09f_cpe431_chap7_9 - UAH Chapter 7 (4th Ed.) CPE 431/531...

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1 1 Electrical and Computer Engineering CPE 431/531 Chapter 7 – Multicores, Multiprocessors and Clusters Dr. Rhonda Kay Gaede UAH Electrical and Computer Engineering Page 2 of 23 UAH CPE 431/531 Chapter 7 (4 th Ed.) 7.1 Introduction - Motivation Why multiprocessors? ____________________ ____________________ ____________________ Electrical and Computer Engineering Page 3 of 23 UAH CPE 431/531 Chapter 7 (4 th Ed.) 7.2 The Difficulty of Creating Parallel Processing Programs The difficulty with parallelism is not the _________, it’s the ________. Why is it difficult to write parallel processing programs that are fast? ____________ ____ ___________ ___________ ____ ____________ _________ ________ ___ Electrical and Computer Engineering Page 4 of 23 UAH CPE 431/531 Chapter 7 (4 th Ed.) 7.2 The Difficulty of Creating Parallel Processing Programs - Speedup Challenge Suppose you want to achieve a speedup of 90 times faster with 100 processors. What percentage of the original computation can be sequential? Electrical and Computer Engineering Page 5 of 23 UAH CPE 431/531 Chapter 7 (4 th Ed.) 7.2 The Difficulty of Creating Parallel Processing Programs - Bigger Problem Suppose you want to perform two sums: one is a sum of 10 scalar variables and one is a matrix sum of a pair of two- dimensional arrays, size 10 by 10. What speedup do you get with 10 versus 100 processors ? Electrical and Computer Engineering Page 6 of 23 UAH CPE 431/531 Chapter 7 (4 th Ed.) 7.2 The Difficulty of Creating Parallel Processing Programs - Bigger Problem Next, calculate the speed-ups assuming the matrices grow to 100 by 100 Strong scaling Weak scaling Electrical and Computer Engineering Page 7 of 23 UAH CPE 431/531 Chapter 7 (4 th Ed.) 7.2 The Difficulty of Creating Parallel Processing Programs – Balancing Load To achieve the speed-up of 91 on the previous larger problem with 100 processors, we assumed the load was perfectly balanced (each processor did 1 % of the work). Instead, show the impact on speed-up if one processor’s load is higher than al the rest. Calculate at 2% and 5%. Electrical and Computer Engineering Page 8 of 23 UAH CPE 431/531 Chapter 7 (4 th Ed.) 7.3 Shared Memory Multiprocessors A shared memory multiprocessor (SMP) is one that offers the programmer a _____ ________ ______ _____ across al processors Processor communicate through ______ __________ in memory. SMPs come in two flavors – ______ – ______ Processors need to coordinate when sharing data, this process is cal ed ______________, processors must acquire a _____ Electrical and Computer Engineering Page 9 of 23 UAH CPE 431/531 Chapter 7 (4 th Ed.) 7.3 Shared Memory Multiprocessors - Parallel Program Suppose we want to sum 100,000 numbers on an SMP with UMA. Let’s assume we have 100 processors
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09f_cpe431_chap7_9 - UAH Chapter 7 (4th Ed.) CPE 431/531...

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