Exam 70-536: TS: Microsoft .NET Framework - Application Development Foundation - PASSED

Why would I need to pass that exam at all?

There are many arguments to pass the exam. Most of them are simple bureaucracy. First of all, your resume will have additional strength if you will add few certification records on the bottom. Secondly, many companies are interested to have their employees to be certified, or maybe they want to make you promotion road more hard :) so to allow you to be promoted you need to pass some set of certificates and cope with lot of other requirements. At least this is situation which I have in my company.

Why would I need this exam for my blog?

Very easy: when YOU are on my blog first time, you read something and create your thought on topic you just read and then you decide to subscribe or not to subscribe. Question is following: what is guarantor that it worth to subscribe to my blog? And answer is "Nothing". But what will be your reaction if you will see MVP logo at the top-right of my blog? Are my chances better? Or course they are.

Why else would I need this exam?

Following point is very important but honestly I could not put it above (I will describe why). The point is to enhance you knowledge and learn something new. Of course during preparation to exam you read some books and search over MSDN on topics you are interested and which will be measured. But in real life you could be experienced .NET developer and still have difficulties to pass exam. In other words I have doubts if 10 years experienced developer could pass exam without at least some special preparation to it.

What else did I miss?

Of course - self-confidence. In order to be successful you need to feel yourself confident in things you do. In order to grow you should have something behind you, that could you help stand when you are with people who have certificates. And plus to that it is always very enjoyable to know that you know more then others. But a secret: do not show them that. It is very important. Do not praise yourself, let others do it instead.

How to prepare and how did I prepare?

You could find a lot of very interesting posts over internet on how to prepare.

I like this one:
http://lukecummins.me.uk/2009/08/70-536-my-tips-for-this-microsoft-exam/

I even found other blogs that are about certification. 

My recommendation number 1: google on how to prepare... and you will find a lot of interesting stuff.
Also while you are trying some demo tests on MeasureUp or tests from TrainingKit and if you are not confident about answer do not try to remember it - go and figure answer in depth!

Also I wrote some tips on how to read TrainingKit. At least this works for me:

• Read accurately but quick if theme is familiar to you.Skip “Real Word” and pay attention on “Important” and “Exam Tip”, try to remember it!
• If there are boring explanation and then code, switch first to code and analyze if you understand everything there, and if that is true, don’t return back to text.
• Do not execute Labs unless you do not understand what you had read.
• If there are difficult chapters try to read them twice – I did this with Application Security.

How was it?

Night before exam I felt confident about exam, but was still worrying.. so I was preparing till 3am. In the morning I came to work as usual and did few things... reviewed ones code, checked e-mails... expressed my thoughts on demo we should have today and wrote e-mail to team members that I will be out for about 2 hours. My company is Microsoft's parner so I do not need to move to other location - just get down 5 floors.
First couple of questions I was nervous, but then I felt that I'm confident with most of questions. I marked only 2 out of 40 for additional review. When I finished I got message saying that I PASSED EXAM with score 907. This means that I answered incorrectly for about 4 questions. I think that this is very good result.

Picture which I get is like following:

My next target is probably 70-505. Passing it is point of honour, because I already failed it twice because of overflow of confidence.

Also as I'm active in preparing developers meeting for developers from my project and I'm thinking to teach our developers in order to get certification - covering some areas from exam.

Express your thoughts on passing this exam.

Today's English Lesson

Today's lesson was not usual. My usual teacher is in vacation, so we have conference calls and we are trying to imitate different situations during conf. calls.

Situation
Initially there was an agreement with the Client for a particular scope of project.  After some time the Client adds more features that require additional time for investigation and execution – in particular he wants to change the user interface (UI) from HTML to FLEX. It’s high time to start working on user interface but the Client is silent regarding reconsideration of the agreement terms. Project Manager has to take charge of conducting a negotiation with the Client and decides to invite Tech Lead, QA and Senior Developer for that.

Roles has been assigned to students. And initially I got TL role, but when we dialed up we discovered that 3 of us are not present, so teacher decided that I could take 3 roles in one time.

Roles are following:

Tech Lead: You do not know FLEX and you do not have time to study it because it is time consuming. But you believe that it is possible to fulfill all the requirements if your PM can find a specialist in that technology and make him TL of that part of the project.

