I'm making a game in Node.js with a C++ component. This C++ component is invoked often (as a subprocess) and is a bottleneck. Thus, I hardcoded its assets as const arrays to make it run faster.
However, I noticed that my C++ code takes a long time to compile. Following is a demonstration of the problem:
#include <iostream>
#include <vector>
#define d 3,
#define _ 999,
// an array holding some game assets
const std::vector<std::vector<std::vector<int>>> STRUCTURES {
{ // you should make 80 copies of this paragraph before benchmarking
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
},
};
int main(int argc, char **argv){
// prevent optimizer from ignoring the big array
std::cout << STRUCTURES.size() << std::endl;
return 0;
}
If you repeat the middle paragraph 80 times, it'll be comparable in size to my C++ program. I compile with g++ test.cpp -O3 and it takes 36 seconds to compile. I don't understand why this is so slow. Is there something I can change to make it compile much faster?
The solution, as suggested by Barmar and Sam Varshavchik, is to avoid std::vector.
There are too many vectors and the optimizer is taking a lot of time to deal with that. std::array can be used instead. For this sample, that means:
#include <iostream>
#include <vector>
#include <array>
#define d 3,
#define _ 999,
// an array holding some game assets
const std::vector<std::array<std::array<int,37>,37>> STRUCTURES {
{{ // you should make 80 copies of this paragraph before benchmarking
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ d d d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ d d d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ d d d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ d d d d d d d d d d d _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ d d d d d d d _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
{ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ },
}},
};
int main(int argc, char **argv){
// prevent optimizer from ignoring the big array
std::cout << STRUCTURES.size() << std::endl;
return 0;
}
Notice that I still used a single std::vector for the outermost dimension. This does not present a significant overhead when compiling.