mock_circuits.hpp

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// === AUDIT STATUS ===
// internal:    { status: not started, auditors: [], date: YYYY-MM-DD }
// external_1:  { status: not started, auditors: [], date: YYYY-MM-DD }
// external_2:  { status: not started, auditors: [], date: YYYY-MM-DD }
// =====================
 
#pragma once
#include "barretenberg/common/assert.hpp"
#include "barretenberg/stdlib_circuit_builders/mega_circuit_builder.hpp"
 
namespace bb {
 
namespace {
auto& engine = numeric::get_debug_randomness();
}
class MockCircuits {
  public:
    using Curve = curve::BN254;
    using FF = Curve::ScalarField;
    using Point = Curve::AffineElement;
 
    template <typename Builder>
    static void add_arithmetic_gates_with_public_inputs(Builder& builder, const size_t num_gates = 4)
    {
        // For good measure, include a gate with some public inputs
        for (size_t i = 0; i < num_gates; ++i) {
            FF a = FF::random_element(&engine);
            FF b = FF::random_element(&engine);
            FF c = FF::random_element(&engine);
            FF d = a + b + c;
            uint32_t a_idx = builder.add_public_variable(a);
            uint32_t b_idx = builder.add_variable(b);
            uint32_t c_idx = builder.add_variable(c);
            uint32_t d_idx = builder.add_variable(d);
 
            builder.create_big_add_gate({ a_idx, b_idx, c_idx, d_idx, FF(1), FF(1), FF(1), FF(-1), FF(0) });
        }
    }
 
    template <typename Builder> static void add_arithmetic_gates(Builder& builder, const size_t num_gates = 4)
    {
        for (size_t i = 0; i < num_gates; ++i) {
            FF a = FF::random_element(&engine);
            FF b = FF::random_element(&engine);
            FF c = FF::random_element(&engine);
            FF d = a + b + c;
            uint32_t a_idx = builder.add_variable(a);
            uint32_t b_idx = builder.add_variable(b);
            uint32_t c_idx = builder.add_variable(c);
            uint32_t d_idx = builder.add_variable(d);
 
            builder.create_big_add_gate({ a_idx, b_idx, c_idx, d_idx, FF(1), FF(1), FF(1), FF(-1), FF(0) });
        }
    }
 
    template <typename Builder> static void add_lookup_gates(Builder& builder, size_t num_iterations = 1)
    {
        auto UINT32_XOR = plookup::MultiTableId::UINT32_XOR;
 
        // Each iteration adds 6 lookup gates (due to six 6-bit limbs); the first adds a table of size 4096
        for (size_t i = 0; i < num_iterations; ++i) {
            // define some arbitrary inputs to uint32 XOR
            uint32_t left_value = engine.get_random_uint32();
            uint32_t right_value = engine.get_random_uint32();
 
            fr left = fr{ left_value, 0, 0, 0 }.to_montgomery_form();
            fr right = fr{ right_value, 0, 0, 0 }.to_montgomery_form();
 
            auto left_idx = builder.add_variable(left);
            auto right_idx = builder.add_variable(right);
 
            // perform lookups from the uint32 XOR table
            auto accumulators = plookup::get_lookup_accumulators(UINT32_XOR, left, right, /*is_2_to_1_lookup*/ true);
            builder.create_gates_from_plookup_accumulators(UINT32_XOR, accumulators, left_idx, right_idx);
        }
    }
 
    template <typename Builder> static void add_RAM_gates(Builder& builder)
    {
        std::array<uint32_t, 3> ram_values{ builder.add_variable(5),
                                            builder.add_variable(10),
                                            builder.add_variable(20) };
 
        size_t ram_id = builder.create_RAM_array(3);
 
        for (size_t i = 0; i < 3; ++i) {
            builder.init_RAM_element(ram_id, i, ram_values[i]);
        }
 
        auto val_idx_1 = builder.read_RAM_array(ram_id, builder.add_variable(1));
        auto val_idx_2 = builder.read_RAM_array(ram_id, builder.add_variable(2));
        auto val_idx_3 = builder.read_RAM_array(ram_id, builder.add_variable(0));
 
        builder.create_big_add_gate({
            val_idx_1,
            val_idx_2,
            val_idx_3,
            builder.zero_idx,
            1,
            1,
            1,
            0,
            -35,
        });
    }
 
    template <typename Builder>
    static void construct_arithmetic_circuit(Builder& builder,
                                             const size_t target_log2_dyadic_size = 4,
                                             bool include_public_inputs = true)
    {
        const size_t target_dyadic_size = 1 << target_log2_dyadic_size;
        const size_t num_preamble_gates = builder.num_gates;
        BB_ASSERT_GTE(target_dyadic_size, num_preamble_gates);
 
        // For good measure, include a gate with some public inputs
        if (include_public_inputs && target_dyadic_size > num_preamble_gates) {
            add_arithmetic_gates_with_public_inputs(builder, 1);
        }
 
        // A proper treatment of this would dynamically calculate how many gates to add given static information about
        // Builder, but a major overhaul of the execution trace is underway, so we just elect to use a hack. Namely, for
        // all of builders for which we instantiate this template and for all circuit sizes we care about, to achieve a
        // desired dyadic circuit size after boilerplate gates, it is sufficient to fill up to OFFSET_HACK-many gates
        // short of the desired dyadic circuit size.
        // TODO(https://github.com/AztecProtocol/barretenberg/issues/902)
        static constexpr size_t OFFSET_HACK = 10;
 
        // to prevent underflow of the loop upper limit; target size >= 16 should suffice
        BB_ASSERT_GT(target_dyadic_size, OFFSET_HACK + num_preamble_gates);
        size_t num_gates_to_add = target_dyadic_size - OFFSET_HACK - 1 - num_preamble_gates;
 
        // Add arbitrary arithmetic gates to obtain a total of num_gates-many gates
        add_arithmetic_gates(builder, num_gates_to_add);
    }
 
    static void construct_goblin_ecc_op_circuit(MegaCircuitBuilder& builder)
    {
        // Add a mul accum op, an add accum op and an equality op
        builder.queue_ecc_add_accum(Point::one() * FF::random_element(&engine));
        builder.queue_ecc_mul_accum(Point::one() * FF::random_element(&engine), FF::random_element(&engine));
        builder.queue_ecc_eq();
    }
};
} // namespace bb