Incoming links: Ruby on Rails
These are the best articles ever authored by Ciro Santilli, most of them in the format of Stack Overflow answers.
Ciro posts update about new articles on his Twitter accounts.
A chronological list of all articles is also kept at: Section "Updates".
Some random generally less technical in-tree essays will be present at: Section "Essays by Ciro Santilli".
- Trended on Hacker News:
- CIA 2010 covert communication websites on 2023-06-11. 190 points, a mild success.
- x86 Bare Metal Examples on 2019-03-19. 513 points. The third time something related to that repo trends. Hacker news people really like that repo!
- again 2020-06-27 (archive). 200 points, repository traffic jumped from 25 daily unique visitors to 4.6k unique visitors on the day
- How to run a program without an operating system? on 2018-11-26 (archive). 394 points. Covers x86 and ARM
- ELF Hello World Tutorial on 2017-05-17 (archive). 334 points.
- x86 Paging Tutorial on 2017-03-02. Number 1 Google search result for "x86 Paging" in 2017-08. 142 points.
- x86 assembly
- What does "multicore" assembly language look like?
- What is the function of the push / pop instructions used on registers in x86 assembly? Going down to memory spills, register allocation and graph coloring.
- Linux kernel
- What do the flags in /proc/cpuinfo mean?
- How does kernel get an executable binary file running under linux?
- How to debug the Linux kernel with GDB and QEMU?
- Can the sys_execve() system call in the Linux kernel receive both absolute or relative paths?
- What is the difference between the kernel space and the user space?
- Is there any API for determining the physical address from virtual address in Linux?
- Why do people write the
#!/usr/bin/envpython shebang on the first line of a Python script? - How to solve "Kernel Panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)"?
Figure 2. Path from init/main.c until bzImage in the Linux kernel 4.19. Source. From: What is the difference between the following kernel Makefile terms: vmLinux, vmlinuz, vmlinux.bin, zimage & bzimage?- Single program Linux distro
- QEMU
- gcc and Binutils:
- How do linkers and address relocation works?
- What is incremental linking or partial linking?
- GOLD (
-fuse-ld=gold) linker vs the traditional GNU ld and LLVM ldd - What is the -fPIE option for position-independent executables in GCC and ld? Concrete examples by running program through GDB twice, and an assembly hello world with absolute vs PC relative load.
- How many GCC optimization levels are there?
- Why does GCC create a shared object instead of an executable binary according to file?
- C/C++: almost all of those fall into "disassemble all the things" category. Ciro also does "standards dissection" and "a new version of the standard is out" answers, but those are boring:
- What does "static" mean in a C program?
- In C++ source, what is the effect of
extern "C"? - Char array vs Char Pointer in C
- How to compile glibc from source and use it?
- When should
static_cast,dynamic_cast,const_castandreinterpret_castbe used? - What exactly is
std::atomicin C++?. This answer was originally more appropriately entitled "Let's disassemble some stuff", and got three downvotes, so Ciro changed it to a more professional title, and it started getting upvotes. People judge books by their covers. notmain.o 0000000000000000 0000000000000017 W MyTemplate<int>::f(int) main.o 0000000000000000 0000000000000017 W MyTemplate<int>::f(int)Code 1.. From: What is explicit template instantiation in C++ and when to use it?nmoutputs showing that objects are redefined multiple times across files if you don't use template instantiation properly
- IEEE 754
- What is difference between quiet NaN and signaling NaN?
- In Java, what does NaN mean?
Without subnormals: +---+---+-------+---------------+-------------------------------+ exponent | ? | 0 | 1 | 2 | 3 | +---+---+-------+---------------+-------------------------------+ | | | | | | v v v v v v ----------------------------------------------------------------- floats * **** * * * * * * * * * * * * ----------------------------------------------------------------- ^ ^ ^ ^ ^ ^ | | | | | | 0 | 2^-126 2^-125 2^-124 2^-123 | 2^-127 With subnormals: +-------+-------+---------------+-------------------------------+ exponent | 0 | 1 | 2 | 3 | +-------+-------+---------------+-------------------------------+ | | | | | v v v v v ----------------------------------------------------------------- floats * * * * * * * * * * * * * * * * * ----------------------------------------------------------------- ^ ^ ^ ^ ^ ^ | | | | | | 0 | 2^-126 2^-125 2^-124 2^-123 | 2^-127Code 2.Visualization of subnormal floating point numbers vs what IEEE 754 would look like without them. From: What is a subnormal floating point number?
