Basic 'SUM' question

[Scott]

Hello fellow Pig users.  I am brand new to Pig/hadoop, and am having 
trouble with something that I am guessing is very basic.  I have a 
relation where I did a group by several values, then counted the 
groups.  Here is a description of the relation:

count_grouped: {g1: (site: chararray,tf: chararray,pos: 
chararray,country: chararray,state: chararray,dma: chararray),imp_count: 
long}


Now I would like to calculate the sum of the imp_count value to get a 
grand total.  The docs indicate I need to do a 'GROUP ALL' to compute a 
global sum, but I can't seem to  make that work.  Any help would be 
appreciated.


Thanks,
Scott