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| Bonita Montero <Bonita.Montero@gmail.com>: Oct 01 03:32AM +0200 Am 30.09.2021 um 22:20 schrieb Chris M. Thomasson: >> When you use wait-free or lock-free algorithms and there's no data >> you have to poll. > Why? Because you don't have to wait in the kernel. |
| RadicalRabbit@theburrow.co.uk: Oct 01 09:17AM On Thu, 30 Sep 2021 13:00:53 -0700 >these I did last year: >https://youtu.be/DSiWvF5QOiI >https://youtu.be/QFPSYsYUKBA Very impressive. Could use maybe a few more colours though. |
| "Öö Tiib" <ootiib@hot.ee>: Oct 01 04:43AM -0700 On Friday, 1 October 2021 at 04:32:18 UTC+3, Bonita Montero wrote: > >> you have to poll. > > Why? > Because you don't have to wait in the kernel. What a thread does when its input queue is empty? |
| Bonita Montero <Bonita.Montero@gmail.com>: Oct 01 02:59PM +0200 Am 01.10.2021 um 13:43 schrieb Öö Tiib: >>> Why? >> Because you don't have to wait in the kernel. > What a thread does when its input queue is empty? If it hasn't anything other to do than "waiting" for a new entry it spins. Lock-free and wait-free datastructures are idiocracy except from lock-free stacks. |
| Branimir Maksimovic <branimir.maksimovic@icloud.com>: Oct 01 01:07PM > these I did last year: > https://youtu.be/DSiWvF5QOiI > https://youtu.be/QFPSYsYUKBA An error occurred. Please try again later. (Playback ID: pHR4vgIqqp13ECHz) Learn More -- 7-77-777 Evil Sinner! |
| Branimir Maksimovic <branimir.maksimovic@icloud.com>: Oct 01 01:08PM >>> you have to poll. >> Why? > Because you don't have to wait in the kernel. If you don't spin it is not lock :P problem is that only way you don't synchronize is when things are *independent* from each other :P -- 7-77-777 Evil Sinner! |
| Branimir Maksimovic <branimir.maksimovic@icloud.com>: Oct 01 01:10PM > If it hasn't anything other to do than "waiting" for a new entry it > spins. Lock-free and wait-free datastructures are idiocracy except > from lock-free stacks. Poof. you spin me around like a record? :P -- 7-77-777 Evil Sinner! |
| "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>: Oct 01 01:04PM -0700 On 10/1/2021 5:59 AM, Bonita Montero wrote: >> What a thread does when its input queue is empty? > If it hasn't anything other to do than "waiting" for a new entry it > spins. Huh? Ever heard of a futex, or an eventcount? Take a lock-free dynamic stack into account. When its empty we can use, say, a futex to wait on it. This would be the slow-path. A fast-path is when the stack is not empty. There is a big difference between a fast and a slow path. The former is lock-free, the latter might have to wait. This even works for wait-free structures. In this case, the fast-path would be wait-free. > Lock-free and wait-free datastructures are idiocracy except > from lock-free stacks. Sure. Whatever you say Bonita. Cough.... Cough... ;^) |
| "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>: Oct 01 01:08PM -0700 On 10/1/2021 6:07 AM, Branimir Maksimovic wrote: >> https://youtu.be/QFPSYsYUKBA > An error occurred. Please try again later. (Playback ID: pHR4vgIqqp13ECHz) > Learn More That's odd. The links I posted work for me. Just checked them. Humm... |
| "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>: Oct 01 01:11PM -0700 >> https://youtu.be/DSiWvF5QOiI >> https://youtu.be/QFPSYsYUKBA > Very impressive. Thank you very much for the kind comment! :^) > Could use maybe a few more colours though. Yeah, they could. Humm... I am working on another animation using a more robust coloring algorithm for the field lines. Here is an example: https://fractalforums.org/gallery/1612-300921002353.png The coloring for that one is more dynamic. Also, I am thinking about cycling the colors during animation. |
| "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>: Oct 01 01:19PM -0700 >> She is clever. > Clever in a small area. She seems to have limited knowledge of development > and OS methodologies that arn't commonly used in Windows however. She seems to make absolute statements based on her rather narrow views. Iirc, she even said something akin to a mutex implementation must use compare-and-swap. I showed her how to do one using only exchange. Recently, in this thread she said a lock-free structure, say a lock-free stack, has to use spin-polling to wait for an empty state to become, non-empty. Well, she is wrong, yet again. |
| "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com>: Oct 01 01:20PM -0700 On 10/1/2021 5:59 AM, Bonita Montero wrote: > If it hasn't anything other to do than "waiting" for a new entry it > spins. Lock-free and wait-free datastructures are idiocracy except > from lock-free stacks. So a lock-free stack is okay with you, but not a lock-free queue? Why? |
| Bonita Montero <Bonita.Montero@gmail.com>: Oct 01 07:48PM +0200 On today's x86-CPUs there is a prefetching-instruction which loads cacheline into an cache-level chosable by a parameter for this in- struction. But I often wondered what is the most appropriate pre- fetching-distance. So I wrote a program which you can give a maxi- mum block-size and it incrementally scans this block lineary from a beginning of a block-size of 4kB up to a default of 64MB, but you can chose a larger maximum (nk, nm, ng parameter, the parame- ter can be a float). The prefetching is done with an incrementing distance, from zero (special case without prefetching) to 512 cachelines (assuming a L1- cacheline-size of 64 bytes, which fits for all x86 CPUs for decades). It first CLFLUSHs the cachelines it scans afterwards. It only scans a block if the prefetching -distance is up to one fourth of the block-size. The tailing part of the block which would give a prefetching beyond the block is scanned without prefetching to simulate a common optimization. It runs the test multiple times and takes the fastest timing. On Windows it sets it thread-affinity to CPU 0 and the priority as high as possible. On Linux it sets only the affinity. So it would be best to run the benchmark with "nice -20 ./a.out". So here's the source (C++17): #if defined(_MSC_VER) #define NOMINMAX #include <Windows.h> #elif defined(__unix__) #include <unistd.h> #include <sched.h> #include <pthread.h> 
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