Comment by jstimpfle
1 day ago
Trust me, I know more C++ than most or all of my peers (working two jobs simultaneously), and I know a million ways that C++ features suck. Also standard library and containers. If you want I'll point out the ways in which std::deque, and even std::map, std::unordered_map, even std::vector (!) suck. IMO, just don't do it.
The standard library implements really do suck (in some cases), but this should be separated from C++ (the language). Even the standard splits the language grammar from the standard library cleanly.
You can't really separate the two, firstly because some parts of the standard library interact directly with the language's syntax (e.g. <initializer_list>), and secondly because the language standard dictates things about the behavior of the standard library that limit implementation options.
For example, the standard says that adding elements to an <unordered_map> is not allowed to invalidate references to keys or elements within the map. That makes it impossible for any standards-compliant C++ implementation to use a high-performance implementation in which keys and elements are stored contiguously in a flat array.
Your map example only concerns the standard library, not the language.
3 replies →
Which sucks... unless you really need reference stability.
1 reply →
and even std::map, std::unordered_map, even std::vector (!) suck
It's really hard to take your comment serious because of generalization like this. Maybe they're not usable for your particular usecase but that doesn't mean they suck. Just like there's a 'million' ways that C++ sucks in your book, there's a reason there's millions of lines of code out there where these containers are valid usecases and hence work without issues whatsoever nor a need to replace them with something else.
std::map and std::unordered_map are just unbelievably shitty implementations. The former is a red-black tree, which in my entire programming career I have needed to reach for like... twice? It's just not the right container for almost any problem you have, yet it's the one that gets the short, sweet name. The latter is a bucket-based hashmap, which is about the worst kind of hashmap that can be built. On top of that, their APIs are also really annoying to use compared to, say, Python or Rust's implementation. At least C++20 finally added a simple contains method, but something like setdefault is just a chore to get implemented.
Pretty much the only collections I use are:
1. arrays
2. linked lists
3. hash tables
4. simple binary trees
They're not useable for anything serious, i.e. high throughput, low frequency, massively concurrent work. In other words, most of the things for which you shouldn't better have chosen a different language in the first place.
They're also unusable by the way because of ergonomic and software architecture factors, such as bad modularity, terrible compile times, unreadable error messages, unreadable symbol names...
Yes that is overgeneralizing a little bit but it's largely true.
The problem is typically not the containers themselves but all the other bad decisions that they push you to make in order to work around their "small issues".
The huge problem is that these containers can get you started quickly, i.e. leetcode type stuff and single threaded stuff, but at some point you'll realize your architecture ended up completely in the wrong place because of that.
If you haven't been thinking deeply about memory management and concurrency, you won't be able to understand, no offense meant. I've just fixed another subsystem that was completely overwhelmed, seeing 8x bandwidth gains already on a small testsystem, but the factor is basically unbounded when moving to bigger systems, when it's about contended vs uncontended.
> anything serious, i.e. high throughput, low frequency, massively concurrent work
Why is only 'high throughput, low frequency, massively concurrent work' considered 'serious'?
11 replies →
If you haven't been thinking deeply about memory management and concurrency, you won't be able to understand, no offense meant
I do think about that, when needed. My point is that these containers can be 'good enough' in places where it doesn't really matter, not that they're always the go-to thing. E.g. I really don't see any issue using a map as part of a configuration type of object which gets read from args or json and which only gets used once at application start.