Python numpy.may_share_memory() Examples

def test_creation_maskcreation(self):
        # Tests how masks are initialized at the creation of Maskedarrays.
        data = arange(24, dtype=float)
        data[[3, 6, 15]] = masked
        dma_1 = MaskedArray(data)
        assert_equal(dma_1.mask, data.mask)
        dma_2 = MaskedArray(dma_1)
        assert_equal(dma_2.mask, dma_1.mask)
        dma_3 = MaskedArray(dma_1, mask=[1, 0, 0, 0] * 6)
        fail_if_equal(dma_3.mask, dma_1.mask)

        x = array([1, 2, 3], mask=True)
        assert_equal(x._mask, [True, True, True])
        x = array([1, 2, 3], mask=False)
        assert_equal(x._mask, [False, False, False])
        y = array([1, 2, 3], mask=x._mask, copy=False)
        assert_(np.may_share_memory(x.mask, y.mask))
        y = array([1, 2, 3], mask=x._mask, copy=True)
        assert_(not np.may_share_memory(x.mask, y.mask)) 

def test_empty(self):
        # Tests empty/like
        datatype = [('a', int), ('b', float), ('c', '|S8')]
        a = masked_array([(1, 1.1, '1.1'), (2, 2.2, '2.2'), (3, 3.3, '3.3')],
                         dtype=datatype)
        assert_equal(len(a.fill_value.item()), len(datatype))

        b = empty_like(a)
        assert_equal(b.shape, a.shape)
        assert_equal(b.fill_value, a.fill_value)

        b = empty(len(a), dtype=datatype)
        assert_equal(b.shape, a.shape)
        assert_equal(b.fill_value, a.fill_value)

        # check empty_like mask handling
        a = masked_array([1, 2, 3], mask=[False, True, False])
        b = empty_like(a)
        assert_(not np.may_share_memory(a.mask, b.mask))
        b = a.view(masked_array)
        assert_(np.may_share_memory(a.mask, b.mask)) 

def check_may_share_memory_exact(a, b):
    got = np.may_share_memory(a, b, max_work=MAY_SHARE_EXACT)

    assert_equal(np.may_share_memory(a, b),
                 np.may_share_memory(a, b, max_work=MAY_SHARE_BOUNDS))

    a.fill(0)
    b.fill(0)
    a.fill(1)
    exact = b.any()

    err_msg = ""
    if got != exact:
        err_msg = "    " + "\n    ".join([
            "base_a - base_b = %r" % (a.__array_interface__['data'][0] - b.__array_interface__['data'][0],),
            "shape_a = %r" % (a.shape,),
            "shape_b = %r" % (b.shape,),
            "strides_a = %r" % (a.strides,),
            "strides_b = %r" % (b.strides,),
            "size_a = %r" % (a.size,),
            "size_b = %r" % (b.size,)
        ])

    assert_equal(got, exact, err_msg=err_msg) 

def test_empty(self):
        # Tests empty/like
        datatype = [('a', int), ('b', float), ('c', '|S8')]
        a = masked_array([(1, 1.1, '1.1'), (2, 2.2, '2.2'), (3, 3.3, '3.3')],
                         dtype=datatype)
        assert_equal(len(a.fill_value.item()), len(datatype))

        b = empty_like(a)
        assert_equal(b.shape, a.shape)
        assert_equal(b.fill_value, a.fill_value)

        b = empty(len(a), dtype=datatype)
        assert_equal(b.shape, a.shape)
        assert_equal(b.fill_value, a.fill_value)

        # check empty_like mask handling
        a = masked_array([1, 2, 3], mask=[False, True, False])
        b = empty_like(a)
        assert_(not np.may_share_memory(a.mask, b.mask))
        b = a.view(masked_array)
        assert_(np.may_share_memory(a.mask, b.mask)) 

def test_creation_maskcreation(self):
        # Tests how masks are initialized at the creation of Maskedarrays.
        data = arange(24, dtype=float)
        data[[3, 6, 15]] = masked
        dma_1 = MaskedArray(data)
        assert_equal(dma_1.mask, data.mask)
        dma_2 = MaskedArray(dma_1)
        assert_equal(dma_2.mask, dma_1.mask)
        dma_3 = MaskedArray(dma_1, mask=[1, 0, 0, 0] * 6)
        fail_if_equal(dma_3.mask, dma_1.mask)

        x = array([1, 2, 3], mask=True)
        assert_equal(x._mask, [True, True, True])
        x = array([1, 2, 3], mask=False)
        assert_equal(x._mask, [False, False, False])
        y = array([1, 2, 3], mask=x._mask, copy=False)
        assert_(np.may_share_memory(x.mask, y.mask))
        y = array([1, 2, 3], mask=x._mask, copy=True)
        assert_(not np.may_share_memory(x.mask, y.mask)) 

def test_empty(self):
        # Tests empty/like
        datatype = [('a', int), ('b', float), ('c', '|S8')]
        a = masked_array([(1, 1.1, '1.1'), (2, 2.2, '2.2'), (3, 3.3, '3.3')],
                         dtype=datatype)
        assert_equal(len(a.fill_value.item()), len(datatype))

        b = empty_like(a)
        assert_equal(b.shape, a.shape)
        assert_equal(b.fill_value, a.fill_value)

        b = empty(len(a), dtype=datatype)
        assert_equal(b.shape, a.shape)
        assert_equal(b.fill_value, a.fill_value)

        # check empty_like mask handling
        a = masked_array([1, 2, 3], mask=[False, True, False])
        b = empty_like(a)
        assert_(not np.may_share_memory(a.mask, b.mask))
        b = a.view(masked_array)
        assert_(np.may_share_memory(a.mask, b.mask)) 

def check_may_share_memory_exact(a, b):
    got = np.may_share_memory(a, b, max_work=MAY_SHARE_EXACT)

    assert_equal(np.may_share_memory(a, b),
                 np.may_share_memory(a, b, max_work=MAY_SHARE_BOUNDS))

    a.fill(0)
    b.fill(0)
    a.fill(1)
    exact = b.any()

    err_msg = ""
    if got != exact:
        err_msg = "    " + "\n    ".join([
            "base_a - base_b = %r" % (a.__array_interface__['data'][0] - b.__array_interface__['data'][0],),
            "shape_a = %r" % (a.shape,),
            "shape_b = %r" % (b.shape,),
            "strides_a = %r" % (a.strides,),
            "strides_b = %r" % (b.strides,),
            "size_a = %r" % (a.size,),
            "size_b = %r" % (b.size,)
        ])

    assert_equal(got, exact, err_msg=err_msg) 

def may_share_memory(a, b):
        # This is Fred suggestion for a quick and dirty way of checking
        # aliasing .. this can potentially be further refined (ticket #374)
        if _is_sparse(a) and _is_sparse(b):
            return (SparseType.may_share_memory(a, b.data) or
                    SparseType.may_share_memory(a, b.indices) or
                    SparseType.may_share_memory(a, b.indptr))
        if _is_sparse(b) and isinstance(a, numpy.ndarray):
            a, b = b, a
        if _is_sparse(a) and isinstance(b, numpy.ndarray):
            if (numpy.may_share_memory(a.data, b) or
                    numpy.may_share_memory(a.indices, b) or
                    numpy.may_share_memory(a.indptr, b)):
                # currently we can't share memory with a.shape as it is a tuple
                return True
        return False 

def test_borrow_input(self):
        """
        Tests that the contract for io.In is respected. When borrow=False, it should be
        impossible for outputs to be aliased to the input variables provided by the user,
        either through a view-map or a destroy map. New tests should be added in the future
        when borrow=True is implemented.
        """
        a = T.dmatrix()
        aval = numpy.random.rand(3, 3)

        # when borrow=False, test that a destroy map cannot alias output to input
        f = theano.function([In(a, borrow=False)], Out(a + 1, borrow=True))
        assert numpy.all(f(aval) == aval + 1)
        assert not numpy.may_share_memory(aval, f(aval))

        # when borrow=False, test that a viewmap cannot alias output to input
        f = theano.function([In(a, borrow=False)], Out(a[0, :], borrow=True))
        assert numpy.all(f(aval) == aval[0, :])
        assert not numpy.may_share_memory(aval, f(aval)) 

def test_no_aliasing_2(self):
        # B and A take one another's values
        # no copying is necessary since each one is updated.
        orig_a = numpy.zeros((2, 2)) + .5
        orig_b = numpy.zeros((2, 2)) - .5
        A = self.shared(orig_a)
        B = self.shared(orig_b)

        data_of_a = data_of(A)
        data_of_b = data_of(B)

        f = pfunc([], [], updates=[(A, B), (B, A)])
        f()
        # correctness
        assert numpy.all(data_of(A) == -.5)
        assert numpy.all(data_of(B) == +.5)

