Tutorial CUDA
Tutorial CUDA
Tutorial CUDA
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Parallel Reduction Complexity<br />
Takes log(N) steps and each step S performs N/2 S<br />
independent operations<br />
© NVIDIA Corporation 2008<br />
Step complexity is O(log(N))<br />
For N=2 D , performs ∑ S∈[1..D] 2 D-S = N-1 operations<br />
Work complexity is O(N)<br />
Is work-efficient (i.e. does not perform more operations<br />
than a sequential reduction)<br />
With P threads physically in parallel (P processors),<br />
performs ∑ S∈[1..D] ceil(2 D-S /P) operations<br />
∑S∈[1..D]ceil(2D-S /P) < ∑S∈[1..D](floor(2D-S /P) + 1) < N/P + log(N)<br />
Time complexity is O(N/P + log(N))<br />
Compare to O(N) for sequential reduction
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