libdpf/examples/evaluation/eval_point.cpp

#include <cstdint>
#include <iostream>

#include "dpf.hpp"

/// One input. `*eval_point` is that party's share of output 0.
/// Reconstruct with `dpf::reconstruct` (leaf outputs are subtractive).
int main()
{
    const std::uint8_t alpha = 42;
    const std::uint64_t beta = 7;
    auto [k0, k1] = dpf::make_dpf(alpha, beta);
    using key_t = dpf::unwrap_party_key_t<std::decay_t<decltype(k0)>>;

    //! [eval-point]
    auto y0 = *dpf::eval_point(k0, alpha);
    auto y1 = *dpf::eval_point(k1, alpha);
    std::uint64_t opened = dpf::reconstruct(y0, y1);
    //! [eval-point]
    if (opened != beta)
    {
        std::cerr << "eval_point at the programmed input\n";
        return 1;
    }

    auto off0 = *dpf::eval_point(k0, std::uint8_t{41});
    auto off1 = *dpf::eval_point(k1, std::uint8_t{41});
    if (dpf::reconstruct(off0, off1) != 0)
    {
        std::cerr << "eval_point off the programmed input\n";
        return 1;
    }

    //! [eval-point-memo]
    // One mutable memoizer per key. Nearby points reuse the common prefix.
    auto path0 = dpf::make_basic_path_memoizer<key_t>();
    auto path1 = dpf::make_basic_path_memoizer<key_t>();
    for (int x = 40; x <= 44; ++x)
    {
        auto s0 = *dpf::eval_point(k0, static_cast<std::uint8_t>(x), path0);
        auto s1 = *dpf::eval_point(k1, static_cast<std::uint8_t>(x), path1);
        std::uint64_t got = dpf::reconstruct(s0, s1);
        std::uint64_t expect = (static_cast<std::uint8_t>(x) == alpha) ? beta : 0;
        if (got != expect)
        {
            std::cerr << "path memoizer\n";
            return 1;
        }
    }
    //! [eval-point-memo]

    std::cout << opened << "\n";
    return 0;
}