LRU Algorithm
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Transcript of LRU Algorithm
LRU AlgorithmLeast Recently Used
Introduction
The fact that the world is doomed with computer, people’s daily living and how the world works nowadays become more modernized. Yet, this is the external reality in this computer era.
We must go deeper by fully
understanding the real thing behind
the direct usage of computers. The
computer world is synthesized, by
means of operations done inside for it
to function.
There are more instances
that troubles occur which we
are supposed to solve in order
to regulate or stabilize
operations.
In order to that, there’s what
we call mapping functions which
we used to avoid conflict of data
processed which involve
different replacement algorithms.
One is Least Recently Used
(LRU). It used to replace a block that
has been in the cache longest with no
reference to it. This will be useful to
lessen the errors and cache miss.
We are assigned to make a program
which executes Least Recently Used
(LRU) Algorithm. It used to replace a
block that has been in the cache longest
with no reference to it. This will be useful
to lessen the errors and data traffic.
Statement of the Problem
The cache stores some of the data that
are transferred from the main memory in
order not to search again for it when the
same data was again needed.
But there’s this THRASHING where a
data that was just removed in the
cache is again needed. So, we make
use of different replacement algorithms
to lessen the error.
LFU considers a counter. FIFO
considers time. While LRU considers
both time and counter.
With these different algorithms, it
is hard to know which is the most
effective to lessen the errors.
Objectives To illustrate how Least Recently Used (LRU)
Algorithm work.
To understand the logical operations done
behind the level of the computer user.
To know and understand the significance of
using LRU.
To know what is easier to use
between LFU,LRU or FIFO.
To prove that LRU is effective in
lessening error and data traffic.
Objectives(cont)
Significance of the Study
Knowing and understanding LRU
allows us to use the algorithm properly
in order for us to achieve the objectives
and solve the statement of the problem.
We will be able to differentiate the
said algorithm with the other types and
for us to identify its strength and
weakness in order to select the
appropriate algorithm to be used.
Least Recently Used (LRU) Algorithm
• When a new block is stored in the cache,
LRU replaces the block that has not been
used for the longest period of time.
Process
a) Divide the main memory
block by the number of sets.
The remainder determines
which set it would belongs.
b) Every time a block is stored,
the time increases. But if
there is a cache hit, the counter
will be incremented.
c) It would compare the counter of the
other blocks in that set and replaces
the one with the least counter.
d) But if there are two blocks with the
same counter, it will then consider the
time and replaces the one with the
longest time.
MM Blocks: 1,2,3,4,1,5,5,7,6,4
Example:
Compared to LFU and FIFO, LRU is
harder to implement because it considers
both time and counter. On the other
hand, it is more effective than the other
two because there is less thrashing
during the process.
Conclusion
Understanding and applying the
concepts of LRU Algorithm is very
useful and contributed a lot for us to
come up a program which executes
the said algorithm.
THANK YOU !Prepared by :
Balatico, Rey Steve P.Bibit, Mae RoseArce, Crissel Lyka Q.Coloma, Madeline C.Lacar, Larissa Vivien S.Manglal-lan, Rizaldy Jr.Salacup, KathleenSoriano, Ethelyn Joyce
BSCS II-A