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From Ufuk Celebi <...@apache.org>
Subject Re: reduce error
Date Fri, 16 Oct 2015 19:59:31 GMT
Hey Michele! Sorry for the long delay on this. Can you share the code and
data? The easiest thing to reproduce is to actually run the code with the
data. It will also help a lot when trying to fix the problem. If you can't
share publicly feel free to mail me at uce at apache org.

– Ufuk

On Thu, Oct 8, 2015 at 9:53 AM, Michele Bertoni <
michele1.bertoni@mail.polimi.it> wrote:

> Hi everybody, I am facing a very strange problem
> Sometimes when I run my program one line of the result is totally wrong
> and if I repeat the execution with same input it can change
>
>
> The algorithm takes two dataset and execute something like a left outer
> join where
> if there is a match
>  - it increments a counter on the left tuple
>  - add some values of the right tuple to an array of the left tuple
> in the end it outputs the left value with the final counter and list of
> values (printer lines A and B)
>
> then there is a group reduce phase that merge element from different
> groups (there can be but not always)
>
> finally there is a map that applies some custom functions (printer lines C
> and D)
>
>
>
>
> my problem is that from printer B and C the data actually change with no
> reason
>
> in example in line B counter is 7 in line C it is 1.82E9, it always goes
> to very high numbers from E9 to E18 while it is expected to be smaller than
> 20
> moreover the array of extradata goes to null
>
>
> what i found is that
> it never happened if the reduce is actually executed (when there are many
> elements in a group) but only when there is one element per group (so the
> reduce should not change data in a tuple)
> I am running on a small dataset 60k lines and if it happens, it always
> happens in the same line of the input
> if I change dataset it happens on an other line but always on the same for
> that dataset
>
> By now it always happened in only one line for each dataset (I am using a
> local environment with parallelism 1)
>
>
>
>
> I tried to changed the reduce with a reducegroup and inside the
> reducegroup a pure scala reduce, this worked perfectly (by now)
> I also added two groupby and reducegroup block (that take the line at put
> it in output) before and after the groupby-reduce, in both cases i faced no
> problem at all
> it only seems to appear when using the group and reduce
>
> any idea on what could be the problem? I am getting mad on it
>
>
> thanks for help
>
>
>
> this is the code I use (there are a lot of println for debugging)
>
> groupedRef // expID, bin, chromosome
>   .coGroup(groupedExp).where(1,3,5).equalTo(2,1,3){
>   (references : Iterator[(Long, Long, Int, Int, Long, String, Long, Long, Char, Array[GValue],
Long)], experiments : Iterator[(Int, Int, Long, String, Long, Long, Char, Array[GValue])],
out : Collector[(Long, String, Long, Long, Char, Array[GValue], Array[List[GValue]], Int,
Long)]) => {
>     val refCollected : List[PartialResult] = references.map((r) => (new PartialResult(r,
0, extraData ))).toList
>     for(e <- experiments){
>       for(r <- refCollected){
>         if( /* complex clause not important */ ) {
>           r.count += 1
>           r.extra = r.extra :+ e._8.foldLeft(new Array[List[GValue]](0))((z : Array[List[GValue]],
v : GValue) => z :+ List(v))
>         }
>       }
>     }
>
>
>
>     refCollected.map((pr) => {
>
>       if(pr.binnedRegion._1.equals(7773719163500064339L) && pr.binnedRegion._7.equals(4860L)
&& pr.binnedRegion._8.equals(5324L)){
>         println("-A--------------------------------------- " + pr.toString())
>       }
>       val res = (pr.binnedRegion._1, pr.binnedRegion._6, pr.binnedRegion._7, pr.binnedRegion._8,
pr.binnedRegion._9, pr.binnedRegion._10, pr.extra.reduce((a,b) => a.zip(b).map((p) =>
p._1 ++ p._2)), pr.count, pr.binnedRegion._11)
>
>       if(res._1.equals(7773719163500064339L) && res._3.equals(4860L) &&
res._4.equals(5324L)){
>         println("-B--------------------------------------- " + (res._1, res._2, res._3,
res._4, res._5, res._6.mkString((" - ")), res._7.mkString(" - "), res._8, res._9 ))
>       }
>
>       out.collect(res)
>     })
>
>
>   }
> }
>
> val aggregationResult : DataSet[(Long, String, Long, Long, Char, Array[GValue])] =
> coGroupResult
>
> //-----------------------------------------------------------------
>
> .groupBy(8)
> //reduce phase
> //concatenation of extra data
> .reduce(
>   (r1,r2) => {
>     val out = (r1._1, r1._2, r1._3, r1._4, r1._5, r1._6,
>       r1._7
>         .zip(r2._7)
>         .map((a) => a._1 ++ a._2),
>       r1._8 + r2._8, r1._9)
>
>     out
>
>   }
> )
>
>
> //————————————————————————————————
>
> .map((l : (Long, String, Long, Long, Char, Array[GValue], Array[List[GValue]], Int, Long))
=> {
>
>
>     if(l._1.equals(7773719163500064339L) && l._3.equals(4860L) && l._4.equals(5324L)){
>       println("-C--------------------------------------- " + (l._1, l._2, l._3, l._4,
l._5, l._6.mkString((" - ")), l._7.mkString(" - "), l._8, l._9 ))
>     }
>
>     val out =
>       //something else that is working good
>
>     if(out._1.equals(7773719163500064339L) && out._3.equals(4860L) &&
out._4.equals(5324L)){
>       println("-D--------------------------------------- " + (out._1, out._2, out._3,
out._4, out._5, out._6.mkString(" - ")))
>     }
>
>     out
> })
>
>
>
>

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