Port 22 #6


Another chaotic swirl.

The next problem with the software port was with AppDomains. An AppDomain is an isolated environment to run a program, or a part of a program. Every program runs in an AppDomain. The main program AppDomain is created when the program starts and taken down when the program exits. You never notice it or think about it. The tricky part is when you want more than one AppDomain.

A second AppDomain is useful with add-on code as described in the last couple of posts. If you load a program add-on into the main AppDomain, you cannot get rid of the add-on without terminating the main program. By loading the add-on into a separate AppDomain, you can discard the AppDomain, and the add-on code when you are done with it. I do this to recover the memory space used by the add-on, and to protect against crashes. The add-on code tends to be more experimental and less tested than the main program code.

My art program is the only program I have that uses more than one AppDomain. So I am deep into the port to VS 2022 when I learn that AppDomain support has been removed from .Net 6. Not changed, just flat out not supported.

The next best thing appears to be the AssemblyLoadContext class. You can load the add-on dll into a separate AssemblyLoadContext. When the add-on is done running the garbage collector eventually runs and frees the space. Well that is the theory at least.

There is a known bug with AssemblyLoadContext garbage collection when it runs WPF (Windows Presentation Foundation) code. WPF creates objects for windows and other display components. Some of these objects are never released, even after the window is closed. That prevents garbage collection. At the time I was discovering these problems the recommended work-around was the ever-so-helpful “just don’t do that”. In my case, my add-ons often come with custom editors which use WPF, so the recommended “solution” is not feasible. It may have been fixed by now, but I am not in a mood to fight that battle again.

I have given up on AppDomain and AssemblyLoadContext. Computers have so much memory these days, that worrying about add-on code memory use is a misplaced concerned. The memory used by the add-on program code is insignificant compared to the memory used for a single high resolution picture. As for program code defects, I just need to be more careful.

Port 22 #5


Another exotic formula. Looks like something mixing or flowing.

Continuing my VS2022 porting story. My first attempt to upgrade failed, a few months later I tried again, this time with more realistic expectations of the time commitment.

I had some success porting some smaller, and some not so small programs to the new framework. I did the first few slowly and carefully. Making sure I understood all of the differences. I compiled a detailed checklist, and the other programs ported smoothly. Eventually I started on the Art program, and had some initial success. The bulk of the program was up and running. Then I hit a wall. Two problems, both related to the dynamic, in-program compile and run add-on code feature.

The Roslyn compile needs a list of dlls used by the program code being compiled. The list contains both the dlls with that I wrote and dlls that contain the .Net 6 library features that I use. In the past it was easy to find the library dlls. If I guessed wrong, then the compiler error message would tell me which type (object) I missed, and the documentation told me the dll that has the missing type. The documentation is not reliable with .net 6. Adding the dll listed in the documentation does not find the missing type. Also, VS2022 introduces two types of dlls (with identical names), one for compilation and one for execution. Grabbing the wrong one causes failure, but only some of the time.

Eventually I made a list of all dlls included with .net 6 and fed that list to the compiler. It works. Since over 90% of them are not used, I know it slows down the compile step. That slowdown is in computer time, I do not notice it. In a whole lifetime, that less than a second delay each time I compile an add-on will not add up to the time already spent trying to debug the problem. This is a good example where trying to be efficient, pick out exactly the dlls I use, turns out to be very inefficient.

Port 22 #4


Here is a test of an escape time fractal with an exotic generating formula.

Now this discussion goes deep into the weeds of programming and development tools. Feel free to skip it if you are just here for the pictures.

Often a fractal program will have a way to add new code to implement formulas and other ideas that the base program does not provide. Today’s picture is an example. Typically this is done in a custom scripting language.

Such a scripting language is not as efficient as a compiled program, and does not have all the features of a full general purpose programming language. I was too lazy to invent a new language, and then have to invest in debugging and optimizing it to do the things I want to do as fast as I want it to. Especially when I was already working in a perfectly good and familiar language, C#. So, in my program the scripting or add-on language is C#.

One of the core elements of VisualStudio is the Roslyn Compiler for C# and other languages. Roslyn is also a component of the .Net framework. You can use it to compile and execute new code within a program. I can write fractal or generative art hacks in C# code, and build and run optimized code without leaving the executing program.

You may ask why bother? Since I have the source code, I could just exit, modify the source code, compile and run. Several reasons, the first is probably the loss of “momentum” going through that stop, edit, compile, run cycle. There is also reproducibility, if I save the ‘recipe’ for an image, and then change the core program, the recipe may produce a different image, or fail entirely. Instead, the custom code changes are saved as part of the recipe. I can create a large number of variations, without ever changing the core program, and they have a high probability of working in the future.

Port 22 #3


Next thing to verify, small variations in the basic formula and zooming.

This is not a programming blog, and I should not bore you with programming minutiae. But I have nothing else to talk about right now.

Visual Studio is the development environment. C# is the programming language I use. .Net is a framework, or a set of libraries. Visual Studio 2022 comes with C# 10, and .net 6.0.

I installed VS2022 several months ago. These tools are for the most part supposed to be backwards compatible. I could not build any of my programs, which were built on .Net 4.8. The framework was properly installed (and re-installed several times) but VS2022 could not find it, and asked me to participate in an infinite loop of un-install and reinstall the framework.

In the past, Visual Studio always provided tools to easily move your programs from the older framework to the newer version. That is not provided this time, you need to do the port manually. As there are no significant benefits to running the old framework on the new IDE, and I did not have the time to invest in learning the new framework, and the product was still in ‘preview’ mode, I gave up.

Port 22 #2


The next goal in the port was to make some simple changes to the coloring algorithm.

I am actually much further along on the software port than these posts would indicated. I had this one queued up to publish a month ago, and generated by the program a few weeks prior to that.

I am falling into the trap where if I do not publish something daily then it gets to be a month or more between posts.