Hi,
I have a Hadoop app in which each mapper generates a floating point result
which I output, along with a single LongWritable key, set to zero.
My reducer receives a set of the results from which I need to select the
minimum. I output the minimum as the result, again as a zero-valued key along
with a floating point value (the minimum).
According to my understanding, I ought to be able to use my reducer as a
combiner. However, when I do this, my final reducer doesn’t seem to get passed
any values at all, although the reducers running as combiners are being called
and seem to be producing the correct output.
Note that I have deliberately not done anything ‘clever’, such a defining
custom partitioners or other customisation.
Any help most appreciated,
Andy Doddington
