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Consolidate permutation mapping computation into one method #330

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Apr 7, 2023
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Consolidate permutation mapping computation into one method #330

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de56786
consolidate computation of permutation mapping into one method usable…
ledwards2225 Apr 6, 2023
b62237f
remove unneeded include
ledwards2225 Apr 6, 2023
3b720db
comment corrections
ledwards2225 Apr 7, 2023
3dc272b
reinstate pub input tag cerr
ledwards2225 Apr 7, 2023
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170 changes: 69 additions & 101 deletions cpp/src/barretenberg/proof_system/composer/permutation_helper.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -47,6 +47,13 @@ struct permutation_subgroup_element {
bool is_public_input = false;
bool is_tag = false;
};

template <size_t program_width> struct PermutationMapping {
using Mapping = std::array<std::vector<permutation_subgroup_element>, program_width>;
Mapping sigmas;
Mapping ids;
};

using CyclicPermutation = std::vector<cycle_node>;

namespace {
Expand Down Expand Up @@ -120,63 +127,95 @@ std::vector<CyclicPermutation> compute_wire_copy_cycles(const CircuitConstructor
}

/**
* @brief Compute the permutation mapping for the basic no-tags case
* @brief Compute the traditional or generalized permutation mapping
*
* @details This function computes the permutation information in a commonf format that can then be used to generate
* either Plonk-style FFT-ready sigma polynomials or Honk-style indexed vectors
* @details Computes the mappings from which the sigma polynomials (and conditionally, the id polynomials)
* can be computed. The output is proving system agnostic. with
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Extra with

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done, thanks

*
* @tparam program_width The number of wires
* @tparam generalized (bool) Triggers use of gen perm tags and computation of id mappings when true
* @tparam CircuitConstructor The class that holds basic circuitl ogic
* @param circuit_constructor Circuit-containing object
* @param key Pointer to the proving key
* @return PermutationMapping sigma mapping (and id mapping if generalized == true)
*/
template <size_t program_width, typename CircuitConstructor>
std::array<std::vector<permutation_subgroup_element>, program_width> compute_basic_proof_system_sigma_permutations(
const CircuitConstructor& circuit_constructor, plonk::proving_key* key)
template <size_t program_width, bool generalized, typename CircuitConstructor>
PermutationMapping<program_width> compute_permutation_mapping(const CircuitConstructor& circuit_constructor,
plonk::proving_key* key)
{
// Compute wire copy cycles (cycles of permutations)
auto wire_copy_cycles = compute_wire_copy_cycles<program_width>(circuit_constructor);

PermutationMapping<program_width> mapping;

// Initialize the table of permutations so that every element points to itself
std::array<std::vector<permutation_subgroup_element>, program_width> sigma_mappings;
for (size_t i = 0; i < program_width; ++i) {
sigma_mappings[i].reserve(key->circuit_size);
mapping.sigmas[i].reserve(key->circuit_size);
if (generalized) {
mapping.ids[i].reserve(key->circuit_size);
}

for (size_t j = 0; j < key->circuit_size; ++j) {
sigma_mappings[i].emplace_back(permutation_subgroup_element{
mapping.sigmas[i].emplace_back(permutation_subgroup_element{
.row_index = (uint32_t)j, .column_index = (uint8_t)i, .is_public_input = false, .is_tag = false });
if (generalized) {
mapping.ids[i].emplace_back(permutation_subgroup_element{
.row_index = (uint32_t)j, .column_index = (uint8_t)i, .is_public_input = false, .is_tag = false });
}
}
}

// Represents the index of a variable in circuit_constructor.variables (needed only for generalized)
std::span<const uint32_t> real_variable_tags = circuit_constructor.real_variable_tags;

// Go through each cycle
for (size_t i = 0; i < wire_copy_cycles.size(); ++i) {
for (size_t j = 0; j < wire_copy_cycles[i].size(); ++j) {
// Get the indices of the current node and next node int he cycle
cycle_node current_cycle_node = wire_copy_cycles[i][j];
size_t cycle_index = 0;
for (auto& copy_cycle : wire_copy_cycles) {
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for (size_t node_idx = 0; node_idx < copy_cycle.size(); ++node_idx) {
// Get the indices of the current node and next node in the cycle
cycle_node current_cycle_node = copy_cycle[node_idx];
// If current node is the last one in the cycle, then the next one is the first one
size_t next_cycle_node_index = j == wire_copy_cycles[i].size() - 1 ? 0 : j + 1;
cycle_node next_cycle_node = wire_copy_cycles[i][next_cycle_node_index];
size_t next_cycle_node_index = (node_idx == copy_cycle.size() - 1 ? 0 : node_idx + 1);
cycle_node next_cycle_node = copy_cycle[next_cycle_node_index];
const auto current_row = current_cycle_node.gate_index;
const auto next_row = next_cycle_node.gate_index;

