Ciro Santilli (@cirosantilli) - New articles

AC adapter Updated 2025-07-16

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AKS primality test Updated 2025-07-16

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Internet privacy organizations Updated 2025-07-16

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Udacity Updated 2025-07-16

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It is a shame that they refocused to more applied courses. This also highlights their highly "managed" approach to content creation. Their 2022 pitch on front page says it all:

for as few as 10 hours a week, you can get the in-demand skills you need to help land a high-paying tech job

they are focused on the highly paid character of many software engineering jobs.

But one cool point of this website is how they hire tutors to help on the courses. This is a very good thing. It is a fair way of monetizing: e-learning websites must keep content free, only charge for certification.

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x86 Paging Tutorial / TLB replacement policy Updated 2025-07-16

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When TLB is filled up, older addresses are overwritten. Just like CPU cache, the replacement policy is a potentially complex operation, but a simple and reasonable heuristic is to remove the least recently used entry (LRU).

With LRU, starting from state:

  valid  linear  physical
  -----  ------  --------
> 1      00003   00005
  1      00007   00009
  1      00009   00001
  1      0000B   00003

adding 0000D -> 0000A would give:

  valid  linear  physical
  -----  ------  --------
  1      0000D   0000A
> 1      00007   00009
  1      00009   00001
  1      0000B   00003

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Allegory Updated 2025-07-16

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Electrolysis Updated 2025-07-16

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Open instant messaging protocols Updated 2025-07-16

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Internet Relay Chat vs XMPP: stackoverflow.com/questions/4149380/whats-the-best-open-protocol-for-chat-room-software

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Weekend Updated 2025-07-16

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Days of the week where you don't do what you set out to do. And yet, it is in those days that you save your sanity, and possibly the world. Wait, this sounds exactly like a week day?

Figure 1.
Calvin and Hobbes "Oh No! I overslept! I gotta get up!" cartoon
. Source.

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XP School Updated 2025-07-16

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www.thetimes.co.uk/article/no-uniforms-no-detentions-no-maths-lessons-is-xp-in-doncaster-the-school-of-the-future-jnc6n80kq

Amazing self-directed learning direction:

The pupils have a parents' evening coming up but instead of their teachers giving an account of their progress, it is a "student-led conference" at which they must present a portfolio of their work, explain what they are most proud of and discuss where they need to put in more effort.

world.hey.com/gwyn/no-excuses-bc4152fb mentions that the founder was inspired by other schools: High Tech High and Expeditionary Learning.

Lots of focus on showcase student work.

The founder Gwyn ap Harri is quite dirty mouthed, which is also cool.

Ciro Santilli tried to contact them in 2021 at: twitter.com/cirosantilli/status/1448924419016036353 and on website contact form to see if we could do some project together, but no reply.

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Academia is broken Updated 2025-07-16

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Sometimes Ciro Santilli regrets not having done a PhD. But this section makes him feel better about himself. To be fair, part of the merit is on him, part of the reason he didn't move on was the strong odour of bullshit oozing down to Masters level. A good PhH might have opened interesting job opportunities however, given that you don't really learn anything useful before that point in your education.

twitter.com/togelius/status/1584611702691483648:

The "real world" is full of people who couldn't make it in academia.

Video 1.

I failed in academia by Andy Stapleton (2021)

Source.

publish or perish

Video 2.

6 Dirty Tactics Found In Academia & Universities by Andy Stapleton (2022)

Source.

Video 3.

Rise to the Top: The Habits and Mindset of Top 0.1% PhD Students by Andy Stapleton (2023)

. Source.

Figure 1.
Profzi scheme by PhD Comics
.
A Ponzi scheme that trains people in new skills is not necessarily a terrible thing. It is a somewhat more useful version than standard exam based education.
Perhaps the problem is "forcing" 35 year olds to go down that path when they might also want to have boring stuff like families and security.
If people could get to the PhD level much, much sooner, it wouldn't be as obscene: Section "Students must be allowed to progress as fast as they want".

Video 4.

The broken system at the heart of Academia by Peter Judo (2023)

. Source.

Video 5.

My dream died, and now I'm here by Sabine Hossenfelder (2024)

. Source.

Video 6.

I left academia. Here's why. by Jared Henderson

. Source.

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List of instant messaging software Updated 2025-07-16

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Physics World Updated 2025-07-16

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Magazine of the Institute of Physics.

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Robert Noyce Updated 2025-07-16

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Academic publishing Updated 2025-07-16

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Closed access academic journals are evil.

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AC Josephson effect Updated 2025-07-16

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This is what happens when you apply a DC voltage across a Josephson junction.

It is called "AC effect" because when we apply a DC voltage, it produces an alternating current on the device.

