### Navigation

- ☰
- PyTecplot-0.9 »
- Module code »

# Source code for tecplot.data.nodemap

    import itertools as it
    import logging

    from  contextlib import contextmanager
    from ctypes import addressof, cast, c_int32, c_int64, c_void_p, POINTER
    from textwrap import dedent

    from ..tecutil import _tecutil, _tecutil_connector
    from ..constant import *
    from ..exception import *
    from .. import session
    from ..tecutil import array_to_str, lock, lock_attributes, filled_slice

    log = logging.getLogger(__name__)

    class Elementmap(c_void_p):
        """Nodemap reverse look-up."""
        def __init__(self, zone):
            self.zone = zone
            super().__init__(self._native_reference())

        @lock()
        def _native_reference(self):
            with self.zone.dataset.frame.activated():
                return _tecutil.DataNodeToElemMapGetReadableRef(self.zone.index + 1)

        def num_elements(self, node):
            return _tecutil.DataNodeToElemMapGetNumElems(self, node + 1)

        def element(self, node, offset):
            return _tecutil.DataNodeToElemMapGetElem(self, node + 1, offset + 1) - 1

    @lock_attributes
    class Nodemap(c_void_p):
        r"""Connectivity list definition and control for classic FE zones.

        A nodemap holds the connectivity between nodes and elements for classic
        finite-element zones. It is nominally a two-dimensionaly array of shape
        :math:`(N_e, N_{npe})` where :math:`N_e` is the number of elements and
        :math:`N_{npe}` is the number of nodes per element. The nodemap interface
        has flat-array access through the `Nodemap.array` property as well as
        reverse look-up with `Nodemap.num_elements()` and `Nodemap.element()`.

        The nodemap behaves mostly like a two-dimensional array and can be treated
        as such::

            >>> nodemap = dataset.zone('My Zone').nodemap
            >>> print('nodes in the first element:', nodemap[0])
            nodes in the first element: [0, 1, 2, 3]
            >>> print(nodemap[:3])
            [[0, 1, 2, 3], [2, 3, 4, 5], [4, 5, 6, 7]]
            >>> nodemap[0] = [6, 7, 8, 9]
            >>> print(nodemap[0])
            [6, 7, 8, 9]

        Just for clarity, the nodemap indexing is by element first, then offset
        within that element::

            >>> element = 6
            >>> offset = 2
            >>> node = nodemap[element][offset]
            >>> print(node)
            21

        Setting node indices must be done for an entire element because getting
        values out of the nodemap and into Python always creates a copy. For
        example, **this will not work**::

            >>> nodemap = dataset.zone('My Zone').nodemap
            >>> # Trying to set the 3rd node of the element 10
            >>> nodemap[10][2] = 5  # Error: nodemap[10] returns a copy

        To modify a single node in a nodemap, it is neccessary to do a round trip
        like so::

            nodemap = dataset.zone('My Zone').nodemap
            >>> nodes = nodemap[10]
            >>> nodes[2] = 5
            >>> nodemap[10] = nodes  # OK: setting whole element at a time
            >>> print(nodemap[10])
            [20, 21, 5, 22]

        The following script creates a quad of two triangles from scratch using the
        PyTecplot low-level data creation interface. The general steps are:

        1. Setup the data
        2. Create the tecplot dataset and variables
        3. Create the zone
        4. Set the node locations and connectivity lists
        5. Set the (scalar) data
        6. Write out data file
        7. Adjust plot style and export image

        The data created looks like this:

        .. code-block:: none

            Node positions (x,y,z):

                           (1,1,1)
                          3
                         / \
                        /   \
             (0,1,.5)  2-----1  (1,0,.5)
                        \   /
                         \ /
                          0
                           (0,0,0)

        Breaking up the two triangular elements, the faces look like this. Notice the
        first element (index: 0) is on the bottom:

        .. code-block:: none

            Element 1 Faces:
                               *
               (nodes 3-2)  1 / \ 0  (nodes 1-3)
                             /   \
                            *-----*
                               2
                                (nodes 2-1)

            Element 0 Faces:
                                (nodes 1-2)
                               1
                            *-----*
                             \   /
               (nodes 2-0)  2 \ / 0  (nodes 0-1)
                               *

        The nodes are created as a list of :math:`(x, y, z)` positions::

            [(x0, y0, z0), (x1, y1, z1)...]

        which are transposed to lists of :math:`x`, :math:`y` and :math:`z`-positions::

            [(x0, x1, x2...), (y0, y1, y2...)...]

        and passed to the :math:`(x, y, z)` arrays. The nodemap, or connectivity list,
        is given as an array of dimensions :math:`(N, D)` where :math:`N` is the number
        of elements and :math:`D` is the number of nodes per element. The order of the
        node locations determines the indices used when specifying the connectivity
        list. The Nodemap can be set individually and separately or all at once as
        shown here.

