chore: rm dummy values from mega wires (#22453)

historically, we would fill the top of ultra and mega circuits with non-zero values to ensure that witness and selector commitments are not points at infinity. we reached the point where it's no longer needed

---------

Co-authored-by: AztecBot <tech@aztec-labs.com>

Author: iakovenkos

barretenberg/cpp/scripts/test_chonk_standalone_vks_havent_changed.sh

@@ -21,7 +21,7 @@ script_path="$root/barretenberg/cpp/scripts/test_chonk_standalone_vks_havent_cha
 # - Generate a hash for versioning: sha256sum bb-chonk-inputs.tar.gz
 # - Upload the compressed results: aws s3 cp bb-chonk-inputs.tar.gz s3://aztec-ci-artifacts/protocol/bb-chonk-inputs-[hash(0:8)].tar.gz
 # Note: In case of the "Test suite failed to run ... Unexpected token 'with' " error, need to run: docker pull aztecprotocol/build:3.0
-pinned_short_hash="4e8b472a"
+pinned_short_hash="ae9c2d06"
 pinned_chonk_inputs_url="https://aztec-ci-artifacts.s3.us-east-2.amazonaws.com/protocol/bb-chonk-inputs-${pinned_short_hash}.tar.gz"
 
 function update_pinned_hash_in_script {

barretenberg/cpp/src/barretenberg/bbapi/bbapi_chonk.cpp

@@ -312,7 +312,7 @@ ChonkStats::Response ChonkStats::execute([[maybe_unused]] BBApiRequest& request)
 
     // Create and finalize circuit
     auto builder = acir_format::create_circuit<MegaCircuitBuilder>(program, metadata);
-    builder.finalize_circuit(/*ensure_nonzero=*/true);
+    builder.finalize_circuit();
 
     // Set response values
     response.acir_opcodes = program.constraints.num_acir_opcodes;

barretenberg/cpp/src/barretenberg/bbapi/bbapi_ultra_honk.cpp

@@ -176,7 +176,7 @@ CircuitStats::Response _stats(std::vector<uint8_t>&& bytecode, bool include_gate
 
     acir_format::AcirProgram program{ std::move(constraint_system), {} };
     auto builder = acir_format::create_circuit<Circuit>(program, metadata);
-    builder.finalize_circuit(/*ensure_nonzero=*/true);
+    builder.finalize_circuit();
 
     response.num_gates = static_cast<uint32_t>(builder.get_finalized_total_circuit_size());
     response.num_gates_dyadic = static_cast<uint32_t>(builder.get_circuit_subgroup_size(response.num_gates));

barretenberg/cpp/src/barretenberg/benchmark/ultra_bench/mock_circuits.hpp

@@ -26,7 +26,7 @@ void generate_basic_arithmetic_circuit_with_target_gates(Builder& builder, size_
     stdlib::field_t c(&builder);
     // Ensure the circuit is filled but finalisation doesn't make the circuit size go to the next power of two
     const size_t GATE_COUNT_BUFFER = 1000; // Since we're using an estimate, let's add an error term in case.
-    size_t current_gates = builder.get_num_finalized_gates_inefficient(/*ensure_nonzero=*/false);
+    size_t current_gates = builder.get_num_finalized_gates_inefficient();
 
     if (target_gate_count <= current_gates + GATE_COUNT_BUFFER) {
         throw_or_abort("Target gate count is too low.");
@@ -41,7 +41,7 @@ void generate_basic_arithmetic_circuit_with_target_gates(Builder& builder, size_
         b = c * c;
     }
 
-    size_t est_gate_count = builder.get_num_finalized_gates_inefficient(/*ensure_nonzero=*/false);
+    size_t est_gate_count = builder.get_num_finalized_gates_inefficient();
     BB_ASSERT_LTE(est_gate_count,
                   target_gate_count - GATE_COUNT_BUFFER,
                   "Check that the finalized gate count won't exceed the desired gate count.");

barretenberg/cpp/src/barretenberg/boomerang_value_detection/graph_description_bigfield.test.cpp

