Datamatics Global Services Ltd interview questions and answers

What is the error message that you would get if you try to assign “Null” to an integer variable ?

Editor — Thu, 22 Jul 2021 07:48:17 +0000

What is the error message that you would get if you try to assign “Null” to an integer variable ?

Error message : Cannot convert null to int because it is a non-nullable value type(or) INVALID use of NULL.

What is the advantages of VB.NET ?

Editor — Thu, 22 Jul 2021 07:43:21 +0000

VB.NET offers code execution that runs under the Common Language Runtime (CLR), resulting in robust, stable and secure applications. Both features of the .NET framework are eagerly obtainable in VB.NET.
VB.NET is object oriented. This is a major addition that VB6 and other earlier releases didn’t have.
The .NET framework comes with ADO.NET, which follows the disconnected paradigm, i.e. once the required records are fetched the connection no longer exists.
It also retrieves the records that are expected to be accessed in the immediate future.
This enhances Scalability of the application to a great extent.
VB.NET uses XML to transfer data between the various layers in the DNA Architecture i.e. data are passed as simple text strings.
Error handling has changed in VB.NET. A new Try-Catch-Finally block has been introduced to handle errors and exceptions as a unit, allowing appropriate action to be taken at the place the error occurred thus discouraging the use of ON ERROR GOTO statement. This again credits to the maintainability of the code.

What is the difference between vb and vb.net ?

Editor — Thu, 22 Jul 2021 07:41:06 +0000

VB	VB.NET
VB stands for Visual Basic. It is a high level programming language that is used for the fast development of Windows based programs.	VB.NET stands for Visual Basic Network Enabled Technology. It is one of the languages for the .NET framework by Microsoft. This language has been created specifically for VB developers. It belongs to the category of object oriented computer programming languages that is implemented on the .NET framework.
Interpreter based Language	Compiled language
VB Runtime	Common Language Specification
This type of language is not safe.	This language is safe compared to visual basic.
Multithreaded applications Cannot be developed.	Multithreaded applications Can be developed.
Data is handled using DAO protocol, then RDO, followed by ADO (ActiveX Data Objects)	Data is handled using ADO.net
An object based language.	A true object oriented language.
Most of the parameters passed by reference.	Parameters passing by Default value.
Objects support default property	Objects does not support default property
Replaced by elements in Collection QBColor, RGB DateAdd, DateDiff, DatePart, DateSerial, DateValue, TimeSerial, TimeValue	System.Collection System.Drawing.Color Replaced by elements in System.DateTime
End Type structure can be used in declare function.	Declared using the Structure…End Structure construct.

What is the difference between sqoop and pig ?

Editor — Thu, 22 Jul 2021 06:59:29 +0000

Pig:

Pig is a platform for managing large data.
It uses high level programming to analyse the data.
The programming is done using the language pig latin.
It is simple and highly specific.
The pig Metastore stores all info about the tables. And we can execute spark sql queries because spark can interact with pig Metastore

Sqoop:

Sqoop is a simple tool used for transferring large amount of data.
It is used for transferring data from hadoop to relational database.
sqoop can import data from Oracle,MYSQL,SQl.
Sqoop metastore is a tool for using hosts in a shared metadata repository. Multiple users and remote users execute saved jobs in metastore.

What is staging table in sqoop ?

Editor — Thu, 22 Jul 2021 06:53:48 +0000

Staging table in sqoop:

Staging table is used to stage the exported data.
Sqoop breaks down method into multiple transactions. A failing job may create partial knowledge.
This could result in job failing because it could cause duplication of data or even collision while insertion.
Staging tables are simple database tables that contain business details.
Staging table acts as an auxiliary table that’s used to transferred data.
Sqoop breaks down export method into multiple transactions, it’s possible that a failing export job may lead to partial data being committed to the database

What is update command in sqoop ?

Editor — Thu, 22 Jul 2021 06:52:07 +0000

Update command in sqoop:

There are two approaches to update in sqoop.
- The records inserted are to be added to the target table.
- The sqoop provides an update mode by providing “update-key ” command.
This command is used to generate the SQl update statement.
If the value in column 1 matches the data is updated else the data is inserted into the table.
This technique is also refered to as upsert where the default action is update but insertion takes place when matching data is not available.

 
$ sqoop export (Generic Arguments)
  --table target-relational-table 
  --update-key column1
  --export-dir /user/my-hdfs-file
  ...
Generates => UPDATE target-relational-table SET
                    column2=1000,column3=2000
		          WHERE column1=100;

What is the use of sqoop ?

