Ciro Santilli @cirosantilli 37

 Articles (11k) Discussions (27) Comments (65) Follows  Received likes Files

New Updated  Top  Announced  A-Z  Liked  Followed

GNU Debugger Updated 2025-07-16

Just add GDB Dashboard, and you're good to go.

 Read the full article

Micro Bit GPIO Updated 2025-07-16

Pinout overview: makecode.microbit.org/device/pins Basically 0, 1, and 2 are the truly generic ones. They can also serve as ADCs.

Micropython documentation: microbit-micropython.readthedocs.io/en/latest/pin.html

 Read the full article

Micro Bit simulator Updated 2025-07-16

 Read the full article

Netflix and chill Updated 2025-07-16

www.urbandictionary.com/define.php?term=Netflix%20and%20Chill

 Read the full article

On the Relative Motion of the Earth and the Luminiferous Ether Updated 2025-07-16

This paper is in the public domain and people have uploaded it e.g. to glorious Wikisource: en.wikisource.org/wiki/On_the_Relative_Motion_of_the_Earth_and_the_Luminiferous_Ether including its amazing illustrations.

Figure 1.
Fig 3 from On the Relative Motion of the Earth and the Luminiferous Ether
. Source. Amazing 3D technical drawing from the 19th century!!!

 Read the full article

Continuous problems are simpler than discrete ones Updated 2025-07-16

This is a general philosophy that Ciro Santilli, and likely others, observes over and over.

Basically, continuity, or higher order conditions like differentiability seem to impose greater constraints on problems, which make them more solvable.

Some good examples of that:

complex discrete problems:
- classification of finite groups
simple continuous problems:
- characterization of Lie groups

 Read the full article

Khronos Group Updated 2025-07-16

The fact that they kept the standard open source makes them huge heroes, see also: closed standard.

Shame that many (most?) of their proposals just die out.

 Read the full article

Quantum field theory lectures Updated 2025-07-16

 Read the full article

Discrete Fourier transform Updated 2025-07-16

Input: a sequence of

N

complex numbers

x_{k}

.

Output: another sequence of

N

complex numbers

X_{k}

such that:

x_{n} = \frac{1}{N} \sum_{k = 0}^{N - 1} X_{k} e^{i 2 π \frac{kn}{N}}

Intuitively, this means that we are braking up the complex signal into

N

sinusoidal frequencies:

$X_{0}$ : is kind of magic and ends up being a constant added to the signal because $e^{i 2 π \frac{kn}{N}} = e^{0} = 1$
$X_{1}$ : sinusoidal that completes one cycle over the signal. The larger the $N$ , the larger the resolution of that sinusoidal. But it completes one cycle regardless.
$X_{2}$ : sinusoidal that completes two cycles over the signal
...
$X_{N - 1}$ : sinusoidal that completes $N - 1$ cycles over the signal

and is the amplitude of each sine.

We use Zero-based numbering in our definitions because it just makes every formula simpler.

Motivation: similar to the Fourier transform:

compression: a sine would use N points in the time domain, but in the frequency domain just one, so we can throw the rest away. A sum of two sines, only two. So if your signal has periodicity, in general you can compress it with the transform
noise removal: many systems add noise only at certain frequencies, which are hopefully different from the main frequencies of the actual signal. By doing the transform, we can remove those frequencies to attain a better signal-to-noise

In particular, the discrete Fourier transform is used in signal processing after a analog-to-digital converter. Digital signal processing historically likely grew more and more over analog processing as digital processors got faster and faster as it gives more flexibility in algorithm design.

Sample software implementations:

numpy.fft, notably see the example: numpy/fft.py

Figure 1.
DFT of $2 sin (t) + cos (4 t)$ with 25 points
. This is a simple example of a discrete Fourier transform for a real input signal. It illustrates how the DFT takes N complex numbers as input, and produces N complex numbers as output. It also illustrates how the discrete Fourier transform of a real signal is symmetric around the center point.

 Read the full article

Flatpak Updated 2025-07-16

 Read the full article

Dizi (instrument) Updated 2025-07-16

Figure 1. Source.

Figure 2. Source.

 Read the full article

Django (web-framework) Updated 2025-07-16

React setups:

One problem with Django is that it does not expose its ORM as an external library: stackoverflow.com/questions/33170016/how-to-use-django-1-8-5-orm-without-creating-a-django-project which is wasteful of development time.

 Read the full article

DNA sequencing milestone Updated 2025-07-16

Most of these are going to be Whole-genome sequencing of some model organism:

1975 by Sanger et al.: 5 kbp of the single-stranded bacteriophage ΦX174 using Sanger's radiolabelling method
1981 by Sanger et al.: 17 kbp of human mitochondrial DNA via Sanger method, known as the Cambridge Reference Sequence
2003: Human Genome Project (3 Gbp)

en.wikipedia.org/wiki/Whole_genome_sequencing#History lists them all. Basically th big "firsts" all happened in the 1990s and early 2000s.

 Read the full article

Smartphone Updated 2025-07-16

 Read the full article

Structure of the mitochondria Updated 2025-07-16

 Read the full article

Cellular respiration Updated 2025-07-16

 Read the full article

diff Updated 2025-07-16

 Read the full article

Minkowski inner product Updated 2025-07-16

This form is not really an inner product in the common modern definition, because it is not positive definite, only a symmetric bilinear form.

 Read the full article

Mitochondrial DNA Updated 2025-07-16

 Read the full article

Mitochondrial endosymbiosis Updated 2025-07-16

Likely happened between an archaea and a bacteria.

 Read the full article

 There are unlisted articles, also show them or only show them.