When I read the SD training.pl(hts2.2 version)，I found that there is a untied stage, I want to know why do this stage？ why not use the before stage result cluster.mmf(after the herest) as the final model? why do the untied stage then clustered, next using herest result as the final model? what is the function of
adding the untied stage? what is the benefit? Can someone give me an answer? Thank you in advance!