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Im (re)writing a socket server in ruby in hopes of simplifying it. Reading about ruby sockets I ran across a site that says multithreaded ruby apps only use one core / processor in a machine.
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In computer architecture, multithreading is the ability of a central processing unit (CPU) (or a single core in a multi-core processor) to provide multiple threads of execution concurrently, supported by the operating system. This approach differs from multiprocessing.
Yes, threads and processes can run concurrently on multi-core CPUs, so this works as you describe (regardless of how you create those threads and processes, OpenMP or otherwise). A single process or thread only runs on a single core at a time.
Multi-threading is the most useful property of Ruby which allows concurrent programming of two or more parts of the program for maximizing the utilization of CPU. Each part of a program is called Thread. So, in other words, threads are lightweight processes within a process.
Thread allocation is managed by the operating system. Threads are created using OS system calls and, if the process happens to run on a multi-core processor, the OS automatically tries to allocate / schedule different threads on different cores. Thread allocation is managed by the programming language implementation.
There is a very nice gem called parallel which allows data processing with parallel threads or multiple processes by forking (work around GIL of current CRuby implementation).
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CRuby has a global interpreter lock, so it cannot run threads in parallel. Jruby and some other implementations can do it, but CRuby will never run any kind of code in parallel. This means that, no matter how smart your OS is, it can never share the load.
This is different in threading in C++. pthreads create real OS threads, and the kernal's scheduler will run them on multiple cores at the same time. Technically Ruby uses pthreads as well, but the GIL prevents them from running in parallel.
Fork creates a new process, and your OS's scheduler will almost certainly be smart enough to run it on a separate core. If you need parallelism in Ruby, either use an implementation without a GIL, or use fork.
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