Python misc._datacopied函数代码示例

def solve(a, b, sym_pos=False, lower=False, overwrite_a=False, overwrite_b=False,
          debug=False):
    """Solve the equation a x = b for x

    Parameters
    ----------
    a : array, shape (M, M)
    b : array, shape (M,) or (M, N)
    sym_pos : boolean
        Assume a is symmetric and positive definite
    lower : boolean
        Use only data contained in the lower triangle of a, if sym_pos is true.
        Default is to use upper triangle.
    overwrite_a : boolean
        Allow overwriting data in a (may enhance performance)
    overwrite_b : boolean
        Allow overwriting data in b (may enhance performance)

    Returns
    -------
    x : array, shape (M,) or (M, N) depending on b
        Solution to the system a x = b

    Raises LinAlgError if a is singular

    """
    a1, b1 = map(asarray_chkfinite,(a,b))
    if len(a1.shape) != 2 or a1.shape[0] != a1.shape[1]:
        raise ValueError('expected square matrix')
    if a1.shape[0] != b1.shape[0]:
        raise ValueError('incompatible dimensions')
    overwrite_a = overwrite_a or _datacopied(a1, a)
    overwrite_b = overwrite_b or _datacopied(b1, b)
    if debug:
        print 'solve:overwrite_a=',overwrite_a
        print 'solve:overwrite_b=',overwrite_b
    if sym_pos:
        posv, = get_lapack_funcs(('posv',), (a1,b1))
        c, x, info = posv(a1, b1, lower=lower,
                        overwrite_a=overwrite_a,
                        overwrite_b=overwrite_b)
    else:
        gesv, = get_lapack_funcs(('gesv',), (a1,b1))
        lu, piv, x, info = gesv(a1, b1, overwrite_a=overwrite_a,
                                            overwrite_b=overwrite_b)

    if info == 0:
        return x
    if info > 0:
        raise LinAlgError("singular matrix")
    raise ValueError('illegal value in %d-th argument of internal gesv|posv'
                                                                    % -info)

def det(a, overwrite_a=False):
    """Compute the determinant of a matrix

    Parameters
    ----------
    a : array, shape (M, M)

    Returns
    -------
    det : float or complex
        Determinant of a

    Notes
    -----
    The determinant is computed via LU factorization, LAPACK routine z/dgetrf.
    """
    a1 = asarray_chkfinite(a)
    if len(a1.shape) != 2 or a1.shape[0] != a1.shape[1]:
        raise ValueError('expected square matrix')
    overwrite_a = overwrite_a or _datacopied(a1, a)
    fdet, = get_flinalg_funcs(('det',), (a1,))
    a_det, info = fdet(a1, overwrite_a=overwrite_a)
    if info < 0:
        raise ValueError('illegal value in %d-th argument of internal '
                                                        'det.getrf' % -info)
    return a_det

def qr_old(a, overwrite_a=False, lwork=None, check_finite=True):
    """Compute QR decomposition of a matrix.

    Calculate the decomposition :lm:`A = Q R` where Q is unitary/orthogonal
    and R upper triangular.

    Parameters
    ----------
    a : array, shape (M, N)
        Matrix to be decomposed
    overwrite_a : boolean
        Whether data in a is overwritten (may improve performance)
    lwork : integer
        Work array size, lwork >= a.shape[1]. If None or -1, an optimal size
        is computed.
    check_finite : boolean, optional
        Whether to check the input matrixes contain only finite numbers.
        Disabling may give a performance gain, but may result to problems
        (crashes, non-termination) if the inputs do contain infinities or NaNs.

    Returns
    -------
    Q : float or complex array, shape (M, M)
    R : float or complex array, shape (M, N)
        Size K = min(M, N)

