matmul.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_MATMUL_H
#define HELIB_MATMUL_H
 
#include <helib/EncryptedArray.h>
 
namespace helib {
 
class MatMulFullExec;
 
// Abstract base class for representing a linear transformation on a full
// std::vector.
class MatMulFull
{
public:
  virtual ~MatMulFull() {}
  virtual const EncryptedArray& getEA() const = 0;
  typedef MatMulFullExec ExecType;
};
 
// Concrete derived class that defines the matrix entries.
template <typename type>
class MatMulFull_derived : public MatMulFull
{
public:
  PA_INJECT(type)
 
  // Get (i, j) entry of matrix.
  // Should return true when the entry is a zero.
  virtual bool get(RX& out, long i, long j) const = 0;
};
 
//====================================
 
class BlockMatMulFullExec;
 
// Abstract base class for representing a block linear transformation on a full
// std::vector.
class BlockMatMulFull
{
public:
  virtual ~BlockMatMulFull() {}
  virtual const EncryptedArray& getEA() const = 0;
  typedef BlockMatMulFullExec ExecType;
};
 
// Concrete derived class that defines the matrix entries.
template <typename type>
class BlockMatMulFull_derived : public BlockMatMulFull
{
public:
  PA_INJECT(type)
 
  // Get (i, j) entry of matrix.
  // Each entry is a d x d matrix over the base ring.
  // Should return true when the entry is a zero.
  virtual bool get(mat_R& out, long i, long j) const = 0;
};
 
//====================================
 
class MatMul1DExec;
 
// Abstract base class for representing a 1D linear transformation.
class MatMul1D
{
public:
  virtual ~MatMul1D() {}
  virtual const EncryptedArray& getEA() const = 0;
  virtual long getDim() const = 0;
  typedef MatMul1DExec ExecType;
};
 
// An intermediate class that is mainly intended for internal use.
template <typename type>
class MatMul1D_partial : public MatMul1D
{
public:
  PA_INJECT(type)
 
  // Get the i'th diagonal, encoded as a single constant.
  // MatMul1D_derived (below) supplies a default implementation,
  // which can be overridden in special circumstances.
  virtual void processDiagonal(RX& poly,
                               long i,
                               const EncryptedArrayDerived<type>& ea) const = 0;
};
 
// Concrete derived class that defines the matrix entries.
template <typename type>
class MatMul1D_derived : public MatMul1D_partial<type>
{
public:
  PA_INJECT(type)
 
  // Should return true if their are multiple (different) transforms
  // among the various components.
  virtual bool multipleTransforms() const = 0;
 
  // Get coordinate (i, j) of the kth component.
  // Should return true when the entry is a zero.
  virtual bool get(RX& out, long i, long j, long k) const = 0;
 
  void processDiagonal(RX& poly,
                       long i,
                       const EncryptedArrayDerived<type>& ea) const override;
};
 
class MatMul1D_CKKS : public MatMul1D
{
public:
  // Get coordinate (i, j)
  virtual std::complex<double> get(long i, long j) const = 0;
 
  void processDiagonal(zzX& poly,
                       double& size,
                       double& factor,
                       long i,
                       const EncryptedArrayCx& ea) const;
};
 
//====================================
 
class BlockMatMul1DExec;
 
// Abstract base class for representing a block 1D linear transformation.
class BlockMatMul1D
{
public:
  virtual ~BlockMatMul1D() {}
  virtual const EncryptedArray& getEA() const = 0;
  virtual long getDim() const = 0;
  typedef BlockMatMul1DExec ExecType;
};
 
// An intermediate class that is mainly intended for internal use.
template <typename type>
class BlockMatMul1D_partial : public BlockMatMul1D
{
public:
  PA_INJECT(type)
 
  // Get the i'th diagonal, encoded as a std::vector of d constants,
  // where d is the order of p.
  // BlockMatMul1D_derived (below) supplies a default implementation,
  // which can be overridden in special circumstances.
  virtual bool processDiagonal(std::vector<RX>& poly,
                               long i,
                               const EncryptedArrayDerived<type>& ea) const = 0;
};
 
// Concrete derived class that defines the matrix entries.
template <typename type>
class BlockMatMul1D_derived : public BlockMatMul1D_partial<type>
{
public:
  PA_INJECT(type)
 
