chore: remove circuit simulator (#13689)

Remove all code related to the `CircuitSimulator`.

The idea of the `CircuitSimulator` was to allow us to write our
verification algorithms once and for all in "circuit" format then
achieve recursive verification through supplying a real builder (e.g.
Ultra/Mega) and native verification through supplying the
`CircuitSimulator`. The motivation was that the recursive circuits
should be the first class objects, rather than their native
counterparts. In practice this proved to be too complicated and was
never used. We don't have time to flesh it out at this point and it adds
a very high degree of complexity and clutter to some of our most complex
code.

Author: ledwards2225

barretenberg/cpp/src/barretenberg/benchmark/CMakeLists.txt

@@ -6,7 +6,6 @@ add_subdirectory(bb_cli_bench)
 add_subdirectory(client_ivc_bench)
 add_subdirectory(pippenger_bench)
 add_subdirectory(plonk_bench)
-add_subdirectory(simulator_bench)
 add_subdirectory(protogalaxy_bench)
 add_subdirectory(protogalaxy_rounds_bench)
 add_subdirectory(relations_bench)

barretenberg/cpp/src/barretenberg/benchmark/simulator_bench/CMakeLists.txt

@@ -12,8 +12,7 @@ concept IsCheckable = bb::IsAnyOf<T,
                                   StandardCircuitBuilder_<bb::fr>,
                                   StandardCircuitBuilder_<bb::fq>,
                                   UltraCircuitBuilder,
-                                  MegaCircuitBuilder,
-                                  CircuitSimulatorBN254>;
+                                  MegaCircuitBuilder>;
 
 /**
  * @brief The unified interface for check circuit functionality implemented in the specialized CircuitChecker classes
@@ -28,8 +27,6 @@ class CircuitChecker {
             return UltraCircuitChecker::check(builder);
         } else if constexpr (IsStandardBuilder<Builder>) {
             return StandardCircuitChecker::check(builder);
-        } else if constexpr (IsSimulator<Builder>) {
-            return SimulatorCircuitChecker::check(builder);
         } else {
             return false;
         }

barretenberg/cpp/src/barretenberg/benchmark/simulator_bench/simulator.bench.cpp

@@ -400,7 +400,6 @@ template <typename T>
 concept IsMegaFlavor = IsAnyOf<T, MegaFlavor, MegaZKFlavor,
                                     MegaRecursiveFlavor_<UltraCircuitBuilder>,
                                     MegaRecursiveFlavor_<MegaCircuitBuilder>,
-                                    MegaRecursiveFlavor_<CircuitSimulatorBN254>,
                                     MegaZKRecursiveFlavor_<MegaCircuitBuilder>,
                                     MegaZKRecursiveFlavor_<UltraCircuitBuilder>>;
 
@@ -413,16 +412,13 @@ concept HasIPAAccumulator = IsAnyOf<T, UltraRollupFlavor, UltraRollupRecursiveFl
 template <typename T>
 concept IsRecursiveFlavor = IsAnyOf<T, UltraRecursiveFlavor_<UltraCircuitBuilder>,
                                        UltraRecursiveFlavor_<MegaCircuitBuilder>,
-                                       UltraRecursiveFlavor_<CircuitSimulatorBN254>,
                                        UltraRollupRecursiveFlavor_<UltraCircuitBuilder>,
                                        MegaRecursiveFlavor_<UltraCircuitBuilder>,
                                        MegaRecursiveFlavor_<MegaCircuitBuilder>,
-                                        MegaRecursiveFlavor_<CircuitSimulatorBN254>,
                                         MegaZKRecursiveFlavor_<MegaCircuitBuilder>,
                                         MegaZKRecursiveFlavor_<UltraCircuitBuilder>,
                                         TranslatorRecursiveFlavor_<UltraCircuitBuilder>,
                                         TranslatorRecursiveFlavor_<MegaCircuitBuilder>,
-                                        TranslatorRecursiveFlavor_<CircuitSimulatorBN254>,
                                         ECCVMRecursiveFlavor_<UltraCircuitBuilder>,
                                         AvmRecursiveFlavor_<UltraCircuitBuilder>,
                                         AvmRecursiveFlavor_<MegaCircuitBuilder>,
@@ -446,11 +442,9 @@ template <typename T> concept IsFoldingFlavor = IsAnyOf<T, UltraFlavor,
                                                            MegaZKFlavor,
                                                            UltraRecursiveFlavor_<UltraCircuitBuilder>,
                                                            UltraRecursiveFlavor_<MegaCircuitBuilder>,
-                                                           UltraRecursiveFlavor_<CircuitSimulatorBN254>,
                                                            UltraRollupRecursiveFlavor_<UltraCircuitBuilder>,
                                                            MegaRecursiveFlavor_<UltraCircuitBuilder>,
                                                            MegaRecursiveFlavor_<MegaCircuitBuilder>,
-                                                            MegaRecursiveFlavor_<CircuitSimulatorBN254>,
                                                             MegaZKRecursiveFlavor_<MegaCircuitBuilder>,
                                                             MegaZKRecursiveFlavor_<UltraCircuitBuilder>>;
 #else
@@ -464,11 +458,9 @@ template <typename T> concept IsFoldingFlavor = IsAnyOf<T, UltraFlavor,
                                                            MegaZKFlavor,
                                                            UltraRecursiveFlavor_<UltraCircuitBuilder>,
                                                            UltraRecursiveFlavor_<MegaCircuitBuilder>,
-                                                           UltraRecursiveFlavor_<CircuitSimulatorBN254>,
                                                            UltraRollupRecursiveFlavor_<UltraCircuitBuilder>,
                                                            MegaRecursiveFlavor_<UltraCircuitBuilder>,
                                                            MegaRecursiveFlavor_<MegaCircuitBuilder>,
-                                                            MegaRecursiveFlavor_<CircuitSimulatorBN254>,
                                                             MegaZKRecursiveFlavor_<MegaCircuitBuilder>,
                                                             MegaZKRecursiveFlavor_<UltraCircuitBuilder>>;
 #endif

