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test_stride_tricks.py
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import numpy as np from numpy.core._rational_tests import rational from numpy.testing import ( assert_equal, assert_array_equal, assert_raises, assert_, assert_raises_regex, assert_warns, ) from numpy.lib.stride_tricks import ( as_strided, broadcast_arrays, _broadcast_shape, broadcast_to, broadcast_shapes, sliding_window_view, ) import pytest def assert_shapes_correct(input_shapes, expected_shape): # Broadcast a list of arrays with the given input shapes and check the # common output shape. inarrays = [np.zeros(s) for s in input_shapes] outarrays = broadcast_arrays(*inarrays) outshapes = [a.shape for a in outarrays] expected = [expected_shape] * len(inarrays) assert_equal(outshapes, expected) def assert_incompatible_shapes_raise(input_shapes): # Broadcast a list of arrays with the given (incompatible) input shapes # and check that they raise a ValueError. inarrays = [np.zeros(s) for s in input_shapes] assert_raises(ValueError, broadcast_arrays, *inarrays) def assert_same_as_ufunc(shape0, shape1, transposed=False, flipped=False): # Broadcast two shapes against each other and check that the data layout # is the same as if a ufunc did the broadcasting. x0 = np.zeros(shape0, dtype=int) # Note that multiply.reduce's identity element is 1.0, so when shape1==(), # this gives the desired n==1. n = int(np.multiply.reduce(shape1)) x1 = np.arange(n).reshape(shape1) if transposed: x0 = x0.T x1 = x1.T if flipped: x0 = x0[::-1] x1 = x1[::-1] # Use the add ufunc to do the broadcasting. Since we're adding 0s to x1, the # result should be exactly the same as the broadcasted view of x1. y = x0 + x1 b0, b1 = broadcast_arrays(x0, x1) assert_array_equal(y, b1) def test_same(): x = np.arange(10) y = np.arange(10) bx, by = broadcast_arrays(x, y) assert_array_equal(x, bx) assert_array_equal(y, by) def test_broadcast_kwargs(): # ensure that a TypeError is appropriately raised when # np.broadcast_arrays() is called with any keyword # argument other than 'subok' x = np.arange(10) y = np.arange(10) with assert_raises_regex(TypeError, 'got an unexpected keyword'): broadcast_arrays(x, y, dtype='float64') def test_one_off(): x = np.array([[1, 2, 3]]) y = np.array([[1], [2], [3]]) bx, by = broadcast_arrays(x, y) bx0 = np.array([[1, 2, 3], [1, 2, 3], [1, 2, 3]]) by0 = bx0.T assert_array_equal(bx0, bx) assert_array_equal(by0, by) def test_same_input_shapes(): # Check that the final shape is just the input shape. data = [ (), (1,), (3,), (0, 1), (0, 3), (1, 0), (3, 0), (1, 3), (3, 1), (3, 3), ] for shape in data: input_shapes = [shape] # Single input. assert_shapes_correct(input_shapes, shape) # Double input. input_shapes2 = [shape, shape] assert_shapes_correct(input_shapes2, shape) # Triple input. input_shapes3 = [shape, shape, shape] assert_shapes_correct(input_shapes3, shape) def test_two_compatible_by_ones_input_shapes(): # Check that two different input shapes of the same length, but some have # ones, broadcast to the correct shape. data = [ [[(1,), (3,)], (3,)], [[(1, 