From 06fcb2531edbb040aa15e5506109511d377f7c10 Mon Sep 17 00:00:00 2001
From: Andrew Noyes <andrew@weaselab.dev>
Date: Fri, 8 Mar 2024 17:04:22 -0800
Subject: [PATCH] Add an analysis on memory usage in static asserts

CC #9
---
 ConflictSet.cpp | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/ConflictSet.cpp b/ConflictSet.cpp
index 891320b..1f3843b 100644
--- a/ConflictSet.cpp
+++ b/ConflictSet.cpp
@@ -247,6 +247,19 @@ struct Node256 : Node {
   uint8_t *partialKey() { return (uint8_t *)(this + 1); }
 };
 
+// Bound memory usage following the analysis in the ART paper
+
+constexpr int kBytesPerKey = 86;
+constexpr int kMinChildrenNode4 = 2;
+constexpr int kMinChildrenNode16 = 5;
+constexpr int kMinChildrenNode48 = 17;
+constexpr int kMinChildrenNode256 = 49;
+
+static_assert(sizeof(Node256) < kMinChildrenNode256 * kBytesPerKey);
+static_assert(sizeof(Node48) < kMinChildrenNode48 * kBytesPerKey);
+static_assert(sizeof(Node16) < kMinChildrenNode16 * kBytesPerKey);
+static_assert(sizeof(Node4) < kMinChildrenNode4 * kBytesPerKey);
+
 // Bounds memory usage in free list, but does not account for memory for partial
 // keys.
 template <class T, size_t kMemoryBound = (1 << 20)>