        # shared vars may not be aliased
        assert not numpy.may_share_memory(data_of(A), data_of(B))

        # theano should have been smart enough to not make copies
        assert numpy.may_share_memory(data_of(A), data_of_b)
        assert numpy.may_share_memory(data_of(B), data_of_a) 

def test_creation_maskcreation(self):
        # Tests how masks are initialized at the creation of Maskedarrays.
        data = arange(24, dtype=float)
        data[[3, 6, 15]] = masked
        dma_1 = MaskedArray(data)
        assert_equal(dma_1.mask, data.mask)
        dma_2 = MaskedArray(dma_1)
        assert_equal(dma_2.mask, dma_1.mask)
        dma_3 = MaskedArray(dma_1, mask=[1, 0, 0, 0] * 6)
        fail_if_equal(dma_3.mask, dma_1.mask)

        x = array([1, 2, 3], mask=True)
        assert_equal(x._mask, [True, True, True])
        x = array([1, 2, 3], mask=False)
        assert_equal(x._mask, [False, False, False])
        y = array([1, 2, 3], mask=x._mask, copy=False)
        assert_(np.may_share_memory(x.mask, y.mask))
        y = array([1, 2, 3], mask=x._mask, copy=True)
        assert_(not np.may_share_memory(x.mask, y.mask)) 

def test_empty(self):
        # Tests empty/like
        datatype = [('a', int), ('b', float), ('c', '|S8')]
        a = masked_array([(1, 1.1, '1.1'), (2, 2.2, '2.2'), (3, 3.3, '3.3')],
                         dtype=datatype)
        assert_equal(len(a.fill_value.item()), len(datatype))

        b = empty_like(a)
        assert_equal(b.shape, a.shape)
        assert_equal(b.fill_value, a.fill_value)

        b = empty(len(a), dtype=datatype)
        assert_equal(b.shape, a.shape)
        assert_equal(b.fill_value, a.fill_value)

        # check empty_like mask handling
        a = masked_array([1, 2, 3], mask=[False, True, False])
        b = empty_like(a)
        assert_(not np.may_share_memory(a.mask, b.mask))
        b = a.view(masked_array)
        assert_(np.may_share_memory(a.mask, b.mask)) 

def check_may_share_memory_exact(a, b):
    got = np.may_share_memory(a, b, max_work=MAY_SHARE_EXACT)

    assert_equal(np.may_share_memory(a, b),
                 np.may_share_memory(a, b, max_work=MAY_SHARE_BOUNDS))

    a.fill(0)
    b.fill(0)
    a.fill(1)
    exact = b.any()

    err_msg = ""
    if got != exact:
        err_msg = "    " + "\n    ".join([
            "base_a - base_b = %r" % (a.__array_interface__['data'][0] - b.__array_interface__['data'][0],),
            "shape_a = %r" % (a.shape,),
            "shape_b = %r" % (b.shape,),
            "strides_a = %r" % (a.strides,),
            "strides_b = %r" % (b.strides,),
            "size_a = %r" % (a.size,),
            "size_b = %r" % (b.size,)
        ])

    assert_equal(got, exact, err_msg=err_msg) 

def test_creation_maskcreation(self):
        # Tests how masks are initialized at the creation of Maskedarrays.
        data = arange(24, dtype=float)
        data[[3, 6, 15]] = masked
        dma_1 = MaskedArray(data)
        assert_equal(dma_1.mask, data.mask)
        dma_2 = MaskedArray(dma_1)
        assert_equal(dma_2.mask, dma_1.mask)
        dma_3 = MaskedArray(dma_1, mask=[1, 0, 0, 0] * 6)
        fail_if_equal(dma_3.mask, dma_1.mask)

