Can't use k of 39 (must be <= 31)

[ailtonpcf]

Hey,
I would like to try Krakenuniq with kmers longer than 31, however I get an error:
Can't use k of 39 (must be <= 31)

Is that really true that I can't use bigger kmer values, or a bug?

Thanks in advance,
Ailton.

[salzberg]

yes that's correct - Krakenuniq uses an array that can only hold values up to 2^31 and there are places in the code that would break if you used longer k-mers. (And yes, I know that there are 4^31 possible DNA sequences of length 31.) Changing this would require a major code rewrite. Btw with longer k-mers you lose sensitivity rather quickly.