  // Should return true if their are multiple (different) transforms
  // among the various components.
  virtual bool multipleTransforms() const = 0;
 
  // Get coordinate (i, j) of the kth component.
  // Each entry is a d x d matrix over the base ring.
  // Should return true when the entry is a zero.
  virtual bool get(mat_R& out, long i, long j, long k) const = 0;
 
  bool processDiagonal(std::vector<RX>& poly,
                       long i,
                       const EncryptedArrayDerived<type>& ea) const override;
};
 
//====================================
 
struct ConstMultiplier;
// Defined in matmul.cpp.
// Holds a constant by which a ciphertext can be multiplied.
// Internally, it is represented as either zzX or a DoubleCRT.
// The former occupies less space, but the latter makes for
// much faster multiplication.
 
struct ConstMultiplierCache
{
  std::vector<std::shared_ptr<ConstMultiplier>> multiplier;
 
  // Upgrade zzX constants to DoubleCRT constants.
  void upgrade(const Context& context);
};
 
//====================================
 
// Abstract base case for multiplying an encrypted std::vector by a plaintext
// matrix.
class MatMulExecBase
{
public:
  virtual ~MatMulExecBase() {}
 
  virtual const EncryptedArray& getEA() const = 0;
 
  // Upgrade zzX constants to DoubleCRT constants.
  virtual void upgrade() = 0;
 
  // If ctxt encrypts a row std::vector v, then this replaces ctxt
  // by an encryption of the row std::vector v*mat, where mat is
  // a matrix provided to the constructor of one of the
  // concrete subclasses MatMul1DExec, BlockMatMul1DExec,
  // MatMulFullExec, BlockMatMulFullExec, defined below.
  virtual void mul(Ctxt& ctxt) const = 0;
};
 
//====================================
 
// Class used to multiply an encrypted row std::vector by a 1D linear
// transformation.
class MatMul1DExec : public MatMulExecBase
{
public:
  const EncryptedArray& ea;
 
  long dim;
  long D;
  bool native;
  bool minimal;
  long g;
 
  ConstMultiplierCache cache;
  ConstMultiplierCache cache1; // only for non-native dimension
 
  // The constructor encodes all the constants for a given
  // matrix in zzX format.
  // The mat argument defines the entries of the matrix.
  // Use the upgrade method (below) to convert to DoubleCRT format.
  // If the minimal flag is set to true, a strategy that relies
  // on a minimal number of key switching matrices will be used;
  // this is intended for use in conjunction with the
  // addMinimal{1D,Frb}Matrices routines declared in helib.h.
  // If the minimal flag is false, it is best to use the
  // addSome{1D,Frb}Matrices routines declared in helib.h.
  explicit MatMul1DExec(const MatMul1D& mat, bool minimal = false);
 
  // Replaces an encryption of row std::vector v by encryption of v*mat
  void mul(Ctxt& ctxt) const override;
 
  // Upgrades encoded constants from zzX to DoubleCRT.
  void upgrade() override
  {
    cache.upgrade(ea.getContext());
    cache1.upgrade(ea.getContext());
  }
 
  const EncryptedArray& getEA() const override { return ea; }
};
 
//====================================
 
// Class used to multiply an encrypted row std::vector by a block 1D linear
// transformation.
class BlockMatMul1DExec : public MatMulExecBase
{
public:
  const EncryptedArray& ea;
 
  long dim;
  long D;
  long d;
  bool native;
  long strategy;
 
  ConstMultiplierCache cache;
  ConstMultiplierCache cache1; // only for non-native dimension
 
  // The constructor encodes all the constants for a given
  // matrix in zzX format.
  // The mat argument defines the entries of the matrix.
  // Use the upgrade method (below) to convert to DoubleCRT format.
  // If the minimal flag is set to true, a strategy that relies
  // on a minimal number of key switching matrices will be used;
  // this is intended for use in conjunction with the
  // addMinimal{1D,Frb}Matrices routines declared in helib.h.
  // If the minimal flag is false, it is best to use the
  // addSome{1D,Frb}Matrices routines declared in helib.h.
  explicit BlockMatMul1DExec(const BlockMatMul1D& mat, bool minimal = false);
 
