Matlab code for Gauss-Seidel and Successive over relaxation iterative methods
2017-06-14 19:00
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代码matlab 维基原理
原始代码里面每迭代一次都求解线性方程组,不太合理。可以通过改写,只须求一次即可。
不过考虑到矩阵是上三角的,主要只涉及回代,也就未必不行。
matrixSplit.m
sor.m
原始代码里面每迭代一次都求解线性方程组,不太合理。可以通过改写,只须求一次即可。
不过考虑到矩阵是上三角的,主要只涉及回代,也就未必不行。
function [x, error, iter, flag] = sor(A, x, b, w, max_it, tol) % -- Iterative template routine -- % Univ. of Tennessee and Oak Ridge National Laboratory % October 1, 1993 % Details of this algorithm are described in "Templates for the % Solution of Linear Systems: Building Blocks for Iterative % Methods", Barrett, Berry, Chan, Demmel, Donato, Dongarra, % Eijkhout, Pozo, Romine, and van der Vorst, SIAM Publications, % 1993. (ftp netlib2.cs.utk.edu; cd linalg; get templates.ps). % % [x, error, iter, flag] = sor(A, x, b, w, max_it, tol) % % sor.m solves the linear system Ax=b using the % Successive Over-Relaxation Method (Gauss-Seidel method when omega = 1 ). % % input A REAL matrix % x REAL initial guess vector % b REAL right hand side vector % w REAL relaxation scalar % max_it INTEGER maximum number of iterations % tol REAL error tolerance % % output x REAL solution vector % error REAL error norm % iter INTEGER number of iterations performed % flag INTEGER: 0 = solution found to tolerance % 1 = no convergence given max_it flag = 0; % initialization iter = 0; bnrm2 = norm( b ); if ( bnrm2 == 0.0 ), bnrm2 = 1.0; end r = b - A*x; error = norm( r ) / bnrm2; if ( error < tol ) return, end [ M, N, b ] = MatriceSplit( A, b, w, 2 ); % matrix splitting M01=M\N;%改写 M02=M\b; for iter = 1:max_it % begin iteration x_1 = x; x = M01*x+M02; %M \ ( N*x + b ); % update approximation error = norm( x - x_1 ) / norm( x ); % compute error if ( error <= tol ), break, end % check convergence end b = b / w; % restore rhs if ( error > tol ) flag = 1; end; % no convergence function [ M, N, b ] = MatriceSplit( A, b, w, flag ) % % function [ M, N, b ] = MatriceSplit( A, b, w, flag ) % % MatriceSplit.m sets up the matrix splitting for the stationary % iterative methods: jacobi and sor (gauss-seidel when w = 1.0 ) % % input A DOUBLE PRECISION matrix % b DOUBLE PRECISION right hand side vector (for SOR) % w DOUBLE PRECISION relaxation scalar % flag INTEGER flag for method: 1 = jacobi % 2 = sor % % output M DOUBLE PRECISION matrix % N DOUBLE PRECISION matrix such that A = M - N % b DOUBLE PRECISION rhs vector ( altered for SOR ) [m,n] = size( A ); if ( flag == 1 ), % jacobi splitting M = diag(diag(A)); N = diag(diag(A)) - A; elseif ( flag == 2 ), % sor/gauss-seidel splitting b = w * b; M = w * tril( A, -1 ) + diag(diag( A )); N = -w * triu( A, 1 ) + ( 1.0 - w ) * diag(diag( A )); end; % END MatriceSplit.m % END sor.m
matrixSplit.m
sor.m
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