feat: Single commitment key allocation in CIVC (#9974)

Previously we allocated the BN254 commitment key freely (I counted 11
times in one small ClientIVC test). This is unnecessary and could lead
to memory fragmentation. This PR implements size functions on a
`TraceSetting` object and, when structured traces are used, allocates
the commitment key at CIVC construction time. It passes this along to
dependent classes via a shared pointer.

I didn't handle the case of Grumpkin since it's not an issue.

I was curious to validate the effect in the browser directly through the
browser app in the ivc-integration test suite. Though it's tangential, I
updated that app to display console logs on the page for easy sharing.

barretenberg/cpp/src/barretenberg/client_ivc/client_ivc.cpp

@@ -176,10 +176,11 @@ void ClientIVC::accumulate(ClientCircuit& circuit, const std::shared_ptr<Verific
         proving_key = std::make_shared<DeciderProvingKey>(circuit, trace_settings);
         trace_usage_tracker = ExecutionTraceUsageTracker(trace_settings);
     } else {
-        proving_key = std::make_shared<DeciderProvingKey>(
-            circuit, trace_settings, fold_output.accumulator->proving_key.commitment_key);
+        proving_key = std::make_shared<DeciderProvingKey>(circuit, trace_settings);
     }
 
+    proving_key->proving_key.commitment_key = bn254_commitment_key;
+
     vinfo("getting honk vk... precomputed?: ", precomputed_vk);
     // Update the accumulator trace usage based on the present circuit
     trace_usage_tracker.update(circuit);
@@ -278,7 +279,7 @@ HonkProof ClientIVC::construct_and_prove_hiding_circuit()
     MergeProof merge_proof = goblin.prove_merge(builder);
     merge_verification_queue.emplace_back(merge_proof);
 
-    auto decider_pk = std::make_shared<DeciderProvingKey>(builder);
+    auto decider_pk = std::make_shared<DeciderProvingKey>(builder, TraceSettings(), bn254_commitment_key);
     honk_vk = std::make_shared<VerificationKey>(decider_pk->proving_key);
     MegaProver prover(decider_pk);
 
@@ -338,6 +339,7 @@ bool ClientIVC::verify(const Proof& proof)
 HonkProof ClientIVC::decider_prove() const
 {
     vinfo("prove decider...");
+    fold_output.accumulator->proving_key.commitment_key = bn254_commitment_key;
     MegaDeciderProver decider_prover(fold_output.accumulator);
     return decider_prover.construct_proof();
     vinfo("finished decider proving.");
@@ -352,11 +354,19 @@ HonkProof ClientIVC::decider_prove() const
 bool ClientIVC::prove_and_verify()
 {
     auto start = std::chrono::steady_clock::now();
-    auto proof = prove();
+    const auto proof = prove();
     auto end = std::chrono::steady_clock::now();
     auto diff = std::chrono::duration_cast<std::chrono::milliseconds>(end - start);
     vinfo("time to call ClientIVC::prove: ", diff.count(), " ms.");
-    return verify(proof);
+
+    start = end;
+    const bool verified = verify(proof);
+    end = std::chrono::steady_clock::now();
+
+    diff = std::chrono::duration_cast<std::chrono::milliseconds>(end - start);
+    vinfo("time to verify ClientIVC proof: ", diff.count(), " ms.");
+
+    return verified;
 }
 
 /**

barretenberg/cpp/src/barretenberg/client_ivc/client_ivc.hpp

@@ -98,8 +98,6 @@ class ClientIVC {
     using ProverFoldOutput = FoldingResult<Flavor>;
 
   public:
-    GoblinProver goblin;
-
     ProverFoldOutput fold_output; // prover accumulator and fold proof
 
     std::shared_ptr<DeciderVerificationKey> verifier_accumulator; // verifier accumulator
@@ -122,11 +120,19 @@ class ClientIVC {
     // Setting auto_verify_mode = true will cause kernel completion logic to be added to kernels automatically
     bool auto_verify_mode;
 
+    std::shared_ptr<typename MegaFlavor::CommitmentKey> bn254_commitment_key;
+
+    GoblinProver goblin;
+
     bool initialized = false; // Is the IVC accumulator initialized
 
