Advanced Computer Architecture CSE 8383Grosch’s Law (1960s)Moore’s LawVon Neumann’s bottleneckProblemParallelismSuperscalar ParallelismPast Trends in Parallel Architecture (inside the box)New Trends in Parallel Architecture (outside the box)SpeedupSlide 12Amdahl’s LawExampleSlide 15Amdahl’s Law (1967)Slide 17Slide 18Gustafson-Barsis LawSlide 20Slide 21Distributed Computing PerformanceSlide 23Benchmark PerformanceComputer Science and EngineeringCopyright by Hesham El-RewiniAdvanced Computer Advanced Computer ArchitectureArchitectureCSE 8383CSE 8383February 23 2006February 23 2006Session 12Session 12Computer Science and EngineeringCopyright by Hesham El-Rewini Grosch’s LawMoore’s LawVon Neumann’s BottlneckParallelismSpeedupAmdahl’s LawThe Gustafson-Barsis LawBenchmarks Performance EvaluationComputer Science and EngineeringCopyright by Hesham El-RewiniGrosch’s Law (1960s)“To sell a computer for twice as much, it must be four times as fast”Vendors skip small speed improvements in favor of waiting for large onesBuyers of expensive machines would wait for a twofold improvement in performance for the same price.Computer Science and EngineeringCopyright by Hesham El-RewiniMoore’s LawGordon Moore (cofounder of Intel)Processor performance would double every 18 monthsThis prediction has held for several decadesUnlikely that single-processor performance continues to increase indefinitelyComputer Science and EngineeringCopyright by Hesham El-RewiniVon Neumann’s bottleneckGreat mathematician of the 1940s and 1950sSingle control unit connecting a memory to a processing unitInstructions and data are fetched one at a time from memory and fed to processing unitSpeed is limited by the rate at which instructions and data are transferred from memory to the processing unit.Computer Science and EngineeringCopyright by Hesham El-RewiniProblem Assume that a switching component such as a transistor can switch in zero time. We propose to construct a disk-shaped computer chip with such a component. The only limitation is the time it takes to send electronic signals from one edge of the chip to the other. Make the simplifying assumption that electronic signals travel 300,000 kilometers per second. What must be the diameter of a round chip so that it can switch 109 times per second? What would the diameter be if the switching requirements were 1012 time per second?Computer Science and EngineeringCopyright by Hesham El-RewiniParallelism Multiple CPUsWithin the CPUOne PipelineMultiple pipelinesComputer Science and EngineeringCopyright by Hesham El-RewiniSuperscalar ParallelismSchedulingComputer Science and EngineeringCopyright by Hesham El-RewiniPast Trends in Parallel Architecture (inside the box)Completely custom designed components (processors, memory, interconnects, I/O)Longer R&D time (2-3 years)Expensive systemsQuickly becoming outdatedBankrupt companies!!Computer Science and EngineeringCopyright by Hesham El-RewiniNew Trends in Parallel Architecture (outside the box)Advances in commodity processors and network technologyNetwork of PCs and workstations connected via LAN or WAN forms a Parallel SystemNetwork ComputingCompete favorably (cost/performance)Utilize unused cycles of systems sitting idleComputer Science and EngineeringCopyright by Hesham El-RewiniSpeedupS = Speed(new) / Speed(old)S = Work/time(new) / Work/time(old)S = time(old) / time(new)S = time(before improvement) / time(after improvement)Computer Science and EngineeringCopyright by Hesham El-RewiniSpeedupTime (one CPU): T(1)Time (n CPUs): T(n)Speedup: SS = T(1)/T(n)Computer Science and EngineeringCopyright by Hesham El-RewiniAmdahl’s Law The performance improvement to be gained from using some faster mode of execution is limited by the fraction of the time the faster mode can be usedComputer Science and EngineeringCopyright by Hesham El-Rewini20 hours200 milesABWalk 4 miles /hourBike 10 miles / hourCar-1 50 miles / hourCar-2 120 miles / hourCar-3 600 miles /hourmust walkExampleComputer Science and EngineeringCopyright by Hesham El-Rewini20 hours200 milesABWalk 4 miles /hour 50 + 20 = 70 hours S = 1Bike 10 miles / hour 20 + 20 = 40 hours S = 1.8Car-1 50 miles / hour 4 + 20 = 24 hours S = 2.9Car-2 120 miles / hour 1.67 + 20 = 21.67 hours S = 3.2Car-3 600 miles /hour 0.33 + 20 = 20.33 hours S = 3.4must walkExampleComputer Science and EngineeringCopyright by Hesham El-RewiniAmdahl’s Law (1967) : The fraction of the program that is naturally serial(1- ): The fraction of the program that is naturally parallelComputer Science and EngineeringCopyright by Hesham El-RewiniS = T(1)/T(N)T(N) = T(1) + T(1)(1- )NS = 1 + (1- )N=NN + (1- )Computer Science and EngineeringCopyright by Hesham El-RewiniAmdahl’s LawComputer Science and EngineeringCopyright by Hesham El-RewiniGustafson-Barsis LawN & are not independent from each other T(N) = 1T(1) = + (1- ) NS = N – (N-1) : The fraction of the program that is naturally serialComputer Science and EngineeringCopyright by Hesham El-RewiniGustafson-Barsis LawComputer Science and EngineeringCopyright by Hesham El-RewiniComputer Science and EngineeringCopyright by Hesham El-RewiniDistributed Computing PerformanceSingle Program PerformanceMultiple Program PerformanceComputer Science and EngineeringCopyright by Hesham El-RewiniComputer Science and EngineeringCopyright by Hesham El-RewiniBenchmark PerformanceSerial BenchmarksParallel BenchmarksPERFECT BenchmarksNAS KernelThe SLALOMThe Golden Bell PrizeWebSTONE for the WebPerformance
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