poseidon2_quad_internal_terminal_relation.hpp

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#pragma once
#include "barretenberg/crypto/poseidon2/poseidon2_params.hpp"
#include "barretenberg/crypto/poseidon2/poseidon2_quad_params.hpp"
#include "relation_types.hpp"
 
namespace bb {
 
template <typename FF_> class Poseidon2QuadInternalTerminalRelationImpl {
  public:
    using FF = FF_;
    using QuadParams = crypto::Poseidon2QuadBn254Params;
 
    static constexpr std::array<size_t, 4> SUBRELATION_PARTIAL_LENGTHS{ 7, 7, 7, 7 };
 
    template <typename AllEntities> inline static bool skip(const AllEntities& in)
    {
        return in[AllEntities::EntityId::q_poseidon2_quad_internal_terminal].is_zero();
    }
 
    template <typename ContainerOverSubrelations, typename AllEntities, typename Parameters>
    void static accumulate(ContainerOverSubrelations& evals,
                           const AllEntities& in,
                           const Parameters& /*params*/,
                           const FF& scaling_factor)
    {
        using Accumulator = std::tuple_element_t<0, ContainerOverSubrelations>;
        using CoeffAcc = typename Accumulator::CoefficientAccumulator;
 
        const auto w_l = CoeffAcc(in[AllEntities::EntityId::w_l]);
        const auto w_r = CoeffAcc(in[AllEntities::EntityId::w_r]);
        const auto w_o = CoeffAcc(in[AllEntities::EntityId::w_o]);
        const auto w_4 = CoeffAcc(in[AllEntities::EntityId::w_4]);
 
        const auto w_l_shift = CoeffAcc(in[AllEntities::EntityId::w_l_shift]);
        const auto w_r_shift = CoeffAcc(in[AllEntities::EntityId::w_r_shift]);
        const auto w_o_shift = CoeffAcc(in[AllEntities::EntityId::w_o_shift]);
        const auto w_4_shift = CoeffAcc(in[AllEntities::EntityId::w_4_shift]);
 
        const auto q_l = CoeffAcc(in[AllEntities::EntityId::q_l]);
        const auto q_r = CoeffAcc(in[AllEntities::EntityId::q_r]);
        const auto q_o = CoeffAcc(in[AllEntities::EntityId::q_o]);
        const auto q_4 = CoeffAcc(in[AllEntities::EntityId::q_4]);
 
        const auto q_sel = CoeffAcc(in[AllEntities::EntityId::q_poseidon2_quad_internal_terminal]);
 
        // Square the degree-1 pow5 input in the coefficient basis before promoting -- see
        // UnivariateCoefficientBasis::sqr.
        auto pow5 = [](const auto& x_m) -> Accumulator {
            const Accumulator x(x_m);
            const Accumulator sq(x_m.sqr());
            return sq.sqr() * x;
        };
 
        // S-boxes for the four rounds.
        auto u_0 = pow5(w_l + q_l);
        auto u_1 = pow5(w_r + q_r);
        auto u_2 = pow5(w_o + q_o);
        auto u_3 = pow5(w_4 + q_4);
 
        // Closed-form output rows, with shifted successor-row terms folded into the wire part.
        const auto& C = QuadParams::tables.closed_form;
        auto wp_0 = w_r * C[0][0] + w_o * C[0][1] + w_4 * C[0][2] - w_l_shift;
        auto wp_1 = w_r * C[1][0] + w_o * C[1][1] + w_4 * C[1][2] - w_r_shift;
        auto wp_2 = w_r * C[2][0] + w_o * C[2][1] + w_4 * C[2][2] - w_o_shift;
        auto wp_3 = w_r * C[3][0] + w_o * C[3][1] + w_4 * C[3][2] - w_4_shift;
 
        const auto q_by_scaling_m = q_sel * scaling_factor;
        const auto q_by_scaling = Accumulator(q_by_scaling_m);
 
        // Subrelation bodies: out_k - w_*_shift = 0.
        auto a0_body = u_0 * C[0][3] + u_1 * C[0][4] + u_2 * C[0][5] + u_3 * C[0][6] + Accumulator(wp_0);
        auto a1_body = u_0 * C[1][3] + u_1 * C[1][4] + u_2 * C[1][5] + u_3 + Accumulator(wp_1);
        auto a2_body = u_0 * C[2][3] + u_1 * C[2][4] + u_2 * C[2][5] + u_3 + Accumulator(wp_2);
        auto a3_body = u_0 * C[3][3] + u_1 * C[3][4] + u_2 * C[3][5] + u_3 + Accumulator(wp_3);
 
        std::get<0>(evals) += q_by_scaling * a0_body;
        std::get<1>(evals) += q_by_scaling * a1_body;
        std::get<2>(evals) += q_by_scaling * a2_body;
        std::get<3>(evals) += q_by_scaling * a3_body;
    }
};
 
template <typename FF>
using Poseidon2QuadInternalTerminalRelation = Relation<Poseidon2QuadInternalTerminalRelationImpl<FF>>;
 
} // namespace bb