On Aug 18, 2011, at 5:02 PM, Alan Wei wrote:
> Dear all,
> I hope you're having a nice day.
> I'm trying to get the x, y-value of a coordinate created by DMDACreate2d.
> Lines I wrote down are:
>
> DMDAGetCoordinateDA(da, &cda);
> DMDAGetGhostedCoordinates(da, &gc);
> DMDAVecGetArray(cda, gc, &coors);
>
> for (i = xs; i < xs+xm; i++) {
> for (j = ys; j < ys+ym; j++) {
> printf("%f %f\n", coors[j][i].x, coors[j][i].y);
> }
> }
>
> DMDAVecRestoreArray(cda, gc, &coors);
>
> I wonder why I need to use "DMDAVecRestoreArray(cda, gc, &coors);" I used it
> because the manual said I need. Actually, I tried to comment it out and there
> is no difference.
>
> Thanks,
> Alan
The practical reason is you might get memory bleeding if you don't. The
philosphical reason is that a call DMDAVecGetArray() or VecGetArray() or others
is a request to access the internal data structure of an object, the object
then gives you permission to access that data. the RestoreArray() is a
statement by you that after this call you will NOT access that data directly
(without another GetArray call). Imagine if you did
Barry
