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MapReduce, mail # user - Ant Colony Optimization for Travelling Salesman Problem in Hadoop


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Re: Ant Colony Optimization for Travelling Salesman Problem in Hadoop
Steve Lewis 2012-05-07, 15:17
Yes but it is the job of the InputFormat code to implement the behavior -
it is not necessary to do so and in other cases I choose to create more
mappers when the mapper has a lot of work

On Mon, May 7, 2012 at 7:54 AM, GUOJUN Zhu <[EMAIL PROTECTED]>wrote:

>
> We are using old API of 0.20.  I think when you set "mapred.reduce.tasks"
> with certain number N and use fileinputformat, the default behavior is that
> any file will be split into that number, N, each split smaller than the
> default block size. Of course, other restriction, such as
> "mapred.min.split.size" cannot be set too large (default is as small as
> possible I think).
>
> Zhu, Guojun
> Modeling Sr Graduate
> 571-3824370
> [EMAIL PROTECTED]
> Financial Engineering
> Freddie Mac
>
>
>     *sharat attupurath <[EMAIL PROTECTED]>*
>
>    05/05/2012 11:37 AM
>     Please respond to
> [EMAIL PROTECTED]
>
>   To
> <[EMAIL PROTECTED]>
> cc
>   Subject
> RE: Ant Colony Optimization for Travelling Salesman Problem in Hadoop
>
>
>
>
> Since the input files are very small, the default input formats in Hadoop
> all generate just a single InputSplit, so only a single map task is
> executed, and we wont have much parallelism.
>
> I was thinking of writing an InputFormat that would read the whole file as
> an InputSplit and replicate this input split n times (where n would be the
> number of ants in a single stage) so that we'll have n mappers.
> Also I want the input format to return the value as the adjacency matrix
> of the graph (calculating it from the coordinates in the input file).
>
> But I can't find a way to do this. Is it possible? Or is it better to just
> have the input as Text and create the adjacency matrix in the mappers?
>
> ------------------------------
> Date: Sat, 5 May 2012 08:20:34 -0700
> Subject: Re: Ant Colony Optimization for Travelling Salesman Problem in
> Hadoop
> From: [EMAIL PROTECTED]
> To: [EMAIL PROTECTED]
>
> yes - if you know how you can put it in distributed cache or if it is
> small put in as a String in the config or have all InputFormats read it
> from somewhere
>
> On Sat, May 5, 2012 at 8:08 AM, sharat attupurath <*[EMAIL PROTECTED]*<[EMAIL PROTECTED]>>
> wrote:
> I looked at both the files. in AbstractNShotInputFormat it is mentioned
> that this input format does not read from files. My input is in a text
> file. I want the whole file as a single record. So is it enough if i just
> copy the contents of the file and return it as a string from
> getValueFromIndex() ?
>
> ------------------------------
> Date: Fri, 4 May 2012 13:15:46 -0700
>
> Subject: Re: Ant Colony Optimization for Travelling Salesman Problem in
> Hadoop
> From: *[EMAIL PROTECTED]* <[EMAIL PROTECTED]>
> To: *[EMAIL PROTECTED]* <[EMAIL PROTECTED]>
>
> Look at NShotInputFormat
> call setNumberKeys to set the number of ants then
> change the method getValueFromIndex to return the text representing the
> original problem to each mapper -
> what happens in the second and third jobs is an exercise but the saved
> test needs to have pheremones and the original problem
>
>
> On Fri, May 4, 2012 at 9:54 AM, sharat attupurath <*[EMAIL PROTECTED]*<[EMAIL PROTECTED]>>
> wrote:
> Hi,
>
> Thanks a lot for the quick reply sir! We are new to Apache Hadoop and
> haven't yet understood it properly yet. Can you please elaborate on how we
> can have multiple stages of mapreduce jobs for combining the trails as you
> have mentioned?
>
> We have been trying to find out how to write a custom splitter and almost
> all online resources tell to subclass the FileInputFormat and write only a
> custom RecordReader? Will it be possible to generate our splits in that way?
>
> Regards
>
> Sharat
>
> ------------------------------
> Date: Fri, 4 May 2012 09:22:51 -0700
> Subject: Re: Ant Colony Optimization for Travelling Salesman Problem in
> Hadoop
> From: *[EMAIL PROTECTED]* <[EMAIL PROTECTED]>
Steven M. Lewis PhD
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