const uint32_t current_column = current_cycle_node.wire_index;
const uint32_t next_column = next_cycle_node.wire_index;
const auto current_column = current_cycle_node.wire_index;
const auto next_column = static_cast<uint8_t>(next_cycle_node.wire_index);
// Point current node to the next node
sigma_mappings[current_column][current_row] = {
.row_index = next_row, .column_index = (uint8_t)next_column, .is_public_input = false, .is_tag = false
mapping.sigmas[current_column][current_row] = {
.row_index = next_row, .column_index = next_column, .is_public_input = false, .is_tag = false
};

if (generalized) {
bool first_node = (node_idx == 0);
bool last_node = (next_cycle_node_index == 0);

if (first_node) {
mapping.ids[current_column][current_row].is_tag = true;
mapping.ids[current_column][current_row].row_index = (real_variable_tags[cycle_index]);
}
if (last_node) {
mapping.sigmas[current_column][current_row].is_tag = true;

// TODO: yikes, std::maps are expensive. Can we find a way to get rid of this?
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Can you attribute this quote to Zac?

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I checked at some point that he wrote it.

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Thought about doing that. Will do

mapping.sigmas[current_column][current_row].row_index =
circuit_constructor.tau.at(real_variable_tags[cycle_index]);
}
}
}
cycle_index++;
}

// Add informationa about public inputs to the computation
const uint32_t num_public_inputs = static_cast<uint32_t>(circuit_constructor.public_inputs.size());

for (size_t i = 0; i < num_public_inputs; ++i) {
sigma_mappings[0][i].row_index = static_cast<uint32_t>(i);
sigma_mappings[0][i].column_index = 0;
sigma_mappings[0][i].is_public_input = true;
mapping.sigmas[0][i].row_index = static_cast<uint32_t>(i);
mapping.sigmas[0][i].column_index = 0;
mapping.sigmas[0][i].is_public_input = true;
}
return sigma_mappings;
return mapping;
}

/**
Expand Down Expand Up @@ -403,9 +442,9 @@ template <size_t program_width, typename CircuitConstructor>
void compute_standard_honk_sigma_permutations(CircuitConstructor& circuit_constructor, plonk::proving_key* key)
{
// Compute the permutation table specifying which element becomes which
auto sigma_mappings = compute_basic_proof_system_sigma_permutations<program_width>(circuit_constructor, key);
auto mapping = compute_permutation_mapping<program_width, false>(circuit_constructor, key);
// Compute Honk-style sigma polynomial fromt the permutation table
compute_honk_style_sigma_lagrange_polynomials_from_mapping(sigma_mappings, key);
compute_honk_style_sigma_lagrange_polynomials_from_mapping(mapping.sigmas, key);
}

/**
Expand All @@ -420,9 +459,9 @@ template <size_t program_width, typename CircuitConstructor>
void compute_standard_plonk_sigma_permutations(CircuitConstructor& circuit_constructor, plonk::proving_key* key)
{
// Compute the permutation table specifying which element becomes which
auto sigma_mappings = compute_basic_proof_system_sigma_permutations<program_width>(circuit_constructor, key);
auto mapping = compute_permutation_mapping<program_width, false>(circuit_constructor, key);
// Compute Plonk-style sigma polynomials from the mapping
compute_plonk_permutation_lagrange_polynomials_from_mapping("sigma", sigma_mappings, key);
compute_plonk_permutation_lagrange_polynomials_from_mapping("sigma", mapping.sigmas, key);
// Compute their monomial and coset versions
compute_monomial_and_coset_fft_polynomials_from_lagrange<program_width>("sigma", key);
}
Expand Down Expand Up @@ -456,82 +495,11 @@ template <size_t program_width, typename CircuitConstructor>
void compute_plonk_generalized_sigma_permutations(const CircuitConstructor& circuit_constructor,
plonk::proving_key* key)
{
// Compute wire copy cycles for public and private variables
auto wire_copy_cycles = compute_wire_copy_cycles<program_width>(circuit_constructor);
std::array<std::vector<permutation_subgroup_element>, program_width> sigma_mappings;
std::array<std::vector<permutation_subgroup_element>, program_width> id_mappings;

