It's been one of the things that have most strongly shaped the evolution of the language and the library, for both good and bad, so absolutely, it is very much well known.
You might say that compilation time is nothing.. But it is C++, compilation time has a huge impact on big codebases.
My point stands. The performance trade-offs you're paying for with various C++ features are extremely well understood, and better documented for C++ than most languages.
That doesn't mean there aren't surprises here and there, and obviously there are compiler difference, but the point was that the language is designed so that these tradeoffs are known and documented and for the most part comes as a surprise to people mostly when they don't know the language very well.
It is not a surprise that you can improve on things like std::vector by rolling your own that does exactly what you want; for starters if you know your requirements chances are you can speed up initialization, because you don't need to abide by standard semantics. For starters, if you know you're going to assign a fixed number of elements, you don't need to track size and capacity, and you can often avoid the need for bounds checking.
As for compilation time, that too is very much a matter of paying for what you're using. You can choose to disable debug info, you can choose to not include headers that are bound to result in lots of time spent on parsing templates.
That he's not using many advanced features is irrelevant; his starting point very much had made trade-offs in using functionality that comes with known costs.
I agree with you about the title, but I also think that if you fix the title the author is making a good point. It's not groundbreaking, but the move "down" from C++ to C does run parallel with the move from more general purpose to more special purpose, in a lot of ways. C dominates embedded after all.
A few years ago for debugging purposes I wanted to hexdump a large amount of data. Turns out that the standard hexdump tool was pretty slow at it, writing a simple C utility that would format the dump "by hand" instead of using printf was about an order of magnitude faster. You have fully static code instead of the interpreted format string, you can unroll all the formatting, you don't have to rewrite the characters that don't change in every line (spaces, delimiters etc...). It's lightning fast but of course not very flexible.
Yes, of course it is. That's why I took it as an example. Since I work on RealTime systems I usually have to use plain 'write' instead. But that is because 'printf' is an incredibly complex function, not because 'C is slow'.
- printf is a standard function in C's stdlib.
- Because of the nature of the function (using a special purpose format strings and varargs instead of some kind of generic system) the function can't really be aggressively optimized and inlined without compiler magic. This limitation is caused by C's own limitations when it comes to generic programming and type introspection, printf needs to be told explicitly through a "side-channel" (the format string) what types to expect because C lacks the infrastructure to do that by itself. It also means that you can't extend the function for custom types and that you can't type-check the parameters without compiler magic.
- Even though some compilers do implement special magic around printf to perform more aggressive optimizations (like replacing it with "puts" if there's no formatting going on for instance) it's still generally trivial to beat its performance in non-trivial case with handwritten code.
Given all of the above I would say that makes this particular corner of C rather slow indeed. Or at least slower than it might be compared to an hypothetical language that made it easier to optimize string formatting.
int x;
cout << x;
#include “studio.h”
int x;
printf(“%d”, x);
(The #include is essential. With it, the compiler can know what printf does, and, in theory, optimize it to a int-to-string conversion and a puts system call. Without it, it cannot, because it doesn’t know what the printf function does (in this case, it is easier to generate fast code for the compiler if it doesn’t have the source available than when it would see source code for a function called printf)
Utterly pedantic: no. As given, both are undefined behavior, and it is trivial for a compiler to discover that.
That is true for certain format strings (containing only %s or %c conversions), but for %d GCC and Clang don't seem to want to call a print_int function, possibly because there is none: https://gcc.godbolt.org/z/rltFse
ios::sync_with_stdio(false);Or if performance is basically your only goal (HFT) then you just need to spend this time on a lot of parts of your code.
But then in 99% of code it's a waste of time.
In that case the author is showing what has been widely known by C++ developers for decades. In fact, the "don't use the STL because it's slow" is a mantra which, along with the old "replace STL's default allocators with your customized ones", is repeated ad nauseum in gamedev circles.
However I'd also say this is something already well known by most C and, particularly, C++ developers. Yes, you can get better performance by reimplementing much of what C++ gives you, and that is typical of writing C code instead of C++. But there's a fair bit of productivity trade off in doing so.