Hi @tremblap, sorry for the delay,
I haven’t coded the descriptors in orchidea myself, but I’m sure they do not rely on ircamdescriptors, the code is very lightweighted and I think Carmine rewrote them from scratch. I think Carmine is going to release the sources on github at some point, so you will also be able to doublecheck directly.
As for the distances in dada, if you refer to dada.distances, indeed that is multidimensional scaling using the simpmatrix library, as @jamesbradbury said. If you mean instead how do we measure the distances for knn, for the time being it’s just euclidean distance, but you can assign weights to each dimension to compensate for differences of magnitude (e.g. knn 4 [400 6000] [1. 0.1]) That’s all manual, and I really wouldn’t take my knn handling as a reference, it’s very naively coded.