Python numpy.nditer() Examples

def to_value(self, parent=None):
        scale = self.scale.upper().encode('ascii'),
        iys, ims, ids, ihmsfs = erfa.d2dtf(scale, self.precision,
                                           self.jd1, self.jd2)
        ihrs = ihmsfs['h']
        imins = ihmsfs['m']
        isecs = ihmsfs['s']
        ifracs = ihmsfs['f']

        fmt = ('{0:04d} {1:02d} {2:02d} {3:02d} {4:02d} {5:02d} '
               '0.{6:0' + str(self.precision) + 'd}')
        outs = []
        for iy, im, id, ihr, imin, isec, ifracsec in np.nditer(
                [iys, ims, ids, ihrs, imins, isecs, ifracs]):
            outs.append(fmt.format(int(iy), int(im), int(id), int(ihr),
                                   int(imin), int(isec), int(ifracsec)))

        return np.array(outs).reshape(self.jd1.shape) 

def _get_bp_indexes_labranchor(self, soi):
        """
        Get indexes of branch point regions in given sequences.

        :param soi: batch of sequences of interest for introns (intron-3..intron+6)
        :return: array of predicted bp indexes
        """
        encoded = [onehot(str(seq)[self.acc_i - 70:self.acc_i]) for seq in np.nditer(soi)]
        labr_in = np.stack(encoded, axis=0)
        out = self.labranchor.predict_on_batch(labr_in)
        # for each row, pick the base with max branchpoint probability, and get its index
        max_indexes = np.apply_along_axis(lambda x: self.acc_i - 70 + np.argmax(x), axis=1, arr=out)
        # self.write_bp(max_indexes)
        return max_indexes

# TODO boilerplate
#    def write_bp(self, max_indexes):
#        max_indexes = [str(seq) for seq in np.nditer(max_indexes)]
#        with open(''.join([this_dir, "/../customBP/example_files/bp_idx_chr21_labr.txt"]), "a") as bp_idx_file:
#            bp_idx_file.write('\n'.join(max_indexes))
#            bp_idx_file.write('\n')
#            bp_idx_file.close() 

def numerical_gradient(f, x):
    h = 1e-4  # 0.0001
    grad = np.zeros_like(x)

    it = np.nditer(x, flags=['multi_index'], op_flags=['readwrite'])
    while not it.finished:
        idx = it.multi_index
        tmp_val = x[idx]
        x[idx] = float(tmp_val) + h
        fxh1 = f(x)  # f(x+h)

        x[idx] = tmp_val - h
        fxh2 = f(x)  # f(x-h)
        grad[idx] = (fxh1 - fxh2) / (2 * h)

        x[idx] = tmp_val  # 还原值
        it.iternext()

    return grad 

def assign_each(the_input, function):
    """Return ndarray composed of passing each array value through some function"""
    if function is None:
        output = np.array(the_input)
    else:
        it_input = np.nditer(the_input, flags=['f_index'])

        output = np.zeros(the_input.shape)
        it_out = np.nditer(output, flags=['f_index'], op_flags=['writeonly'])

        while not it_input.finished:
            val_input = it_input[0]
            it_out[0] = function(val_input)
            it_input.iternext()
            it_out.iternext()

    return output 

def assign_each2(input1, input2, function):
    """Return ndarray composed of passing two array values through some function"""
    if function is None:
        output = np.array(input1)
    else:
        assert input1.shape == input2.shape
        it_input1 = np.nditer(input1, flags=['f_index'])
        it_input2 = np.nditer(input2, flags=['f_index'])

        output = np.zeros(input1.shape)
        it_out = np.nditer(output, flags=['f_index'], op_flags=['writeonly'])

        while not it_input1.finished:
            val_input1 = it_input1[0]
            val_input2 = it_input2[0]
            it_out[0] = function(val_input1, val_input2)
            it_input1.iternext()
            it_input2.iternext()
            it_out.iternext()

    return output 

def test_card(self):
        x = Card(5, k=3, M=1)
        p = Problem(Maximize(cp.sum(x)),
            [x <= 1, x >= 0])
        result = p.solve(method="NC-ADMM")
        self.assertAlmostEqual(result[0], 3)
        for v in np.nditer(x.value):
            self.assertAlmostEqual(v*(1-v), 0)
        self.assertAlmostEqual(x.value.sum(), 3)

