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Unformatted text preview: em are more difﬁcult to analyze and optimize than the simple loop programs we ﬁrst considered. The basic strategy is to try to make loops more predictable and to try to reduce interactions between store and load operations. When working with large programs, it becomes important to focus our optimization efforts on the parts that consume the most time. Code proﬁlers and related tools can help us systematically evaluate and improve 268 CHAPTER 5. OPTIMIZING PROGRAM PERFORMANCE program performance. We described GPROF, a standard Unix proﬁling tool. More sophisticated proﬁlers are available, such as the VTUNE program development system from Intel. These tools can break down the execution time below the procedure level, to measure performance of each basic block of the program. A basic block is a sequence of instructions with no conditional operations. Amdahl’s Law provides a simple, but powerful insight into the performance gains obtained by improving just one part of the system. The gain depends both on how much we improve this p...
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- Spring '10
- The American