[ImageJ-devel] Local Neighborhood stuff

[Tobias Pietzsch]

On 08/20/2012 02:50 PM, Jean-Yves Tinevez wrote:
> Hi Stephan
>
> Just to be sure I got your point:
>
> You mean that if we iterate over all the neighbohoods of a single final
> image in a multithreaded way, we might screw up with the unsafe
> implementations right? In a pseudo code, this:
>
> for (int i =0; i < nThreads, i++) {
>    threads[i] = new Thread() {
>
>      public void run() {
>
>               for ( Neighborhood<T> n : chunks)
>                      for ( T t : n )
>            ...
> ...
> ...
>
> would always fail with the unsafe implementation and always work with
> safe implementations? Right??

Hi Jean-Yves,

No. That would work in all cases, because the outer loop
for ( Neighborhood<T> n : chunks) uses one Cursor<Neighborhood<T>> and 
those are just completely normal cursors.


What would be problematic would be something like:

for ( Neighborhood<T> n : chunks)
    parallel( n );

void paralled( IterableInterval<T> iterable )
{
    for (int i =0; i < nThreads, i++) {
       threads[i] = new Thread() {
       public void run() {
          for ( T t : iterable )
              ...
}

because every thread would get the same Cursor<T> for the unsafe
variant.

best regards,
Tobias