Ciro Santilli @cirosantilli 37

 Articles (11k) Discussions (26) Comments (64) Follows  Received likes Files

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

Ciro's nc HTTP test server Updated 2025-07-16

As per stackoverflow.com/a/52351480/895245 our standard test setup is:

while true; do
  resp=$"$(date): hello\n"
  len="$(printf '%s' "$resp" | wc -c)"
  printf "HTTP/1.1 200 OK\r\nContent-Length: $len\r\n\r\n${resp}\n" | nc -Nl 8000
done

 Read the full article

Cirq Updated 2025-07-16

 Read the full article

Cisco Updated 2025-07-16

Nerds 2.0.1 excerpt about Cisco (1998)

youtu.be/mhz24AR3nIc?t=45 the founders both worked at Stanford University but because they were in different departments they couldn't send an email to one another.
youtu.be/mhz24AR3nIc?t=54 Sandy Lerner is very nice and chilled. She says how she was amazed by Leonard's manners!
youtu.be/mhz24AR3nIc?t=86 "sincerity begins at a little over 100 hours a week". The dude is a robot.
youtu.be/mhz24AR3nIc?t=279 earthquake!!!
youtu.be/d0ya8DggDYs?list=PLn7AqqWS1I_9EHEHy6sw-v6hUMhbeOTRW&t=3268 she bought a manor house, probably in Chawton Hampshire, England, possibly Chawton House
youtu.be/d0ya8DggDYs?list=PLn7AqqWS1I_9EHEHy6sw-v6hUMhbeOTRW&t=3312 he started donating to search for extraterrestrial intelligence

 Read the full article

Closed source offline software used by millions Updated 2025-07-16

Closed source on offline products used by millions of people is evil, when you could just have those for free with open source software! Thus Ciro's hatred for Microsoft Windows and MacOS (at least userland, maybe).

 Read the full article

Closing questions as off-topic Updated 2025-07-16

There's no point.

The question remains there, but people lose the ability to help the asker.

Reputation is meaningless regardless, since JavaScript gurus will always have 1000x more readers than low level junkies.

The deeper problem: the existence of multiple separate websites instead of just using the tags on a single website.

Examples:

 Read the full article

Cloud chamber Updated 2025-07-16

Figure 1.
Radium 226 source in a cloud chamber
. Source.

How to make a cloud chamber by Suzie Sheehy (2011)

 Read the full article

Cloud computing market share Updated 2025-07-16

 Read the full article

Cloud computing platform Updated 2025-07-16

 Read the full article

CNN convolution kernels are also learnt Updated 2025-07-16

CNN convolution kernels are not hardcoded. They are learnt and optimized via backpropagation. You just specify their size! Example in PyTorch you'd do just:

nn.Conv2d(1, 6, kernel_size=(5, 5))

as used for example at: activatedgeek/LeNet-5.

This can also be inferred from: stackoverflow.com/questions/55594969/how-to-visualise-filters-in-a-cnn-with-pytorch where we see that the kernels are not perfectly regular as you'd expected from something hand coded.

 Read the full article

CNOT gate Updated 2025-07-16

The CNOT gate is a controlled quantum gate that operates on two qubits, flipping the second (operand) qubit if the first (control) qubit is set.

This gate is the first example of a controlled quantum gate that you should study.

1000010000010010

CNOT gate matrix

.

Figure 1.
CNOT gate symbol
. Source. The symbol follow the generic symbol convention for controlled quantum gates shown at Figure "Generic controlled quantum gate symbol", but replacing the generic "U" with the Figure "Quantum NOT gate symbol".

To understand why the gate is called a CNOT gate, you should think as follows.

First let's produce a generic quantum state vector where the control qubit is certain to be 0.

On the standard basis:

∣ 00 ⟩ ∣ 01 ⟩ ∣ 10 ⟩ ∣ 11 ⟩

we see that this means that only

∣ 00 ⟩

and

∣ 01 ⟩

should be possible. Therefore, the state must be of the form:

x y 00

where

x

and

y

are two complex numbers such that

∣ x ∣ + ∣ y ∣ = 1.0

If we operate the CNOT gate on that state, we obtain:

1000010000010010 \times x y 00 = x y 00

and so the input is unchanged as desired, because the control qubit is 0.

If however we take only states where the control qubit is for sure 1:

1000010000010010 \times 00 x y = 00 y x

Therefore, in that case, what happened is that the probabilities of

∣ 10 ⟩

and

∣ 11 ⟩

were swapped from

x

and

y

to

y

and

x

respectively, which is exactly what the quantum NOT gate does.

So from this we understand more concretely what "the gate only operates if the first qubit is set to one" means.

Now go and study the Bell state and understand intuitively how this gate is used to produce it.

 Read the full article

Code golf Updated 2025-07-16

 Read the full article

Competitive programming website Updated 2025-10-14

 Read the full article

Complete basis Updated 2025-07-16

Finding a complete basis such that each vector solves a given differential equation is the basic method of solving partial differential equation through separation of variables.

The first example of this you must see is solving partial differential equations with the Fourier series.

Notable examples:

Fourier series for the heat equation as shown at Fourier basis is complete for $L^{2}$ and solving partial differential equations with the Fourier series
Hermite functions for the quantum harmonic oscillator
Legendre polynomials for Laplace's equation in spherical coordinates
Bessel function for the 2D wave equation on a circular domain in polar coordinates

 Read the full article

Complex dot product Updated 2025-07-16

This section is about the definition of the dot product over

C^{n}

, which extends the definition of the dot product over

R^{n}

.

Some motivation is discussed at: math.stackexchange.com/questions/2459814/what-is-the-dot-product-of-complex-vectors/4300169#4300169

The complex dot product is defined as:

\sum a_{i} \overline{b_{i}}

E.g. in

C^{1}

:

(a + bi) \cdot (c + d i) = (a + bi) (\overline{c + d i}) = (a + bi) (c - d i) = (a c + b d) + (b c - a d) i

We can see therefore that this is a form, and a positive definite because:

(a + bi) \cdot (a + bi) = (aa + bb) + (ba - ab) i = a^{2} + b^{2}

Just like the usual dot product, this will be a positive definite symmetric bilinear form by definition.

 Read the full article

Computable problem Updated 2025-07-16

A:

decidable problem is to a decision problem
like a computable problem is to a function problem

 Read the full article

Computational biology Updated 2025-07-16

 Read the full article

Computational complexity of modular exponentiation Updated 2025-07-16

math.stackexchange.com/questions/2382011/computational-complexity-of-modular-exponentiation-from-rosens-discrete-mathem mentions:

b^{n} m o d m

can be calculated in:

l o g (m)^{2} l o g (n)

Remember that

l o g (m)

and

l o g (n)

are the lengths in bits of

m

and

n

, so in terms of the length in bits

M

and

N

we'd get:

M^{2} N

 Read the full article

Computational physics Updated 2025-07-16

The intersection of two beautiful arts: coding and physics!

Computational physics is a good way to get valuable intuition about the key equations of physics, and train your numerical analysis skills:

classical mechanics
- "Real-time heat equation OpenGL visualization with interactive mouse cursor using relaxation method" under the best articles by Ciro Articles
phet.colorado.edu PhET simulations from University of Colorado Boulder

Other child sections:

 Read the full article

Computational protein folding implementation Updated 2025-07-16

 Read the full article

Computer chess competition Updated 2025-10-14

 Read the full article

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