- Computer science
- Algorithms
- Is it necessary for NP problems to be decision problems?
- Polynomial time and exponential time. Answered focusing on the definition of "exponential time".
- What is the smallest Turing machine where it is unknown if it halts or not?. Answer focusing on "blank tape" initial condition only. Large parts of it are summarizing the Busy Beaver Challenge, but some additions were made.
- Algorithms
- Git
| 0 | 4 | 8 | C | |-------------|--------------|-------------|----------------| 0 | DIRC | Version | File count | ctime ...| 0 | ... | mtime | device | 2 | inode | mode | UID | GID | 2 | File size | Entry SHA-1 ...| 4 | ... | Flags | Index SHA-1 ...| 4 | ... |tree {tree_sha} {parents} author {author_name} <{author_email}> {author_date_seconds} {author_date_timezone} committer {committer_name} <{committer_email}> {committer_date_seconds} {committer_date_timezone} {commit message}Code 4.Description of the Git commit object binary data structure. From: What is the file format of a git commit object data structure?- How do I clone a subdirectory only of a Git repository?
- Python
- Web technology
- OpenGL
Figure 8. Example of a texture atlas containing glyphs. Source.Image by Nicolas P. Rougier, author of Freetype GL.Used on Ciro Santilli's answer: How to draw text using only OpenGL methods?- What are shaders in OpenGL?
- Why do we use 4x4 matrices to transform things in 3D?
Figure 10. . Source. - Image Processing with GLSL shaders? Compared the CPU and GPU for a simple blur algorithm.
- Node.js
- Ruby on Rails
- POSIX
- What is POSIX? Huge classified overview of the most important things that POSIX specifies.
- Systems programming
- What do the terms "CPU bound" and "I/O bound" mean?
Figure 12. Plot of "real", "user" and "sys" mean times of the output of time for CPU-bound workload with 8 threads. Source. From: What do 'real', 'user' and 'sys' mean in the output of time?+--------+ +------------+ +------+ | device |>---------------->| function 0 |>----->| BAR0 | | | | | +------+ | |>------------+ | | | | | | | +------+ ... ... | | |>----->| BAR1 | | | | | | +------+ | |>--------+ | | | +--------+ | | ... ... ... | | | | | | | | +------+ | | | |>----->| BAR5 | | | +------------+ +------+ | | | | | | +------------+ +------+ | +--->| function 1 |>----->| BAR0 | | | | +------+ | | | | | | +------+ | | |>----->| BAR1 | | | | +------+ | | | | ... ... ... | | | | | | +------+ | | |>----->| BAR5 | | +------------+ +------+ | | | ... | | | +------------+ +------+ +------->| function 7 |>----->| BAR0 | | | +------+ | | | | +------+ | |>----->| BAR1 | | | +------+ | | ... ... ... | | | | +------+ | |>----->| BAR5 | +------------+ +------+Code 5.Logical struture PCIe device, functions and BARs. From: What is the Base Address Register (BAR) in PCIe?
- Electronics
- Raspberry Pi
Figure 13. . Image from answer to: How to hook up a Raspberry Pi via Ethernet to a laptop without a router? 
Figure 14. . Image from answer to: How to hook up a Raspberry Pi via Ethernet to a laptop without a router? 
Figure 15. . Image from answer to: How to emulate the Raspberry Pi 2 on QEMU? 
Figure 16. Bare metal LED blinker program running on a Raspberry Pi 2. Image from answer to: How to run a C program with no OS on the Raspberry Pi?
- Raspberry Pi
- Computer security
- Media
Video 2. Canon in D in C. Source.The original question was deleted, lol...: How to programmatically synthesize music?- How to resize a picture using ffmpeg's sws_scale()?
- Is there any decent speech recognition software for Linux? ran a few examples manually on
vosk-apiand compared to ground truth.
- Eclipse
- Computer hardware
- Scientific visualization software
Figure 17. VisIt zoom in 10 million straight line plot with some manually marked points. Source. From: Section "Survey of open source interactive plotting software with a 10 million point scatter plot benchmark by Ciro Santilli"
- Numerical analysis
Video 3. Real-time heat equation OpenGL visualization with interactive mouse cursor using relaxation method by Ciro Santilli (2016)Source.
