, 2022/4/8: Original
2022/6/17: Revised to stress importance of not bundling features in a single PR
2022/8/31: Revised to remove duplicate terminology section
2023/4/18: Revised to clarify that modifications to an existing stealth feature is considered a stealth feature.
This document describes the policy for bringing in new features and changing existing code in the E3SM model. This new policy requires a significant amount of work improving the E3SM diagnostics, CIME test suites and developing documentation, collected /wiki/spaces/CNCL/pages/3315138566
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BFB (bit-for-bit)
New code produces results which are bit-for-bit identical with old code
Does not contain stealth features
github PR label: BFB
Roundoff
New code would match old code in exact arithmetic, but will diverge exponentially fast when using finite precision
Climate of new and old code will converge as the averaging time goes to infinity
github PR label: non-BFB
Climate changing
New feature is brought into the model turned on
Other model configuration change (parameters, resolution, forcing data)
github PR label: CC
Stealth Feature
BFB code change that includes a new feature, turned off by default, or modifications to an existing stealth feature.
github PR labels: BFB and Stealth
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Coupled model: B-case runs (~100 years) for WC, cryosphere and BGC configurations
Component models: F, I and G cases, typically much shorter (e.g. 5 year F case with cyclic year 2010 forcing)
Updated periodically when climate changes are integrated, or monthly ( to check for unintended changes)
New features will be evaluated with respect to these reference solutions, with documentation on the import metrics
Note: E3SM Reference solutions and related documentation not yet ready!
Section 1: New Feature Request Process and Documentation Requirements
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