DRAFT: Minimal Grid Reader

test/test_mpas.py

@@ -140,3 +140,9 @@ def test_face_area(self):
 
         assert "face_areas" in uxgrid_primal._ds
         assert "face_areas" in uxgrid_dual._ds
+
+    def test_minimal(self):
+        """Tests the minimal grid reader"""
+        uxgrid = ux.open_grid(self.mpas_grid_path, minimal=True)
+
+        assert "node_x" not in uxgrid._ds

uxarray/core/api.py

@@ -19,6 +19,7 @@ def open_grid(
     ],
     latlon: Optional[bool] = False,
     use_dual: Optional[bool] = False,
+    minimal: Optional[bool] = False,
     **kwargs: Dict[str, Any],
 ) -> Grid:
     """Constructs and returns a ``Grid`` from a grid file.
@@ -34,11 +35,13 @@ def open_grid(
         object to define the grid.
 
     latlon : bool, optional
-            Specify if the grid is lat/lon based
+        Specify if the grid is lat/lon based
 
     use_dual: bool, optional
         Specify whether to use the primal (use_dual=False) or dual (use_dual=True) mesh if the file type is mpas
 
+    minimal: bool, optional
+        Specify whether to read the minimal information (`nodes` and `face_node_connectivity`) needed for a grid
     **kwargs : Dict[str, Any]
         Additional arguments passed on to ``xarray.open_dataset``. Refer to the
         [xarray
@@ -84,7 +87,7 @@ def open_grid(
         try:
             grid_ds = xr.open_dataset(grid_filename_or_obj, **kwargs)
 
-            uxgrid = Grid.from_dataset(grid_ds, use_dual=use_dual)
+            uxgrid = Grid.from_dataset(grid_ds, use_dual=use_dual, minimal=minimal)
         except ValueError:
             raise ValueError("Inputted grid_filename_or_obj not supported.")
 

uxarray/grid/grid.py

@@ -241,7 +241,11 @@ def __init__(
 
     @classmethod
     def from_dataset(
-        cls, dataset: xr.Dataset, use_dual: Optional[bool] = False, **kwargs
+        cls,
+        dataset: xr.Dataset,
+        use_dual: Optional[bool] = False,
+        minimal: Optional[bool] = False,
+        **kwargs,
     ):
         """Constructs a ``Grid`` object from an ``xarray.Dataset``.
 
@@ -251,6 +255,8 @@ def from_dataset(
             ``xarray.Dataset`` containing unstructured grid coordinates and connectivity variables
         use_dual : bool, default=False
             When reading in MPAS formatted datasets, indicates whether to use the Dual Mesh
+        minimal : bool, default=False
+             Specify whether to read the minimal information (`nodes` and `face_node_connectivity`) needed for a grid
         """
         if not isinstance(dataset, xr.Dataset):
             raise ValueError("Input must be an xarray.Dataset")
@@ -264,17 +270,21 @@ def from_dataset(
             if source_grid_spec == "Exodus":
                 grid_ds, source_dims_dict = _read_exodus(dataset)
             elif source_grid_spec == "Scrip":
-                grid_ds, source_dims_dict = _read_scrip(dataset)
+                grid_ds, source_dims_dict = _read_scrip(dataset, minimal)
             elif source_grid_spec == "UGRID":
-                grid_ds, source_dims_dict = _read_ugrid(dataset)
+                grid_ds, source_dims_dict = _read_ugrid(dataset, minimal=minimal)
             elif source_grid_spec == "MPAS":
-                grid_ds, source_dims_dict = _read_mpas(dataset, use_dual=use_dual)
+                grid_ds, source_dims_dict = _read_mpas(
+                    dataset, use_dual=use_dual, minimal=minimal
+                )
             elif source_grid_spec == "ESMF":
-                grid_ds, source_dims_dict = _read_esmf(dataset)
+                grid_ds, source_dims_dict = _read_esmf(dataset, minimal=minimal)
             elif source_grid_spec == "GEOS-CS":
-                grid_ds, source_dims_dict = _read_geos_cs(dataset)
+                grid_ds, source_dims_dict = _read_geos_cs(dataset, minimal=minimal)
             elif source_grid_spec == "ICON":
-                grid_ds, source_dims_dict = _read_icon(dataset, use_dual=use_dual)
+                grid_ds, source_dims_dict = _read_icon(
+                    dataset, use_dual=use_dual, minimal=minimal
+                )
             elif source_grid_spec == "Structured":
                 grid_ds = _read_structured_grid(dataset[lon_name], dataset[lat_name])
                 source_dims_dict = {"n_face": (lon_name, lat_name)}

uxarray/io/_esmf.py

@@ -6,7 +6,7 @@
 from uxarray.conventions import ugrid
 
 
-def _read_esmf(in_ds):
+def _read_esmf(in_ds, minimal=False):
     """Reads in an Xarray dataset containing an ESMF formatted Grid dataset and
     encodes it in the UGRID conventions.
 