  // Replaces an encryption of row std::vector v by encryption of v*mat
  void mul(Ctxt& ctxt) const override;
 
  // Upgrades encoded constants from zzX to DoubleCRT.
  void upgrade() override
  {
    cache.upgrade(ea.getContext());
    cache1.upgrade(ea.getContext());
  }
 
  const EncryptedArray& getEA() const override { return ea; }
};
 
//====================================
 
// Class used to multiply an encrypted row std::vector by a full linear
// transformation.
class MatMulFullExec : public MatMulExecBase
{
public:
  const EncryptedArray& ea;
  bool minimal;
  std::vector<long> dims;
  std::vector<MatMul1DExec> transforms;
 
  // The constructor encodes all the constants for a given
  // matrix in zzX format.
  // The mat argument defines the entries of the matrix.
  // Use the upgrade method (below) to convert to DoubleCRT format.
  // If the minimal flag is set to true, a strategy that relies
  // on a minimal number of key switching matrices will be used;
  // this is intended for use in conjunction with the
  // addMinimal{1D,Frb}Matrices routines declared in helib.h.
  // If the minimal flag is false, it is best to use the
  // addSome{1D,Frb}Matrices routines declared in helib.h.
  explicit MatMulFullExec(const MatMulFull& mat, bool minimal = false);
 
  // Replaces an encryption of row std::vector v by encryption of v*mat
  void mul(Ctxt& ctxt) const override;
 
  // Upgrades encoded constants from zzX to DoubleCRT.
  void upgrade() override
  {
    for (auto& t : transforms)
      t.upgrade();
  }
 
  const EncryptedArray& getEA() const override { return ea; }
 
  // This really should be private.
  long rec_mul(Ctxt& acc, const Ctxt& ctxt, long dim, long idx) const;
};
 
//====================================
 
// Class used to multiply an encrypted row std::vector by a full block linear
// transformation.
class BlockMatMulFullExec : public MatMulExecBase
{
public:
  const EncryptedArray& ea;
  bool minimal;
  std::vector<long> dims;
  std::vector<BlockMatMul1DExec> transforms;
 
  // The constructor encodes all the constants for a given
  // matrix in zzX format.
  // The mat argument defines the entries of the matrix.
  // Use the upgrade method (below) to convert to DoubleCRT format.
  // If the minimal flag is set to true, a strategy that relies
  // on a minimal number of key switching matrices will be used;
  // this is intended for use in conjunction with the
  // addMinimal{1D,Frb}Matrices routines declared in helib.h.
  // If the minimal flag is false, it is best to use the
  // addSome{1D,Frb}Matrices routines declared in helib.h.
  explicit BlockMatMulFullExec(const BlockMatMulFull& mat,
                               bool minimal = false);
 
  // Replaces an encryption of row std::vector v by encryption of v*mat
  void mul(Ctxt& ctxt) const override;
 
  // Upgrades encoded constants from zzX to DoubleCRT.
  void upgrade() override
  {
    for (auto& t : transforms)
      t.upgrade();
  }
 
  const EncryptedArray& getEA() const override { return ea; }
 
  // This really should be private.
  long rec_mul(Ctxt& acc, const Ctxt& ctxt, long dim, long idx) const;
};
 
//===================================
 
// ctxt = \sum_{i=0}^{d-1} \sigma^i(ctxt),
//   where d = order of p mod m, and \sigma is the Frobenius map
 
void traceMap(Ctxt& ctxt);
 
//====================================
 
// These routines apply linear transformation to plaintext arrays.
// Mainly for testing purposes.
void mul(PlaintextArray& pa, const MatMul1D& mat);
void mul(PlaintextArray& pa, const BlockMatMul1D& mat);
void mul(PlaintextArray& pa, const MatMulFull& mat);
void mul(PlaintextArray& pa, const BlockMatMulFull& mat);
 
// These are used mainly for performance evaluation.
 
extern int fhe_test_force_bsgs;
// Controls whether or not we use BSGS multiplication.
// 1 to force on, -1 to force off, 0 for default behaviour.
 
extern int fhe_test_force_hoist;
// Controls whether ot not we use hoisting.
// -1 to force off, 0 for default behaviour.
 
} // namespace helib
 
#endif // ifndef HELIB_MATMUL_H