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Unformatted text preview: tion “How fast does Program run on Machine ?” ¯ ¯ If the anticipated run times of are long (e.g., greater than 1.0 second), then interval counting should work well enough and be less sensitive to processor load. If the anticipated run times of are in a range of around 0.01 to 1.0 seconds, then it is essential to perform measurements on a lightly loaded system, and to use accurate, cycle-based timing. We should 9.6. PUTTING IT TOGETHER: AN EXPERIMENTAL PROTOCOL 479 Using gettimeofday
0.5 0.4 0.3 Measured:Expected Error 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4 -0.5 Expected CPU Time (ms) 0 50 100 150 200 250 300 Win-NT Linux Linux-comp Figure 9.22: Experimental Validation if Ã -Best Measurement Scheme Using gettimeofday Function. Linux implements this function using cycle counters and hence achieve the same accuracy as do our own timing routines. Windows-NT implements this function using interval counting, and hence the accuracy is low, especially for small duration measurements. 480 CHAPTER 9. MEASURING PROGRAM EXECUTION TIME
perform tests of the gettimeofday library function to determine whether its implementation on machine is cycle based or interval ba...
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