        .. code-block:: python

            import tecplot as tp
            from tecplot.constant import *

            # (x, y, z) locations of nodes
            nodes = (
                (0, 0, 0  ), # node 0
                (1, 0, 0.5), # node 1
                (0, 1, 0.5), # ...
                (1, 1, 1  ),
                )

            scalar_data = [0, 1, 2, 3]

            # Connectivity list
            # (n0, n1, n2) node indexes which make up the triangles
            conn = (
                (0, 1, 2), # element 0 consisting of faces
                           #     node connections: 0-1, 1-2, 2-0
                (1, 3, 2), # element 1
                )

            # Setup dataset and zone
            ds = tp.active_frame().create_dataset('Data', ['x','y','z','s'])
            z = ds.add_fe_zone(ZoneType.FETriangle,
                               name='FE Triangle Float (4,2) Nodal',
                               num_points=len(nodes), num_elements=len(conn))

            # Fill in node locations
            z.values('x')[:] = [n[0] for n in nodes]
            z.values('y')[:] = [n[1] for n in nodes]
            z.values('z')[:] = [n[2] for n in nodes]

            # Set the nodemap
            z.nodemap[:] = conn

            # Set the scalar data
            z.values('s')[:] = scalar_data

            ### Now we setup a nice view of the data
            plot = tp.active_frame().plot(PlotType.Cartesian3D)
            plot.activate()

            plot.contour(0).colormap_name = 'Sequential - Yellow/Green/Blue'
            plot.contour(0).colormap_filter.distribution = ColorMapDistribution.Continuous

            for ax in plot.axes:
                ax.show = True

            plot.show_mesh = False
            plot.show_contour = True
            plot.show_edge = True
            plot.use_translucency = True

            fmap = plot.fieldmap(z)
            fmap.surfaces.surfaces_to_plot = SurfacesToPlot.All
            fmap.effects.surface_translucency = 40

            # View parameters obtained interactively from Tecplot 360
            plot.view.distance = 10
            plot.view.width = 2
            plot.view.psi = 80
            plot.view.theta = 30
            plot.view.alpha = 0
            plot.view.position = (-4.2, -8.0, 2.3)

            # Showing mesh, we can see all the individual triangles
            plot.show_mesh = True
            plot.fieldmap(z).mesh.line_pattern = LinePattern.Dashed

            tp.export.save_png('fe_triangles1.png', 600, supersample=3)

        ..  figure:: /_static/images/fe_triangles1.png
            :width: 300px
            :figwidth: 300px
        """
        def __init__(self, zone):
            self.zone = zone
            super().__init__(self._native_reference())

        @lock()
        def _native_reference(self, writable=False):
            _dispatch = {
                True: _tecutil.DataNodeGetWritableRef,
                False: _tecutil.DataNodeGetReadableRef}
            with self.zone.dataset.frame.activated():
                return _dispatch[writable](self.zone.index + 1)

        @lock()
        def _raw_pointer(self, writable=False):
            if _tecutil_connector.connected:
                msg = 'raw pointer access only available in batch-mode'
                raise TecplotLogicError(msg)
            _dispatch = {
                True: {
                    c_int32: _tecutil.DataNodeGetWritableRawPtrByRef,
                    c_int64: _tecutil.DataNodeGetWritableRawPtrByRef64},
                False: {
                    c_int32: _tecutil.DataNodeGetReadableRawPtrByRef,
                    c_int64: _tecutil.DataNodeGetReadableRawPtrByRef64}
                }
            return _dispatch[writable][self.c_type](self)

        def _raw_array(self, writable=False):
            ptr = self._raw_pointer(writable)
            return cast(ptr, POINTER(self.c_type * self.size)).contents

        @property
        def array(self):
            r"""Flattened array accessor for this nodemap.

            :type: 1D view of the nodemap.

            The nodemap is normally dimensioned by :math:`(N_e, N_{npe})` where
            :math:`N_e` is the number of elements and :math:`N_{npe}` is the number
            of nodes per element. This property represents a flattened view into
            the array which is of length :math:`N_e \times N_{npe}`. This may be
            more convenient than flattening the array in your script using a
            looping construct.

