Should one interrupt the prayer upon remembering the absence of ablution during it, and what is the ruling on the prayer if one remembers the absence of ablution after concluding it?

"Whoever remembers during or after the prayer that he prayed without ablution, his prayer is void and must be repeated. As for whoever doubts the validity of his ablution during or after the prayer, his prayer is valid and he is not required to repeat it, because the default is the persistence of purity. However, if a person is certain of having invalidated his ablution and doubts whether he performed ablution or not, he must repeat the prayer, because the default is not having performed ablution."