* Use this version if you do not need to keep functors
* @param map the map
* @param func the functor to apply
* @param shared set to true if functors can be shared over the different thread (if false a copy will be used)
* @param nbth number of threads 0 for let the system choose
* @param needMarkers set to yes if you want that each thread use different markers. Warning if set to false (default) do not use algo with thread id or markers !!
* @param shared set to true if functors can be shared over the different thread (if false a copy will be used)
* @param nbth number of thread to use, 0 for let the system choose
* @param needMarkers set to yes if you want that each thread use different markers. Warning if set to false (default) do not use algo with thread id or markers !!