Trust your compiler: Modern C++

(categorica.io)

32 points | by foxhill 4 days ago

6 comments

Joker_vD 34 minutes ago

Every time I see "use ranges and algorithms!" examples, I am baffled that apparently, I am supposed to find

    inline double algorithm_call(std::span<double const> xs) noexcept {
        return std::accumulate(
            xs.begin(),
            xs.end(),
            0.0,
            [](double acc, double volts) {
                auto mv  = calibrated_mv(volts);
                auto err = residual(mv);
                return weighted_square(err) + acc;
        });
    }

more readable, concise, and easier on my eyes than

    inline double raw_loop(std::span<double const> xs) noexcept {
        double sum = 0.0;

        for (double volts : xs) {
            auto mv  = calibrated_mv(volts);
            auto err = residual(mv);
            sum += weighted_square(err);
        }

        return sum;
    }

Sure, there are some algorithms in <algorithms> that I'm rather not reimplement myself, but this one is not it.

[-]

rzzzt 19 minutes ago
The first form is easier to send to 32 beefy cores or 1024 small CPUs or a Beowulf cluster or a GPU or people sitting in a room.

Panzerschrek 42 minutes ago
> exceptions are slow
There are proposals to introduce better exceptions into C++. Like this: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p07....
But until it's not in the standard, people should use std::expceted instead.
kzrdude 1 hour ago
Trust the compiler - sure - but we can't change the whole program by using -ffast-math, unfortunately, so that particular one is out.
[-]
- CoastalCoder 58 minutes ago
  I really dislike the complexity of modern C++ language specs, but does it obscure much detail about FP ops?
  TL;DR:
  A vast majority of the programmers I've worked with don't understand the nuances of FP in general, nor the various extents of IEEE-754 support in different programming languages.
  So for important numerical programming, I think clarity regarding the FP operations being performed can be crucial. I'm just unclear if modern C++ is a significant factor for that.
mike_hock 1 hour ago
> Virtual vs static polymorphism
> std::visit over std::variant<A, B, C> is lowered to a switch over the active alternative.
> In this case, layout is probably doing more work than the dispatch mechanism itself.
Very likely because last time I checked visit lowers to a virtual call.
Glandalf 1 hour ago
I’ve seen some terrible horrid nonsense from them and even the best compilers don’t use a third of the opcodes our modern CPUs boast of. Nobody understands the big compilers any more either, they’re all too huge. And soon AI will be “improving” hem too.
You want to see a beautiful compiler? Look at Plan 9’s compiler suite. A man could understand and even build on that.
sylware 1 hour ago
Are you a fool?
Another name for compilers: invisible backdoor injectors. The more complex is the syntax the more it is likely to happen... I let you guess how the "sane" syntax from c++ and similar (LOL) does fit here...
[-]
- pjmlp 58 minutes ago
  Quite funny comment on the vibe coding age.