Hi Thomas, If I understand your question correctly, what you want is reduce the number of mappers that spawn streaming processes. The default-parallel controls the number of reducers, so it won't have any effect to the number of mappers. Although the number of mappers is auto-determined by the size of input data, you can try to set "pig.maxCombinedSplitSize" to combine input files into bigger ones. For more details, please refer to: http://pig.apache.org/docs/r0.10.0/perf.html#combine-files
You can also read a discussion on a similar topic here: http://search-hadoop.com/m/J5hCw1UdxTa/How+can+I+set+the+mapper+number&subj=How+can+I+set+the+mapper+number+for+pig+script+ Thanks, Cheolsoo On Tue, Dec 18, 2012 at 12:00 PM, Thomas Bach <[email protected]>wrote: > Hi, > > I have around 4 million time series. ~1000 of them had a special > occurrence at some point. Now, I want to draw 10 samples for each > special time-series based on a similarity comparison. > > What I have currently implemented is a script in Python which consumes > time-series one-by-one and does a comparison with all 1000 special > time-series. If the similarity is sufficient with one of them I pass > it back to Pig and strike out the according special time-series, > subsequent time-series will not be compared against this one. > > This routine runs, but it lasts around 6 hours. > > One of the problems I'm facing is that Pig starts >160 scripts > although 10 would be sufficient. Is there some way to define the > number of scripts Pig starts in a `STREAM THROUGH` step? I tried to > set default_parallel to 10, but it doesn't seem to have any effect. > > I'm also open to any other ideas on how to accomplish the task. > > Regards, > Thomas Bach. >
