Computation-domain.md

@@ -79,3 +79,25 @@ int ixyz = iz + lNZ*iy + lNZ*lNY*ix;
 h_densities.density_a[ixyz]; // value of density in center of the box
 ```  
 
+#Iterating over lattice points
+The following scheme is used to iterate over lattice points.
+```c
+int lNX=h_densities.nx, lNY=h_densities.ny, lNZ=h_densities.nz; // local sizes
+// or ...
+// int lNX=NX, lNY=NY, lNZ=NZ;
+int ix, iy, iz, ixyz;
+
+// ITERATE OVER ALL POINTS
+ixyz=0;
+for(ix=0; ix<lNX; ix++) for(iy=0; iy<lNY; iy++) for(iz=0; iz<lNZ; iz++)
+{
+    double x = DX*(ix-lNX/2);
+    double y = DY*(iy-lNY/2); // for 1d code y will be always 0
+    double z = DZ*(iz-lNZ/2); // for 1d and 2d codes z will be always 0
+    
+    // ... compute something for coordinate (x,y,z) ....
+    // rho_a[ixyz]=...;
+
+    ixyz++; // go to the next point, it should be the last line of the triple loop
+}
+```