algorithm2e provides no option to use e.g. the
subsection counter to number the algorithms. It only provides an option to create a new counter within e.g. the
section counter. This counter will then be independent of the
subsection counter, though.
If I read this correctly the solution is to just overwrite the
algocf counter that algorithm2e uses.
\makeatletter \let\c@algocf\c@subsection \makeatother
To have the counter displayed as chapter.section.subsection I did:
I found the answer in Defining shared counters for theorem environments *after* environments are defined