     ClientIVC(TraceSettings trace_settings = {}, bool auto_verify_mode = false)
         : trace_settings(trace_settings)
         , auto_verify_mode(auto_verify_mode)
+        , bn254_commitment_key(trace_settings.structure.has_value()
+                                   ? std::make_shared<CommitmentKey<curve::BN254>>(trace_settings.dyadic_size())
+                                   : nullptr)
+        , goblin(bn254_commitment_key)
     {}
 
     void instantiate_stdlib_verification_queue(

barretenberg/cpp/src/barretenberg/dsl/acir_proofs/c_bind.cpp

@@ -236,7 +236,7 @@ WASM_EXPORT void acir_prove_and_verify_aztec_client(uint8_t const* acir_stack,
     }
     // TODO(#7371) dedupe this with the rest of the similar code
     // TODO(https://github.com/AztecProtocol/barretenberg/issues/1101): remove use of auto_verify_mode
-    ClientIVC ivc{ { E2E_FULL_TEST_STRUCTURE }, /*auto_verify_mode=*/true };
+    ClientIVC ivc{ { CLIENT_IVC_BENCH_STRUCTURE }, /*auto_verify_mode=*/true };
 
     // Accumulate the entire program stack into the IVC
     // TODO(https://github.com/AztecProtocol/barretenberg/issues/1116): remove manual setting of is_kernel once databus
@@ -267,6 +267,10 @@ WASM_EXPORT void acir_prove_and_verify_aztec_client(uint8_t const* acir_stack,
     bool result = ivc.prove_and_verify();
     info("verified?: ", result);
 
+    end = std::chrono::steady_clock::now();
+    diff = std::chrono::duration_cast<std::chrono::milliseconds>(end - start);
+    vinfo("time to construct, accumulate, prove and verify all circuits: ", diff.count());
+
     *verified = result;
 }
 

barretenberg/cpp/src/barretenberg/eccvm/eccvm_prover.cpp

@@ -104,8 +104,7 @@ void ECCVMProver::execute_relation_check_rounds()
         gate_challenges[idx] = transcript->template get_challenge<FF>("Sumcheck:gate_challenge_" + std::to_string(idx));
     }
 
-    auto commitment_key = std::make_shared<CommitmentKey>(Flavor::BATCHED_RELATION_PARTIAL_LENGTH);
-    zk_sumcheck_data = ZKSumcheckData<Flavor>(key->log_circuit_size, transcript, commitment_key);
+    zk_sumcheck_data = ZKSumcheckData<Flavor>(key->log_circuit_size, transcript, key->commitment_key);
 
     sumcheck_output = sumcheck.prove(key->polynomials, relation_parameters, alpha, gate_challenges, zk_sumcheck_data);
 }

barretenberg/cpp/src/barretenberg/goblin/goblin.hpp

@@ -51,6 +51,7 @@ class GoblinProver {
      */
 
     std::shared_ptr<OpQueue> op_queue = std::make_shared<OpQueue>();
+    std::shared_ptr<CommitmentKey<curve::BN254>> commitment_key;
 
     MergeProof merge_proof;
     GoblinProof goblin_proof;
@@ -70,11 +71,12 @@ class GoblinProver {
     GoblinAccumulationOutput accumulator; // Used only for ACIR methods for now
 
   public:
-    GoblinProver()
+    GoblinProver(const std::shared_ptr<CommitmentKey<curve::BN254>>& bn254_commitment_key = nullptr)
     { // Mocks the interaction of a first circuit with the op queue due to the inability to currently handle zero
       // commitments (https://github.com/AztecProtocol/barretenberg/issues/871) which would otherwise appear in the
       // first round of the merge protocol. To be removed once the issue has been resolved.
-        GoblinMockCircuits::perform_op_queue_interactions_for_mock_first_circuit(op_queue);
+        commitment_key = bn254_commitment_key ? bn254_commitment_key : nullptr;
+        GoblinMockCircuits::perform_op_queue_interactions_for_mock_first_circuit(op_queue, commitment_key);
     }
     /**
      * @brief Construct a MegaHonk proof and a merge proof for the present circuit.
@@ -160,7 +162,7 @@ class GoblinProver {
             merge_proof_exists = true;
         }
 
-        MergeProver merge_prover{ circuit_builder.op_queue };
+        MergeProver merge_prover{ circuit_builder.op_queue, commitment_key };
         return merge_prover.construct_proof();
     };
 
@@ -209,7 +211,7 @@ class GoblinProver {
 
             auto translator_builder =
                 std::make_unique<TranslatorBuilder>(translation_batching_challenge_v, evaluation_challenge_x, op_queue);
-            translator_prover = std::make_unique<TranslatorProver>(*translator_builder, transcript);
+            translator_prover = std::make_unique<TranslatorProver>(*translator_builder, transcript, commitment_key);
         }
 
