[Xapian-devel] Questions on letor module

[Jia Xu]

Hi,

  I have several questions regarding the letor module,I looked at the
framework of learning to rank in xapian
http://rishabhmehrotra.com/gsoc/17.png, I am a little confused. Why using
deep learning to find unsupervised features in test data? Since in my
understanding, learning to rank model usually learn features from the
training data then apply the model to the test data? Why test set and
training set have different features? And deep learning is to extract
hidden features from the data set, I don't think it is necessary to use it
in this problem. Furthermore, I didn't see any implementation in the source
code for deep learning, is it actually included in letor?

  For the source code
https://github.com/rishabhmehrotra/xapian/tree/397034af42c9b1998730160176d219d6f8f38b25/xapian-letor,
the last update is about 2 years ago, is that the latest version of the
code? For several files such as ranker.cc, evalmetric.cc, there is no
implementations of functions, I don't know if they have been implemented
somewhere in the module(as far as I read through the source code, I didn't
see any).

 For the tests,  are there any benchmark tests on SVM based or listnet
models on sample datasets and what the NDCG or MAP scores of them ( I
didn't see any measure methods have been implemented in the current
module)? And how about the cross validation for the training set? Is there
any method included in the current project?

For SVM method, I found letor_learn_model() has been commented out, but I
didn't find any other file contain this function (or maybe in
letor_internal.cc)?

Finally I found a file called letor_internal_refactored.cc file, is that
the latest version of letor_internal.cc ? Is letor_internal.cc
still being used?

Thank you very much. I am waiting for your reply.

-- 
Jia Xu
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