add optional scipy dependency for numpy sparse

Author: majosm

.github/workflows/ci.yml

@@ -38,7 +38,7 @@ jobs:
         -   uses: actions/checkout@v6
         -   name: "Main Script"
             run: |
-                EXTRA_INSTALL="pytest types-colorama types-Pygments"
+                EXTRA_INSTALL="pytest types-colorama types-Pygments scipy-stubs"
                 curl -L -O https://tiker.net/ci-support-v0
                 . ./ci-support-v0
 

arraycontext/impl/numpy/__init__.py

@@ -214,18 +214,14 @@ def sparse_matmul(
             assert isinstance(x1.elem_col_indices, np.ndarray)
             assert isinstance(x1.row_starts, np.ndarray)
 
-            # FIXME: Not sure if the scipy dependency is OK or if it should just use
-            # the call_loopy fallback? Currently getting errors with the loopy version:
-            #     loopy.diagnostic.LoopyError: One of the kernels in the program has
-            #         been preprocessed, cannot modify target now.
             from scipy.sparse import csr_matrix
             np_matrix = csr_matrix(
                 (x1.elem_values, x1.elem_col_indices, x1.row_starts),
                 shape=x1.shape)
 
             def _matmul(ary: ArrayOrScalar) -> ArrayOrScalar:
                 assert isinstance(ary, np.ndarray)
-                return np_matrix @ ary
+                return cast("ArrayOrScalar", cast("object", np_matrix @ ary))
 
             return cast("ArrayOrContainer", rec_map_container(_matmul, x2))
 

pyproject.toml

@@ -46,6 +46,9 @@ pyopencl = [
 pytato = [
     "pytato>=2021.1",
 ]
+sparse = [
+    "scipy",
+]
 test = [
     "basedpyright",
     "pytest",