flowbase VS Vrmac

I see a lot of potential in pipeline concurrency, as seen in dataflow (DF) and flow-based programming (FBP). That is, modeling computation as pipelines where one component sends data to the next component via message passing. As long as there is enough data it will be possible for multiple components in the chain to work concurrently.

The benefits are that no other synchronization is needed than the data sent between processes, and race conditions are ruled out as long as only one process is allowed to process a data item at a time (this is the rule in FBP).

The main blockers I think is that it requires quite a rethink of the architecture of software. I see this rethink happening in larger, especially distributed systems, which are modeled a lot around these principles already, using systems such as Kafka and message queues to communicate, which more or less forces people to model computations around the data flow.

I think the same could happen inside monolithic applications too, with the right tooling. The concurrency primitives in Go are superbly suited to this in my experience, given that you work with the right paradigm, which I've been writing about before [1, 2], and started making a micro-unframework for [3] (though the latter one will be possible to make so much nicer after we get generics in Go).

But then, I also think there are some lessons to be learned about the right granularity for processes and data in the pipeline. Due to the overhead of message passing, it will not make sense performance-wise to use dataflow for the very finest-grain data.

Perhaps this in a sense parallels what we see with distributed computing, where there is a certain breaking point before which it isn't really worth it to go with distributed computing, because of all the overhead, both performance-wise and complexity-wise.

[1] https://blog.gopheracademy.com/composable-pipelines-pattern/

[2] https://blog.gopheracademy.com/advent-2015/composable-pipeli...

[3] https://flowbase.org

Couple times in the past I have implemented GPU-targeted GUI renderers, here’s an example: https://github.com/Const-me/Vrmac?tab=readme-ov-file#vector-... https://github.com/Const-me/Vrmac/blob/master/Vrmac/Draw/VAA...

2D graphics have very little in common with game engines. The problem is very different in many regards. In 2D, you generally have Bezier and other splines on input, large amount of overdraw, textures coming from users complicate VRAM memory management. OTOH, game engines are solving hard problem which are irrelevant to 2D renderers, like dynamic lighting, volumetric effects, and dynamic environment.

I think Java is only good for long-running servers.

Java doesn’t support C interop. For many desktop and embedded projects this is a showstopper, here’s an example https://github.com/Const-me/Vrmac/tree/master/VrmacVideo That C# code directly consumes V4L2 and ASIO Linux kernel APIs, and calls unmanaged user-mode DLLs like libfdk-aac.so and liba52-0.7.4.so.

Native stack and value types in C# reduce load on GC, and the number of complicated tricks required from JIT compiler. This in turn helps with startup performance. This is critical for command-line apps, and very desirable for desktop apps.

Another thing missing in Java is intrinsics support, both scalar like popcnt, bitscan, BMI, etc., and SIMD like SSE and AVX.

> Part of Panama

Most real-live C APIs are using function pointers and/or complicated data structures. Here’s couple real-life examples defined by Linux kernel developers who made V4L2 API: [0], [1] The first of them contains a union in C version, i.e. different structures are at the same memory addresses. Note C# delivers the level of usability similar to C or C++: we simply define structures, and access these fields. Not sure this is gonna be easy in Java even after all these proposals arrive.

For a managed runtime, unmanaged interop is a huge feature which affects all levels of the stack: type system in the language for value types, GC to be able to temporarily pin objects passed to native code (making copies is prohibitively slow for use cases like video processing), code generator to convert managed delegates to C function pointers and vice versa, error handling to automatically convert between exceptions and integer status codes at the API boundary, and more. Gonna be very hard to add into the existing language like Java.

> "Vector API" JEP

That API is not good. They don’t expose hardware instructions, instead they have invented some platform-agnostic API and implemented graceful degradation.

This means the applicability is likely to be limited to pure vertical operations processing FP32 or FP64 numbers. The rest of the SIMD instructions are too different between architectures. A simple example in C++ is [2], see [3] for the context. That example is trivial to port to modern C#, but impossible to port to Java even after the proposed changes. The key part of the implementation is psadbw instruction, which is very specific to SSE2/AVX2 and these vector APIs don’t have an equivalent. Apart from reduction, other problematic operations are shuffles, saturating integer math, and some memory access patterns (gathers in AVX2, transposed loads/stores on NEON).

> most of these are not done / not in a stable LTS Java release yet

BTW, SIMD intrinsics arrived to C# in 2019 (.NET Core 3.0 released in 2019), and unmanaged interop support is available since the very first 1.0 version.

[0] https://github.com/Const-me/Vrmac/blob/master/VrmacVideo/Lin...

[1] https://github.com/Const-me/Vrmac/blob/master/VrmacVideo/Lin...