        #should be equivalent to x == choose
        x = Variable((5, 4))
        c = Choose(5, 4, k=4)
        b = Boolean(5, 4)
        p = Problem(Minimize(sum(1-x) + sum(x)),
                    [x == c, x == b])
        result = p.solve(method="NC-ADMM", solver=CVXOPT)
        self.assertAlmostEqual(result[0], 20)
        for i in range(x.shape[0]):
            for j in range(x.shape[1]):
                v = x.value[i, j]
                self.assertAlmostEqual(v*(1-v), 0)

    # Test permutation variable. 

def set_jds(self, val1, val2):
        """Parse the time strings contained in val1 and set jd1, jd2"""
        iterator = np.nditer([val1, None, None, None, None, None, None],
                             op_dtypes=([val1.dtype] + 5 * [np.intc]
                                        + [np.double]))
        try:
            for val, iy, im, id, ihr, imin, dsec in iterator:
                timestr = val.item()
                components = timestr.split()
                iy[...], im[...], id[...], ihr[...], imin[...], sec = (
                    int(component) for component in components[:-1])
                dsec[...] = sec + float(components[-1])
        except Exception:
            raise ValueError('Time {0} does not match {1} format'
                             .format(timestr, self.name))

        self.jd1, self.jd2 = erfa.dtf2d(
            self.scale.upper().encode('utf8'), *iterator.operands[1:]) 

def test_iter_allocate_output_subtype():
    # Make sure that the subtype with priority wins
    # 2018-04-29: moved here from core.tests.test_nditer, given the
    # matrix specific shape test.

    # matrix vs ndarray
    a = np.matrix([[1, 2], [3, 4]])
    b = np.arange(4).reshape(2, 2).T
    i = np.nditer([a, b, None], [],
                  [['readonly'], ['readonly'], ['writeonly', 'allocate']])
    assert_(type(i.operands[2]) is np.matrix)
    assert_(type(i.operands[2]) is not np.ndarray)
    assert_equal(i.operands[2].shape, (2, 2))

    # matrix always wants things to be 2D
    b = np.arange(4).reshape(1, 2, 2)
    assert_raises(RuntimeError, np.nditer, [a, b, None], [],
                  [['readonly'], ['readonly'], ['writeonly', 'allocate']])
    # but if subtypes are disabled, the result can still work
    i = np.nditer([a, b, None], [],
                  [['readonly'], ['readonly'],
                   ['writeonly', 'allocate', 'no_subtype']])
    assert_(type(i.operands[2]) is np.ndarray)
    assert_(type(i.operands[2]) is not np.matrix)
    assert_equal(i.operands[2].shape, (1, 2, 2)) 

def _broadcast_to(array, shape, subok, readonly):
    shape = tuple(shape) if np.iterable(shape) else (shape,)
    array = np.array(array, copy=False, subok=subok)
    if not shape and array.shape:
        raise ValueError('cannot broadcast a non-scalar to a scalar array')
    if any(size < 0 for size in shape):
        raise ValueError('all elements of broadcast shape must be non-'
                         'negative')
    needs_writeable = not readonly and array.flags.writeable
    extras = ['reduce_ok'] if needs_writeable else []
    op_flag = 'readwrite' if needs_writeable else 'readonly'
    it = np.nditer(
        (array,), flags=['multi_index', 'refs_ok', 'zerosize_ok'] + extras,
        op_flags=[op_flag], itershape=shape, order='C')
    with it:
        # never really has writebackifcopy semantics
        broadcast = it.itviews[0]
    result = _maybe_view_as_subclass(array, broadcast)
    if needs_writeable and not result.flags.writeable:
        result.flags.writeable = True
    return result 

def _broadcast_shape(*args):
    """Returns the shape of the arrays that would result from broadcasting the
    supplied arrays against each other.
    """
    if not args:
        return ()
    # use the old-iterator because np.nditer does not handle size 0 arrays
    # consistently
    b = np.broadcast(*args[:32])
    # unfortunately, it cannot handle 32 or more arguments directly
    for pos in range(32, len(args), 31):
        # ironically, np.broadcast does not properly handle np.broadcast
        # objects (it treats them as scalars)
        # use broadcasting to avoid allocating the full array
        b = broadcast_to(0, b.shape)
        b = np.broadcast(b, *args[pos:(pos + 31)])
    return b.shape 

def test_iter_no_inner_dim_coalescing():
    # Check no_inner iterators whose dimensions may not coalesce completely