            Standard Python list slicing works for both fetching values and assignments. Example usage::

                >>> nmap = dataset.zone('My Zone').nodemap
                >>> nmap.array[:] = mydata
                >>> print(nmap.array[:10])
                [1, 10, 8, 0, 5, 18, 6, 12, 18, 11]
            """
            return NodemapArray(self.zone)

        @lock()
        def alloc(self):
            """Allocates the internal space needed to store the Nodemap.

            This method is used in conjunction with deferred nodemap creation and
            is not needed with load-on-demand or normal zone creation methods.
            """
            with self.zone.dataset.frame.activated():
                if not _tecutil.DataNodeAlloc(self.zone.index + 1):
                    raise TecplotSystemError()

        def __eq__(self, other):
            self_addr = addressof(cast(self, POINTER(c_int64)).contents)
            other_addr = addressof(cast(other, POINTER(c_int64)).contents)
            return self_addr == other_addr

        def __ne__(self, other):
            return not (self == other)

        def __len__(self):
            return self.zone.num_elements

        def __iter__(self):
            self._current_index = -1
            self._current_length = len(self)
            return self

        def __next__(self):
            self._current_index = self._current_index + 1
            if self._current_index < self._current_length:
                return self.__getitem__(self._current_index)
            else:
                del self._current_index
                del self._current_length
                raise StopIteration

        def next(self):  # if sys.version_info < (3,)
            return self.__next__()

        @contextmanager
        def assignment(self):
            """Context manager for assigning to the nodemap.

            When setting values to the nodemap, a state change is emitted to the
            engine after every statement. This can degrade performance if in the
            script the nodemap is being set many times. This context provides a way
            to suspend the state change notification until all assignments have
            been completed. In the following example, the state change is emitted
            only after the ``nodemap.assignment()`` context exits::

                >>> nodemap = dataset.zone('My Zone').nodemap
                >>> with nodemap.assignment():
                ...     for elem, nodes in enumerate(mydata):
                ...         nodemap[elem] = nodes
            """
            opts = dict(what=StateChange.NodeMapsAltered, zones=self.zone,
                        dataset=self.zone.dataset)
            with session.state_change(self, **opts):
                yield

        @property
        def shape(self):
            r"""Shape of the nodemap array.

            :type: `tuple` of `integers <int>`

            .. note:: This property is read-only.

            This is defined by the zone type and is equal to :math:`(N_e, N_{npe})`
            where :math:`N_e` is the number of elements and :math:`N_{npe}` is the
            number of nodes per element. Example usage::

                >>> print(dataset.zone(0).nodemap.shape)
                (1024, 4)
            """
            return (self.zone.num_elements, self.num_points_per_element)

        @property
        def size(self):
            r"""Total number of nodes stored in the nodemap array.

            :type: `integer <int>`

            .. note:: This property is read-only.

            This is defined by the zone type and is equal to :math:`N_e \times
            N_{npe}` where :math:`N_e` is the number of elements and
            :math:`N_{npe}` is the number of nodes per element. Example usage::

                >>> print(dataset.zone(0).nodemap.shape)
                (1024, 4)
                >>> print(dataset.zone(0).nodemap.size)
                4096
            """
            return self.zone.num_elements * self.num_points_per_element

        @property
        def c_type(self):
            """The underlying data type for this nodemap.

            :type: One of: `ctypes.c_int32`, `ctypes.c_int64`

            .. note:: This property is read-only.

            This is the `ctypes` integer type used by the Tecplot Engine to store
            the nodemap data. This is used internally and is not normally needed
            for simple nodemap access.
            """
            _ctypes = {
                OffsetDataType.OffsetDataType_32Bit: c_int32,
                OffsetDataType.OffsetDataType_64Bit: c_int64}
            data_type = _tecutil.DataNodeGetRawItemType(self)
            return _ctypes[data_type]

        @property
        def num_points_per_element(self):
            r"""Points per element for classic finite-element zones.

            :type: `integer <int>`

            .. note:: This property is read-only.

            The number of points (also known as nodes) per finite-element is
            determined from the ``zone_type`` parameter. The following table shows
            the number of points per element for the available zone types along
            with the resulting shape of the nodemap based on the number of points
            specified (:math:`N`):

                ============== ============== ================
                Zone Type      Points/Element Nodemap Shape
                ============== ============== ================
                ``FELineSeg``  2              :math:`(N, 2 N)`
                ``FETriangle`` 3              :math:`(N, 3 N)`
                ``FEQuad``     4              :math:`(N, 4 N)`
                ``FETetra``    4              :math:`(N, 4 N)`
                ``FEBrick``    8              :math:`(N, 8 N)`
                ============== ============== ================

            Example usage::

                >>> zone = dataset.zone('My Zone')
                >>> print(zone.zone_type)
                ZoneType.FETriangle
                >>> print(zone.nodemap.num_points_per_element)
                3
            """
            return _tecutil.DataNodeGetNodesPerElem(self)

        def __getitem__(self, i):
            """Access the nodemap by elements.

