23.7. Summary

Writing concurrent programs is not always important. If your code runs fast enough on a single core, then the only reason to write concurrent code is if it is conceptually parallel. If this is the case, then writing a program that is split over multiple threads or processes will make development easier.

If your program is conceptually serial, or has interlocking components that make splitting it into parallel parts difficult, then try running it before you decide to make it parallel. While I am writing this, Activity Monitor tells me I have 454 threads running in 119 processes and yet my CPU load is only 5%. Splitting any of the running processes into more threads would make the load higher from the extra locking and context switching overhead; it wouldn’t make anything faster.