Senior Developer:  You have used FLEX before. You are not an expert in it but you can do the task. However, you require more time (you have your own tasks which you have to finish in time) and you also need more people.  Anyway, there should be reconsideration of the agreement terms.

QA: You know that whenever a new feature is added, it always involves adding test cases and plans rewriting. You are 100% sure that this change will require extra effort for testing. Besides, the integration of a new feature will lead to the additional integration testing.

I was trying to be in all of them and I would say that I succeeded in those.One of interesting things about this is that I was dialing from my desk, and one of the colleagues was really confused about what I'm talking out there... Maybe he was concerned if I'm not mad, but teacher said that it was tremendous :)

I got a lot of fun and I really appreciate that my company game me possibility to learn English in lot of fun and enjoyable ways.

Brainbench Master Certification in C#

It turns out that I'm eligible to pass exam 70-536 for free - my company will pay for me, but before I'm required to pass Brainbench C# exam with higher than 4.0 score.

And I just did it - my score is 4.03.

You could see my results using following link: http://www.brainbench.com/transcript.jsp?pid=9108054

So now I could use this logo on my blog (see somewhere on the right):

Also in e-mail which I got is following information:

You are eligible for a certificate! Would you like to receive it?

Printed paper certificate suitable for framing $14.95 Get Electronic Certificate $4.95 Get

How do you think should I pay for that? Please let me know.


Also following information says that I have weak areas in implementing Services and Data Consumers. Need to check-out in more details about that.

Test: C# Date: 27-Apr-2010 Score: 4.03 Weights: 100% C# Elapsed time: 46 min 23 sec

C# Score: 4.03 Percentile: Scored higher than 90% of previous examinees Demonstrates a clear understanding of many advanced concepts within this topic. Appears capable of mentoring others on most projects in this area. Strong Areas Grammar Object-Oriented Programming Value and Reference Types Delegates Properties, Indexers, and Fields Weak Areas Developing Data Consumers and Services Methods

Guys, it is quite easy to pass this. And don't loose chance, this exam is free till 30 April.

MCTS 70-536 Application Development Foundation book review

What can I say about this book? It is specialized for passing specific Microsoft Exam. If you are going to pass 536 exam you 100% need it. If you just want to learn some core things about developing applications with .net, book is not best choice. It will lead you through big portion of class names, different methods and enumerations, which could be easily seen in MSDN documentation up to date. I would even say that books like authors took everything possible from MSDN that is related to exam. Also book have mistakes, which I think should not be in such books. Plus to that book is dry to read, but you can read it fast if you know how.





How to read book:

• Read accurately but quick if theme is familiar to you.Skip “Real Word” and pay attention on “Important” and “Exam Tip”, try to remember it!
• If there are boring explanation and then code, switch first to code and analyze if you understand everything there, and if that is true, don’t return back to text.
• Do not execute Labs unless you do not understand what you had read.
• If there are difficult chapters try to read them twice – I did this with Application Security.

I would recommend this book if you are going to pass exam, if not just check-out maybe there are some interesting things that you should know, but do not read book whole end-to-end.

It is time to get Microsoft Certification

When is it time to be Microsoft Certified?
My company is developing new certification model, named abc (I’m not sure if I can use original name), which includes few levels such as abc Certified Junior, abc Certified Intermediate, abc Certified Senior... and so on... To become Senior developer after you are Intermediate you first need to get abc Intermediate certification.

Each of the levels has some requirements like industry experience, some number company-wide presentations, passed performance appraisal with strength area marks, passed knowledge evaluation, but what is important here is that each next level also requires some external certifications. For example, to be abc certified intermediate level in .NET desktop you need to have 2 certificates: 70-505 and 70-536.

Hey, but I'm already promoted to be intermediate, but do not have certificates... At least it is one of the reasons why I cannot become Senior (another one is that I need about half a year more experience and improve my knowledge). And this makes me bit sad.
Actually I tried to get 70-505 exam immediately after I get promoted (summer 2009). First time it was free attempt, and I failed it. Shit, but that was so easy, I got 670 out of 1000 with required 700.

Why did I fail it? There are few reasons:

* Exam 70-505 includes features from the 3.0 framework, which I did not ever use. For example it includes easy question regarding the Linq. I did not know Linq at that moment. It included question regarding installing and deploying strategies. Which I did not ever try. Stop. Am I so bad? I knew design patterns; I had experience in developing desktop applications. But I was interacted only with actual developing of easy things; I was not familiar with whole lifecycle of our product. To be honest we have so complicated lifecycle that nobody knows it well.
* I was too much self-confident about the exam.
* I did not spend a lot of time on preparing, maybe half a day.

