Hiring guide for Infer.NET Engineers

Infer.NET Developer Hiring Guide

Infer.NET is a framework for running Bayesian inference in graphical models. It was developed by Microsoft Research in Cambridge, UK and provides a range of model-based machine learning methods that are used in various fields such as information retrieval, bioinformatics, epidemiology, vision, and many others. Infer.NET enables developers to construct their own algorithms without having to directly manipulate matrices or write low-level code, thus making it easier to build complex models. It supports a variety of data types and can be integrated with other .NET languages like C# or F#.

Ask the right questions secure the right Infer.NET talent among an increasingly shrinking pool of talent.

First 20 minutes

General Infer.NET app knowledge and experience

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

How would you explain the purpose of Infer.NET?
Infer.NET is a framework for running Bayesian inference in graphical models. It provides state-of-the-art algorithms for probabilistic inference from data, which can be used in a wide variety of fields including machine learning, system biology, information retrieval, and vision.
What are the main components of Infer.NET?
The main components of Infer.NET are the model definition, inference engine, and the factor graph. The model definition is where you specify your model, the inference engine is what performs the inference on the model, and the factor graph is a visual representation of the model.
Describe the difference between supervised and unsupervised learning in the context of Infer.NET.
In supervised learning, we have a labeled dataset and the goal is to learn a function that maps inputs to outputs. In unsupervised learning, we don't have labels and the goal is to learn the underlying structure of the data. Infer.NET can be used for both types of learning.
How would you use Infer.NET to perform classification?
To perform classification with Infer.NET, you would first define a model that represents the classification problem. Then, you would use the inference engine to infer the parameters of the model from the training data. Finally, you would use the learned model to classify new instances.
What are the advantages of using Infer.NET over other machine learning frameworks?
Infer.NET offers several advantages over other machine learning frameworks. It allows for the creation of custom probabilistic models, it provides state-of-the-art inference algorithms, and it has a flexible and intuitive API. Additionally, it is backed by Microsoft, which ensures its reliability and support.
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What you’re looking for early on

Does the candidate have a comprehensive understanding of Infer.NET?
Can the candidate demonstrate a strong knowledge of .NET framework?
Does the candidate show good problem-solving skills?
Is the candidate able to communicate effectively about complex technical topics?

Next 20 minutes

Specific Infer.NET 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.

Describe the difference between generative and discriminative models in Infer.NET.
Generative models model the joint probability distribution of the input and output variables, while discriminative models model the conditional probability of the output given the input. Infer.NET supports both types of models.
How would you handle missing data in Infer.NET?
In Infer.NET, missing data can be handled by treating them as random variables. The inference engine can then infer the values of these variables from the data.
What are the limitations of Infer.NET?
Some limitations of Infer.NET include the fact that it can be slower than other machine learning frameworks for large datasets, it requires a good understanding of probabilistic models to use effectively, and it doesn't support deep learning models.
Describe the difference between batch and online learning in Infer.NET.
Batch learning involves training a model on the entire dataset at once, while online learning involves training the model incrementally, updating the model as new data comes in. Infer.NET supports both types of learning.
How would you use Infer.NET to perform regression?
To perform regression with Infer.NET, you would first define a model that represents the regression problem. Then, you would use the inference engine to infer the parameters of the model from the training data. Finally, you would use the learned model to make predictions on new instances.
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The ideal back-end app developer

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

At this point, a skilled Infer.NET engineer should demonstrate strong problem-solving abilities, proficiency in Infer.NET 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 Infer.NET.

What does the following Infer.NET code do?
Variable firstCoinIsHeads = Variable.Bernoulli(0.5);
This code declares a random variable 'firstCoinIsHeads' which follows a Bernoulli distribution with a probability of 0.5. This represents a coin flip where the coin is fair (i.e., the probability of getting heads is 0.5).
What will be the output of the following Infer.NET code?
VariableArray data = Variable.Observed(new double[] { 11, 5, 8, 9, 7 });
Variable mean = Variable.GaussianFromMeanAndVariance(0, 100);
mean.ObservedValue = data.Range.Average();
This code declares an observed variable array 'data' with some values, then declares a Gaussian random variable 'mean' with a mean of 0 and variance of 100. The last line sets the observed value of 'mean' to the average of the data array. The output will be the average of the data array, which is 8.
What does the following Infer.NET array manipulation code do?
Range itemRange = new Range(items.Count);
VariableArray itemTraits = Variable.Array(itemRange);
itemTraits[itemRange] = Variable.GaussianFromMeanAndVariance(0, 1).ForEach(itemRange);
This code first creates a range 'itemRange' based on the count of some 'items'. Then it declares a variable array 'itemTraits' over this range. The last line assigns a Gaussian distribution with mean 0 and variance 1 to each element in the 'itemTraits' array.
What does the following Infer.NET threading related code do?
InferenceEngine engine = new InferenceEngine();
engine.NumberOfThreads = 2;
Variable evidence = Variable.Bernoulli(0.5);
Bernoulli evDist = engine.Infer(evidence);
This code creates an 'InferenceEngine' object and sets its 'NumberOfThreads' property to 2, allowing it to use multithreading. Then it declares a Bernoulli random variable 'evidence'. The last line infers the posterior distribution of 'evidence' using the inference engine, and assigns it to 'evDist'.

Wrap-up questions

Final candidate for Infer.NET 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 Infer.NET application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

What are the different types of inference algorithms available in Infer.NET?
Infer.NET provides several inference algorithms including Variational Message Passing (VMP), Expectation Propagation (EP), and Gibbs Sampling. The choice of algorithm depends on the specific model and problem.
Describe the difference between a factor graph and a Bayesian network in Infer.NET.
A factor graph is a bipartite graph that represents the factorization of a function, while a Bayesian network is a directed acyclic graph that represents the conditional dependencies between random variables. Both can be used to represent probabilistic models in Infer.NET.
How would you handle overfitting in Infer.NET?
Overfitting in Infer.NET can be handled by using techniques such as regularization, early stopping, or by splitting the data into training and validation sets and using the validation set to tune the model parameters.

Infer.NET application related

Product Perfect's Infer.NET development capabilities

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