SoA Benchmarks

• We have added a few things in our benchmarks repository: https://github.com/cern-nextgen/wp1.7-soa-benchmark
  
  • Truly contiguous SoA data layouts
  • Automatic plots comparing different SoA implementations
• Discussions about summer student Milla working on this.
• Our library now has the same performance than hardcoded SoA in the tested examples only with clang, not with gcc.
• In small examples, such as the one below, I cannot reproduce the issue (both gcc and clang are optimizing away the issue).

#include <vector>

struct SoA_Points { std::vector<float> x, y, z; };

struct S_ref { float &x, &y, &z; };

struct wrapper {
    SoA_Points soa_points;
    S_ref operator[]( int i ) {
        return { soa_points.x[i], soa_points.y[i], soa_points.z[i] };
    }
};

int main() {
    int N = 100;
    wrapper w {{ std::vector<float>(N), std::vector<float>(N), std::vector<float>(N) }};
    w[42].x = 3;  // Accesses all data members of soa_points, although only x is needed
    return 0;
}