scriptLab4

lab4gs.m

function [convf,k,results,xn] = mygaussseidel(A,b,x,niter,tol)

[nrow,~] = size(A);
convf = 0;
results(1,:) = x';
xn = x;

for k = 1:niter
  
   for i = 1:nrow
       sigma = 0;
       for j = 1:nrow
           if (i~=j)
              sigma = sigma + A(i,j)*xn(j);
           end
       end
       xn(i) = (b(i)-sigma)/A(i,i);
   
   end   
   
    if (norm(x-xn,Inf) / norm(xn,Inf)) < tol
        convf = 1;
        results(k+1,:) = xn';
        break 
    end
    
    x = xn;
    results(k+1,:) = xn'; 
end

end

lab4jacobi.m

function [convf,k,results,xn] = myjacobi(A,b,x,niter,tol)

[nrow,~] = size(A);
convf = 0;
results(1,:) = x';
xn = zeros(nrow,1);

for k = 1:niter
  
   for i = 1:nrow
       sigma = 0;
       for j = 1:nrow
           if (i~=j)
              sigma = sigma + A(i,j)*x(j);
           end
       end
       xn(i) = (b(i)-sigma)/A(i,i);
   
   end   
   
    if (norm(x-xn,Inf) / norm(xn,Inf)) < tol
        convf = 1;
        results(k+1,:) = xn';
        break 
    end
    
    x = xn;
    results(k+1,:) = xn'; 
end

end

scriptLab4.m

clear all
clc

A = [ 4 1 1 ; 1 2 3 ; 2 -1 -3];
%A = [ 4 -2 1 ; 3 -6 1 ; -4 1 6];
%A = [ 1 -2 1 ; 3 1 1 ; -4 1 1];
b = [5 ; 5 ; -3];
x = [0 ; 0 ; 0];
niter = 100;
tol = 1e-6;

[convf,i,resultsj,xn] = myjacobi(A,b,x,niter,tol);

i
convf
resultsj(end,:)'
A\b
b
A*resultsj(end,:)'


[convf,i,resultsgs,xn] = mygaussseidel(A,b,x,niter,tol);

i
convf
resultsgs(end,:)'
A\b
b
A*resultsgs(end,:)'