From 815f19f7089f6fc8a6efa3396433b799b91d7a44 Mon Sep 17 00:00:00 2001
From: dapplion <35266934+dapplion@users.noreply.github.com>
Date: Tue, 11 Jul 2023 22:22:37 +0200
Subject: [PATCH] Add limit churn feature

---
 specs/_features/limit_churn/beacon_chain.md | 52 +++++++++++++++++++++
 1 file changed, 52 insertions(+)
 create mode 100644 specs/_features/limit_churn/beacon_chain.md

diff --git a/specs/_features/limit_churn/beacon_chain.md b/specs/_features/limit_churn/beacon_chain.md
new file mode 100644
index 0000000000..a2295f38e3
--- /dev/null
+++ b/specs/_features/limit_churn/beacon_chain.md
@@ -0,0 +1,52 @@
+Limit churn -- The Beacon Chain
+
+## Table of contents
+
+<!-- TOC -->
+<!-- START doctoc generated TOC please keep comment here to allow auto update -->
+<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
+
+- [Introduction](#introduction)
+- [Configuration](#configuration)
+  - [Validator cycle](#validator-cycle)
+- [Helper functions](#helper-functions)
+  - [Beacon state accessors](#beacon-state-accessors)
+    - [modified `get_validator_churn_limit`](#modified-get_validator_churn_limit)
+
+<!-- END doctoc generated TOC please keep comment here to allow auto update -->
+<!-- /TOC -->
+
+## Introduction
+
+This is the beacon chain specification to limit the max churn value, motivated to limit the validator active set growth rate.
+
+*Note:* This specification is built upon [Capella](../../capella/beacon_chain.md) and is under active development.
+
+## Configuration
+
+### Validator cycle
+
+| Name | Value |
+| - | - |
+| `MAX_PER_EPOCH_CHURN_LIMIT` | `uint64(12)` (= 12) |
+
+## Helper functions
+
+### Beacon state accessors
+
+#### modified `get_validator_churn_limit`
+
+```python
+def get_validator_churn_limit(state: BeaconState) -> uint64:
+    """
+    Return the validator churn limit for the current epoch.
+    """
+    active_validator_indices = get_active_validator_indices(state, get_current_epoch(state))
+    return min(
+      MAX_PER_EPOCH_CHURN_LIMIT,
+      max(
+        MIN_PER_EPOCH_CHURN_LIMIT,
+        uint64(len(active_validator_indices)) // CHURN_LIMIT_QUOTIENT
+      )
+    )
+```