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Practice problem 56 as another example of code with

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Unformatted text preview: consisting of various patterns of of ·½s and ½s. For regular patterns (e.g., all ·½s, all ½s, or alternating ·½ and ½s), we ﬁnd the function requires between 13.01 and 13.41 cycles. We use this as our estimate of the performance with perfect branch condition. On an array set to random patterns of ·½s and ½s, we ﬁnd that the function requires 20.32 cycles. One principle of random processes is that no matter what strategy one uses to guess a sequence of values, if the underlying process is truly random, then we will be right only 50% of the time. For example, no matter what strategy one uses to guess the outcome of a coin toss, as long as the coin toss is fair, our probability of success is only 0.5. Thus, we can see that a mispredicted branch with this processor incurs a penalty of around 14 clock cycles, since a misprediction rate of 50% causes the function to run an average of 7 cycles slower. This means that calls to absval require between 13 and 27 cycles depending on the success of the branch pre...
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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.

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