I know that there are other ways to successfully pass exam, I think you know what I mean, but I did not see in internet actual tests for my exam, and besides that is not good way to pass it. I saw some people that passed with 1000 score other exams. Why? They found exact test in internet.

Let’s suppose that I was not ready and I did not know how to pass such exams.

Ok. Do you know Roosevelt? His words: “Never, never, never, never…give up!” And I did not give up. I tried again with the same exam month later. And you know – I field it with score less than 500. I was pure sure that questions will be similar, and they were. I was too much confident that I will pass it, but I did not. So I blew 50$. Holly shit.



Was it needed to pass Microsoft exam? Tips are following:

•    Get resource to learn from it. Best choice is Microsoft Training Kits.
•    Be aware what does your exam include, if there are some unknown technologies for you, ask yourself if this is correct exam for you.
•    Ensure that you interacted with each technology meant there in real world, if you have not interact, just write simple applications when preparing to exam.
•    Do not schedule exam, if you are not self-confident in your knowledge.
•    Do not be too much self-confident in your knowledge. Most of exams are dry tests, which include some monkey questions that could be easily forgotten.
•    Train, train, train… and never give up.


Getting MCTS for me is very important step in my career. (See picture below).
I’m going to achieve this with passing 536 and 505 in short terms.

My presentation on the Service Oriented Architecture

Yesterday I executed my presentation on the Service Oriented Architecture. It was awesome. I got good portion of emotions.

People

I was really surprised how many people have come to listen to me. As per me it was supposed that this local Architecture Group (AG) is for couple of people, who have desire to spend their free time on talking about SOA, but for my great surprise almost all team came, I mean developers from whole enterprise project where I work. Guys, there should be something that I don't know about intent of this group?

Rehearsal

Before presentation I as usual did my rehearsal. First it was presenting to my friend, who is also developer. We call this 'Turbulent Developers Community' where we sit in the evening with beer and talk about different interesting IT things. So he brought few interesting questions for which I was now ready to respond. Also, I had my *.ppt at my phone, so when getting to my work I was trying to replay presentation in my mind. І на останок, вже безпосередньо перед презентацією я розказав її своїй дівчині в скороченому режимі - це зайняло близько 20 хвилин. Дуже тобі дякую за це!

Presentation

So, I started with plan which I have in this blog post. People were listening with attention and that is very appreciating. Also, what was enjoyable is that they had a lot of different comments on what about I was talking. They even spoke to 3 of my slides instead of my... OMG.

How was it?

... asked I, and got an answer: "It's a great success! ... can we now get money out of that?.. :)". Those are words of my colleague with whom I work on the same piece of software. I really hope that other also enjoyed what I did.

Conclusion

For myself I have discovered that I learnt more about how to provide a good presentation. I do not say that this is my best presentation. I this the best I had is presentation on DDD, but anyway... having more experience in that area is very good achievement.

Keep in mind - you will die someday

What is the intent of my life? I spend my life at work, so that is a very big part of it. If above said it truth, why don't then do the best at work and in your growth? For me it is mandatory. If you don't like you work - just change it. Just do it!

Everyone have to die some day. Think about what you do and what you want to achieve. Have super large dreams. Often why I'm getting to the work at town vehicle many people talks and as I understand the intent of their life it to find a good job, to have a car, home and family. I don't say that family is bad, BUT why to put such trivial task in front of you? You have one life and then death!

Service Oriented Architecture - Introduction

Currently I'm part of local SOA group. Purpose of it is to accumulate information about SOA and its implementation, to talk and discuss different approaches that could be applied with this paradigm of developing software. I volunteered to prepare first introduction presentation. So other more experienced guys will prepare more deep presentations. Right folks? ;)

What is SOA?

Over internet you could find lot of different definitions to SOA. One of the most simplest is:

Service Oriented Architecture is an architectural style of building software applications that promotes loose coupling between components for their reuse.

Term itself could be a bit confusing, because it combines two different things. First two words describe software methodology - how to build software. Third word, architecture, represents picture of company's assets, which all together should build a good building. So, in other words, we could say that SOA is strategy that forces building software assets in business using service-oriented methodology.

