SoftExplorer: Estimating and Optimizing the Power and Energy Consumption of a C Program for DSP Applications
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SoftExplorer: Estimating and Optimizing the Power and Energy Consumption of a C Program for DSP Applications Eric Senn LESTER, University of South-Brittany, BP 92116, 56321 Lorient Cedex, France Email: [email protected]
Johann Laurent LESTER, University of South-Brittany, BP 92116, 56321 Lorient Cedex, France Email: [email protected]
Nathalie Julien LESTER, University of South-Brittany, BP 92116, 56321 Lorient Cedex, France Email: [email protected]
Eric Martin LESTER, University of South-Brittany, BP 92116, 56321 Lorient Cedex, France Email: [email protected] Received 30 January 2004; Revised 20 October 2004 We present a method to estimate the power and energy consumption of an algorithm directly from the C program. Three models are involved: a model for the targeted processor (the power model), a model for the algorithm, and a model for the compiler (the prediction model). A functional-level power analysis is performed to obtain the power model. Five power models have been developed so far, for different architectures, from the simple RISC ARM7 to the very complex VLIW DSP TI C64. Important phenomena are taken into account, like cache misses, pipeline stalls, and internal/external memory accesses. The model for the algorithm expresses the algorithm’s influence over the processor’s activity. The prediction model represents the behavior of the compiler, and how it will allow the algorithm to use the processor’s resources. The data mapping is considered at that stage. We have developed a tool, SoftExplorer, which performs estimation both at the C-level and the assembly level. Estimations are performed on real-life digital signal processing applications with average errors of 4.2% at the C-level and 1.8% at the assembly level. We present how SoftExplorer can be used to optimize the consumption of an application. We first show how to find the best data mapping for an algorithm. Then we demonstrate a method to choose the processor and its operating frequency in order to minimize the global energy consumption. Keywords and phrases: power, energy, estimation, optimization, C program, DSP applications.
1. INTRODUCTION Lowering the power consumption of today’s electronic devices is more than ever a crucial challenge. Indeed, the market of mobile devices has exploded those last years: laptop computers, pocket PC, tablet PC, PDA, mobile phones, and so forth. It is remarkable that there is less and less difference between all these devices. With mobile phones, you can take pictures, record movies, or surf the internet as easily as with any laptop. A common point between all those new multimedia materials is the necessity to comply with the Universal Mobile Telecommunication Systems (UMTS) norm [1].
UMTS was adopted as the international norm for mobile telecommunication systems of the third generation (3G). It defines a set of high-speed services: voice, image, file transfer, fax, videoconference, as well as the capability to connect to any kind of network from any kind of place. Flexibility and re
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