uscs.tcc

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/** @file
 *****************************************************************************
 
 Implementation of interfaces for:
 - a USCS constraint,
 - a USCS variable assignment, and
 - a USCS constraint system.
 
 See uscs.hpp .
 
 *****************************************************************************
 * @author     This file is part of libsnark, developed by SCIPR Lab
 *             and contributors (see AUTHORS).
 * @copyright  MIT license (see LICENSE file)
 *****************************************************************************/
 
#ifndef USCS_TCC_
#define USCS_TCC_
 
#include <algorithm>
#include <cassert>
#include <libff/algebra/fields/bigint.hpp>
#include <libff/common/profiling.hpp>
#include <libff/common/utils.hpp>
#include <set>
 
namespace libsnark
{
 
template<typename FieldT>
size_t uscs_constraint_system<FieldT>::num_inputs() const
{
    return primary_input_size;
}
 
template<typename FieldT>
size_t uscs_constraint_system<FieldT>::num_variables() const
{
    return primary_input_size + auxiliary_input_size;
}
 
template<typename FieldT>
size_t uscs_constraint_system<FieldT>::num_constraints() const
{
    return constraints.size();
}
 
template<typename FieldT> bool uscs_constraint_system<FieldT>::is_valid() const
{
    if (this->num_inputs() > this->num_variables())
        return false;
 
    for (size_t c = 0; c < constraints.size(); ++c) {
        if (!valid_vector(constraints[c], this->num_variables())) {
            return false;
        }
    }
 
    return true;
}
 
template<typename FieldT>
void dump_uscs_constraint(
    const uscs_constraint<FieldT> &constraint,
    const uscs_variable_assignment<FieldT> &full_variable_assignment,
    const std::map<size_t, std::string> &variable_annotations)
{
    printf("terms:\n");
    constraint.print_with_assignment(
        full_variable_assignment, variable_annotations);
}
 
template<typename FieldT>
bool uscs_constraint_system<FieldT>::is_satisfied(
    const uscs_primary_input<FieldT> &primary_input,
    const uscs_auxiliary_input<FieldT> &auxiliary_input) const
{
    assert(primary_input.size() == num_inputs());
    assert(primary_input.size() + auxiliary_input.size() == num_variables());
 
    uscs_variable_assignment<FieldT> full_variable_assignment = primary_input;
    full_variable_assignment.insert(
        full_variable_assignment.end(),
        auxiliary_input.begin(),
        auxiliary_input.end());
 
    for (size_t c = 0; c < constraints.size(); ++c) {
        FieldT res = constraints[c].evaluate(full_variable_assignment);
        if (!(res.squared() == FieldT::one())) {
#ifdef DEBUG
            auto it = constraint_annotations.find(c);
            printf(
                "constraint %zu (%s) unsatisfied\n",
                c,
                (it == constraint_annotations.end() ? "no annotation"
                                                    : it->second.c_str()));
            printf("<a,(1,x)> = ");
            res.print();
            printf("constraint was:\n");
            dump_uscs_constraint(
                constraints[c], full_variable_assignment, variable_annotations);
#endif // DEBUG
            return false;
        }
    }
 
    return true;
}
 
template<typename FieldT>
void uscs_constraint_system<FieldT>::add_constraint(
    const uscs_constraint<FieldT> &c)
{
    constraints.emplace_back(c);
}
 
template<typename FieldT>
void uscs_constraint_system<FieldT>::add_constraint(
    const uscs_constraint<FieldT> &c, const std::string &annotation)
{
#ifdef DEBUG
    constraint_annotations[constraints.size()] = annotation;
#else
    libff::UNUSED(annotation);
#endif
    constraints.emplace_back(c);
}
 
template<typename FieldT>
bool uscs_constraint_system<FieldT>::operator==(
    const uscs_constraint_system<FieldT> &other) const
{
    return (
        this->constraints == other.constraints &&
        this->primary_input_size == other.primary_input_size &&
        this->auxiliary_input_size == other.auxiliary_input_size);
}
 
template<typename FieldT>
std::ostream &operator<<(
    std::ostream &out, const uscs_constraint_system<FieldT> &cs)
{
    out << cs.primary_input_size << "\n";
    out << cs.auxiliary_input_size << "\n";
 
    out << cs.num_constraints() << "\n";
    for (const uscs_constraint<FieldT> &c : cs.constraints) {
        out << c;
    }
 
    return out;
}
 
template<typename FieldT>
std::istream &operator>>(std::istream &in, uscs_constraint_system<FieldT> &cs)
{
    in >> cs.primary_input_size;
    in >> cs.auxiliary_input_size;
 
    cs.constraints.clear();
 
    size_t s;
    in >> s;
 
    char b;
    in.read(&b, 1);
 
    cs.constraints.reserve(s);
 
    for (size_t i = 0; i < s; ++i) {
        uscs_constraint<FieldT> c;
        in >> c;
        cs.constraints.emplace_back(c);
    }
 
    return in;
}
 
template<typename FieldT>
void uscs_constraint_system<FieldT>::report_linear_constraint_statistics() const
{
#ifdef DEBUG
    for (size_t i = 0; i < constraints.size(); ++i) {
        auto &constr = constraints[i];
        bool a_is_const = true;
        for (auto &t : constr.terms) {
            a_is_const = a_is_const && (t.index == 0);
        }
 
        if (a_is_const) {
            auto it = constraint_annotations.find(i);
            printf(
                "%s\n",
                (it == constraint_annotations.end()
                     ? FMT("", "constraint_%zu", i)
                     : it->second)
                    .c_str());
        }
    }
#endif
}
 
} // namespace libsnark
 
#endif // USCS_TCC_