--global-ranking, impact and when to set lower?

[fpusan]

Hi and thanks for the continued development and maintenance of DIAMOND.

I'm interested in speeding up searches against NCBI nr. Ideally I would like to get only the top 10-20 hits, even if they are not very good.

I've seen here that I can use the --fast mode, which afaik is optimized for hits with >90% identity. I have also seen you mention that -g100 can speed things up if you only need the best hits for each query. I didn't fully undertood what it did exactly, or whether it came with a lower sensitivity against low identity hits.

Could you elaborate a bit on when to set -g lower than the default and the expected consecuences of doing so?

Thanks in advance