glibc VS Configurations

I am writing a short paper for school and the topic is Fast Inverse Square Root and alternatives. One of the questions is how the sqrt-function is implemented in glibc. Here is the code of that function.

The code isn't the easiest to read but in glibc it seems that the syscall is only performed if waiter are detected in userspace during an unlock operation

https://github.com/lattera/glibc/blob/master/nptl/pthread_mu...

You might still not realize, but floats are a large topic. Have a look at eg. this implementation here: https://github.com/lattera/glibc/blob/master/stdlib/strtod_l.c

This is a nice write up, thank you. However, I'm stilling interpreting this as a "fun trick" rather than the common sense method for solving the problem. For example, looking at the source code for htonl() from glibc: https://github.com/lattera/glibc/blob/master/inet/htonl.c

Second of all: The horrifying truth is that there is no such thing as a canonical text representation for IPv4 (source) (and yes... I am indeed citing the failed attempt to standardize this as my source for it not being standardized). Authoritatively speaking, all possible (non-binary) representations are equally invalid. In fact, text address resolution is typically delegated to the OS kernel, so what constitutes a "usable" address is liable to vary depending on if you're using Linux, OSX, Windows, or Other.

Optimized code gets really weird. The creators of strlen, for example, decided that iterating over each character to find the end was far too slow. So instead, they convert the character pointer into an int pointer and do bitwise manipulation with the int on two different magic numbers so they can check four/eight characters at once.

If you're using a cross-platform C compiler like gcc or clang, you're usually expected to switch to assembly. Here's the syscall instruction in glibc

Maybe you should include the math part of a libc statically with your code. glibc is one option, or dietlibc if you want it to be as small as possible.

Check Marlin‘s configuration repository at https://github.com/MarlinFirmware/Configurations for your specific board …

Go to the marlin github https://github.com/MarlinFirmware/Marlin and download the latest stable or bugfix release. Also, download the configurations that match the version of the firmware you downloaded https://github.com/MarlinFirmware/Configurations

Generally you would start with the Example config files from the Marlin Github https://github.com/MarlinFirmware/Configurations/tree/import-2.1.x/config/example

download Marlin configurations folder v2.0.9.6 from https://github.com/MarlinFirmware/Configurations

Current release, not bugfix branch? Started from the example config for your printer corresponding to the version of Marlin you downloaded?

Download the Marlin Example configs > https://github.com/MarlinFirmware/ConfigurationsThis contains the pre written configs for most popular printers so much of the config work is already done for you

I would add the Auto Build Marlin plugin (as well as PlatformIO) to your VS Code install, download the latest stable version of Marlin from the official source, along with the configuration examples. Copy the example Configuration.h and Configuration_adv.h for the Ender 3 Pro with Mini E3 V3, to your Marlin folder and compile that. The only important difference between an Ender 3 Pro and an Ender 3 V2, as far as firmware is concerned, is the V2 display, which you're not using, so don't use any of the config examples for a V2. The Pro version should have the correct serial port assignments: