NOAA-GFDL · FlorianDeconinck · Nov 27, 2025 · Oct 29, 2025 · Oct 29, 2025 · Oct 30, 2025
diff --git a/.github/PULL_REQUEST_TEMPLATE/README.md b/.github/PULL_REQUEST_TEMPLATE/README.md
@@ -0,0 +1,9 @@
+# Pull request templates
+
+- `../pull_request_template.md`: The default pull request template. Used for PRs.
+- `release.md`: Special template used for releasing a new version of NDSL.
+- `release-patch.md`: Special template used for patch releases.
+
+Note: GitHub has limited support for multiple pull request templates. Most notably, templates can only be [selected by an URL query parameter](https://github.com/orgs/community/discussions/4620) and there's currently [no way to set a title](https://github.com/orgs/community/discussions/63965).
+
+Note: GitHub does not support having the default pull request template in this folder. All templates in this folder can only be used with the `template=` URL parameter (see note above).
diff --git a/.github/PULL_REQUEST_TEMPLATE/release-patch.md b/.github/PULL_REQUEST_TEMPLATE/release-patch.md
@@ -0,0 +1,32 @@
+# Release NDSL version `YYYY.MM.PP`
+
+This PR patches release `YYYY.MM.PP` because
+
+1. reason
+2. reason
+3. ...
+
+## Pre-release checklist
+
+Things to do before the patch release. Helps to keep the fallout from this release as minimal as possible.
+
+- [ ] setup a draft PR in [NOAA-GFDL/pace](https://github.com/NOAA-GFDL/pace) with updated submodules for `NDSL`, `pyFV3`, and `pySHiELD`.
+  Don't merge yet - just let CI run and fix potential issues before the release. To be merged afterwards, see post-release checklist.
+
+## Release checklist
+
+What to do to actually release:
+
+- [x] create this PR to merge changes from `my-patches` into `main`
+  - use "squash merge"
+- [ ] once merged, create a GitHub release and tag the new version
+  - version format is `[year].[month].[patch]`. Increase the patch version, e.g. `2025.10.01` if this is patching the `2025.10.00` release.
+  - let GitHub auto-generate release notes from the last tagged version
+- [ ] send an announcement on Mattermost
+
+## Post-release checklist
+
+What to do after a release:
+
+- [ ] update the pace PR from the pre-commit checklist to include the released version of NDSL and merge it.
+- [ ] in NDSL, merge `main` back into `develop` (potentially adding a commit to fix the issue "properly")
diff --git a/.github/PULL_REQUEST_TEMPLATE/release.md b/.github/PULL_REQUEST_TEMPLATE/release.md
@@ -0,0 +1,26 @@
+# Release NDSL version `YYYY.MM.00`
+
+## Pre-release checklist
+
+Things to do before the release. Helps to keep the fallout from this release as minimal as possible.
+
+- [ ] setup a draft PR in [NOAA-GFDL/pace](https://github.com/NOAA-GFDL/pace) with updated submodules for `NDSL`, `pyFV3`, and `pySHiELD`.
+  Don't merge yet - just let CI run and fix potential issues before the release. To be merged afterwards, see post-release checklist.
+
+## Release checklist
+
+What to do to actually release:
+
+- [x] create this PR to merge changes from `develop` into `main`
+  - merge as "Merge commit"
+- [ ] once merged, create a GitHub release and tag the new version
+  - version format is `[year].[month].[patch]`, e.g. `2025.10.00`
+  - let GitHub auto-generate release notes from the last tagged version
+- [ ] send an announcement on Mattermost
+
+## Post-release checklist
+
+What to do after a release:
+
+- [ ] update the pace PR from the pre-commit checklist to include the released version of NDSL and merge it.
+- [ ] merge breaking changes in NDSL (e.g. search for deprecation warnings)
diff --git a/.github/PULL_REQUEST_TEMPLATE.md → .github/pull_request_template.md b/.github/PULL_REQUEST_TEMPLATE.md → .github/pull_request_template.md
diff --git a/.github/workflows/create-cache.yaml b/.github/workflows/create-cache.yaml
@@ -14,7 +14,7 @@ on:
 
 # Cancel running jobs if there's a newer push
 concurrency:
-  group: ${{ github.repository }}-${{ github.workflow }}-${{ github.ref }}
+  group: ndsl-${{ github.workflow }}-${{ github.ref }}
   cancel-in-progress: true
 
 jobs:
@@ -45,8 +45,8 @@ jobs:
 
   # GitHub Actions cache of pyFV3 test data
   pyFV3_test_data:
-    uses: NOAA-GFDL/pyFV3/.github/workflows/create_cache.yml@develop
+    uses: NOAA-GFDL/pyFV3/.github/workflows/create_cache.yaml@develop
 
   # GitHub Actions cache of pySHiELD test data
   pySHiELD_test_data:
-    uses: NOAA-GFDL/pySHiELD/.github/workflows/create_cache.yml@develop
+    uses: NOAA-GFDL/pySHiELD/.github/workflows/create_cache.yaml@develop
diff --git a/.github/workflows/docs_build.yaml b/.github/workflows/docs_build.yaml
@@ -28,7 +28,7 @@ jobs:
           python-version: '3.11'
 
       - name: Install mkdocs
-        run: pip install mkdocs-material mkdocstrings[python]
+        run: pip install mkdocs-material mkdocstrings[python] mkdocs-exclude
 
       - name: Build docs
         run: mkdocs build
diff --git a/.github/workflows/docs_deploy.yaml b/.github/workflows/docs_deploy.yaml
@@ -29,7 +29,7 @@ jobs:
           python-version: 3.11
 
       - name: Install dependencies
-        run: pip install mkdocs-material mkdocstrings[python]
+        run: pip install mkdocs-material mkdocstrings[python] mkdocs-exclude
 
       - name: Deploy docs to GitHub Pages
         run: mkdocs gh-deploy --force
diff --git a/.github/workflows/unit_tests.yaml b/.github/workflows/unit_tests.yaml
@@ -32,7 +32,7 @@ jobs:
         run: pip3 install mpich
 
       - name: Install Python packages
-        run: pip3 install .[test]
+        run: pip3 install .[test,zarr]
 
       - name: Run serial-cpu tests
         run: coverage run --rcfile=pyproject.toml -m pytest tests

diff --git a/docs/docstrings/testing/dummy_comm.md b/docs/docstrings/testing/dummy_comm.md
diff --git a/docs/docstrings/top/exceptions.md b/docs/docstrings/top/exceptions.md
diff --git a/docs/docstrings/top/filesystem.md b/docs/docstrings/top/filesystem.md
diff --git a/docs/docstrings/top/namelist.md b/docs/docstrings/top/namelist.md
diff --git a/docs/docstrings/top/units.md b/docs/docstrings/top/units.md
diff --git a/docs/internal/README.md b/docs/internal/README.md
@@ -0,0 +1,3 @@
+# Internal documentation
+
+This folder contains internal / developer documentation and processes, e.g. how to build a release. This folder is thus ignored when building the public facing documentation from the `docs/` folder.
diff --git a/docs/internal/release.md b/docs/internal/release.md
@@ -0,0 +1,24 @@
+# Release a new version
+
+This internal documentation guides you through the process of releasing a new version of NDSL. It is very simple:
+
+1. Click [create a release](https://github.com/NOAA-GFDL/NDSL/compare/main...develop?expand=1&template=release.md) and follow the steps in the release checklist.
+
+## Patch release
+
+Every now and then, we'll need to patch the currently released version of NDSL. To do so, follow these steps:
+
+1. Create a branch from `main`.
+2. Commit your changes on that branch.
+3. Use the following URL <https://github.com/NOAA-GFDL/NDSL/compare/main...[your-branch-name]?expand=1&template=release-patch.md> and follow the steps in the patch release checklist.
+
+As an example, you'd go and create branch `my-patches` from `main`
+
+```bash
+git checkout main
+git switch -c my-patches
+# do changes ...
+git push
+```
+
+and in that case, the URL with the patch release template is: <https://github.com/NOAA-GFDL/NDSL/compare/main...my-patches?expand=1&template=release-patch.md>.
diff --git a/docs/user/index.md b/docs/user/index.md
@@ -12,13 +12,13 @@ NDSL tries to have sensible defaults. In cases you want tweak something, here ar
 
 ### Literal precision (float/int)
 
-Unspecified integer and floating point literals (e.g. `42` and `3.1415`) default to 64-bit precision. This can be changed with the environment variable `PACE_FLOAT_PRECISION`.
+Unspecified integer and floating point literals (e.g. `42` and `3.1415`) default to 64-bit precision. This can be changed with the environment variable `NDSL_LITERAL_PRECISION`.
 
 For mixed precision code, you can specify the "hard coded" precision with type hints and casts, e.g.
 
 ```python
 with computation(PARALLEL), interval(...):
-    # Either 32-bit or 64-bit depending on `PACE_FLOAT_PRECISION`
+    # Either 32-bit or 64-bit depending on `NDSL_LITERAL_PRECISION`
     my_int = 42
     my_float = 3.1415
 

diff --git a/external/dace b/external/dace
diff --git a/external/gt4py b/external/gt4py
diff --git a/mkdocs.yml b/mkdocs.yml
@@ -24,15 +24,12 @@ nav:
           - "boilerplate": docstrings/top/boilerplate.md
           - "buffer": docstrings/top/buffer.md
           - "constants": docstrings/top/constants.md
-          - "exceptions": docstrings/top/exceptions.md
-          - "filesystem": docstrings/top/filesystem.md
           - "io": docstrings/top/io.md
           - "logging": docstrings/top/logging.md
           - "namelist": docstrings/top/namelist.md
           - "optional_imports": docstrings/top/optional_imports.md
           - "types": docstrings/top/types.md
           - "typing": docstrings/top/typing.md
-          - "units": docstrings/top/units.md
           - "utils": docstrings/top/utils.md
       - checkpointer:
           - "base": docstrings/checkpointer/base.md
@@ -106,7 +103,6 @@ nav:
           - "tridiag": docstrings/stencils/tridiag.md
       - testing:
           - "comparison": docstrings/testing/comparison.md
-          - "dummy_comm": docstrings/testing/dummy_comm.md
           - "perturbation": docstrings/testing/perturbation.md
       - viz:
           - "cube_sphere": docstrings/viz/cube_sphere.md
@@ -149,6 +145,9 @@ plugins:
           paths: [./ndsl]  # Adjust this path to where your Python modules are
           options:
             show_source: false
+  - exclude:
+      glob:
+        - internal/*
 
 watch:
   # reload when the glossary file is updated

diff --git a/ndsl/__init__.py b/ndsl/__init__.py
@@ -19,18 +19,15 @@
 from .dsl.ndsl_runtime import NDSLRuntime
 from .dsl.stencil import FrozenStencil, GridIndexing, StencilFactory, TimingCollector
 from .dsl.stencil_config import CompilationConfig, RunMode, StencilConfig
-from .exceptions import OutOfBoundsError
 from .halo.data_transformer import HaloExchangeSpec
 from .halo.updater import HaloUpdater, HaloUpdateRequest, VectorInterfaceHaloUpdater
 from .initialization import GridSizer, QuantityFactory, SubtileGridSizer
 from .monitor.netcdf_monitor import NetCDFMonitor
-from .namelist import Namelist
 from .performance.collector import NullPerformanceCollector, PerformanceCollector
 from .performance.profiler import NullProfiler, Profiler
 from .performance.report import Experiment, Report, TimeReport
 from .quantity import Local, Quantity, State
 from .quantity.field_bundle import FieldBundle, FieldBundleType  # Break circular import
-from .testing.dummy_comm import DummyComm
 from .types import Allocator
 from .utils import MetaEnumStr
 
@@ -62,7 +59,6 @@
     "CompilationConfig",
     "RunMode",
     "StencilConfig",
-    "OutOfBoundsError",
     "HaloExchangeSpec",
     "HaloUpdater",
     "HaloUpdateRequest",
@@ -72,7 +68,6 @@
     "SubtileGridSizer",
     "ndsl_log",
     "NetCDFMonitor",
-    "Namelist",
     "NullPerformanceCollector",
     "PerformanceCollector",
     "NullProfiler",
@@ -83,7 +78,6 @@
     "Quantity",
     "FieldBundle",
     "FieldBundleType",
-    "DummyComm",
     "Allocator",
     "MetaEnumStr",
     "State",

diff --git a/ndsl/boilerplate.py b/ndsl/boilerplate.py
@@ -3,7 +3,7 @@
     DaceConfig,
     DaCeOrchestration,
     GridIndexing,
-    NullComm,
+    MPIComm,
     QuantityFactory,
     RunMode,
     StencilConfig,
@@ -54,6 +54,13 @@ def _get_factories(
     )
 
     if topology == "tile":
+        mpi_comm = MPIComm()
+        if mpi_comm.Get_size() != 1:
+            raise ValueError(
+                "Single tile topology requested with an MPI communicator of size "
+                f"{mpi_comm.Get_size()} > 1. Re-configure MPI to run on only one rank."
+            )
+
         partitioner = TilePartitioner((1, 1))
         sizer = SubtileGridSizer.from_tile_params(
             nx_tile=nx,
@@ -63,13 +70,13 @@ def _get_factories(
             layout=partitioner.layout,
             tile_partitioner=partitioner,
         )
-        comm = TileCommunicator(comm=NullComm(0, 1, 42), partitioner=partitioner)
+        comm = TileCommunicator(comm=mpi_comm, partitioner=partitioner)
     else:
