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Unformatted text preview: get_counter(); } This could easily yield misleading results if some other process also executes between the two calls to the counter routines. This is especially a problem if either the machine is heavily loaded, or if the run time for P is especially long. This phenomenon is illustrated in Figure 9.11. This ﬁgure shows the result of repeatedly measuring a program that computes the sum of an array of 131,072 integers. The times have been converted into milliseconds. Note that the run times are all over 36 ms, greater than the timer interval. Two trials were run, each measuring 18 executions of the exact same procedure. The series labeled “Load 1” indicates the run times on a lightly loaded machine, where this is the only process actively running. All of the measurements are within 3.4% of the minimum run time. The series labeled “Load 4” indicates the run times when three other processes making heavy use of the CPU and memory system are also running. 9.4. MEASURING PROGRAM EXECUTION TIME WITH CYCLE COUNTERS
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This note was uploaded on 09/02/2010 for the course ELECTRICAL 360 taught by Professor Schultz during the Spring '10 term at BYU.
- Spring '10
- The American