Wikipedia gives more complex definition:
A paradigm for organizing and utilizing distributed capabilities that may be under the control of different ownership domains. It provides a uniform means to offer, discover, interact with and use capabilities to produce desired effects consistent with measurable preconditions and expectations.

SOA is not simply IT solution, it is whole paradigm shift. It is another step to the IT industry dream, when we will not need write low level code, but just combining different ready components to have product which is good for immediate selling. It is about describing, building, using and managing your IT environment with focus on services and capabilities it provides rather then on concrete technology used for that.



Advantages both for Business and for Development

Before we start with what stands behind SOA lets first take a look on advantages that it brings for Business and Development process.

Advantages of service-oriented development:

Software reuse is one of the most commonly used arguments to justify SOA. If services are developed of good size and correct scale they could be reused. Consider that you company has for sailing departments, each of them works with orders, so all of them have code that checks customers credit card, books order and so on. But checking credit card is almost 100% the same task in all departments, so developers could gather code and make it shared for all systems, in this case software reuse is accomplished. All that we need to have in our systems is client that is able to consume service. Systems are no longer concerned about the internal verification process. In future is company will create new department it will just reuse existing service, so development time will be saved and money for business.
But we could not say that reuse will be accomplished everytime. First of all service should be of right size, not to big and with correct scope. This meas that we will not be able to use 'verify credit card and book that car' in department where they sale phones. I also found that by only from 10 to 40 percents of services are reused. This adds additional requirement to implementers to be accurate with choosing correct scope and size of service.
Productivity increase. That is easy, once we achieved re-use system, we could not spend our time on implementing same things, testing them. We only need integrate services and do integration testing, so this becomes more cheaper.
Increased agility. Even if re-use will not be achieved we anyway get additional agility with having services. For example our selling department has divided whole process into few services, like 'check user', 'check credit card', 'get order', 'ship order'... And if will need change in process we could do this in isolated island of concrete service. That is how we get more flexibility.    

Advantages of SOA strategy are:

Better alignment with business. Business people can now imagine how their business are constructed in terms of technology. Once they better understand how application is built they could promote their requirements to development teams in more efficient way. And as well development team is now more suitable with understanding of what does that business really do. It is now much easier to explain why having credit card in one service is good decision.
A better way to sell architecture to the business. Having gap in understanding how all is really implemented was also a preventing thing to sell IT product to the business.

What are services?

So we talk about services. But what exactly are those services?
Service is complete self-contained component, that provides defined tasks. List of tasks could be obtained by consumer using agreed contracts. Consumer should not know about internal implementation of service. Communication between consumer and service should be done through platform and language independent contracts.

Here is list of just mentioned properties of good Service:

• Self-contained module that performs a predetermined task
• Software components that have published contracts/interfaces
• Black-box to the consumers
• Platform-Independent
• Language-Independent
• Operating-System-Independent
• Interoperable

Main Architecture Concepts

On the picture below we see how three main parts of SOA interacts with each other.

Loose coupling - Services maintain a relationship that minimizes dependencies and only requires that they maintain an awareness of each other.
Service contract - Services adhere to a communications agreement, as defined collectively by one or more service description documents.
Service abstraction - Beyond what is described in the service contract, services hide logic from the outside world.
Service reusability - Logic is divided into services with the intention of promoting reuse.
Service composability - Collections of services can be coordinated and assembled to form composite services.
Service autonomy – Services have control over the logic they encapsulate.
Service optimization – All else equal, high-quality services are generally considered preferable to low-quality ones.
Service discoverability - Services are designed to be outwardly descriptive so that they can be found and assessed via available discovery mechanisms


How could it be implemented?

Since SOA is technology independent we currently have really lot of different possiblities to implement it. So this could be simple Web service, which sends data packed into XML with help of SOAP, at the same time contracts are established with WSDL. Possibility to discover available services could be UDDI.

We could also realize SOA with REST, DCOM, CORBA, DDS and other things.

Also Microsoft has its solution for the SOA which is WCF. It is very great tool to develop distributed application. I'm glad that already have at least some experience using it.

What are SOA Patterns?

Here is very good site on disign patterns applicable with SOA.

Mistakes when implementing SOA

There are lot of mistakes that could appear when you are trying to introduce SOA in your project. They are listed in Twelve Common SOA Mistakes pdf.


I hope that I will be able to provide a good presentation, since I don't feel myself to be professional in this area and don't have enough required background, except of few months using WCF.