    # Skipping the last element in a dimension prevents coalescing
    # with the next-bigger dimension
    a = arange(24).reshape(2, 3, 4)[:,:, :-1]
    i = nditer(a, ['external_loop'], [['readonly']])
    assert_equal(i.ndim, 2)
    assert_equal(i[0].shape, (3,))
    a = arange(24).reshape(2, 3, 4)[:, :-1,:]
    i = nditer(a, ['external_loop'], [['readonly']])
    assert_equal(i.ndim, 2)
    assert_equal(i[0].shape, (8,))
    a = arange(24).reshape(2, 3, 4)[:-1,:,:]
    i = nditer(a, ['external_loop'], [['readonly']])
    assert_equal(i.ndim, 1)
    assert_equal(i[0].shape, (12,))

    # Even with lots of 1-sized dimensions, should still coalesce
    a = arange(24).reshape(1, 1, 2, 1, 1, 3, 1, 1, 4, 1, 1)
    i = nditer(a, ['external_loop'], [['readonly']])
    assert_equal(i.ndim, 1)
    assert_equal(i[0].shape, (24,)) 

def test_iter_scalar_cast_errors():
    # Check that invalid casts are caught

    # Need to allow copying/buffering for write casts of scalars to occur
    assert_raises(TypeError, nditer, np.float32(2), [],
                [['readwrite']], op_dtypes=[np.dtype('f8')])
    assert_raises(TypeError, nditer, 2.5, [],
                [['readwrite']], op_dtypes=[np.dtype('f4')])
    # 'f8' -> 'f4' isn't a safe cast if the value would overflow
    assert_raises(TypeError, nditer, np.float64(1e60), [],
                [['readonly']],
                casting='safe',
                op_dtypes=[np.dtype('f4')])
    # 'f4' -> 'i4' is neither a safe nor a same-kind cast
    assert_raises(TypeError, nditer, np.float32(2), [],
                [['readonly']],
                casting='same_kind',
                op_dtypes=[np.dtype('i4')]) 

def test_iter_op_axes_errors():
    # Check that custom axes throws errors for bad inputs

    # Wrong number of items in op_axes
    a = arange(6).reshape(2, 3)
    assert_raises(ValueError, nditer, [a, a], [], [['readonly']]*2,
                                    op_axes=[[0], [1], [0]])
    # Out of bounds items in op_axes
    assert_raises(ValueError, nditer, [a, a], [], [['readonly']]*2,
                                    op_axes=[[2, 1], [0, 1]])
    assert_raises(ValueError, nditer, [a, a], [], [['readonly']]*2,
                                    op_axes=[[0, 1], [2, -1]])
    # Duplicate items in op_axes
    assert_raises(ValueError, nditer, [a, a], [], [['readonly']]*2,
                                    op_axes=[[0, 0], [0, 1]])
    assert_raises(ValueError, nditer, [a, a], [], [['readonly']]*2,
                                    op_axes=[[0, 1], [1, 1]])

    # Different sized arrays in op_axes
    assert_raises(ValueError, nditer, [a, a], [], [['readonly']]*2,
                                    op_axes=[[0, 1], [0, 1, 0]])

    # Non-broadcastable dimensions in the result
    assert_raises(ValueError, nditer, [a, a], [], [['readonly']]*2,
                                    op_axes=[[0, 1], [1, 0]]) 

def test_iter_allocate_output_types_promotion():
    # Check type promotion of automatic outputs

    i = nditer([array([3], dtype='f4'), array([0], dtype='f8'), None], [],
                    [['readonly']]*2+[['writeonly', 'allocate']])
    assert_equal(i.dtypes[2], np.dtype('f8'))
    i = nditer([array([3], dtype='i4'), array([0], dtype='f4'), None], [],
                    [['readonly']]*2+[['writeonly', 'allocate']])
    assert_equal(i.dtypes[2], np.dtype('f8'))
    i = nditer([array([3], dtype='f4'), array(0, dtype='f8'), None], [],
                    [['readonly']]*2+[['writeonly', 'allocate']])
    assert_equal(i.dtypes[2], np.dtype('f4'))
    i = nditer([array([3], dtype='u4'), array(0, dtype='i4'), None], [],
                    [['readonly']]*2+[['writeonly', 'allocate']])
    assert_equal(i.dtypes[2], np.dtype('u4'))
    i = nditer([array([3], dtype='u4'), array(-12, dtype='i4'), None], [],
                    [['readonly']]*2+[['writeonly', 'allocate']])
    assert_equal(i.dtypes[2], np.dtype('i8')) 

