CModulus.h

/* Copyright (C) 2012-2020 IBM Corp.
 * This program is Licensed under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 *   http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License. See accompanying LICENSE file.
 */
#ifndef HELIB_CMODULUS_H
#define HELIB_CMODULUS_H
 
#include <helib/NumbTh.h>
#include <helib/PAlgebra.h>
#include <helib/bluestein.h>
#include <helib/clonedPtr.h>
 
namespace helib {
 
class Cmodulus
{
  long q;
  NTL::mulmod_t qinv;
 
  NTL::zz_pContext context;
 
  const PAlgebra* zMStar;
 
  long m_inv;
 
  long root;
  long rInv;
 
  // tables for forward FFT
  copied_ptr<NTL::zz_pX> powers;
  NTL::Vec<NTL::mulmod_precon_t> powers_aux;
  copied_ptr<NTL::fftRep> Rb;
 
  // tables for backward FFT
  copied_ptr<NTL::zz_pX> ipowers;
  NTL::Vec<NTL::mulmod_precon_t> ipowers_aux;
  copied_ptr<NTL::fftRep> iRb;
 
  // PhimX modulo q, for faster division w/ remainder
  copied_ptr<zz_pXModulus1> phimx;
 
  // Allocate memory and compute roots
  void privateInit(const PAlgebra&, long rt);
 
public:
#ifdef HELIB_OPENCL
  SmartPtr<AltFFTPrimeInfo> altFFTInfo;
  // We need to allow copying...the underlying object
  // is immutable
#endif
 
  // Destructor and constructors
 
  Cmodulus() {}
 
  Cmodulus(const Cmodulus& other) { *this = other; }
 
  Cmodulus(const PAlgebra& zms, long qq, long rt);
 
  Cmodulus& operator=(const Cmodulus& other);
 
  // utility methods
 
  const PAlgebra& getZMStar() const { return *zMStar; }
  unsigned long getM() const { return zMStar->getM(); }
  unsigned long getPhiM() const { return zMStar->getPhiM(); }
  long getQ() const { return q; }
  NTL::mulmod_t getQInv() const { return qinv; }
  long getRoot() const { return root; }
  const zz_pXModulus1& getPhimX() const { return *phimx; }
 
  void restoreModulus() const { context.restore(); }
 
  // FFT routines
 
  // sets zp context internally
  // y = FFT(x)
  void FFT(NTL::vec_long& y, const NTL::ZZX& x) const;
  // y = FFT(x)
  void FFT(NTL::vec_long& y, const zzX& x) const;
 
  // auxiliary routine used by above two routines
  void FFT_aux(NTL::vec_long& y, NTL::zz_pX& tmp) const;
 
  // expects zp context to be set externally
  // x = FFT^{-1}(y)
  void iFFT(NTL::zz_pX& x, const NTL::vec_long& y) const;
 
  // returns thread-local scratch space
  // DIRT: this zz_pX is used for several zz_p moduli,
  // which is not officially sanctioned by NTL, but should be OK.
  static NTL::zz_pX& getScratch_zz_pX();
 
  static NTL::Vec<long>& getScratch_vec_long();
 
  // returns thread-local scratch space
  // DIRT: this use a couple of internal, undocumented
  // NTL interfaces
  static NTL::fftRep& getScratch_fftRep(long k);
};
 
} // namespace helib
 
#endif // ifndef HELIB_CMODULUS_H