Refactor: Sequential Coupling => Template Method

Another colleague brought me present today - the blog post. Thank you. You were right!

We will do some refactoring which will lead us from Anti-Pattern to Pattern. From Sequential Coupling to Template Method. And as I see it could be very common way to refactor bad code that represents mentioned anti-pattern.


So, lets start with the following question. What do you see to be wrong with following code?

  public class Manager

  {

    public void DoTheProject()

    {

      IWorker worker = GetMeWorker();

      worker.PreWork();

      worker.Work();

      worker.AfterWork();

    }

Manager is very angry guy and he needs to get the project done. For that he would like to get some worker, which implements IWorker interface, and delegate some work to him. But also manager knows that worker could be new to project so it will require do go ahead and to some preparational work before and maybe something to do after work is done...

What is wrong? Answer is that Manager cares too much about how worker should organize his work. Why should manager know that worker needs to be prepared for work? What do we have here is the Sequential Coupling anti-pattern.


(My definition) 

Sequential Coupling Anti-Pattern - appears when consuming code is forced to call methods of used object in particular sequence to make it work correctly.

If we call Work and then PreWork, code could be broken. And we want to prevent this. For example, we can move all that stuff in one method - Work, but also sometimes it is needed to perform pre or/and after work, but sometimes not. That is why we had following design that allowed us do this. See that StandardWorker doesn't need do something after he has finished. This was achieved with virtual and abstract methods.

  public interface IWorker

  {

    void PreWork();

    void Work();

    void AfterWork();

  }

  public abstract class WorkerBase : IWorker

  {

    public virtual void PreWork(){}

    public abstract void Work();

    public virtual void AfterWork(){}

  }

  public class StandardWorker : WorkerBase

  {

    public override void PreWork()

    {

      Console.WriteLine("... I need to prepare to work ...");

    }

    public override void Work()

    {

      Console.WriteLine("... hard work is in process ...");

    }

  }

So, what we need to do is to hide the order in which we call methods, be sure that order remains the same, and still have possibility to override each of method. What I just described is Template Method.

In our example we could leave one method in interface, then implement it in base class with calling everything else we need in correct order, each of those things we call could be overridden, we left them protected to do not show to the world.

  public interface IWorker

  {

    void Work();

  }

  public abstract class WorkerBase : IWorker

  {

    

    //this is template method

    public void Work()

    {

      PreWorkActivity();

      WorkActivity();

      AfterWorkActivity();

    }

    protected virtual void PreWorkActivity() { }

    protected abstract void WorkActivity();

    protected virtual void AfterWorkActivity() { }

  }

  public class StandardWorker : WorkerBase

  {

    protected override void PreWorkActivity()

    {

      Console.WriteLine("... I need to prepare to work ...");

    }

    protected override void WorkActivity()

    {

      Console.WriteLine("... hard work is in process ...");

    }

  }

  public class Manager

  {

    public void DoTheProject()

    {

      IWorker worker = GetMeWorker();

      worker.Work();

    }

    private IWorker GetMeWorker()

    {

      return new StandardWorker();

    }

  }

It really looks for me that it could be common to perform refactoring from Sequential Coupling to Template Method. Hope you liked this post. CodeProject

Null is not equal to null. How could that happen?

Today one of my colleagues bring me a present - a new blog post!

Please take a look on the following picture and think how could execution step into the if statement. See that oldPerson is null!

She has asked everyone if anyone knows how could this happen. Do you know?


Honestly my first thought was that it is something with Nullable<T>, or maybe method Find isn't what we think about it. I had thought that it could be LinQ method, which is somehow wrong, whatever. But nothing of that is true. :(


She did not sent the whole picture so we did not know what is the type of oldPerson object. So far we don't know the type and we know that "!=" behaves somehow different. That's it! Operator is wrong and I won beer. (of course not :) )


So let's take a look on implementation of the operator:

    1 using System.Collections.Generic;

    2 

    3 namespace ConsoleApplication1

    4 {

    5     internal class Person

    6     {

    7         public string Name { get; set; }

    8 

    9         public static bool operator ==(Person left, Person right)

   10         {

   11             if (ReferenceEquals(null, right)) return false;

   12             if (ReferenceEquals(left, right)) return true;

   13             return Equals(left.Name, right.Name);

   14         }

   15 

   16         public static bool operator !=(Person left, Person right)

