There are no queues in CSP, although you can make one by making a queue process. In CSP, the sending side of a message is always logically simultaneous with th

There are no queues in CSP, although you can make one by making a queue process. In CSP, the sending side of a message is always logically simultaneous with the receiving side. So it's like Go's default channels where the sender and receiver both block until ready to transfer, and different from Python's multiprocessing and queue constructs, where the sender doesn't block. CSP was used in Occam¹ on Transputers² in the 1980s. In Occam, it was normal to have a large number of tiny processes, some of them maybe only a few instructions (such as an implementation of a queue), and the thread switching and communication primitives were actual CPU instructions. The CPUs were joined with dedicated message communication links into large meshes, providing hardware parallelism with a very different model than today's SMP multi-core. A similar architecture exists today, XMOS³. Go implements a model similar to CSP on today's SMP multi-core systems and OSes, emphasising many efficient, small threads running loops that communicate synchronously. Channels are unbuffered by default, making them like CSP. They can be made buffered, which adds a queue, as if a CSP queue process was added. Go is much less rigid than Occam, because you can also make new channels and spawn new threads efficiently, which are essential features in modern sofware. Python multiprocessing doesn't provide efficient, small threads. You need larger thread units to get good performance out of it. It also emphasises queuing. So it's quite different from CSP. Erlang implements a model like Occam and Go of many, efficient, small threads, but the messaging is always asynchronous. The communication is similar to Go with buffered channels. ¹ https://en.wikipedia.org/wiki/Occam_(programming_language) https://en.wikipedia.org/wiki/Occam_(programming_language) ² https://en.wikipedia.org/wiki/Transputer https://en.wikipedia.org/wiki/Transputer ³ https://en.wikipedia.org/wiki/XMOS https://en.wikipedia.org/wiki/XMOS