chore: simplify handling of pub inputs block (#11747)

Simplifies handling of public inputs by populating `pub_inputs` block in
`finalize_circuit()` which ensures that all blocks are complete prior to
any prover work. Also improves some of the log info related to the
overflow mechanism.

closes: AztecProtocol/barretenberg#1220

barretenberg/cpp/src/barretenberg/benchmark/mega_memory_bench/mega_memory.bench.cpp

@@ -295,14 +295,7 @@ void fill_trace(State& state, TraceSettings settings)
     fill_lookup_block(builder);
 
     {
-        // finalize doesn't populate public inputs block, so copy to verify that the block is being filled well.
-        // otherwise the pk construction will overflow the block
-        // alternative: add to finalize or add a flag to check whether PIs have already been populated
-        auto builder_copy = builder;
-        builder_copy.finalize_circuit(/* ensure_nonzero */ false);
-        DeciderProvingKey::Trace::populate_public_inputs_block(builder_copy);
-
-        for (const auto [label, block] : zip_view(builder_copy.blocks.get_labels(), builder_copy.blocks.get())) {
+        for (const auto [label, block] : zip_view(builder.blocks.get_labels(), builder.blocks.get())) {
             bool overfilled = block.size() >= block.get_fixed_size();
             if (overfilled) {
                 vinfo(label, " overfilled");

barretenberg/cpp/src/barretenberg/examples/join_split/join_split.test.cpp

@@ -703,7 +703,7 @@ TEST_F(join_split_tests, test_0_input_notes_and_detect_circuit_change)
     // The below part detects any changes in the join-split circuit
     constexpr size_t DYADIC_CIRCUIT_SIZE = 1 << 16;
 
-    constexpr uint256_t CIRCUIT_HASH("0x48687216f00a81d2a0f64f0a10cce056fce2ad13c47f8329229eb3712d3f7566");
+    constexpr uint256_t CIRCUIT_HASH("0x103eeb052dd7c2f8ebf531bdfadb7d3cee0ab95371289f6d507beaa24b210fba");
 
     const uint256_t circuit_hash = circuit.hash_circuit();
     // circuit is finalized now

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

@@ -220,6 +220,16 @@ class MegaExecutionTraceBlocks : public MegaTraceBlockData<MegaTraceBlock> {
         info("");
     }
 
+    // Get cumulative size of all blocks
+    size_t get_total_content_size()
+    {
+        size_t total_size(0);
+        for (const auto& block : this->get()) {
+            total_size += block.size();
+        }
+        return total_size;
+    }
+
     size_t get_structured_dyadic_size() const
     {
         size_t total_size = 1; // start at 1 because the 0th row is unused for selectors for Honk

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

@@ -125,6 +125,16 @@ class UltraExecutionTraceBlocks : public UltraTraceBlockData<UltraTraceBlock> {
         info("overflow :\t", this->overflow.size());
     }
 
+    // Get cumulative size of all blocks
+    size_t get_total_content_size()
+    {
+        size_t total_size(0);
+        for (const auto& block : this->get()) {
+            total_size += block.size();
+        }
+        return total_size;
+    }
+
     size_t get_structured_dyadic_size()
     {
         size_t total_size = 1; // start at 1 because the 0th row is unused for selectors for Honk

barretenberg/cpp/src/barretenberg/stdlib_circuit_builders/ultra_circuit_builder.cpp

@@ -52,6 +52,7 @@ void UltraCircuitBuilder_<ExecutionTrace>::finalize_circuit(const bool ensure_no
         process_RAM_arrays();
         process_range_lists();
 #endif
+        populate_public_inputs_block();
         circuit_finalized = true;
     } else {
         // Gates added after first call to finalize will not be processed since finalization is only performed once
@@ -1794,6 +1795,24 @@ std::array<uint32_t, 2> UltraCircuitBuilder_<ExecutionTrace>::evaluate_non_nativ
     return std::array<uint32_t, 2>{ lo_1_idx, hi_3_idx };
 }
 
+/**
+ * @brief Copy the public input idx data into the public inputs trace block
+ * @note
+ */
+template <typename ExecutionTrace> void UltraCircuitBuilder_<ExecutionTrace>::populate_public_inputs_block()
+{
+    PROFILE_THIS_NAME("populate_public_inputs_block");
+
+    // Update the public inputs block
+    for (const auto& idx : this->public_inputs) {
+        // first two wires get a copy of the public inputs
+        blocks.pub_inputs.populate_wires(idx, idx, this->zero_idx, this->zero_idx);
+        for (auto& selector : this->blocks.pub_inputs.selectors) {
+            selector.emplace_back(0);
+        }
+    }
+}
+
 /**
  * @brief Called in `compute_proving_key` when finalizing circuit.
  * Iterates over the cached_non_native_field_multiplication objects,

barretenberg/cpp/src/barretenberg/stdlib_circuit_builders/ultra_circuit_builder.hpp

@@ -332,6 +332,8 @@ class UltraCircuitBuilder_ : public CircuitBuilderBase<typename ExecutionTrace_:
 
     std::vector<fr> ipa_proof;
 
+    void populate_public_inputs_block();
+
     void process_non_native_field_multiplications();
     UltraCircuitBuilder_(const size_t size_hint = 0)
         : CircuitBuilderBase<FF>(size_hint)

barretenberg/cpp/src/barretenberg/trace_to_polynomials/trace_to_polynomials.cpp

@@ -8,25 +8,6 @@
 #include "barretenberg/stdlib_circuit_builders/ultra_zk_flavor.hpp"
 namespace bb {
 
-template <class Flavor> void TraceToPolynomials<Flavor>::populate_public_inputs_block(Builder& builder)
-{
-    PROFILE_THIS_NAME("populate_public_inputs_block");
-
-    // Update the public inputs block
-    for (const auto& idx : builder.public_inputs) {
-        for (size_t wire_idx = 0; wire_idx < NUM_WIRES; ++wire_idx) {
-            if (wire_idx < 2) { // first two wires get a copy of the public inputs
-                builder.blocks.pub_inputs.wires[wire_idx].emplace_back(idx);
-            } else { // the remaining wires get zeros
-                builder.blocks.pub_inputs.wires[wire_idx].emplace_back(builder.zero_idx);
-            }
-        }
-        for (auto& selector : builder.blocks.pub_inputs.selectors) {
-            selector.emplace_back(0);
-        }
-    }
-}
-
 template <class Flavor>
 void TraceToPolynomials<Flavor>::populate(Builder& builder,
                                           typename Flavor::ProvingKey& proving_key,
@@ -89,11 +70,6 @@ typename TraceToPolynomials<Flavor>::TraceData TraceToPolynomials<Flavor>::const
 
     PROFILE_THIS_NAME("construct_trace_data");
 
-    if constexpr (IsPlonkFlavor<Flavor>) {
-        // Complete the public inputs execution trace block from builder.public_inputs
-        populate_public_inputs_block(builder);
-    }
-
     TraceData trace_data{ builder, proving_key };
 
     uint32_t offset = Flavor::has_zero_row ? 1 : 0; // Offset at which to place each block in the trace polynomials

barretenberg/cpp/src/barretenberg/trace_to_polynomials/trace_to_polynomials.hpp

@@ -78,14 +78,6 @@ template <class Flavor> class TraceToPolynomials {
      */
     static void populate(Builder& builder, ProvingKey&, bool is_structured = false);
 
-    /**
-     * @brief Populate the public inputs block
-     * @details The first two wires are a copy of the public inputs and the other wires and all selectors are zero
-     *
-     * @param circuit
-     */
-    static void populate_public_inputs_block(Builder& builder);
-
   private:
     /**
      * @brief Add the memory records indicating which rows correspond to RAM/ROM reads/writes

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

@@ -17,10 +17,7 @@ template <IsUltraFlavor Flavor> size_t DeciderProvingKey_<Flavor>::compute_dyadi
     const size_t min_size_due_to_lookups = circuit.get_tables_size();
 
     // minimum size of execution trace due to everything else
-    size_t min_size_of_execution_trace = circuit.public_inputs.size() + circuit.num_gates;
-    if constexpr (IsMegaFlavor<Flavor>) {
-        min_size_of_execution_trace += circuit.blocks.ecc_op.size();
-    }
+    size_t min_size_of_execution_trace = circuit.blocks.get_total_content_size();
 