   17         {

   18             return !(left == right);

   19         }

   20 

   21         public bool Equals(Person obj)

   22         {

   23             return (this == obj);

   24         }

   25 

   26         public override bool Equals(object obj)

   27         {

   28             if (ReferenceEquals(this, obj)) return true;

   29             if (obj.GetType() != typeof(Person)) return false;

   30             return (this == ((Person)obj));

   31         }

   32 

   33     }

   34 

   35     class Program

   36     {

   37         static void Main(string[] args)

   38         {

   39             var persons = new List<Person>()

   40                 {

   41                     new Person(){Name = "Ivan"},

   42                     new Person(){Name = "Andriy"}

   43                 };

   44 

   45             foreach (var item in persons)

   46             {

   47                 var oldPerson = persons

   48                     .Find(x => x.Name == item.Name+"Not Andriy");

   49 

   50                 if (oldPerson != null)

   51                 {

   52                     item.Name = oldPerson.Name;

   53                 }

   54             }

   55         }

   56     }

   57 }

Do you already see where the problem is? It is definitely in line 11: if (ReferenceEquals(null, right)) return false;
if we will get null in right object it will say that null is not equal to null.


Reason why she needs that so much complicated is because she accesses properties of the object in return condition later:
return Equals(left.Name, right.Name);

Get started with F#

Renaissance of functional languages

We are at renaissance of functional languages. When I read blog posts I often see guys talking about functional programming and stuff related to it. Community wants more features that functional style provides for us. In response to that creators of languages and technologies are now introducing a lot of amazing cool features to make our life happier. They also create new languages, and so on.


What is going on with C# nowadays?

Let's start with what we do have with C# nowadays. It has moved to functional side slightly. Introducing LINQ is big step in that direction. We are moving away from imperative programming to functional, for example this simple loop represents imperative way to work with list items.

      foreach (var element in list)

      {

        Console.WriteLine(element);

      }

Using LinQ we can have so much elegant functional syntax:

      list.ForEach(Console.WriteLine);

So we pass function into function. Simply saying that is why we call this functional programming. If example above isn't so bright take a look on next:

      Func<int, int> doubleThat = delegate(int x) { return x * 2; };

      var from2To20 = from1To10.Select(doubleThat).ToList();

Another example of that C# is more close to those languages is introducing var keyword, which doesn't mean that we can change type in further code like in dynamic languages, but that is thing which really helps us to write code without being really concerned about types, but the language itself is still strongly typed. If you would say here about C# dynamics, hm.. honestly I'm not a fan of that thing in C#, but maybe it gives some advantages for us.

Immutability

Few days ago I have heard podcast where guy from Microsoft .NET languages team spoke about different features that community had requested to language C#. One of them was immutability and it looks that they are going to introduce this in further releases (after 4.0 of course). So what is immutability? It is something that functional languages has by default and imperative hasn't :).

For example we have

   int number = 1;
   number = number + 3;

We can change number as many times as we want. But the same in F# will produce compilation error:

("<-" is assignment operator in F#). In order to make it work you will need another element result:

If you want variable with you 100% want to change you should declare this using mutable keyword:

Functions

So lets move to much interesting - declaring functions:

ten will be immutable variable which has value 10.

Are you familiar with parameter binding in C++ functors? It doesn't matter but, currying of methods in F# reminds me that. Take a look how we get new method with mixing function multiply and using one frozen parameter.

Using F# library in other .Net languages 

I did all this fun stuff with creating new F# library in Visual Studio. I viewed results of code which interested me with selecting it and pressing 'Send To Interactive' from context menu. Next what was interested for me is how can I use that dll in my usual C# program. So I created console application, added reference to my F# lib. Now I can use it like below:

See how things differs out there. Method is seen as method, immutable variables as properties without setter and mutable as properties with setter. Forgot to mention that FirstFSharpProgram  defines with keyword module at the top of *.fs file.


Why?

When could F# be useful? Anywhere you would like. But as it creators says it has lot of multi-threading capabilities plus to that you write immutable code, which was the main root of stupid bugs in imperative programming. Plus to that you can easily use it in combination to other .NET languages.

Don't miss chance to learn this language if you are interested in it.

Take a look on this elegant Fibbonachi solution: let rec fib n = if n < 2 then 1 else fib (n-2) + fib(n-1)

Refactoring your code to be multithreaded

In this post I will start with some time consuming algorithm, which is very simple and will move to decrease its execution time with using advantage of my two processors.

