{
super.InitModel();
// create data structure
diff_matrix_like = new SkewSymmetricSparseMatrix(MaxItemID + 1);
freq_matrix_like = new SymetricSparseMatrix_i(MaxItemID + 1);
diff_matrix_dislike = new SkewSymmetricSparseMatrix(MaxItemID + 1);
freq_matrix_dislike = new SymetricSparseMatrix_i(MaxItemID + 1);
user_average = new double[MaxUserID + 1];
}