def __init__(self, M, ifunc=gmres, tol=0):
        if tol <= 0:
            # when tol=0, ARPACK uses machine tolerance as calculated
            # by LAPACK's _LAMCH function.  We should match this
            tol = 2 * np.finfo(M.dtype).eps
        self.M = M
        self.ifunc = ifunc
        self.tol = tol
        if hasattr(M, 'dtype'):
            self.dtype = M.dtype
        else:
            x = np.zeros(M.shape[1])
            self.dtype = (M * x).dtype
        self.shape = M.shape
dataset/ETHPy150Open scikit-learn/scikit-learn/sklearn/utils/arpack.py/IterInv.__init__/original