    Raises LinAlgError if decomposition fails

    """
    if check_finite:
        a1 = numpy.asarray_chkfinite(a)
    else:
        a1 = numpy.asarray(a)
    if len(a1.shape) != 2:
        raise ValueError('expected matrix')
    M,N = a1.shape
    overwrite_a = overwrite_a or (_datacopied(a1, a))
    geqrf, = get_lapack_funcs(('geqrf',), (a1,))
    if lwork is None or lwork == -1:
        # get optimal work array
        qr, tau, work, info = geqrf(a1, lwork=-1, overwrite_a=1)
        lwork = work[0]
    qr, tau, work, info = geqrf(a1, lwork=lwork, overwrite_a=overwrite_a)
    if info < 0:
        raise ValueError('illegal value in %d-th argument of internal geqrf'
                                                                    % -info)
    gemm, = get_blas_funcs(('gemm',), (qr,))
    t = qr.dtype.char
    R = numpy.triu(qr)
    Q = numpy.identity(M, dtype=t)
    ident = numpy.identity(M, dtype=t)
    zeros = numpy.zeros
    for i in range(min(M, N)):
        v = zeros((M,), t)
        v[i] = 1
        v[i+1:M] = qr[i+1:M, i]
        H = gemm(-tau[i], v, v, 1+0j, ident, trans_b=2)
        Q = gemm(1, Q, H)
    return Q, R

def solve_triangular(a, b, trans=0, lower=False, unit_diagonal=False,
                     overwrite_b=False, debug=False):
    """Solve the equation `a x = b` for `x`, assuming a is a triangular matrix.

    Parameters
    ----------
    a : array, shape (M, M)
    b : array, shape (M,) or (M, N)
    lower : boolean
        Use only data contained in the lower triangle of a.
        Default is to use upper triangle.
    trans : {0, 1, 2, 'N', 'T', 'C'}
        Type of system to solve:

        ========  =========
        trans     system
        ========  =========
        0 or 'N'  a x   = b
        1 or 'T'  a^T x = b
        2 or 'C'  a^H x = b
        ========  =========

    unit_diagonal : boolean
        If True, diagonal elements of A are assumed to be 1 and
        will not be referenced.

    overwrite_b : boolean
        Allow overwriting data in b (may enhance performance)

    Returns
    -------
    x : array, shape (M,) or (M, N) depending on b
        Solution to the system a x = b

    Raises
    ------
    LinAlgError
        If a is singular

    """

    a1, b1 = map(asarray_chkfinite,(a,b))
    if len(a1.shape) != 2 or a1.shape[0] != a1.shape[1]:
        raise ValueError('expected square matrix')
    if a1.shape[0] != b1.shape[0]:
        raise ValueError('incompatible dimensions')
    overwrite_b = overwrite_b or _datacopied(b1, b)
    if debug:
        print 'solve:overwrite_b=',overwrite_b
    trans = {'N': 0, 'T': 1, 'C': 2}.get(trans, trans)
    trtrs, = get_lapack_funcs(('trtrs',), (a1,b1))
    x, info = trtrs(a1, b1, overwrite_b=overwrite_b, lower=lower,
                    trans=trans, unitdiag=unit_diagonal)

    if info == 0:
        return x
    if info > 0:
        raise LinAlgError("singular matrix: resolution failed at diagonal %s" % (info-1))
    raise ValueError('illegal value in %d-th argument of internal trtrs')

def det(a, overwrite_a=False, check_finite=True):
    """
    Compute the determinant of a matrix

    The determinant of a square matrix is a value derived arithmetically
    from the coefficients of the matrix.

    The determinant for a 3x3 matrix, for example, is computed as follows::

        a    b    c
        d    e    f = A
        g    h    i

        det(A) = a*e*i +b*f*g + c*d*h - c*e*g - b*d*i - a*f*h

    Parameters
    ----------
    a : array_like, shape (M, M)
        A square matrix.
    overwrite_a : bool
        Allow overwriting data in a (may enhance performance).
    check_finite : boolean, optional
        Whether to check the input matrixes contain only finite numbers.
        Disabling may give a performance gain, but may result to problems
        (crashes, non-termination) if the inputs do contain infinities or NaNs.

    Returns
    -------
    det : float or complex
        Determinant of `a`.

    Notes
    -----
    The determinant is computed via LU factorization, LAPACK routine z/dgetrf.

    Examples
    --------
    >>> a = np.array([[1,2,3],[4,5,6],[7,8,9]])
    >>> linalg.det(a)
    0.0
    >>> a = np.array([[0,2,3],[4,5,6],[7,8,9]])
    >>> linalg.det(a)
    3.0

    """
    if check_finite:
        a1 = np.asarray_chkfinite(a)
    else:
        a1 = np.asarray(a)
    if len(a1.shape) != 2 or a1.shape[0] != a1.shape[1]:
        raise ValueError('expected square matrix')
    overwrite_a = overwrite_a or _datacopied(a1, a)
    fdet, = get_flinalg_funcs(('det',), (a1,))
    a_det, info = fdet(a1, overwrite_a=overwrite_a)
    if info < 0:
        raise ValueError('illegal value in %d-th argument of internal '
                                                        'det.getrf' % -info)
    return a_det

def lu_factor(a, overwrite_a=False, check_finite=True):
    """Compute pivoted LU decomposition of a matrix.