@@ -387,7 +387,7 @@ TEST(boomerang_bigfield, test_graph_description_mult_madd_function)
     }
     fq_ct f = fq_ct::mult_madd(mul_left, mul_right, to_add);
     fix_bigfield_element(f);
-    builder.finalize_circuit(false);
+    builder.finalize_circuit();
     auto graph = StaticAnalyzer(builder);
     auto variables_in_one_gate = graph.get_variables_in_one_gate();
     EXPECT_EQ(variables_in_one_gate.size(), 0);
@@ -412,7 +412,7 @@ TEST(boomerang_bigfield, test_graph_description_constructor_high_low_bits)
         fq_ct::create_from_u512_as_witness(&builder, uint512_t(uint256_t(mul_right_value)));
     fq_ct product = mul_left * mul_right;
     fix_bigfield_element(product);
-    builder.finalize_circuit(false);
+    builder.finalize_circuit();
     auto graph = StaticAnalyzer(builder);
     auto connected_components = graph.find_connected_components();
     auto variables_in_one_gate = graph.get_variables_in_one_gate();

barretenberg/cpp/src/barretenberg/boomerang_value_detection/graph_description_ipa_recursive.test.cpp

@@ -99,7 +99,7 @@ class BoomerangIPARecursiveTests : public CommitmentTest<NativeCurve> {
 
         RecursiveIPA::reduce_verify(stdlib_claim, stdlib_transcript);
         stdlib::recursion::honk::DefaultIO<Builder>::add_default(builder);
-        builder.finalize_circuit(/*ensure_nonzero=*/true);
+        builder.finalize_circuit();
         return builder;
     }
     // flag to determine what type of polynomial to generate
@@ -172,7 +172,7 @@ class BoomerangIPARecursiveTests : public CommitmentTest<NativeCurve> {
         output_claim.set_public();
         output_claim.commitment.fix_witness();
         builder.ipa_proof = ipa_proof;
-        builder.finalize_circuit(/*ensure_nonzero=*/false);
+        builder.finalize_circuit();
         EXPECT_TRUE(CircuitChecker::check(builder));
 
         const OpeningPair<NativeCurve> opening_pair{ bb::fq(output_claim.opening_pair.challenge.get_value()),
@@ -206,7 +206,7 @@ TEST_F(BoomerangIPARecursiveTests, FullRecursiveVerifierMediumRandom)
     VerifierCommitmentKey<Curve> stdlib_pcs_vkey(&builder, poly_length, this->vk());
     auto result = RecursiveIPA::full_verify_recursive(stdlib_pcs_vkey, stdlib_claim, stdlib_transcript);
     EXPECT_TRUE(result);
-    builder.finalize_circuit(/*ensure_nonzero=*/true);
+    builder.finalize_circuit();
 
     auto tool = StaticAnalyzer(builder);
     auto tool_results = tool.analyze_circuit();
@@ -261,7 +261,7 @@ TEST_F(BoomerangIPARecursiveTests, AccumulationAndFullRecursiveVerifierMediumRan
     auto [output_claim, ipa_proof] = RecursiveIPA::accumulate(this->ck(), transcript_1, claim_1, transcript_2, claim_2);
     output_claim.set_public();
     builder.ipa_proof = ipa_proof;
-    builder.finalize_circuit(/*ensure_nonzero=*/false);
+    builder.finalize_circuit();
 
     Builder root_rollup;
     // Fully recursively verify this proof to check it.
@@ -274,7 +274,7 @@ TEST_F(BoomerangIPARecursiveTests, AccumulationAndFullRecursiveVerifierMediumRan
         Curve::ScalarField::create_from_u512_as_witness(&root_rollup, output_claim.opening_pair.evaluation.get_value());
     ipa_claim.commitment = Curve::AffineElement::from_witness(&root_rollup, output_claim.commitment.get_value());
     auto result = RecursiveIPA::full_verify_recursive(stdlib_pcs_vkey, ipa_claim, stdlib_verifier_transcript);
-    root_rollup.finalize_circuit(/*ensure_nonzero=*/true);
+    root_rollup.finalize_circuit();
     EXPECT_TRUE(result);
 
     auto tool = StaticAnalyzer(root_rollup);

barretenberg/cpp/src/barretenberg/chonk/chonk.test.cpp

@@ -405,7 +405,7 @@ HEAVY_TEST(ChonkKernelCapacity, MaxCapacityPassing)
 {
     bb::srs::init_file_crs_factory(bb::srs::bb_crs_path());
 
