Using the framework of operator or Calder\'on preconditioning, uniform preconditioners are constructed for elliptic operators discretized with continuous finite (or boundary) elements. The preconditioners are constructed as the composition of an opposite order operator, discretized on the same ansatz space, and two diagonal scaling operators.

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操作员预处理：最简单的情况

使用算子或Calder'on预处理的框架，为离散化具有连续有限（或边界）元素的椭圆算子构造统一的预处理器。预处理器由反序算子和两个对角线缩放算子组成，该算子在相同的ansatz空间上离散。