parallelization - data sharing analysis

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Jan Kis

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Jun 4, 2012, 5:45:08 AM6/4/12
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Hi Andreas,

in the following blog post I express some thoughts on the time and amount of the necessary data sharing in the application.

To verify that my view on the necessary data sharing is correct I would need a little bit of help in the form of answering the following questions.

1) In the blog I write that we do not need any data sharing between SCATTER and SOLVE because SOLVE only uses the local currents. My question is: Is it possible / likely for solve to use currents from neighboring cells?

2) Considering the amount of data necessary to transfer: GATHER (and also SOLVE) only uses the Ex and Ey from the grid, so I suppose it is sufficient to share just these and not all the grid properties?

Cheers,
Jan

Andreas Ipp

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Jun 4, 2012, 7:32:57 AM6/4/12
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> 1) [...] Is it possible / likely for solve to use currents from neighboring cells?

No, most probably not. Looking at Maxwell's equations, dE/dt = -j + curl B, so updating E requires j at the same position, but B in a neighborhood. The other Maxwell equation is dB/dt = - curl E, so updating B requires E in a neighborhood.

> 2) Considering the amount of data necessary to transfer: GATHER (and also SOLVE) only uses the Ex and Ey from the grid, so I suppose it is sufficient to share just these and not all the grid properties?

If you mean, Ex, Ey, and Bz, then yes, you only need those.

Cheers,
Andreas
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