How to resolve the algorithm Dining philosophers step by step in the Mathematica / Wolfram Language programming language

Published on 22 June 2024 08:30 PM

How to resolve the algorithm Dining philosophers step by step in the Mathematica / Wolfram Language programming language

Table of Contents

Problem Statement

The dining philosophers problem illustrates non-composability of low-level synchronization primitives like semaphores. It is a modification of a problem posed by Edsger Dijkstra. Five philosophers, Aristotle, Kant, Spinoza, Marx, and Russell (the tasks) spend their time thinking and eating spaghetti. They eat at a round table with five individual seats. For eating each philosopher needs two forks (the resources). There are five forks on the table, one left and one right of each seat. When a philosopher cannot grab both forks it sits and waits. Eating takes random time, then the philosopher puts the forks down and leaves the dining room. After spending some random time thinking about the nature of the universe, he again becomes hungry, and the circle repeats itself. It can be observed that a straightforward solution, when forks are implemented by semaphores, is exposed to deadlock. There exist two deadlock states when all five philosophers are sitting at the table holding one fork each. One deadlock state is when each philosopher has grabbed the fork left of him, and another is when each has the fork on his right. There are many solutions of the problem, program at least one, and explain how the deadlock is prevented.

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Dining philosophers step by step in the Mathematica / Wolfram Language programming language

This code is a simulation of the "dining philosophers" problem, which is a classic example of a synchronization problem in computer science. In this problem, there are $n$ philosophers sitting around a circular table, with a fork to the left and right of each philosopher. The philosophers alternate between thinking and eating, and they can only eat if they have both forks. However, only one philosopher can use a fork at a time, so if a philosopher wants to eat, they must first acquire both forks. If a philosopher cannot acquire both forks, they must wait until both forks are available.

The code you provided uses the Wolfram programming language to simulate the dining philosophers problem. The code first creates a list of the names of the philosophers, and then it sets the number of philosophers to the length of the list. The code then defines a function, rp, which pauses the execution of the code for a random amount of time. The code then prints the names of the forks, and then it clears the definition of the forks function and defines a new function with the same name that returns Null.

The code then uses the With function to create a new scope, and in that scope, it defines a new variable, nf, which is equal to the number of philosophers. The code then uses the ParallelDo function to execute the following code in parallel for each philosopher:

  1. The code sets the variables i1 and i2 to the current philosopher's index and the index of the next philosopher, respectively.
  2. The code prints the name of the current philosopher and the fact that they are thinking.
  3. The code pauses the execution of the code for a random amount of time.
  4. The code prints the name of the current philosopher and the fact that they are hungry.
  5. The code uses the CriticalSection function to acquire the forks to the left and right of the current philosopher.
  6. The code prints the name of the current philosopher and the fact that they are eating.
  7. The code pauses the execution of the code for a random amount of time.
  8. The code releases the forks to the left and right of the current philosopher.

The code then ends the With scope and the ParallelDo loop.

Source code in the wolfram programming language

names = <|1 -> "Aristotle", 2 -> "Kant", 3 -> "Spinoza", 4 -> "Marx", 5 -> "Russell"|>;
n = Length[names];
rp := Pause[RandomReal[4]];
PrintTemporary[Dynamic[Array[forks, n]]];
Clear[forks]; forks[_] := Null;
With[{nf = n},
  ParallelDo[
   With[{i1 = i, i2 = Mod[i + 1, nf, 1]},
    Do[Print[names[i], " thinking"]; rp; Print[names[i], " hungry"];
     CriticalSection[{forks[i1], forks[i2]}, 
      Print[names[i], " eating"]; rp],
     {2}]],
   {i, nf}]];


  

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