     // The number of gates is the maximum required by the lookup argument or everything else, plus an optional zero row
     // to allow for shifts.
@@ -237,6 +234,7 @@ void DeciderProvingKey_<Flavor>::construct_databus_polynomials(Circuit& circuit)
  */
 template <IsUltraFlavor Flavor>
 void DeciderProvingKey_<Flavor>::move_structured_trace_overflow_to_overflow_block(Circuit& circuit)
+    requires IsMegaFlavor<Flavor>
 {
     auto& blocks = circuit.blocks;
     auto& overflow_block = circuit.blocks.overflow;
@@ -252,9 +250,19 @@ void DeciderProvingKey_<Flavor>::move_structured_trace_overflow_to_overflow_bloc
         uint32_t fixed_block_size = block.get_fixed_size();
         if (block_size > fixed_block_size && block != overflow_block) {
             // Disallow overflow in blocks that are not expected to be used by App circuits
-            ASSERT(!block.is_pub_inputs);
-            if constexpr (IsMegaFlavor<Flavor>) {
-                ASSERT(block != blocks.ecc_op);
+            if (block.is_pub_inputs) {
+                info("WARNING: Number of public inputs (",
+                     block_size,
+                     ") cannot exceed capacity specified in structured trace: ",
+                     fixed_block_size);
+                ASSERT(false);
+            }
+            if (block == blocks.ecc_op) {
+                info("WARNING: Number of ecc op gates (",
+                     block_size,
+                     ") cannot exceed capacity specified in structured trace: ",
+                     fixed_block_size);
+                ASSERT(false);
             }
 
             // Set has_overflow to true if at least one block exceeds its capacity
@@ -264,7 +272,6 @@ void DeciderProvingKey_<Flavor>::move_structured_trace_overflow_to_overflow_bloc
             // the block containing RAM/ROM gates overflows, the indices of the corresponding gates in the memory
             // records need to be updated to reflect their new position in the overflow block
             if (block.has_ram_rom) {
-
                 uint32_t overflow_cur_idx = overflow_block.trace_offset + static_cast<uint32_t>(overflow_block.size());
                 overflow_cur_idx -= block.trace_offset; // we'll add block.trace_offset to everything later
                 uint32_t offset = overflow_cur_idx + 1; // +1 accounts for duplication of final gate
@@ -315,12 +322,7 @@ void DeciderProvingKey_<Flavor>::move_structured_trace_overflow_to_overflow_bloc
 
     // Set the fixed size of the overflow block to its current size
     if (overflow_block.size() > overflow_block.get_fixed_size()) {
-        info("WARNING: Structured trace overflowed beyond the prescribed fixed overflow size. This is valid in the "
-             "context of one-off VK/proof generation but not in the IVC setting. \nPrescribed overflow size: ",
-             overflow_block.get_fixed_size(),
-             ". \nActual overflow size: ",
-             overflow_block.size(),
-             "\n");
+        info("WARNING: Structured trace overflow mechanism in use. Performance may be degraded!");
         overflow_block.fixed_size = static_cast<uint32_t>(overflow_block.size());
         blocks.summarize();
     }

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

@@ -81,10 +81,7 @@ template <IsUltraFlavor Flavor> class DeciderProvingKey_ {
              ". Log dyadic circuit size: ",
              numeric::get_msb(dyadic_circuit_size),
              ".");
-
-        // Complete the public inputs execution trace block from circuit.public_inputs
-        Trace::populate_public_inputs_block(circuit);
-        circuit.blocks.compute_offsets(is_structured);
+        circuit.blocks.compute_offsets(is_structured); // compute offset of each block within the trace
 
         // Find index of last non-trivial wire value in the trace
         for (auto& block : circuit.blocks.get()) {
@@ -227,7 +224,8 @@ template <IsUltraFlavor Flavor> class DeciderProvingKey_ {
     void construct_databus_polynomials(Circuit&)
         requires HasDataBus<Flavor>;
 
-    static void move_structured_trace_overflow_to_overflow_block(Circuit& circuit);
+    static void move_structured_trace_overflow_to_overflow_block(Circuit& circuit)
+        requires IsMegaFlavor<Flavor>;
 };
 
 } // namespace bb