us VS entt

It might be easier to think about it as a stack, rather than a tree. Each element of the stack represents a subtree -- a perfect binary tree. If you ever have two subtrees of height k, you merge them together into one subtree of height k+1. Your stack might already have another subtree of height k+1; if so, you repeat the process, until there's at most one subtree of each height.

This process is isomorphic to binary addition. Worked example: let's start with a single leaf, i.e. a subtree of height 0. Then we "add" another leaf; since we now have a pair of two equally-sized leaves, we merge them into one subtree of height 1. Then we add a third leaf; now this one doesn't have a sibling to merge with, so we just keep it. Now our "stack" contains two subtrees: one of height 1, and one of height 0.

Now the isomorphism: we start with the binary integer 1, i.e. a single bit at index 0. We add another 1 to it, and the 1s "merge" into a single 1 bit at index 1. Then we add another 1, resulting in two 1 bits at different indices: 11. If we add one more bit, we'll get 100; likewise, if we add another leaf to our BNT, we'll get a single subtree of height 2. Thus, the binary representation of the number of leaves "encodes" the structure of the BNT.

This isomorphism allows you to do some neat tricks, like calculating the size of a Merkle proof in 3 asm instructions. There's some code here if that helps: https://github.com/lukechampine/us/blob/master/merkle/stack....

You could also check out section 5.1 of the BLAKE3 paper: https://github.com/BLAKE3-team/BLAKE3-specs/blob/master/blak...

This isn't what I'm asking for - I don't care if it's baked into us, exists as a backend for minio, uses PseudoKV https://github.com/lukechampine/us/issues/67, or whatever the case may be. I see no value in sending any third party my private data in an unencrypted form (uploading to your server, even if over HTTPS, you got my data).

EnTT is a popular alternative to flecs for C++, which has different performance/memory characteristics.

https://pastebin.com/VPypiitk This is a very small experiment i did to learn the metaprogramming features. its an ECS library using the same model as entt (https://github.com/skypjack/entt). In 200 lines or so it does the equivalent of a few thousand lines of template heavy Cpp while compiling instantly and generating good debug code.

Some walkthrough:

Line 8 declares a SparseSet type as a fairly typical template. its just a struct with arrays of type T inside. Next lines implement getters/setters for this data structure

Line 46 Base_Registry things get interesting. This is a struct that holds a bunch of SparseSet of different types, and providers getters/setters for them by type. It uses code generation to do this. The initial #insert at the start of the class injects codegen that creates structure members from the type list the struct gets on its declaration. Note also how type-lists are a native structure in the lang, no need for variadics.

Line 99 i decide to do variadic style tail templates anyway for fun. I implement a function that takes a typelist and returns the tail, and the struct is created through recursion as one would do in cpp. Getters and setters for the View struct are also implemented through recursion

Line 143 has the for expansion. This is how you overload the for loop functionality to create custom iterators.

The rest of the code is just some basic test code that runs the thing.

Since we wanted a common game simulation that would be on both the server and the client we looked into a few libraries that would fit our ECS needs. It was decided we were going to write this common part of our game in C++, but rust was considered. C++ was a familiar language for us so naturally EnTT and flecs came up right away. I had used EnTT before, writing some small demo projects, so our choice was made based on familiarity. In order to integrate with Unity we created a small C interface to communicate between our simulation code and Unity’s C#. Here’s close to what it looked like. I removed some parts for brevity sake.

Are you sure you don't want to use a C++ package manager? Libtcod is on Vcpkg and with that setup you could add the fmt library or EnTT. fmt fixes C++'s string handling and EnTT fixes everything wrong with the entities of the previous tutorials.

There's also a performance question. While we can now use Blueprint nativization to convert Blueprints to C++ the result will be a fairly naive version, fast enough for most purposes but not if you're trying to push every bit of performance. This is where you're looking at making sure you're hitting things such as using the CPU cache as well as possible for an ECS system (Look at ENTT or Flecs if you want to see what they're about and why you'd want one), or a system needing to process massive amounts of data quickly such as the Voxel Plugin.

For a modern engine you’re probably best looking at Unity’s DOTS. You may also want to check out some of the different open source ECS libraries such as flecs and EnTT are two popular ones for C++, but there’s lots of them. Largely you’ll see lots of different approaches taken, all with their own pros and cons. Not all of them will be performant (some focus more on the design benefits) while others will be optimised for certain use cases. What you should prioritise will depend on your specific needs.

You can think of DynaMix as combining one of these libraries with an ECS like entt(https://github.com/skypjack/entt)