@@ -27,6 +27,8 @@ def _read_esmf(in_ds):
     ----------
     in_ds: xr.Dataset
         ESMF Grid Dataset
+    minimal : bool, optional
+        Specify whether to read the minimal information (`nodes` and `face_node_connectivity`) needed for a grid
 
     Returns
     -------
@@ -56,7 +58,7 @@ def _read_esmf(in_ds):
             node_lat, dims=[ugrid.NODE_DIM], attrs=ugrid.NODE_LAT_ATTRS
         )
 
-        if "centerCoords" in in_ds:
+        if "centerCoords" in in_ds and not minimal:
             # parse center coords (face centers) if available
             face_lon = in_ds["centerCoords"].isel(coordDim=0).values
             out_ds[ugrid.FACE_COORDINATES[0]] = xr.DataArray(

uxarray/io/_geos.py

@@ -5,8 +5,19 @@
 from uxarray.conventions import ugrid
 
 
-def _read_geos_cs(in_ds: xr.Dataset):
+def _read_geos_cs(in_ds: xr.Dataset, minimal=False):
     """Reads and encodes a GEOS Cube-Sphere grid into the UGRID conventions.
+    Parameters
+    ----------
+    in_ds: xr.Dataset
+        GEOS_CS Grid Dataset
+    minimal : bool, optional
+        Specify whether to read the minimal information (`nodes` and `face_node_connectivity`) needed for a grid
+
+    Returns
+    -------
+    out_ds: xr.Dataset
+        GEOS_CS Grid encoder in the UGRID conventions
 
     https://gmao.gsfc.nasa.gov/gmaoftp/ops/GEOSIT_sample/doc/CS_Description_c180_v1.pdf
     """
@@ -23,7 +34,7 @@ def _read_geos_cs(in_ds: xr.Dataset):
         data=node_lat, dims=ugrid.NODE_DIM, attrs=ugrid.NODE_LAT_ATTRS
     )
 
-    if "lons" in in_ds:
+    if "lons" in in_ds and not minimal:
         face_lon = in_ds["lons"].values.ravel()
         face_lat = in_ds["lats"].values.ravel()
 

uxarray/io/_icon.py

@@ -3,8 +3,20 @@
 import numpy as np
 
 
-def _primal_to_ugrid(in_ds, out_ds):
-    """Encodes the Primal Mesh of an ICON Grid into the UGRID conventions."""
+def _primal_to_ugrid(in_ds, out_ds, minimal=False):
+    """Encodes the Primal Mesh of an ICON Grid into the UGRID conventions.
+    Parameters
+    ----------
+    in_ds: xr.Dataset
+        ICON Grid Dataset
+    minimal : bool, optional
+        Specify whether to read the minimal information (`nodes` and `face_node_connectivity`) needed for a grid
+
+    Returns
+    -------
+    out_ds: xr.Dataset
+        ICON Grid encoder in the UGRID conventions
+    """
     source_dims_dict = {"vertex": "n_node", "edge": "n_edge", "cell": "n_face"}
 
     # rename dimensions to match ugrid conventions
@@ -21,28 +33,6 @@ def _primal_to_ugrid(in_ds, out_ds):
         data=node_lat, dims=ugrid.NODE_DIM, attrs=ugrid.NODE_LAT_ATTRS
     )
 
-    # edge coordinates
-    edge_lon = np.rad2deg(in_ds["elon"])
-    edge_lat = np.rad2deg(in_ds["elat"])
-
-    out_ds["edge_lon"] = xr.DataArray(
-        data=edge_lon, dims=ugrid.EDGE_DIM, attrs=ugrid.EDGE_LON_ATTRS
-    )
-    out_ds["edge_lat"] = xr.DataArray(
-        data=edge_lat, dims=ugrid.EDGE_DIM, attrs=ugrid.EDGE_LAT_ATTRS
-    )
-
-    # face coordinates
-    face_lon = np.rad2deg(in_ds["clon"])
-    face_lat = np.rad2deg(in_ds["clat"])
-
-    out_ds["face_lon"] = xr.DataArray(
-        data=face_lon, dims=ugrid.FACE_DIM, attrs=ugrid.FACE_LON_ATTRS
-    )
-    out_ds["face_lat"] = xr.DataArray(
-        data=face_lat, dims=ugrid.FACE_DIM, attrs=ugrid.FACE_LAT_ATTRS
-    )
-
     face_node_connectivity = in_ds["vertex_of_cell"].T - 1
 
     out_ds["face_node_connectivity"] = xr.DataArray(
@@ -51,45 +41,68 @@ def _primal_to_ugrid(in_ds, out_ds):
         attrs=ugrid.FACE_NODE_CONNECTIVITY_ATTRS,
     )
 
