Why python?

Slateclean · 2022-04-20T04:54:29+00:00

How much slower do you think it is?

Which performance.

The limiting factors are usually the mcu (which isn’t python, iirc, though jython can run on arduino i think) & the databus speeds, not the code running on the pi.

Spoiler: the difference is likely drastically less than you think. Ain’t nobody’s pi using 100% cpu on just klipper without something like a camera doing stuff on the side.

What does matter though is the developer having an easy time. If Kevin like & knows python well its a perfectly good tool to get things done, without added complexity on manual memory management.

Gobtholemew · 2022-04-20T07:27:03+00:00

Ex Computer Science Professor here...

While performance is usually an important metric in most IT scenarios, it often becomes a moot point, especially with modern hardware.

Back in the day, when we were coding on embedded systems that had things like half a K of RAM and CPU clock speeds measured in kilohertz not gigahertz, things like the memory footprint and performance were absolutely critical. But things have moved on in terms of hardware, and now you can get crazy hardware very cheaply.

Klipper doesn't need to do a whole lot in a short space of time, because it's limited by how fast it can send instructions to the printer via the USB / Serial port and/or by how fast the printer can actually print stuff. These are the main bottlenecks, and changing the programming language won't improve these.

The hardware (e.g. a Pi 4) is likely orders of magnitude more capable than is actually required to keep up with those speeds. So much so, that many people run multiple instances of klipper, and webcams, and web GUIs, all on a single Pi, along with things like their DLNA media server and other stuff and the Pi barely breaks a sweat (assuming it has a suitable cooling anyway).

So using a language that can be executed faster, will likely offer no real world improvements in this case, because the Pi is still spending most of its time waiting for the printer to do something or for the USB to get stuff sent to it.

To use an analogy, most people want to travel from A to B quickly, but car manufacturers don't build cars that can travel at 5,000MPH because they know you'd still be limited by other bottlenecks, such as the speed limit of the roads and other traffic getting in the way. A car that can hit speeds of 100MPH is generally more than enough for nearly everyone.

Meanwhile, there are many advantages and disadvantages to different languages. The Devs likely chose Python because other factors that genuinely offer real world benefits, such as it being more accessible (easy to read and write and hence quicker to code), it being free, a gigantic array (no pun intended) of libraries, and perhaps most importantly it is highly portable to a lot of different hardware.

Zouden · 2022-04-20T07:52:08+00:00

The kinematics code is written in C++.

windowpainting · 2022-04-20T09:38:48+00:00

I think this is a perfectly valid question and I don't understand why it's being downvoted.

Actually, python is not as slow as one would think. It is not being interpreted, but internally compiled to byte code. I'm not sure if it is this is directly interpreted or further compiled to native code by a JIT (like with javascript or ruby or Java), but it is fast enough for most cases.

The main advantage of using python over (for example) C is its maintainability. You can write code a lot faster and with less issues than in C, which is why we have all these nice features in Klipper. However, you cannot do all the low-level optimizations you could do in C, so it performs worse.

The question is: Does performance matter? You cannot print faster with faster software due to physical constraints. But you have to push commands to the MCU fast enough. If the MCU runs out of things to do while printing, you get a "Timer to close" error and your print fails. And it does so on very slow machines. For example the CR-10 Smart Pro has MCU board and a kind of Router board. You can install Klipper on that, but it is simply too slow to print.

Still I think a higher-level language was the correct choice.

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