I need idea for small project which will clear my synchronization concepts clear.
Basically any multi-threading application.
I know the idea and theory, but not able to figure out how to go more deep in details.
I am planning to use C++ and pthreads
I recommend you The Little Book of Semaphores.
There are many problems that you can try to solve. After each problem there is a hint that should help you and at the end there is a solution that you can compare with yours.
Hope this helps.
Related
I understand it should cover threading primitives (mutex, semaphore, condition variables etc.) plus design patterns (such as those specified in POSA2). But what's more? Every project has its own multithreading scenarios and one may have not dealt with those that the job is expecting?. So how does one build their knowledge and prove that they have the ability?
Regardless of specifics solid, detailed and very deep knowledge is required. One should understand how the bottlenecks form, how to deal with scalability problems, how to diagnose cases where synchronization is required but is erroneously omitted.
If for example you had a job experience with multithreading and I ran an interview to assess you I'd ask detailed questions on typical scenarios that arise when developing multithreaded programs. I wouldn't expect you knew many technologies or some specific technology, but I'd expect you to have mastered the technology you claim you're familiar with in great detail and to understand which fundamental problems it solves and how.
I would expect the candidate has knowledge and experience of the issues that arise when multiple threads access shared resources. What problems can be caused by concurrent access and what problems the solutions (such as locking etc) present.
At the very least understanding of how to write and read asych code on the platform of choice.
After this it will be understanding the specifics if the platform - e.g. such how to access the primary window in windows system while many things needs up the display at the same time.
Fundamentally is about understanding what trade-offs are needed and when.
May I present a different view. I think you should understand the basics,
but really never give up on a job based on a flyer description. I have
not met a programming concept that could not be figured out in half a day.
So, basically, read a tutorial before the interview, do not try to misrepresent
your actual experience with threading, but make sure they know the things you
had more hands on experience, and see if there is a mutual interest in you working
for the company. They may like you even if you know nothing about threading if they are confident that you can pick it up at full speed.
I know that the question has already been asked and answered, but it was more than one year ago and it looks like there are new alternatives out there.
So I'm coding a game with the SFML library (which I'm starting to find pretty much cool actually) and I'm looking for a light and fast event/delegate library.
After doing some research and having put aside the classical ones (Boosts.Signals, libsigc++), I found "cpp-events". It does not look very popular right now — since it is a very recent library — but it seems worst to be tested. I would be very interested to know if someone here tried it and can give a little feedback.
Do you have other similar (or better) options to suggest? I look rather real projects (which will be maintained) than answers on forums.
Thank you !
My feeling is that http://www.codeproject.com/KB/cpp/ImpossiblyFastCppDelegate.aspx is a great implementation for games. No dynamic memory allocation, reasonable performance, simple to debug => great for games.
I have used similar delegates in the past, this implementation looks more efficient.
The one you suggested mentions thread safety, but I would not be comfortable with a delegate based interface being used between threads. That may work fine on a small project but if a team grows, so too does the potential for disaster. I would also question the performance implications of such a feature.
Also take a look at Boost.Signals2 which is the thread-safe version of Boost.Signals. I'm using it at work in a medium-sized project and I'm quite happy with it.
I have to do enhancements to an existing C++ project with above 100k lines of code.
My question is How and where to start with such projects ?
The problem increases further if the code is not well documented.
Are there any automated tools for studying code flow with large projects?
Thanx,
Use Source Control before you touch anything!
There's a book for you: Working Effectively with Legacy Code
It's not about tools, but about various approaches, processes and techniques you can use to better understand and make changes to the code. It is even written from a mostly C++ perspective.
First study the existing interface well.
Write tests if they are absent, or expand already written ones.
Modify the source code.
Run tests to check if the modification somehow breaks the older behaviour.
There is another good book, currently freely available on the net, about object oriented reengineering : http://www.iam.unibe.ch/~scg/OORP/
The book "Code Reading" by Diomidis Spinellis contains lots of advice about how to gain an overview and in-depth knowledge about larger, unknown projects.
Chapter 6 is focuses sonely on that topic (Tacking Large Projects). Also the chapters about tooling (Ch. 9) and architecture (Ch. 8) might contain nice hints for you.
However, the book is about understanding (by reading) the "code". It does not tackle directly the maintenance step.
First thing I would do is try to find the product's requirements.
It's almost unthinkable that a product of this size would be developed without requirements.
By perusing the requirements, you'll be able to:
get a sense of what the product (and hence the code) is at least supposed to be doing
see just how well (or poorly) the code actually fulfills those requirements
Otherwise you're just looking at code, trying to divine the intention of the developers...
If you are able to run the code in a PC, you can try to build a callgraph usually from a profiling output.
Also cross referencing tools like cscope, ctags, lxr, etc. Can help a lot. A
Spending some time reading, building class diagrams or even adding comments to the parts of the code you took long to understand are steps towards getting familiar with the codebase and getting ready to modify/extend it.
The first thing you need to do is understand how the code works. Read what documentation there is and then watch the program operate under a debugger. If you watch the main function/loop and then slowly work your way deeper into the program, you can gain a pretty good idea how things are operating. Make sure you write down your findings so others who follow after you have a better position to start from.
Running Doxygen with the EXTRACT_ALL tag set to document all the relationships in the code base. It's not going to help you with the code flow, but hopefully it will shed some light with regards to the structure and design of the entire application.
A very good austrian programmer once told me that in order to understand a program you first have to understand the data-structures that the program uses.
