Program Listing for File ckksrns-utils.h

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#ifndef _CKKSRNS_UTILS_H_
#define _CKKSRNS_UTILS_H_

#include "utils/exception.h"

#include <complex>
#include <memory>
#include <stdint.h>
#include <vector>

/*
 * Subroutines used by the linear transformation homomorphic capability
 */

namespace lbcrypto {

template <typename VecDType>
struct longDiv {
    std::vector<VecDType> q;
    std::vector<VecDType> r;
    longDiv() = default;
    longDiv(const std::vector<VecDType>& q0, const std::vector<VecDType>& r0) : q(q0), r(r0) {}
};

inline bool IsNotEqualOne(double v, double delta = 0x1p-44) {
    return std::abs(v - 1.0) > delta;
}
inline bool IsNotEqualZero(double v, double delta = 0x1p-44) {
    return std::abs(v) > delta;
}
inline bool IsNotEqualNegOne(double v, double delta = 0x1p-44) {
    return std::abs(v + 1.0) > delta;
}
inline bool IsNotEqualOne(std::complex<double> val, double delta = 0x1p-44) {
    return IsNotEqualOne(val.real(), delta) || IsNotEqualZero(val.imag(), delta);
}
inline bool IsNotEqualZero(std::complex<double> val, double delta = 0x1p-44) {
    return IsNotEqualZero(val.real(), delta) || IsNotEqualZero(val.imag(), delta);
}

inline double ToReal(double val) {
    return val;
}
inline double ToReal(int64_t val) {
    return static_cast<double>(val);
}
inline double ToReal(std::complex<double> val) {
    return val.real();
}

template <typename VecDType>
uint32_t Degree(const std::vector<VecDType>& coefficients, double delta = 0.0) {
    uint32_t i = coefficients.size();
    if (i == 0)
        OPENFHE_THROW("Coefficients vector can not be empty");
    while (i > 0) {
        if (IsNotEqualZero(coefficients[--i], delta))
            break;
    }
    return i;
}

template <typename VecDType>
std::shared_ptr<longDiv<VecDType>> LongDivisionPoly(const std::vector<VecDType>& f, const std::vector<VecDType>& g);

template <typename VecDType>
std::shared_ptr<longDiv<VecDType>> LongDivisionChebyshev(const std::vector<VecDType>& f,
                                                         const std::vector<VecDType>& g);

std::vector<uint32_t> ComputeDegreesPS(uint32_t n);

uint32_t GetDepthByDegree(size_t degree);

template <typename VecDType>
uint32_t GetMultiplicativeDepthByCoeffVector(const std::vector<VecDType>& vec, bool isNormalized = false) {
    if (vec.size() == 0)
        OPENFHE_THROW("Cannot perform operation on empty vector. vec.size() == 0");
    return GetDepthByDegree(vec.size() - 1) - isNormalized;
}

std::vector<std::complex<double>> ExtractShiftedDiagonal(const std::vector<std::vector<std::complex<double>>>& A,
                                                         int i);

template <typename VecDType>
std::vector<VecDType> Rotate(const std::vector<VecDType>& a, int32_t index);

template <typename VecDType>
std::vector<VecDType> RotateTwoHalves(const std::vector<VecDType>& a, int32_t index);

template <typename VecDType = std::vector<std::complex<double>>>
std::vector<VecDType> Fill(const std::vector<VecDType>& a, uint32_t slots);

template <typename VecDType = std::vector<std::complex<double>>>
std::vector<VecDType> Fill(std::initializer_list<VecDType> a, uint32_t slots);

/*
template <typename VecDType = std::complex<double>>
std::vector<VecDType> Fill(const std::vector<VecDType>& a, uint32_t slots);
*/

std::vector<std::vector<std::complex<double>>> CoeffEncodingOneLevel(const std::vector<std::complex<double>>& pows,
                                                                     const std::vector<uint32_t>& rotGroup,
                                                                     bool flag_i);

std::vector<std::vector<std::complex<double>>> CoeffDecodingOneLevel(const std::vector<std::complex<double>>& pows,
                                                                     const std::vector<uint32_t>& rotGroup,
                                                                     bool flag_i);

std::vector<std::vector<std::vector<std::complex<double>>>> CoeffEncodingCollapse(
    const std::vector<std::complex<double>>& pows, const std::vector<uint32_t>& rotGroup, uint32_t levelBudget,
    bool flag_i);

std::vector<std::vector<std::vector<std::complex<double>>>> CoeffDecodingCollapse(
    const std::vector<std::complex<double>>& pows, const std::vector<uint32_t>& rotGroup, uint32_t levelBudget,
    bool flag_i);

uint32_t ReduceRotation(int32_t index, uint32_t slots);

struct ckks_boot_params {
    uint32_t lvlb;             // level budget
    uint32_t layersCollapse;   // layers to collapse in one level
    uint32_t remCollapse;      // remaining layers to collapse
    uint32_t numRotations;     // umber of rotations in one level
    uint32_t b;                // baby step in the baby-step giant-step strategy
    uint32_t g;                // giant step in the baby-step giant-step strategy
    uint32_t numRotationsRem;  // number of rotations in the remaining level
    uint32_t bRem;             // baby step in the baby-step giant-step strategy for the remaining level
    uint32_t gRem;             // giant step in the baby-step giant-step strategy for the remaining level
};
struct ckks_boot_params GetCollapsedFFTParams(uint32_t slots, uint32_t levelBudget = 4, uint32_t dim1 = 0);

uint32_t getRatioBSGSLT(uint32_t slots);

std::vector<int32_t> FindLTRotationIndicesSwitch(uint32_t dim1, uint32_t m, uint32_t blockDimension);

std::vector<int32_t> FindLTRotationIndicesSwitchArgmin(uint32_t m, uint32_t blockDimension, uint32_t cols);

}  // namespace lbcrypto

#endif