        x = array([1, 2, 3], mask=True)
        assert_equal(x._mask, [True, True, True])
        x = array([1, 2, 3], mask=False)
        assert_equal(x._mask, [False, False, False])
        y = array([1, 2, 3], mask=x._mask, copy=False)
        assert_(np.may_share_memory(x.mask, y.mask))
        y = array([1, 2, 3], mask=x._mask, copy=True)
        assert_(not np.may_share_memory(x.mask, y.mask)) 

def test_empty(self):
        # Tests empty/like
        datatype = [('a', int), ('b', float), ('c', '|S8')]
        a = masked_array([(1, 1.1, '1.1'), (2, 2.2, '2.2'), (3, 3.3, '3.3')],
                         dtype=datatype)
        assert_equal(len(a.fill_value.item()), len(datatype))

        b = empty_like(a)
        assert_equal(b.shape, a.shape)
        assert_equal(b.fill_value, a.fill_value)

        b = empty(len(a), dtype=datatype)
        assert_equal(b.shape, a.shape)
        assert_equal(b.fill_value, a.fill_value)

        # check empty_like mask handling
        a = masked_array([1, 2, 3], mask=[False, True, False])
        b = empty_like(a)
        assert_(not np.may_share_memory(a.mask, b.mask))
        b = a.view(masked_array)
        assert_(np.may_share_memory(a.mask, b.mask)) 

def check_may_share_memory_exact(a, b):
    got = np.may_share_memory(a, b, max_work=MAY_SHARE_EXACT)

    assert_equal(np.may_share_memory(a, b),
                 np.may_share_memory(a, b, max_work=MAY_SHARE_BOUNDS))

    a.fill(0)
    b.fill(0)
    a.fill(1)
    exact = b.any()

    err_msg = ""
    if got != exact:
        err_msg = "    " + "\n    ".join([
            "base_a - base_b = %r" % (a.__array_interface__['data'][0] - b.__array_interface__['data'][0],),
            "shape_a = %r" % (a.shape,),
            "shape_b = %r" % (b.shape,),
            "strides_a = %r" % (a.strides,),
            "strides_b = %r" % (b.strides,),
            "size_a = %r" % (a.size,),
            "size_b = %r" % (b.size,)
        ])

    assert_equal(got, exact, err_msg=err_msg) 

def test_creation_maskcreation(self):
        # Tests how masks are initialized at the creation of Maskedarrays.
        data = arange(24, dtype=float)
        data[[3, 6, 15]] = masked
        dma_1 = MaskedArray(data)
        assert_equal(dma_1.mask, data.mask)
        dma_2 = MaskedArray(dma_1)
        assert_equal(dma_2.mask, dma_1.mask)
        dma_3 = MaskedArray(dma_1, mask=[1, 0, 0, 0] * 6)
        fail_if_equal(dma_3.mask, dma_1.mask)

        x = array([1, 2, 3], mask=True)
        assert_equal(x._mask, [True, True, True])
        x = array([1, 2, 3], mask=False)
        assert_equal(x._mask, [False, False, False])
        y = array([1, 2, 3], mask=x._mask, copy=False)
        assert_(np.may_share_memory(x.mask, y.mask))
        y = array([1, 2, 3], mask=x._mask, copy=True)
        assert_(not np.may_share_memory(x.mask, y.mask)) 

def test_empty(self):
        # Tests empty/like
        datatype = [('a', int), ('b', float), ('c', '|S8')]
        a = masked_array([(1, 1.1, '1.1'), (2, 2.2, '2.2'), (3, 3.3, '3.3')],
                         dtype=datatype)
        assert_equal(len(a.fill_value.item()), len(datatype))

        b = empty_like(a)
        assert_equal(b.shape, a.shape)
        assert_equal(b.fill_value, a.fill_value)

        b = empty(len(a), dtype=datatype)
        assert_equal(b.shape, a.shape)
        assert_equal(b.fill_value, a.fill_value)

        # check empty_like mask handling
        a = masked_array([1, 2, 3], mask=[False, True, False])
        b = empty_like(a)
        assert_(not np.may_share_memory(a.mask, b.mask))
        b = a.view(masked_array)
        assert_(np.may_share_memory(a.mask, b.mask)) 

def final_view(self, a, axis=None):
        """
        Returns a view of array `a` restricting it to only the
        *final* results computed by this tree (not the intermediate
        results).

