I wrote these two solutions for Project Euler Q14, in assembly and in C++. They implement identical brute force approach for testing the Collatz conjecture. The assembly solution was assembled with: nasm -felf64 p14.asm && gcc p14.o -o p14 The C++ was compiled with: g++ p14.cpp -o p14 Assembly, p14.asm: section .data fmt db “%d”, … Read more
I was looking for the fastest way to popcount large arrays of data. I encountered a very weird effect: Changing the loop variable from unsigned to uint64_t made the performance drop by 50% on my PC. The Benchmark #include <iostream> #include <chrono> #include <x86intrin.h> int main(int argc, char* argv[]) { using namespace std; if (argc … Read more
Is if (a < 901) faster than if (a <= 900)? Not exactly as in this simple example, but there are slight performance changes on loop complex code. I suppose this has to do something with generated machine code in case it’s even true. 1 14 No, it will not be faster on most architectures. … Read more
I am doing some numerical optimization on a scientific application. One thing I noticed is that GCC will optimize the call pow(a,2) by compiling it into a*a, but the call pow(a,6) is not optimized and will actually call the library function pow, which greatly slows down the performance. (In contrast, Intel C++ Compiler, executable icc, … Read more
