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You will never have true realtime. There are always unexpected delays, from cache misses to virtual memory paging operations. The systems getting closest to RT are the old ones: The first machine I laid my hands on was a 1976 design 16-bit mini (i.e. the class of PDP-11): It had 16 hardware interrupt levels - that is, 16 complete sets of hardware registers, so when an interrupt occured at a higher level than the one currently executing, the register bank was switched in an the first instruction executed 900 ns after the interrupt signal was received. That was certainly impressive in 1976, but the CPU was hard logic throughout, with no nasty pipelines to be emptied, no microcode loops that had to terminate, usually you had no paging or virtual memory. That got you close to RT. You won't see anything that compares today, even without GC.
In those days, people got shivers from the though of writing any system software in any high level language. Lots of people shook their heads in disbelief over Unix written in K&R C: It could never work, could never give good enough performance. I have saved a printout of a long discussion from around 1995, when NetNews was The Social Media: This one guy who insisted, at great length, that high level languages was nothing but a fad that would soon go away; they will never give high enough performance. (In 1995, he didn't get much support from the community, but he never gave in to the pressure.)
Using a high level language takes you one step away from RT. Using a machine with virtual memory is another step (even if your program is fixed in memory - the OS may be busy managing memory for other processes, with interrupts disabled). Dependency on pipelines and cache hit rates is yet another step. If you require really hard RT, you must stay away from such facilities - probably from any modern CISC CPU.
You probably do not have hard RT requirements; you can live with a cache miss, or the OS updating page table for other processes. You should design your code to be able to handle as large random delays as possible. Networking guys know the techniques, like window mechanisms and elastic buffers. If you do things the right way, I am not willing to believe that a modern multi-GHz six-core CPUs ability to run a VST plugin sufficiently close to RT is ruined by the CRT GC!
I grew up with high level languages, but knowing that RT "had to" be done in assembly. But soon I also learned how smart optimizing compilers can be, and gave up my belief in assembly. I much longer thought that I would have to manage the heap myself, if performance was essential. I switched to C#, where it isn't an option, and then came across a fairly good description of the CLR CG (in "CLR via C#"). Again and again I said to myself: Hey, that's a neat trick! or: I never though of that in my heap management! ... Twenty years earlier I concluded that a compiler is far smarter than I am in generating code. Now Irealized that CLR is far smarter than I am in managing memory. And I never had any performance problems in C#.
You sure can manage memory yourself, even in C#. As a graduate student I was a TA helping freshmen through their first programming course. The "hard" engineering disciplines still used Fortran, the rest had switched to Pascal. Exercises were common to both languages, except for one: The Pascal version was a linked list problem. One EE student was offended: Why can't we learn about this pointer stuff, like all the others? I gave her an introduction to pointers ... and next week she returned with a solution to linked list problem, written in Fortran, the heap as a big 2D array, pointers being integer indexes of the next object (i.e. array row) in the list.
You can do something similar: At program startup, allocate a large byte or integer array, cast any slice of the array into any class when referencing an object, cast from an arbitrary object to an array slice when allocating or modifying an object. As if you were writing your own memory manager in assembly language (except then you wouldn't have to do all that casting). I am sure that you could find a lot of smart strategies in the description of the CLR memory management 
For being a little more serious: I would very much like to see a C++ solution and a C# solution side-by-side, everything being identical with the exception of the heap management. And then have a demonstration that the C# solution has untolerable hickups every time the GC makes a round of cleanup. I doubt that I will ever have that experience.
What probably would happen is that in the rewriting from C# to C++, experience from the C# work allows you to write better, more efficient code in C++ - improvements that might have been carried back to the C# version, but it isn't. So there are far more differences in the two alternatives than just the heap management.
One example showing this effect: When IBM developed its first RISC chip, the 801, at a conference they presented a paper on the speed increase made possible by the large register file of the 801, requiring new compiler optimization techniques. Then, more or less as a side remark, the presenter told that they had carried back those optimzation methods to the compiler for the 360/370 architecture, and gained a 30% speed increase ... without any extended register file. But that was only an informal experiment, so for the rest of the presentation, all performance gains on the RISC was ascribed to the RISC architecture, including the 30% which could be obtained on a quite different CISC architecture.
So if a C++ implementation with "handwritten" heap management runs more smoothly than a C# one with automatic heap management, I would suspect that it has more to do with "new optimization techniques" until I have compared the two, line by line, as well as the compiler options.
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See my other reply where i said in this case i don't care about it being technically an RTOS
I care about being able to play live music with it
When I was growin' up, I was the smartest kid I knew. Maybe that was just because I didn't know that many kids. All I know is now I feel the opposite.