Editor — Thu, 22 Jul 2021 06:49:42 +0000

Sqoop uses:

Sqoop is a simple tool that is used for moving data.
It is generally used move data from non hadoop data stores.
These non hadoop data stores are the relational databases and data warehouses .
Sqoop allows the users to specify the target (i.e) the place where the data is to be moved inside of hadoop from relational databases like Oracle,Teredata.
Data ingestion is important in any big data project because the volume of data is generally in petabytes or exabytes.
Hadoop Sqoop and Hadoop Flume are the two tools in Hadoop which is used to gather data from different sources and load them into HDFS.

What is sqoop metastore ?

Editor — Thu, 22 Jul 2021 06:47:16 +0000

Sqoop Metastore:

Sqoop metastore is an internally implemented database that can hold the definition of a given job.
It includes details like which database,which table,which approach,what query to extract from,what target to write to and so on.
Consider an array of SQL databases that have the same structure, but are partitioned by for performance reasons.
Thus we have the same sqoop job running against multiple database instances at the same time, all unified at a single table in Hadoop.
In order to get parallelization, we generate a job that manages the Sqoop sub-workflows. This results in 500 distinct sqoop jobs.
Metastore is used to handle these complexities.

What is sqoop ?

Editor — Thu, 22 Jul 2021 06:22:24 +0000

Sqoop:

Apache Sqoop is efficiently transferring data between Relational databases and Apache Hadoop.
It is used to import data from relational databases such as MySQL, Oracle to Hadoop HDFS, and export from Hadoop file system to relational databases.
It improves the efficiency of data analysis by combining structured data and unstructured data.
Sqoop stands for SQL for Hadoop.SQL + HADOOP =SQOOP

What is the difference between apache mahout and Prediction.io ?

Editor — Tue, 20 Jul 2021 03:21:23 +0000

Difference between Prediction.io and apache mahout

Apache mahout	Prediction.io
FEATURES: The three components of Mahout are an environment for building scalable algorithms,many new Scala + Spark and H2O (Apache Flink in progress) algorithms, and Mahout’s mature Hadoop MapReduce algorithms.	FEATURES: The Prediction.io supports event collection, evaluation, deployment of algorithms, querying predictive results via REST APIs.
PROGRAMMING LANGUAGES: Java, Python, Ruby	PROGRAMMING LANGUAGES: Java
SOURCE TYPE: Open	SOURCE TYPE: Open
Individual can create analytics apps with Mahout, if you want the apps as an API or as a server, individual needs something like Prediction.IO	Prediction.io wants an algorithm layer; it comes with Apache Spark as well as Stanford NLP, but individual also can use Mahout.

What is the difference between Cloudera Oryx and Apache Mahout ?

Editor — Tue, 20 Jul 2021 03:20:00 +0000

Differences between Cloudera Oryx and Apache Mahout

There are 3 broad things an operational ML system needs to do eventually
- Build models at scale, offline
- Update models in near real time
- Query models in real time
Most of the tools like Mahout or MLLib do building models at scale only.

Oryx tries to do all 3, and is not doing building model.
Therefore it is really intended as a complement to any Hadoop-based model build system.
As a result it is MapReduce based for model building and implemented algorithms instead of using Mahout to improve on perceived problems.
The project which is open source, is more designed as 3 complete apps rather than a platform for extension.
It only implements
- ALS for recommendation
- Kmeans for clustering
- Random decision forests for classification and regression
The major difference is fewer algorithms but complete apps including incremental update and serving. It is not the algorithms that are really the difference since Oryx is not a new library.
The next version is built on Spark and Kafka then becomes more of generic lambda architecture for ML that happens to have entire apps too.
It is kind of Summing bird for ML on Spark. It has no algorithms implementations at all, not now. Therefore it is even more different from Mahout or MLLib.

What is the difference between Apache Mahout and Spark MLLib ?

Editor — Tue, 20 Jul 2021 03:18:20 +0000

Differences between Apache Mahout and Spark MLLib:

Apache Mahout is a multi-backend capable high level system with implementations of some scalable algorithms.
These fundamentally include large-scale matrix decomposition and recommendation algorithms, yet any linear algebra based issue can be attacked with Mahout.
Efficient implementation is likely at this point to require improvement of the current optimizer (which is relatively easy to do), but when the optimizer is able to simplify the program, the results are quite dramatic.
Mahout also supports both Spark and H2O back-ends while MLLib is bound only to Spark.
If Spark manages to dominate all other possible back-ends (such as H2O, Julia or many others) then it is likely that MLLib will do as well as Mahout on performance.
On the other hand, with back ends that have super high performance specialized capabilities, Mahout will give you port programs to utilize these capabilities very efficiently.
MLLib is new and has yet to really hit its stride while Mahout is older and has belongings from the earlier period.
These to characteristics are opposite sides of the similar coin. Mahout focuses on algorithms for which there is a wide-spread need for scalable algorithms. MLLib is considerably more liberal with what is gotten.

