Hello,
sum and threshold are both Integers.
for the threshold variable I first add a new resource to the
configuration - conf.addResource( ... );
later I get the threshold value from the configuration.
Code
#####################################
private int threshold;
public void setup( Context context ) {
Configuration conf = context.getConfiguration();
threshold = conf.getInt( "threshold", -1 );
}
#####################################
Best,
Peter
On 11.05.2015 19:26, Shahab Yunus wrote:
What is the type of the threshold variable? sum I believe is a Java int.
Regards,
Shahab
On Mon, May 11, 2015 at 1:08 PM, Peter Ruch <[email protected]
<mailto:[email protected]>> wrote:
Hi,
I am currently playing around with Hadoop and have some problems
when trying to filter in the Reducer.
I extended the WordCount v1.0 example from the 2.7 MapReduce
Tutorial with some additional functionality
and added the possibility to filter by the specific value of each
key - e.g. only output the key-value pairs where [[ value >
threshold ]].
Filtering Code in Reducer
#####################################
for (IntWritable val : values) {
sum += val.get();
}
if ( sum > threshold ) {
result.set(sum);
context.write(key, result);
}
#####################################
For threshold smaller any value the above code works as expected
and the output contains all key-value pairs.
If I increase the threshold to 1 some pairs are missing in the
output although the respective value would be larger than the
threshold.
I tried to work out the error myself, but I could not get it to
work as intended. I use the exact Tutorial setup with Oracle JDK 8
on a CentOS 7 machine.
As far as I understand the respective Iterable<...> in the
Reducer already contains all the observed values for a specific key.
Why is it possible that I am missing some of these key-value pairs
then? It only fails in very few cases. The input file is pretty
large - 250 MB -
so I also tried to increase the memory for the mapping and
reduction steps but it did not help ( tried a lot of different
stuff without success )
Maybe someone already experienced similar problems / is more
experienced than I am.
Thank you,
Peter
