Hello, I am Laszlo

The Knapsack Problem with Hardware Intrinsics

03/07/2020

Acknowledgements

I would like to thank Kristof for reviewing this post. He gave me great ideas to further discover the problem and to have a better understanding on AVX. Thank you, Kristof.

Introduction to the Problem

The Knapsack problem is an optimization task: given a set of items, each with a weight and a value, create a subset of these items so that their total weight is less than or equal to a given limit, and their total value is maximized.

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NDC London 2020

02/26/2020

I have attended to NDC London 2020 conference, and collected the talks I prefer or suggest for watching on YouTube.

• Make your custom .NET GC - "whys" and "hows" by Konrad Kokosa

  The talk is a deep dive into the internals of implementing a custom ZeroGC and Epsilon GC. I suggest this talk for developers being familiar with the internals of the .net runtime.

• Application Diagnostics in .NET Core 3.1 by David Fowler, Damian Edwards

  Is an essential talk to see how you can use application .net core diagnostics in a cross-platform environment.

• From WCF to gRPC by Mark Rendle

  gRPC is getting traction, Mark has worked on a tool to convert WCF services to gRPC. It is a great talk to learn about gRPC.

• Blazor, a new framework for browser-based .NET apps by Steve Sanderson

  Steve Sanderson gives a great overview on how Blazor renderer can be used for creating native (non-web) apps.

• The Internet of Pwned Things by Troy Hunt

  Troy is one of most known members of the security community. He goes over some of the significant security breaches in the past year. He discusses how companies handle these issues in a good or bad way.

• Ordering the chaos - cleaning logs and ordering events in microservices by Adam Furmanek

  It is a talk about managing logging for distributed system - correlations and ordering log messages. The presenter introduces Lamport's algorithm and gives an initial implementation on it in C#.

• Challenges of Managing CoreFX repo by Karel Zikmund

  .NET Core's CoreFX repo is a large repo with thousands of issues and pull requests. The presenter walks through the key steps to make such a big repository handleable and friendly to the open source community at the same time.

• Turbocharged: Writing High-Performance C# and .NET Code by Steve Gordon

  Bring C# speed to your next level.

• Change your habits: Modern techniques for modern C# by Bill Wagner

  This talk is about ways to modernize your coding style to latest C#.

• Crash, bang, wallop: miscellaneous lessons from exploring a drum kit by Jon Skeet

  The key thought of the talk is about the importance of diversity. The idea is being presented through an electronic drum kit and connecting this kit to software development.

• Navigating microservices with .NET Core by Ryan Nowak

  One of the best talks on microservices: how do you communicate, find other services, manage secrets, visualize problems and monitor performance, using ASP.NET Core and k8s.

• UX Design Fundamentals: What do your users really see by Billy Hollis

  One of the best UI/UX related topics. The presenter shows how to create user friendly interfaces, what are the common mistakes, and why those mistakes are made. He demos small experiences to prove how users really see the screen.

• Fly the Enterprise: Applying Aviation Lessons to DevOps Teams by Kendall Miller

  The person behind Loupe walks through aviation examples for procedures that makes flying better, safer and more reliable. The key question of the talk is how could we apply similar procedures to software development.

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Null-coalescing assignment operator ??=

02/20/2020

The Operator

One of the new C# features is the null-coalescing assignment operator: ??=. It assigns the value of its right-hand operand to the left-hand operand if the left-hand operand is null.In other words:

if(myfield == null)
  myfield = new object();

can be replaced with

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Blazor Initializing State

02/16/2020

Problem

Using WebAssembly based Blazor is one great technology to create static websites using C# and mono. Unfortunately search engines are not yet good enough to index WebAssembly based websites. A way to overcome this issue is to create a Host service which only does pre-render and serve the files for the static website. This way search engines can load the pre-rendered HTML page, and index that.

When the webassembly based, client side, static page is fully loaded and initialized, the same state must be re-created as the pre-rendered page had during rendering. If initiating this state includes an async operation, such as fetching data from a service, the Blazor client might finish the first render before the required data is available. Without data, the first render will render an empty page. Once the state initialized a new render will re-create the same (or similar) DOM as the pre-rendered page had. Having these 2 renders results a huge 'flash' like experience for the user, where an empty page is rendered for a moment.

Proposal

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Missing Number Performance Tests 2

02/01/2020

A couple of weeks ago, I had a post about a tipical interview question: finding a missing number from an unordered array.

The task goes as follows:

Given an array with integers from 1 to N. The order of the integers is unknown. One of the randomly chosen number is replaced with 0. Create a method that receives the array as an input and returns the replaced number.

I am not going into the details of edge cases, input validation, error handling, etc. This post purely checks the performance aspects of some of the possible solutions. I also assume that N=x*8.

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