-    const size_t NUM_APP_CIRCUITS = 18;
+    const size_t NUM_APP_CIRCUITS = 21;
     auto [proof, vk] = ChonkTests::accumulate_and_prove_ivc(NUM_APP_CIRCUITS);
 
     bool verified = ChonkTests::verify_chonk(proof, vk);

barretenberg/cpp/src/barretenberg/circuit_checker/mega_circuit_builder.test.cpp

@@ -228,7 +228,7 @@ TEST(MegaCircuitBuilder, EccOpBlockIsFirstInTrace)
     auto c = builder.add_variable(builder.get_variable(a) + builder.get_variable(b));
     builder.create_add_gate({ a, b, c, 1, 1, -1, 0 });
 
-    builder.finalize_circuit(true);
+    builder.finalize_circuit();
     builder.blocks.compute_offsets(MegaFlavor::TRACE_OFFSET);
 
     // Verify ecc_op block starts at offset TRACE_OFFSET + NUM_ZERO_ROWS = NUM_ZERO_ROWS for non-ZK Mega.
@@ -247,23 +247,35 @@ TEST(MegaCircuitBuilder, EccOpBlockIsFirstInTrace)
 
 /**
  * @brief Verify that an empty circuit can be finalized and passes circuit checks
- * @details Finalization should add required gates to ensure all polynomials are non-zero
- * @note This is a "completeness" test; unlikely to be a use-case.
  */
 TEST(MegaCircuitBuilder, EmptyCircuitFinalization)
 {
     auto builder = MegaCircuitBuilder();
 
     // Completely empty circuit - no gates added
     EXPECT_EQ(builder.blocks.ecc_op.size(), 0);
+    EXPECT_FALSE(builder.circuit_finalized);
 
-    builder.finalize_circuit(true);
+    builder.finalize_circuit();
 
-    // After finalization, ecc_op block remains empty (no dummy ops needed)
+    EXPECT_TRUE(builder.circuit_finalized);
+
+    // After finalization: only zero_idx arithmetic gates and the corresponding public inputs remain.
+    // No dummy ecc ops, databus entries, or other gate types are added.
+    EXPECT_EQ(builder.blocks.arithmetic.size(), 4); // zero_idx setup
+    EXPECT_EQ(builder.blocks.pub_inputs.size(), 0);
     EXPECT_EQ(builder.blocks.ecc_op.size(), 0);
-    EXPECT_GT(builder.get_calldata().size(), 0) << "Finalization should add databus entries";
-    EXPECT_GT(builder.get_secondary_calldata().size(), 0);
-    EXPECT_GT(builder.get_return_data().size(), 0);
+    EXPECT_EQ(builder.blocks.busread.size(), 0);
+    EXPECT_EQ(builder.blocks.lookup.size(), 0);
+    EXPECT_EQ(builder.blocks.delta_range.size(), 0);
+    EXPECT_EQ(builder.blocks.elliptic.size(), 0);
+    EXPECT_EQ(builder.blocks.memory.size(), 0);
+    EXPECT_EQ(builder.blocks.nnf.size(), 0);
+    EXPECT_EQ(builder.blocks.poseidon2_external.size(), 0);
+    EXPECT_EQ(builder.blocks.poseidon2_internal.size(), 0);
+    EXPECT_EQ(builder.get_calldata().size(), 0);
+    EXPECT_EQ(builder.get_secondary_calldata().size(), 0);
+    EXPECT_EQ(builder.get_return_data().size(), 0);
 
