Diag

[IanQS]

Emulate Numpy diag

Extract a diagonal or construct a diagonal array.

Include testing. Progress so far listed below

[IanQS]

pTensor.h

  /**
   * Extract the diagonal from a matrix
   * @param matrix
   *    Matrix of shape (m, n) (not necessarily a square matrix)
   * @param asRowVector
   *    Whether to return as a rowVector or as a col Vector
   * @return
   *    The diagonal elements as a vector
   */
  static pTensor getDiagonal(const pTensor& matrix, bool asRowVector);

  /**
   * Make a matrix where the diagonals are elements of the vector
   * @param vector
   *    Vector of (1, numElems)
   * @return
   *    Return a matrix where the diagonals are populated by the vector's elements
   */
  static pTensor makeDiagonal(pTensor vector);

[IanQS]

pTensor pTensor::getDiagonal(const pTensor &matrix, bool asRowVector) {
    throw NotImplementedException();
    assert (matrix.isMatrix());
    if (asRowVector) {
        // We mask out all but the row of interest then accumulate into a row vector
        messageVector _container(matrix.m_cols, 0);
        cipherVector vectorContainer = (*m_cc)->Encrypt(
            m_public_key,
            (*m_cc)->MakeCKKSPackedPlaintext(_container));

        int diagIndex = 0;
        for (auto &v: matrix.m_ciphertexts) {
            messageVector mask(matrix.m_cols, 0);
            mask[diagIndex] = 1;
            auto ptMask = (*m_cc)->MakeCKKSPackedPlaintext(mask);
            auto maskedVal = (*m_cc)->EvalMult(v, ptMask);
            vectorContainer = (*m_cc)->EvalAdd(vectorContainer, maskedVal);
        }
        cipherTensor matrixContainer = {vectorContainer};
        pTensor newTensor(1, matrix.m_cols, matrixContainer);
        newTensor.m_isEncrypted = true;
        return newTensor;
    }
    return pTensor();
}
pTensor pTensor::makeDiagonal(pTensor vector) {
    throw NotImplementedException();
    assert (vector.isVector());
    pTensor identity = pTensor::identity(vector.m_rows);
    auto eIdentity = identity.encrypt();

    return eIdentity * vector;  // Hadamard
}