Impact of GCC optimization levels in energy consumption during C/C++ program execution

In the context of a research project aimed at studying patterns for energy consumption at runtime in order to transform the original software into executable programs that consume less energy, we are carrying out a master's thesis looking for ways to get this improvement at the code generation phase. First we investigated how the hardware manufacturers have been and are concerned with green issues, aiming to find whether the modern processors are delivered with instruction sets that express the energy required to execute each operation, and whether they include code alternatives cheaper in terms of electric energy. In this paper we intend to describe a second step in this project. We will analyze the influence of GCC optimizations on the energy consumed by a program. We will compare the consumption of a given program compiled without any optimization with other versions of the same program compiled with different levels of optimization. The experiment conducted has shown that actually options-Ofast and -O3 generate a faster code that decreases the energy consumed. We report in the paper the study carried on, presenting the experimental setup and the method followed to measure and compare the resources consumed by a program during execution, and then we discuss the results obtained.