        Parameters
        ----------
        a : ndarray
            An array of results computed using this EvalTree,
            such that the `axis`-th dimension equals the full
            length of the tree.  The other dimensions of `a` are
            unrestricted.

        axis : int, optional
            Specified the axis along which the selection of the
            final elements is performed. If None, than this
            selection if performed on flattened `a`.

        Returns
        -------
        ndarray
            Of the same shape as `a`, except for along the
            specified axis, whose dimension has been reduced
            to filter out the intermediate (non-final) results.
        """
        if axis is None:
            return a[0:self.num_final_strings()]
        else:
            sl = [slice(None)] * a.ndim
            sl[axis] = slice(0, self.num_final_strings())
            ret = a[tuple(sl)]
            assert(ret.base is a or ret.base is a.base)  # check that what is returned is a view
            assert(ret.size == 0 or _np.may_share_memory(ret, a))
            return ret 

def test_array_memory_sharing(self):
        assert_(np.may_share_memory(self.a, self.a.ravel()))
        assert_(not np.may_share_memory(self.a, self.a.flatten())) 

def test_matrix_memory_sharing(self):
        assert_(np.may_share_memory(self.m, self.m.ravel()))
        assert_(not np.may_share_memory(self.m, self.m.flatten())) 

def test_basic(self):
        d = np.ones((50, 60))
        d2 = np.ones((30, 60, 6))
        assert_(np.may_share_memory(d, d))
        assert_(np.may_share_memory(d, d[::-1]))
        assert_(np.may_share_memory(d, d[::2]))
        assert_(np.may_share_memory(d, d[1:, ::-1]))

        assert_(not np.may_share_memory(d[::-1], d2))
        assert_(not np.may_share_memory(d[::2], d2))
        assert_(not np.may_share_memory(d[1:, ::-1], d2))
        assert_(np.may_share_memory(d2[1:, ::-1], d2))


# Utility 

def _compare_index_result(self, arr, index, mimic_get, no_copy):
        """Compare mimicked result to indexing result.
        """
        arr = arr.copy()
        indexed_arr = arr[index]
        assert_array_equal(indexed_arr, mimic_get)
        # Check if we got a view, unless its a 0-sized or 0-d array.
        # (then its not a view, and that does not matter)
        if indexed_arr.size != 0 and indexed_arr.ndim != 0:
            assert_(np.may_share_memory(indexed_arr, arr) == no_copy)
            # Check reference count of the original array
            if HAS_REFCOUNT:
                if no_copy:
                    # refcount increases by one:
                    assert_equal(sys.getrefcount(arr), 3)
                else:
                    assert_equal(sys.getrefcount(arr), 2)

        # Test non-broadcast setitem:
        b = arr.copy()
        b[index] = mimic_get + 1000
        if b.size == 0:
            return  # nothing to compare here...
        if no_copy and indexed_arr.ndim != 0:
            # change indexed_arr in-place to manipulate original:
            indexed_arr += 1000
            assert_array_equal(arr, b)
            return
        # Use the fact that the array is originally an arange:
        arr.flat[indexed_arr.ravel()] += 1000
        assert_array_equal(arr, b) 

def check_may_share_memory_easy_fuzz(get_max_work, same_steps, min_count):
    # Check that overlap problems with common strides are solved with
    # little work.
    x = np.zeros([17,34,71,97], dtype=np.int16)

    feasible = 0
    infeasible = 0

    pair_iter = iter_random_view_pairs(x, same_steps)

    while min(feasible, infeasible) < min_count:
        a, b = next(pair_iter)

        bounds_overlap = np.may_share_memory(a, b)
        may_share_answer = np.may_share_memory(a, b)
        easy_answer = np.may_share_memory(a, b, max_work=get_max_work(a, b))
        exact_answer = np.may_share_memory(a, b, max_work=MAY_SHARE_EXACT)

        if easy_answer != exact_answer:
            # assert_equal is slow...
            assert_equal(easy_answer, exact_answer)

        if may_share_answer != bounds_overlap:
            assert_equal(may_share_answer, bounds_overlap)

        if bounds_overlap:
            if exact_answer:
                feasible += 1
            else:
                infeasible += 1 

def test_may_share_memory_bad_max_work():
    x = np.zeros([1])
    assert_raises(OverflowError, np.may_share_memory, x, x, max_work=10**100)
    assert_raises(OverflowError, np.shares_memory, x, x, max_work=10**100) 

def test_fast_power(self):
        x = np.array([1, 2, 3], np.int16)
        res = x**2.0
        assert_((x**2.00001).dtype is res.dtype)
        assert_array_equal(res, [1, 4, 9])
        # check the inplace operation on the casted copy doesn't mess with x
        assert_(not np.may_share_memory(res, x))
        assert_array_equal(x, [1, 2, 3])

