GPSS Developer Hiring Guide

Hiring Guide for GPSS Engineers

Ask the right questions to secure the right GPSS talent among an increasingly shrinking pool of talent.

The General Purpose Simulation System (GPSS) is a high-level, discrete simulation language developed by IBM in the 1960s. It was designed to model complex systems, such as those found in business and industry, by representing them as a series of transactions. GPSS allows users to create models of systems and processes to analyze their performance and efficiency. The language has been widely used in operations research, manufacturing, telecommunications, and transportation planning. Its development marked a significant advancement in computer programming languages and simulation methodologies.

First 20 minutes

General GPSS knowledge and experience

The next 20 minutes of the interview should attempt to focus more specifically on the development questions used, and the level of depth and skill the engineer possesses.

What is the function of the ADVANCE block in GPSS?

The ADVANCE block is used in GPSS to represent a delay in the system. It holds a transaction for a specified amount of time before allowing it to proceed to the next block.

How would you use the GENERATE block in GPSS?

The GENERATE block in GPSS is used to create transactions at specified time intervals. The time between arrivals can be either fixed or randomly generated according to a specified distribution.

Describe the difference between deterministic and stochastic models in GPSS.

Deterministic models in GPSS have outcomes that are entirely determined by the parameter values and initial conditions, while stochastic models incorporate randomness in their inputs, leading to a range of possible outcomes.

What is the purpose of using transactions in GPSS?

Transactions are used in GPSS to represent individual entities moving through the system. They carry attributes that can be used to control their behavior and can be created, altered, and destroyed as they move through the model.

How would you describe the basic structure of a GPSS model?

A GPSS model is structured into blocks, each representing a specific aspect of the system being modeled. Blocks are connected in a network to represent the flow of transactions through the system. Each block has its own parameters and functions.

The hiring guide has been successfully sent to your email address.
Oops! Something went wrong while submitting the form.

What youre looking for early-on

Has the candidate demonstrated a strong attention to detail?

This is essential in programming and development roles to minimize errors and ensure high-quality work.

Has the candidate shown an ability to learn new technologies and adapt to changes?

This is important as technology and programming languages are constantly evolving.

Is the candidate able to communicate effectively and work well in a team?

Communication and teamwork are key in any development role to ensure projects run smoothly.

Can the candidate demonstrate experience with other programming languages, especially those that are often used alongside GPSS?

This shows versatility and a broader understanding of programming, which can be invaluable in GPSS development.

How well does the candidate understand and apply problem-solving skills?

GPSS development often involves complex problem-solving and the candidate should be able to demonstrate this ability.

Does the candidate have a strong understanding of GPSS language and its applications?

This is crucial as the candidate will be required to develop and maintain GPSS-based systems.

Next 20 minutes

Specific GPSS development questions

The next 20 minutes of the interview should attempt to focus more specifically on the development questions used, and the level of depth and skill the engineer possesses.

How would you model a resource with limited capacity in GPSS?

A resource with limited capacity can be modeled in GPSS using the SEIZE and RELEASE blocks. The SEIZE block is used to represent a transaction claiming a resource, and the RELEASE block is used to represent the resource being freed.

What is the function of the GATHER block in GPSS?

The GATHER block in GPSS is used to collect transactions that have been split. It waits until all copies of a transaction have arrived before allowing the original transaction to proceed.

How would you use the SPLIT block in GPSS?

The SPLIT block in GPSS is used to create copies of a transaction. Each copy can then be directed to a different part of the model, allowing for parallel processing.

What is the purpose of the TEST block in GPSS?

The TEST block in GPSS is used to make decisions based on the attributes of a transaction. It can direct a transaction to different blocks depending on the outcome of the test.

How would you model a queue in GPSS?

A queue in GPSS can be modeled using a combination of the QUEUE, DEPART, and SEIZE/RELEASE blocks. The QUEUE block is used to hold transactions until a server is available, the DEPART block removes transactions from the queue, and the SEIZE/RELEASE blocks are used to represent the server.

The hiring guide has been successfully sent to your email address.
Oops! Something went wrong while submitting the form.

The ideal back-end app developer

What you’re looking to see on the GPSS engineer at this point.

At this point, a skilled GPSS engineer should demonstrate strong problem-solving skills, proficiency in GPSS language and simulation modeling. They should show an understanding of system analysis and design principles. Red flags include lack of practical experience, inability to explain complex concepts simply, or unfamiliarity with current trends and technologies in GPSS engineering.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with GPSS.

What does this simple GPSS code do?

