source: doc/theses/thierry_delisle_PhD/code/utils.hpp @ c921712

#pragma once

#include <cassert>
#include <cstddef>
#include <atomic>
#include <chrono>
#include <fstream>
#include <iostream>

#include <unistd.h>
#include <sys/sysinfo.h>

// Barrier from
class barrier_t {
public:
        barrier_t(size_t total)
                : waiting(0)
                , total(total)
        {}

        void wait(unsigned) {
                size_t target = waiting++;
                target = (target - (target % total)) + total;
                while(waiting < target)
                        asm volatile("pause");

                assert(waiting < (1ul << 60));
        }

private:
        std::atomic<size_t> waiting;
        size_t total;
};

class Random {
private:
        unsigned int seed;
public:
        Random(int seed) {
                this->seed = seed;
        }

        /** returns pseudorandom x satisfying 0 <= x < n. **/
        unsigned int next() {
                seed ^= seed << 6;
                seed ^= seed >> 21;
                seed ^= seed << 7;
                return seed;
        }
};

static inline long long rdtscl(void) {
    unsigned int lo, hi;
    __asm__ __volatile__ ("rdtsc" : "=a"(lo), "=d"(hi));
    return ( (unsigned long long)lo)|( ((unsigned long long)hi)<<32 );
}

void affinity(int tid) {
        static int cpus = get_nprocs();

        cpu_set_t  mask;
        CPU_ZERO(&mask);
        int cpu = cpus - tid;  // Set CPU affinity to tid, starting from the end
        CPU_SET(cpu, &mask);
        auto result = sched_setaffinity(0, sizeof(mask), &mask);
        if(result != 0) {
                std::cerr << "Affinity set failed with " << result<< ", wanted " << cpu << std::endl;
        }
}

static const constexpr std::size_t cache_line_size = 64;
void check_cache_line_size() {
        std::cout << "Checking cache line size" << std::endl;
        const std::string cache_file = "/sys/devices/system/cpu/cpu0/cache/index0/coherency_line_size";

        std::ifstream ifs (cache_file, std::ifstream::in);

        if(!ifs.good()) {
                std::cerr << "Could not open file to check cache line size" << std::endl;
                std::cerr << "Looking for: " << cache_file << std::endl;
                std::exit(2);
        }

        size_t got;
        ifs >> got;

        ifs.close();

        if(cache_line_size != got) {
                std::cerr << "Cache line has incorrect size : " << got << std::endl;
                std::exit(1);
        }

        std::cout << "Done" << std::endl;
}

using Clock = std::chrono::high_resolution_clock;
using duration_t = std::chrono::duration<double>;
using std::chrono::nanoseconds;

template<typename Ratio, typename T>
T duration_cast(T seconds) {
        return std::chrono::duration_cast<std::chrono::duration<T, Ratio>>(std::chrono::duration<T>(seconds)).count();
}