    The decomposition is::

        A = P L U

    where P is a permutation matrix, L lower triangular with unit
    diagonal elements, and U upper triangular.

    Parameters
    ----------
    a : array, shape (M, M)
        Matrix to decompose
    overwrite_a : boolean
        Whether to overwrite data in A (may increase performance)
    check_finite : boolean, optional
        Whether to check the input matrixes contain only finite numbers.
        Disabling may give a performance gain, but may result to problems
        (crashes, non-termination) if the inputs do contain infinities or NaNs.

    Returns
    -------
    lu : array, shape (N, N)
        Matrix containing U in its upper triangle, and L in its lower triangle.
        The unit diagonal elements of L are not stored.
    piv : array, shape (N,)
        Pivot indices representing the permutation matrix P:
        row i of matrix was interchanged with row piv[i].

    See also
    --------
    lu_solve : solve an equation system using the LU factorization of a matrix

    Notes
    -----
    This is a wrapper to the ``*GETRF`` routines from LAPACK.

    """
    if check_finite:
        a1 = asarray_chkfinite(a)
    else:
        a1 = asarray(a)
    if len(a1.shape) != 2 or (a1.shape[0] != a1.shape[1]):
        raise ValueError('expected square matrix')
    overwrite_a = overwrite_a or (_datacopied(a1, a))
    getrf, = get_lapack_funcs(('getrf',), (a1,))
    lu, piv, info = getrf(a1, overwrite_a=overwrite_a)
    if info < 0:
        raise ValueError('illegal value in %d-th argument of '
                                'internal getrf (lu_factor)' % -info)
    if info > 0:
        warn("Diagonal number %d is exactly zero. Singular matrix." % info,
                    RuntimeWarning)
    return lu, piv

def lu(a, permute_l=False, overwrite_a=False):
    """Compute pivoted LU decompostion of a matrix.

    The decomposition is::

        A = P L U

    where P is a permutation matrix, L lower triangular with unit
    diagonal elements, and U upper triangular.

    Parameters
    ----------
    a : array, shape (M, N)
        Array to decompose
    permute_l : boolean
        Perform the multiplication P*L  (Default: do not permute)
    overwrite_a : boolean
        Whether to overwrite data in a (may improve performance)

    Returns
    -------
    (If permute_l == False)
    p : array, shape (M, M)
        Permutation matrix
    l : array, shape (M, K)
        Lower triangular or trapezoidal matrix with unit diagonal.
        K = min(M, N)
    u : array, shape (K, N)
        Upper triangular or trapezoidal matrix

    (If permute_l == True)
    pl : array, shape (M, K)
        Permuted L matrix.
        K = min(M, N)
    u : array, shape (K, N)
        Upper triangular or trapezoidal matrix

    Notes
    -----
    This is a LU factorization routine written for Scipy.

    """
    a1 = asarray_chkfinite(a)
    if len(a1.shape) != 2:
        raise ValueError('expected matrix')
    overwrite_a = overwrite_a or (_datacopied(a1, a))
    flu, = get_flinalg_funcs(('lu',), (a1,))
    p, l, u, info = flu(a1, permute_l=permute_l, overwrite_a=overwrite_a)
    if info < 0:
        raise ValueError('illegal value in %d-th argument of '
                                            'internal lu.getrf' % -info)
    if permute_l:
        return l, u
    return p, l, u

def qr_old(a, overwrite_a=False, lwork=None):
    """Compute QR decomposition of a matrix.

    Calculate the decomposition :lm:`A = Q R` where Q is unitary/orthogonal
    and R upper triangular.

    Parameters
    ----------
    a : array, shape (M, N)
        Matrix to be decomposed
    overwrite_a : boolean
        Whether data in a is overwritten (may improve performance)
    lwork : integer
        Work array size, lwork >= a.shape[1]. If None or -1, an optimal size
        is computed.