Mahout and MLLib both have a typical execution engine.
Apache Mahout focuses on machine learning and have a rich set of algorithms, while MLLib only adopt various develop and basic algorithms.

What is pre-requisites for contributing to Apache Mahout ?

Editor — Tue, 20 Jul 2021 03:16:51 +0000

Pre-requisites for contributing to Apache Mahout:

Apache Mahout is open project. There are lots of new things happening in the project lately so a variety of skills are useful.
If you have a bit of background in machine learning or math or Spark or Scala, then your contributions would be quite welcoming.
Even if you just would like to work through and correct some of the tutorials that might have gotten a bit out of date, your contributions would be very welcoming.

How is 0xdata’s H2O different from Apache Mahout ?

Editor — Tue, 20 Jul 2021 03:15:13 +0000

0xdata’s H2O different from Apache Mahout:

By using H2O, you can use several of R, REST/JSON. For Example curl/bash, GUI browser, Scala or Java.
The H2O algorithms are usually 100x to 1000x faster than current Map/Reduce-based Mahout (but Mahout is working hard to port itself to both Spark and H2O).
H2O has some algorithms implemented:
1. Deep Learning / Neural Nets
2. Random Forest
3. Gradient Boosted Method
4. Generalized Linear Modelling including Logistic, Regression, Poisson, Gamma
5. PCA
6. KMeans (KMeans++, KMeans||, K-modes)
7. Naive Bayes
8. General Data Munging any standard R expression which auto-broadens to cover arrays also works the same in H2O.

What is the difference between GraphLab and Mahout ?

Editor — Tue, 20 Jul 2021 03:13:48 +0000

Difference between graphlab and mahout:

Mahout	Graphlab
Mahout is a framework for machine learning and part of the Apache Foundation	Graphlab project takes a quite different approach to parallel collaborative filtering (more broadly, machine learning), and is primarily used by academic institutions.
Mahout has inherent Fault-tolerance	Graphlab does not have inherent Fault-tolerance
Mahout looks like a more polished product, especially as it relies on Hadoop for scalability and distribution.	Graphlab excells since it is built ground up for iterative algorithms such as those used in collaborative filtering.
The mahout framework comes in two approaches: Online where recommendations are computed on demand, typically on smaller datasets. Offline which utilise Apache Hadoop to achieve scalability.	Graphlab lacks a production-ready distribution framework.
For 50000 items, you need to have N machines with at least 28 GiB of memory for each, where N is the number of Hadoop nodes and hence 28 GiB of memory becomes an issue.	Costly performance penalties since runtime of each phase is decided by slowest machine.

How Mahout used with Python ?

Editor — Tue, 20 Jul 2021 02:48:20 +0000

Mahout is used with Python:

You should need to download and install the JPype package for python.The initial step is to set up JPype is determining the path to the dynamic library for the jvm ; on linux this will be a .so file and on windows it will be a .dll.
In python script, make a global variable with the path to this dll file.
Then we need to make sense how we have to set the classpath for mahout. The simplest way to do this is to edit script in “bin/mahout” to print out the classpath. Now include the code line “echo $CLASSPATH” to the script anywhere in the following comment “run it”.
Finally execute the script to print out the classpath. Now copy this output and paste into a variable in your python script.
Presently we can create a function to begin the jvm in python utilizing jype.

from jpype import *
jvm=None
def start_jpype():
global jvm
if (jvm is None):
cpopt="-Djava.class.path={cp}".format(cp=classpath)
startJVM(jvmlib,"-ea",cpopt)
jvm="started"

In the same way while reading or writing call the JPype function:

start_jpype()

What are the uses and applications of Mahout ?

Editor — Tue, 20 Jul 2021 02:45:34 +0000

Uses of mahout:

It uses the Apache Hadoop library to allow Mahout to scale efficiently in the cloud.
Mahout focus on real-world, practical use cases as opposed to bleeding-edge research or unproven techniques and offers quality documentation.
It used to produce scalable machine learning algorithm then to implements its machine learning techniques that are:
1. Recommendation
2. Clustering
3. Classification

Applications of Mahout:

Adobe, Facebook, LinkedIn, Foursquare, Twitter, and Yahoo use Mahout internally.
Foursquare helps you to find out the place, food and entertainment available in a particular area. It uses the recommender engine of Mahout.
Twitter may use Mahout for user interest modelling.
Yahoo uses Mahout for pattern mining.

What is Apache Mahout ?

