列主元高斯消去：解方程组用，在实际使用高斯消去法时，常结合使用“选主元”的技术以避免零主元或小主元的出现，以便保证高斯消去发的正常进行或改善求解过程的数值稳定性。-PCA out Gaussian elimination: Solution of equations used in the actual use of Gaussian elimination method, often combined with the use of　PCA election　technology in order to avoid zero or small PCA PCA emergence in order to guarantee issued by Gaussian elimination normal or improve the numerical stability of the solution process.