Intel Threading Building Blocks

What Is a Thread?

If you know what a thread is, skip ahead to the section “Safety in the Presence of Concurrency.” It’s important to be comfortable with the concept of a thread, even though the goal of Intel Threading Building Blocks is to abstract away thread management. Fundamentally, you will still be constructing a threaded program and you will need to understand the implications of this underlying implementation.

All modern operating systems are multitasking operating systems that typically use a preemptive scheduler. Multitasking means that more than one program can be active at a time. You may take it for granted that you can have an email program and a web browser program running at the same time. Yet, not that long ago, this was not the case.

A preemptive scheduler means the operating system puts a limit on how long one program can use a processor core before it is forced to let another program use it. This is how the operating system makes it appear that your email program and your web browser are running at the same time when only one processor core is actually doing the work.

Generally, each process (program) runs relatively independent of other processes. In particular, the memory where your program variables will reside is completely separate from the memory used by other processes. Your email program cannot directly assign a new value to a variable in the web browser program. If your email program can communicate with your web browser—for instance, to have it open a ...