         {

barretenberg/cpp/src/barretenberg/goblin/mock_circuits.hpp

@@ -121,7 +121,8 @@ class GoblinMockCircuits {
      *
      * @param op_queue
      */
-    static void perform_op_queue_interactions_for_mock_first_circuit(std::shared_ptr<bb::ECCOpQueue>& op_queue)
+    static void perform_op_queue_interactions_for_mock_first_circuit(
+        std::shared_ptr<bb::ECCOpQueue>& op_queue, std::shared_ptr<CommitmentKey> commitment_key = nullptr)
     {
         PROFILE_THIS();
 
@@ -134,11 +135,12 @@ class GoblinMockCircuits {
 
         // Manually compute the op queue transcript commitments (which would normally be done by the merge prover)
         bb::srs::init_crs_factory("../srs_db/ignition");
-        auto commitment_key = CommitmentKey(op_queue->get_current_size());
+        auto bn254_commitment_key =
+            commitment_key ? commitment_key : std::make_shared<CommitmentKey>(op_queue->get_current_size());
         std::array<Point, Flavor::NUM_WIRES> op_queue_commitments;
         size_t idx = 0;
         for (auto& entry : op_queue->get_aggregate_transcript()) {
-            op_queue_commitments[idx++] = commitment_key.commit({ 0, entry });
+            op_queue_commitments[idx++] = bn254_commitment_key->commit({ 0, entry });
         }
         // Store the commitment data for use by the prover of the next circuit
         op_queue->set_commitment_data(op_queue_commitments);

barretenberg/cpp/src/barretenberg/plonk_honk_shared/execution_trace/mega_execution_trace.hpp

@@ -59,8 +59,15 @@ template <typename T> struct MegaTraceBlockData {
         };
     }
 
-    static uint32_t size() { return 0; }
-    static uint32_t dyadic_size() { return 0; }
+    size_t size() const
+        requires std::same_as<T, uint32_t>
+    {
+        size_t result{ 0 };
+        for (const auto& block_size : get()) {
+            result += block_size;
+        }
+        return static_cast<size_t>(result);
+    }
 
     bool operator==(const MegaTraceBlockData& other) const = default;
 };
@@ -72,6 +79,15 @@ struct TraceSettings {
     // The size of the overflow block. Specified separately because it is allowed to be determined at runtime in the
     // context of VK computation
     uint32_t overflow_capacity = 0;
+
+    size_t size() const { return structure->size() + static_cast<size_t>(overflow_capacity); }
+
+    size_t dyadic_size() const
+    {
+        const size_t total_size = size();
+        const size_t lower_dyadic = 1 << numeric::get_msb(total_size);
+        return total_size > lower_dyadic ? lower_dyadic << 1 : lower_dyadic;
+    }
 };
 
 class MegaTraceBlock : public ExecutionTraceBlock<fr, /*NUM_WIRES_ */ 4, /*NUM_SELECTORS_*/ 14> {

barretenberg/cpp/src/barretenberg/stdlib_circuit_builders/mega_flavor.hpp

@@ -581,11 +581,12 @@ class MegaFlavor {
         VerificationKey(ProvingKey& proving_key)
         {
             set_metadata(proving_key);
-            if (proving_key.commitment_key == nullptr) {
-                proving_key.commitment_key = std::make_shared<CommitmentKey>(proving_key.circuit_size);
+            auto& ck = proving_key.commitment_key;
+            if (!ck || ck->srs->get_monomial_size() < proving_key.circuit_size) {
+                ck = std::make_shared<CommitmentKey>(proving_key.circuit_size);
             }
             for (auto [polynomial, commitment] : zip_view(proving_key.polynomials.get_precomputed(), this->get_all())) {
-                commitment = proving_key.commitment_key->commit(polynomial);
+                commitment = ck->commit(polynomial);
             }
         }
 

barretenberg/cpp/src/barretenberg/translator_vm/translator_prover.cpp

@@ -8,17 +8,18 @@
 
 namespace bb {
 
-TranslatorProver::TranslatorProver(CircuitBuilder& circuit_builder, const std::shared_ptr<Transcript>& transcript)
+TranslatorProver::TranslatorProver(CircuitBuilder& circuit_builder,
+                                   const std::shared_ptr<Transcript>& transcript,
+                                   std::shared_ptr<CommitmentKey> commitment_key)
     : dyadic_circuit_size(Flavor::compute_dyadic_circuit_size(circuit_builder))
     , mini_circuit_dyadic_size(Flavor::compute_mini_circuit_dyadic_size(circuit_builder))
     , transcript(transcript)
+    , key(std::make_shared<ProvingKey>(circuit_builder))
 {
     PROFILE_THIS();
 