     EXPECT_TRUE(CircuitChecker::check(builder));
 }

barretenberg/cpp/src/barretenberg/circuit_checker/ultra_circuit_builder_nonnative.test.cpp

@@ -24,8 +24,8 @@ class UltraCircuitBuilderNonNative : public ::testing::Test {
 
     // Number of NNF gates produced by a single partial multiplication
     static constexpr size_t NNF_GATES_PER_PARTIAL_MUL = 4;
-    // Number of padding gates added to NNF block by finalize_circuit(ensure_nonzero=true)
-    static constexpr size_t NNF_ENSURE_NONZERO_PADDING = 2;
+    // Number of padding gates added to NNF block by finalize_circuit()
+    static constexpr size_t NNF_ENSURE_NONZERO_PADDING = 0;
 
     // Generate 4 random field elements (one per limb)
     static std::array<fr, 4> random_limbs()
@@ -548,7 +548,7 @@ TEST_F(UltraCircuitBuilderNonNative, PartialMultiplicationDeduplication)
     EXPECT_TRUE(CircuitChecker::check(builder));
 
     // Finalize to check deduplication results
-    builder.finalize_circuit(/*ensure_nonzero=*/true);
+    builder.finalize_circuit();
 
     // After finalization, cache should be deduplicated to 1 entry
     EXPECT_EQ(builder.cached_partial_non_native_field_multiplications.size(), 1U);
@@ -597,7 +597,7 @@ TEST_F(UltraCircuitBuilderNonNative, PartialMultiplicationDedupeAssertEqual)
     EXPECT_TRUE(CircuitChecker::check(builder));
 
     // Finalize to check deduplication
-    builder.finalize_circuit(/*ensure_nonzero=*/true);
+    builder.finalize_circuit();
 
     // After finalization, should be deduplicated to 1 entry
     EXPECT_EQ(builder.cached_partial_non_native_field_multiplications.size(), 1U);
@@ -630,7 +630,7 @@ TEST_F(UltraCircuitBuilderNonNative, PartialMultiplicationMultipleDistinct)
     EXPECT_TRUE(CircuitChecker::check(builder));
 
     // Finalize to check gate counts
-    builder.finalize_circuit(/*ensure_nonzero=*/true);
+    builder.finalize_circuit();
 
     // After finalization, all distinct entries should remain (no deduplication)
     EXPECT_EQ(builder.cached_partial_non_native_field_multiplications.size(), num_multiplications);
@@ -666,7 +666,7 @@ TEST_F(UltraCircuitBuilderNonNative, ProcessNonNativeFieldMultiplicationsEmptyCa
     EXPECT_TRUE(CircuitChecker::check(builder));
 
     // Finalize to inspect NNF block
-    builder.finalize_circuit(/*ensure_nonzero=*/true);
+    builder.finalize_circuit();
 
     // Cache should still be empty
     EXPECT_EQ(builder.cached_partial_non_native_field_multiplications.size(), 0U);

barretenberg/cpp/src/barretenberg/circuit_checker/ultra_circuit_checker.cpp

@@ -23,7 +23,7 @@ UltraCircuitBuilder_<UltraExecutionTraceBlocks> UltraCircuitChecker::prepare_cir
     // Create a copy of the input circuit
     UltraCircuitBuilder_<UltraExecutionTraceBlocks> builder{ builder_in };
     if (!builder.circuit_finalized) { // avoid warnings about finalizing an already finalized circuit
-        builder.finalize_circuit(/*ensure_nonzero=*/true); // Test the ensure_nonzero gates as well
+        builder.finalize_circuit();
     }
 
     return builder;
@@ -40,7 +40,7 @@ MegaCircuitBuilder_<bb::fr> UltraCircuitChecker::prepare_circuit<MegaCircuitBuil
     builder.op_queue = std::make_shared<ECCOpQueue>(*builder.op_queue);
 
     if (!builder.circuit_finalized) { // avoid warnings about finalizing an already finalized circuit
-        builder.finalize_circuit(/*ensure_nonzero=*/true); // Test the ensure_nonzero gates as well
+        builder.finalize_circuit();
     }
 
     return builder;