3), (3, 3)], (3, 3)], [[(3, 1), (3, 3)], (3, 3)], [[(1, 3), (3, 1)], (3, 3)], [[(1, 1), (3, 3)], (3, 3)], [[(1, 1), (1, 3)], (1, 3)], [[(1, 1), (3, 1)], (3, 1)], [[(1, 0), (0, 0)], (0, 0)], [[(0, 1), (0, 0)], (0, 0)], [[(1, 0), (0, 1)], (0, 0)], [[(1, 1), (0, 0)], (0, 0)], [[(1, 1), (1, 0)], (1, 0)], [[(1, 1), (0, 1)], (0, 1)], ] for input_shapes, expected_shape in data: assert_shapes_correct(input_shapes, expected_shape) # Reverse the input shapes since broadcasting should be symmetric. assert_shapes_correct(input_shapes[::-1], expected_shape) def test_two_compatible_by_prepending_ones_input_shapes(): # Check that two different input shapes (of different lengths) broadcast # to the correct shape. data = [ [[(), (3,)], (3,)], [[(3,), (3, 3)], (3, 3)], [[(3,), (3, 1)], (3, 3)], [[(1,), (3, 3)], (3, 3)], [[(), (3, 3)], (3, 3)], [[(1, 1), (3,)], (1, 3)], [[(1,), (3, 1)], (3, 1)], [[(1,), (1, 3)], (1, 3)], [[(), (1, 3)], (1, 3)], [[(), (3, 1)], (3, 1)], [[(), (0,)], (0,)], [[(0,), (0, 0)], (0, 0)], [[(0,), (0, 1)], (0, 0)], [[(1,), (0, 0)], (0, 0)], [[(), (0, 0)], (0, 0)], [[(1, 1), (0,)], (1, 0)], [[(1,), (0, 1)], (0, 1)], [[(1,), (1, 0)], (1, 0)], [[(), (1, 0)], (1, 0)], [[(), (0, 1)], (0, 1)], ] for input_shapes, expected_shape in data: assert_shapes_correct(input_shapes, expected_shape) # Reverse the input shapes since broadcasting should be symmetric. assert_shapes_correct(input_shapes[::-1], expected_shape) def test_incompatible_shapes_raise_valueerror(): # Check that a ValueError is raised for incompatible shapes. data = [ [(3,), (4,)], [(2, 3), (2,)], [(3,), (3,), (4,)], [(1, 3, 4), (2, 3, 3)], ] for input_shapes in data: assert_incompatible_shapes_raise(input_shapes) # Reverse the input shapes since broadcasting should be symmetric. assert_incompatible_shapes_raise(input_shapes[::-1]) def test_same_as_ufunc(): # Check that the data layout is the same as if a ufunc did the operation. data = [ [[(1,), (3,)], (3,)], [[(1, 3), (3, 3)], (3, 3)], [[(3, 1), (3, 3)], (3, 3)], [[(1, 3), (3, 1)], (3, 3)], [[(1, 1), (3, 3)], (3, 3)], [[(1, 1), (1, 3)], (1, 3)], [[(1, 1), (3, 1)], (3, 1)], [[(1, 0), (0, 0)], (0, 0)], [[(0, 1), (0, 0)], (0, 0)], [[(1, 0), (0, 1)], (0, 0)], [[(1, 1), (0, 0)], (0, 0)], [[(1, 1), (1, 0)], (1, 0)], [[(1, 1), (0, 1)], (0, 1)], [[(), (3,)], (3,)], [[(3,), (3, 3)], (3, 3)], [[(3,), (3, 1)], (3, 3)], [[(1,), (3, 3)], (3, 3)], [[(), (3, 3)], (3, 3)], [[(1, 1), (3,)], (1, 3)], [[(1,), (3, 1)], (3, 1)], [[(1,), (1, 3)], (1, 3)], [[(), (1, 3)], (1, 3)], [[(), (3, 1)], (3, 1)], [[(), (0,)], (0,)], [[(0,), (0, 0)], (0, 0)], [[(0,), (0, 1)], (0, 0)], [[(1,), (0, 0)], (0, 0)], [[(), (0, 0)], (0, 0)], [[(1, 1), (0,)], (1, 0)], [[(1,), (0, 1)], (0, 1)], [[(1,), (1, 0)], (1, 0)], [[(), (1, 0)], (1, 0)], [[(), (0, 1)], (0, 1)], ] for input_shapes, expected_shape in data: assert_same_as_ufunc(input_shapes[0], input_shapes[1], "Shapes: %s %s" % (input_shapes[0], input_shapes[1])) # Reverse the input shapes since broadcasting should be symmetric. assert_same_as_ufunc(input_shapes[1], input_shapes[0]) # Try them transposed, too. assert_same_as_ufunc(input_shapes[0], input_shapes[1], True) # ... and