▍1. single
使用奇异值分解来帮助求解最小二乘问题,特别是在方程系数矩阵不满秩的情况下。(SGELSD computes the minimum-norm solution to a real linear least * squares problem: * minimize 2-norm(| b- A*x |) * using the singular value decomposition (SVD) of A. A is an M-by-N * matrix which may be rank-deficient.)