        # Check that the fast path ignores 1-element not 0-d arrays
        res = x ** np.array([[[2]]])
        assert_equal(res.shape, (1, 1, 3)) 

def __array_finalize__(self, obj):
        if hasattr(obj, '_mmap') and np.may_share_memory(self, obj):
            self._mmap = obj._mmap
            self.filename = obj.filename
            self.offset = obj.offset
            self.mode = obj.mode
        else:
            self._mmap = None
            self.filename = None
            self.offset = None
            self.mode = None 

def shares_memory(a, b, max_work=None):
    """
    shares_memory(a, b, max_work=None)

    Determine if two arrays share memory

    Parameters
    ----------
    a, b : ndarray
        Input arrays
    max_work : int, optional
        Effort to spend on solving the overlap problem (maximum number
        of candidate solutions to consider). The following special
        values are recognized:

        max_work=MAY_SHARE_EXACT  (default)
            The problem is solved exactly. In this case, the function returns
            True only if there is an element shared between the arrays.
        max_work=MAY_SHARE_BOUNDS
            Only the memory bounds of a and b are checked.

    Raises
    ------
    numpy.TooHardError
        Exceeded max_work.

    Returns
    -------
    out : bool

    See Also
    --------
    may_share_memory

    Examples
    --------
    >>> np.may_share_memory(np.array([1,2]), np.array([5,8,9]))
    False

    """
    return (a, b) 

def may_share_memory(a, b, max_work=None):
    """
    may_share_memory(a, b, max_work=None)

    Determine if two arrays might share memory

    A return of True does not necessarily mean that the two arrays
    share any element.  It just means that they *might*.

    Only the memory bounds of a and b are checked by default.

    Parameters
    ----------
    a, b : ndarray
        Input arrays
    max_work : int, optional
        Effort to spend on solving the overlap problem.  See
        `shares_memory` for details.  Default for ``may_share_memory``
        is to do a bounds check.

    Returns
    -------
    out : bool

    See Also
    --------
    shares_memory

    Examples
    --------
    >>> np.may_share_memory(np.array([1,2]), np.array([5,8,9]))
    False
    >>> x = np.zeros([3, 4])
    >>> np.may_share_memory(x[:,0], x[:,1])
    True

    """
    return (a, b) 

def test_array_interface(self, datetime_index):
        arr = DatetimeArray(datetime_index)

        # default asarray gives the same underlying data (for tz naive)
        result = np.asarray(arr)
        expected = arr._data
        assert result is expected
        tm.assert_numpy_array_equal(result, expected)
        result = np.array(arr, copy=False)
        assert result is expected
        tm.assert_numpy_array_equal(result, expected)

        # specifying M8[ns] gives the same result as default
        result = np.asarray(arr, dtype='datetime64[ns]')
        expected = arr._data
        assert result is expected
        tm.assert_numpy_array_equal(result, expected)
        result = np.array(arr, dtype='datetime64[ns]', copy=False)
        assert result is expected
        tm.assert_numpy_array_equal(result, expected)
        result = np.array(arr, dtype='datetime64[ns]')
        assert result is not expected
        tm.assert_numpy_array_equal(result, expected)

        # to object dtype
        result = np.asarray(arr, dtype=object)
        expected = np.array(list(arr), dtype=object)
        tm.assert_numpy_array_equal(result, expected)

        # to other dtype always copies
        result = np.asarray(arr, dtype='int64')
        assert result is not arr.asi8
        assert not np.may_share_memory(arr, result)
        expected = arr.asi8.copy()
        tm.assert_numpy_array_equal(result, expected)

        # other dtypes handled by numpy
        for dtype in ['float64', str]:
            result = np.asarray(arr, dtype=dtype)
            expected = np.asarray(arr).astype(dtype)
            tm.assert_numpy_array_equal(result, expected)