Re: Read once input data?

Posted by Saliya Ekanayake on
URL: http://deprecated-apache-flink-user-mailing-list-archive.369.s1.nabble.com/Read-once-input-data-tp4932p4950.html

Fabian,

I've a quick follow-up question on what you suggested. When streaming the same data through different maps, were you implying that everything goes as single job in Flink, so data read happens only once? 

Thanks,

Saliya

On Mon, Feb 15, 2016 at 3:58 PM, Fabian Hueske <[hidden email]> wrote:

It is not possible to "pin" data sets in memory, yet.

However, you can stream the same data set through two different mappers at the same time.

For instance you can have a job like:

                 /---> Map 1 --> SInk1

Source --<
                 \---> Map 2 --> SInk2

and execute it at once.

For that you define you data flow and call execute once after all sinks have been created.

Best, Fabian

2016-02-15 21:32 GMT+01:00 Saliya Ekanayake <[hidden email]>:

Fabian,

count() was just an example. What I would like to do is say run two map operations on the dataset (ds). Each map will have it's own reduction, so is there a way to avoid creating two jobs for such scenario?

The reason is, reading these binary matrices are expensive. In our current MPI implementation, I am using memory maps for faster loading and reuse.

Thank you,

Saliya

On Mon, Feb 15, 2016 at 3:15 PM, Fabian Hueske <[hidden email]> wrote:

Hi,

it looks like you are executing two distinct Flink jobs.
DataSet.count() triggers the execution of a new job. If you have an execute() call in your program, this will lead to two Flink jobs being executed.

It is not possible to share state among these jobs.

Maybe you should add a custom count implementation (using a ReduceFunction) which is executed in the same program as the other ReduceFunction.

Best, Fabian

2016-02-15 21:05 GMT+01:00 Saliya Ekanayake <[hidden email]>:

Hi,

I see that an InputFormat's open() and nextRecord() methods get called for each terminal operation on a given dataset using that particular InputFormat. Is it possible to avoid this - possibly using some caching technique in Flink?

For example, I've some code like below and I see for both the last two statements (reduce() and count()) the above methods in the input format get called. Btw. this is a custom input format I wrote to represent a binary matrix stored as Short values.

ShortMatrixInputFormat smif = new ShortMatrixInputFormat();

DataSet<Short[]> ds = env.createInput(smif, BasicArrayTypeInfo.SHORT_ARRAY_TYPE_INFO);

MapOperator<Short[], DoubleStatistics> op = ds.map(...)
op.reduce(...)
op.count(...)

Thank you,

Saliya

--

Saliya Ekanayake

Ph.D. Candidate | Research Assistant

School of Informatics and Computing | Digital Science Center

Indiana University, Bloomington
Cell <a href="tel:[phone]" value="[phone]" target="_blank">812-391-4914
http://saliya.org

--

Saliya Ekanayake

Ph.D. Candidate | Research Assistant

School of Informatics and Computing | Digital Science Center

Indiana University, Bloomington
Cell <a href="tel:[phone]" value="[phone]" target="_blank">812-391-4914
http://saliya.org

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