That doesn't feel like a problem? As a PhD thesis, the cited works should cover the subjects, but there is no requirement for the citations to be direct, or even useful to the general public who want to "learn more" =)

If you just want to know the difference between CHAMP and HAMT, then Google gets you that information pretty swiftly. Maybe you were looking for https://blog.acolyer.org/2015/11/27/hamt which discusses HAMT and then discusses the improvements CHAMP brings to the table.

> That doesn't feel like a problem?

It doesn't make it a bad thesis, but also doesn't answer the questions asked, which is presumably why they were asked.

I was trying to tactfully suggest that google would have trivially found that answer instead of waiting for someone on HN to deliver the answer on a silver plate =)

I already found that "answer" and it wasn't very good or descriptive, so I was hoping someone on HN could give me an actual high-quality answer. People here often pull through with good, detailed answers.

They increase cache locality and runtime performance of iteration and equality checking. If that answer isn't sufficient, try watching the ~30min Clojure West video on the github page. The speaker seems to be a bit new to public speaking but his talk on the subject was easy to follow and informative for me.

The talk at Clojure West wasn't given by myself, but I found it worthwhile linking. Rather it was given by someone who independently picked up my research results and replicated them in the context of ClojureScript (https://github.com/bendyworks/lean-map). The authors independently confirmed the performance improvements of CHAMP over HAMT that I was observing.

You can also have a look at the JVMLS'16 talk (https://www.youtube.com/watch?v=pUXeNAeyY34) for a high-level overview of the work that is covered in my thesis.

From what I've read, it seems that the performance benefits disappear when compound data structures/objects are used as keys. Is this true?

Let's say that I were to use a vector of coordinates as the key to something in a map. Would CHAMP still vastly outperform HAMT?

Why should that be the case? Can you point to sources where you read that? In my experience, CHAMP clearly has advantages over HAMT in this scenario.

To answer your questions about using vectors of coordinates of keys: it depends on the design implementation of the vector's hash code, regardless if you use HAMT or CHAMP.

Using collections as keys in other collections is in general a performance sensitive subject. The available HAMT implementations in Clojure and Scala fail to deliver here. The case study in Chapter 3.7 nests hash-sets into hash-sets (i.e., Set.Immutable<Set.Immutable<K>> sets). The CHAMP implementation yields minimal speedups of ~10x over Clojure and Scala due to the way it calculates and incrementally updates the collection's hash code.

I was there and you are right, he was very nervous. However his talk was excellent and approachable for everyone reading the above comment. Explains the differences quite well. Certainly worth a talk. I've asked on the clojure slack group if the proposal had gone anywhere and it seems to have stalled unfortunately.