>> [A b]= load_equ('cooA.txt', 'b.txt');
>> spy(A)
>> x= pcg(A, b, 1e-2, 500);
pcg converged at iteration 383 to a solution with relative residual 0.0098.
>> x= pcg(A, b, 1e-2, 500, diag(diag(A)));
pcg converged at iteration 179 to a solution with relative residual 0.0096.
>> help mySOR
  SOR iteration for solving Ax=b;
  [x, iter]= mySOR(A, b, omega, tol, maxit, flag);
  tol is the criteria of relative residual ||b-Ax||/||b||
  The last three parameters are optional. Default values are
  tol=1e-3, maxit=1000, flag=0 (if flag=1, prints iterative solutions)

>> [x, iter]= mySOR(A, b, 1, 1e-2, 5000);
Converged with  3813  steps!
>> [x, iter]= mySOR(A, b, 1.3, 1e-2, 5000);
Converged with  2403  steps!
>> [x, iter]= mySOR(A, b, 1.2, 1e-2, 5000);
Converged with  2803  steps!
>> opt.type= 'ict';
>> opt.droptol=0.3;
>> L=ichol(A, opt);
>> spy(L); figure(2); spy(A);
>> x=pcg(A, b, 1e-2, 500, L, L');
pcg converged at iteration 99 to a solution with relative residual 0.0095.
>> 