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Peter_in_278015-Jul-20 20:08

Peter_in_2780

15-Jul-20 20:08

Rick York wrote:
Unfortunately I have half a planet to my NW so I won't be able to see unless I go somewhere else.

(It's called localisation! Poke tongue | ;-P

)

Software rusts. Simon Stephenson, ca 1994. So does this signature. me, 2012

Richard Andrew x6416-Jul-20 7:58

Richard Andrew x64

16-Jul-20 7:58

Peter_in_2780 wrote:
Unfortunately I have half a planet to my NW

Are you sure about that? The planet also rotates.

The difficult we do right away...
...the impossible takes slightly longer.

Peter_in_278016-Jul-20 14:53

Peter_in_2780

16-Jul-20 14:53

I could misquote Galileo, but...

NW is defined in a geocentric (or at least geodetic) frame of reference, fixed relative to the earth.
If I draw a line on the ground NE/SW, the vertical plane through that line approximately* bisects the earth. giving me a NW half and an SE half.
My original comment was a light-hearted way of saying I'm too far south to see the comet.

* Don't get me started on geodesy. I've spent too many hundreds of hours battling through that jungle of intractable 3D trigonometry.

</lecture>

Cheers,
Peter

Software rusts. Simon Stephenson, ca 1994. So does this signature. me, 2012

OriginalGriff15-Jul-20 20:20

OriginalGriff

15-Jul-20 20:20

I know the feeling - I have a small mountain in the way. I could drive up it, but ... lockdown and all that ... Sigh | :sigh:

"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
"Common sense is so rare these days, it should be classified as a super power" - Random T-shirt
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Daniel Pfeffer15-Jul-20 20:02

Daniel Pfeffer

15-Jul-20 20:02

It should have been visible last night in Israel. I tried to see it, but it was either lost in the twilight or lost in the haze close to the horizon. It should be higher in the sky tonight, so I'll try again.

Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.

Nelek15-Jul-20 22:12

Nelek

15-Jul-20 22:12

Nope...

Kid and me are ill... so we haven't gone out Cry | :((

M.D.V.

If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about?
Help me to understand what I'm saying, and I'll explain it better to you
Rating helpful answers is nice, but saying thanks can be even nicer.

OriginalGriff15-Jul-20 22:19

OriginalGriff

15-Jul-20 22:19

Not Covid, I hope?

Nelek15-Jul-20 22:30

Nelek

15-Jul-20 22:30

Nope, but throat / bronchia related (bacterial infection), that's why I prefer to stay home.

Thanks for asking Smile | :)

And same as you and Rick... from here I can't see it. Im in the shadow side of a tiny hill. Heck, I can't even see the new year's eve fireworks of the city Frown | :(

M.D.V.

OriginalGriff15-Jul-20 22:32

OriginalGriff

15-Jul-20 22:32

That's a relief - as someone whose had it, I wouldn't wish it on anybody ... get well soon, both of you! Rose | [Rose]

Nelek15-Jul-20 23:31

Nelek

15-Jul-20 23:31

Thanks.

OriginalGriff wrote:
I wouldn't wish it on anybody

I didn't have it, and I wouldn't wish it on anybody, and even less in me or my family. Big Grin | :-D

M.D.V.

5teveH15-Jul-20 22:31

5teveH

15-Jul-20 22:31

Clouds aren't helping! Frown | :(

That, and having to stay up until it's properly dark! Way too late for me.

jsc4216-Jul-20 0:19

jsc42

16-Jul-20 0:19

Ditto - Clouds. There is rumoured to be a bright yellow circular shiny thing above the clouds as well. Not seen any evidence of that either. Apparently, it should be visible during day time.

Multithreaded code is ridiculous

Daniel Pfeffer16-Jul-20 1:04

Daniel Pfeffer

16-Jul-20 1:04

jsc42 wrote:
Apparently, it should be visible during day time.

I've been in the UK. What is this thing you call "day"? Smile | :)

Freedom is the freedom to say that two plus two make four. If that is granted, all else follows.
-- 6079 Smith W.

5teveH16-Jul-20 1:59

16-Jul-20 1:59

jsc4217-Jul-20 0:13

17-Jul-20 0:13

Last night, there was a clear patch and I knew roughly where to look; unfortunately right across the street with light pollution from houselights, street lights etc. and only just clearing some roof tops. To the naked eye, there was just a vague small smudge like a short contrail, so I got some binoculars and it was the comet. It is the (visually) longest tailed comet that I have seen; but not as bright as Hale-Bopp was in 1997. It is well worth searching for; but I'd strongly recommend using binoculars to see it once you have located it.

honey the codewitch15-Jul-20 10:45

15-Jul-20 10:45

So as an instructional article I'm preparing code that can enqueue work items to a limited number of threads. If all the threads are busy and there's no more thread creation allowed (say you have a 3 thread limit) then one of the threads that's already busy enqueues the next message for when it's done with what it's currently processing. It schedules among the already busy threads using a round robin technique.