def test_iter_write_buffering():
    # Test that buffering of writes is working

    # F-order swapped array
    a = np.arange(24).reshape(2, 3, 4).T.newbyteorder().byteswap()
    i = nditer(a, ['buffered'],
                   [['readwrite', 'nbo', 'aligned']],
                   casting='equiv',
                   order='C',
                   buffersize=16)
    x = 0
    with i:
        while not i.finished:
            i[0] = x
            x += 1
            i.iternext()
    assert_equal(a.ravel(order='C'), np.arange(24)) 

def test_iter_buffering_string():
    # Safe casting disallows shrinking strings
    a = np.array(['abc', 'a', 'abcd'], dtype=np.bytes_)
    assert_equal(a.dtype, np.dtype('S4'))
    assert_raises(TypeError, nditer, a, ['buffered'], ['readonly'],
                  op_dtypes='S2')
    i = nditer(a, ['buffered'], ['readonly'], op_dtypes='S6')
    assert_equal(i[0], b'abc')
    assert_equal(i[0].dtype, np.dtype('S6'))

    a = np.array(['abc', 'a', 'abcd'], dtype=np.unicode)
    assert_equal(a.dtype, np.dtype('U4'))
    assert_raises(TypeError, nditer, a, ['buffered'], ['readonly'],
                    op_dtypes='U2')
    i = nditer(a, ['buffered'], ['readonly'], op_dtypes='U6')
    assert_equal(i[0], u'abc')
    assert_equal(i[0].dtype, np.dtype('U6')) 

def test_close_equivalent():
    ''' using a context amanger and using nditer.close are equivalent
    '''
    def add_close(x, y, out=None):
        addop = np.add
        it = np.nditer([x, y, out], [],
                    [['readonly'], ['readonly'], ['writeonly','allocate']])
        for (a, b, c) in it:
            addop(a, b, out=c)
        ret = it.operands[2]
        it.close()
        return ret

    def add_context(x, y, out=None):
        addop = np.add
        it = np.nditer([x, y, out], [],
                    [['readonly'], ['readonly'], ['writeonly','allocate']])
        with it:
            for (a, b, c) in it:
                addop(a, b, out=c)
            return it.operands[2]
    z = add_close(range(5), range(5))
    assert_equal(z, range(0, 10, 2))
    z = add_context(range(5), range(5))
    assert_equal(z, range(0, 10, 2)) 

def _broadcast_to(array, shape, subok, readonly):
    shape = tuple(shape) if np.iterable(shape) else (shape,)
    array = np.array(array, copy=False, subok=subok)
    if not shape and array.shape:
        raise ValueError('cannot broadcast a non-scalar to a scalar array')
    if any(size < 0 for size in shape):
        raise ValueError('all elements of broadcast shape must be non-'
                         'negative')
    needs_writeable = not readonly and array.flags.writeable
    extras = ['reduce_ok'] if needs_writeable else []
    op_flag = 'readwrite' if needs_writeable else 'readonly'
    it = np.nditer(
        (array,), flags=['multi_index', 'refs_ok', 'zerosize_ok'] + extras,
        op_flags=[op_flag], itershape=shape, order='C')
    with it:
        # never really has writebackifcopy semantics
        broadcast = it.itviews[0]
    result = _maybe_view_as_subclass(array, broadcast)
    if needs_writeable and not result.flags.writeable:
        result.flags.writeable = True
    return result 

def fermi_dirac_occupations(telec, ksn2e, fermi_energy):
  """ Occupations according to the Fermi-Dirac distribution function. """
  assert telec>0.0
  ksn2f = copy(ksn2e)
  for e in nditer(ksn2f, op_flags=['readwrite']): e[...] = fermi_dirac(telec, e, fermi_energy)

