matrix of size n-by-n or function returning A*x

right hand side vector

initial guess vector (default: zeros(n,1))

left preconditioner: matrix or function returning M1*x (In the first case, default: eye(n,n))

must only be provided when M1 is a function. In this case M1p is the function which returns M1'*x

right preconditioner: matrix or function returning M2*x (In the first case, default: eye(n,n))

must only be provided when M2 is a function. In this case M2p is the function which returns M2'*x

maximum number of iterations (default: n)

error tolerance (default: 1000*%eps)

solution vector

residual vector

final residual norm

number of iterations performed