Ghislain Putois website

Fade to black

Sat, 30 Jan 2021 00:00:00 +0000

Fade to Black</h1>
What is the common point between a Desktop Manager (KDE Plasma) and a gorgeous 3D modeler (Blender) ? Something that was bugging me, a black screen. On KDE Plasma 5.8 with default settings, everything went pitch black when i toggle fullscreen, whereas in Blender, when I tried to use transparent reference images, nothing was displayed. It turned out there is a common problem with my underlying graphc card, an Intel HD Graphics 520, and OpenGL 3.1, when using partial transparency.</p>

Workaround</h1>
For blender, running it with `MESA_LOADER_DRIVER_OVERRIDE=i965 ./blender</code> gets rid of this bug. Whereas for KDE, one should disable the fullscreen effect plugin.</p>`



Cardiac Coherence
Tue, 26 Jan 2021 00:00:00 +0000
Cardiac Coherence</h1>
Disclaimer : I am not a MD.</p>
The autonomic nervous system keeps up alive, pumping and breathing. It is composed of : the sympathetic system, firing up our reaction, and the parasympathetic system, responsible for getting back to calm.</p>
There exists a simple way to influence our parasympathetic system, by stimulating the vagus nerve through a controlled breathing, deeper and slower than usual. Good results might be obtained by breathing in for 5 seconds through the nose, and breathing out for 5 seconds through the mouth, for a duration of 5 minutes.</p>
I have therefore developed a little web page with music and visual aids to support your breathing. You can find the page here</a> . For the more tech savy of you, the project was built using ELM Language v0.19</a>, and is released into the public domain here</a>. </p>
In these times of covid 19 and other respiratory problems, I hope this can help you stay safe. Beware, this is no cure ! Should you get any symptoms indicative of a resipratory distress, please consult the ER or a qualified MD.</p>


SSH and keys
Sat, 23 Jan 2021 00:00:00 +0000
SSH and keys</h1>
Everyone always told you password is bad security. And you are just so lazy, and deploying your keys seems complicated.</p>
no more ! Use ssh-keygen and ssh-copy-id :</p>
.
ssh-keygen
ssh-copy-id ~/.ssh/[my_key] [user]@[host]
.</p>
Replace [my_key] by the your keyfile.
[user] and [host] are to be replaced by the login credential to the host where you wnt to deploy your keys.</p>
And that's it ! Keep the private key ~/.ssh/[my_key] file protected at all costs.</p>


Another photo gallery
Sat, 23 Jan 2021 00:00:00 +0000
A glamour portrait gallery</h1>


  
    
      
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</div>


2021, A Home Odyssey
Fri, 22 Jan 2021 00:00:00 +0000
2021, A Home Odyssey</h1>
After a crash during update of Ubuntu on my vps, I have decided to build a website anew, for personal ramblings on programming, arts and life.</p>
As I am playing quite a lot with rust recently, I turned to the Zola</a> static site generator. I also found a quite appealing (to me) theme called DeepThought, which also includes some interesting javascript libraries, amongst them :</p>


Mermaid</a> generates diagrams from a textual description (like graphviz, but at runtime). As one says, a picture is worth a thousand words, and I know how lazy I am, even for writing ;-)</p>
</li>

Chart.xkcd</a> generates nice hand-drawn looking charts, in the style of the famous XKCD</a> comics.</p>
</li>
</ul>


Rust, graphs, raw memory, and arena allocators
Fri, 22 Jan 2021 00:00:00 +0000
Rust, graphs, raw memory, and arena allocators</h1>
Context</h2>
Rust is a very solid language to build safe programs, when one can abide by its memory model and contrainsts : an object must have a unique owner. 
This constraint enable rust compiler to statically check the program, and avoid numerous bugs which would lead to undefined behaviours, race conditions, and other nasty deadly memory overlap bugs.</p>
Objective</h2>
However, when one wants to manage more complex structured data like graphs, where nodes can reference each others, it is very difficult to work within the "single ownership" model. This article will track my learnings and experiments around the darker, unsafe rituals needed to work as safely as possible whith graph structures.</p>
Some leads to investigate</h2>

Rust Petgraph crate</a>,</li>
Rust unsafe keyword use and raw pointers.(see the rustonomicon</a>),</li>
Manual Arena allocator (CAD97),</li>
Slice-dst crate</li>
</ul>
Graph model and foreseen implementation</h2>
I would like to base my graph model on the hypergraphdb</a> approach, as found in the paper hypergraphDB A Genealized Graph Database</a>.</p>
The hypergraph is composed of :</p>

atoms : nodes, directed edges, and hyperedges (like ordered set of nodes, or n-ary relationships)...</li>
kinds : types (but type is a reserved rust keyword)</li>
values : primitive or complex types</li>
</ul>
An Atom is used to represent a structure element of the hypergraph. In rust, it is composed of :</p>

an Id,</li>
a Kind,</li>
a Value, of type Kind,</li>
a vector of targets ids</li>
</ul>
A Kind is also stored as an Atom.</p>