  return ksn2f 

def test_permutation(self):
        x = Variable((1, 5))
        c = np.array([[1,2,3,4,5]])
        perm = Assign(5, 5)
        p = Problem(Minimize(cp.sum(x)), [x == c*perm])
        result = p.solve(method="NC-ADMM")
        self.assertAlmostEqual(result[0], 15)
        assert_array_almost_equal(sorted(np.nditer(x.value)), c.ravel()) 

def test_iter_refcount():
    # Make sure the iterator doesn't leak

    # Basic
    a = arange(6)
    dt = np.dtype('f4').newbyteorder()
    rc_a = sys.getrefcount(a)
    rc_dt = sys.getrefcount(dt)
    with nditer(a, [],
                [['readwrite', 'updateifcopy']],
                casting='unsafe',
                op_dtypes=[dt]) as it:
        assert_(not it.iterationneedsapi)
        assert_(sys.getrefcount(a) > rc_a)
        assert_(sys.getrefcount(dt) > rc_dt)
    # del 'it'
    it = None
    assert_equal(sys.getrefcount(a), rc_a)
    assert_equal(sys.getrefcount(dt), rc_dt)

    # With a copy
    a = arange(6, dtype='f4')
    dt = np.dtype('f4')
    rc_a = sys.getrefcount(a)
    rc_dt = sys.getrefcount(dt)
    it = nditer(a, [],
                [['readwrite']],
                op_dtypes=[dt])
    rc2_a = sys.getrefcount(a)
    rc2_dt = sys.getrefcount(dt)
    it2 = it.copy()
    assert_(sys.getrefcount(a) > rc2_a)
    assert_(sys.getrefcount(dt) > rc2_dt)
    it = None
    assert_equal(sys.getrefcount(a), rc2_a)
    assert_equal(sys.getrefcount(dt), rc2_dt)
    it2 = None
    assert_equal(sys.getrefcount(a), rc_a)
    assert_equal(sys.getrefcount(dt), rc_dt)

    del it2  # avoid pyflakes unused variable warning 

def test_iter_c_order():
    # Test forcing C order

    # Test the ordering for 1-D to 5-D shapes
    for shape in [(5,), (3, 4), (2, 3, 4), (2, 3, 4, 3), (2, 3, 2, 2, 3)]:
        a = arange(np.prod(shape))
        # Test each combination of positive and negative strides
        for dirs in range(2**len(shape)):
            dirs_index = [slice(None)]*len(shape)
            for bit in range(len(shape)):
                if ((2**bit) & dirs):
                    dirs_index[bit] = slice(None, None, -1)
            dirs_index = tuple(dirs_index)

            aview = a.reshape(shape)[dirs_index]
            # C-order
            i = nditer(aview, order='C')
            assert_equal([x for x in i], aview.ravel(order='C'))
            # Fortran-order
            i = nditer(aview.T, order='C')
            assert_equal([x for x in i], aview.T.ravel(order='C'))
            # Other order
            if len(shape) > 2:
                i = nditer(aview.swapaxes(0, 1), order='C')
                assert_equal([x for x in i],
                                    aview.swapaxes(0, 1).ravel(order='C')) 

def test_iter_f_order():
    # Test forcing F order

    # Test the ordering for 1-D to 5-D shapes
    for shape in [(5,), (3, 4), (2, 3, 4), (2, 3, 4, 3), (2, 3, 2, 2, 3)]:
        a = arange(np.prod(shape))
        # Test each combination of positive and negative strides
        for dirs in range(2**len(shape)):
            dirs_index = [slice(None)]*len(shape)
            for bit in range(len(shape)):
                if ((2**bit) & dirs):
                    dirs_index[bit] = slice(None, None, -1)
            dirs_index = tuple(dirs_index)

            aview = a.reshape(shape)[dirs_index]
            # C-order
            i = nditer(aview, order='F')
            assert_equal([x for x in i], aview.ravel(order='F'))
            # Fortran-order
            i = nditer(aview.T, order='F')
            assert_equal([x for x in i], aview.T.ravel(order='F'))
            # Other order
            if len(shape) > 2:
                i = nditer(aview.swapaxes(0, 1), order='F')
                assert_equal([x for x in i],
                                    aview.swapaxes(0, 1).ravel(order='F')) 

