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Recap. Computational Power Improvement. Multiprocessor. Uniprocessor. C.P.I. 1 2. No. of Processors. Summing m Numbers. Example : summing m numbers On a sequential computer we have, sum = a[0]; for (i=1;i<m;i++) { sum = sum + a[i]; }
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Computational Power Improvement Multiprocessor Uniprocessor C.P.I 1 2 . . . . No. of Processors
Summing m Numbers Example: summing m numbers On a sequential computer we have, sum = a[0]; for (i=1;i<m;i++) { sum = sum + a[i]; } Would expect the running time be be roughly proportional to m.
Summing m Numbers in Parallel • What if we have N processors, with each calculating the m/N numbers assigned to it? • We must add these partial sums together to get the total sum.
Summing Multiprocessors Suppose we have N processors. • The algorithm is as follows: • Each processor finds the local sum of its m/N numbers • Each processor passes its local sum to another processor in a coordinated way • The global sum is finally in processor P11. P11 P12 P13 P21 P22 P23 i P31 P32 P33 j
MB MB P/C P/C Cache Cache NIC NIC Bus/Custom-Designed Network Shared Memory Multiprocessors Shared Memory
MPP (Massively Parallel Processing)Distributed Memory Multiprocessors MB : Memory Bus NIC : Network Interface Circuitry MB MB P/C P/C LM LM NIC NIC Custom-Designed Network
Cluster LD : Local Disk IOB : I/O Bus MB MB P/C P/C M M Bridge Bridge LD LD IOB IOB NIC NIC Commodity Network (Ethernet, ATM, Myrinet)
Grid P/C P/C P/C P/C IOC IOC Hub/LAN Hub/LAN NIC NIC LD LD SM SM SM SM Internet
