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merged 2 commits into from
Oct 23, 2025
Merged

chore: static batch inverses #17899

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9ac076e
Precomputed inverses should be stored in a static const variable
jeanmon Oct 23, 2025
3c34201
Use lambda
jeanmon Oct 23, 2025
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58 changes: 37 additions & 21 deletions barretenberg/cpp/src/barretenberg/vm2/tracegen/alu_trace.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -8,34 +8,41 @@
#include "barretenberg/numeric/uint256/uint256.hpp"
#include "barretenberg/vm2/common/memory_types.hpp"
#include "barretenberg/vm2/common/tagged_value.hpp"
#include "barretenberg/vm2/generated/columns.hpp"
#include "barretenberg/vm2/generated/relations/lookups_alu.hpp"
#include "barretenberg/vm2/simulation/events/alu_event.hpp"
#include "barretenberg/vm2/simulation/events/event_emitter.hpp"
#include "barretenberg/vm2/simulation/lib/uint_decomposition.hpp"
#include "barretenberg/vm2/tracegen/lib/instruction_spec.hpp"
#include "barretenberg/vm2/tracegen/lib/interaction_def.hpp"

namespace bb::avm2::tracegen {

AluTraceBuilder::AluTraceBuilder()
namespace {

// Get tag inverse for a given index using static precomputed inverses.
const FF& get_tag_inverse(size_t index)
{
for (size_t i = 0; i < NUM_TAGS; i++) {
tag_inverses.at(i) = FF(i);
}
FF::batch_invert(tag_inverses);
constexpr size_t NUM_TAGS = static_cast<size_t>(MemoryTag::MAX) + 1;
static const std::array<FF, NUM_TAGS> tag_inverses = []() {
std::array<FF, NUM_TAGS> inverses;
for (size_t i = 0; i < NUM_TAGS; i++) {
inverses.at(i) = FF(i);
}
FF::batch_invert(inverses);
return inverses;
}();

return tag_inverses.at(index);
}

FF AluTraceBuilder::get_tag_diff_inverse(const MemoryTag a_tag, const MemoryTag b_tag) const
FF get_tag_diff_inverse(const MemoryTag a_tag, const MemoryTag b_tag)
{
if (static_cast<uint8_t>(a_tag) >= static_cast<uint8_t>(b_tag)) {
return tag_inverses[static_cast<uint8_t>(a_tag) - static_cast<uint8_t>(b_tag)];
return get_tag_inverse(static_cast<uint8_t>(a_tag) - static_cast<uint8_t>(b_tag));
}

return -tag_inverses[static_cast<uint8_t>(b_tag) - static_cast<uint8_t>(a_tag)];
return -get_tag_inverse(static_cast<uint8_t>(b_tag) - static_cast<uint8_t>(a_tag));
}