def test_iter_c_or_f_order():
    # Test forcing any contiguous (C or F) order

    # Test the ordering for 1-D to 5-D shapes
    for shape in [(5,), (3, 4), (2, 3, 4), (2, 3, 4, 3), (2, 3, 2, 2, 3)]:
        a = arange(np.prod(shape))
        # Test each combination of positive and negative strides
        for dirs in range(2**len(shape)):
            dirs_index = [slice(None)]*len(shape)
            for bit in range(len(shape)):
                if ((2**bit) & dirs):
                    dirs_index[bit] = slice(None, None, -1)
            dirs_index = tuple(dirs_index)

            aview = a.reshape(shape)[dirs_index]
            # C-order
            i = nditer(aview, order='A')
            assert_equal([x for x in i], aview.ravel(order='A'))
            # Fortran-order
            i = nditer(aview.T, order='A')
            assert_equal([x for x in i], aview.T.ravel(order='A'))
            # Other order
            if len(shape) > 2:
                i = nditer(aview.swapaxes(0, 1), order='A')
                assert_equal([x for x in i],
                                    aview.swapaxes(0, 1).ravel(order='A')) 

def test_iter_best_order_multi_index_1d():
    # The multi-indices should be correct with any reordering

    a = arange(4)
    # 1D order
    i = nditer(a, ['multi_index'], [['readonly']])
    assert_equal(iter_multi_index(i), [(0,), (1,), (2,), (3,)])
    # 1D reversed order
    i = nditer(a[::-1], ['multi_index'], [['readonly']])
    assert_equal(iter_multi_index(i), [(3,), (2,), (1,), (0,)]) 

def test_iter_best_order_multi_index_2d():
    # The multi-indices should be correct with any reordering

    a = arange(6)
    # 2D C-order
    i = nditer(a.reshape(2, 3), ['multi_index'], [['readonly']])
    assert_equal(iter_multi_index(i), [(0, 0), (0, 1), (0, 2), (1, 0), (1, 1), (1, 2)])
    # 2D Fortran-order
    i = nditer(a.reshape(2, 3).copy(order='F'), ['multi_index'], [['readonly']])
    assert_equal(iter_multi_index(i), [(0, 0), (1, 0), (0, 1), (1, 1), (0, 2), (1, 2)])
    # 2D reversed C-order
    i = nditer(a.reshape(2, 3)[::-1], ['multi_index'], [['readonly']])
    assert_equal(iter_multi_index(i), [(1, 0), (1, 1), (1, 2), (0, 0), (0, 1), (0, 2)])
    i = nditer(a.reshape(2, 3)[:, ::-1], ['multi_index'], [['readonly']])
    assert_equal(iter_multi_index(i), [(0, 2), (0, 1), (0, 0), (1, 2), (1, 1), (1, 0)])
    i = nditer(a.reshape(2, 3)[::-1, ::-1], ['multi_index'], [['readonly']])
    assert_equal(iter_multi_index(i), [(1, 2), (1, 1), (1, 0), (0, 2), (0, 1), (0, 0)])
    # 2D reversed Fortran-order
    i = nditer(a.reshape(2, 3).copy(order='F')[::-1], ['multi_index'], [['readonly']])
    assert_equal(iter_multi_index(i), [(1, 0), (0, 0), (1, 1), (0, 1), (1, 2), (0, 2)])
    i = nditer(a.reshape(2, 3).copy(order='F')[:, ::-1],
                                                   ['multi_index'], [['readonly']])
    assert_equal(iter_multi_index(i), [(0, 2), (1, 2), (0, 1), (1, 1), (0, 0), (1, 0)])
    i = nditer(a.reshape(2, 3).copy(order='F')[::-1, ::-1],
                                                   ['multi_index'], [['readonly']])
    assert_equal(iter_multi_index(i), [(1, 2), (0, 2), (1, 1), (0, 1), (1, 0), (0, 0)]) 

def test_iter_best_order_c_index_1d():
    # The C index should be correct with any reordering

    a = arange(4)
    # 1D order
    i = nditer(a, ['c_index'], [['readonly']])
    assert_equal(iter_indices(i), [0, 1, 2, 3])
    # 1D reversed order
    i = nditer(a[::-1], ['c_index'], [['readonly']])
    assert_equal(iter_indices(i), [3, 2, 1, 0]) 

def test_iter_best_order_c_index_2d():
    # The C index should be correct with any reordering

