Although adaptive processors can exploit application variability to improve performance or save energy, effectively managing their adaptivity is challenging. To address this problem, we introduce a new approach to adaptivity: the Positional approach. In this approach, both the testing of configurations and the application of the chosen configurations are associated with particular code sections. This is in contrast to the currently-used Temporal approach to adaptation, where both the testing

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... application of configurations are tied to successive intervals in time. We propose to use subroutines as the granularity of code sections in positional adaptation. Moreover, we design three implementations of subroutine-based positional adaptation that target energy reduction in three different workload environments: embedded or specialized server, general purpose, and highly dynamic. All three implementations of positional adaptation are much more effective than temporal schemes. On average, they boost the energy savings of applications by 50% and 84% over temporal schemes in two experiments. To combine ease of implementation and effectiveness, we propose to use subroutines as the granularity of code sections in positional adaptation. Moreover, we propose three implementations of subroutine-based positional adaptation that are generic, easy to implement, and effective. Each implementation targets a different workload environment: embedded or specialized server, general purpose, and highly dynamic. Our results show that all three implementations of subroutine-based positional adaptation are much more effective than temporal schemes. On average, they boost the energy savings of applications by 50% and 84% over temporal schemes in two experiments. This paper is organized as follows: Section 2 describes in more detail subroutine-based positional adaptation; Section 3 presents our three different implementations; Section 4 discusses our evaluation environment; Section 5 evaluates the implementations; Section 6 discusses related work, and Section 7 concludes.