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Tony van Eerd: C++ Memory Model & Lock-Free Programming (Avast C++ Meetup Prague) https://youtube.com/watch?v=14ntPfyNaKE https://redd.it/9p220b @r_cpp

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Ludovic 'Archivist'

Tony van Eerd: C++ Memory Model & Lock-Free Programming (Avast C++ Meetup Prague) https://youtube.com/watch?v=14ntPfyNaKE https://redd.it/9p220b @r_cpp

I was given a good analogy for how lock free programming work in school: your threads are dudes in some heavy tempest, they all have setup some pile of rocks, and to communicate, they ship it to a shared pile of rock. Rocks have values written on them, as well as a position. Threads can copy rocks at the pile and then tinker with them here to update their value. But when they meet a guy on their way, they can just hand it the value for copy, and so there is no real consistency here. When you are relaxed on your memory order, it means you've done all the job and can ship the rock to the pile. When your memory order is acquired, it means you just came from the pile to acquire a rock.

Ludovic 'Archivist'

And all those guys try to walk the least possible while doing their job

Ludovic 'Archivist'

So sometime, if they meet a dude that is just coming from or going to the pile, they'll merrily trade rocks on the way

Ludovic 'Archivist'

So if you are to ask one of the dude what value is on the pile, he'll just likely tell you shit even if he is just coming back from it

Ludovic 'Archivist'

And on NUMA, it is the same, except there are two shared piles of rocks, one blue and one red, and no one wants to mix them somehow

Ludovic 'Archivist'

So guys from the blue pile make red copies of their rocks for the red guys to use and vice versa

Ludovic 'Archivist'

And when they want some copies and no one's there, they yell in the hail until someone comes to make the copy

Ludovic 'Archivist'

CPUs are like that: an associal bunch of lazy dudes in an hail storm

Ибраги́м

Ur bedtime story will make child sleep early not because it's great but because it's punishing

Ludovic 'Archivist'

Ur bedtime story will make child sleep early not because it's great but because it's punishing

At least it may teach something

Ludovic 'Archivist'

BTW, distributed programming is the same, except the dudes exchange the rocks with trebuchets

Ибраги́м

I was given a good analogy for how lock free programming work in school: your threads are dudes in some heavy tempest, they all have setup some pile of rocks, and to communicate, they ship it to a shared pile of rock. Rocks have values written on them, as well as a position. Threads can copy rocks at the pile and then tinker with them here to update their value. But when they meet a guy on their way, they can just hand it the value for copy, and so there is no real consistency here. When you are relaxed on your memory order, it means you've done all the job and can ship the rock to the pile. When your memory order is acquired, it means you just came from the pile to acquire a rock.

A tempest is already implicitly "violent", why add heavy ?

Ludovic 'Archivist'

A tempest is already implicitly "violent", why add heavy ?

For the same reason one adds light to lightbulbs

Ибраги́м

For the same reason one adds light to lightbulbs

No. No try harder

Ибраги́м

BTW, distributed programming is the same, except the dudes exchange the rocks with trebuchets

Now u talking siege engines

Anonymous

CPUs are like that: an associal bunch of lazy dudes in an hail storm

what the f Dude CPUs are CPUs Central processor unit if anyone want more information, can read books, webpages, etc... this group is not for <10 kids

Ибраги́м

what the f Dude CPUs are CPUs Central processor unit if anyone want more information, can read books, webpages, etc... this group is not for <10 kids

I'm pretty sure you're lost on his explanation

Anonymous

I hate the education system

Bro. What can we do about it?

klimi

Bro. What can we do about it?

Change it

Ludovic 'Archivist'

what the f Dude CPUs are CPUs Central processor unit if anyone want more information, can read books, webpages, etc... this group is not for <10 kids

And this analogy was given to me by a 50yo man

Ludovic 'Archivist'

what the f Dude CPUs are CPUs Central processor unit if anyone want more information, can read books, webpages, etc... this group is not for <10 kids

It is an explanation of what is the actual way memory work in a CPU and why memory operations are tendious

Anonymous

Rose is killing the game 🤣