Additional energy

To account for energy differences due to the OS and hardware, we use the concept of additional energy. When a software or hardware event occurs in the system within a certain time interval, the software running in the interval is called a $target$. We design the software to be exactly the same except that it does not trigger that event during the same time interval. The resultant software is called a $context$. The additional energy of the event is defined as the target energy minus the context energy. For every GUI event we characterize, a context is carefully designed. Measurement of a target and corresponding context is repeated in an interleaved way to reduce the impact of random factors.