Homotopy Updated 2025-07-16
Java (programming language) Updated 2025-07-16
Java is good.
Its boilerplate requirement is a pain, but the design is otherwise very clean.
But its ecosystem sucks.
The development process is rather closed, the issue tracker obscure.
And above all, Google LLC v. Oracle America, Inc. killed everybody's trust in it once and for all. Thanks Oracle.
Video 1.
Java for the Haters in 100 Seconds by Fireship (2022)
Source.
How large primes are found for RSA Updated 2025-07-16
Answers suggest hat you basically pick a random large odd number, and add 2 to it until your selected primality test passes.
The prime number theorem tells us that the probability that a number between 1 and is a prime number is .
Therefore, for an N-bit integer, we only have to run the test N times on average to find a prime.
Since say, A 512-bit integer is already humongous and sufficiently large, we would only need to search 512 times on average even for such sizes, and therefore the procedure scales well.
How the telephone works Updated 2025-07-16
Video 1.
Phone Intercom by Make (2014)
Source. This video illustrates will the incredible simplicity of the connection of a telephone system. Compare that to the relative complexity of wireless communication, which requires modulation.
Video 2.
Making a Microphone Work with an Oscilloscope by Environmental Radiation LLC (2012)
Source. Not the most detailed setup, but good.
How to become a good programmer? Updated 2025-07-16
Or: how to learn X.
This pops up on Reddit every week.
The right question is: what is the most awesome project I can do to improve the world?
Then, once you decide to try one, if that involves programming, only then learn to program to achieve that goal. And don't stop learning what's needed until you either get the thing done, or decide that it is actually not a good idea, or not possible, or that there is something else more important to be done first.
But if doesn't involve programming, then don't learn to program, and learn whatever you actually need to reach that goal instead.
Having that goal is the only way to be motivated to do something.
This is the essence of backward design.
How to decide if an ORM is good? Updated 2025-07-16
How to decide if an ORM is decent? Just try to replicate every SQL query from nodejs/sequelize/raw/many_to_many.js on PostgreSQL and SQLite.
There is only a very finite number of possible reasonable queries on a two table many to many relationship with a join table. A decent ORM has to be able to do them all.
If it can do all those queries, then the ORM can actually do a good subset of SQL and is decent. If not, it can't, and this will make you suffer. E.g. Sequelize v5 is such an ORM that makes you suffer.
The next thing to check are transactions.
Basically, all of those come up if you try to implement a blog hello world world such as gothinkster/realworld correctly, i.e. without unnecessary inefficiencies due to your ORM on top of underlying SQL, and dealing with concurrency.
The website moved from AsciiDoctor to OurBigBook Markup in 2020, making this section mostly useless. But hey, history!
Ciro's website is powered by GitHub Pages and Jekyll Asciidoc.
Build locally, watch for changes and rebuild automatically, and start a local server with:
git clone --recursive https://github.com/cirosantilli/cirosantilli.github.io
cd cirosantilli.github.io
bundle install
npm install
./run
Source: ./run.
The website will be visible at: localhost:4000.
Tested on the latest Ubuntu.
Publish changes to GitHub Pages:
git add -u
git commit -m 'make yourself look sillier'
./publish
Source: ./publish.
GitHub forces us to use the master branch for the build output... so the actual source is in the branch dev.
Update the gems with:
bundle update
git add Gemfile.lock
git commit -m 'update gems'
His website was originally written in markdown, however those were deprecated in favour of AsciiDoctor when Ciro saw the light, rationale shown at: markdown-style-guideuse-asciidoc
How to mine Monero Updated 2025-11-05
Ubuntu 20.10 as per xmrig.com/docs/miner/build/ubuntu:
sudo apt install git build-essential cmake libuv1-dev libssl-dev libhwloc-dev
git clone https://github.com/xmrig/xmrig.git
mkdir xmrig/build && cd xmrig/build
cmake ..
make -j$(nproc)
At minexmr.com/#getting_started we see that all you then need is a single CLI command:
xmrig -o pool.minexmr.com:4444 -u <your-monero-address>
Seems simple, well done devs!
Benchmark on Lenovo ThinkPad P51 (2017) as per xmrig.com/docs/miner/benchmark:
./xmrig --bench=1M
gives:
948.1 h/s
which according to the minexmr.com mining pool would generate 0.0005 XMR/day, which at the February 2021 rate of 140 USD/XMR is 0.07 USD/day. The minimum payout in that pool is 0.004 XMR so it would take 8 days to reach that.
So clearly, application-specific integrated circuit mining is the only viable way of doing this.
www.makeuseof.com/cryptos-you-can-mine-at-home/ is a completely full of bullshit article that says otherwise. How can someone publish that!
How to report Ubuntu crashes Updated 2025-07-16
Their crash system does not have an amazing user interface.
Tested on Ubuntu 21.10.
After something crashes, look under /var/crash for a crash file, which helps to determine which package to report under on Launchpad.
E.g. a file /var/crash/_usr_sbin_gdm3.0.crash makes you want to file the bug under gdm at: bugs.launchpad.net/ubuntu/+source/gdm/+filebug
Then, while reporting the bug, you want to give the developpers access to that .crash file. But you can't publicly upload it because it contains memory dumps and could contain secret information. The way to do it is to look at the ID under:
sudo cat /var/crash/_usr_sbin_gdm3.0.uploaded
Ubuntu's crash report system has already uploaded the .crash for you, so you just have to confirm it and give the ID on the ticket.
You can view a list of all your uploaded errors at:
xdg-open https://errors.ubuntu.com/user/$(sudo cat /var/lib/whoopsie/whoopsie-id)
and each of those contain a link to:
https://errors.ubuntu.com/oops/<.uloaded error id>
which you yourself cannot see.
Running:
sudo apport-unpack /var/crash/_usr_sbin_gdm3.0.crash /tmp/app
splits it up into a few files, but does not make any major improvements.
apport-retrace
sudo apt install apport-retrace
sudo chmod 666 /var/crash/_usr_sbin_gdm3.0.crash
apport-retrace -g /var/crash/_usr_sbin_gdm3.0.crash
opens GDB with the core dump. Debug symbols are supplied as separate packages, which is a really cool idea: so you should be able to download them after the crash to see symbols. askubuntu.com/questions/487222/how-to-install-debug-symbols-for-installed-packages mentions how to install them. Official docs at: wiki.ubuntu.com/DebuggingProgramCrash#Debug_Symbol_Packages
Tried:
echo "deb http://ddebs.ubuntu.com $(lsb_release -cs) main restricted universe multiverse" | sudo tee -a /etc/apt/sources.list.d/ddebs.list
echo -e "deb http://ddebs.ubuntu.com $(lsb_release -cs)-updates main restricted universe multiverse\ndeb http://ddebs.ubuntu.com $(lsb_release -cs)-proposed main restricted universe multiverse" | sudo tee -a /etc/apt/sources.list.d/ddebs.list
sudo apt install ubuntu-dbgsym-keyring
but then sudo apt update fails with:
E: The repository 'http://ddebs.ubuntu.com impish-security Release' does not have a Release file.
How to teach and learn physics Updated 2025-07-16
The approach many courses take to physics, specially "modern Physics" is really bad, this is how it should be taught:
This is likely because at some point, experiments get more and more complicated, and so people are tempted to say "this is the truth" instead of "this is why we think this is the truth", which is much harder.
But we can't be lazy, there is no replacement to the why.
Related:
There is only one thing that can truly motivate you to make good materials: becoming famous.
Strive for that. Make good materials. Publish them. Get good reviews. Loop.
This generates a virtuous loop, which makes you produce better and better material.

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