Ciro Santilli @cirosantilli 40 

This is related to the underlying SVG pain point of SVG background color:

For PNG export:

superuser.com/questions/249860/how-can-i-change-inkscapes-default-export-background-color-from-yellow-to-white

Rotate object around a point in Inkscape Updated 2025-11-05

There's a tiny little crosshair that you can drag around to set the center of rotation.

And there's a button to make that crosshair snap: inkscape.org/forums/questions/can-a-pivotingtransfrom-crosshair-be-moved-and-made-to-snap-to-a-node-or-a-grid-point/#c14432

Inscription (blockchain) Updated 2025-11-18

Data that is inscribed in a blockchain as a way to perpetuate the data, rather than to follow the main intended purpose of the given blockchain, e.g. ASCII art instead of financial transactions on the Bitcoin blockchain.

A catalogue for Bitcoin can be found at: Section "Cool data embedded in the Bitcoin blockchain".

Ciro Santilli's hardware / Internet speed Updated 2025-11-18

Home 2017 TalkTalk 38Mbps nominal, Google M-lab speed test:

36.4 Mbps download
9.15 Mbps up
58 ms latency over 80km of first world

Home 2025 Giffgaff

Home 2025 Sky Broadband WiFi Max Hub SR213 (SR213-02-UK-wht) 1GBPS:

Lenovo ThinkPad P14s gen4 amd
- wired to fiber box:
- wireless sitting next to router:
Google Pixel 7a
- wireless sitting next to router: 414 down 107 up. Receiver bound which is funny.

Admin at 192.168.0.1/ username admin password same as wifi password.

Navier-Stokes existence and smoothness Updated 2025-12-25

On December 19, 2025 a bet was revealed between two DeepMind guys that one of them would have a Lean proof to the problem:

A report on the Navier-Stokes Problem by Vladimir Šverak

. Source. 2025.

List of subtitle file formats Updated 2025-11-18

Fluid mechanics Updated 2025-10-27

Boooooring. Except for Navier-Stokes existence and smoothness. That's OK.

The eye in Ciro Santilli's website banner Updated 2025-11-18

Synthetic virus Updated 2025-11-18

Man-made virus!

TODO: if we had cheap de novo DNA synthesis, how hard would it be to bootstrap a virus culture from that? github.com/cirosantilli/cirosantilli.github.io/issues/60

Is it easy to transfect a cell with the synthesized DNA, and get it to generate full infectious viral particles?

If so, then de novo DNA synthesis would be very similar to 3D printed guns: en.wikipedia.org/wiki/3D_printed_firearms.

It might already be possible to order dissimulated sequences online:

www.theguardian.com/world/2006/jun/14/terrorism.topstories3

Asian fetish Updated 2025-10-27

en.wikipedia.org/wiki/Asian_fetish#History_of_origins

All interests are based on fetishes.

The fetish of beauty. The fetish if intelligence. The fetish of kindness.

What's wrong with the fetish of Asianess?

Whenever Ciro's wife starts with "the Asian fetish talk", Ciro reminds her of her own claimed "tall person fetish", and they call it quits.

Asian fetish is much more than sex. It is about the culture, the history, the language. It is the same fetish that makes great mathematicians an Artists do what they do.

When Ciro Santilli was at École Polytechnique, he had to do a presentation for his stupid English courses that all students were forced to take, no matter how good their English was.

The topic was likely something like "pick a country", and Ciro was delighted when he managed to pick "China", after it had gone around a table with many many people before him.

The PowerPoint presentation Ciro made over the weekend was so amazing (and making it was actually fun to make, Ciro actually remembers it a bit!), drawing partly from stuff his wife then girlfriend showed him, that at the end the one of the other students asked him if he had lived in China.

