Well I want to solve a 2D homogeneous Laplace equation (Dirichlet BC.) in a domain with 256*256 grid point with CG algorithm. common CG Algorithm I'm using MATLAB and it's so obvious that my coefficient matrix (A) is 256^2*256^2 that is out of memory and I can't even form it like a matrix. What should I do? What is the numerical technique when we want to do a CG-like method to a large general matrix?
*Note: A is 5 banded symmetric matrix
thanks