Pitfalls

We have already discussed many of the problems that we may face when developing parallel program. In this section, we will summarize them with the usual terminology used for the problems. Terminology is not only interesting, but it is also important when you talk with colleagues to easily understand each other.

Deadlocks

Deadlock is the most infamous parallel programming pitfall, and for this reason, we will start with this one. To describe the situation, we will follow the metaphor of bureaucrats.

The bureaucrat has to stamp a paper he has in his hand. To do that, he needs the stamp, and he also needs the inkpad. First, he goes to the drawer where the stamp is and takes it. Then, he walks to the drawer where the inkpad is and takes the inkpad. He inks the stamp, pushes on the paper. Then, he puts the stamp back to its place and then the inkpad back in its place. Everything is nice, we are on cloud 9.

What happens if another bureaucrat takes the inkpad first and then the stamp second...