciprocalSuperCell =
+        SuperCellDeformation * SuperCellMultiplier.cast<double>().asDiagonal() * QpointByReciprocalPrimitiveCell;
     */
-    auto qpoint_by_reciprocal_super_cell =
+    auto qpoint_in_reciprocal_primitive_cell_by_reciprocal_super_cell =
     (
-      super_cell_transformation * qpoint_in_reciprocal_primitive_cell_by_reciprocal_primitive_cell
+      super_cell_deformation * super_cell_multiplier.cast<double>().asDiagonal()
+        * qpoint_in_reciprocal_primitive_cell_by_reciprocal_primitive_cell
     ).eval();
     /*
       到目前为止，我们还没有移动过 q 点的坐标。现在，我们将它移动整数个 ReciprocalSuperCell，直到它落在超胞的倒格子中。
       这等价于直接取 QpointByReciprocalSuperCell - QpointByReciprocalSuperCell.floor()。
     */
-    return (qpoint_by_reciprocal_super_cell.array() - qpoint_by_reciprocal_super_cell.array().floor()).matrix();
+    return (qpoint_in_reciprocal_primitive_cell_by_reciprocal_super_cell.array()
+      - qpoint_in_reciprocal_primitive_cell_by_reciprocal_super_cell.array().floor()).matrix();
   };
 
   biu::Logger::Guard log(config_file);
@@ -46,7 +51,6 @@ void ufo::fold(std::string config_file)
   for (const auto& qpoint : input.Qpoints) log.info("{} -> {}"_f
     (
       qpoint,
-      fold(qpoint,
-        input.SuperCellDeformation * input.SuperCellMultiplier.cast<double>().asDiagonal())
+      fold(input.SuperCellDeformation, input.SuperCellMultiplier, qpoint)
     ));
 }