    a = arange(6)
    # 2D C-order
    i = nditer(a.reshape(2, 3), ['c_index'], [['readonly']])
    assert_equal(iter_indices(i), [0, 1, 2, 3, 4, 5])
    # 2D Fortran-order
    i = nditer(a.reshape(2, 3).copy(order='F'),
                                    ['c_index'], [['readonly']])
    assert_equal(iter_indices(i), [0, 3, 1, 4, 2, 5])
    # 2D reversed C-order
    i = nditer(a.reshape(2, 3)[::-1], ['c_index'], [['readonly']])
    assert_equal(iter_indices(i), [3, 4, 5, 0, 1, 2])
    i = nditer(a.reshape(2, 3)[:, ::-1], ['c_index'], [['readonly']])
    assert_equal(iter_indices(i), [2, 1, 0, 5, 4, 3])
    i = nditer(a.reshape(2, 3)[::-1, ::-1], ['c_index'], [['readonly']])
    assert_equal(iter_indices(i), [5, 4, 3, 2, 1, 0])
    # 2D reversed Fortran-order
    i = nditer(a.reshape(2, 3).copy(order='F')[::-1],
                                    ['c_index'], [['readonly']])
    assert_equal(iter_indices(i), [3, 0, 4, 1, 5, 2])
    i = nditer(a.reshape(2, 3).copy(order='F')[:, ::-1],
                                    ['c_index'], [['readonly']])
    assert_equal(iter_indices(i), [2, 5, 1, 4, 0, 3])
    i = nditer(a.reshape(2, 3).copy(order='F')[::-1, ::-1],
                                    ['c_index'], [['readonly']])
    assert_equal(iter_indices(i), [5, 2, 4, 1, 3, 0]) 

def test_iter_best_order_c_index_3d():
    # The C index should be correct with any reordering

    a = arange(12)
    # 3D C-order
    i = nditer(a.reshape(2, 3, 2), ['c_index'], [['readonly']])
    assert_equal(iter_indices(i),
                            [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11])
    # 3D Fortran-order
    i = nditer(a.reshape(2, 3, 2).copy(order='F'),
                                    ['c_index'], [['readonly']])
    assert_equal(iter_indices(i),
                            [0, 6, 2, 8, 4, 10, 1, 7, 3, 9, 5, 11])
    # 3D reversed C-order
    i = nditer(a.reshape(2, 3, 2)[::-1], ['c_index'], [['readonly']])
    assert_equal(iter_indices(i),
                            [6, 7, 8, 9, 10, 11, 0, 1, 2, 3, 4, 5])
    i = nditer(a.reshape(2, 3, 2)[:, ::-1], ['c_index'], [['readonly']])
    assert_equal(iter_indices(i),
                            [4, 5, 2, 3, 0, 1, 10, 11, 8, 9, 6, 7])
    i = nditer(a.reshape(2, 3, 2)[:,:, ::-1], ['c_index'], [['readonly']])
    assert_equal(iter_indices(i),
                            [1, 0, 3, 2, 5, 4, 7, 6, 9, 8, 11, 10])
    # 3D reversed Fortran-order
    i = nditer(a.reshape(2, 3, 2).copy(order='F')[::-1],
                                    ['c_index'], [['readonly']])
    assert_equal(iter_indices(i),
                            [6, 0, 8, 2, 10, 4, 7, 1, 9, 3, 11, 5])
    i = nditer(a.reshape(2, 3, 2).copy(order='F')[:, ::-1],
                                    ['c_index'], [['readonly']])
    assert_equal(iter_indices(i),
                            [4, 10, 2, 8, 0, 6, 5, 11, 3, 9, 1, 7])
    i = nditer(a.reshape(2, 3, 2).copy(order='F')[:,:, ::-1],
                                    ['c_index'], [['readonly']])
    assert_equal(iter_indices(i),
                            [1, 7, 3, 9, 5, 11, 0, 6, 2, 8, 4, 10]) 

def test_iter_best_order_f_index_1d():
    # The Fortran index should be correct with any reordering

    a = arange(4)
    # 1D order
    i = nditer(a, ['f_index'], [['readonly']])
    assert_equal(iter_indices(i), [0, 1, 2, 3])
    # 1D reversed order
    i = nditer(a[::-1], ['f_index'], [['readonly']])
    assert_equal(iter_indices(i), [3, 2, 1, 0])