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Anserini Experiments on Gov2

Indexing:

nohup sh target/appassembler/bin/IndexCollection -collection Gov2Collection \
 -input /path/to/gov2/ -generator JsoupGenerator \
 -index lucene-index.gov2.pos+docvectors -threads 16 -storePositions -storeDocvectors -optimize \
 > log.gov2.pos+docvectors &

The directory /path/to/gov2/ should be the root directory of Gov2 collection, i.e., ls /path/to/gov2/ should bring up a bunch of subdirectories, GX000 to GX272. The command above builds a standard positional index (-storePositions) that's optimized into a single segment (-optimize). If you also want to store document vectors (e.g., for query expansion), add the -docvectors option. The above command builds an index that stores term positions (-storePositions) as well as doc vectors for relevance feedback (-storeDocvectors), and -optimize force merges all index segment into one.

After indexing is done, you should be able to perform a retrieval as follows:

sh target/appassembler/bin/SearchWebCollection \
  -topicreader Trec -index lucene-index.gov2.pos+docvectors -bm25 \
  -topics src/main/resources/topics-and-qrels/topics.701-750.txt -output run.gov2.701-750.bm25.txt

For the retrieval model: specify -bm25 to use BM25, -ql to use query likelihood, and add -rm3 to invoke the RM3 relevance feedback model (requires docvectors index).

Topics and qrels are stored in src/main/resources/topics-and-qrels/. Use trec_eval to compute AP and P30:

eval/trec_eval.9.0/trec_eval src/main/resources/topics-and-qrels/qrels.701-750.txt run.gov2.701-750.bm25.txt

You should be able to replicate the following results:

MAP BM25 BM25+RM3 QL QL+RM3
TREC 2004 Terabyte Track: Topics 701-750 0.2673 0.2953 0.2635 0.2800
TREC 2005 Terabyte Track: Topics 751-800 0.3365 0.3837 0.3263 0.3627
TREC 2006 Terabyte Track: Topics 801-850 0.3053 0.3411 0.2955 0.3199
Mean 0.3030 0.3400 0.2951 0.3209
P30 BM25 BM25+RM3 QL QL+RM3
TREC 2004 Terabyte Track: Topics 701-750 0.4850 0.5306 0.4673 0.4850
TREC 2005 Terabyte Track: Topics 751-800 0.5520 0.5913 0.5167 0.5660
TREC 2006 Terabyte Track: Topics 801-850 0.4913 0.5260 0.4760 0.4873
Mean 0.5094 0.5493 0.4867 0.5128