A simple WAND baseline.
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This code is derived from the following papers:

  1. M. Petri, J. S. Culpepper, and A. Moffat. Exploring the Magic of WAND. Proceedings of the 18th Annual Australasian Document Computing Symposium (ADCS 2013) , pp 58-65, December 2013.

  2. M. Petri, A, Moffat and J. S. Culpepper. Score-safe term dependency processing with hybrid indexes. Proceedings of the 37th Annual International Conference on Research and Development in Information Retrieval (SIGIR 2014) , pp 899-902, July 2014.

  3. S. Gog and M. Petri. Compact indexes for flexible top-k retrieval. In Proc. CPM, pages 207–218, 2015. https://github.com/simongog/surf

Several people have contributed to this codebase over the years. They are:

  • Matthias Petri
  • Simon Gog
  • Joel Mackenzie
  • Yubin Kim
  • Shane Culpepper

Build Info

  • gcc 4.8.x
  • Run ./build.sh to do everything.
  • cat build.sh to see the steps in case you prefer to do them manually.
  • A summary of the steps is:
git submodule init
git submodule update
cd build
cmake28 ..
make -j 5
cd ../external/indri-5.9
make -j 5
cd ../../src
cd ..
cp src/mk_wand_idx bin/mk_wand_idx
cp src/kstem_query bin/kstem_query
cp build/wand_search bin/wand_search

Binary Info

There are two important binaries.

  1. bin/mk_wand_idx GOV2_STOP wand_out This will convert the Indri Index in GOV2_STOP generated using the file ir-repo/index-GOV2_STOP.param. The WAND index will be in the wand_out directory.

  2. bin/wand_search -c wand_out -q ir-repo/gov2-2004.qry -k 1000 -o gov2-2004 Will run queries 701-750 on the GOV2 stopped collection, and generate a timing and run file with the prefix gov2-2004.

Note that the input queries must be Krovetz stemmed if the Indri index is built with Krovetz stemming. There is no stemmer built into the query engine. You can use the kstem_query program to stem a text string. It is up to you to add the query id and ; before the query. See the example query sets in ir-repo for an example.

A note on flags

-e: If set, a completely exhaustive search will be used rather than a WAND traversal.

-i: If set, all query terms for a given query will be used to evaluate each candidate document. The default (that is, the -i flag not set) is to ignore any postings lists where the maximum contribution of any entry in this list is less than some threshold t, defined in util.hpp. For example, given a query q = "the example", t = 0.01 and the maximum contribution of the term "the" = 0.004, then the postings list for "the" will never be utilised.