    Returns
    -------
    Q : double or complex array, shape (M, M)
    R : double or complex array, shape (M, N)
        Size K = min(M, N)

    Raises LinAlgError if decomposition fails

    """
    a1 = asarray_chkfinite(a)
    if len(a1.shape) != 2:
        raise ValueError('expected matrix')
    M,N = a1.shape
    overwrite_a = overwrite_a or (_datacopied(a1, a))
    geqrf, = get_lapack_funcs(('geqrf',), (a1,))
    if lwork is None or lwork == -1:
        # get optimal work array
        qr, tau, work, info = geqrf(a1, lwork=-1, overwrite_a=1)
        lwork = work[0]
    qr, tau, work, info = geqrf(a1, lwork=lwork, overwrite_a=overwrite_a)
    if info < 0:
        raise ValueError('illegal value in %d-th argument of internal geqrf'
                                                                    % -info)
    gemm, = get_blas_funcs(('gemm',), (qr,))
    t = qr.dtype.char
    R = special_matrices.triu(qr)
    Q = numpy.identity(M, dtype=t)
    ident = numpy.identity(M, dtype=t)
    zeros = numpy.zeros
    for i in range(min(M, N)):
        v = zeros((M,), t)
        v[i] = 1
        v[i+1:M] = qr[i+1:M, i]
        H = gemm(-tau[i], v, v, 1, ident, trans_b=2)
        Q = gemm(1, Q, H)
    return Q, R

def _cholesky(a, lower=False, overwrite_a=False, clean=True):
    """Common code for cholesky() and cho_factor()."""

    a1 = asarray_chkfinite(a)
    if len(a1.shape) != 2 or a1.shape[0] != a1.shape[1]:
        raise ValueError('expected square matrix')

    overwrite_a = overwrite_a or _datacopied(a1, a)
    potrf, = get_lapack_funcs(('potrf',), (a1,))
    c, info = potrf(a1, lower=lower, overwrite_a=overwrite_a, clean=clean)
    if info > 0:
        raise LinAlgError("%d-th leading minor not positive definite" % info)
    if info < 0:
        raise ValueError('illegal value in %d-th argument of internal potrf'
                                                                    % -info)
    return c, lower

def lu_factor(a, overwrite_a=False):
    """Compute pivoted LU decomposition of a matrix.

    The decomposition is::

        A = P L U

    where P is a permutation matrix, L lower triangular with unit
    diagonal elements, and U upper triangular.

    Parameters
    ----------
    a : array, shape (M, M)
        Matrix to decompose
    overwrite_a : boolean
        Whether to overwrite data in A (may increase performance)

    Returns
    -------
    lu : array, shape (N, N)
        Matrix containing U in its upper triangle, and L in its lower triangle.
        The unit diagonal elements of L are not stored.
    piv : array, shape (N,)
        Pivot indices representing the permutation matrix P:
        row i of matrix was interchanged with row piv[i].

    See also
    --------
    lu_solve : solve an equation system using the LU factorization of a matrix

    Notes
    -----
    This is a wrapper to the ``*GETRF`` routines from LAPACK.

    """
    a1 = asarray(a)
    if len(a1.shape) != 2 or (a1.shape[0] != a1.shape[1]):
        raise ValueError("expected square matrix")
    overwrite_a = overwrite_a or (_datacopied(a1, a))
    getrf, = get_lapack_funcs(("getrf",), (a1,))
    lu, piv, info = getrf(a1, overwrite_a=overwrite_a)
    if info < 0:
        raise ValueError("illegal value in %d-th argument of " "internal getrf (lu_factor)" % -info)
    if info > 0:
        warn("Diagonal number %d is exactly zero. Singular matrix." % info, RuntimeWarning)
    return lu, piv

def _geneig(a1, b, left, right, overwrite_a, overwrite_b):
    b1 = asarray(b)
    overwrite_b = overwrite_b or _datacopied(b1, b)
    if len(b1.shape) != 2 or b1.shape[0] != b1.shape[1]:
        raise ValueError('expected square matrix')
    ggev, = get_lapack_funcs(('ggev',), (a1, b1))
    cvl, cvr = left, right
    ggev_info = get_func_info(ggev)
    if ggev_info.module_name[:7] == 'clapack':
        raise NotImplementedError('calling ggev from %s' % get_func_info(ggev).module_name)
    res = ggev(a1, b1, lwork=-1)
    lwork = res[-2][0]
    if ggev_info.prefix in 'cz':
        alpha, beta, vl, vr, work, info = ggev(a1, b1, cvl, cvr, lwork,
                                                    overwrite_a, overwrite_b)
        w = alpha / beta
    else:
        alphar, alphai, beta, vl, vr, work, info = ggev(a1, b1, cvl, cvr, lwork,
                                                        overwrite_a,overwrite_b)
        w = (alphar + _I * alphai) / beta
    if info < 0:
        raise ValueError('illegal value in %d-th argument of internal ggev'
                                                                    % -info)
    if info > 0:
        raise LinAlgError("generalized eig algorithm did not converge (info=%d)"
                                                                    % info)