barretenberg/cpp/src/barretenberg/circuit_checker/circuit_checker.hpp

@@ -831,10 +831,6 @@ stdlib::byte_array<Builder> keccak<Builder>::hash(byte_array_ct& input, const ui
         return output;
     };
 
-    if constexpr (IsSimulator<Builder>) {
-        return constant_case();
-    }
-
     if (ctx == nullptr) {
         return constant_case();
     }
@@ -921,7 +917,6 @@ template <typename Builder> void generate_keccak_test_circuit(Builder& builder,
     }
 }
 
-template class keccak<bb::CircuitSimulatorBN254>;
 template class keccak<bb::UltraCircuitBuilder>;
 template class keccak<bb::MegaCircuitBuilder>;
 template void generate_keccak_test_circuit(bb::UltraCircuitBuilder&, size_t);

barretenberg/cpp/src/barretenberg/flavor/flavor.hpp

@@ -47,6 +47,5 @@ template <typename C> field_t<C> poseidon2<C>::hash_buffer(C& builder, const std
 }
 template class poseidon2<bb::MegaCircuitBuilder>;
 template class poseidon2<bb::UltraCircuitBuilder>;
-template class poseidon2<bb::CircuitSimulatorBN254>;
 
 } // namespace bb::stdlib

barretenberg/cpp/src/barretenberg/stdlib/hash/keccak/keccak.cpp

@@ -147,7 +147,7 @@ template <typename Builder> class StdlibPoseidon2 : public testing::Test {
     }
 };
 
-using CircuitTypes = testing::Types<bb::MegaCircuitBuilder, bb::UltraCircuitBuilder, bb::CircuitSimulatorBN254>;
+using CircuitTypes = testing::Types<bb::MegaCircuitBuilder, bb::UltraCircuitBuilder>;
 
 TYPED_TEST_SUITE(StdlibPoseidon2, CircuitTypes);
 

barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.cpp

@@ -23,7 +23,6 @@ namespace bb::stdlib {
 template <typename Params, typename Builder>
 typename Poseidon2Permutation<Params, Builder>::State Poseidon2Permutation<Params, Builder>::permutation(
     Builder* builder, const typename Poseidon2Permutation<Params, Builder>::State& input)
-    requires(!IsSimulator<Builder>)
 {
     // deep copy
     State current_state(input);
@@ -115,95 +114,6 @@ typename Poseidon2Permutation<Params, Builder>::State Poseidon2Permutation<Param
     return current_state;
 }
 