flipped for non-rank-0 inputs in order to test negative # strides. if () not in input_shapes: assert_same_as_ufunc(input_shapes[0], input_shapes[1], False, True) assert_same_as_ufunc(input_shapes[0], input_shapes[1], True, True) def test_broadcast_to_succeeds(): data = [ [np.array(0), (0,), np.array(0)], [np.array(0), (1,), np.zeros(1)], [np.array(0), (3,), np.zeros(3)], [np.ones(1), (1,), np.ones(1)], [np.ones(1), (2,), np.ones(2)], [np.ones(1), (1, 2, 3), np.ones((1, 2, 3))], [np.arange(3), (3,), np.arange(3)], [np.arange(3), (1, 3), np.arange(3).reshape(1, -1)], [np.arange(3), (2, 3), np.array([[0, 1, 2], [0, 1, 2]])], # test if shape is not a tuple [np.ones(0), 0, np.ones(0)], [np.ones(1), 1, np.ones(1)], [np.ones(1), 2, np.ones(2)], # these cases with size 0 are strange, but they reproduce the behavior # of broadcasting with ufuncs (see test_same_as_ufunc above) [np.ones(1), (0,), np.ones(0)], [np.ones((1, 2)), (0, 2), np.ones((0, 2))], [np.ones((2, 1)), (2, 0), np.ones((2, 0))], ] for input_array, shape, expected in data: actual = broadcast_to(input_array, shape) assert_array_equal(expected, actual) def test_broadcast_to_raises(): data = [ [(0,), ()], [(1,), ()], [(3,), ()], [(3,), (1,)], [(3,), (2,)], [(3,), (4,)], [(1, 2), (2, 1)], [(1, 1), (1,)], [(1,), -1], [(1,), (-1,)], [(1, 2), (-1, 2)], ] for orig_shape, target_shape in data: arr = np.zeros(orig_shape) assert_raises(ValueError, lambda: broadcast_to(arr, target_shape)) def test_broadcast_shape(): # tests internal _broadcast_shape # _broadcast_shape is already exercised indirectly by broadcast_arrays # _broadcast_shape is also exercised by the public broadcast_shapes function assert_equal(_broadcast_shape(), ()) assert_equal(_broadcast_shape([1, 2]), (2,)) assert_equal(_broadcast_shape(np.ones((1, 1))), (1, 1)) assert_equal(_broadcast_shape(np.ones((1, 1)), np.ones((3, 4))), (3, 4)) assert_equal(_broadcast_shape(*([np.ones((1, 2))] * 32)), (1, 2)) assert_equal(_broadcast_shape(*([np.ones((1, 2))] * 100)), (1, 2)) # regression tests for gh-5862 assert_equal(_broadcast_shape(*([np.ones(2)] * 32 + [1])), (2,)) bad_args = [np.ones(2)] * 32 + [np.ones(3)] * 32 assert_raises(ValueError, lambda: _broadcast_shape(*bad_args)) def test_broadcast_shapes_succeeds(): # tests public broadcast_shapes data = [ [[], ()], [[()], ()], [[(7,)], (7,)], [[(1, 2), (2,)], (1, 2)], [[(1, 1)], (1, 1)], [[(1, 1), (3, 4)], (3, 4)], [[(6, 7), (5, 6, 1), (7,), (5, 1, 7)], (5, 6, 7)], [[(5, 6, 1)], (5, 6, 1)], [[(1, 3), (3, 1)], (3, 3)], [[(1, 0), (0, 0)], (0, 0)], [[(0, 1), (0, 0)], (0, 0)], [[(1, 0), (0, 1)], (0, 0)], [[(1, 1), (0, 0)], (0, 0)], [[(1, 1), (1, 0)], (1, 0)], [[(1, 1), (0, 1)], (0, 1)], [[(), (0,)], (0,)], [[(0,), (0, 0)], (0, 0)], [[(0,), (0, 1)], (0, 0)], [[(1,), (0, 0)], (0, 0)], [[(), (0, 0)], (0, 0)], [[(1, 1), (0,)], (1, 0)], [[(1,), (0, 1)], (0, 1)], [[(1,), (1, 0)], (1, 0)], [[(), (1, 0)], (1, 0)], [[(), (0, 1)], (0, 1)], [[(1,), (3,)], (3,)], [[2, (3, 2)], (3, 2)], ] for input_shapes, target_shape in data: assert_equal(broadcast_shapes(*input_shapes), target_shape) assert_equal(broadcast_shapes(*([(1, 