Banker Algorithm

This is a version of the banker algorithm which is an algorithm to resource allocation with impass prevention, this version makes a simulation using process created manually and how they are managed.

The project is separated in five packages:

• domain: related to the business rules
  

  • BankerObj.java
    Contains the quantity and arrays of processes and available resources, in addiction to the AllocationA, ClaimC and NeedCA (C-A) matrices. The matrices are made with the List of ProcessObj with which we can dinamically add and remove processes.
  • ProcessObj.java
    Used as a process object, it contains an ID and an array of resources, this array is the maximum of resources necessary for the process.

• port: the ports related to the application
  

  • Cli.java
    Handle the man-machine-interface to the application
  • FileDataInput.java
    Handle the file data input

• thread: contains the threads
  

  • ThreadNewProcess.java
    Insert new processes to the application in runtime execution (6 process with 15 sec interval)
  • ThreadRunBanker.java
    Run the banker algorithm itself. The simulation of a process execution is handled by the Thread.Sleep in 10 sec.

• usecase: usecases of the application
  

  • AddProcess.java
    Add the process in runtime, invoked by ThreadNewProcess each 15 sec.
  • CheckSafeState.java
    Check if the system is in SAFE/ UNSAFE state
  • ExecuteBanker.java
    Run the banker algorithm itself
  • LoadProcesses.java
    Load the processes to the system from startFile.txt

• Main.java
  Run the application starting all classes used by application

Flowcharts

Execution

Case 1, the best cenario, new process added but keep SAFE:
Input: ______________________________________________________________________________

---

Output:

---

The starterFile generate the following matrix:

The banker started in SAFE state

As the new processes are add the banker keep running, but updating the sequence of processes

The list of executed process:

---

Case 2, on this case the system is started in SAFE state but turn to UNSAFE when adding process at runtime:
Input:

---

---

Output:

---

The starterFile generate the following matrix:

The banker started in SAFE state

After insert P6 the system go to UNSAFE state

After that the system can't exit of the UNSAFE:

---

Conclusion The algorithm works as expected managing a lot of Deadlocks. But handle new process insertion is a problem, the process already enter allocating some resource, and, with that, the system go to UNSAFE state, in addiction to, the simulation is not considering the execution time of a process, if a process takes a long time all other process need to wait until the end.
Another not considered question is if a process need more resources when it is running, in this case all system will stop. Despite that the banker's algorithm is interesting when it is running on a limited and controlled operational system, with the knowledge of all processes used by the system.