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All I am saying is: If you can't play your music, it is not the fault of the GC. I am not willing to believe that.
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LOL
yeah dude, it is.
i've tested it.
and i've tested it again by using the critical region feature of .NET 4 to suspend the GC
so you can believe whatever you want.
I'll believe my tests, thanks.
When I was growin' up, I was the smartest kid I knew. Maybe that was just because I didn't know that many kids. All I know is now I feel the opposite.
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Yes. As a matter of fact. I'm saying that. It's one of the reasons I abandoned it and went back to writing them in C++
Maybe if you have an 8 core monster the lag on the GC won't kill it. But on my little I5-2700 it certainly does
When I was growin' up, I was the smartest kid I knew. Maybe that was just because I didn't know that many kids. All I know is now I feel the opposite.
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Hi!
Let me share with you the techniques we have used to go around some of the drawbacks you describe.
Our solution is consuming a LARGE amount of UDP traffic (MPEG2 streams) - over 200Mbps of data. It is also performing some heavy DSP processing and it taxes the garbage collector heavily.
Being UDP and with no retransmission protocol available - we are very sensitive to reading the data on time if we want to keep the quality of the video streams high. Reading the UDP traffic with managed code was a disaster.
Basically, we are taking advantage of the fact that an unmanaged thread is NOT suspended during garbage collection.
1. We used C++/CLI to write the multicast UDP reader code inside a non-managed class. We ensure that the CLR support is disabled for the .cpp file implementing the code that we don't want to be interrupted during garbage collection. This makes sure that the code is compiled to native code, otherwise it may get compiled to IL code and the unmanaged thread may be blocked once it transitions to IL space. Even if using the unmanaged pragma, the compiler creates managed thunks around the unmanaged code and we want to avoid IL completely for this generated code. The unmanaged thread that is reading the UDP traffic (using RIO for higher performance) runs inside this class. Note that unfortunately we can't take advantage of the .Net framework in this class, so we rely on Boost.
2. We keep the unmanaged code as simple as possible, basically we loop reading UDP packets and enqueue them. However, we make sure that we use a lockless queue for this purpose (we use a Boost lockless queue). This is vital because there will be a managed thread consuming the queue, bridging the data onto the managed world. This consumer thread will be suspendend during GC activity and we don't want the thread to be suspended while holding a lock for the queue (otherwise the unmanaged thread may block contending for the lock). Another plus is that using a lockless queue, we become immune to thread priority inversion, so we can boost the producer thread priority to the highest level possible.
3. Using C++/CLI we produce a .net friendly class. This class owns and instantiates the unmanaged class, and also implements the managed queue consumer thread. (It can seamlessly consume the Boost lockless queue and expose the unmanaged memory (the udp packets) in a managed friendly way. Now, no matter if the managed world is suspended, the unmanaged thread will keep filling the lockless queue.
We also tuned some relevant NIC parameters, and by using these techniques, we can proudly say we are losing less than 0.001% of the packets (when we were losing around 8% of the packets with our initial, purely-managed solution).
I think I may actually write an article (my first) on this technique. It may be useful to others.
Feel free to contact me if you want to try this approach!
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Yeah, that's the Microsoft recommended way I think, either that or using classic unmanaged C++ and just calling into that but marshalling can be a problem depending on performance needs, so mixed mode/managed may be the way to go. The other option would probably be to write a custom marshaller for those methods, if you really don't want to mix manage/unmanaged code in the same assembly
I'd share it, because people may not be aware of the technique.
As far as the UDP I'm curious if you use any sort of QOS method on your UDP streaming?
uTP does, but to the opposite ends and goals as yours, although using something like it might smooth playback during network traffic spikes
When I was growin' up, I was the smartest kid I knew. Maybe that was just because I didn't know that many kids. All I know is now I feel the opposite.
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so I took someone's advice here about the way i declare tuples. Redid everything using named tuples and now my code only works with .NET core.
FML.
Luckily i won't be releasing officially for like a year.
When I was growin' up, I was the smartest kid I knew. Maybe that was just because I didn't know that many kids. All I know is now I feel the opposite.
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I just checked, and once I set my project to .NET 4.7.2 instead of 4.6.2 it compiled and worked perfectly:
private void FrmMain_Load(object sender, EventArgs e)
{
if ((ModifierKeys & Keys.Shift) == 0)
{
this.LoadLocation();
}
var loc = GetLocation("some address");
Console.WriteLine($"Lat: {loc.x}, Long: {loc.y}");
}
private (double x, double y) GetLocation(string address)
{
return (100, 100);
}
Sent from my Amstrad PC 1640
Never throw anything away, Griff
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
AntiTwitter: @DalekDave is now a follower!