By looking at the Josephson equations, we see that

V (t) = k

a positive constant, then

φ

just increases linearly without bound.

Therefore, from the first equation:

I (t) = I_{c} sin (φ (t))

(1)

we see that the current will just vary sinusoidally between

\pm I_{c}

.

This meas that we can use a Josephson junction as a perfect voltage to frequency converter.

Wikipedia mentions that this frequency is

484 G Hz / mV

, so it is very very high, so we are not able to view individual points of the sine curve separately with our instruments.

Also it is likely not going to be very useful for many practical applications in this mode.

An I-V curve can also be seen at: Figure "Electron microscope image of a Josephson junction its I-V curve".

Figure 1.
I-V curve of the AC Josephson effect
. Source.
Voltage is horizontal, current vertical. The vertical bar in the middle is the effect of interest: the current is going up and down very quickly between $\pm I_{c}$ , the Josephson current of the device. Because it is too quick for the oscilloscope, we just see a solid vertical bar.
The non vertical curves at right and left are just other effects we are not interested in.
TODO what does it mean that there is no line at all near the central vertical line? What happens at those voltages?

Video 1.

Superconducting Transition of Josephson junction by Christina Wicker (2016)

Source. Amazing video that presumably shows the screen of a digital oscilloscope doing a voltage sweep as temperature is reduced and superconductivity is reached.

Figure 2.
I-V curve of a superconducting tunnel junction
. So it appears that there is a zero current between $V = 0$ and $V = 2Δ/ e$ . Why doesn't it show up on the oscilloscope sweeps, e.g. Video 1. "Superconducting Transition of Josephson junction by Christina Wicker (2016)"?

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Animal intelligence Updated 2025-07-16

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São Paulo (state) Updated 2025-07-16

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activatedgeek/LeNet-5 Updated 2025-07-16

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github.com/activatedgeek/LeNet-5

This repository contains a very clean minimal PyTorch implementation of LeNet-5 for MNIST.

It trains the LeNet-5 neural network on the MNIST dataset from scratch, and afterwards you can give it newly hand-written digits 0 to 9 and it will hopefully recognize the digit for you.

Ciro Santilli created a small fork of this repo at lenet adding better automation for:

extracting MNIST images as PNG
ONNX CLI inference taking any image files as input
a Python tkinter GUI that lets you draw and see inference live
running on GPU

Install on Ubuntu 24.10 with:

sudo apt install protobuf-compiler
git clone https://github.com/activatedgeek/LeNet-5
cd LeNet-5
git checkout 95b55a838f9d90536fd3b303cede12cf8b5da47f
virtualenv -p python3 .venv
. .venv/bin/activate
pip install \
  Pillow==6.2.0 \
  numpy==1.24.2 \
  onnx==1.13.1 \
  torch==2.0.0 \
  torchvision==0.15.1 \
  visdom==0.2.4 \
;

We use our own pip install because their requirements.txt uses >= instead of == making it random if things will work or not.

On Ubuntu 22.10 it was instead:

pip install
  Pillow==6.2.0 \
  numpy==1.26.4 \
  onnx==1.17.0 torch==2.6.0 \
  torchvision==0.21.0 \
  visdom==0.2.4 \
;

Then run with:

python run.py

This script:

does a fixed 15 epochs on the training data
it then uses the trained net from memory to check accuracy with the test data
then it also produces a lenet.onnx ONNX file which contains the trained network, nice!

It throws a billion exceptions because we didn't start the Visdom server, but everything works nevertheless, we just don't get a visualization of the training.

The terminal outputs lines such as:

Train - Epoch 1, Batch: 0, Loss: 2.311587
Train - Epoch 1, Batch: 10, Loss: 2.067062
Train - Epoch 1, Batch: 20, Loss: 0.959845
...
Train - Epoch 1, Batch: 230, Loss: 0.071796
Test Avg. Loss: 0.000112, Accuracy: 0.967500
...
Train - Epoch 15, Batch: 230, Loss: 0.010040
Test Avg. Loss: 0.000038, Accuracy: 0.989300

And the runtime on Ubuntu 22.10, P51 was:

real    2m10.262s
user    11m9.771s
sys     0m26.368s

One of the benefits of the ONNX output is that we can nicely visualize the neural network on Netron:

Figure 1.
Netron visualization of the activatedgeek/LeNet-5 ONNX output
. From this we can see the bifurcation on the computational graph as done in the code at:
`output = self.c1(img) x = self.c2_1(output) output = self.c2_2(output) output += x output = self.c3(output)`
This doesn't seem to conform to the original LeNet-5 however?

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Amazon Web Services Updated 2025-07-16

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Ciro Santilli @cirosantilli 37