sap.tcc

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/** @file
*****************************************************************************
 
Implementation of interfaces for a SAP ("Square Arithmetic Program").
 
See sap.hpp .
 
*****************************************************************************
* @author     This file is part of libsnark, developed by SCIPR Lab
*             and contributors (see AUTHORS).
* @copyright  MIT license (see LICENSE file)
*****************************************************************************/
 
#ifndef SAP_TCC_
#define SAP_TCC_
 
#include <libff/algebra/scalar_multiplication/multiexp.hpp>
#include <libff/common/profiling.hpp>
#include <libff/common/utils.hpp>
#include <libfqfft/evaluation_domain/evaluation_domain.hpp>
 
namespace libsnark
{
 
template<typename FieldT>
sap_instance<FieldT>::sap_instance(
    const std::shared_ptr<libfqfft::evaluation_domain<FieldT>> &domain,
    const size_t num_variables,
    const size_t degree,
    const size_t num_inputs,
    const std::vector<std::map<size_t, FieldT>> &A_in_Lagrange_basis,
    const std::vector<std::map<size_t, FieldT>> &C_in_Lagrange_basis)
    : num_variables_(num_variables)
    , degree_(degree)
    , num_inputs_(num_inputs)
    , domain(domain)
    , A_in_Lagrange_basis(A_in_Lagrange_basis)
    , C_in_Lagrange_basis(C_in_Lagrange_basis)
{
}
 
template<typename FieldT>
sap_instance<FieldT>::sap_instance(
    const std::shared_ptr<libfqfft::evaluation_domain<FieldT>> &domain,
    const size_t num_variables,
    const size_t degree,
    const size_t num_inputs,
    std::vector<std::map<size_t, FieldT>> &&A_in_Lagrange_basis,
    std::vector<std::map<size_t, FieldT>> &&C_in_Lagrange_basis)
    : num_variables_(num_variables)
    , degree_(degree)
    , num_inputs_(num_inputs)
    , domain(domain)
    , A_in_Lagrange_basis(std::move(A_in_Lagrange_basis))
    , C_in_Lagrange_basis(std::move(C_in_Lagrange_basis))
{
}
 
template<typename FieldT> size_t sap_instance<FieldT>::num_variables() const
{
    return num_variables_;
}
 
template<typename FieldT> size_t sap_instance<FieldT>::degree() const
{
    return degree_;
}
 
template<typename FieldT> size_t sap_instance<FieldT>::num_inputs() const
{
    return num_inputs_;
}
 
template<typename FieldT>
bool sap_instance<FieldT>::is_satisfied(
    const sap_witness<FieldT> &witness) const
{
    const FieldT t = FieldT::random_element();
 
    std::vector<FieldT> At(this->num_variables() + 1, FieldT::zero());
    std::vector<FieldT> Ct(this->num_variables() + 1, FieldT::zero());
    std::vector<FieldT> Ht(this->degree() + 1);
 
    const FieldT Zt = this->domain->compute_vanishing_polynomial(t);
 
    const std::vector<FieldT> u =
        this->domain->evaluate_all_lagrange_polynomials(t);
 
    for (size_t i = 0; i < this->num_variables() + 1; ++i) {
        for (auto &el : A_in_Lagrange_basis[i]) {
            At[i] += u[el.first] * el.second;
        }
 
        for (auto &el : C_in_Lagrange_basis[i]) {
            Ct[i] += u[el.first] * el.second;
        }
    }
 
    FieldT ti = FieldT::one();
    for (size_t i = 0; i < this->degree() + 1; ++i) {
        Ht[i] = ti;
        ti *= t;
    }
 
    const sap_instance_evaluation<FieldT> eval_sap_inst(
        this->domain,
        this->num_variables(),
        this->degree(),
        this->num_inputs(),
        t,
        std::move(At),
        std::move(Ct),
        std::move(Ht),
        Zt);
    return eval_sap_inst.is_satisfied(witness);
}
 
template<typename FieldT>
sap_instance_evaluation<FieldT>::sap_instance_evaluation(
    const std::shared_ptr<libfqfft::evaluation_domain<FieldT>> &domain,
    const size_t num_variables,
    const size_t degree,
    const size_t num_inputs,
    const FieldT &t,
    const std::vector<FieldT> &At,
    const std::vector<FieldT> &Ct,
    const std::vector<FieldT> &Ht,
    const FieldT &Zt)
    : num_variables_(num_variables)
    , degree_(degree)
    , num_inputs_(num_inputs)
    , domain(domain)
    , t(t)
    , At(At)
    , Ct(Ct)
    , Ht(Ht)
    , Zt(Zt)
{
}
 