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string interpolation != named tuples
(int First, int Last) intRage = (1,2);
like that.
Yeah, i think 4.7.2 might work. i'm installing now
When I was growin' up, I was the smartest kid I knew. Maybe that was just because I didn't know that many kids. All I know is now I feel the opposite.
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The interpolation is just there for usage demo:
(int x, int y) v = (100, 200);
Console.WriteLine($"{v.x}, {v.y}");
Works fine as well.
Sent from my Amstrad PC 1640
Never throw anything away, Griff
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
AntiTwitter: @DalekDave is now a follower!
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ahh
well, it's not working in my .NET 4.7.1 target in VStudio. Only in .NET core 2.1+ target
which means it's using a newer version of the C# compiler
When I was growin' up, I was the smartest kid I knew. Maybe that was just because I didn't know that many kids. All I know is now I feel the opposite.
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If its just two unnamed ints, return an array. If the two ints need names, create a class with two properties.
Will work with any framework.
Bastard Programmer from Hell 
If you can't read my code, try converting it here[^]
"If you just follow the bacon Eddy, wherever it leads you, then you won't have to think about politics." -- Some Bell.
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There's lots of nested data. like this
(int Accept, ((char First, char Last)[] Ranges, int Destination)[] Transitions, int[] PossibleAccepts)[]
I'm avoiding polluting the namespace with types the end user-dev will never touch.
Most of these are strictly for parse tables - machine generated data that will never be touched by human hands, or perused by human eyes.
If I start polluting the namespace with types, I've in a way, broken encapsulation. Now, i can make these types private, but then if you ever WANT to see or debug or peruse these tables, you basically can't.
Tuples give me a really nice compromise. They avoid polluting the namespace, and are still exposed enough that someone can use them and alter them if they really want to.
Keep in mind, this is not a general guideline for writing code - this is a very special case.
When I was growin' up, I was the smartest kid I knew. Maybe that was just because I didn't know that many kids. All I know is now I feel the opposite.
modified 14-May-19 10:28am.
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It was probably a Russian meaning "Tupolev" 
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It is language feature and not Framework related...
Using C# 7.0 you have tuples, using 7.1 you have named tuples...
All you need is to configure your project (the easiest way is to pick a framework compiles with those features by default, like 4.7.2)...
"The only place where Success comes before Work is in the dictionary." Vidal Sassoon, 1928 - 2012
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As you were tying that i did some research to find out which C# versions ship with which MS devstudio targeting packs.
And you're right, but i don't have those installed. Remedying now.
When I was growin' up, I was the smartest kid I knew. Maybe that was just because I didn't know that many kids. All I know is now I feel the opposite.
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If you are using VS 2017, you can add named tuples via nuget: NuGet Gallery | System.ValueTuple 4.5.0[^]
Sent from my Amstrad PC 1640
Never throw anything away, Griff
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
AntiTwitter: @DalekDave is now a follower!
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it doesn't let the C# compiler use implicit naming though does it? that's a *language* feature that came AFTER c# 7.0. It's not a framework feature, although the ValueTuple type framework feature is usd by the compiler to support this.
When I was growin' up, I was the smartest kid I knew. Maybe that was just because I didn't know that many kids. All I know is now I feel the opposite.
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Not sure - I'm using 2019 at the moment (I removed 2015 and 2017 when I installed the latest, just keeping 2013 in case ...)
Sent from my Amstrad PC 1640
Never throw anything away, Griff
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
AntiTwitter: @DalekDave is now a follower!
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I'm still on 2017, as i like to wait until many other devs have updated before i do.
When I was growin' up, I was the smartest kid I knew. Maybe that was just because I didn't know that many kids. All I know is now I feel the opposite.
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I have to say it's been pretty stable so far - I've had fewer problems with it than with 2017 (which is why I didn't move to that or 2015). It's slower than 2013 to compile, but seems to load slightly faster.
And I like some of the UI addins such as "always visible" reference counts - even if some of the "improvements" it suggests are contradictory. Fuzzy searches are handy as well, as is Intellicode, when you get used to it (Intellisense on steroids).
Sent from my Amstrad PC 1640
Never throw anything away, Griff
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
AntiTwitter: @DalekDave is now a follower!
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I get refcounts in VS2017. The rest is new i think.
the reason i don't switch is it's harder for me to share code. not really a stability thing. A lot of devs are somewhat conservative about updating, so i try to hold off a little myself, so that we can exchange project files, like I can post them here and more people can use them without having to fiddle with recreating an older project file from the source code.
When I was growin' up, I was the smartest kid I knew. Maybe that was just because I didn't know that many kids. All I know is now I feel the opposite.
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