I was under the impression that Lanczos had been long deprecated in Mahout now for a few years and the reason we still have it was only because it was being used by Spectral KMeans clustering.
See http://grepcode.com/file/repo1.maven.org/maven2/org.apache.mahout/mahout-math/0.9/org/apache/mahout/math/decomposer/lanczos/LanczosSolver.java Its still not deprecated as of 0.9, even thou the Release notes for 0.8 mention call out that it will be deprecated in a future release. As one who's finalized the release notes for both 0.8 and 0.9 releases, I apologize for this slip up. While the community internally understands that Lanczos has been long deprecated, but without explicitly marking the code as "deprecated" and updating the project wiki documentation to reflect the same it wouldn't be apparent to a user of the project and its possible that its referenced in talks for comparison with SSVD or other similar methods. Apologies to all of those who have been using/referencing Lanczos in their work or talks. For the upcoming release: 1. Refactor Spectral KMeans to use SSVD (Shannon, this is now a high priority) 2. Deprecate Lanczos, I prefer completely purging it from the codebase. 3. Ensure the Release notes and Wiki documentation reflect that very clearly. Thanks.
