在波动方程的经典解法中，初始条件与边界条件都要充分光滑，介质系数也不能出现间断。

In the classic solution of wave equation, it is required that the initial and boundary conditions should be smooth enough and any discontinuities are not allowed in medium coefficients.

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当在空间位置出现突变时，偏微分方程的经典解法如有限元法和加权残差法等无法保证解的精度和收敛性。

The problems of resolution and convergence are increased by classic methods such as FEM and WRM when the solutions exhibit sharp changes.

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对于背包问题这样一个经典的递归问题，发现了它的不需栈支持的循环解法，并由此说明其存在并行。

For knapsack problem (which is a classical recursion problem), find its round solution which need not stack to support, then prove it exists parallel solutio.

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