Chapter 8:

1. Without the standard giving some guarantees on the behavior of C++ programs in the presence of threads, it is not possible to write any portable concurrent C++ programs. Of course, in practice, we were using concurrency long before C++11, but this was made possible by the compiler writers who chose to follow an additional standard, such as POSIX. The downside of that situation was that these additional standards varied. There was no portable way to write, for example, concurrent programs for Linux and Windows without conditional compilation and OS-specific extensions for each platform. Similarly, atomic operations were implemented as CPU-specific extensions. Also, there were some subtle differences between various standards followed by different compilers, which occasionally resulted in very hard-to-find bugs.
2. The use of parallel algorithms is very simple: any algorithm that has a parallel version can be invoked with an execution policy as the first argument. If...