Time consuming algorithm

For example you have some complex calculations algorithm, which runs on array of dozens of elements. For simplicity let it be list of doubles like below:

      var inputVector = new List<double>();

      for (int i = 0; i < 10000; i++)

        inputVector.Add(random.NextDouble());

All complex calculations that you do are located in class OneThreadAlgorithm. It goes through all array and gets index of the element, which is more closer to value d that you provide inside of method FindBestMatchingIndex.

  internal class OneThreadAlgorithm

  {

    public readonly List<double> InputVector;

    public OneThreadAlgorithm(List<double> inputVector)

    {

      InputVector = inputVector;

    }

    public int FindBestMatchingIndex(double d)

    {

      double minDist = double.MaxValue;

      int bestInd = -1;

      for (int i = 0; i < InputVector.Count; i++)

      {

        var currentDistance = DistanceProvider.GetDistance(InputVector[i], d);

        if (currentDistance < minDist)

        {

          minDist = currentDistance;

          bestInd = i;

        }

      }

      return bestInd;

    }

  }

If you are interested in DistanceProvider, it just returns between two double elements. Take a look on it.

  public static class DistanceProvider

  {

    public static double GetDistance(double val1, double val2)

    {

      for (int i = 0; i < 10000; i++)i = i + 1 - 1;

      return Math.Abs(val1 - val2);

    }

  }

As you see I have some loop before returning value. It is needed to imitate hard calculations. I'm not using Thread.Sleep(), because there are some nuances, that will appear when we will move to multithreading, so I would I like to neglect them.

First change: dividing calculations to sections

As we see algorithm just loops through collection of values and finds some element. To make it going in few threads first we need to accommodate it. The intent of our accommodation is to divide calculations to sections, so we introduce following method

    public void FindBestMatchingIndexInRange(int start, int end, double d)

    {

      double minDist = double.MaxValue;

      int bestInd = -1;

      for (int i = start; i < end; i++)

      {

        var currentDistance = DistanceProvider.GetDistance(InputVector[i], d);

        if (currentDistance < minDist)

        {

          minDist = currentDistance;

          bestInd = i;

        }

      }

      BestMatchingElements.Add(bestInd);

    }

So, what it does is the same that we had previously. Only the difference is that now we start searching for best matching indexes in range starting with index start and finishing with end, also we put result to the BestMatchingElements list. After we went through all sections we can find best matching element only in that list. See that below:

    public int FindBestMatchingIndex(double d)

    {

      double minDist = double.MaxValue;

      int bestInd = -1;

      BestMatchingElements = new List<int>();

      int sectionLength = InputVector.Count / ParallelingNumber;

      int start = 0;

      int end = sectionLength;

      for (int i = 0; i < ParallelingNumber; i++)

      {

        FindBestMatchingIndexInRange(start, end, d);

        start = end;

        end += sectionLength;

        if (i == ParallelingNumber - 1) end = InputVector.Count;

      }

      foreach (var elementIndex in BestMatchingElements)

      {

        var currentDistance = DistanceProvider.GetDistance(InputVector[elementIndex], d);

        if (currentDistance < minDist)

        {

          minDist = currentDistance;

          bestInd = elementIndex;

        }

      }

      return bestInd;

    }

So now it works as well as before, theoretically it is a bit slower, and it does, especially when you divide array to lot of segments (number of segments we define with variable ParallelingNumber property).

Second modification: storing task information into one object

When we use multithreading we schedule method which represents public delegate void WaitCallback (Object state). So to accomplish this we create new class FindBestInRangeRequest and use it as an object that passes to changed method:

    public void FindBestMatchingIndexInRange(object bestInRangeRequest)

    {

      var request = (FindBestInRangeRequest)bestInRangeRequest;

      double minDist = double.MaxValue;

      int bestInd = -1;

      for (int i = request.Start; i < request.End; i++)

      {

That new class FindBestInRangeRequest encapsulates Start, End, D and other values needed to schedule a threading task. See that class:

    internal class FindBestInRangeRequest

    {

      public int Start { get; private set; }

      public int End { get; private set; }

      public double D { get; private set; }

      public ManualResetEvent Done { get; private set; }

      public FindBestInRangeRequest(int start, int end, double d, ManualResetEvent done)

      {

        Start = start;

        End = end;

        D = d;

        Done = done;

      }

    }

As you see we are also passing the ManualResetEvent object, which has method Set(), with using it we can identify that task execution has finished.

