---
# System prepended metadata

title: '[ICON4Py] Prepare serialization data of mch_icon-ch2_small'
tags: [cycle 30 07/25]

---

# [ICON4Py] Prepare serialization data of mch_icon-ch2_small

<!-- Add the tag for the current cycle number in the top bar -->

- Shaped by: Magdalena
- Appetite (FTEs, weeks):
- Developers: <!-- Filled in at the betting table unless someone is specifically required here -->

## Problem
<!-- The raw idea, a use case, or something we’ve seen that motivates us to work on this -->
Icon4py still uses the "old" dsl experiment mch_ch_r04b09_dsl as a verification base line for the a local area model. We want to switch to using the `mch_icon-ch2_small` which is used in ICON and closer to MCH production.

## Appetite
<!-- Explain how much time we want to spend and how that constrains the solution -->
should not take more than 0.5 week.

## Solution

- serialize reference data for `mch_icon-ch2` in icon.
    - add serialization config to the namelist
    - rename experiment in icon4py and check that all tests run with the new experiment, might need to fix configuration in icon4py.
    - run serialization on 1, 2, 4 nodes
    - replace data on polybox
    - place data on CI TESTDATA folder
- Additionally: repeat the above for the following cases:
    - one that triggers CFL > 0.8 extra diffusion (by taking an experiment and changing the number of substeps and/or changing dt)
    - one that triggers dynamic substep adaption (see above)
    - one that triggers 4th order divdamp (either by setting `divdamp_order == 4` or `(divdamp_order == 24 .AND. divdamp_fac_o2 <= 4._wp*divdamp_fac)`)

- delete everything related to mch_ch_r04b09_dsl in icon4py.

## Rabbit holes
<!-- Details about the solution worth calling out to avoid problems -->
- In order to not duplicate work, we might want to wait for the icon4py CI to be switched from
d126/icontest to the new location.
- It also depends on the [`StencilTests` refactoring task](https://hackmd.io/nkaT0BGFRgevuDMW2t78xw?both#1-StencilTests-with-larger-grids) from the [[ICON4Py] Benchmarking infrastructure](https://hackmd.io/@gridtools/S1dAIqMSxl) project.

## No-gos
<!-- Anything specifically excluded from the concept: functionality or use cases we intentionally aren’t covering to fit the ## appetite or make the problem tractable -->

## Progress
<!-- Don't fill during shaping. This area is for collecting TODOs during building. As first task during building add a preliminary list of coarse-grained tasks for the project and refine them with finer-grained items when it makes sense as you work on them. -->

- [x] Task 1 ([PR#xxxx](https://github.com/GridTools/gt4py/pulls))
    - [x] Subtask A
    - [x] Subtask X
- [ ] Task 2
    - [x] Subtask H
    - [ ] Subtask J
- [ ] Discovered Task 3
    - [ ] Subtask L
    - [ ] Subtask S
- [ ] Task 4

