Igor Ostrovsky Blogging

There is a lot of information on the concurrent primitives and concepts exposed by the .NET Framework 3.5 available on MSDN, blogs, and other websites. The goal of this post is to distill the information into an easy-to-digest high-level summary: what are the different pieces, where they differ and how they relate. If you want to know the difference between a Thread and a BackgroundWorker, or what is the point of interlocked operations, you are reading the right article.

Continue reading »

I realized that there is a very clean way to express a multi-clause if statement by composing ternary conditional operators like this:

var result =
    condition1 ? result1
    : condition2 ? result2
    : condition3 ? result4
          …
    : conditionN ? resultN
    : default;

Continue reading »

In responses to my last week’s post, several readers mentioned LINQ-like operators they implemented themselves. I also had ideas for operators that would lead to neat solutions for some problems, so I decided to give it some thought and collect up the most useful operators into a reusable library.

My goal was to include operators that are simple to use, but applicable to a broad range of problems. I  left out operators that I thought were either too complicated to use, or too specific to a particular problem domain.

You can download the full source code of the library here (rename the file to ExtendedEnumerable.cs). Read on to find out what it contains.

Continue reading »

Ever since I learned about LINQ, I keep discovering new ways to use it to improve my code. Every trick makes my code a little bit faster to write, and a little bit easier to read.

This posting summarizes some of the tricks that I came across. I will show you how to use LINQ to:

• Initialize an array
• Iterate over multiple arrays in a single loop
• Generate a random sequence
• Generate a string
• Convert sequences or collections
• Convert a value to a sequence of length 1
• Iterate over all subsets of a sequence

Continue reading »

The folks at Dev 102 posted a programming job interview challenge. It is rather easy, but I figured that it may be a nice change of pace, since my last posting was fairly involved.

The challenge is to reverse the bits in each byte, given a large array of bytes. What is the fastest possible solution?

Continue reading »

What is the time complexity of quicksort? The answer that first pops up in my head is O(N logN). That answer is only partly right: the worst case is in fact O(N²). However, since very few inputs take anywhere that long, a reasonable quicksort implementation will almost never encounter the quadratic case in real life.

I came across a very cool paper that describes how to easily defeat just about any quicksort implementation. The paper describes a simple comparer that decides ordering of elements lazily as the sort executes, and arranges the order so that the sort takes quadratic time. This works even if the quicksort is randomized! Furthermore, if the quicksort is deterministic (not randomized), this algorithm also reveals the input which reliably triggers quadratic behavior for this particular quicksort implementation.

Continue reading »

Today, I am writing about a design problem related to C# generics that I’ve seen arise a few times. The problem occurs when we need to manipulate a generic class given a reference to its non-generic base class. For example, if a generic class Node<T> inherits from a non-generic class Node, and we are holding a Node reference to a Node<T> object, we cannot just cast the object to Node<T> because we do not have access to T.

I realize that the description is a bit abstract; let’s look at an example right away! It may look like a bit of code, but the classes are very simple and do just what you’d expect:

Continue reading »

Says who? Google search engine, none other. Yesterday, I searched for my name, and my blog appeared as the fourth link. That surprised me, because I did not intend to make the blog public before I have some content here. As far as I know, nobody links here so far, so I didn’t expect Google to find me. Maybe they automatically index newly registered domains?

Continue reading »

On the Paris Charles de Gaulle airport, I encountered this internet kiosk:

Continue reading »

It was an early morning when I received a call from one of the numerous firms that sell preparation materials for the various IT certification exams. The call woke me up, and perhaps because of my initial confusion, I did not hang up as quickly as I would normally do. Encouraged that he was still on the line, the salesperson began telling me about the life-changing effects of certifications. In the heat of his passionate speech, he exclaimed:

Continue reading »