If you do not supply HeNCE with a cost matrix when you either build or run a program, it will use a default in which the all nodes will run on a single host- the host on which htool is running. Of course, this means that no parallelism will be realized since only one processor is available. This mode is convenient when first learning HeNCE since you can run programs while completely ignoring the issue of cost matrices. It also may be helpful during program debugging.