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PDL, or Perl Data Language, is a high-level programming language developed in the late 1980s for data manipulation and display. It was designed to extend the capabilities of Perl, a popular scripting language at the time. PDL provides advanced numerical and data manipulation abilities akin to those found in MATLAB or NumPy. The language is particularly suited for scientific computing tasks, such as image processing and numerical analysis. Its development has been driven by an active open-source community with references available through CPAN (Comprehensive Perl Archive Network).

Ask the right questions secure the right PDL (Perl Data Language) talent among an increasingly shrinking pool of talent.

First 20 minutes

General PDL (Perl Data Language) app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in PDL (Perl Data Language) application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

What is the use of the PDL module in Perl?

The PDL module in Perl is used for numerical and scientific computing. It provides a high-level interface to the standard Perl data types, allowing for efficient manipulation of large numerical arrays.

How would you create a new PDL object?

You can create a new PDL object using the 'pdl' constructor, which takes a list of values as its argument. For example: my $p = pdl(1,2,3,4);

What are PDL threads?

PDL threads are a way of automatically iterating over one or more dimensions of a PDL data object. They allow for efficient vectorized operations on large data sets.

How would you read data from a file into a PDL object?

You can use the 'rcols' function to read data from a file into a PDL object. For example: my ($x,$y) = rcols('data.txt');

Describe the difference between PDL and standard Perl arrays.

PDL arrays are more memory-efficient and faster for numerical computations than standard Perl arrays. They also support automatic threading, which allows for efficient vectorized operations.

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What you’re looking for early on

Does the candidate have a strong understanding of Perl Data Language?

Has the candidate demonstrated problem-solving skills?

Is the candidate familiar with data manipulation and analysis using PDL?

Has the candidate shown the ability to work in a team?

Next 20 minutes

Specific PDL (Perl Data Language) development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

How would you perform element-wise operations on PDL objects?

You can use the overloaded arithmetic operators to perform element-wise operations on PDL objects. For example: my $z = $x + $y;

What are PDL slices?

PDL slices are a way of accessing a subset of a PDL data object. They allow for efficient manipulation of large data sets.

How would you create a PDL object from a Perl list?

You can use the 'pdl' constructor to create a PDL object from a Perl list. For example: my $p = pdl(@list);

Describe the difference between PDL's 'threading' and Perl's 'threading'.

PDL's threading refers to automatic iteration over data dimensions, allowing for efficient vectorized operations. Perl's threading, on the other hand, refers to the ability to run multiple threads of execution within a single program.

How would you handle missing data in a PDL object?

You can use the 'isbad' function to check for missing data in a PDL object, and the 'badflag' function to enable or disable the propagation of missing data.

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At this point, a skilled PDL (Perl Data Language) engineer should demonstrate strong problem-solving abilities, proficiency in PDL (Perl Data Language) programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with PDL (Perl Data Language).

What does the following PDL code do?
$a = pdl [[1,2,3],[4,5,6],[7,8,9]];
This code creates a 3x3 PDL object (similar to an array) with the values from 1 to 9.
What will be the output of the following PDL code?
$a = sequence(10);
print $a->at(5);
The code will print '5'. It creates a sequence of 10 numbers from 0 to 9 and then prints the value at index 5 which is 5.
What does the following PDL code do?
$a = pdl [[1,2,3],[4,5,6],[7,8,9]];
$b = $a->slice('1:2');
This code creates a 3x3 PDL object, then selects the second and third columns of this PDL object and assigns them to 'b'. The slice function in PDL is used for selecting a range of elements from an array.
What does the following PDL code do?
$a = pdl [[1,2,3],[4,5,6],[7,8,9]];
$a->thread(1);
This code creates a 3x3 PDL object and then threads over the second dimension of the PDL object. Threading in PDL is a way of applying an operation to higher-dimensional data by automatically looping over extra dimensions.

Wrap-up questions

Final candidate for PDL (Perl Data Language) Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle PDL (Perl Data Language) application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

What are PDL dimensions?

PDL dimensions are the size of the data object in each direction. For example, a 2D PDL object might have dimensions [3,4], representing 3 rows and 4 columns.

How would you reshape a PDL object?

You can use the 'reshape' function to change the dimensions of a PDL object. For example: my $q = $p->reshape(2,2);

Describe the difference between PDL's 'clump' and 'thread' functions.

The 'clump' function combines adjacent dimensions into a single dimension, while the 'thread' function allows for automatic iteration over one or more dimensions.

PDL (Perl Data Language) application related

Product Perfect's PDL (Perl Data Language) development capabilities

Beyond hiring for your PDL (Perl Data Language) engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in PDL (Perl Data Language) projects, and can engage in multiple capacities.

PDL (Perl Data Language) Consultive assessments

PDL (Perl Data Language) Application Conversion Assessment PDL (Perl Data Language) Application Integration Assessment PDL (Perl Data Language) Data & Database Integration Assessment

Custom PDL (Perl Data Language) development projects

Custom PDL (Perl Data Language) App Conversion PDL (Perl Data Language) Custom App Development Process App UI Design for PDL (Perl Data Language) Facelifts

Hiring guide for PDL (Perl Data Language) Engineers

PDL (Perl Data Language) Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

What you’re looking to see on the PDL (Perl Data Language) engineer at this point.

PDL (Perl Data Language) Consultive assessments

Custom PDL (Perl Data Language) development projects