5 ms·

Came here to say almost exactly this. C++ is fast. All the things mentioned in the article are very specific replacements of C++ standard library implementation

Came here to say almost exactly this. C++ is fast. All the things mentioned in the article are very specific replacements of C++ standard library implementations. C++ is a zero cost abstraction language, all these things could have been replaced with idiomatic C++. The fact that they were implemented in C is more of an authors language preference. Reimplementing some things might be easier in C because C is a simpler (and often more familiar) language. Idiomatic C++ may require knowledge of pretty arcane feature of already complicated language, like placement new and judicious use of references and move operators.

stephencanon 8y ago
All the things that were replaced were abstractions, which had costs. I think that there's a valid point that a lot of C++ programmers use these abstractions liberally, while sweeping the very real costs under the rug. There are also benefits to using them, of course.
lasagnaphil 8y ago
I would say C++ is more like a zero runtime-cost abstraction language (in release builds). You could achieve good release build runtime-speeds in modern idiomatic C++, but you have to trade off your compile times and Debug-build runtime-speeds for that.
- vardump 8y ago
  > I would say C++ is more like a zero runtime-cost abstraction language (in release builds). Well, other than the "zero-cost" features that increase code size. For example careless use of heavy template classes can generate a lot of code. In other words, in C++ it's very easy to generate a lot of code from seemingly innocent constructs. Instruction cache misses, page faults (and to lesser amount TLB misses) are not zero cost.
  - ben509 8y ago
    To your point, cost (or strength) should always consider size as well as time. It would be nice to have a tool that could compute the size impact of a given line.
FreezerburnV 8y ago
I said this elsewhere, but I would legitimately like to see a program like what the author wrote, written in idiomatic C++ that performs as well as what the author got to. Maybe in a comparison style like the author to show the slower C++, the faster "C with classes", and the comparable speed "idiomatic C++" or something. I feel like I see people saying that idiomatic C++ is just as fast as something, while other people say that idiomatic C++ is slower and should be replaced. I'm going to assume you can for sure write C++ using the STL to be just as fast, and would like to learn what needs to be done to get to that point so I can incorporate those techniques into my own C++ code where I might need that extra bit of performance. (I'm playing around with writing games in C++, so performance is more of a concern than an IO-heavy web server. Or I'm considering learning QT for making apps, etc.)
- mynegation 8y ago
  Author posted C version of their code[1]. As a couple of examples of how you can go back to idiomatic C++ starting from here: 1. replace all pointers by passing references to templatized vectors. On a high level of optimization they will be compiled to the same pointer arithmetic as C, but will give you type-safety on the source level. 2. Replace structs with clasess with short inlined accessors. On a high level of optimization they will be compiled to the same memory offset access 3. _If_ there is any value in making domain-specific sort generic - make it such [1] https://gist.github.com/zeux/bf847986e0474cf48f61bb5749da38e4 https://gist.github.com/zeux/bf847986e0474cf48f61bb5749da38e...

stephencanon 8y ago

All the things that were replaced were abstractions, which had costs. I think that there's a valid point that a lot of C++ programmers use these abstractions liberally, while sweeping the very real costs under the rug. There are also benefits to using them, of course.

lasagnaphil 8y ago

I would say C++ is more like a zero runtime-cost abstraction language (in release builds). You could achieve good release build runtime-speeds in modern idiomatic C++, but you have to trade off your compile times and Debug-build runtime-speeds for that.

vardump 8y ago
> I would say C++ is more like a zero runtime-cost abstraction language (in release builds). Well, other than the "zero-cost" features that increase code size. For example careless use of heavy template classes can generate a lot of code. In other words, in C++ it's very easy to generate a lot of code from seemingly innocent constructs. Instruction cache misses, page faults (and to lesser amount TLB misses) are not zero cost.
- ben509 8y ago
  To your point, cost (or strength) should always consider size as well as time. It would be nice to have a tool that could compute the size impact of a given line.

FreezerburnV 8y ago

I said this elsewhere, but I would legitimately like to see a program like what the author wrote, written in idiomatic C++ that performs as well as what the author got to. Maybe in a comparison style like the author to show the slower C++, the faster "C with classes", and the comparable speed "idiomatic C++" or something. I feel like I see people saying that idiomatic C++ is just as fast as something, while other people say that idiomatic C++ is slower and should be replaced. I'm going to assume you can for sure write C++ using the STL to be just as fast, and would like to learn what needs to be done to get to that point so I can incorporate those techniques into my own C++ code where I might need that extra bit of performance. (I'm playing around with writing games in C++, so performance is more of a concern than an IO-heavy web server. Or I'm considering learning QT for making apps, etc.)

mynegation 8y ago
Author posted C version of their code[1]. As a couple of examples of how you can go back to idiomatic C++ starting from here: 1. replace all pointers by passing references to templatized vectors. On a high level of optimization they will be compiled to the same pointer arithmetic as C, but will give you type-safety on the source level. 2. Replace structs with clasess with short inlined accessors. On a high level of optimization they will be compiled to the same memory offset access 3. _If_ there is any value in making domain-specific sort generic - make it such [1] https://gist.github.com/zeux/bf847986e0474cf48f61bb5749da38e4 https://gist.github.com/zeux/bf847986e0474cf48f61bb5749da38e...