Function almost_equal

tests/test-opt.cpp:18–20

#define TEST_LOG(...)       printf(__VA_ARGS__)

static bool almost_equal(const double a, const double b, const double atol) {
    return fabs(a - b) < atol;
}

constexpr int64_t ne_datapoint = 2;
constexpr int64_t ne_label     = 1;