I'm trying to learn c++ and I really want to do a lot of coding but I'm not sure what I can code.. Tbh, book exercises are not very interesting to me (usually because they're just too short). I like to code OS related stuff like I/O stuff..
I'm thinking of looking at linux and try mimicking some of the tools there.. is that a good idea?
Rewriting tools is a good idea - my C++ professor made us rewrite all the standard library string functions by hand before we were allowed to use them in our homework assignments so that is something that may help you as well. You could also check out Project Euler.
Here's a good task that involves I/O, has interesting algorithm, is not too simple, not too difficult, and can even have practical application:
Write a simple compressor / decompressor.
Simple ideas to start with: LZW, Huffman codes.
I write stuff I'm interested in ... games for example. Poker games or blackjack games. I also take existing libraries and see if I can make better versions of their stuff, like try and make a QuickSort that outperforms the Framework version. Some day I will write a chess game, but that will take some time. :)
Write a language! Make C# compile to Sparc V9 assembly (just kidding.) But seriously, I think, writing a small compiler that produces actual machine code is one of the greatest ways to learn a great deal about software and hardware (and operating systems, and libraries, etc. etc.) and pick up lots of useful skills along the way. Here's the The Dragon to get you started :)
You can try getting involved in some open-source projects if you are wanting to write code. If you find a project that has some use to you personally, it is going to greatly increase your interest levels and decrease the likelihood that you'll get bored with it and move on to something else. Plus you'll be able to get some feedback from other developers on the same project.
Try TopCoder. They're competition applet has hundreds of example programming problems. Some of them are sure to be more interesting than the exercises in the books, and you have the added bonus of seeing how your problem solving abilities measure up to other users.
I'm just now learning to programming at age 17. It's hard for me to talk to other programmers as I'm just out of high school (which means I can't take programming courses). I know that I write terrible code, and not like Jeff Atwood terrible code, my code actually sucks. So where can I post some of my code and get real programmers to review it. I know if I had a question I could ask it on StackOverflow, but I want to post a whole class and get a review on it.
The real problem here is that I'm not going to be writing the next great piece of Software. I'm going to be writing a really useless class, which will serve no other purpose than to teach me how to program. This code will never be used, ever! EVER! How can I get an advanced (or even intermediate) programmer to look at my code?
Thanks in advance! ;-)
Look to the open source community. There are plenty of existing and new projects that would love an eager (if inexperienced) developer to offer support.
Going this route offers two advantages:
You get to see great code in action and learn from it
Any changes you submit will be reviewed by an experienced developer and they will often give you excellent suggestions as to how to improve your code before it will be accepted
Start by choosing a project in your language (there are a bunch in c++) and check out the code. You don't need to understand it all, but you must be able to understand at least a portion of it.
If the project looks way to complicated, keep looking. Younger projects tend to have less code that you need to learn.
If you can't get great programmers to look at your code, do the next best thing: look at theirs!
Look for a bunch of code snippets that do the same (simple) thing. Before you look at them too closely, write your own code to perform the same task. Compare all of the snippets with your own (and each other!) and try to figure out the reasons for the differences.
I recommend looking for code from well established projects. Code from tutorials often ignores important details for the sake of simplicity.
Why don't you try RefactorMyCode?
I would try not to write useless code, but attempt to solve some particular problem. Your learning will be more advanced if you are learning in the context of a real-world scenario. It doesn't have to be a big business domain; could even be a game or a shareware utility.
As for getting your code reviewed, the open source community is a good way to go as The Lame Duck says - in fact you're guaranteed it gets some form of review if you actually contribute to a project. Other avenues to explore: your local C++ users' group, checking out a co-op program available through a junior college, or engaging someone in a company that sponsors interns.
I haven't tried sites such as RefactorMyCode as suggested by Gilad Naor, but that seems promising. And, yes, StackOverflow is a good place for bite-sized chunks of code. If you do that, explain what you are trying to do, and why you are trying to do it that way, and ask if there's a better approach. Good luck!
I think the best way to learn is the way I learned (I may be biased): trial and error. I just wrote programs all the time, teaching myself as I went. I'd write terrible code, and I would wrestle with making it do what I wanted. Often it would make me give up on that particular project. But on the next project, I'd take a different approach, and it would work better. Repeat ad nauseam. Once you know where the rough spots are in your designs, you'll be able to ask specific questions on places like SO, or, better yet IMHO, come up with better designs yourself. I independently invented all the major design patterns just through frustration at the solutions I'd created in the past. I think this gives me a valuable perspective, since for most people design patterns are just a "best practice", but I know the pain that comes with using other designs, and I can see signs of bad designs in code very easily (it takes one to know one). This last skill is one that I often see lacking in other programmers... they can't see why their design is deficient and they should use something else.
You could always try a site like Project Euler, where there are a whole load of problems that will test your skills and a whole bunch of solutions to those problems, submitted by others. Project Euler tends to focus on algorithms rather than higher level programming constructs, but I imagine that there are others in a similar vein.
Do something fun and don't worry too much about code style yet. I started out with BASIC on Commodore 64 without even realizing that there was such a thing as clean code vs dirty code. If I had worried a lot about that then, it might have hindered me from progressing. You always learn best when doing it playfully.
Maybe a bit late, but since StackExchange has Code Review, it worth the answer:
Code Review Stack Exchange is a question and answer site for peer
programmer code reviews. It's 100% free, no registration required.
Here is the link: Code Review Stack Exchange