1) What is the first step in problem-solving? A) Writing code B) Debugging C) Understanding the problem D) Optimizing the solution Answer: C 2) Which of these is not a step in the problem-solving process? A) Algorithm development B) Problem analysis C) Random guessing D) Testing and debugging Answer: C 3) What is an algorithm? A) A high-level programming language B) A step-by-step procedure to solve a problem C) A flowchart D) A data structure Answer: B 4) Which of these is the simplest data structure for representing a sequence of elements? A) Dictionary B) List C) Set D) Tuple Answer: B 5) What does a flowchart represent? A) Errors in a program B) A graphical representation of an algorithm C) The final solution to a problem D) A set of Python modules Answer: B 6) What is pseudocode? A) Code written in Python B) Fake code written for fun C) An informal high-level description of an algorithm D) A tool for testing code Answer: C 7) Which of the following tools is NOT commonly used in pr...
Recovery From Deadlock
There are three basic methods to recovery from deadlock:
i) Inform the system operator, and allow him/her to take manual intercession.
ii) End one or more processes involved in the deadlock
iii) Preempt resources.
Process Termination
1) Two basic methods, both of which recover resources allocated to ended processes:
i) End all processes involved in the deadlock. This definitely solves the deadlock, but at the expense of ending more processes than would be absolutely necessary.
ii) End processes successively until the deadlock is fragmented. This is more conservative, but needs doing deadlock detection after each step.
2) In the latter case there are many factors that can go into deciding which processes to end next:
i) Process priorities.
ii) How long the process has been running, and how close it is to completing.
iii) How many and what type of resources is the process possession. ( Are they easy to prevent and restore? )
iv. How many more resources does the process need to finished.
v. How many processes will need to be ended
vi. Whether the process is relative or batch.
Resource Preemption
When preempting resources to reduce deadlock, there are three important issues to be addressed:
Selecting a victim - Deciding which resources to prevent from which processes involves many of the same decision criteria outlined above.
Rollback - Ideally one would like to roll back a prevented process to a safe state prior to the point at which that resource was originally allocated to the process. Unfortunately it can be difficult or
impossible to determine what such a safe state is, and so the only safe rollback is to roll back all the way back to the origin. (I.e. remove the process and make it start over.)
Starvation - How do you guarantee that a process won't starve because its resources are always being prevented? One option would be to use a priority system, and increase the priority of a process every time its resources get prevented. Eventually it should get a high enough priority that it won't get prevented any more.