- Computational physics
Figure 18. gnuplot plot of the y position of a sphere bouncing on a plane simulated in Bullet Physics. Source. From: What is the simplest collision example possible in a Bullet Physics simulation?
- Register transfer level languages like Verilog and VHDL
- Verilog:
Figure 19. . See also: Section "Verilator interactive example"
- Verilog:
- Android
Video 4. Android screen showing live on an Ubuntu laptop through ADB. Source. From: How to see the Android screen live on an Ubuntu desktop through ADB?
- Debugging
- Program optimization
- What is tail call optimization?
Figure 21. gprof2dot image generated from the gprof data of a simple test program. Source.The answer compares gprof, valgrind callgrind, perf and gperftools on a single simple executable.
- Data
Figure 22. Mathematics dump of Wikipedia CatTree. Source. In this project, Ciro Santilli explored extracting the category and article tree out of the Wikipedia dumps.
- Mathematics
Figure 23. Diagram of the fundamental theorem on homomorphisms by Ciro Santilli (2020)Shows the relationship between group homomorphisms and normal subgroups.- Section "Formalization of mathematics": some early thoughts that could be expanded. Ciro almost had a stroke when he understood this stuff in his teens.
Figure 24. Simple example of the Discrete Fourier transform. Source. That was missing from Wikipedia page: en.wikipedia.org/wiki/Discrete_Fourier_transform!
- Network programming
- Physics
- What is the difference between plutonium and uranium?
Figure 25. Spacetime diagram illustrating how faster-than-light travel implies time travel. From: Does faster than light travel imply travelling back in time?
- Biology
Figure 27. Mass fractions in a minimal growth medium vs an amino acid cut in a simulation of the E. Coli Whole Cell Model by Covert Lab. Source. From: Section "E. Coli Whole Cell Model by Covert Lab"
- Quantum computing
- Section "Quantum computing is just matrix multiplication"
Figure 28. Visualization of the continuous deformation of states as we walk around the Bloch sphere represented as photon polarization arrows. From: Understanding the Bloch sphere.
- Bitcoin
- GIMP
Figure 29. GIMP screenshot part of how to combine two images side-by-side in GIMP?.
- Home DIY
Figure 30. Total_Blackout_Cassette_Roller_Blind_With_Curtains.Source. From: Section "How to blackout your window without drilling"
- China
Only patches which were reviewed by at least one person with push permission will be listed here.
This may also include patches which were rejected in favor of another patch, but strongly influenced the merged patch.
One of the least evil of the big tech companies of the early 21st century, partly because Sergey Brin's parents fled from the Soviet Union and so he is anti censorship, although they have been tempted by it.
Google only succeeds at highly algorithmic tasks or at giving infinite storage to users to then mine their data.
It is incapable however of adding any obvious useful end user features to most of its products, most of which get terminated and cannot be relied on:
This also seems to extend to business-to-business: twitter.com/MohapatraHemant/status/1343969802080030720 ex-Googler tells how they lost the cloud to Amazon.
More mentions of that:
- world.hey.com/dhh/google-suffers-from-a-digital-petro-curse-908e919a "Google suffers from a digital petro curse" by David Heinemeier Hansson (2021), the creator of Ruby on Rails
- killedbygoogle.com/ dedicated website, source on GitHub: github.com/codyogden/killedbygoogle
Too many genius engineers. They need some dumber people like Ciro Santilli who need to write documentation to learn stuff.
Ciro Santilli actually attempted two interviews to work at Google in the early 2010's but very quickly failed both on the first phase, because you have to be a fast well trained coding machine to pass that interview.
Ciro later felt better about himself by fantasizing how he would actually do more important things outside of Google and that they would beg to buy him instead.
He was also happy that he wouldn't have to use Google crazy internal tools: someone once said that Google's tools make easy tasks middle hard, and they also make impossible tasks middle hard. TODO source.
But whatever the case: Ciro will not, ever, spend his time drilling programmer competition problems to join a company.
www.wired.com/story/google-shakes-up-its-tgif-and-ends-its-culture-of-openness/ "GOOGLE TGIF 1999 video". TGIF is the weekly all hands meeting abolished in 2019: www.wired.com/story/google-shakes-up-its-tgif-and-ends-its-culture-of-openness/
Founder: Peter Armstrong
The general idea is publishing entire books with usual copyright, but with gradual updates.
ruboss.com/ documents their stack, a somewhat similar choice to OurBigBook.com as of 2021, notably Next.js. But backend in Ruby on Rails. They actually managed Apollo/GraphQL, which Ciro Santilli would have liked, but din't have the patience for.