std::vector<std::pair<Column, FF>> AluTraceBuilder::get_operation_specific_columns(
const simulation::AluEvent& event) const
std::vector<std::pair<Column, FF>> get_operation_specific_columns(const simulation::AluEvent& event)
{
const MemoryTag a_tag = event.a.get_tag();
bool is_ff = a_tag == MemoryTag::FF;
Expand Down Expand Up @@ -106,7 +113,8 @@ std::vector<std::pair<Column, FF>> AluTraceBuilder::get_operation_specific_colum
{ Column::alu_helper1, remainder },
{ Column::alu_constant_64, 64 },
{ Column::alu_sel_is_ff, is_ff },
{ Column::alu_tag_ff_diff_inv, tag_inverses[static_cast<uint8_t>(a_tag)] }, // Relies on MemoryTag::FF is 0
{ Column::alu_tag_ff_diff_inv,
get_tag_inverse(static_cast<uint8_t>(a_tag)) }, // Relies on MemoryTag::FF is 0
{ Column::alu_sel_is_u128, is_u128 },
{ Column::alu_tag_u128_diff_inv, get_tag_diff_inverse(a_tag, MemoryTag::U128) },
{ Column::alu_b_inv, div_0_error ? 0 : event.b.as_ff() }, // Will be inverted in batch later
Expand Down Expand Up @@ -136,7 +144,8 @@ std::vector<std::pair<Column, FF>> AluTraceBuilder::get_operation_specific_colum
{ Column::alu_sel_op_fdiv, 1 },
{ Column::alu_op_id, SUBTRACE_INFO_MAP.at(ExecutionOpCode::FDIV).subtrace_operation_id },
{ Column::alu_sel_is_ff, is_ff },
{ Column::alu_tag_ff_diff_inv, tag_inverses[static_cast<uint8_t>(a_tag)] }, // Relies on MemoryTag::FF is 0
{ Column::alu_tag_ff_diff_inv,
get_tag_inverse(static_cast<uint8_t>(a_tag)) }, // Relies on MemoryTag::FF is 0
{ Column::alu_b_inv, div_0_error ? 0 : event.b.as_ff() }, // Will be inverted in batch later
};
}
Expand All @@ -160,7 +169,8 @@ std::vector<std::pair<Column, FF>> AluTraceBuilder::get_operation_specific_colum
{ Column::alu_sel_is_ff, is_ff },
{ Column::alu_sel_ff_lt_ops, is_ff && no_tag_err },
{ Column::alu_sel_int_lt_ops, !is_ff && no_tag_err },
{ Column::alu_tag_ff_diff_inv, tag_inverses[static_cast<uint8_t>(a_tag)] }, // Relies on MemoryTag::FF is 0
{ Column::alu_tag_ff_diff_inv,
get_tag_inverse(static_cast<uint8_t>(a_tag)) }, // Relies on MemoryTag::FF is 0
};
case simulation::AluOperation::LTE:
return {
Expand All @@ -174,14 +184,16 @@ std::vector<std::pair<Column, FF>> AluTraceBuilder::get_operation_specific_colum
{ Column::alu_sel_is_ff, is_ff },
{ Column::alu_sel_ff_lt_ops, is_ff && no_tag_err },
{ Column::alu_sel_int_lt_ops, !is_ff && no_tag_err },
{ Column::alu_tag_ff_diff_inv, tag_inverses[static_cast<uint8_t>(a_tag)] }, // Relies on MemoryTag::FF is 0
{ Column::alu_tag_ff_diff_inv,
get_tag_inverse(static_cast<uint8_t>(a_tag)) }, // Relies on MemoryTag::FF is 0
};
case simulation::AluOperation::NOT: {
return {
{ Column::alu_sel_op_not, 1 },
{ Column::alu_op_id, SUBTRACE_INFO_MAP.at(ExecutionOpCode::NOT).subtrace_operation_id },
{ Column::alu_sel_is_ff, is_ff },
{ Column::alu_tag_ff_diff_inv, tag_inverses[static_cast<uint8_t>(a_tag)] }, // Relies on MemoryTag::FF is 0
{ Column::alu_tag_ff_diff_inv,
get_tag_inverse(static_cast<uint8_t>(a_tag)) }, // Relies on MemoryTag::FF is 0
};
}
case simulation::AluOperation::SHL: {
Expand All @@ -208,7 +220,8 @@ std::vector<std::pair<Column, FF>> AluTraceBuilder::get_operation_specific_colum
{ Column::alu_shift_lo_bits, shift_lo_bits },
{ Column::alu_two_pow_shift_lo_bits, static_cast<uint128_t>(1) << shift_lo_bits },
{ Column::alu_sel_is_ff, is_ff },
{ Column::alu_tag_ff_diff_inv, tag_inverses[static_cast<uint8_t>(a_tag)] }, // Relies on MemoryTag::FF is 0
{ Column::alu_tag_ff_diff_inv,
get_tag_inverse(static_cast<uint8_t>(a_tag)) }, // Relies on MemoryTag::FF is 0
{ Column::alu_op_id, SUBTRACE_INFO_MAP.at(ExecutionOpCode::SHL).subtrace_operation_id },
{ Column::alu_helper1, static_cast<uint128_t>(1) << b_num },
};
Expand Down Expand Up @@ -237,7 +250,8 @@ std::vector<std::pair<Column, FF>> AluTraceBuilder::get_operation_specific_colum
{ Column::alu_shift_lo_bits, shift_lo_bits },
{ Column::alu_two_pow_shift_lo_bits, static_cast<uint128_t>(1) << shift_lo_bits },
{ Column::alu_sel_is_ff, is_ff },
{ Column::alu_tag_ff_diff_inv, tag_inverses[static_cast<uint8_t>(a_tag)] }, // Relies on MemoryTag::FF is 0
{ Column::alu_tag_ff_diff_inv,
get_tag_inverse(static_cast<uint8_t>(a_tag)) }, // Relies on MemoryTag::FF is 0
{ Column::alu_op_id, SUBTRACE_INFO_MAP.at(ExecutionOpCode::SHR).subtrace_operation_id },
};
}
Expand Down Expand Up @@ -270,7 +284,7 @@ std::vector<std::pair<Column, FF>> AluTraceBuilder::get_operation_specific_colum
}
}

