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Posted to user@spark.apache.org by Zhiliang Zhu <zc...@yahoo.com.INVALID> on 2015/12/08 10:23:16 UTC
what's the way to access the last element from another partition
In some given partition, it seems difficult to access the last element in another partition, but in my application I need do as that.Exactly how to do it ?
Just by repartition /shuffle the rdd into one partition and get the specific "last" element ? Will this will change the previous order among the elements, and will it also not work ?
Thanks very much in advance!
On Monday, December 7, 2015 11:32 AM, Zhiliang Zhu <zc...@yahoo.com> wrote:
On Monday, December 7, 2015 10:37 AM, DB Tsai <db...@dbtsai.com> wrote:
Only beginning and ending part of data. The rest in the partition can
be compared without shuffle.
Would you help write a few pseudo-code about it...It seems that there is not shuffle related API , or repartition ?
Thanks a lot in advance!
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Sincerely,
DB Tsai
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Web: https://www.dbtsai.com
PGP Key ID: 0xAF08DF8D
On Sun, Dec 6, 2015 at 6:27 PM, Zhiliang Zhu <zc...@yahoo.com> wrote:
>
>
>
>
> On Saturday, December 5, 2015 3:00 PM, DB Tsai <db...@dbtsai.com> wrote:
>
>
> This is tricky. You need to shuffle the ending and beginning elements
> using mapPartitionWithIndex.
>
>
> Does this mean that I need to shuffle the all elements in different
> partitions into one partition, then compare them by way of any two adjacent
> elements?
> It seems good, if it is like that.
>
> One more issue, will it loss parallelism since there become only one
> partition ...
>
> Thanks very much in advance!
>
>
>
>
>
>
> Sincerely,
>
> DB Tsai
> ----------------------------------------------------------
> Web: https://www.dbtsai.com
> PGP Key ID: 0xAF08DF8D
>
>
> On Fri, Dec 4, 2015 at 10:30 PM, Zhiliang Zhu <zc...@yahoo.com> wrote:
>> Hi All,
>>
>> I would like to compare any two adjacent elements in one given rdd, just
>> as
>> the single machine code part:
>>
>> int a[N] = {...};
>> for (int i=0; i < N - 1; ++i) {
>> compareFun(a[i], a[i+1]);
>> }
>> ...
>>
>> mapPartitions may work for some situations, however, it could not compare
>> elements in different partitions.
>> foreach also seems not work.
>>
>> Thanks,
>> Zhiliang
>
>>
>>
>
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