Yesterday, we explored the differences between a Merkle DAG and vessel’s DAG. Today’s topic revolves around how combining wyrd’s conflict-free, replicated data type (CRDT) with vessel makes a specific kind of CRDT, namely a DAG-based one. Figure: “Fractal Structures” by SolomonVipe is licensed under CC BY-SA 2.0 Conflict-Free, Replicated Data Types A quick recap on CRDTs first. They’re data types, largely fairly simple ones, such as counters or sets. And they’re conflict-free, meaning that multiple parties can modify them concurrently, and when their respective modifications get synchronized, each party with the full set of modifications will reconstruct the same state.

One of the recurring conversations I’m having is on whether vessel is a Merkle DAG or Merkle Tree/Trie, and every time I have to start over with explaining that it is not. And this is a deliberate choice. In this post, I’d like to explore the differences – and this post will also kick off a mini series on how vessel and it’s sibling project wyrd together form a DAG-based conflict-free, replicated data type (CRDT) akin to a Merkle CRDT.

The recent issues with Google’s WEI proposal have provided for a few more views of this blog and website, which makes it worth diving into our work a little again. The previous post on resource access is quite old at this stage, after all. Quick Recap Under different grants, we’ve been working on a bunch of loosely related technologies. The highlights are: Channeler – a protocol that has can switch between UDP-like lossy and TCP-like lossless modes of connection, as well as novel modes suitable for live broadcast.

Previously, I wrote about how to use Valgrind for debugging memory issues – and today, I’d like to go into how to use the tool for profiling. As I wrote before, Valgrind is an instrumentation framework that provides a collection of tools. For profiling, we’ll look at the Callgrind tool together a GUI application called KCachegrind. As a quick historical note, the predecessor to Callgrind is called Cachegrind, and was mostly for examining CPU cache usage – but Callgrind was developed out of that.