It is a shame Ciro couldn't find the presentation when he wrote this line many many years later. Anything that is not in a BLOB-free monorepo, will disappear, heed my words. But he's certain about two things which it contained:

In the United States, women of East and Southeast Asian descent are sometimes stereotyped as subservient, passive, mysterious, villainous in nature, and hyper-sexual.

subservient, passive, mysterious are understandable. But Hyper-sexual and villainous? OMG have these people never seen real Asians?
en.wikipedia.org/wiki/Asian_fetish#Pornography:

Several studies have implied that Asian women are over-represented in the American pornography industry. Asian women make up perhaps 20% of all female performers, despite being roughly 2.5% of the U.S. population. Asian men also appear to be considerably over-represented, at 10% of male actors.

How my boyfriend CHEATED with another Asian girl by Jenny Tian

. Source.

Video 2.

Sam Rockwell monologue about being an Asian girl on The White Lotus

. Source.

ZynAddSubFX Updated 2025-07-16

askubuntu.com/questions/220802/no-sound-zynaddsubfx-and-jack-wont-run/1297988#1297988

Contains a large database of instruments, and allows you to edit them. This is a fun toy.

Instruments are edited on a GUI. It is a multi-window program, and you open new windows from new windows from new windows, all filled with hundreds of virtual knobs that you drag with your keyboard, and which would be better done from textual software like Csound. It is a thing of beauty.

It does not seem possible to program arbitrary modular synthesizer circuits therefore. But if you understand additive synthesis and subtractive synthesis well, you can make some funky sounds with it.

It is basically a superset of all popular hardware synthesizers ever made.

Has its own built-in MIDI keyboard which is nice.

On Ubuntu 20.04 Version: 3.0.5:

sudo apt install zynaddsubfx
zynaddsubfx -O alsa

as per askubuntu.com/questions/220802/no-sound-zynaddsubfx-and-jack-wont-run/1297988#1297988
To do anything of interest, switch to the Advanced UI:

Misc
Switch Interface Mode

The UI is completely different form what is shown on the website as of 2020: zynaddsubfx.sourceforge.io/, it looks instead like: www.youtube.com/watch?v=iVPr6iUuO3g Maybe on the website it is the new zyn-fusion UI... www.reddit.com/r/linuxaudio/comments/bxn3ur/some_help_for_installing_zynfusion_zynaddsubfx/ so confusing.

And they have some crappy policy of asking for 45 USD for binary downloads.

Compiling from source:

git clone https://github.com/zynaddsubfx/zynaddsubfx
cd zynaddsubfx
git checkout a789866de4d45a784c1f4d95fcf5a1938347baef
sudo apt build-dep zynaddsubfx
mkdir build
cd build
cmake ..
make -j`nproc`

fails with:

Traceback (most recent call last):
  File "/usr/bin/cxxtestgen", line 7, in <module>
    import cxxtest.cxxtestgen
  File "/usr/share/cxxtest/cxxtest/__init__.py", line 33, in <module>
    from cxxtest.cxxtestgen import *
  File "/usr/share/cxxtest/cxxtest/cxxtestgen.py", line 18, in <module>
    import __release__
ModuleNotFoundError: No module named '__release__'

Ciro gives up for now.

ZX-calculus Updated 2025-07-16

As en.wikipedia.org/w/index.php?title=ZX-calculus&oldid=1071329204#Diagram_rewriting tries to explain but fails to deliver as usual consider the GHZ state represented as a quantum circuit.

How can we easily prove that that quantum circuit equals the state:

\frac{∣000 > + ∣111 >}{2}

(1)

The naive way would be to just do the matrix multiplication as explained at Section "Quantum computing is just matrix multiplication".

However, ZX-calculus provides a simpler way.

And even more importantly, sometimes it is the only way, because in a real circuit, we would not be able to do the matrix multiplication

What we do in ZX-calculus is we first transform the original quantum circuit into a ZX graph.

This is always possible, because we can describe how to do the conversion simply for any of the Clifford plus T gates, which is a set of universal quantum gates.

Then, after we do this transformation, we can start applying further transformations that simplify the circuit.

It has already been proven that there is no efficient algorithm for this (TODO source, someone said P-sharp complete best case)

But it has been proven in 2017 that any possible equivalence between quantum circuits can be reached by modifying ZX-calculus circuits.