    only_real = numpy.logical_and.reduce(numpy.equal(w.imag, 0.0))
    if not (ggev_info.prefix in 'cz' or only_real):
        t = w.dtype.char
        if left:
            vl = _make_complex_eigvecs(w, vl, t)
        if right:
            vr = _make_complex_eigvecs(w, vr, t)
    if not (left or right):
        return w
    if left:
        if right:
            return w, vl, vr
        return w, vl
    return w, vr

def eig(a, b=None, left=False, right=True, overwrite_a=False, overwrite_b=False):
    """
    Solve an ordinary or generalized eigenvalue problem of a square matrix.

    Find eigenvalues w and right or left eigenvectors of a general matrix::

        a   vr[:,i] = w[i]        b   vr[:,i]
        a.H vl[:,i] = w[i].conj() b.H vl[:,i]

    where ``.H`` is the Hermitian conjugation.

    Parameters
    ----------
    a : array_like, shape (M, M)
        A complex or real matrix whose eigenvalues and eigenvectors
        will be computed.
    b : array_like, shape (M, M), optional
        Right-hand side matrix in a generalized eigenvalue problem.
        Default is None, identity matrix is assumed.
    left : bool, optional
        Whether to calculate and return left eigenvectors.  Default is False.
    right : bool, optional
        Whether to calculate and return right eigenvectors.  Default is True.
    overwrite_a : bool, optional
        Whether to overwrite `a`; may improve performance.  Default is False.
    overwrite_b : bool, optional
        Whether to overwrite `b`; may improve performance.  Default is False.

    Returns
    -------
    w : double or complex ndarray
        The eigenvalues, each repeated according to its multiplicity.
        Of shape (M,).
    vl : double or complex ndarray
        The normalized left eigenvector corresponding to the eigenvalue
        ``w[i]`` is the column v[:,i]. Only returned if ``left=True``.
        Of shape ``(M, M)``.
    vr : double or complex array
        The normalized right eigenvector corresponding to the eigenvalue
        ``w[i]`` is the column ``vr[:,i]``.  Only returned if ``right=True``.
        Of shape ``(M, M)``.

    Raises
    ------
    LinAlgError
        If eigenvalue computation does not converge.

    See Also
    --------
    eigh : Eigenvalues and right eigenvectors for symmetric/Hermitian arrays.

    """
    a1 = asarray_chkfinite(a)
    if len(a1.shape) != 2 or a1.shape[0] != a1.shape[1]:
        raise ValueError('expected square matrix')
    overwrite_a = overwrite_a or (_datacopied(a1, a))
    if b is not None:
        b1 = asarray_chkfinite(b)
        overwrite_b = overwrite_b or _datacopied(b1, b)
        if len(b1.shape) != 2 or b1.shape[0] != b1.shape[1]:
            raise ValueError('expected square matrix')
        if b1.shape != a1.shape:
            raise ValueError('a and b must have the same shape')
        return _geneig(a1, b1, left, right, overwrite_a, overwrite_b)
    geev, = get_lapack_funcs(('geev',), (a1,))
    compute_vl, compute_vr = left, right
    if geev.module_name[:7] == 'flapack':
        lwork = calc_lwork.geev(geev.prefix, a1.shape[0],
                                    compute_vl, compute_vr)[1]
        if geev.prefix in 'cz':
            w, vl, vr, info = geev(a1, lwork=lwork,
                                        compute_vl=compute_vl,
                                        compute_vr=compute_vr,
                                        overwrite_a=overwrite_a)
        else:
            wr, wi, vl, vr, info = geev(a1, lwork=lwork,
                                        compute_vl=compute_vl,
                                        compute_vr=compute_vr,
                                        overwrite_a=overwrite_a)
            t = {'f':'F','d':'D'}[wr.dtype.char]
            w = wr + _I * wi
    else: # 'clapack'
        if geev.prefix in 'cz':
            w, vl, vr, info = geev(a1,
                                    compute_vl=compute_vl,
                                    compute_vr=compute_vr,
                                    overwrite_a=overwrite_a)
        else:
            wr, wi, vl, vr, info = geev(a1,
                                        compute_vl=compute_vl,
                                        compute_vr=compute_vr,
                                        overwrite_a=overwrite_a)
            t = {'f':'F','d':'D'}[wr.dtype.char]
            w = wr + _I * wi
    if info < 0:
        raise ValueError('illegal value in %d-th argument of internal geev'
                                                                    % -info)
    if info > 0:
        raise LinAlgError("eig algorithm did not converge (only eigenvalues "
                            "with order >= %d have converged)" % info)
#.........这里部分代码省略.........

        The solution to the system a x = b

    """

    if check_finite:
        a1, b1 = map(np.asarray_chkfinite, (ab, b))
    else:
        a1, b1 = map(np.asarray, (ab,b))
    # Validate shapes.
    if a1.shape[-1] != b1.shape[0]:
        raise ValueError("shapes of ab and b are not compatible.")
    if l + u + 1 != a1.shape[0]:
        raise ValueError("invalid values for the number of lower and upper diagonals:"
                " l+u+1 (%d) does not equal ab.shape[0] (%d)" % (l+u+1, ab.shape[0]))

    overwrite_b = overwrite_b or _datacopied(b1, b)

    gbsv, = get_lapack_funcs(('gbsv',), (a1, b1))
    a2 = np.zeros((2*l+u+1, a1.shape[1]), dtype=gbsv.dtype)
    a2[l:,:] = a1
    lu, piv, x, info = gbsv(l, u, a2, b1, overwrite_ab=True,
                                                overwrite_b=overwrite_b)
    if info == 0:
        return x
    if info > 0:
        raise LinAlgError("singular matrix")
    raise ValueError('illegal value in %d-th argument of internal gbsv' % -info)

def solveh_banded(ab, b, overwrite_ab=False, overwrite_b=False, lower=False,
                    check_finite=True):
    """Solve equation a x = b. a is Hermitian positive-definite banded matrix.

def eig_banded(a_band, lower=False, eigvals_only=False, overwrite_a_band=False,
               select='a', select_range=None, max_ev = 0):
    """Solve real symmetric or complex hermitian band matrix eigenvalue problem.

    Find eigenvalues w and optionally right eigenvectors v of a::

        a v[:,i] = w[i] v[:,i]
        v.H v    = identity

    The matrix a is stored in a_band either in lower diagonal or upper
    diagonal ordered form:

        a_band[u + i - j, j] == a[i,j]        (if upper form; i <= j)
        a_band[    i - j, j] == a[i,j]        (if lower form; i >= j)

    where u is the number of bands above the diagonal.

    Example of a_band (shape of a is (6,6), u=2)::

        upper form:
        *   *   a02 a13 a24 a35
        *   a01 a12 a23 a34 a45
        a00 a11 a22 a33 a44 a55

        lower form:
        a00 a11 a22 a33 a44 a55
        a10 a21 a32 a43 a54 *
        a20 a31 a42 a53 *   *

    Cells marked with * are not used.

    Parameters
    ----------
    a_band : array, shape (u+1, M)
        The bands of the M by M matrix a.
    lower : boolean
        Is the matrix in the lower form. (Default is upper form)
    eigvals_only : boolean
        Compute only the eigenvalues and no eigenvectors.
        (Default: calculate also eigenvectors)
    overwrite_a_band:
        Discard data in a_band (may enhance performance)
    select: {'a', 'v', 'i'}
        Which eigenvalues to calculate

        ======  ========================================
        select  calculated
        ======  ========================================
        'a'     All eigenvalues
        'v'     Eigenvalues in the interval (min, max]
        'i'     Eigenvalues with indices min <= i <= max
        ======  ========================================
    select_range : (min, max)
        Range of selected eigenvalues
    max_ev : integer
        For select=='v', maximum number of eigenvalues expected.
        For other values of select, has no meaning.

        In doubt, leave this parameter untouched.

    Returns
    -------
    w : array, shape (M,)
        The eigenvalues, in ascending order, each repeated according to its
        multiplicity.

    v : double or complex double array, shape (M, M)
        The normalized eigenvector corresponding to the eigenvalue w[i] is
        the column v[:,i].