2)] * 32)), (1, 2)) assert_equal(broadcast_shapes(*([(1, 2)] * 100)), (1, 2)) # regression tests for gh-5862 assert_equal(broadcast_shapes(*([(2,)] * 32)), (2,)) def test_broadcast_shapes_raises(): # tests public broadcast_shapes data = [ [(3,), (4,)], [(2, 3), (2,)], [(3,), (3,), (4,)], [(1, 3, 4), (2, 3, 3)], [(1, 2), (3,1), (3,2), (10, 5)], [2, (2, 3)], ] for input_shapes in data: assert_raises(ValueError, lambda: broadcast_shapes(*input_shapes)) bad_args = [(2,)] * 32 + [(3,)] * 32 assert_raises(ValueError, lambda: broadcast_shapes(*bad_args)) def test_as_strided(): a = np.array([None]) a_view = as_strided(a) expected = np.array([None]) assert_array_equal(a_view, np.array([None])) a = np.array([1, 2, 3, 4]) a_view = as_strided(a, shape=(2,), strides=(2 * a.itemsize,)) expected = np.array([1, 3]) assert_array_equal(a_view, expected) a = np.array([1, 2, 3, 4]) a_view = as_strided(a, shape=(3, 4), strides=(0, 1 * a.itemsize)) expected = np.array([[1, 2, 3, 4], [1, 2, 3, 4], [1, 2, 3, 4]]) assert_array_equal(a_view, expected) # Regression test for gh-5081 dt = np.dtype([('num', 'i4'), ('obj', 'O')]) a = np.empty((4,), dtype=dt) a['num'] = np.arange(1, 5) a_view = as_strided(a, shape=(3, 4), strides=(0, a.itemsize)) expected_num = [[1, 2, 3, 4]] * 3 expected_obj = [[None]*4]*3 assert_equal(a_view.dtype, dt) assert_array_equal(expected_num, a_view['num']) assert_array_equal(expected_obj, a_view['obj']) # Make sure that void types without fields are kept unchanged a = np.empty((4,), dtype='V4') a_view = as_strided(a, shape=(3, 4), strides=(0, a.itemsize)) assert_equal(a.dtype, a_view.dtype) # Make sure that the only type that could fail is properly handled dt = np.dtype({'names': [''], 'formats': ['V4']}) a = np.empty((4,), dtype=dt) a_view = as_strided(a, shape=(3, 4), strides=(0, a.itemsize)) assert_equal(a.dtype, a_view.dtype) # Custom dtypes should not be lost (gh-9161) r = [rational(i) for i in range(4)] a = np.array(r, dtype=rational) a_view = as_strided(a, shape=(3, 4), strides=(0, a.itemsize)) assert_equal(a.dtype, a_view.dtype) assert_array_equal([r] * 3, a_view) class TestSlidingWindowView: def test_1d(self): arr = np.arange(5) arr_view = sliding_window_view(arr, 2) expected = np.array([[0, 1], [1, 2], [2, 3], [3, 4]]) assert_array_equal(arr_view, expected) def test_2d(self): i, j = np.ogrid[:3, :4] arr = 10*i + j shape = (2, 2) arr_view = sliding_window_view(arr, shape) expected = np.array([[[[0, 1], [10, 11]], [[1, 2], [11, 12]], [[2, 3], [12, 13]]], [[[10, 11], [20, 21]], [[11, 12], [21, 22]], [[12, 13], [22, 23]]]]) assert_array_equal(arr_view, expected) def test_2d_with_axis(self): i, j = np.ogrid[:3, :4] arr = 10*i + j arr_view = sliding_window_view(arr, 3, 0) expected = np.array([[[0, 10, 20], [1, 11, 21], [2, 12, 22], [3, 13, 23]]]) assert_array_equal(arr_view, expected) def test_2d_repeated_axis(self): i, j = np.ogrid[:3, :4] arr = 10*i + j arr_view = sliding_window_view(arr, (2, 3), (1, 1)) expected = np.array([[[[0, 1, 2], [1, 2, 3]]], [[[10, 11, 12], [11, 12, 13]]], [[[20, 21, 22], [21, 22, 23]]]]) assert_array_equal(arr_view, expected) def