-    face_edge_connectivity = in_ds["edge_of_cell"].T - 1
-
-    out_ds["face_edge_connectivity"] = xr.DataArray(
-        data=face_edge_connectivity,
-        dims=ugrid.FACE_EDGE_CONNECTIVITY_DIMS,
-        attrs=ugrid.FACE_EDGE_CONNECTIVITY_ATTRS,
-    )
-
-    face_face_connectivity = in_ds["neighbor_cell_index"].T - 1
-
-    out_ds["face_face_connectivity"] = xr.DataArray(
-        data=face_face_connectivity,
-        dims=ugrid.FACE_FACE_CONNECTIVITY_DIMS,
-        attrs=ugrid.FACE_FACE_CONNECTIVITY_ATTRS,
-    )
-
-    edge_face_connectivity = in_ds["adjacent_cell_of_edge"].T - 1
-
-    out_ds["edge_face_connectivity"] = xr.DataArray(
-        data=edge_face_connectivity,
-        dims=ugrid.EDGE_FACE_CONNECTIVITY_DIMS,
-        attrs=ugrid.EDGE_FACE_CONNECTIVITY_ATTRS,
-    )
-
-    edge_node_connectivity = in_ds["edge_vertices"].T - 1
-    out_ds["edge_node_connectivity"] = xr.DataArray(
-        data=edge_node_connectivity,
-        dims=ugrid.EDGE_NODE_CONNECTIVITY_DIMS,
-        attrs=ugrid.EDGE_NODE_CONNECTIVITY_ATTRS,
-    )
+    if not minimal:
+        # edge coordinates
+        edge_lon = np.rad2deg(in_ds["elon"])
+        edge_lat = np.rad2deg(in_ds["elat"])
+
+        out_ds["edge_lon"] = xr.DataArray(
+            data=edge_lon, dims=ugrid.EDGE_DIM, attrs=ugrid.EDGE_LON_ATTRS
+        )
+        out_ds["edge_lat"] = xr.DataArray(
+            data=edge_lat, dims=ugrid.EDGE_DIM, attrs=ugrid.EDGE_LAT_ATTRS
+        )
+
+        # face coordinates
+        face_lon = np.rad2deg(in_ds["clon"])
+        face_lat = np.rad2deg(in_ds["clat"])
+
+        out_ds["face_lon"] = xr.DataArray(
+            data=face_lon, dims=ugrid.FACE_DIM, attrs=ugrid.FACE_LON_ATTRS
+        )
+        out_ds["face_lat"] = xr.DataArray(
+            data=face_lat, dims=ugrid.FACE_DIM, attrs=ugrid.FACE_LAT_ATTRS
+        )
+
+        face_edge_connectivity = in_ds["edge_of_cell"].T - 1
+
+        out_ds["face_edge_connectivity"] = xr.DataArray(
+            data=face_edge_connectivity,
+            dims=ugrid.FACE_EDGE_CONNECTIVITY_DIMS,
+            attrs=ugrid.FACE_EDGE_CONNECTIVITY_ATTRS,
+        )
+
+        face_face_connectivity = in_ds["neighbor_cell_index"].T - 1
+
+        out_ds["face_face_connectivity"] = xr.DataArray(
+            data=face_face_connectivity,
+            dims=ugrid.FACE_FACE_CONNECTIVITY_DIMS,
+            attrs=ugrid.FACE_FACE_CONNECTIVITY_ATTRS,
+        )
+
+        edge_face_connectivity = in_ds["adjacent_cell_of_edge"].T - 1
+
+        out_ds["edge_face_connectivity"] = xr.DataArray(
+            data=edge_face_connectivity,
+            dims=ugrid.EDGE_FACE_CONNECTIVITY_DIMS,
+            attrs=ugrid.EDGE_FACE_CONNECTIVITY_ATTRS,
+        )
+
+        edge_node_connectivity = in_ds["edge_vertices"].T - 1
+        out_ds["edge_node_connectivity"] = xr.DataArray(
+            data=edge_node_connectivity,
+            dims=ugrid.EDGE_NODE_CONNECTIVITY_DIMS,
+            attrs=ugrid.EDGE_NODE_CONNECTIVITY_ATTRS,
+        )
 
     return out_ds, source_dims_dict
 
 
-def _read_icon(ext_ds, use_dual=False):
+def _read_icon(ext_ds, use_dual=False, minimal=False):
     """Reads and encodes an ICON mesh into the UGRID conventions."""
     out_ds = xr.Dataset()
 
     if not use_dual:
-        return _primal_to_ugrid(ext_ds, out_ds)
+        return _primal_to_ugrid(ext_ds, out_ds, minimal)
     else:
         raise ValueError("Conversion of the ICON Dual mesh is not yet supported.")