// Instantiate the sigma and id mappings by reserving enough space and pushing 'default' permutation subgroup
// elements that point to themselves.
for (size_t i = 0; i < program_width; ++i) {
sigma_mappings[i].reserve(key->circuit_size);
id_mappings[i].reserve(key->circuit_size);
}
for (size_t i = 0; i < program_width; ++i) {
for (size_t j = 0; j < key->circuit_size; ++j) {
sigma_mappings[i].emplace_back(permutation_subgroup_element{
.row_index = (uint32_t)j, .column_index = (uint8_t)i, .is_public_input = false, .is_tag = false });

id_mappings[i].emplace_back(permutation_subgroup_element{
.row_index = (uint32_t)j, .column_index = (uint8_t)i, .is_public_input = false, .is_tag = false });
}
}

// // Represents the index of a variable in circuit_constructor.variables
std::span<const uint32_t> real_variable_tags = circuit_constructor.real_variable_tags;
// const std::map<uint32_t, uint32_t>& tau = circuit_constructor.tau;

// Go through all wire cycles and update sigma and id mappings to point to the next element
// within each cycle as well as set the appropriate tags
for (size_t i = 0; i < wire_copy_cycles.size(); ++i) {
for (size_t j = 0; j < wire_copy_cycles[i].size(); ++j) {
cycle_node current_cycle_node = wire_copy_cycles[i][j];
size_t next_cycle_node_index = j == wire_copy_cycles[i].size() - 1 ? 0 : j + 1;
cycle_node next_cycle_node = wire_copy_cycles[i][next_cycle_node_index];
const auto current_row = current_cycle_node.gate_index;
const auto next_row = next_cycle_node.gate_index;

const uint32_t current_column = current_cycle_node.wire_index;
const uint32_t next_column = next_cycle_node.wire_index;

sigma_mappings[current_column][current_row] = {
.row_index = next_row, .column_index = (uint8_t)next_column, .is_public_input = false, .is_tag = false
};

bool first_node, last_node;

first_node = j == 0;
last_node = next_cycle_node_index == 0;
if (first_node) {
id_mappings[current_column][current_row].is_tag = true;
id_mappings[current_column][current_row].row_index = (real_variable_tags[i]);
}
if (last_node) {
sigma_mappings[current_column][current_row].is_tag = true;

// TODO: yikes, std::maps are expensive. Can we find a way to get rid of this?
sigma_mappings[current_column][current_row].row_index =
circuit_constructor.tau.at(real_variable_tags[i]);
}
}
}

const uint32_t num_public_inputs = static_cast<uint32_t>(circuit_constructor.public_inputs.size());

// This corresponds in the paper to modifying sigma to sigma' with the zeta_i values; this enforces public input
// consistency
for (size_t i = 0; i < num_public_inputs; ++i) {
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Where did this logic go?

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This takes place in the final lines of compute_permutation_mapping

sigma_mappings[0][i].row_index = static_cast<uint32_t>(i);
sigma_mappings[0][i].column_index = 0;
sigma_mappings[0][i].is_public_input = true;
if (sigma_mappings[0][i].is_tag) {
std::cerr << "MAPPING IS BOTH A TAG AND A PUBLIC INPUT" << std::endl;
}
}
auto mapping = compute_permutation_mapping<program_width, true>(circuit_constructor, key);

// Compute Plonk-style sigma and ID polynomials from the corresponding mappings
compute_plonk_permutation_lagrange_polynomials_from_mapping("sigma", sigma_mappings, key);
compute_plonk_permutation_lagrange_polynomials_from_mapping("id", id_mappings, key);
compute_plonk_permutation_lagrange_polynomials_from_mapping("sigma", mapping.sigmas, key);
compute_plonk_permutation_lagrange_polynomials_from_mapping("id", mapping.ids, key);
// Compute the monomial and coset-ffts for sigmas and IDs
compute_monomial_and_coset_fft_polynomials_from_lagrange<program_width>("sigma", key);
compute_monomial_and_coset_fft_polynomials_from_lagrange<program_width>("id", key);
Expand Down