Variable Refresh Monitors and Animation

So variable refresh rates have a lot of hype surrounding them now, with representatives from GPU and monitor vendors are saying that it will just magically make existing games better with no effort required on the part of the developer. This is bullshit and you shouldn’t believe them. If you’re a developer you need to be careful to handle these new refresh rates and if you’re a customer you should consider just locking your monitor to 60Hz for games that don’t do the right thing.

Flags are a code smell

In most major code bases, it’s common to have objects with lots of Boolean flags indicating what state they’re in. E.g. is an enemy targeting the player or not? Is it trying to flee or not? If you have a set of mutually exclusive flags an enum can be used instead, but this is often not possible, and doesn’t change much in terms of the downsides. In my opinion these are code smells.

The Perils of Future-Coding

In my opinion, one of the most insidious form of technical debt is what I like to call future-coding. You might also call it over-engineering, second-system syndrome, etc. It’s code written in an overly elaborate and general way in order to, the future-coder reasons, pre-emptively handle use cases that we’ll “probably see in the future”. I find it more treacherous than plain “stupid code” because it predominantly affects smart people.

More on Robin Hood Hashing

I posted about Robin Hood hashing in a previous post. In the comments to that post David Wragg pointed out a flaw in my implementation: if you repeatedly delete and reinsert elements into a hashtable, the average probe count keeps rising. This is a good observation, and it’s true. Repeatedly deleting items makes the table slower but it (until you insert enough to trigger a rebuild of the table, which will filter out any tombstones - note: the number tombstones do not affect the rate of rebuilds).

Language Design Deal Breakers

I’m a bit of a programming language nerd. I love to learn new languages. That said, I spend most of my days writing C++. It’s a truly awful language, with many warts and problems, but I know it well and with enough effort and pain you can get the job done. The biggest benefit of C++ is purely an historical accident: it’s great because it’s popular. There’s no trouble finding people who know it, or libraries that work with it.

Robin Hood Hashing should be your default Hash Table implementation

There’s a neat variation on open-addressing based hash tables called Robin Hood hashing. This technique isn’t very well-known, but it makes a huge practical difference because it both improves performance and space utilization compared to other “standard” hash tables (e.g. chaining). It also eliminates the major downside of other open addressing hash tables. Here are the benefits, summarized: High load factors can be used without seriously affecting performance. 0.

Thoughts on Game Data Formats

I’ve been thinking about the representation and loading of game data recently. This has largely been the result of stumbling upon a variety of blog posts and libraries such as:  Desired characteristics So, the basic problem is that you want to store a large variety of “resources” for a game “level” (or “sector” or whatever), describing all sorts of things such as the location of every object, the vertices of every mesh, and so on.

On GC in Games (response to Jeff and Casey)

So it turns out youtube comments suck. I’ll write my response to Jeff and Casey’s latest podcast in blog form instead of continuing the discussion there. View it here: Now, first let me say that I agree with 99% of the sentiment of this podcast. I think writing high performance games in Java or C# is kinda crazy, and the current trend of writing apps in HTML5 and JavaScript and then running it on top of some browser-like environment is positively bonkers.

Runtime Code Specialization

Specializing code is nothing new, but I’m surprised that modern programming languages don’t attempt to make this easier. Just to give you some context, the idea is that whenever you have an algorithm that takes multiple parameters where one or more of the parameters are fixed for some period of time, you specialize the code for the fixed parameters in order to achieve greater optimization at runtime. A key idea is that you may not know at compile time what the fixed value is, and the duration for which a value is fixed could be shorter than the execution of the program (mere milliseconds, even).

Space-efficient Resizable Arrays

This post is about resizable arrays that would serve as an alternative to std::vector. You’re probably familiar with geometrically growing arrays like std::vector, so I won’t waste time describing them in detail. Briefly, they offer amortized constant-time append and lookups, but with a pretty severe cost to space overhead (as low as 33% utilization, after shrinking until you hit a realloc, or 50% if all you ever do is append). Another issue is that the elements of the array get copied ever so often.