What is "photoanalysisd" and why is it using 77% of my CPU? We got a new iMac for Christmas and it has seemed really slow for the past couple of days. In desperation I checked out Activity Monitor and it shows photoanalysisd as the guilty process that is hogging my CPU. I assume this is related to the Photos app, but that's not even running!

What is "photoanalysisd", why is it using 77% of my CPU, and can I safely stop the process?
Update for 2019, 16" MacBook Pro running Catalina 10.15.2:


start Photos, let it continue past the first dialogue box;
now Preferences in the app menu is clickable (it wasn't before);
Preferences > General , and untick both check boxes in Memories;
close Photos.


This stops photoanalysisd cold, no reboot or kill required.