Use faster lookup

lib/iris/_concatenate.py

 return False 
 if get_hashes(coord_a.coord) != get_hashes(coord_b.coord): 
 return False 
@@ -5,17 +5,18 @@
 """Automatic concatenation of multiple cubes over one or more existing dimensions."""
 
 from collections import namedtuple
+from collections.abc import Sequence
 import itertools
-from typing import Iterable
+from typing import Any, Iterable
 import warnings
 
 import dask
 import dask.array as da
+from dask.base import tokenize
 import numpy as np
-from xxhash import xxh3_64
+from xxhash import xxh3_64_digest
 
 from iris._lazy_data import concatenate as concatenate_arrays
-from iris._lazy_data import is_masked_data
 import iris.coords
 import iris.cube
 import iris.exceptions
@@ -308,11 +309,7 @@ def _hash_array(a: da.Array | np.ndarray) -> np.int64:
  """
 
  def arrayhash(x):
- value = xxh3_64(np.array(x.shape, dtype=np.uint).tobytes())
- value.update(x.data.tobytes())
- if is_masked_data(x):
- value.update(x.mask.tobytes())
- return np.frombuffer(value.digest(), dtype=np.int64)
+ return np.frombuffer(xxh3_64_digest(x.tobytes()), dtype=np.int64)
 
  return da.reduction(
  a,
@@ -325,20 +322,41 @@ def arrayhash(x):
  )
 
 
-class _ArrayHash:
- def __init__(self, value: np.int64, chunks: tuple) -> None:
- self.value = value
- self.chunks = chunks
+class _ArrayHash(namedtuple("ArrayHash", ["value", "chunks"])):
+ """Container for a hash value and the chunks used when computing it.
 
- def __eq__(self, other: "_ArrayHash") -> bool:
+ Parameters
+ ----------
+ value : :class:`np.int64`
+ The hash value.
+ chunks : tuple
+ The chunks the array had when the hash was computed.
+ """
+
+ __slots__ = ()
+
+ def __eq__(self, other: Any) -> bool:
+ if not isinstance(other, self.__class__):
+ return NotImplemented
  if self.chunks != other.chunks:
- raise ValueError("Unable to compare arrays with different chunks.")
+ raise ValueError(
+ "Unable to compare arrays with different chunks: "
+ f"{self.chunks} != {other.chunks}"
+ )
  return self.value == other.value
 
 
+def array_id(array: np.ndarray | da.Array) -> str:
+ """Get a deterministic token representing `array`."""
+ if isinstance(array, np.ma.MaskedArray):
+ # Tokenizing a masked array is much slower than separately tokenizing
+ # the data and mask.
+ return tokenize((tokenize(array.data), tokenize(array.mask)))
+ return tokenize(array)
+
+
 def _compute_hashes(arrays: Iterable[np.ndarray | da.Array]) -> dict[str, _ArrayHash]:
  """Compute hashes for the arrays that will be compared."""
- hashes = {}
 
  def is_numerical(dtype):
  return np.issubdtype(dtype, np.bool_) or np.issubdtype(dtype, np.number)
@@ -350,9 +368,11 @@ def group_key(a):
  dtype = str(a.dtype)
  return a.shape, dtype
 
+ hashes = {}
+
  arrays = sorted(arrays, key=group_key)
- for _, group in itertools.groupby(arrays, key=group_key):
- group = list(group)
+ for _, group_iter in itertools.groupby(arrays, key=group_key):
+ group = list(group_iter)
  # Unify dtype for numerical arrays, as the hash depends on it
  if is_numerical(group[0].dtype):
  dtype = np.result_type(*group)
@@ -364,23 +384,23 @@ def group_key(a):
  argpairs = [(a, indices) for a in same_dtype_arrays]
  rechunked_arrays = da.core.unify_chunks(*itertools.chain(*argpairs))[1]
  for array, rechunked in zip(group, rechunked_arrays):
- hashes[dask.base.tokenize(array)] = (
+ hashes[array_id(array)] = (
  _hash_array(rechunked),
  rechunked.chunks,
  )
 
- result = dask.compute(hashes)[0]
- return {k: _ArrayHash(*v) for k, v in result.items()}
+ hashes = dask.compute(hashes)[0]
+ return {k: _ArrayHash(*v) for k, v in hashes.items()}
 
 
 def concatenate(
- cubes,
- error_on_mismatch=False,
- check_aux_coords=True,
- check_cell_measures=True,
- check_ancils=True,
- check_derived_coords=True,
-):
+ cubes: Sequence[iris.cube.Cube],
+ error_on_mismatch: bool = False,
+ check_aux_coords: bool = True,
+ check_cell_measures: bool = True,
+ check_ancils: bool = True,
+ check_derived_coords: bool = True,
+) -> iris.cube.CubeList:
  """Concatenate the provided cubes over common existing dimensions.
 
  Parameters
@@ -418,7 +438,7 @@ def concatenate(
  A :class:`iris.cube.CubeList` of concatenated :class:`iris.cube.Cube` instances.
 
