Array lderror = ref.lowerDiagonal().clone();
lderror.subAssign(op1.lowerDiagonal());
Array derror = ref.diagonal().clone();
derror.subAssign(op1.diagonal());
Array uderror = ref.upperDiagonal().clone();
uderror.subAssign(op1.upperDiagonal());
for (i=2; i<grid.size()-2; i++) {
QL.info("lderror(" + i + ") = "+ Math.abs(lderror.get(i)) + " tolerance " + tolerance + " \n");
QL.info("derror(" + i + ") = "+ Math.abs(derror.get(i)) + " tolerance " + tolerance + " \n");