VectorList is a rather odd beast. it's a cool idea. It increases in # of rows dynamically, unlike all other Matrix classes (which was coded wrong and inspired this patch). It can fail on given accesses, throwing a null pointer if you have not supplied a vector for a row.
And, if you say "like(4,3)" it cannot make a vector matching your existing vector type with "like(3)", because Vector only has 'like()' and no 'like(int length)'. I was not using it for sparseness. In fact, looking back, I was misusing it. Perhaps it should not exist? On Mon, Jul 11, 2011 at 9:34 PM, Ted Dunning <ted.dunn...@gmail.com> wrote: > I haven't been able to track all of this, but I think things are going in an > odd direction. > > - DenseVector is not a reasonable default for something that appears to be > intended to support various flavors of sparse matrices. > > - null rows are not a problem. Interpret them as all zero > > - setting the number of rows and columns does not imply allocation. Neither > does a legal access. The only thing that implies allocation is setting a > value to non-zero. > > On Mon, Jul 11, 2011 at 9:06 PM, Lance Norskog (JIRA) <j...@apache.org>wrote: > >> >> [ >> https://issues.apache.org/jira/browse/MAHOUT-756?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13063705#comment-13063705] >> >> Lance Norskog commented on MAHOUT-756: >> -------------------------------------- >> >> When it is this confusing, UnsupportedOperationException is permissible. >> There is no obvious right thing to do. What if there are different Vector >> classes and some empty slots? >> >> Using DenseVector/Matrix is the default policy in other places, so let's go >> with that. If your program runs out of memory, you'll eventually find all of >> the DenseVectors and track down the problem. In the meantime, it will be >> slow but will work. >> >> > VectorList (Matrix implementation) does not maintain cardinality getters >> correctly >> > >> ---------------------------------------------------------------------------------- >> > >> > Key: MAHOUT-756 >> > URL: https://issues.apache.org/jira/browse/MAHOUT-756 >> > Project: Mahout >> > Issue Type: Bug >> > Components: Math >> > Reporter: Lance Norskog >> > Priority: Minor >> > Attachments: VectorList.patch >> > >> > >> > VectorList (implements Matrix) is dynamically expandable, row-wise. There >> are three different ways to query the size of a Matrix, and VectorList does >> not correctly supply these values. >> > >> >> -- >> This message is automatically generated by JIRA. >> For more information on JIRA, see: http://www.atlassian.com/software/jira >> >> >> > -- Lance Norskog goks...@gmail.com
