Home | About | Sematext search-lucene.com search-hadoop.com
 Search Hadoop and all its subprojects:

Switch to Threaded View
MapReduce, mail # user - Please help on providing correct answers


Copy link to this message
-
Re: Please help on providing correct answers
Michael Segel 2012-11-07, 17:27
Ok...
Where are you pulling these questions from?

Seriously.
On Nov 7, 2012, at 11:21 AM, Ramasubramanian Narayanan <[EMAIL PROTECTED]> wrote:

> Hi,
>
>    I came across the following question in some sites and the answer that they provided seems to be wrong according to me... I might be wrong... Can some one help on confirming the right answers for these 11 questions pls.. appreciate the explanation if you could able to provide...
>
> *******************************************************************************
> You are running a job that will process a single InputSplit on a cluster which has no other jobs
> currently running. Each node has an equal number of open Map slots. On which node will Hadoop
> first attempt to run the Map task?
> A. The node with the most memory
> B. The node with the lowest system load
> C. The node on which this InputSplit is stored
> D. The node with the most free local disk space
>
> My Answer            : C
> Answer Given in site : A
>
> *******************************************************************************
> What is a Writable?
> A. Writable is an interface that all keys and values in MapReduce must implement. Classes implementing this interface must implement methods forserializingand deserializing themselves.
> B. Writable is an abstract class that all keys and values in MapReduce must extend. Classes extending this abstract base class must implementmethods for serializing and deserializingthemselves
> C. Writable is an interface that all keys, but not values, in MapReduce must implement. Classes implementing this interface mustimplementmethods for serializing and deserializing themselves.
> D. Writable is an abstract class that all keys, but not values, in MapReduce must extend. Classes extending this abstract base class must implementmethods for serializing and deserializing themselves.
>
> My Answer            : A
> Answer Given in site : B
>
> *******************************************************************************
>
> You write a MapReduce job to process 100 files in HDFS. Your MapReducc algorithm uses
> TextInputFormat and the IdentityReducer: the mapper applies a regular expression over input
> values and emits key-value pairs with the key consisting of the matching text, and the value
> containing the filename and byte offset. Determine the difference between setting the number of
> reducers to zero.
> A. There is no differenceinoutput between the two settings.
> B. With zero reducers, no reducer runs and the job throws an exception. With one reducer,
> instances of matching patterns are stored in a single file on HDFS.
> C. With zero reducers, all instances of matching patterns are gathered together in one file on
> HDFS. With one reducer, instances ofmatching patternsstored in multiple files on HDFS.
> D. With zero reducers, instances of matching patterns are stored in multiple files on HDFS. With
> one reducer, all instances of matching patterns aregathered together in one file on HDFS.
>
> My Answer            : D
> Answer Given in site : C
>
> *******************************************************************************
>
> During the standard sort and shuffle phase of MapReduce, keys and values are passed to
> reducers. Which of the following is true?
> A. Keys are presented to a reducerin sorted order; values foragiven key are not sorted.
> B. Keys are presented to a reducer in soiled order; values for a given key are sorted in ascending
> order.
> C. Keys are presented to a reducer in random order; values for a given key are not sorted.
> D. Keys are presented to a reducer in random order; values for a given key are sorted in
> ascending order.
>
> My Answer            : A
> Answer Given in site : D
>
> *******************************************************************************
>
> Which statement best describes the data path of intermediate key-value pairs (i.e., output of the
> mappers)?
> A. Intermediate key-value pairs are written to HDFS. Reducers read the intermediate data from