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Foil 6 Some Inefficiencies of the N2 Algorithm - II

From CPS615-End of N-Body Discussion and Beginning of Numerical Integration Delivered Lectures of CPS615 Basic Simulation Track for Computational Science -- 15 October 96. by Geoffrey C. Fox *
Secs 115.2
Also, all particle information is sent to all processors, taking O(N2) space whereas natural algorithms use O(N) space and this is how special purpose machines like GRAPE get their cost effectiveness
  • If N is one million as for globular cluster problem, there is a big difference between DRAM cost of 106 and 1012 units of memory
Space is further wasted as everything is spread to 3 dimensional arrays even when arrays like mass are naturally one dimensional!

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