poseidon2_internal_relation.hpp

#pragma once
#include "barretenberg/crypto/poseidon2/poseidon2_params.hpp"
#include "relation_types.hpp"
 
namespace proof_system {
 
template <typename FF_> class Poseidon2InternalRelationImpl {
  public:
    using FF = FF_;
 
    static constexpr std::array<size_t, 4> SUBRELATION_PARTIAL_LENGTHS{
        7, // internal poseidon2 round sub-relation for first value
        7, // internal poseidon2 round sub-relation for second value
        7, // internal poseidon2 round sub-relation for third value
        7, // internal poseidon2 round sub-relation for fourth value
    };
 
    template <typename ContainerOverSubrelations, typename AllEntities, typename Parameters>
    void static accumulate(ContainerOverSubrelations& evals,
                           const AllEntities& in,
                           const Parameters&,
                           const FF& scaling_factor)
    {
        using Accumulator = std::tuple_element_t<0, ContainerOverSubrelations>;
        using View = typename Accumulator::View;
        auto w_l = View(in.w_l);
        auto w_r = View(in.w_r);
        auto w_o = View(in.w_o);
        auto w_4 = View(in.w_4);
        auto w_l_shift = View(in.w_l_shift);
        auto w_r_shift = View(in.w_r_shift);
        auto w_o_shift = View(in.w_o_shift);
        auto w_4_shift = View(in.w_4_shift);
        auto q_l = View(in.q_l);
        auto q_poseidon2_internal = View(in.q_poseidon2_internal);
 
        // add round constants
        auto s1 = w_l + q_l;
 
        // apply s-box round
        auto u1 = s1 * s1;
        u1 *= u1;
        u1 *= s1;
        auto u2 = w_r;
        auto u3 = w_o;
        auto u4 = w_4;
 
        // matrix mul with v = M_I * u 4 muls and 7 additions
        auto sum = u1 + u2 + u3 + u4;
 
        auto v1 = u1 * crypto::Poseidon2Bn254ScalarFieldParams::internal_matrix_diagonal[0];
        v1 += sum;
        auto tmp = q_poseidon2_internal * (v1 - w_l_shift);
        tmp *= scaling_factor;
        std::get<0>(evals) += tmp;
 
        auto v2 = u2 * crypto::Poseidon2Bn254ScalarFieldParams::internal_matrix_diagonal[1];
        v2 += sum;
        tmp = q_poseidon2_internal * (v2 - w_r_shift);
        tmp *= scaling_factor;
        std::get<1>(evals) += tmp;
 
        auto v3 = u3 * crypto::Poseidon2Bn254ScalarFieldParams::internal_matrix_diagonal[2];
        v3 += sum;
        tmp = q_poseidon2_internal * (v3 - w_o_shift);
        tmp *= scaling_factor;
        std::get<2>(evals) += tmp;
 
        auto v4 = u4 * crypto::Poseidon2Bn254ScalarFieldParams::internal_matrix_diagonal[3];
        v4 += sum;
        tmp = q_poseidon2_internal * (v4 - w_4_shift);
        tmp *= scaling_factor;
        std::get<3>(evals) += tmp;
    };
}; // namespace proof_system
 
template <typename FF> using Poseidon2InternalRelation = Relation<Poseidon2InternalRelationImpl<FF>>;
} // namespace proof_system