Ciro Santilli @cirosantilli 37

 +---+---+---+---+---+---+---+---+
 | r | n | b | q | k | b | n | r | 8
 +---+---+---+---+---+---+---+---+
 | p | p | p | p | p | p | p | p | 7
 +---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   | 6
 +---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   | 5
 +---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   | 4
 +---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   | 3
 +---+---+---+---+---+---+---+---+
 | P | P | P | P | P | P | P | P | 2
 +---+---+---+---+---+---+---+---+
 | R | N | B | Q | K | B | N | R | 1
 +---+---+---+---+---+---+---+---+
   a   b   c   d   e   f   g   h

Fen: rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1
Key: 8F8F01D4562F59FB

Sweet ASCII art. where:

Fen: FEN notation
Key: TODO

Move white king's pawn from e2 to e4:

position startpos moves e2e4

Then display again:

gives:

 +---+---+---+---+---+---+---+---+
 | r | n | b | q | k | b | n | r | 8
 +---+---+---+---+---+---+---+---+
 | p | p | p | p | p | p | p | p | 7
 +---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   | 6
 +---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   | 5
 +---+---+---+---+---+---+---+---+
 |   |   |   |   | P |   |   |   | 4
 +---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   | 3
 +---+---+---+---+---+---+---+---+
 | P | P | P | P |   | P | P | P | 2
 +---+---+---+---+---+---+---+---+
 | R | N | B | Q | K | B | N | R | 1
 +---+---+---+---+---+---+---+---+
   a   b   c   d   e   f   g   h

Fen: rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq - 0 1
Key: B46022469E3DD31B

so we see that the pawn moved.

Now let's make Stockfish think for one second what is the next best move for black:

go movetime 1000

gives as the last line:

bestmove c7c5 ponder g1f3

TODO:

what is ponder? Something to do with thinking on the opponent's turn: permanent brain.
understand the previous lines

To make the move it as suggested for black, we have to either repeat the entire sequence of movements:

position startpos moves e2e4 c7c5

d:

 +---+---+---+---+---+---+---+---+
 | r | n | b | q | k | b | n | r | 8
 +---+---+---+---+---+---+---+---+
 | p | p |   | p | p | p | p | p | 7
 +---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   | 6
 +---+---+---+---+---+---+---+---+
 |   |   | p |   |   |   |   |   | 5
 +---+---+---+---+---+---+---+---+
 |   |   |   |   | P |   |   |   | 4
 +---+---+---+---+---+---+---+---+
 |   |   |   |   |   |   |   |   | 3
 +---+---+---+---+---+---+---+---+
 | P | P | P | P |   | P | P | P | 2
 +---+---+---+---+---+---+---+---+
 | R | N | B | Q | K | B | N | R | 1
 +---+---+---+---+---+---+---+---+
   a   b   c   d   e   f   g   h

Fen: rnbqkbnr/pp1ppppp/8/2p5/4P3/8/PPPP1PPP/RNBQKBNR w KQkq - 0 2
Key: 4CA78BCE9C2980B0

or alternatively we could also use the previous FEN notation as a starting point;

position fen rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq - 0 1 moves c7c5

Note how the Universal Chess Interface interface is very simple: we just load a state and then decide what to do next for that one state. The engine holds only one and exactly one state at a time, and you can't even modify it differentially without loading new one from scratch.

Let's move white again with our brain with either:

position startpos moves e2e4 c7c5 d2d3
position fen rnbqkbnr/pp1ppppp/8/2p5/4P3/8/PPPP1PPP/RNBQKBNR w KQkq - 0 2 moves d2d3

Set a specific position from fen:

position fen rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq - 0 1

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Strange Tales from a Chinese Studio Updated 2025-07-16

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Big collection of a bunch of ghost stories. 90% of them involve some dude dating a beautiful ghost woman or animal that can shapeshift as a woman.

Organized into 12 chapeters as seen on the Chinese wiki: zh.wikipedia.org/wiki/聊齋志異#章節

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Central dogma of molecular biology Updated 2025-07-16

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Computer science masters course of the University of Oxford Updated 2025-07-16

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Concurrent programming course of the University of Oxford Updated 2025-07-16

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Strategy game Updated 2025-07-16

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vmpk Updated 2025-07-16

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vmpk.sourceforge.io/

Opens a virtual MIDI piano GUI. It just works on Ubuntu 20.04: askubuntu.com/questions/34391/virtual-midi-piano-keyboard-setup/1298026#1298026

VMPK is a virtual device that replicates what you would get by connecting a physical MIDI keyboard to your computer. It is not a software synthesizer on its own. But it does connect to a working synthesizer by default (Sonivox EAS) which makes it produce sounds out-of-the box.

TODO: then I messed with my sound settings, and then it stopped working by default on the default "MIDI Connection" > "MIDI Out Driver" > "Network". But it still works on "SonivoxEAS".

A hello world of actually connecting it to a specific software synthesizer manually on Advanced Linux Sound Architecture with aconnect can be found at: askubuntu.com/questions/34391/virtual-midi-piano-keyboard-setup/1298026#1298026

Save to a MIDI file: askubuntu.com/questions/709673/save-as-midi-when-playing-from-vmpk-qsynth/1298231#1298231

Reasonable default key mappings to keyboard covering 2 octaves.