-/**
- * @brief Circuit form of Poseidon2 permutation from https://eprint.iacr.org/2023/323 for UltraCircuitBuilder.
- * @details The permutation consists of one initial linear layer, then a set of external rounds, a set of internal
- * rounds, and a set of external rounds.
- * @param builder
- * @param input
- * @return State
- */
-template <typename Params, typename Builder>
-typename Poseidon2Permutation<Params, Builder>::State Poseidon2Permutation<Params, Builder>::permutation(
-    Builder* builder, const typename Poseidon2Permutation<Params, Builder>::State& input)
-    requires IsSimulator<Builder>
-{
-    // deep copy
-    State current_state(input);
-
-    // Apply 1st linear layer
-    matrix_multiplication_external(builder, current_state);
-
-    // First set of external rounds
-    constexpr size_t rounds_f_beginning = rounds_f / 2;
-    for (size_t i = 0; i < rounds_f_beginning; ++i) {
-        add_round_constants(current_state, round_constants[i]);
-        apply_sbox(current_state);
-        matrix_multiplication_external(builder, current_state);
-    }
-
-    // Internal rounds
-    const size_t p_end = rounds_f_beginning + rounds_p;
-    for (size_t i = rounds_f_beginning; i < p_end; ++i) {
-        current_state[0] += round_constants[i][0];
-        apply_single_sbox(current_state[0]);
-        matrix_multiplication_internal(current_state);
-    }
-
-    // Remaining external rounds
-    for (size_t i = p_end; i < NUM_ROUNDS; ++i) {
-        add_round_constants(current_state, round_constants[i]);
-        apply_sbox(current_state);
-        matrix_multiplication_external(builder, current_state);
-    }
-    return current_state;
-}
-
-template <typename Params, typename Builder>
-void Poseidon2Permutation<Params, Builder>::add_round_constants(
-    State& input, const typename Poseidon2Permutation<Params, Builder>::RoundConstants& rc)
-    requires IsSimulator<Builder>
-
-{
-    for (size_t i = 0; i < t; ++i) {
-        input[i] += rc[i];
-    }
-}
-
-template <typename Params, typename Builder>
-void Poseidon2Permutation<Params, Builder>::apply_sbox(State& input)
-    requires IsSimulator<Builder>
-{
-    for (auto& in : input) {
-        apply_single_sbox(in);
-    }
-}
-
-template <typename Params, typename Builder>
-void Poseidon2Permutation<Params, Builder>::apply_single_sbox(field_t<Builder>& input)
-    requires IsSimulator<Builder>
-{
-    // hardcoded assumption that d = 5. should fix this or not make d configurable
-    auto xx = input.sqr();
-    auto xxxx = xx.sqr();
-    input *= xxxx;
-}
-
-template <typename Params, typename Builder>
-void Poseidon2Permutation<Params, Builder>::matrix_multiplication_internal(State& input)
-    requires IsSimulator<Builder>
-{
-    // for t = 4
-    auto sum = input[0];
-    for (size_t i = 1; i < t; ++i) {
-        sum += input[i];
-    }
-    for (size_t i = 0; i < t; ++i) {
-        input[i] *= Params::internal_matrix_diagonal[i]; // internal_matrix_diagonal[i];
-        input[i] += sum;
-    }
-}
-
 /**
  * @brief Separate function to do just the first linear layer (equivalent to external matrix mul).
  * @details We use 6 arithmetic gates to implement:
@@ -318,6 +228,5 @@ void Poseidon2Permutation<Params, Builder>::matrix_multiplication_external(
 
 template class Poseidon2Permutation<crypto::Poseidon2Bn254ScalarFieldParams, MegaCircuitBuilder>;
 template class Poseidon2Permutation<crypto::Poseidon2Bn254ScalarFieldParams, UltraCircuitBuilder>;
-template class Poseidon2Permutation<crypto::Poseidon2Bn254ScalarFieldParams, CircuitSimulatorBN254>;
 
-} // namespace bb::stdlib
+} // namespace bb::stdlib

barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2.test.cpp

@@ -50,19 +50,7 @@ template <typename Params, typename Builder> class Poseidon2Permutation {
      * @param input
      * @return State
      */
-    static State permutation(Builder* builder, const State& input)
-        requires(!IsSimulator<Builder>);
-    static State permutation(Builder* builder, const State& input)
-        requires IsSimulator<Builder>;
-
-    static void add_round_constants(State& input, const RoundConstants& rc)
-        requires IsSimulator<Builder>;
-    static void apply_sbox(State& input)
-        requires IsSimulator<Builder>;
-    static void apply_single_sbox(field_t<Builder>& input)
-        requires IsSimulator<Builder>;
-    static void matrix_multiplication_internal(State& input)
-        requires IsSimulator<Builder>;
+    static State permutation(Builder* builder, const State& input);
 
     /**
      * @brief Separate function to do just the first linear layer (equivalent to external matrix mul).
@@ -80,4 +68,4 @@ template <typename Params, typename Builder> class Poseidon2Permutation {
     static void matrix_multiplication_external(Builder* builder, State& state);
 };
 
-} // namespace bb::stdlib
+} // namespace bb::stdlib

barretenberg/cpp/src/barretenberg/stdlib/hash/poseidon2/poseidon2_permutation.cpp

@@ -59,6 +59,4 @@ DeciderRecursiveVerifier_<Flavor>::AggregationObject DeciderRecursiveVerifier_<F
 
 template class DeciderRecursiveVerifier_<bb::MegaRecursiveFlavor_<MegaCircuitBuilder>>;
 template class DeciderRecursiveVerifier_<bb::MegaRecursiveFlavor_<UltraCircuitBuilder>>;
-template class DeciderRecursiveVerifier_<bb::UltraRecursiveFlavor_<CircuitSimulatorBN254>>;
-template class DeciderRecursiveVerifier_<bb::MegaRecursiveFlavor_<CircuitSimulatorBN254>>;
 } // namespace bb::stdlib::recursion::honk