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

vault backup: 2025-03-10 19:32:06

Browse source
This commit is contained in:
Marco Realacci 2025-03-10 19:32:06 +01:00
parent e206c6bcf7
commit 67736a6535
1 changed files with 3 additions and 3 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

6
Concurrent Systems/notes/3.md
View file

@ -265,15 +265,15 @@ It looks like I can experience at most $2n-1$ other critical sections, but it is
- $p_{n}$ has to wait all other processes to complete their CSs - $p_{n}$ has to wait all other processes to complete their CSs
- when $p_{n-1}$ completes its CS, its new DATE will be $n+(n-1)+1=2n$ -> RESET - when $p_{n-1}$ completes its CS, its new DATE will be $n+(n-1)+1=2n$ -> RESET
- now all $p_{1}\dots p_{n-1}$ invoke lock again and complete their CSs (after that $p_i$ completes its CS, now it has `DATE[i] <- n+i`, because as everyone invoked lock after the RESET, max date was `n`) - now all $p_{1}\dots p_{n-1}$ invoke lock again and complete their CSs (after that $p_i$ completes its CS, now it has `DATE[i] <- n+i`, because as everyone invoked lock after the RESET, max date was `n`)
- so $p_n$ has to wait n-1 CSs for the reset, and another n-1 CSs before entering again - so $p_n$ has to wait n-1 CSs for the reset, and another n-1 CSs before entering again. **Literally the worst case is when the process is the first of the first round, and the last of the last round.**
#### Improvement of Aravind’s algorithm #### Improvement of Aravind’s algorithm
``` ```
unlock(i) := unlock(i) :=
∀j≠i.if DATE[j] > DATE[i] then ∀j≠i.if DATE[j] > DATE[i] then
DATE[j] <- DATE[j]-1 DATE[j] <- DATE[j]-1
DATE[i] <- n STAGE[i] <- 0 DATE[i] <- n
STAGE[i] <- 0
FLAG[i] <- down FLAG[i] <- down
``` ```