3 multiple simultaneous keys did not work (tested "ZQI"). This might just be a limitation of my keyboard however.

TODO how to save to a .mid file? askubuntu.com/questions/709673/save-as-midi-when-playing-from-vmpk-qsynth

SourceForge.

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If a product of a big company has a catchy name it came from an acquisition Updated 2025-07-16

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If a Big Company makes a product that Does Something, they just call it Big Company Does Something.

If a product is called "Big Company Catchy Name Does Something", then it came from an acquisition, and they wanted to keep the name due to its prestige and to not confuse users.

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Open source video game asset Updated 2025-07-16

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Power engineering Updated 2025-07-16

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Applications of power, we have to remember it is there to notice how awesome it is!

lightning
motors
sending nad receiving communication signals
computers, which in turn can do computations and improved communication

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Probability Updated 2025-07-16

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Algebra Updated 2025-07-16

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Not to be confused with algebra over a field, which is a particular algebraic structure studied within algebra.

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Connect two computers directly without a router with an Ethernet cable Updated 2025-07-16

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For IP-level communication, askubuntu.com/questions/22835/how-to-network-two-ubuntu-computers-using-ethernet-without-a-router/116680#116680 just worked between P51 and P14s both on Ubuntu 23.10 connected with a regular Cat 5e cable.

On both machines, first we found the Ethernet cable interface name with the ip CLI tool:

ip a

which outputs on the P41s:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: enp1s0f0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether fc:5c:ee:24:fb:b4 brd ff:ff:ff:ff:ff:ff
3: wlp2s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 04:7b:cb:cc:1b:10 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.123/24 brd 192.168.1.255 scope global dynamic noprefixroute wlp2s0
       valid_lft 61284sec preferred_lft 61284sec
    inet6 fe80::3597:15d8:74ff:e112/64 scope link noprefixroute
       valid_lft forever preferred_lft forever

so the interface was enp1s0f0, because wlp is wireless and lo is localhost.

So on the P14s we assign an IP of 10.0.0.10 to the P51:

sudo ip address add 10.0.0.10/24 dev enp1s0f0

Then on the P51 analogously, giving IP of 10.0.0.20 to the P14s:

sudo ip address add 10.0.0.20/24 dev enp0s31f6

And after that, P14s can:

ping 10.0.0.10

and P51 can:

ping 10.0.0.20

TODO after a few seconds, the settings appear to be forgotten, and ping stops working unless you do sudo ip address add on the local machine again. This seems to happen after a popup appears saying "Activation of network connection failed" as it fails to obtain Internet from the cable.

TODO list and delete such manual assignments we've made.

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The beauty of mathematics Updated 2025-07-16

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Ciro Santilli intends to move his beauty list here little by little: github.com/cirosantilli/mathematics/blob/master/beauty.md

The most beautiful things in mathematics are results that are:

simple to state but hard to prove:
- Fermat's Last Theorem
- number of unknown rationality, e.g. is $e + π$ rational?
- transcendental number conjectures, e.g. is $e + π$ transcendental?
- basically any conjecture involving prime numbers:
  - twin prime conjecture
- many combinatorial game questions, e.g.:
  - first-move advantage in chess
surprising results: we had intuitive reasons to believe something as possible or not, but a theorem shatters that conviction and brings us on our knees, sometimes via pathological counter-examples. General surprise themes include:
- classification of potentially infinite sets like: compact manifolds, etc.
  - classification of finite simple groups
  - classification of regular polytopes
  - classification of closed surfaces, and more generalized Poincaré conjectures
  - classification of wallpaper groups and space groups
- problems that are more complicated in low dimensions than high like:
  - generalized Poincaré conjectures. It is also fun to see how in many cases complexity peaks out at 4 dimensions.
  - classification of regular polytopes
- unpredictable magic constants:
  - why is the lowest dimension for an exotic sphere 7?
  - why is 4 the largest degree of an equation with explicit solution? Abel-Ruffini theorem
- undecidable problems, especially simple to state ones:
  - mortal matrix problem
  - sharp frontiers between solvable and unsolvable are also cool:
    attempts at determining specific values of the Busy beaver function for Turing machines with a given number of states and symbols
    related to Diophantine equations:
    decidability of Hilbert's tenth problem of a given degree and number of variables
    Hilbert's tenth problem over other rings
Lists:
- math.stackexchange.com/questions/139699/what-are-some-examples-of-a-mathematical-result-being-counterintuitive
- math.stackexchange.com/questions/2040811/what-are-some-counter-intuitive-results-in-mathematics-that-involve-only-finite/2055458#2055458
applications: make life easier and/or modeling some phenomena well, e.g. in physics. See also: explain how to make money with the lesson

Good lists of such problems Lists of mathematical problems.

Whenever Ciro Santilli learns a bit of mathematics, he always wonders to himself:

Am I achieving insight, or am I just memorizing definitions?

Unfortunately, due to how man books are written, it is not really possible to reach insight without first doing a bit of memorization. The better the book, the more insight is spread out, and less you have to learn before reaching each insight.

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Voltage transformer Updated 2025-07-16

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Waring-Goldbach problem Updated 2025-07-16

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It is exactly what you'd expect from the name, Waring was watching Netflix with Goldbach, when they suddenly came up with this.

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Water Updated 2025-07-16

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"Water" is the name for both: