public double getDouble(long... coordinates) {
if (inv == null) {
DenseMatrix A = new MTJDenseDoubleMatrix2D(getSource()).getWrappedObject();
DenseMatrix I = Matrices.identity((int) getSource().getColumnCount());
DenseMatrix AI = I.copy();
inv = new MTJDenseDoubleMatrix2D((DenseMatrix) A.solve(I, AI));
}
return inv.getAsDouble(coordinates);
}