[2] https://gist.github.com/Const-me/3ade77faad47f0fbb0538965ae7...

[3] https://news.ycombinator.com/item?id=36618344

Projects Panama & Valhalla seems to solve all your complaints:

> Java doesn’t support C interop. For many desktop and embedded projects this is a showstopper, here’s an example https://github.com/Const-me/Vrmac/tree/master/VrmacVideo That C# code directly consumes V4L2 and ASIO Linux kernel APIs, and calls unmanaged user-mode DLLs like libfdk-aac.so and liba52-0.7.4.so.

Part of Panama: check out the "Foreign Function & Memory API" [0]. The official docs here [1] say it is a preview in 21 but it got stabilized in Java 22 (isn't out yet).

> Another thing missing in Java is intrinsics support, both scalar like popcnt, bitscan, BMI, etc., and SIMD like SSE and AVX.

Also part of Panama: see the "Vector API" JEP [2].

> Native stack and value types in C# reduce load on GC, and the number of complicated tricks required from JIT compiler. This in turn helps with startup performance. This is critical for command-line apps, and very desirable for desktop apps.

This is part of Project Valhalla [3], they're adding value types and actual generics, among other things.

That said, most of these are not done / not in a stable LTS Java release yet. We'll see how much better it'll be compared to C# (if at all) once all of these land.

[0] https://openjdk.org/jeps/454

I have minimal experience with Rust. OTOH, programming C++ for living since 2000, with a few gaps when I used other languages like Obj-C and C#.

I agree C++ is very hard to learn if you only have experience with higher-level languages like Python and Scala. I think there’re two reasons for that.

C++ is unsafe. There’s no way around this one, it was designed that way, like C or assembly. Still, with modern toolset it’s not terribly bad. Compilers print warnings, BTW I typically ask them to treat warnings as errors to deliberately fail the build. On Windows, a combination of debug build, debug C runtime, and visual studio debugger helps tremendously. Linux compilers have these sanitizers (address, memory, thread, undefined behavior) which are comparable, they too sacrifice runtime speed for diagnostics and debuggability.

Another reason, the language itself is very complicated, especially the templates. However, just because something is in the language doesn’t mean it’s a good idea to use it. You don’t need to be familiar with that stuff unless doing something very advanced, like customizing the Eigen C++ library. Don’t follow the patterns found in the standard library: unlike your code, that library has good reasons to use that template BS. If instead of templates you do something else, C++ becomes much easier to use, and most importantly other people will still be able to read and understand your code. Another reason to avoid excessive template metaprogramming, it slows down the compiler, because template-heavy code often needs to be in headers as opposed to cpp files.

P.S. If you don’t need extreme levels of performance (defined as “approach the numbers listed in CPU specs”, the numbers are FLOPS or memory bandwidth), and you don’t need the ecosystem too much, consider C# instead of C++. Much faster than Python, often faster than Scala or Java, easy integration with C should you need that (same as Rust, much easier than Python or Java), the only downside is these ~100MB of the runtime. The reputation is weird, but technically the language and runtime are pretty good. For example, here’s a C# library which re-implements a subset of ffmpeg and libavcodec C libraries: https://github.com/Const-me/Vrmac/tree/master/VrmacVideo

BTW, I did that too for 32-bit ARM Linux on Raspberry Pi 4, back in 2020: https://github.com/Const-me/Vrmac/tree/master/VrmacVideo Unlike Uno, my implementation doesn’t use libVLC and is written mostly in C#, only audio decoders are in C++. To decode video, I directly consume V4L2 Linux kernel APIs.

Doing that for decades.

An app for Windows phone, downloaded 140k times: https://github.com/Const-me/SkyFM

Cross-platform graphics library for .NET: https://github.com/Const-me/Vrmac

Recently, offline speech-to-text for Windows: https://github.com/Const-me/Whisper

At this point, I consider side projects like that as a hobby.

I think this needs much more complexity to be useful.

For the rendering, ideally it needs GPU support.

Input needs much more work, here's an overview for Windows: https://zserge.com/posts/fenster/

Windows' Sleep() function has default resolution 15.6ms, that's not enough for realtime rendering, and relatively hard to fix, ideally need a modern OS and a waitable timer created with high resolution flag.

Here's my attempt at making something similar, couple years ago: https://github.com/Const-me/Vrmac

I agree about Python or PHP.

However, for Java or modern C#, in my experience the performance is often fairly close. When using either of them, very often one doesn’t need C++ to be good enough.

Here’s an example, a video player library for Raspberry Pi4: https://github.com/Const-me/Vrmac/tree/master/VrmacVideo As written on that page, just a few things are in C++ (GLES integration, audio decoders, and couple SIMD utility functions), the majority of things are in C#.