-    // Compute total number of gates, dyadic circuit size, etc.
-    key = std::make_shared<ProvingKey>(circuit_builder);
+    key->commitment_key = commitment_key ? commitment_key : std::make_shared<CommitmentKey>(key->circuit_size);
     compute_witness(circuit_builder);
-    compute_commitment_key(key->circuit_size);
 }
 
 /**
@@ -159,9 +160,8 @@ void TranslatorProver::execute_relation_check_rounds()
         gate_challenges[idx] = transcript->template get_challenge<FF>("Sumcheck:gate_challenge_" + std::to_string(idx));
     }
 
-    // create masking polynomials for sumcheck round univariates and auxiliary data
-    auto commitment_key = std::make_shared<CommitmentKey>(Flavor::BATCHED_RELATION_PARTIAL_LENGTH);
-    zk_sumcheck_data = ZKSumcheckData<Flavor>(key->log_circuit_size, transcript, commitment_key);
+    // // create masking polynomials for sumcheck round univariates and auxiliary data
+    zk_sumcheck_data = ZKSumcheckData<Flavor>(key->log_circuit_size, transcript, key->commitment_key);
 
     sumcheck_output = sumcheck.prove(key->polynomials, relation_parameters, alpha, gate_challenges, zk_sumcheck_data);
 }

barretenberg/cpp/src/barretenberg/translator_vm/translator_prover.hpp

@@ -28,7 +28,9 @@ class TranslatorProver {
     size_t dyadic_circuit_size = 0;      // final power-of-2 circuit size
     size_t mini_circuit_dyadic_size = 0; // The size of the small circuit that contains non-range constraint relations
 
-    explicit TranslatorProver(CircuitBuilder& circuit_builder, const std::shared_ptr<Transcript>& transcript);
+    explicit TranslatorProver(CircuitBuilder& circuit_builder,
+                              const std::shared_ptr<Transcript>& transcript,
+                              std::shared_ptr<CommitmentKey> commitment_key = nullptr);
 
     void compute_witness(CircuitBuilder& circuit_builder);
     void compute_commitment_key(size_t circuit_size);

barretenberg/cpp/src/barretenberg/ultra_honk/decider_prover.cpp

@@ -57,33 +57,31 @@ template <IsUltraFlavor Flavor> void DeciderProver_<Flavor>::execute_relation_ch
  */
 template <IsUltraFlavor Flavor> void DeciderProver_<Flavor>::execute_pcs_rounds()
 {
-    if (proving_key->proving_key.commitment_key == nullptr) {
-        proving_key->proving_key.commitment_key =
-            std::make_shared<CommitmentKey>(proving_key->proving_key.circuit_size);
-    }
-    vinfo("made commitment key");
     using OpeningClaim = ProverOpeningClaim<Curve>;
 
+    auto& ck = proving_key->proving_key.commitment_key;
+    ck = ck ? ck : std::make_shared<CommitmentKey>(proving_key->proving_key.circuit_size);
+
     OpeningClaim prover_opening_claim;
     if constexpr (!Flavor::HasZK) {
         prover_opening_claim = ShpleminiProver_<Curve>::prove(proving_key->proving_key.circuit_size,
                                                               proving_key->proving_key.polynomials.get_unshifted(),
                                                               proving_key->proving_key.polynomials.get_to_be_shifted(),
                                                               sumcheck_output.challenge,
-                                                              proving_key->proving_key.commitment_key,
+                                                              ck,
                                                               transcript);
     } else {
         prover_opening_claim = ShpleminiProver_<Curve>::prove(proving_key->proving_key.circuit_size,
                                                               proving_key->proving_key.polynomials.get_unshifted(),
                                                               proving_key->proving_key.polynomials.get_to_be_shifted(),
                                                               sumcheck_output.challenge,
-                                                              proving_key->proving_key.commitment_key,
+                                                              ck,
                                                               transcript,
                                                               zk_sumcheck_data.libra_univariates_monomial,
                                                               sumcheck_output.claimed_libra_evaluations);
     }
     vinfo("executed multivariate-to-univarite reduction");
-    PCS::compute_opening_proof(proving_key->proving_key.commitment_key, prover_opening_claim, transcript);
+    PCS::compute_opening_proof(ck, prover_opening_claim, transcript);
     vinfo("computed opening proof");
 }
 

barretenberg/cpp/src/barretenberg/ultra_honk/decider_proving_key.hpp

@@ -45,12 +45,12 @@ template <IsUltraFlavor Flavor> class DeciderProvingKey_ {
     std::vector<FF> gate_challenges;
     // The target sum, which is typically nonzero for a ProtogalaxyProver's accmumulator
     FF target_sum;
-
     size_t final_active_wire_idx{ 0 }; // idx of last non-trivial wire value in the trace
+    size_t dyadic_circuit_size{ 0 };   // final power-of-2 circuit size
 