Priors and medecine
Fri, 22 Jan 2021 00:00:00 +0000
Priors in medecine</h1>
Context</h2>
Why is is so hard to agree on the efficiency of a cure for an ill patient ?</p>
I would argue here that this is caused by disagrement on about each one perceives the patient condition.</p>
First and foremost, a deviation</h2>
Let's take a slight deviation to some subsets of mathematics, called statistics and probability theory.</p>
The statistics is the science dedicated to measure the prevalence of an event, and of its relations to other events, inside the universe of "past measurable events".</p>
The probability theories explore how one can estimate the occurence of an event in the future. They work within a universe of "possible events".</p>
Statistics and probabilities are often linked through a probability theory.</p>
Frequentist or Bayesian</h2>
Two main probability theories are common, they both express probabilities between 0 ("not possible at all") and 1 ("fully certain"), but ascribe different meanings.</p>
The frequentist theory poses that the only "possible events" are events whch were already measured in the past.</p>
For instance, if a dice has rolled only 6s for eight rolls, there is only one possible outcome in the frequentist probability theory for a future roll, which is a 6, so the frequentist probability of rolling a 6 is 1.</p>
On the other end, the bayesian probability is not interested directly in measure events, but on "natural causes". A 6 face dice perfectly balanced has "a natural probability of rolling a 6" of 1/6. This natural probability is called a prior</em>.</p>
Interesting enough, if the number of rolls is large, the probabilities in both models converge to the same value, called the expected value</em> : the more rolls you observe, the more precise will be your prior</em>, and the more precise your frequentist probability.</p>
Convergence on large population, divergence at small scale</h2>
However, this only applies for a large number of measured past events, and not for each individual event.
This fact is hopefully well known for all gamblers amongst you, and depending if you are more inclined towards the frequentist , after our eight rolls, you will bet big on the next roll being a 6, whereas if you are a bayesian player, you wouldn't bet much, and probably begin to suspect that the "fair" dice might be not so fair...</p>
Back to medecine</h2>
So when one has to evaluate the relevance of a cure, they only get at best the probability measured in a statistically way. For the frequentist practitioner, this is the true probability, and should be used for decision. However the true probability would only be meaningful if we were talking about exactly the "same event" ; aggregating a cure given to different people into "a same cure" is probably dubious at best, because every patient had different circumstances (general immunity health, gene expressions...). The frequentist approach is probably not the best approach for an MD.</p>
On the other hand, for the bayesian practitioner, it is at best one element influencing their own estimation of the prior</em>, the other elements being their perception of the prevalence of the disease in the general population, and their own biases based on when and how they have been taught medecine, and all the consensus slowly formed by experimenting. One can see that the bayesian approach might be here more relevant, as it somehow integrates the "causal factors" of a disease propagation. However, at the extreme, if a bayesian practitioner does not known about an emerging disease, which becomes heavily prevalent, then, they will be biased against curing it...</p>


A photo gallery
Fri, 22 Jan 2021 00:00:00 +0000
Nature</h1>


  
    
      
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</div>

Ghislain Putois website

Fade to black

Workaround</h1> For blender, running it with MESA_LOADER_DRIVER_OVERRIDE=i965 ./blender</code> gets rid of this bug. Whereas for KDE, one should disable the fullscreen effect plugin.</p>

Cardiac Coherence

SSH and keys

Another photo gallery

A glamour portrait gallery</h1> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </div>

2021, A Home Odyssey

2021, A Home Odyssey</h1> After a crash during update of Ubuntu on my vps, I have decided to build a website anew, for personal ramblings on programming, arts and life.</p>

Rust, graphs, raw memory, and arena allocators

Rust, graphs, raw memory, and arena allocators</h1>

Priors and medecine

Priors in medecine</h1>

Context</h2> Why is is so hard to agree on the efficiency of a cure for an ill patient ?</p> I would argue here that this is caused by disagrement on about each one perceives the patient condition.</p>

A photo gallery

Workaround</h1>
For blender, running it with `MESA_LOADER_DRIVER_OVERRIDE=i965 ./blender</code> gets rid of this bug. Whereas for KDE, one should disable the fullscreen effect plugin.</p>`

A glamour portrait gallery</h1>
</a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </a> </div>

Context</h2>
Why is is so hard to agree on the efficiency of a cure for an ill patient ?</p>
I would argue here that this is caused by disagrement on about each one perceives the patient condition.</p>