abstract = "Reducing the energy consumption of software systems
though optimisations techniques such as genetic
improvement is gaining interest. However, efficient and
effective improvement of software systems requires a
better understanding of the code-change search space.
One important choice practitioners have is whether to
preserve the system's original output or permit
approximation with each scenario having its own search
space characteristics. When output preservation is a
hard constraint, we report that the maximum energy
reduction achievable by the modification operators is
2.69percent (0.76percent on average). By contrast, this
figure increases dramatically to 95.60percent
(33.90percent on average) when approximation is
permitted, indicating the critical importance of
approximate output quality assessment for code
optimisation. We investigate synergy, a phenomenon that
occurs when simultaneously applied source code
modifications produce an effect greater than their
individual sum. Our results reveal that 12.0percent of
all joint code modifications produced such a
synergistic effect though 38.5percent produce an
antagonistic interaction in which simultaneously
applied modifications are less effective than when
applied individually. This highlights the need for more
advanced search-based approaches.",
notes = "Presented at ESEC/FSE 2018 Journal-First
https://2018.fseconference.org/event/fse-2018-journal-first-approximate-oracles-and-synergy-in-software-energy-search-spaces