There are only 7 transformation rules that we need, and all others can be derived from those, universality.

So, we can apply those rules to do the transformation shown in Wikipedia:

Figure 1.
GHZ circuit as ZX-diagram
. Source.

and one of those rules finally tells us that that last graph means our desired state:

\frac{∣000 > + ∣111 >}{2}

(2)

because it is a Z spider with

m = 3

and

n = 1

Working with PyZX by Aleks Kissinger (2019)

Source. This video appears to give amazing motivation on why you should care about ZX-calculus, it mentions

Bibliography:

Year 4 of the physics course of the University of Oxford Updated 2025-07-16

Students choose only one of the Cx courses.

Then there are PhDs corresponding to each of them: www.ox.ac.uk/admissions/graduate/courses/mpls/physics

Yang-Mills existence and mass gap Updated 2025-07-16

www.youtube.com/watch?v=-_qNKbwM_eE Unsolved: Yang-Mills existence and mass gap by J Knudsen (2019). Gives 10 key points, but the truly hard ones are too quick. He knows the thing though.

Yang-Mills 1 by David Metzler (2011)

Source.

Playlist: www.youtube.com/watch?v=j3fsPHnrgLg&list=PL613A31A706529585&index=13

A bit disappointing, too high level, with very few nuggests that are not Googleable withing 5 minutes.

Breakdown:

1 www.youtube.com/watch?v=j3fsPHnrgLg: too basic
2 www.youtube.com/watch?v=br6OxCLyqAI?t=569: mentions groups of Lie type in the context of classification of finite simple groups. Each group has a little diagram.
3 youtu.be/1baiIxKKQlQ?list=PL613A31A706529585&t=728 the original example of a local symmetry was general relativity, and that in that context it can be clearly seen that the local symmetry is what causes "forces" to appear
- youtu.be/1baiIxKKQlQ?list=PL613A31A706529585&t=933 local symmetry gives a conserved current. In the case of electromagnetism, this is electrical current. This was the only worthwhile thing he sad to 2021 Ciro. Summarized at: local symmetries of the Lagrangian imply conserved currents.
4 youtu.be/5ljKcWm7hoU?list=PL613A31A706529585&t=427 electromagnetism has both a global symmetry (special relativity) but also local symmetry, which leads to the conservation of charge current and forces.
lecture 3 properly defines a local symmetry in terms of the context of the lagrangian density, and explains that the conservation of currents there is basically the statement of Noether's theorem in that context.

Video 2.

Millennium Prize Problem: Yang Mills Theory by David Gross (2018)

Source. 2 hour talk at the Kavli Institute for Theoretical Physics. Too mathematical, 2021 Ciro can't make much out of it.

Video 3.

Lorenzo Sadun on the "Yang-Mills and Mass Gap" Millennium problem

. Source. Unknown year. He almost gets there, he's good. Just needed to be a little bit deeper.

Xah Lee Updated 2025-07-16

fuseki.net/home/List-of-Patreon-Subs-with-Justification.html describes him well:

Outsider, formerly homeless, extreme person interested in CS and culture. Self-publishes a website with thousands of tutorial / opinion pages. Possibly similar to Sam Sloan - extremely productive, wide interests, obsessive, and pretty disagreeable.

Homepage xahlee.org/ says:

Siphon my knowledge into your brain. Assimilate my sensibilities to your spine.

Nice Second brain vibe.

Figure 1.
Xah Lee with some weird statuettes of himself
. Source. 2019.

