Threads #

If you think your programs crashing before, wait until they crash ten times as fast

A thread is short for ‘thread-of-execution’. It represents the sequence of instructions that the CPU has and will execute. To remember how to return from function calls, and to store the values of automatic variables and parameters a thread uses a stack. Almost weirdly, a thread is a process, meaning that creating a thread is similar to fork, except there is no copying meaning no copy on write. What this allows is for a process to share the same address space, variables, heap, file descriptors and etc. The actual system call to create a thread is similar to fork. It’s clone. We won’t go into the specifics, but you can read the http://man7.org/linux/man-pages/man2/clone.2.html keeping in mind that it is outside the direct scope of this course. LWP or Lightweight Processes or threads are preferred to forking for a lot of scenarios because there is a lot less overhead creating them. But in some cases, notably python uses this, multiprocessing is the way to make your code faster.