update notations and fix typos

This commit is contained in:
Zheyuan Wu
2025-02-25 20:41:35 -06:00
parent 419ea07352
commit 27bff83685
71 changed files with 920 additions and 430 deletions

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@@ -96,7 +96,7 @@ We wait for $R$ times and then take the stairs. In worst case, we wait for $R$ t
Competitive ratio = $\frac{2R}{R}=2$.
EOP
QED
Let's try $R=S-E$ instead.
@@ -116,7 +116,7 @@ We wait for $R=S-E$ times and then take the stairs.
Competitive ratio = $\frac{S-E+S}{S}=2-\frac{E}{S}$.
EOP
QED
What if we wait less time? Let's try $R=S-E-\epsilon$ for some $\epsilon>0$
@@ -174,7 +174,7 @@ The optimal offline solution: In each subsequence, must have at least $1$ miss.
So the competitive ratio is at most $k+1$.
EOP
QED
Using similar analysis, we can show that LRU is $k$ competitive.
@@ -184,7 +184,7 @@ Split the sequence into subsequences such that each subsequence LRU has $k$ miss
Argue that OPT has at least $1$ miss in each subsequence.
EOP
QED
#### Many sensible algorithms are $k$-competitive
@@ -210,7 +210,7 @@ So competitive ratio is at most $\frac{ck}{(c-1)k}=\frac{c}{c-1}$.
_Actual competitive ratio is $\sim \frac{c}{c-1+\frac{1}{k}}$._
EOP
QED
### Conclusion
@@ -297,7 +297,7 @@ Let $P$ be a page in the cache with probability $1-\frac{1}{k}$.
With probability $\frac{1}{k}$, $P$ is not in the cache and RAND evicts $P'$ in the cache and brings $P$ to the cache.
EOP
QED
MRU is $k$-competitive.
@@ -317,4 +317,4 @@ Let's define the random variable $X$ as the number of misses of RAND MRU.
$E[X]\leq 1+\frac{1}{k}$.
EOP
QED