            Parameters:
                i (`integer <int>` or `slice`): Element(s) to fetch from the
                    nodemap.
            """
            ppe = self.num_points_per_element
            if isinstance(i, slice):
                s = filled_slice(i, len(self))
                nelems = s.stop - s.start
                start = (s.start * ppe)
                stop = (s.stop * ppe)
                arr = self.array[start:stop]
                elems = list(range(nelems))[::s.step]
                return [arr[e * ppe:(e  + 1) * ppe] for e in elems]
            else:
                return self.array[i * ppe:(i + 1) * ppe]

        def __setitem__(self, i, nodes):
            """Modify the nodemap by elements.

            Parameters:
                i (`integer <int>` or `slice`): Element(s) to modify in the
                    nodemap.
            """
            ppe = self.num_points_per_element
            if isinstance(i, slice):
                s = filled_slice(i, len(self))
                if s.step == 1:
                    a = s.start * ppe
                    b = s.stop * ppe
                    self.array[a:b] = [i for sublist in nodes for i in sublist]
                else:
                    with self.assignment():
                        for i, n in zip(range(s.start, s.stop, s.step), nodes):
                            self[i] = n
            else:
                self.array[i * ppe:(i + 1) * ppe] = nodes

        def num_elements(self, node):
            """The number of elements that use a given node.

            Parameters:
                node: (`integer <int>`): Zero-based index of a node.

            Returns:
                `integer <int>` - The number of elements that use this node.

            Example usage::

                >>> nodemap = dataset.zone('My Zone').nodemap
                >>> nodemap.num_elements(3)
                8
            """
            return Elementmap(self.zone).num_elements(node)

        def element(self, node, offset):
            """The element containing a given node.

            Parameters:
                node (`integer <int>`): Zero-based index of a node.
                offset (`integer <int>`): Zero-based index of the element that uses
                    the given node.

            Returns:
                `integer <int>` - Zero-based index of the element.

            Example usage::

                >>> nodemap = dataset.zone('My Zone').nodemap
                >>> print(nodemap.element(3, 7))
                324
            """
            return Elementmap(self.zone).element(node, offset)

    class NodemapArray(Nodemap):
        def __len__(self):
            return self.size

        @property
        def shape(self):
            return (len(self),)

        @lock()
        def __getitem__(self, i):
            """Access the underlying nodemap as 1D array."""
            if isinstance(i, slice):
                s = filled_slice(i, len(self))
                n = s.stop - s.start
                arr = (self.c_type * n)()
                _tecutil.DataNodeArrayGetByRef(self, s.start + 1, n, arr)
                for i in range(len(arr)):
                    arr[i] -= 1
                return arr[::s.step]
            else:
                elem, node = divmod(i, self.num_points_per_element)
                return _tecutil.DataNodeGetByRef(self, elem + 1, node + 1) - 1

        @lock()
        def __setitem__(self, i, nodes):
            """Modify the underlying nodemap as 1D array."""
            _dispatch = {
                c_int32: _tecutil.DataNodeArraySetByRef,
                c_int64: _tecutil.DataNodeArraySetByRef64}
            data_ctype = self.c_type
            ref = self._native_reference(writable=True)
            with self.assignment():
                if isinstance(i, slice):
                    s = filled_slice(i, len(self))
                    if s.step == 1:
                        n = s.stop - s.start
                        arr = (data_ctype * n)(*[nd + 1 for nd in nodes])

                        if __debug__:
                            if min(arr) < 1 or self.zone.num_points < max(arr):
                                raise TecplotIndexError
                            log.debug(dedent('''\
                                Nodemap Assignment:
                                    offset: {}
                                    array({}): {}''').format(s.start + 1, n,
                                                             array_to_str(arr)))
                        _dispatch[data_ctype](ref, s.start + 1, n, arr)
                    else:
                        ppe = self.num_points_per_element
                        for i, n in zip(range(s.start, s.stop, s.step), nodes):
                            elem, node = divmod(i, ppe)
                            _tecutil.DataNodeSetByRef(ref, elem + 1, node + 1,
                                                      n + 1)
                else:
                    ppe = self.num_points_per_element
                    elem, node = divmod(i, ppe)
                    _tecutil.DataNodeSetByRef(ref, elem + 1, node + 1, nodes + 1)

### Navigation

- index
- modules |