GENERATE 5,2
TERMINATE 1

This code generates a transaction every 5 units of time, with a standard deviation of 2 units. Then it terminates the transaction after 1 unit of time.

What does this GPSS code do?

GENERATE 10,3
QUEUE LINE
DEPART LINE
TERMINATE 1

This code generates a transaction every 10 units of time, with a standard deviation of 3 units. The transaction then enters a queue named LINE, leaves the queue, and then terminates after 1 unit of time.

What will be the output of this GPSS code?

GENERATE 5,2
QUEUE LINE
DEPART LINE
TERMINATE 1
START 100

This code will generate a transaction every 5 units of time, with a standard deviation of 2 units. The transaction then enters a queue named LINE, leaves the queue, and then terminates after 1 unit of time. The simulation will run for 100 units of time.

What does this GPSS code do?

GENERATE 5,2
ADVANCE 7,1
TERMINATE 1

This code generates a transaction every 5 units of time, with a standard deviation of 2 units. The transaction then advances 7 units of time, with a standard deviation of 1 unit, and then terminates after 1 unit of time.

What will be the output of this GPSS code?

GENERATE 5,2
SEIZE MACHINE
ADVANCE 7,1
RELEASE MACHINE
TERMINATE 1
START 100

This code generates a transaction every 5 units of time, with a standard deviation of 2 units. The transaction then seizes a facility named MACHINE, advances 7 units of time, with a standard deviation of 1 unit, releases the facility, and then terminates after 1 unit of time. The simulation will run for 100 units of time.

What does this GPSS code do?

GENERATE 5,2
SEIZE MACHINE
ADVANCE 7,1
RELEASE MACHINE
TERMINATE 1
START 100
GENERATE 10,3
QUEUE LINE
DEPART LINE
TERMINATE 1
START 200

This code generates a transaction every 5 units of time, with a standard deviation of 2 units. The transaction then seizes a facility named MACHINE, advances 7 units of time, with a standard deviation of 1 unit, releases the facility, and then terminates after 1 unit of time. The simulation will run for 100 units of time. Then it generates a new transaction every 10 units of time, with a standard deviation of 3 units. The transaction then enters a queue named LINE, leaves the queue, and then terminates after 1 unit of time. The simulation will run for 200 units of time.

Wrap-up questions

Final candidate for GPSS role questions

The final few interview questions for a GPSS candidate should typically focus on a combination of technical skills, personal goals, growth potential, team dynamics, and company culture.

Describe the difference between a warm-up period and a steady state in GPSS simulations.

The warm-up period in a GPSS simulation is the initial period during which the system is settling into its typical behavior. The steady state is the period during which the system's behavior is stable and can be used for analysis.

How would you optimize a GPSS model?

Optimizing a GPSS model involves adjusting its parameters to improve its performance. This can involve changing the model's structure, adjusting the values of parameters, or using optimization techniques such as genetic algorithms or gradient descent.

How would you use the TRANSFER block in GPSS?

The TRANSFER block in GPSS is used to direct a transaction to a different part of the model based on a condition or a probability. It can be used to represent decisions or random events.

What is the purpose of the SAVEVALUE block in GPSS?

The SAVEVALUE block in GPSS is used to store a value for later use. This can be a value calculated during the simulation, or it can be a value that is input into the model.

How would you validate a GPSS model?

Validating a GPSS model involves comparing its output with real-world data or with the output of a trusted model. This can involve statistical tests, visual inspection of output graphs, or other techniques.

The hiring guide has been successfully sent to your email address.
Oops! Something went wrong while submitting the form.

GPSS application related

Product Perfect's GPSS development capabilities

Beyond hiring for your GPSS engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in GPSS projects, and can engage in multiple capacities.

GPSS Consultive assessments

Custom GPSS development projects

Hiring guides

Hiring guides at a higher level of coverage

Zooming out above a specific programming language, these other hiring guides may be helpful.

Back-end App Developer

Front-end Web Developer

Full Stack Developer (Java)

Full Stack Developer (.Net)

Full Stack Developer (MEAN)

Full Stack Developer (MERN)

DevOps Engineer

Database Engineer (AzureSQL)

Database Engineer (Oracle)

Database Engineer (General)

Solution Architect (.NET)

Solution Architect (Java)

Solution Architect (Ruby)

Solution Architect (Python)

AI Engineer (Python)

Sr. AI Engineer (Python)

AI Strategist (Python)

Business Intelligence Engineer

Systems Analyst

Mainframe Developer (COBOL)

Mainframe Developer (General)