  """
- proto_cubes = []
+ proto_cubes: list[_ProtoCube] = []
  # Initialise the nominated axis (dimension) of concatenation
  # which requires to be negotiated.
  axis = None
@@ -718,7 +738,7 @@ def match(self, other, error_on_mismatch):
 class _CoordSignature:
  """Template for identifying a specific type of :class:`iris.cube.Cube` based on its coordinates."""
 
- def __init__(self, cube_signature):
+ def __init__(self, cube_signature: _CubeSignature) -> None:
  """Represent the coordinate metadata.
 
  Represent the coordinate metadata required to identify suitable
@@ -737,7 +757,7 @@ def __init__(self, cube_signature):
  self.derived_coords_and_dims = cube_signature.derived_coords_and_dims
  self.dim_coords = cube_signature.dim_coords
  self.dim_mapping = cube_signature.dim_mapping
- self.dim_extents = []
+ self.dim_extents: list[_CoordExtent] = []
  self.dim_order = [
  metadata.kwargs["order"] for metadata in cube_signature.dim_metadata
  ]
@@ -746,7 +766,10 @@ def __init__(self, cube_signature):
  self._calculate_extents()
 
  @staticmethod
- def _cmp(coord, other):
+ def _cmp(
+ coord: iris.coords.DimCoord,
+ other: iris.coords.DimCoord,
+ ) -> tuple[bool, bool]:
  """Compare the coordinates for concatenation compatibility.
 
  Returns
@@ -757,22 +780,17 @@ def _cmp(coord, other):
 
  """
  # A candidate axis must have non-identical coordinate points.
- candidate_axis = not array_equal(coord.core_points(), other.core_points())
+ candidate_axis = not array_equal(coord.points, other.points)
 
- if candidate_axis:
- # Ensure both have equal availability of bounds.
- result = (coord.core_bounds() is None) == (other.core_bounds() is None)
- else:
- if coord.core_bounds() is not None and other.core_bounds() is not None:
- # Ensure equality of bounds.
- result = array_equal(coord.core_bounds(), other.core_bounds())
- else:
- # Ensure both have equal availability of bounds.
- result = coord.core_bounds() is None and other.core_bounds() is None
+ # Ensure both have equal availability of bounds.
+ result = coord.has_bounds() == other.has_bounds()
+ if result and not candidate_axis:
+ # Ensure equality of bounds.
+ result = array_equal(coord.bounds, other.bounds)
 
  return result, candidate_axis
 
- def candidate_axis(self, other):
+ def candidate_axis(self, other: "_CoordSignature") -> int | None:
  """Determine the candidate axis of concatenation with the given coordinate signature.
 
  If a candidate axis is found, then the coordinate
@@ -804,13 +822,13 @@ def candidate_axis(self, other):
  # Only permit one degree of dimensional freedom when
  # determining the candidate axis of concatenation.
  if result and len(candidate_axes) == 1:
- result = candidate_axes[0]
+ axis = candidate_axes[0]
  else:
- result = None
+ axis = None
 
- return result
+ return axis
 
- def _calculate_extents(self):
+ def _calculate_extents(self) -> None:
  """Calculate the extent over each dimension coordinates points and bounds."""
  self.dim_extents = []
  for coord, order in zip(self.dim_coords, self.dim_order):
@@ -950,15 +968,15 @@ def concatenate(self):
 
  def register(
  self,
- cube,
- hashes,
- axis=None,
- error_on_mismatch=False,
- check_aux_coords=False,
- check_cell_measures=False,
- check_ancils=False,
- check_derived_coords=False,
- ):
+ cube: iris.cube.Cube,
+ hashes: dict[str, _ArrayHash],
+ axis: int | None = None,
+ error_on_mismatch: bool = False,
+ check_aux_coords: bool = False,
+ check_cell_measures: bool = False,
+ check_ancils: bool = False,
+ check_derived_coords: bool = False,
+ ) -> bool:
  """Determine if the given source-cube is suitable for concatenation.
 
  Determine if the given source-cube is suitable for concatenation
@@ -1032,7 +1050,7 @@ def register(
  warnings.warn(msg, category=iris.warnings.IrisUserWarning)
 
  def get_hash(array):
- return hashes[dask.base.tokenize(array)]
+ return hashes[array_id(array)]
 
  def get_hashes(coord):
  result = []

lib/iris/tests/unit/concatenate/test_hashing.py

@@ -5,7 +5,6 @@
 """Test array hashing in :mod:`iris._concatenate`."""
 
 import dask.array as da
-from dask.base import tokenize
 import numpy as np
 import pytest
 
@@ -30,7 +29,7 @@
 )
 def test_compute_hashes(a, b, eq):
  hashes = _concatenate._compute_hashes([a, b])
- assert eq == (hashes[tokenize(a)] == hashes[tokenize(b)])
+ assert eq == (hashes[_concatenate.array_id(a)] == hashes[_concatenate.array_id(b)])
 
 
 def test_arrayhash_incompatible_chunks_raises():