     DeciderProvingKey_(Circuit& circuit,
                        TraceSettings trace_settings = {},
-                       std::shared_ptr<typename Flavor::CommitmentKey> commitment_key = nullptr)
+                       std::shared_ptr<CommitmentKey> commitment_key = nullptr)
         : is_structured(trace_settings.structure.has_value())
     {
         PROFILE_THIS_NAME("DeciderProvingKey(Circuit&)");
@@ -105,6 +105,7 @@ template <IsUltraFlavor Flavor> class DeciderProvingKey_ {
             if ((IsMegaFlavor<Flavor> && !is_structured) || (is_structured && circuit.blocks.has_overflow)) {
                 // Allocate full size polynomials
                 proving_key.polynomials = typename Flavor::ProverPolynomials(dyadic_circuit_size);
+                vinfo("allocated polynomials object in proving key");
             } else { // Allocate only a correct amount of memory for each polynomial
                 // Allocate the wires and selectors polynomials
                 {
@@ -262,6 +263,7 @@ template <IsUltraFlavor Flavor> class DeciderProvingKey_ {
                         /* size=*/dyadic_circuit_size, /*virtual size=*/dyadic_circuit_size, /*start_idx=*/0);
                 }
             }
+            vinfo("allocated polynomials object in proving key");
             // We can finally set the shifted polynomials now that all of the to_be_shifted polynomials are
             // defined.
             proving_key.polynomials.set_shifted(); // Ensure shifted wires are set correctly
@@ -334,7 +336,6 @@ template <IsUltraFlavor Flavor> class DeciderProvingKey_ {
   private:
     static constexpr size_t num_zero_rows = Flavor::has_zero_row ? 1 : 0;
     static constexpr size_t NUM_WIRES = Circuit::NUM_WIRES;
-    size_t dyadic_circuit_size = 0; // final power-of-2 circuit size
 
     size_t compute_dyadic_size(Circuit&);
 

barretenberg/cpp/src/barretenberg/ultra_honk/merge_prover.cpp

@@ -10,13 +10,14 @@ namespace bb {
  *
  */
 template <class Flavor>
-MergeProver_<Flavor>::MergeProver_(const std::shared_ptr<ECCOpQueue>& op_queue)
+MergeProver_<Flavor>::MergeProver_(const std::shared_ptr<ECCOpQueue>& op_queue,
+                                   std::shared_ptr<CommitmentKey> commitment_key)
     : op_queue(op_queue)
 {
     // Update internal size data in the op queue that allows for extraction of e.g. previous aggregate transcript
     op_queue->set_size_data();
-    // Get the appropriate commitment based on the updated ultra ops size
-    pcs_commitment_key = std::make_shared<CommitmentKey>(op_queue->get_current_size());
+    pcs_commitment_key =
+        commitment_key ? commitment_key : std::make_shared<CommitmentKey>(op_queue->get_current_size());
 }
 
 /**

barretenberg/cpp/src/barretenberg/ultra_honk/merge_prover.hpp

@@ -27,7 +27,8 @@ template <typename Flavor> class MergeProver_ {
   public:
     std::shared_ptr<Transcript> transcript;
 
-    explicit MergeProver_(const std::shared_ptr<ECCOpQueue>&);
+    explicit MergeProver_(const std::shared_ptr<ECCOpQueue>& op_queue,
+                          std::shared_ptr<CommitmentKey> commitment_key = nullptr);
 
     BB_PROFILE HonkProof construct_proof();
 

barretenberg/cpp/src/barretenberg/ultra_honk/oink_prover.cpp

@@ -58,8 +58,10 @@ template <IsUltraFlavor Flavor> void OinkProver<Flavor>::prove()
     // Generate relation separators alphas for sumcheck/combiner computation
     proving_key->alphas = generate_alphas_round();
 
+#ifndef __wasm__
     // Free the commitment key
     proving_key->proving_key.commitment_key = nullptr;
+#endif
 }
 
 /**