fixed_base_params.hpp

Go to the documentation of this file.

// === AUDIT STATUS ===
// internal:    { status: not started, auditors: [], date: YYYY-MM-DD }
// external_1:  { status: not started, auditors: [], date: YYYY-MM-DD }
// external_2:  { status: not started, auditors: [], date: YYYY-MM-DD }
// =====================
 
#pragma once
 
#include <array>
#include <barretenberg/common/assert.hpp>
#include <barretenberg/ecc/curves/bn254/fr.hpp>
#include <barretenberg/numeric/general/general.hpp>
#include <cstddef>
#include <cstdint>
 
namespace bb::plookup {
struct FixedBaseParams {
    static constexpr size_t BITS_PER_TABLE = 9;
    static constexpr size_t BITS_ON_CURVE = 254;
 
    static constexpr size_t BITS_PER_LO_SCALAR = 128;
    static constexpr size_t BITS_PER_HI_SCALAR = BITS_ON_CURVE - BITS_PER_LO_SCALAR;
    // Max table size (Note: the last lookup table might be smaller if BITS_PER_TABLE does not neatly divide
    // BITS_PER_LO_SCALAR)
    static constexpr size_t MAX_TABLE_SIZE = (1UL) << BITS_PER_TABLE;
    // We create four Multitables, two for each supported base point (one for the LO_SCALAR, one for the HI_SCALAR)
    static constexpr size_t NUM_FIXED_BASE_MULTI_TABLES = 4;
    static constexpr size_t NUM_TABLES_PER_LO_MULTITABLE = numeric::ceil_div(BITS_PER_LO_SCALAR, BITS_PER_TABLE);
    static constexpr size_t NUM_TABLES_PER_HI_MULTITABLE = numeric::ceil_div(BITS_PER_HI_SCALAR, BITS_PER_TABLE);
    static constexpr size_t MAX_NUM_TABLES_IN_MULTITABLE =
        std::max(NUM_TABLES_PER_LO_MULTITABLE, NUM_TABLES_PER_HI_MULTITABLE);
 
    // Step sizes for BasicTable columns in fixed-base scalar multiplication
    // Column 1 contains the index, so step size varies with table size
    // Columns 2 and 3 (x, y coordinates) do not utilize the typical accumulator pattern --> step size is 0
    static inline const bb::fr COLUMN_2_STEP_SIZE = bb::fr(0);
    static inline const bb::fr COLUMN_3_STEP_SIZE = bb::fr(0);
 
    template <size_t multitable_index> static constexpr size_t get_num_bits_of_multi_table()
    {
        static_assert(multitable_index < NUM_FIXED_BASE_MULTI_TABLES);
        // Even indices (0, 2) are LO_SCALAR tables, odd indices (1, 3) are HI_SCALAR tables
        return (multitable_index % 2 == 0) ? BITS_PER_LO_SCALAR : BITS_PER_HI_SCALAR;
    }
};
} // namespace bb::plookup