test_2d_without_axis(self): i, j = np.ogrid[:4, :4] arr = 10*i + j shape = (2, 3) arr_view = sliding_window_view(arr, shape) expected = np.array([[[[0, 1, 2], [10, 11, 12]], [[1, 2, 3], [11, 12, 13]]], [[[10, 11, 12], [20, 21, 22]], [[11, 12, 13], [21, 22, 23]]], [[[20, 21, 22], [30, 31, 32]], [[21, 22, 23], [31, 32, 33]]]]) assert_array_equal(arr_view, expected) def test_errors(self): i, j = np.ogrid[:4, :4] arr = 10*i + j with pytest.raises(ValueError, match='cannot contain negative values'): sliding_window_view(arr, (-1, 3)) with pytest.raises( ValueError, match='must provide window_shape for all dimensions of `x`'): sliding_window_view(arr, (1,)) with pytest.raises( ValueError, match='Must provide matching length window_shape and axis'): sliding_window_view(arr, (1, 3, 4), axis=(0, 1)) with pytest.raises( ValueError, match='window shape cannot be larger than input array'): sliding_window_view(arr, (5, 5)) def test_writeable(self): arr = np.arange(5) view = sliding_window_view(arr, 2, writeable=False) assert_(not view.flags.writeable) with pytest.raises( ValueError, match='assignment destination is read-only'): view[0, 0] = 3 view = sliding_window_view(arr, 2, writeable=True) assert_(view.flags.writeable) view[0, 1] = 3 assert_array_equal(arr, np.array([0, 3, 2, 3, 4])) def test_subok(self): class MyArray(np.ndarray): pass arr = np.arange(5).view(MyArray) assert_(not isinstance(sliding_window_view(arr, 2, subok=False), MyArray)) assert_(isinstance(sliding_window_view(arr, 2, subok=True), MyArray)) # Default behavior assert_(not isinstance(sliding_window_view(arr, 2), MyArray)) def as_strided_writeable(): arr = np.ones(10) view = as_strided(arr, writeable=False) assert_(not view.flags.writeable) # Check that writeable also is fine: view = as_strided(arr, writeable=True) assert_(view.flags.writeable) view[...] = 3 assert_array_equal(arr, np.full_like(arr, 3)) # Test that things do not break down for readonly: arr.flags.writeable = False view = as_strided(arr, writeable=False) view = as_strided(arr, writeable=True) assert_(not view.flags.writeable) class VerySimpleSubClass(np.ndarray): def __new__(cls, *args, **kwargs): return np.array(*args, subok=True, **kwargs).view(cls) class SimpleSubClass(VerySimpleSubClass): def __new__(cls, *args, **kwargs): self = np.array(*args, subok=True, **kwargs).view(cls) self.info = 'simple' return self def __array_finalize__(self, obj): self.info = getattr(obj, 'info', '') + ' finalized' def test_subclasses(): # test that subclass is preserved only if subok=True a = VerySimpleSubClass([1, 2, 3, 4]) assert_(type(a) is VerySimpleSubClass) a_view = as_strided(a, shape=(2,), strides=(2 * a.itemsize,)) assert_(type(a_view) is np.ndarray) a_view = as_strided(a, shape=(2,), strides=(2 * a.itemsize,), subok=True) assert_(type(a_view) is VerySimpleSubClass) # test that if a subclass has __array_finalize__, it is used a = SimpleSubClass([1, 2, 3, 4]) a_view = as_strided(a, shape=(2,), strides=(2 * a.itemsize,), subok=True) assert_(type(a_view) is SimpleSubClass) assert_(a_view.info == 'simple finalized') # similar tests