Consider a dinner table where n dining philosophers are seated. Each
philosopher has a plate of food; however, there is only a single eating-utensil placed
in the center of the table. Eating is done at discrete rounds. At the beginning of
each round, if a philosopher wishes to eat, she may attempt to obtain the utensil
from the center of the table. If the philosopher obtains the utensil, she eats for the
duration of the round (i.e., only one philosopher may eat during any given round)
and then places the utensil back at the table center at the end of the round. If
two or more philosophers attempt to obtain the utensil at the beginning of the
same round, then no philosopher will eat during that round (i.e., no one obtains the
utensil); thus, if all the philosophers try to access the utensil on every round, no
philosopher would ever eat.
One way to avoid the starvation of these philosophers is to use randomization. A
possible simple randomized algorithm is to have each philosopher attempt to obtain
the utensil at any given round with probability p > 0 (independently of the decisions
of the other philosophers).
a) What is the probability (in terms of p) that a philosopher is able to successfully
eat during any given single round?
b) What value of p maximizes this probability?
c) Using the probability from Part b, what is the probability that a philosopher
does not successfully obtain the utensil after k consecutive rounds?
Solution
a.) p*(1-p)^n b.) p = 1/n c.) [(1- 1/n)^n ]/n.
social pharmacy d-pharm 1st year by Pragati K. Mahajan
Consider a dinner table where n dining philosophers are seated. Each.pdf
1. Consider a dinner table where n dining philosophers are seated. Each
philosopher has a plate of food; however, there is only a single eating-utensil placed
in the center of the table. Eating is done at discrete rounds. At the beginning of
each round, if a philosopher wishes to eat, she may attempt to obtain the utensil
from the center of the table. If the philosopher obtains the utensil, she eats for the
duration of the round (i.e., only one philosopher may eat during any given round)
and then places the utensil back at the table center at the end of the round. If
two or more philosophers attempt to obtain the utensil at the beginning of the
same round, then no philosopher will eat during that round (i.e., no one obtains the
utensil); thus, if all the philosophers try to access the utensil on every round, no
philosopher would ever eat.
One way to avoid the starvation of these philosophers is to use randomization. A
possible simple randomized algorithm is to have each philosopher attempt to obtain
the utensil at any given round with probability p > 0 (independently of the decisions
of the other philosophers).
a) What is the probability (in terms of p) that a philosopher is able to successfully
eat during any given single round?
b) What value of p maximizes this probability?
c) Using the probability from Part b, what is the probability that a philosopher
does not successfully obtain the utensil after k consecutive rounds?
Solution
a.) p*(1-p)^n b.) p = 1/n c.) [(1- 1/n)^n ]/n
![Consider a dinner table where n dining philosophers are seated. Each
philosopher has a plate of food; however, there is only a single eating-utensil placed
in the center of the table. Eating is done at discrete rounds. At the beginning of
each round, if a philosopher wishes to eat, she may attempt to obtain the utensil
from the center of the table. If the philosopher obtains the utensil, she eats for the
duration of the round (i.e., only one philosopher may eat during any given round)
and then places the utensil back at the table center at the end of the round. If
two or more philosophers attempt to obtain the utensil at the beginning of the
same round, then no philosopher will eat during that round (i.e., no one obtains the
utensil); thus, if all the philosophers try to access the utensil on every round, no
philosopher would ever eat.
One way to avoid the starvation of these philosophers is to use randomization. A
possible simple randomized algorithm is to have each philosopher attempt to obtain
the utensil at any given round with probability p > 0 (independently of the decisions
of the other philosophers).
a) What is the probability (in terms of p) that a philosopher is able to successfully
eat during any given single round?
b) What value of p maximizes this probability?
c) Using the probability from Part b, what is the probability that a philosopher
does not successfully obtain the utensil after k consecutive rounds?
Solution
a.) p*(1-p)^n b.) p = 1/n c.) [(1- 1/n)^n ]/n](https://image.slidesharecdn.com/consideradinnertablewherendiningphilosophersareseated-230327025051-a06810ea/85/Consider-a-dinner-table-where-n-dining-philosophers-are-seated-Each-pdf-1-320.jpg)
