def lgmres_params(inner_m=30, outer_k=3, maxiter=100, tol_coef=0.01):
    """
    Bundles parameters for the LGMRES linear solver. These control the
    expense of finding the left and right environment Hamiltonians.

    PARAMETERS
    ----------
    inner_m (int, 30): Number of gmres iterations per outer k loop.
    outer_k (int, 3) : Number of vectors to carry between inner iterations.
    maxiter (int)    : lgmres terminates after this many iterations.
    tol_coef (float): This number times the MPS gradient will set the
                      convergence threshold of the linear solve.

    RETURNS
    -------
    A dictionary storing each of these parameters.
    """
    return {"solver": "lgmres", "inner_m": inner_m, "maxiter": maxiter,
            "outer_k": outer_k, "tol_coef": tol_coef}