code: public static CholeskyDecomposition_F64<DMatrixRMaj> chol(int matrixSize , boolean lower )
      {
          if( matrixSize < EjmlParameters.SWITCH_BLOCK64_CHOLESKY ) {
              return new CholeskyDecompositionInner_DDRM(lower);
          } else if( EjmlParameters.MEMORY == EjmlParameters.MemoryUsage.FASTER ){
              return new CholeskyDecomposition_DDRB_to_DDRM(lower);
          } else {
              return new CholeskyDecompositionBlock_DDRM(EjmlParameters.BLOCK_WIDTH_CHOL);
          }
      }
docs: <p>
  Returns a {@link CholeskyDecomposition_F64} that has been optimized for the specified matrix size.
  </p>
  
  @param matrixSize Number of rows and columns that the returned decomposition is optimized for.
  @param lower should a lower or upper triangular matrix be used. If not sure set to true.
  @return A new CholeskyDecomposition.