human
Complete the below
@non_reentrant()
def qmr(A, b, x0=None, tol=1e-05, maxiter=None, xtype=None, M1=None, M2=None, callback=None):

    ''''Use Quasi-Minimal Residual iteration to solve ``Ax = b``.
    Parameters
    A : {sparse matrix, dense matrix, LinearOperator}
    The real-valued N-by-N matrix of the linear system.
    It is required that the linear operator can produce
    ``Ax`` and ``A^T x``.
    b : {array, matrix}
    Right hand side of the linear system. Has shape (N,) or (N,1).
    Returns
    x : {array, matrix}
    The converged solution.
    info : integer
    Provides convergence information:
    0  : successful exit
    >0 : convergence to tolerance not achieved, number of iterations
    <0 : illegal input or breakdown
    Other Parameters
    x0  : {array, matrix}
    Starting guess for the solution.
    tol : float
    Tolerance to achieve. The algorithm terminates when either the relative
    or the absolute residual is below `tol`.
    maxiter : integer
    Maximum number of iterations.  Iteration will stop after maxiter
    steps even if the specified tolerance has not been achieved.
    M1 : {sparse matrix, dense matrix, LinearOperator}
    Left preconditioner for A.
    M2 : {sparse matrix, dense matrix, LinearOperator}
    Right preconditioner for A. Used together with the left
    preconditioner M1.  The matrix M1*A*M2 should have better
    conditioned than A alone.
    callback : function
    User-supplied function to call after each iteration.  It is called
    as callback(xk), where xk is the current solution vector.
    xtype : {\'f\',\'d\',\'F\',\'D\'}
    This parameter is DEPRECATED -- avoid using it.
    The type of the result.  If None, then it will be determined from
    A.dtype.char and b.  If A does not have a typecode method then it
    will compute A.matvec(x0) to get a typecode.   To save the extra
    computation when A does not have a typecode attribute use xtype=0
    for the same type as b or use xtype=\'f\',\'d\',\'F\',or \'D\'.
    This parameter has been superseded by LinearOperator.
    See Also
    LinearOperator
    Examples
    >>> from scipy.sparse import csc_matrix
    >>> from...'''

What is a Python program to compute A?
assistant
#Here is Python program to compute A.
    A_ = A
    (A, M, x, b, postprocess) = make_system(A, None, x0, b, xtype)
    if ((M1 is None) and (M2 is None)):
        if hasattr(A_, 'psolve'):
            def left_psolve(b):
                return A_.psolve(b, 'left')
            def right_psolve(b):
                return A_.psolve(b, 'right')
            def left_rpsolve(b):
                return A_.rpsolve(b, 'left')
            def right_rpsolve(b):
                return A_.rpsolve(b, 'right')
            M1 = LinearOperator(A.shape, matvec=left_psolve, rmatvec=left_rpsolve)
            M2 = LinearOperator(A.shape, matvec=right_psolve, rmatvec=right_rpsolve)
        else:
            def id(b):
                return b
            M1 = LinearOperator(A.shape, matvec=id, rmatvec=id)
            M2 = LinearOperator(A.shape, matvec=id, rmatvec=id)
    n = len(b)
    if (maxiter is None):
        maxiter = (n * 10)
    ltr = _type_conv[x.dtype.char]
    revcom = getattr(_iterative, (ltr + 'qmrrevcom'))
    stoptest = getattr(_iterative, (ltr + 'stoptest2'))
    resid = tol
    ndx1 = 1
    ndx2 = (-1)
    work = _aligned_zeros((11 * n), x.dtype)
    ijob = 1
    info = 0
    ftflag = True
    bnrm2 = (-1.0)
    iter_ = maxiter
    while True:
        olditer = iter_
        (x, iter_, resid, info, ndx1, ndx2, sclr1, sclr2, ijob) = revcom(b, x, work, iter_, resid, info, ndx1, ndx2, ijob)
        if ((callback is not None) and (iter_ > olditer)):
            callback(x)
        slice1 = slice((ndx1 - 1), ((ndx1 - 1) + n))
        slice2 = slice((ndx2 - 1), ((ndx2 - 1) + n))
        if (ijob == (-1)):
            if (callback is not None):
                callback(x)
            break
        elif (ijob == 1):
            work[slice2] *= sclr2
            work[slice2] += (sclr1 * A.matvec(work[slice1]))
        elif (ijob == 2):
            work[slice2] *= sclr2
            work[slice2] += (sclr1 * A.rmatvec(work[slice1]))
        elif (ijob == 3):
            work[slice1] = M1.matvec(work[slice2])
        elif (ijob == 4):
            work[slice1] =...