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Looping Over the Grid

As described in section 7.2, each processor stores n values in the $i$ direction and N values in each other direction. In addition, each processor stores one extra ``buffer'' value of $i$ at each end of its grid for calculating spatial derivatives. To loop over all gridpoints in 3D, for example, you would write

for(i=1;i \le n;i++) \;\;\;\; for(j=0;j<N;j++) \;\;\;\; for(k=0;k<N;k++)
\end{displaymath} (7.1)

The macro LOOP automatically does this looping correctly. If you are calculating the average of a quantity across the entire lattice you will need to gather the results from all the processors after the loop is completed. The simplest way to do this is with the functions MPI_Reduce() or MPI_Allreduce(). These are explained in any standard reference on MPI, and you can find examples of them in CLUSTEREASY.

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This documentation was generated on 2008-01-21