[ot][spam][crazy] Inhibition Efforts: High-Precision

[Undiscussed Horrific Abuse, One Victim of Many]

// g++ -lgmpxx -lgmp
#include <gmpxx.h>

#include <string>
#include <iostream>

#include <ctime>
#include <cerrno>

#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>


mpq_class now()
{
    struct timespec t;
    if (clock_gettime(CLOCK_MONOTONIC, &t)) {
        throw std::runtime_error(std::strerror(errno));
    }

    return t.tv_sec + mpq_class(t.tv_nsec) / 1000000000;
}

class Measurer
{
public:
    Measurer(char const * input_filename)
    : current_time(0), fd(open(input_filename, O_RDONLY))
    { }
    ~Measurer()
    {
        close(fd);
    }

    void measure()
    {
        last_time = current_time;
        last_value = current_value;

        lseek(fd, 0, SEEK_SET);
        int len = read(fd, buf, sizeof(buf));
        buf[len] = 0;
        if (buf[len-1] == '\n') { buf[len-1] = 0; }

        current_time = now();
        current_value = buf;

        if (last_time != 0) {
            time_change = current_time - last_time;
            accumulated_time += time_change * 2;
            accumulated_timevalues += time_change * (last_value +
current_value);
        }
    }

    mpq_class value()
    {
        return accumulated_timevalues / accumulated_time;
    }

    mpq_class & time()
    {
        return last_time;
    }

private:
    int fd;
    mpq_class last_time;
    mpq_class last_value;
    mpq_class current_time;
    mpq_class current_value;
    mpq_class time_change;
    mpq_class accumulated_time;
    mpq_class accumulated_timevalues;
    char buf[1024];
};

int main(int argc, char **argv)
{
    if (argc != 2) {
        std::cout << "Usage: " << argv[0] << "
filepath-containing-a-changing-number" << std::endl;
        return -1;
    }

    Measurer measurer(argv[1]);
    mpq_class start_time = now();
    while ("reading numbers from filepath") {
        measurer.measure();
        if (start_time + 1 <= measurer.time()) {
            std::cout << "Average: " << measurer.value().get_d() << std::endl;
            start_time += 1;
        }
    }
}