create empty index

[visr]

Hi, I just wanted to try out this package. I've used NearestNeigbors.jl before, but need to be able to add and remove points from the tree efficiently.

I want to start with an empty index (nvectors=0) and build it up, but got stuck on this assert:

IVFADC.jl/src/index.jl

Line 119 in b2a9e0b

@assert k <= nvectors "Number of quantization levels has to be <= $nvectors"

Is there a way to do this? I don't know much about these indices and if this would be the right package for the job.

[zgornel]

Hi. Not really but feasible. Main point is:

• the index relies on a coarse quantizer (often just cluster ceters) and a residual quantizer, both learned from data
• a simple method to build an empty index is to build it and remove all indexed points. The coarse and residual quantizers remain in the object while the points are deleted.
• there is not straightforward way of incrementally building this type of index and it was never supposed to. The quality depends on the initial indexed data.

[visr]

Ok, thanks the additional information! It seems that this is not the right index for my use case. Good to know!

[zgornel]

Yep, seems not. A brutetree from NearestNeighbors might do the job as it is basically brute force NN with a very simple vector of vector structure. For low dimensionalities may be enough...