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> it turns an optimization done out of technical necessity into a gameplay feature And this folks is why an optimizing compiler can never beat sufficient quantities of human optimization. The human can decide when the abstraction layers should be deliberately broken for performance reasons. A compiler cannot do that.
> Imagine a programmer asking a game designer if they could change their formula to use an 8 instead of a 9.5 because it is a number that the CPU prefers to calculate with. There is a very good argument to be made that a game designer should never have to worry about the runtime performance characteristics of binary arithmetic in their life, that’s a fate reserved for programmers Numeric characteristics are absolutel…
Examples?
I had always heard about how RCT was built in Assembly, and thought it was very impressive. The more I actually started digging into assembly, the more this task seems monumental and impossible. I didn't know there was a fork and I'm excited to look into it
Now writing very optimized assembly is very hard. Because you need to break your consistency and conventions to squeeze out all the possible performance. The larger "kernel" you optimize the more pattern breaking code you need to keep in your head at a time.
> it turns an optimization done out of technical necessity into a gameplay feature And this folks is why an optimizing compiler can never beat sufficient quantities of human optimization. The human can decide when the abstraction layers should be deliberately broken for performance reasons. A compiler cannot do that.
Great write up. Thank you. Really great! I was reminded of the factorio blog. That game's such a huge optimization challenge even by today's standards and I believe works with the design. One interesting thing I remember is if you have a long conveyor belt of 10,000 copper coils, you can basically simplify it to just be only the entry and exit tile are actually active. All the others don't actually have to move becau…
Earlier quoted context omitted.
Examples?
One of the main issues with Kerbal Space Program is instability caused by floating point numbers. I know Starcraft 2 was built upon integers.
> Imagine a programmer asking a game designer if they could change their formula to use an 8 instead of a 9.5 because it is a number that the CPU prefers to calculate with. There is a very good argument to be made that a game designer should never have to worry about the runtime performance characteristics of binary arithmetic in their life, that’s a fate reserved for programmers Numeric characteristics are absolutel…
> Imagine a programmer asking a game designer if they could change their formula to use an 8 instead of a 9.5 because it is a number that the CPU prefers to calculate with. There is a very good argument to be made that a game designer should never have to worry about the runtime performance characteristics of binary arithmetic in their life, that’s a fate reserved for programmers Numeric characteristics are absolutel…
I used to think like this, not anymore.
What convinced me that these sort of micro-optimizations just don't matter is reading up on the cycle count of modern processors.
One a Zen 5, Integer addition is a single cycle, multiplication 3, and division ~12. But that's not the full story. The CPU can have 5 inflight multiplications running simultaneously. It can have about 3 divisions running simultaneously.
Back in the day of RCT, there was much less pipelining. For the original pentium, a multiplication took 11 cycles, division could take upwards of 46 cycles. These were on CPUs with 100 Mhz clock cycles. So not only did it take more cycles to finish, couldn't be pipelined, the CPUs were also operating at 1/30th to 1/50th the cycle rate of common CPUs today.
And this isn't even touching on SIMD instructions.
Integer tricks and optimizations are pointless. Far more important than those in a modern game is memory layout. That's where the CPU is actually going to be burning most it's time. If you can create and do operations on a int[], you'll be MUCH faster than if you are doing operations against a Monster[]. A cache miss is going to mean anywhere from a 100 to 1000 cycle penalty. That blows out any sort of hit you take cutting your cycles from 3 to 1.
Earlier quoted context omitted.
Examples?
I think Minecraft's lighting system is a good example: there are 16 different brightness levels, from 0 to 15. This allows the game to store light levels in 4 bytes per block. Similarly, redstone has 16 power levels: 0 to 15. This allows it to store the power level using 4 bits. In fact, quite a lot of attributes in Minecraft blocks are squeezed into 4 bits. I think the system has grown to be more flexible these days…