The whole thing works using message passing and message queues. That's how the threads communicate with each other. You can post messages to each of the threads.

The trouble with it is the complexity of it snowballs. All of the sudden I need to sync the UI which requires a whole separate layer. And then there's the interthread communication that's already complicated.

There's only so much I can fit into an article without overwhelming the reader, and to produce anything approaching a real world example requires so much complicated code that it's just silly.

Oh you did this over here? Well you need to synchronize over there. And because you did that, you need to handle it over there too, etc. It's a mess.

I really think the approach traditional computers take to preemptive multithreading is an anti-pattern. It feels like every anti-pattern I've ever encountered: The more code you need to make it work, the more code you need to make it work! You end up putting more work into it just to get to the point where you can put more work into it, and everything feels like a workaround.

Real programmers use butterflies

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Greg Utas15-Jul-20 11:05

Greg Utas

15-Jul-20 11:05

Well, I'm a longstanding member of the choir that you're preaching to. Laugh | :laugh:

If it's a thread pool, I have them share a work queue. You seem to imply that you queue messages against threads even in this case, but I doubt it. I only queue messages on a thread when it's the only one handling that kind of work.

honey the codewitch15-Jul-20 11:47

15-Jul-20 11:47

What I'm doing is I'm queuing up tasks. In the demo each time a user clicks a button (in order to queue up a new task) the code looks for an available worker. If it doesn't have one, and it can create a new one (and consequently a new thread) then it will. Otherwise if there are already a maximum number of workers created it will choose one of the busy workers to handle the next task. All of the workers do the same task. Think of this like a server application that accepts a limited number of incoming requests into a pool of workers, but will then queue requests after the limit is exceeded among the busy workers. One of them will pick it up as soon as it's finished with what it's doing. Make sense? I hope it does! Unsure | :~

ETA: Wait, I think I see what you mean by using one queue. I'll have to think on this.

Real programmers use butterflies

Robust Services Core | Software Techniques for Lemmings | Articles

Greg Utas15-Jul-20 12:22

Greg Utas

15-Jul-20 12:22

You said you round-robin, which sounds fine for what you're doing. I use work queues because items aren't lost if a thread fails, there can be queues for different priorities, and some work items may take longer than others. None of these are issues for your demo, though.

honey the codewitch15-Jul-20 12:36

15-Jul-20 12:36

Well it turns out you were right, and I could get away with a single shared server queue in this case.

Thanks for that. I guess I was just following a pattern without thinking hard enough about it.

I use queues, but not priority queues because the code is already complicated enough. I could probably implement a thread safe priority queue but it's not something i want to do. Poke tongue | ;-P

Real programmers use butterflies

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Greg Utas15-Jul-20 12:58

Greg Utas

15-Jul-20 12:58

Just to clarify. I don't use a priority queue, but a separate queue for each priority level.

honey the codewitch15-Jul-20 13:16

15-Jul-20 13:16

fair enough. Smile | :)

Real programmers use butterflies

raddevus15-Jul-20 17:29

raddevus

15-Jul-20 17:29

These issues you are discussing related to multi-threaded programming really are a problem.
It's amazing how it originally seemed like multi-threaded programming was the panacea but just became another problem. Smile | :)

Because it is so difficult a new thing has arisen: The Actor Model.
Basically, it is a way to say that you have some work that should be done and you set an Actor to doing that work. It will be done concurrently and then let you know when it is done.
In this way the threading part is abstracted away.
One of the main implementations of The Actor Model is called Akka (originally implemented on the JVM).
But now there is a .NET Version[^].

That site has a pretty good overview explanation of it all. The Actor Model really does fix a lot of what is wrong with the multi-threaded world.
Check it out and see what you think.

Member 1330167916-Jul-20 20:19

Member 13301679

16-Jul-20 20:19

That isn't the usual way of doing things; the common approach is:

1. Create pool of threads at startup (3, 5, whatever).
2. Create two queues at startup (work-queue and results-queue, using a LL or DLL queue, not an array).
3. Each thread takes the next work item from work-queue, working to completion, and posting the results to results-queue.
4. The main thread simply enqueues work items to the work-queue, and waits on the results-queue (use a semaphore here) for results.

There's no blocking involved other than the wait-on-semaphore (and wait-on-mutex for queue modification).

honey the codewitch17-Jul-20 2:09