some improvements about the latent semantic search, more details are in Description part [LUCENE-4458]

Hi,all,Recently I invented a new ranking algorithm inspired by the theory of spread activation and probabilistic model, which can find the latent semantic relationship between docs and terms and is almost linear time, and I took one afternoon to code and implement this algorithm. And the testing result shows that the speed of this algorithm is much faster than the famous Latent Semantic Analysis algorithm, and the affect is almost as good as the LSA. I wanna share my idea to all of you and add this algorithm to the Lucene project.

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Migrated from [LUCENE-4458](https://issues.apache.org/jira/browse/LUCENE-4458) by wang jianping, 1 vote

Start by reading the migrated LUCENE-4458 entry and the issue description to understand the proposed latent semantic search and ranking algorithm. The payload names no Lucene files, tests, entry points, acceptance criteria, or implementation scope, so the intended definition of done needs to be established before work begins.

Written by the indexing model from the issue text.