Third modification: Using ThreadPool

We can allocate threads manually, but that operation is very expensive, so it is strongly recommended to use ThreadPool.
So here is how we do use ThreadPool to call FindBestMatchingIndexInRange.

        var bestInRangeRequest = new FindBestInRangeRequest(start, end, d, DoneEvents[i]);

        ThreadPool.QueueUserWorkItem(FindBestMatchingIndexInRange, bestInRangeRequest);

after we have scheduled all ranges we should ensure that all threads has synchronized. We could do this using

      WaitHandle.WaitAll(DoneEvents);

 method.
Another interesting thing is that saving into BestMatchingElements is not safe, so we use to unsure safe adding.

      Monitor.Enter(BestMatchingElements);

      BestMatchingElements.Add(bestInd);

      Monitor.Exit(BestMatchingElements);

which is the same to the locking with keyword lock.

Full code base of algorithm

  internal class MultiThreadAlgorithm

  {

    public int ParallelingNumber { get; private set; }

    private List<int> BestMatchingElements { get; set; }

    private ManualResetEvent[] DoneEvents { get; set; }

    public readonly List<double> InputVector;

    public MultiThreadAlgorithm(List<double> inputVector, int parallelingNumber)

    {

      InputVector = inputVector;

      ParallelingNumber = parallelingNumber;

      DoneEvents = new ManualResetEvent[ParallelingNumber];

    }

    public int FindBestMatchingIndex(double d)

    {

      double minDist = double.MaxValue;

      int bestInd = -1;

      BestMatchingElements = new List<int>();

      for (int i = 0; i < ParallelingNumber; i++)

      {

        DoneEvents[i] = new ManualResetEvent(false);

      }

      int sectionLength = InputVector.Count / ParallelingNumber;

      int start = 0;

      int end = sectionLength;

      for (int i = 0; i < ParallelingNumber; i++)

      {

        var bestInRangeRequest = new FindBestInRangeRequest(start, end, d, DoneEvents[i]);

        ThreadPool.QueueUserWorkItem(FindBestMatchingIndexInRange, bestInRangeRequest);

        start = end;

        end += sectionLength;

        if (i == ParallelingNumber - 1) end = InputVector.Count;

      }

      WaitHandle.WaitAll(DoneEvents);

      foreach (var elementIndex in BestMatchingElements)

      {

        var currentDistance = DistanceProvider.GetDistance(InputVector[elementIndex], d);

        if (currentDistance < minDist)

        {

          minDist = currentDistance;

          bestInd = elementIndex;

        }

      }

      return bestInd;

    }

    public void FindBestMatchingIndexInRange(object bestInRangeRequest)

    {

      var request = (FindBestInRangeRequest)bestInRangeRequest;

      double minDist = double.MaxValue;

      int bestInd = -1;

      for (int i = request.Start; i < request.End; i++)

      {

        var currentDistance = DistanceProvider.GetDistance(InputVector[i], request.D);

        if (currentDistance < minDist)

        {

          minDist = currentDistance;

          bestInd = i;

        }

      }

      Monitor.Enter(BestMatchingElements);

      BestMatchingElements.Add(bestInd);

      Monitor.Exit(BestMatchingElements);

      request.Done.Set();

    }

    internal class FindBestInRangeRequest

    {

      public int Start { get; private set; }

      public int End { get; private set; }

      public double D { get; private set; }

      public ManualResetEvent Done { get; private set; }

      public FindBestInRangeRequest(int start, int end, double d, ManualResetEvent done)

      {

        Start = start;

        End = end;

        D = d;

        Done = done;

      }

    }

  }

Do you see how our class is cumbersome. So that is why do we call multithreading to be complex and not an easy to implement.

Does this pay off?
Of course, it does. I wrote this example, because I've been working on another, a bit more complex thing, but generally I did the same.

Here is output of execution of three variants of algorithm: simple, division to sections, multithreading.

One thread result = 9841. TIME: 0H:0M:2S:583ms
One thread with sections result = 9841. TIME: 0H:0M:2S:917ms
Multi threads result = 9841. TIME: 0H:0M:1S:939ms
Press any key to continue . . .

As could bee seen, multithreading variant is much-much faster. It could be even faster if I had more than two processors on my machine.