yes, the UpperTriangular in SSVD doesn't support some of the Matrix operations. On top of it, it is built with some assumptions that Mahout support in general should not have, or have an alternative for, for efficiency sake of ssvd:
1) it assumes the matrix is dense. 2) most importantly, it assumes the matrix is sufficiently small (it packs it into a single vector). that means it may experience problems when dense allocation exceeds 2G contiguous heap chunk. 3) consequently, it only serializes into a dense vector. for diagonal matrices, the same ssvd uses vector form. It does mean that you don't have a nice single method to implement multiplication; but it is just one vector-scalar loop instead, but oh well. -d On Sat, Jan 14, 2012 at 2:03 AM, Tamas Jambor <[email protected]> wrote: > thanks, ideally I would need both symmetric and diagonal. > > On Sat, Jan 14, 2012 at 8:26 AM, Sebastian Schelter <[email protected]> wrote: > >> I think Tamas referred to matrices that are symmetric (only the upper >> triangular half would need to be stored) not diagonal matrices. >> >> >> On 14.01.2012 05:25, Lance Norskog wrote: >> > org.apache.mahout.math.DiagonalMatrix >> > >> > It even supports sparse values in the diagonal! >> > >> > On Fri, Jan 13, 2012 at 9:00 AM, Tamas Jambor (Commented) (JIRA) >> > <[email protected]> wrote: >> >> >> >> [ >> https://issues.apache.org/jira/browse/MAHOUT-737?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13185670#comment-13185670] >> >> >> >> Tamas Jambor commented on MAHOUT-737: >> >> ------------------------------------- >> >> >> >> I think so. When will you be releasing 0.6? I am planning to do a bit >> more extensive testing in the next 2-3 weeks. >> >> >> >>> Implicit Alternating Least Squares SVD >> >>> -------------------------------------- >> >>> >> >>> Key: MAHOUT-737 >> >>> URL: https://issues.apache.org/jira/browse/MAHOUT-737 >> >>> Project: Mahout >> >>> Issue Type: New Feature >> >>> Components: Collaborative Filtering >> >>> Affects Versions: 0.6 >> >>> Reporter: Tamas Jambor >> >>> Assignee: Sebastian Schelter >> >>> Attachments: MAHOUT-737-2.patch, MAHOUT-737.patch, >> MAHOUT-737.patch, MAHOUT-737.patch, MAHOUT-737.patch >> >>> >> >>> >> >>> I am sharing this Java implementation of mine that is based on the >> paper - Collaborative Filtering with Implicit Datasets. The implementation >> is multi-treading and can be easily extended to use it on Hadoop. In fact >> this approach would possibly work with non-implicit datasets, but further >> testing is needed. The algorithm is tried and tested on an implicit >> TV-viewing dataset, and the performance was pretty good (details to follow). >> >> >> >> -- >> >> This message is automatically generated by JIRA. >> >> If you think it was sent incorrectly, please contact your JIRA >> administrators: >> https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa >> >> For more information on JIRA, see: >> http://www.atlassian.com/software/jira >> >> >> >> >> > >> > >> > >> >>