template<typename FieldT>
sap_instance_evaluation<FieldT>::sap_instance_evaluation(
    const std::shared_ptr<libfqfft::evaluation_domain<FieldT>> &domain,
    const size_t num_variables,
    const size_t degree,
    const size_t num_inputs,
    const FieldT &t,
    std::vector<FieldT> &&At,
    std::vector<FieldT> &&Ct,
    std::vector<FieldT> &&Ht,
    const FieldT &Zt)
    : num_variables_(num_variables)
    , degree_(degree)
    , num_inputs_(num_inputs)
    , domain(domain)
    , t(t)
    , At(std::move(At))
    , Ct(std::move(Ct))
    , Ht(std::move(Ht))
    , Zt(Zt)
{
}
 
template<typename FieldT>
size_t sap_instance_evaluation<FieldT>::num_variables() const
{
    return num_variables_;
}
 
template<typename FieldT> size_t sap_instance_evaluation<FieldT>::degree() const
{
    return degree_;
}
 
template<typename FieldT>
size_t sap_instance_evaluation<FieldT>::num_inputs() const
{
    return num_inputs_;
}
 
template<typename FieldT>
bool sap_instance_evaluation<FieldT>::is_satisfied(
    const sap_witness<FieldT> &witness) const
{
    if (this->num_variables() != witness.num_variables()) {
        return false;
    }
 
    if (this->degree() != witness.degree()) {
        return false;
    }
 
    if (this->num_inputs() != witness.num_inputs()) {
        return false;
    }
 
    if (this->num_variables() != witness.coefficients_for_ACs.size()) {
        return false;
    }
 
    if (this->degree() + 1 != witness.coefficients_for_H.size()) {
        return false;
    }
 
    if (this->At.size() != this->num_variables() + 1 ||
        this->Ct.size() != this->num_variables() + 1) {
        return false;
    }
 
    if (this->Ht.size() != this->degree() + 1) {
        return false;
    }
 
    if (this->Zt != this->domain->compute_vanishing_polynomial(this->t)) {
        return false;
    }
 
    FieldT ans_A = this->At[0] + witness.d1 * this->Zt;
    FieldT ans_C = this->Ct[0] + witness.d2 * this->Zt;
    FieldT ans_H = FieldT::zero();
 
    ans_A = ans_A +
            libff::inner_product<FieldT>(
                this->At.begin() + 1,
                this->At.begin() + 1 + this->num_variables(),
                witness.coefficients_for_ACs.begin(),
                witness.coefficients_for_ACs.begin() + this->num_variables());
    ans_C = ans_C +
            libff::inner_product<FieldT>(
                this->Ct.begin() + 1,
                this->Ct.begin() + 1 + this->num_variables(),
                witness.coefficients_for_ACs.begin(),
                witness.coefficients_for_ACs.begin() + this->num_variables());
    ans_H =
        ans_H + libff::inner_product<FieldT>(
                    this->Ht.begin(),
                    this->Ht.begin() + this->degree() + 1,
                    witness.coefficients_for_H.begin(),
                    witness.coefficients_for_H.begin() + this->degree() + 1);
 
    if (ans_A * ans_A - ans_C != ans_H * this->Zt) {
        return false;
    }
 
    return true;
}
 
template<typename FieldT>
sap_witness<FieldT>::sap_witness(
    const size_t num_variables,
    const size_t degree,
    const size_t num_inputs,
    const FieldT &d1,
    const FieldT &d2,
    const std::vector<FieldT> &coefficients_for_ACs,
    const std::vector<FieldT> &coefficients_for_H)
    : num_variables_(num_variables)
    , degree_(degree)
    , num_inputs_(num_inputs)
    , d1(d1)
    , d2(d2)
    , coefficients_for_ACs(coefficients_for_ACs)
    , coefficients_for_H(coefficients_for_H)
{
}
 
template<typename FieldT>
sap_witness<FieldT>::sap_witness(
    const size_t num_variables,
    const size_t degree,
    const size_t num_inputs,
    const FieldT &d1,
    const FieldT &d2,
    const std::vector<FieldT> &coefficients_for_ACs,
    std::vector<FieldT> &&coefficients_for_H)
    : num_variables_(num_variables)
    , degree_(degree)
    , num_inputs_(num_inputs)
    , d1(d1)
    , d2(d2)
    , coefficients_for_ACs(coefficients_for_ACs)
    , coefficients_for_H(std::move(coefficients_for_H))
{
}
 
template<typename FieldT> size_t sap_witness<FieldT>::num_variables() const
{
    return num_variables_;
}
 
template<typename FieldT> size_t sap_witness<FieldT>::degree() const
{
    return degree_;
}
 
template<typename FieldT> size_t sap_witness<FieldT>::num_inputs() const
{
    return num_inputs_;
}
 
} // namespace libsnark
 
#endif // SAP_TCC_