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Multi-dimensional Unrolling #12

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muellch opened this issue Mar 18, 2020 · 1 comment

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muellch commented Mar 18, 2020

Unrolling a stencil in 2 or even 3 dimensions (+ inlining) might have performance benefits over unrolling into one dimension (+ inlining).

Example in 2D:

Assume for every grid point (i,j) the Laplacians for the 9 surrounding gridpoints have to be calculated (i-1) to (i+1) and (j-1) to (j+1).
We now compare no unrolling to unrolling in one direction by 4 to unrolling in 2 dimensions by 2. We always look at how many Laplacians have to be calculated for 4 grid points.
No Unrolling: 4*9 = 36
Unrolling in one dimension by 4: 9 + 3*3 = 18
Unrolling in two dimensions by 2: 9 + 3 + 4 = 16

Here the unrolling in two dimensions seems to be the best choice for performance

Collaborator

gysit commented Aug 27, 2020

I close this issue since this has rather low priority at the moment. I think we should focus on features and correctness

gysit closed this as completed

gysit reopened this

gysit added the enhancement label

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