std::vector<std::pair<Column, FF>> AluTraceBuilder::get_tag_error_columns(const simulation::AluEvent& event) const
std::vector<std::pair<Column, FF>> get_tag_error_columns(const simulation::AluEvent& event)
{
const MemoryTag a_tag = event.a.get_tag();
const FF a_tag_ff = static_cast<FF>(static_cast<uint8_t>(a_tag));
Expand Down Expand Up @@ -305,6 +319,8 @@ std::vector<std::pair<Column, FF>> AluTraceBuilder::get_tag_error_columns(const
return {};
}

} // namespace

void AluTraceBuilder::process(const simulation::EventEmitterInterface<simulation::AluEvent>::Container& events,
TraceContainer& trace)
{
Expand Down
10 changes: 0 additions & 10 deletions barretenberg/cpp/src/barretenberg/vm2/tracegen/alu_trace.hpp
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Original file line number Diff line number Diff line change
@@ -1,6 +1,5 @@
#pragma once

#include "barretenberg/vm2/generated/columns.hpp"
#include "barretenberg/vm2/simulation/events/alu_event.hpp"
#include "barretenberg/vm2/simulation/events/event_emitter.hpp"
#include "barretenberg/vm2/tracegen/lib/interaction_def.hpp"
Expand All @@ -10,19 +9,10 @@ namespace bb::avm2::tracegen {

class AluTraceBuilder final {
public:
AluTraceBuilder();
void process(const simulation::EventEmitterInterface<simulation::AluEvent>::Container& events,
TraceContainer& trace);

static const InteractionDefinition interactions;

private:
static constexpr size_t NUM_TAGS = static_cast<size_t>(MemoryTag::MAX) + 1;
// Precomputed inverses for tag values.
std::array<FF, NUM_TAGS> tag_inverses;
std::vector<std::pair<Column, FF>> get_operation_specific_columns(const simulation::AluEvent& event) const;
FF get_tag_diff_inverse(const MemoryTag a_tag, const MemoryTag b_tag) const;
std::vector<std::pair<Column, FF>> get_tag_error_columns(const simulation::AluEvent& event) const;
};

} // namespace bb::avm2::tracegen
31 changes: 15 additions & 16 deletions barretenberg/cpp/src/barretenberg/vm2/tracegen/keccakf1600_trace.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -379,24 +379,23 @@ constexpr std::array<C, AVM_KECCAKF1600_STATE_SIZE> MEM_VAL_COLS = {
},
};

