most importantly, what's your number of non-zero elements. (or input sequence file size).
On Fri, Sep 14, 2012 at 2:19 PM, Dmitriy Lyubimov <[email protected]> wrote: > Q job is actually the fastest and map-only.I'd say you drop all the > optional parameters (including p) and use mahout 0.7. > > Actually reducing split size is unlikely to help. Default split should be > fine. > > i'd say running -k 10 on any sized input should result in Q mapper > task running in at most couple of minutes. > > using -k200 -p100 is fairly ambitious (mapper task running time will > scale a little worse then proportional to k+p). > > if you use -q1 you will likely to have more problems with ABt job and > that may require some memory tuning... > > otherwise check the usual things -- memory, cluster capacity (do you > actually have capacity running 100 mappers? Do they have at least 1G > of RAM on -Xmx without scratching the swap? Are you seeing GC > thrashing? etc.) > > That said your problem doesn't seem too big (judging from 100 mappers > with a regular split size, that should be ok). with -k 100 and default > p you should expect single q task to run about 20-25 minutes, > depending on your hardware. It is cpu-bound (or rather, mostly > fpu-bound, assuming you tackled memory issues etc.) > > > On Fri, Sep 14, 2012 at 1:24 PM, lei tang <[email protected]> wrote: >> Hi, >> >> I am using mahout's SSVD (stochastic SVD) to factorize a huge sparse >> matrix (around 30M x 1M). I used a modified script of >> http://bickson.blogspot.com/2011/02/mahout-svd-matrix-factorization.html >> to store the input matrix with <key, value> pairs being integer, and >> vectorwritable (in particular, SequentialAccessSparseVector). Should I >> change to RandomAccessSparseVector? >> >> I managed to run mahout SSVD with the following specification. >> mahout ssvd -Dmapred.max.split.size=1000000 -i mf/tr_full.seq -o >> mf/out_full -k 200 -p 100 -r 100000 -U true -V true -t 20 --tempDir mf/tmp >> >> I specified the max split in order to have more mappers. However, the >> first Qjob seems not moving. After 1 hour, it is still 12% with 100 >> mappers. Is this expected? Should I change any parameter? >> >> Any suggestion is highly appreciated. >> >> - Lei >> P.S. I'm also reading the docs from >> https://issues.apache.org/jira/browse/MAHOUT-376 in hope that I can figure >> out why it is so slow.