Let's see:

LinkedIn: www.linkedin.com/in/xahlee/
youtu.be/a6J62TwOreY?t=271 OMG he also uses a Kinesis Advantage 2 keyboard-like keyboard! Maybe there is something here after all.
he's also a mad tutorial writer: xahlee.info/Wallpaper_dir/c4_Derivation.html#gc2.2.2.1 like Ciro's Stack Overflow
www.patreon.com/xahlee £835.2/month from ony 27 members as of 2023, holy crap not bad!
he was in a bad spot as of 2014: xahlee.info/emacs/misc/xah_as_good_as_dead.html
i live on $3 per day for food in past 3 years. Eating noodles and oats with salt
Thread: www.reddit.com/r/programming/comments/25pypq/im_about_as_good_as_dead_the_end_of_xah_lee/
One is reminded of Chill and eat your bread in peace and Quote "Omar Khayyam's chill out quote". xahlee.org/PageTwo_dir/Personal_dir/xah.html autobiography is also of interest.

x86 Paging Tutorial / Multiple addresses translate to a single physical address Updated 2025-07-16

The same linear address can translate to different physical addresses for different processes, depending only on the value inside cr3.

Both linear addresses 00002 000 from process 1 and 00004 000 from process 2 point to the same physical address 00003 000. This is completely allowed by the hardware, and it is up to the operating system to handle such cases.

This often in normal operation because of Copy-on-write (COW), which be explained elsewhere.

Such mappings are sometime called "aliases".

x86 Paging Tutorial / Linux kernel usage Updated 2025-07-16

The Linux kernel makes extensive usage of the paging features of x86 to allow fast process switches with small data fragmentation.

There are also however some features that the Linux kernel might not use, either because they are only for backwards compatibility, or because the Linux devs didn't feel it was worth it yet.

x86 Paging Tutorial / How the K-ary tree is used in x86 Updated 2025-07-16

x86's multi-level paging scheme uses a 2 level K-ary tree with 2^10 bits on each level.

Addresses are now split as:

| directory (10 bits) | table (10 bits) | offset (12 bits) |

Then:

the top 10 bits are used to walk the top level of the K-ary tree (level0)
The top table is called a "directory of page tables".
cr3 now points to the location on RAM of the page directory of the current process instead of page tables.
Page directory entries are very similar to page table entries except that they point to the physical addresses of page tables instead of physical addresses of pages.
Each directory entry also takes up 4 bytes, just like page entries, so that makes 4 KiB per process minimum.
Page directory entries also contain a valid flag: if invalid, the OS does not allocate a page table for that entry, and saves memory.
Each process has one and only one page directory associated to it (and pointed to by cr3), so it will contain at least 2^10 = 1K page directory entries, much better than the minimum 1M entries required on a single-level scheme.
the next 10 bits are used to walk the second level of the K-ary tree (level1)
Second level entries are also called page tables like the single level scheme.
Page tables are only allocated only as needed by the OS.
Each page table has only 2^10 = 1K page table entries instead of 2^20 for the single paging scheme.
Each process can now have up to 2^10 page tables instead of 2^20 for the single paging scheme.
the offset is again not used for translation, it only gives the offset within a page

One reason for using 10 bits on the first two levels (and not, say, 12 | 8 | 12 ) is that each Page Table entry is 4 bytes long. Then the 2^10 entries of Page directories and Page Tables will fit nicely into 4Kb pages. This means that it faster and simpler to allocate and deallocate pages for that purpose.

x86 Paging Tutorial / CAM Updated 2025-07-16

Using the TLB makes translation faster, because the initial translation takes one access per TLB level, which means 2 on a simple 32 bit scheme, but 3 or 4 on 64 bit architectures.

The TLB is usually implemented as an expensive type of RAM called content-addressable memory (CAM). CAM implements an associative map on hardware, that is, a structure that given a key (linear address), retrieves a value.

Mappings could also be implemented on RAM addresses, but CAM mappings may required much less entries than a RAM mapping.

For example, a map in which:

both keys and values have 20 bits (the case of a simple paging schemes)
at most 4 values need to be stored at each time

could be stored in a TLB with 4 entries:

linear  physical
------  --------
00000   00001
00001   00010
00010   00011
FFFFF   00000

However, to implement this with RAM, it would be necessary to have 2^20 addresses:

linear  physical
------  --------
00000   00001
00001   00010
00010   00011
... (from 00011 to FFFFE)
FFFFF   00000

which would be even more expensive than using a TLB.

Erdős number Updated 2025-10-27