Add test config for iterhybrid predictor-corrector with small fixed timestep.

Used for benchmarks. Not run as part of sim tests.

PiperOrigin-RevId: 951425379

Author: jcitrin

torax/tests/test_data/test_iterhybrid_predictor_corrector_fixed_small_dt.py

@@ -0,0 +1,22 @@
+# Copyright 2026 DeepMind Technologies Limited
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Identical to iterhybrid_predictor_corrector but with small fixed timestep."""
+import copy
+
+from torax.examples import iterhybrid_predictor_corrector
+
+CONFIG = copy.deepcopy(iterhybrid_predictor_corrector.CONFIG)
+CONFIG['numerics']['fixed_dt'] = 1e-3
+CONFIG['time_step_calculator'] = {'calculator_type': 'fixed'}