Editor — Tue, 20 Jul 2021 02:43:50 +0000

Apache mahout:

An Apache Software Foundation project to create free implementations of distributed or else scalable machine learning algorithms under the Apache Software license that focused in the areas of collaborative filtering, classification and clustering.
Several implementations utilize the Apache Hadoop platform.

It gives Java libraries for general maths operations (like linear algebra framework, statistics and data scientists) and primal Java collections.
Mahout is a work in advancement; much number of implemented algorithms has developed rapidly, however various algorithms are still missing.
Apache Mahout contains three major features:
- It gives simple and extensible programming environment then framework for building versatile algorithms.
- A wide variety of premade algorithms for Scala + Apache Spark, Apache Flink, H2O.
- Samsara, a vector math experimentation environment with R-like syntax which works at scale.

What is DITA ?

Editor — Mon, 19 Jul 2021 10:48:55 +0000

What is DITA ?

Darwin Information Typing Architecture (DITA) is the most ideal approach to be brilliant about composition and distributing your business content.
DITA is an open standard that portrays the engineering for making and overseeing data that isolates the substance from the arranging, takes into account a progressively streamlined substance creation process, and opens up the potential outcomes of acquainting less difficult methods for distributing with new advancements, as for cell phones. IBM, which created DITA initially, characterizes DITA as pursues:
The Darwin Information Typing Architecture (DITA) is a XML-based, end-to-end design for composing, creating, and conveying specialized data.
This engineering comprises of a lot of structure standards for making “data composed” modules at a subject dimension and for utilizing that content in conveyance modes, for example, online help and item bolster entryways on the Web.

Purpose of DITA

The information put away in your documentation has esteem.
What’s more, whatever has an incentive to the association can be treated as an advantage. Making and afterward leaving that data inside a Word or PowerPoint record seriously constrains what you can do with it, and whatever you can do, you need to utilize manual, kludge approaches to do it.
Making records with conventional instruments in static documents is a wasteful method for composing, refreshing, sharing, and dealing with your data.
DITA is a general methodology that illuminates that wastefulness.
DITA emphatically influences your substance in three principle ways;
It streamlines your substance creation process expands the nature of your substance by institutionalizing it enables you to use your substance in a wide range of ways (reusing it, distributing to numerous configurations, deciphering it effectively)
Despite the fact that there are numerous advantages to DITA, everything comes down to a certain something: being proficient with your substance so you can spare time and cash.

What DITA Is Not

DITA is certainly not a specific device. A wide range of apparatuses enable you to creator in DITA. Truth be told, choosing your instrument set is a piece of the procedure of DITA selection.
DITA isn’t a layout, in spite of the fact that writers regularly use formats to make it considerably quicker and less demanding to compose.
DITA isn’t a style direct, despite the fact that creators surely advantage from one, with or without DITA content.

Why XML ?

Try not to give the XML a chance to part of DITA alarm you.
It’s simply the engineering underneath your substance. Each bit of substance gets put away inside labels-titles, sections, requested records-whatever you have to arrange your substance into a characterized set of theme types.
DITA has a lot of guidelines that state what labels are permitted where, which gives you institutionalization of your substance.
DITA XML at last completes three things.
DITA XML composes your substance into points.
Not all XML does this, but rather DITA has a center arrangement of theme types so you can put the correct kind of data in the correct subject sort, bringing about exceptionally usable substance.
Consider subjects and even the XML inside themes like Lego® squares. You use them in different approaches to fabricate what you require. At last, they meet up to make more than the individual parts.
XML isolates content from configuration, making it compact and adaptable. Your words and your arrangement are never again consolidated, which implies they can be overseen and refreshed autonomously.
For instance, if your marking changes and you have to refresh the text dimension, shading, and style in the entirety of your archives, this will be a focal, once change for any substance put away without organization (in XML).
XML enables the substance to be changed into numerous different arrangements. A great many people creator in XML and after that distribute to PDF, HTML, and either portable or ePub.
It’s additionally conceivable to distribute to places you wouldn’t anticipate, similar to Open Office, Excel, and PowerPoint. You’re constrained just by your creative energy.

What is the difference between Angularjs and Polymer ?

Editor — Sun, 11 Jul 2021 13:09:56 +0000

Difference between Angularjs and Polymer

Angularjs	Polymer
Angular is a framework written using javascript and is made for building single-page web applications.	Polymer’s webcomponents.js is a library that contains several polyfills for various W3C APIs that fall under the Web Components umbrella.
Angular’s data binding and dependency injection eliminate much of the code writing.It happens within the browser, making it an ideal partner with any server technology.	Polymer is a library that aims to use (and show how to use) Web Components.Its foundation is Custom Elements (e.g. everything you build is a web component) and it evolves as the web evolves.