IPhoto 9.5.1 keeps hanging when updating faces.

Question

Hi, Basically what the subject says. I open up iphoto. Go to faces>persons name and then confirm additonal faces. Click done, then I get the spinning ball of death for hours. I have done the whole rebuilding the data base still no joy. So fustrating iPhoto used to work so well.
A few points; my iPhoto library contains about 18,000 photos and the library sits on an external hard drive.
Any help would be appeciated.

Answer 1

genpro I think you are seeing what I have seen many times.  I hesitate to disagree with so formidable and respected an authority as Old Toad, but I do think there is more to this issue, and that the real problem has been missed. 
What happens is that the process that searches for new faces takes a long time to run.  While it runs iPhoto becomes unresponsive, as you have noted.  When iPhoto finishes all its database housekeeping it becomes responsive.  You can see this by watching iPhoto's use of cpu time in Activity Monitor.  When suggested found faces are confirmed as correct or as incorrect, iPhoto seems to go through several steps.  One is marking the databases according the the confirmed responses, another is using the newly modified database of positive face exemplars to search the newly modified database of all found faces.  When these databases become large, the calculations ale a very long time.  The search algorithm apparently stores intermediate values during the search.  When these databases become large, the intermediate stored values become impossibly large.  Often large amounts of virtual memory are used, meaning the data manipulation requires disk access and swapping, slowing the process much more.   The combination of slow complex calculation and massive intermediate stored value overwhelms your computer.  When the search ends cpu cycles become available and memory becomes freed, and iPhoto and your computer return to normal operation. 
When you used iPLM the search for new found faces proceeded slightly differently, and did not hold up the computer. 
Use Activity Monitor to observe cpu and memory usage next time you confirm suggested found faces, and you will see what I am telling you. 
One workaround is to do something else and let iPhoto run until it is finished,  This only works for smaller libraries or smaller sets of exemplars.  For larger ones the memory requirements can easily be too great for the Faces search to complete.  In this case the only solution is to Force-Quit iPhoto.  In general Force-Quit while a database is updating is not a good idea.  In this case it seems to be the only solution, and usually does not seem to cause too much trouble. 
I have reported this to Apple.  I urge you to do so also. 
As LarryHN notes, "I find Faces more that a bit flaky".