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I know fixed point was very important back in the days when CPUs didn't have dedicated floating point instructions. How important is it now, when most common CPUs have fast floating point operations? Is there still a performance win? Do games and similar software use them today?
I used fixed point for my game's physics, because I wanted things to be deterministic across platforms and compilers (the game has a hidden "solver" which is used to tweak things a little bit to make the game more fun, but this involves rerunning simulations multiple times).
I know fixed point was very important back in the days when CPUs didn't have dedicated floating point instructions. How important is it now, when most common CPUs have fast floating point operations? Is there still a performance win? Do games and similar software use them today?
I know fixed point was very important back in the days when CPUs didn't have dedicated floating point instructions. How important is it now, when most common CPUs have fast floating point operations? Is there still a performance win? Do games and similar software use them today?
They are still popular for multiplayer games that has a synced game state. In all clients you want to get exact same results when they run same code which is not possible with fp
I know fixed point was very important back in the days when CPUs didn't have dedicated floating point instructions. How important is it now, when most common CPUs have fast floating point operations? Is there still a performance win? Do games and similar software use them today?
I know fixed point was very important back in the days when CPUs didn't have dedicated floating point instructions. How important is it now, when most common CPUs have fast floating point operations? Is there still a performance win? Do games and similar software use them today?
The main appeal of fixed point nowadays is determinism across hardware - so networked games benefit, for instance.
Earlier quoted context omitted.
On the PIC32, fixed add is ~2 cycles and floating point is is ~60. And about a 2x increase for multiplies. On architectures with floating point hardware some of the advantage is lost, but it's fantastic for DSP on microcontrollers.
Do you have numbers for x86? A web search didn't give me a clear answer, especially for non-vectorized code.
Mid-range smartphones will generally have acceptable floating point units, and you should stick to floating point math. If you're targeting low end smartphones, you never know what you're going to get.
Fixed point is generally only still useful on embedded. If you're building software for fixed point, it's generally because you know exactly what CPU your software is going to run on, and you know it doesn't have a FPU.
I know fixed point was very important back in the days when CPUs didn't have dedicated floating point instructions. How important is it now, when most common CPUs have fast floating point operations? Is there still a performance win? Do games and similar software use them today?
Integer arithmetic is still simpler to implement in hardware and therefore faster than floating point arithmetic, so it is still heavily used for resource-constrained numerical programs. This shows up in signal processing code for e.g. very low-level network software, radios, and image processing. It is also popular for running efficient neural net inference. In neural nets, it is usually paired with reduced precisio…
This is true in the abstract, but not necessarily true of a specific commodity chip. Processor vendors spend a lot of silicon on offering low latency and high throughput floating point support. It's a fairly recent trend of processor vendors adding fast int8 or bfloat16 vectors after the ML craze demonstrated that there was demand for vector support for more bandwidth-friendly datatypes.
I used fixed point for my game's physics, because I wanted things to be deterministic across platforms and compilers (the game has a hidden "solver" which is used to tweak things a little bit to make the game more fun, but this involves rerunning simulations multiple times).
Did you use stdfix, another library, or just hand-roll it?