for broadcast_arrays b = np.arange(len(a)).reshape(-1, 1) a_view, b_view = broadcast_arrays(a, b) assert_(type(a_view) is np.ndarray) assert_(type(b_view) is np.ndarray) assert_(a_view.shape == b_view.shape) a_view, b_view = broadcast_arrays(a, b, subok=True) assert_(type(a_view) is SimpleSubClass) assert_(a_view.info == 'simple finalized') assert_(type(b_view) is np.ndarray) assert_(a_view.shape == b_view.shape) # and for broadcast_to shape = (2, 4) a_view = broadcast_to(a, shape) assert_(type(a_view) is np.ndarray) assert_(a_view.shape == shape) a_view = broadcast_to(a, shape, subok=True) assert_(type(a_view) is SimpleSubClass) assert_(a_view.info == 'simple finalized') assert_(a_view.shape == shape) def test_writeable(): # broadcast_to should return a readonly array original = np.array([1, 2, 3]) result = broadcast_to(original, (2, 3)) assert_equal(result.flags.writeable, False) assert_raises(ValueError, result.__setitem__, slice(None), 0) # but the result of broadcast_arrays needs to be writeable, to # preserve backwards compatibility for is_broadcast, results in [(False, broadcast_arrays(original,)), (True, broadcast_arrays(0, original))]: for result in results: # This will change to False in a future version if is_broadcast: with assert_warns(FutureWarning): assert_equal(result.flags.writeable, True) with assert_warns(DeprecationWarning): result[:] = 0 # Warning not emitted, writing to the array resets it assert_equal(result.flags.writeable, True) else: # No warning: assert_equal(result.flags.writeable, True) for results in [broadcast_arrays(original), broadcast_arrays(0, original)]: for result in results: # resets the warn_on_write DeprecationWarning result.flags.writeable = True # check: no warning emitted assert_equal(result.flags.writeable, True) result[:] = 0 # keep readonly input readonly original.flags.writeable = False _, result = broadcast_arrays(0, original) assert_equal(result.flags.writeable, False) # regression test for GH6491 shape = (2,) strides = [0] tricky_array = as_strided(np.array(0), shape, strides) other = np.zeros((1,)) first, second = broadcast_arrays(tricky_array, other) assert_(first.shape == second.shape) def test_writeable_memoryview(): # The result of broadcast_arrays exports as a non-writeable memoryview # because otherwise there is no good way to opt in to the new behaviour # (i.e. you would need to set writeable to False explicitly). # See gh-13929. original = np.array([1, 2, 3]) for is_broadcast, results in [(False, broadcast_arrays(original,)), (True, broadcast_arrays(0, original))]: for result in results: # This will change to False in a future version if is_broadcast: # memoryview(result, writable=True) will give warning but cannot # be tested using the python API. assert memoryview(result).readonly else: assert not memoryview(result).readonly def test_reference_types(): input_array = np.array('a', dtype=object) expected = np.array(['a'] * 3, dtype=object) actual = broadcast_to(input_array, (3,)) assert_array_equal(expected, actual) actual, _ = broadcast_arrays(input_array, np.ones(3)) assert_array_equal(expected, actual)