---
# System prepended metadata

title: FV3 Features into Main Branch
tags: [cycle 7, gtc]

---

# FV3 Features into Main Branch

###### tags: `cycle 7` `gtc`
shaped by: Johann

## Problem

Despite work on the project, we still do not have the core features necessary for the dynamical core into the main branch of gt4py.

There are multiple reasons for this, among them having to support so many backends (which will become easier with the removal of the legacy toolchain), both AI2 and CSCS having other development priorities - such as new features for physics ports.

The focus here should be on enabling just the features necessary for the dynamical core.

## Appetite

1 developer. Johann and Hannes will coordinate.

## Solution

### Continue reviewing [while loop PR](https://github.com/GridTools/gt4py/pull/422) and merge

This is quite close. We need to merge the concept documentation, and continue reviewing the code together.

### Revise [horizontal regions PR](https://github.com/GridTools/gt4py/pull/486), review, and merge

This is a larger undertaking. First, it has fallen out of date with the master branch, so there are likely bugs that need to be fixed.

There were a number of internal new features that had to be added to make this work, which have to get reviewed and merged
- Axis offsets in the horizontal
- GridTools positional computations
- Extents taking into account restricted computation
The best path forward might be to split the PR again into sub-tasks to make this easier to understand and have better test coverage.

## Potential Rabbit Holes

A primary concern is that both AI2 and CSCS get focused on other projects and this falls down the list of priorities.

Splitting the monolithic horizontal regions pull request into multiple and adding tests might take long.

## No Gos

Features for the physics ports.