// Precomputed inverses from 0, 1 ... AVM_KECCAKF1600_STATE_SIZE.
std::array<FF, AVM_KECCAKF1600_STATE_SIZE + 1> generate_precomputed_inverses()
// Get inverse for a given index using static precomputed inverses.
const FF& get_precomputed_inverse(size_t index)
{
std::array<FF, AVM_KECCAKF1600_STATE_SIZE + 1> precomputed_inverses;
for (size_t i = 0; i < AVM_KECCAKF1600_STATE_SIZE + 1; i++) {
precomputed_inverses.at(i) = FF(i);
}
FF::batch_invert(precomputed_inverses);
return precomputed_inverses;
static const std::array<FF, AVM_KECCAKF1600_STATE_SIZE + 1> precomputed_inverses = []() {
std::array<FF, AVM_KECCAKF1600_STATE_SIZE + 1> inverses;
for (size_t i = 0; i < AVM_KECCAKF1600_STATE_SIZE + 1; i++) {
inverses.at(i) = FF(i);
}
FF::batch_invert(inverses);
return inverses;
}();

return precomputed_inverses.at(index);
}

} // namespace

KeccakF1600TraceBuilder::KeccakF1600TraceBuilder()
{
precomputed_inverses = generate_precomputed_inverses();
}

// Populate a memory slice read or write operation for the Keccak permutation.
void KeccakF1600TraceBuilder::process_single_slice(const simulation::KeccakF1600Event& event,
bool write,
Expand Down Expand Up @@ -450,9 +449,9 @@ void KeccakF1600TraceBuilder::process_single_slice(const simulation::KeccakF1600
{ C::keccak_memory_sel, 1 },
{ C::keccak_memory_clk, event.execution_clk },
{ C::keccak_memory_ctr, i + 1 },
{ C::keccak_memory_ctr_inv, precomputed_inverses.at(i + 1) },
{ C::keccak_memory_ctr_inv, get_precomputed_inverse(i + 1) },
{ C::keccak_memory_state_size_min_ctr_inv,
precomputed_inverses.at(AVM_KECCAKF1600_STATE_SIZE - i - 1) },
get_precomputed_inverse(AVM_KECCAKF1600_STATE_SIZE - i - 1) },
{ C::keccak_memory_start_read, (i == 0 && !write) ? 1 : 0 },
{ C::keccak_memory_start_write, (i == 0 && write) ? 1 : 0 },
{ C::keccak_memory_ctr_end, i == AVM_KECCAKF1600_STATE_SIZE - 1 ? 1 : 0 },
Expand Down Expand Up @@ -555,7 +554,7 @@ void KeccakF1600TraceBuilder::process_permutation(
{ C::keccakf1600_dst_addr, event.dst_addr },
{ C::keccakf1600_sel_no_error, error ? 0 : 1 },
{ C::keccakf1600_space_id, event.space_id },
{ C::keccakf1600_round_inv, precomputed_inverses.at(round_idx + 1) },
{ C::keccakf1600_round_inv, get_precomputed_inverse(round_idx + 1) },
} });

// When no out-of-range value occured but a tag value error, we
Expand Down
3 changes: 0 additions & 3 deletions barretenberg/cpp/src/barretenberg/vm2/tracegen/keccakf1600_trace.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,6 @@ namespace bb::avm2::tracegen {

class KeccakF1600TraceBuilder final {
public:
KeccakF1600TraceBuilder();
void process_permutation(const simulation::EventEmitterInterface<simulation::KeccakF1600Event>::Container& events,
TraceContainer& trace);
void process_memory_slices(const simulation::EventEmitterInterface<simulation::KeccakF1600Event>::Container& events,
Expand All @@ -19,8 +18,6 @@ class KeccakF1600TraceBuilder final {
static const InteractionDefinition interactions;

private:
// Precomputed inverses from 0, 1 ... AVM_KECCAKF1600_STATE_SIZE.
std::array<FF, AVM_KECCAKF1600_STATE_SIZE + 1> precomputed_inverses;
void process_single_slice(const simulation::KeccakF1600Event& event,
bool write,
uint32_t& row,
Expand Down
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