    Raises LinAlgError if eigenvalue computation does not converge

    """
    if eigvals_only or overwrite_a_band:
        a1 = asarray_chkfinite(a_band)
        overwrite_a_band = overwrite_a_band or (_datacopied(a1, a_band))
    else:
        a1 = array(a_band)
        if issubclass(a1.dtype.type, inexact) and not isfinite(a1).all():
            raise ValueError("array must not contain infs or NaNs")
        overwrite_a_band = 1

    if len(a1.shape) != 2:
        raise ValueError('expected two-dimensional array')
    if select.lower() not in [0, 1, 2, 'a', 'v', 'i', 'all', 'value', 'index']:
        raise ValueError('invalid argument for select')
    if select.lower() in [0, 'a', 'all']:
        if a1.dtype.char in 'GFD':
            bevd, = get_lapack_funcs(('hbevd',), (a1,))
            # FIXME: implement this somewhen, for now go with builtin values
            # FIXME: calc optimal lwork by calling ?hbevd(lwork=-1)
            #        or by using calc_lwork.f ???
            # lwork = calc_lwork.hbevd(bevd.prefix, a1.shape[0], lower)
            internal_name = 'hbevd'
        else: # a1.dtype.char in 'fd':
            bevd, = get_lapack_funcs(('sbevd',), (a1,))
            # FIXME: implement this somewhen, for now go with builtin values
            #         see above
            # lwork = calc_lwork.sbevd(bevd.prefix, a1.shape[0], lower)
            internal_name = 'sbevd'
#.........这里部分代码省略.........

def hessenberg(a, calc_q=False, overwrite_a=False):
    """
    Compute Hessenberg form of a matrix.

    The Hessenberg decomposition is::

        A = Q H Q^H

    where `Q` is unitary/orthogonal and `H` has only zero elements below
    the first sub-diagonal.

    Parameters
    ----------
    a : ndarray
        Matrix to bring into Hessenberg form, of shape ``(M,M)``.
    calc_q : bool, optional
        Whether to compute the transformation matrix.  Default is False.
    overwrite_a : bool, optional
        Whether to overwrite `a`; may improve performance.
        Default is False.

    Returns
    -------
    H : ndarray
        Hessenberg form of `a`, of shape (M,M).
    Q : ndarray
        Unitary/orthogonal similarity transformation matrix ``A = Q H Q^H``.
        Only returned if ``calc_q=True``.  Of shape (M,M).

    """
    a1 = asarray(a)
    if len(a1.shape) != 2 or (a1.shape[0] != a1.shape[1]):
        raise ValueError('expected square matrix')
    overwrite_a = overwrite_a or (_datacopied(a1, a))
    gehrd,gebal = get_lapack_funcs(('gehrd','gebal'), (a1,))
    ba, lo, hi, pivscale, info = gebal(a1, permute=1, overwrite_a=overwrite_a)
    if info < 0:
        raise ValueError('illegal value in %d-th argument of internal gebal '
                                                    '(hessenberg)' % -info)
    n = len(a1)
    lwork = calc_lwork.gehrd(gehrd.prefix, n, lo, hi)
    hq, tau, info = gehrd(ba, lo=lo, hi=hi, lwork=lwork, overwrite_a=1)
    if info < 0:
        raise ValueError('illegal value in %d-th argument of internal gehrd '
                                        '(hessenberg)' % -info)

    if not calc_q:
        for i in range(lo, hi):
            hq[i+2:hi+1, i] = 0.0
        return hq

    # XXX: Use ORGHR routines to compute q.
    typecode = hq.dtype
    ger,gemm = get_blas_funcs(('ger','gemm'), dtype=typecode)
    q = None
    for i in range(lo, hi):
        if tau[i]==0.0:
            continue
        v = zeros(n, dtype=typecode)
        v[i+1] = 1.0
        v[i+2:hi+1] = hq[i+2:hi+1, i]
        hq[i+2:hi+1, i] = 0.0
        h = ger(-tau[i], v, v,a=diag(ones(n, dtype=typecode)), overwrite_a=1)
        if q is None:
            q = h
        else:
            q = gemm(1.0, q, h)
    if q is None:
        q = diag(ones(n, dtype=typecode))
    return hq, q