On 12/07/2019 01:51, DL Neil wrote: > older articles! We haven't discussed hardware. Most modern PC CPUs offer > multiple "cores". Assuming (say) four cores, asyncio is capable of > running up to four processes concurrently - realising attendant > acceleration of the entirety.
Just to pick up on this point because I often see it being cited. The number of concurrent processes running to achieve performance gain is only very loosely tied to the number of cores. We ran concurrent processes for many years before multi-core processors were invented with significant gains. Indeed any modern computer runs hundreds of "concurrent" processes on a small umber of cores and the OS switches between them. What the number of cores affects is the number of processes actually executing at the same time. If you just want to chunk up the processing of a large amount of data and run the exact same code multiple times then there is no point in having more than the number of cores. But if your concurrent processes are doing different tasks on different data then the number of cores is basically irrelevant. And especially if they are performing any kind of I/O operations since they are likely to be parked by the OS for most of the time anyway. Of course, there is a point where creating extra processes becomes counter-effective since that is an expensive operation, and especially if the process will be very short lived or only execute for tiny lengths of time (such as handling a network event by passing it on to some other process). But for most real world uses of multiprocessing the number of cores is not a major factor in deciding how many processes to run. I certainly would not hesitate to run 10xN where N is the number of cores. Beyond that you might need to think carefully. In Sydney's scenario is sounds like the processes are different and explicitly halt to perform I/O so the cores issue should not be a problem. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
