data: Rename engine selector Scalar to IndexScalar

The selection-layer Scalar collided with devito.types.Scalar, forcing an
alias wherever both are imported (e.g. test_data.py). Rename it to
IndexScalar at the source so the name is unambiguous everywhere and no
aliasing is needed.

Author: mloubout

devito/data/distributed/plan.py

@@ -22,7 +22,7 @@
 
 import numpy as np
 
-from devito.data.distributed.selection import Affine, Scalar
+from devito.data.distributed.selection import Affine, IndexScalar
 from devito.data.distributed.transport import nbx_exchange
 from devito.mpi import MPI
 from devito.tools import prod
@@ -288,7 +288,7 @@ def _distributed_coords(selection, layout, t_dims, t_shape):
     gcoords = {}
     for axis in layout.distributed_axes:
         s = selection.selectors[axis]
-        if isinstance(s, Scalar):
+        if isinstance(s, IndexScalar):
             gcoords[axis] = np.full(nrows, s.index, dtype=np.int64)
         elif isinstance(s, Affine):
             ri = t_dims.index(('basic', axis))
@@ -368,7 +368,7 @@ def _replicated_block(selection, layout, p_dims, payload_shape):
 
     for axis in layout.replicated_axes:
         s = selection.selectors[axis]
-        if isinstance(s, Scalar):
+        if isinstance(s, IndexScalar):
             coord = np.full(payload_size, s.index, dtype=np.int64)
         elif isinstance(s, Affine):
             ri = p_dims.index(('basic', axis))

devito/data/distributed/selection.py

@@ -15,7 +15,7 @@
 
 from devito.tools import is_integer
 
-__all__ = ['Affine', 'Explicit', 'Scalar', 'Selection', 'index_has_array',
+__all__ = ['Affine', 'Explicit', 'IndexScalar', 'Selection', 'index_has_array',
            'result_dims']
 
 
@@ -33,7 +33,7 @@ def index_has_array(idx, ndim):
 
 
 @dataclass(frozen=True)
-class Scalar:
+class IndexScalar:
     """A single global index on one axis. The axis is dropped from the result."""
 
     index: int
@@ -153,7 +153,7 @@ class Selection:
     Attributes
     ----------
     selectors : tuple
-        One ``Scalar``, ``Affine``, or ``Explicit`` per axis.
+        One ``IndexScalar``, ``Affine``, or ``Explicit`` per axis.
     advanced_axes : tuple of int
         The axes indexed by arrays (the single coupled advanced group). Their
         ``Explicit`` coords share one flattened point ordering.
@@ -204,7 +204,7 @@ def from_index(cls, idx, shape):
                 if not 0 <= index < n:
                     raise IndexError(f"index {item} is out of bounds for axis "
                                      f"{axis} with size {n}")
-                selectors[axis] = Scalar(index)
+                selectors[axis] = IndexScalar(index)
             elif isinstance(item, slice):
                 selectors[axis] = Affine(*item.indices(n))
             elif _is_advanced(item):
@@ -285,7 +285,7 @@ def result_dims(selectors, advanced_axes, advanced_shape, advanced_at_front):
         dims += [('adv', j) for j in range(len(advanced_shape))]
     inserted = False
     for axis, s in enumerate(selectors):
-        if isinstance(s, Scalar):
+        if isinstance(s, IndexScalar):
             continue
         elif isinstance(s, Explicit):
             if advanced_at_front:

tests/test_data.py

@@ -9,9 +9,9 @@
 from devito.data import LEFT, RIGHT, Decomposition, convert_index, loc_data_idx
 from devito.data.allocators import DataReference
 from devito.data.distributed.layout import Layout
-from devito.data.distributed.selection import Affine, Explicit
-from devito.data.distributed.selection import Scalar as IndexScalar
-from devito.data.distributed.selection import Selection, index_has_array, result_dims
+from devito.data.distributed.selection import (
+    Affine, Explicit, IndexScalar, Selection, index_has_array, result_dims
+)
 from devito.ir import ccode
 from devito.tools import as_tuple
 from devito.types import Scalar