simple_example.cpp

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#include <libsnark/gadgetlib2/adapters.hpp>
#include <libsnark/gadgetlib2/examples/simple_example.hpp>
#include <libsnark/gadgetlib2/gadget.hpp>
#include <libsnark/gadgetlib2/integration.hpp>
 
namespace libsnark
{
 
/* NOTE: all examples here actually generate one constraint less to account for
 * soundness constraint in QAP */
r1cs_example<libff::Fr<libff::default_ec_pp>>
gen_r1cs_example_from_gadgetlib2_protoboard(const size_t size)
{
    typedef libff::Fr<libff::default_ec_pp> FieldT;
 
    gadgetlib2::initPublicParamsFromDefaultPp();
    // necessary in case a protoboard was built before,  libsnark assumes
    // variable indices always begin with 0 so we must reset the index before
    // creating constraints which will be used by libsnark
    gadgetlib2::GadgetLibAdapter::resetVariableIndex();
 
    // create a gadgetlib2 gadget. This part is done by both generator and
    // prover.
    auto pb = gadgetlib2::Protoboard::create(gadgetlib2::R1P);
    gadgetlib2::VariableArray A(size, "A");
    gadgetlib2::VariableArray B(size, "B");
    gadgetlib2::Variable result("result");
    auto g = gadgetlib2::InnerProduct_Gadget::create(pb, A, B, result);
    // create constraints. This part is done by generator.
    g->generateConstraints();
    // create assignment (witness). This part is done by prover.
    for (size_t k = 0; k < size; ++k) {
        pb->val(A[k]) = std::rand() % 2;
        pb->val(B[k]) = std::rand() % 2;
    }
    g->generateWitness();
    // translate constraint system to libsnark format.
    r1cs_constraint_system<FieldT> cs =
        get_constraint_system_from_gadgetlib2(*pb);
    // translate full variable assignment to libsnark format
    const r1cs_variable_assignment<FieldT> full_assignment =
        get_variable_assignment_from_gadgetlib2(*pb);
    // extract primary and auxiliary input
    const r1cs_primary_input<FieldT> primary_input(
        full_assignment.begin(), full_assignment.begin() + cs.num_inputs());
    const r1cs_auxiliary_input<FieldT> auxiliary_input(
        full_assignment.begin() + cs.num_inputs(), full_assignment.end());
 
    assert(cs.is_valid());
    assert(cs.is_satisfied(primary_input, auxiliary_input));
 
    return r1cs_example<FieldT>(cs, primary_input, auxiliary_input);
}
 
} // namespace libsnark