         raise NotImplementedError(f"Topology {topology} is not implemented.")
 
     grid_indexing = GridIndexing.from_sizer_and_communicator(sizer, comm)
     stencil_factory = StencilFactory(config=stencil_config, grid_indexing=grid_indexing)
-    quantity_factory = QuantityFactory.from_backend(sizer, backend)
+    quantity_factory = QuantityFactory(sizer, backend=backend)
 
     return stencil_factory, quantity_factory
 

diff --git a/ndsl/comm/__init__.py b/ndsl/comm/__init__.py
@@ -5,7 +5,7 @@
     CachingRequestReader,
     CachingRequestWriter,
 )
-from .comm_abc import Comm, Request
+from .comm_abc import Comm, ReductionOperator, Request
 
 
 __all__ = [
@@ -15,5 +15,6 @@
     "CachingRequestReader",
     "CachingRequestWriter",
     "Comm",
+    "ReductionOperator",
     "Request",
 ]
diff --git a/ndsl/comm/communicator.py b/ndsl/comm/communicator.py
@@ -108,7 +108,7 @@ def _create_all_reduce_quantity(
             units=input_metadata.units,
             origin=input_metadata.origin,
             extent=input_metadata.extent,
-            gt4py_backend=input_metadata.gt4py_backend,
+            backend=input_metadata.backend,
             allow_mismatch_float_precision=False,
         )
         return all_reduce_quantity
@@ -228,7 +228,7 @@ def _get_gather_recv_quantity(
             units=send_metadata.units,
             origin=tuple([0 for dim in send_metadata.dims]),
             extent=global_extent,
-            gt4py_backend=send_metadata.gt4py_backend,
+            backend=send_metadata.backend,
             allow_mismatch_float_precision=True,
         )
         return recv_quantity
@@ -241,7 +241,7 @@ def _get_scatter_recv_quantity(
             send_metadata.np.zeros(shape, dtype=send_metadata.dtype),  # type: ignore
             dims=send_metadata.dims,
             units=send_metadata.units,
-            gt4py_backend=send_metadata.gt4py_backend,
+            backend=send_metadata.backend,
             allow_mismatch_float_precision=True,
         )
         return recv_quantity
@@ -326,6 +326,7 @@ def gather_state(self, send_state=None, recv_state=None, transfer_type=None):  #
                     dims=quantity.dims,
                     units=quantity.units,
                     allow_mismatch_float_precision=True,
+                    backend=quantity.backend,
                 )
                 if recv_state is not None and name in recv_state:
                     tile_quantity = self.gather(
@@ -841,7 +842,7 @@ def _get_gather_recv_quantity(
             units=metadata.units,
             origin=(0,) + tuple([0 for dim in metadata.dims]),
             extent=global_extent,
-            gt4py_backend=metadata.gt4py_backend,
+            backend=metadata.backend,
             allow_mismatch_float_precision=True,
         )
         return recv_quantity
@@ -861,7 +862,7 @@ def _get_scatter_recv_quantity(
             metadata.np.zeros(shape, dtype=metadata.dtype),  # type: ignore
             dims=metadata.dims[1:],
             units=metadata.units,
-            gt4py_backend=metadata.gt4py_backend,
+            backend=metadata.backend,
             allow_mismatch_float_precision=True,
         )
         return recv_quantity
diff --git a/ndsl/comm/null_comm.py b/ndsl/comm/null_comm.py
@@ -1,4 +1,5 @@
 import copy
+import warnings
 from collections.abc import Mapping
 from typing import Any, TypeVar, cast
 
@@ -33,6 +34,12 @@ def __init__(self, rank: int, total_ranks: int, fill_value: T = default_fill_val
             fill_value: fill halos with this value when performing
                 halo updates.
         """
+        warnings.warn(
+            "NullComm is deprecated and will be removed with the next version of NDSL. "
+            "Use MPIComm or LocalComm instead.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
         self.rank = rank
         self.total_ranks = total_ranks
         self._fill_value = fill_value
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,3 @@
		# Internal documentation

		This folder contains internal / developer documentation and processes, e.g. how to build a release. This folder is thus ignored when building the public facing documentation from the `docs/` folder.
+5 −0		dace/data.py
+12 −6		dace/frontend/python/newast.py
+8 −0		dace/symbolic.py
+1 −1		setup.py
+2 −1		tests/codegen/allocation_lifetime_test.py
+18 −0		tests/python_frontend/loops_test.py
+114 −25		tests/python_frontend/structures/structure_python_test.py