marcorealacci/master-degree-notes
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

vault backup: 2025-04-05 00:05:56

Browse source
This commit is contained in:
Marco Realacci 2025-04-05 00:05:56 +02:00
parent a99d09af0c
commit 47b74f3eec
4 changed files with 6 additions and 6 deletions
Download patch file Download diff file Expand all files Collapse all files

6
.obsidian/workspace.json vendored
View file

@ -13,12 +13,12 @@
"state": { "state": {
"type": "markdown", "type": "markdown",
"state": { "state": {
"file": "Concurrent Systems/notes/1b - Peterson algorithm.md", "file": "Concurrent Systems/notes/2b - Round Robin algorithm.md",
"mode": "source", "mode": "source",
"source": false "source": false
}, },
"icon": "lucide-file", "icon": "lucide-file",
"title": "1b - Peterson algorithm" "title": "2b - Round Robin algorithm"
} }
} }
] ]
@ -191,8 +191,8 @@
}, },
"active": "7c5b0ca6f7687800", "active": "7c5b0ca6f7687800",
"lastOpenFiles": [ "lastOpenFiles": [
"Concurrent Systems/notes/images/Pasted image 20250405000438.png",
"Concurrent Systems/notes/1b - Peterson algorithm.md", "Concurrent Systems/notes/1b - Peterson algorithm.md",
"Concurrent Systems/notes/images/Pasted image 20250405000438.png",
"Pasted image 20250405000428.png", "Pasted image 20250405000428.png",
"Concurrent Systems/notes/3b - Aravind's algorithm and improvements.md", "Concurrent Systems/notes/3b - Aravind's algorithm and improvements.md",
"Concurrent Systems/notes/4 - Semaphores.md", "Concurrent Systems/notes/4 - Semaphores.md",

2
Concurrent Systems/notes/1b - Peterson algorithm.md
View file

@ -140,7 +140,7 @@ Easy to generalize to k-MUTEX.
Peterson's algorithm cost $O(n^2)$ Peterson's algorithm cost $O(n^2)$
A first way to reduce this cost is by using a tournament of MUTEX between pairs of processes: A first way to reduce this cost is by using a tournament of MUTEX between pairs of processes:
![350](Concurrent%20Systems/notes/images/Pasted%20image%2020250304082459.png|) ![350](images/Pasted%20image%2020250304082459.png|)
Of course this is a binary tree, and the height of a binary tree is logaritmic to the number of leaves. A process then wins after $\lceil \log_{2}n \rceil$ competitions $\to O(\log n)$ cost. Of course this is a binary tree, and the height of a binary tree is logaritmic to the number of leaves. A process then wins after $\lceil \log_{2}n \rceil$ competitions $\to O(\log n)$ cost.

2
Concurrent Systems/notes/4 - Semaphores.md
View file

@ -180,7 +180,7 @@ producer A:
- so producer A will write at `BUF[0]` - so producer A will write at `BUF[0]`
- but wait! Consumer B is still reading there - but wait! Consumer B is still reading there
- **Producer A doesn't give a fuck.** - **Producer A doesn't give a fuck.**
![200](Concurrent%20Systems/notes/images/Pasted%20image%2020250312121828.png|) ![]()
*don't be like Producer A, be more like Bob, who always scans EMPTY before!* *don't be like Producer A, be more like Bob, who always scans EMPTY before!*
So the issue here is that producers just assume that IN is the first available slot. But it its not necessarily the case. So the issue here is that producers just assume that IN is the first available slot. But it its not necessarily the case.

2
Concurrent Systems/notes/4c - Dining Philosophers.md
View file

@ -3,7 +3,7 @@ The first real practical example of a concurrent system.
- one chopstick between each pair of philosophers - one chopstick between each pair of philosophers
- a philosophers must pick up its two nearest chopsticks in order to eat - a philosophers must pick up its two nearest chopsticks in order to eat
- a philosopher must pick up first one chopstick, then the second one, not both at once - a philosopher must pick up first one chopstick, then the second one, not both at once
![100](Concurrent%20Systems/notes/images/Pasted%20image%2020250317100456.png|) ![]()
**PROBLEM:** *Devise a deadlock-free algorithm for allocating these limited resources (chopsticks) among several processes (philosophers).* **PROBLEM:** *Devise a deadlock-free algorithm for allocating these limited resources (chopsticks) among several processes (philosophers).*