The founder/CEO Peter Armstrong www.linkedin.com/in/peterburtonarmstrong/ He looks like a nice guy.
In any case, the outcome of that is that the tech has improved. And I have done a relatively good job of clearly publishing any "more user visible" improvements to docs.ourbigbook.com/news and social media such as though it is important to note that there have been more than one "fix a hard bug" weeks that were not published because they would just bore readers.
During this period the main focus has been on improving OurBigBook Web, i.e. the dynamic website that powers OurBigBook.com. There are two reasons for that:As a result, Web is now way less buggy and much more usable.
- Web is what has the OurBigBook topics feature for mind-melding, which is the killer feature of OurBigBook compared to other note taking apps and therefore deserves the highest levels of priorityStatic website generation is an indispensable escape valve that ensures that your content can be published forever even if OurBigBook.com goes down one day, which it won't as long as I live. But the innovation is Web.
- static website generation was closer to good enough, but web was much further and is fundamentally harder.I'm extremely satisfied with OurBigBook static website generation and haven't touched it as much. It wasn't easy to reach this state, but I'm there.But Web is a different and much more complex beast.Making CLI software that will run on a person's local computer under full trust and building a bunch of HTML from lightweight markup in bulk is one thing.But making a public dynamic website that has to continuously maintain a coherent database state on granular updates, while giving users some trust but not enough for them to blow everything up is on a totally different level. See e.g. the recent SPAM attack we've had to fend off.
Figure 1. Screenshot showing voting manipulated SPAM as the most highly upvoted article on OurBigBook.com. Source.And then there's also the issue of front-end being mega-hard to get right.
If you look through the list of Web updates, there is nothing specifically mind blowing. The core ideas have largely crystallized, and we are just trying to making them click. I have a few more punches up my sleeve, but the core is decided.
OurBigBook Web search
. Source. This is one of the many basic quality of life improvements that have been done on OurBigBook Web.
OurBigBook Web article announcement
. Source. Another cute new feature, you can send an email to your followers about a new amazing article you created.Web process has been somewhat slower than what I'd like. Of course, it is the case of any project that things are easily said than done. But there are two other main structural factors that have played into it:
- I have my first baby now, and we're learning how to deal with that on the fly.For example, we could have put him on childcare a bit earlier, but due to inexperience we've kept him a bit longer than we maybe should have.Things are well sorted out now, but not matter how good your support system is, at the end of the day, and more often night, it is you the parents that have to deal with a lot of inevitable baby issues. Unless you want them to turn into psychopaths and drug addicts that is, which I don't. I've reached the point of semi failure middle age that the baby feels like my best moonshot.All of this sets a fundamental limit on how many hours you can work per week.But at least with the donations I was able to work on OurBigBook at all. Because if it weren't for that, I would have to focus entirely on the generic job instead and OurBigBook would have been put on hold.
- the choice of Web stack. I was allured by Next.js. I can see the beauty and usefulness of a Node.js render front-end that also runs on backend and hydration. That is awesome.But:
- React is insanely hard to learn and understand. Furthermore, it is also hard to understand the performance problem that it solves, and actually have a benchmark where this problem is solved faster than just delivering some HTML files with ad-hoc Js on top.
- the lack (or perhaps excess of shitty) actual web framework like Ruby on Rails and Django means that I have to rediscover the wheel many times over for all the essential support activities like testing, login and so one
At this point a rewrite is out of the question. I've managed to master things well enough to get a decent result, and given up on the few things that I couldn't for the life of me achieve, after documenting them very well for posterity of course.
Aside from Web, there was only one thing that received a significant improvement, and that was the OurBigBook VS Code extension. The extension is not perfect, and it is not the "final UI", which has to be some WYSIWYG implementation, and there are some fundamental limitations that cannot be overcome without patching VS Code itself. However, the extension is already extremely usable, and I'm writing this on it right now. Basics like syntax highlighting, jump to definition and autocomplete are very useful and usable.
Tree navigation in the OurBigBook Visual Studio Code extension
.