For testing the under construction library I wrote a test suite which performed 100 variable changes from peer to peer and finally exited when all of the handshakes where complete..
The test suite was then debugged using valgrind and standard gdb and despite some early mixups and architecture problems that were very evident with the debugger output after they were gradually fixed some very strange behaviour ensued as the test suite would “randomly” stop at some point and the program “seemed” to stop acknowledging and transmitting changes on the variables without an apparent reason..

Adding to the complexity of identifying the problem was the fact that a total of 6 threads spanning in two procedures could potentially cause a deadlock somewhere ( despite the mutex protection ) ..

After 5 or 6 days of trying to fix the problem I started to get desperate going line by line and almost rewriting all the critical segments until I figured it out..

The problematic code was the following :

unsigned long GetVariableHash(struct VariableShare * vsh,void * ptr,unsigned int size_of_ptr)
{
if (size_of_ptr unsigned long * stacklongptr = ptr;
unsigned long stacklong = *stacklongptr;
return stacklong;
}else
{
return rvhash(ptr,size_of_ptr);
}
return 0;
}


Each pointer (void * ptr) points to a memory block of variable size (unsigned int size_of_ptr ) and the hash values get stored on an unsigned long ..
All is good for variables that are longer than an unsigned long since they are casted to a char * "string" and then a hash function converts them to a reasonably unique unsigned long.. But .. for smaller sizes of pointers such as unsigned ints my code directly casted the 4byte payload of the pointer to the 8byte accomodation of the unsigned long leaving 4 bytes uninitialized..

What was very funny was that in all the fprintf(stderr,"hash %u",(unsigned int) hash); calls I had added to review the function the results appeared completely normal but when two hashes where compared they failed the equal if operation even if they seemed to carry the same value when fprintf'ed

To better illustrate a simplified version , what I saw was an instance of

fprintf(stderr,"old hash %u , new hash %u\n",(unsigned int) oldhash,(unsigned int) newhash);
if (oldhash==newhash) { fprintf(stderr,"They are the same\n"); } else
{ fprintf(stderr,"They are not the same\n"); }

where I got output like :
old hash 5 , new hash 5
They are not the same

Needless to say valgrind ( which is a great tool and this wasnt its fault ) has an initialization check that did not report the unitialized bytes , the possible problem of unitialized bytes didnt even cross my mind while hastly writting the function @ 3 AM 2 years ago ( the problematic commit ) and 2 weeks of my life were "kind of" thrown away ..

It is true that you can sometimes shoot yourself in the foot when using tools that give you this kind of freedom , and this might be just such a case , but I frankly found it enlighting..
C is an awesome language!

The fix commit

http://www.kathimerini.gr/4dcgi/_w_articles_kathremote_1_29/03/2012_435325

http://www.kerdos.gr/default.aspx?id=1707043&nt=103

http://www.euro2day.gr/news/market/123/articles/690675/Article.aspx

Parts of the results , so far :

-A trendy ( ) company name generation tool for a potential new software company

-A list of the 267 “best” greek companies ( their websites ) , along with what each of them has to offer as a service ( generated using WebSniper )

-The realization that 3 ERP/CRM product families , namely SAP , SoftOne and Singular Galaxy are basically dominating the market and many smaller companies just use them instead of developing an in house solution ( which makes sense ).
The fact that software solutions are VERY expensive (for example SAP offers a ERP/CRM “entry-level” package for 41.000 euro ) and all of the other popular solutions have similar pricing with large profit margins. These large profit margins might also explain why almost all of the major companies are Microsoft partners ( this of course is bad for them and their clients ,but on the other hand what difference do 100 euro annually make in a 41000 euro transaction )

An opensource ERP/CRM program would really be a killer app ,and from a small search there seems to be one which is called openTAPS and another one which is called OpenERP , both licensed with AGPL I wonder what the impact will be when these projects along with OpenCart and others will be “discovered” in Greece!
Beetech is the “only?” company offering OpenERP right now..

-Despite the many Microsoft Gold partners etc. , Microsoft Dynamics CRM was only offered by one vendor

-From what I’ve searched there doesn’t seem to be a big piracy problem with Greek software ( In contrast to SAP for example )

-Most of the products sold , offer different versions of the product with arbitrary limits to be able to appeal to every possible client purchasing power. While I find this reasonable when you let’s say buy a house with or without a pool ( which implies many man-hours to build the thing ) , on software flipping a variable according to a license key for the same binaries , seems like a shitty thing to do.
If someone built me a house with a pool and then because I didn’t pay them for the “Deluxe house packet” covered it with concrete , it would be crazy..

-Android/Mobile development seems to be pretty popular..!

-E-Goverment projects also seem to be very popular..!

-There seems to be a big demand for SMS gateways , Radio programs , Video Club management programs. I guess in a few years ( i.e. when netflix comes to Greece ) these will gradually die out..

-The stock price for most of the technology companies that are in the stock market is very cheap , but very few of them have a good prospect in my opinion.. Most of the really big companies are dinosaurs , and sooner or later their clients will find a cheaper and more agile alternative..

-There are , of course , many more companies which focus on websites / hosting / e-communities / advertising etc. BUT this list mainly focuses on business programs/software ( websites are software , I know , but not the kind of software I am discussing here.. )

I have made a small map of the sites that I frequently use and the interconnections are astonishing.! The major “spy entities” on the graph are Google and Facebook , something that comes as no surprise . An also disturbing fact is that adult themed sites report your “preferences” to google so I can only imagine what kind of details a google account must have logged on about you , and all of this in an effort to show you the most targeted commercials possible!
I strongly recommend using this tool just to get a glimpse of the privacy problems that arise..!

Even my website where I have made an effort not to use google analytics or adwords or any other framework that may track visitors , the youtube embeds ( of documentaries and etc ) on my pages give away clues about where the visitor was. The only way to combat this I guess is to host everything on my server but due to the cost of this ( bandwidth ) it is impossible..!

The free and open source group of AUEB ( and me along with it xD ) will join the worldwide protest against ACTA , this Saturday 11/Feb.
The gathering in Athens will take place in Syntagma square at 17:00

Because of the recent economic developments concerning Greece the ACTA treaty is a topic which has received little if no coverage from the Greek Media.

The HELLUG and the Greek pirate party will also participate , so we will be an interesting bunch..

The ACTA agreement in Greek

The ACTA agreement in English

I was very happy to learn about a new political movement called , the Greek Pirate party..
It is the only ( as far as I know ) political entity with these kind of agendas in Greece. The political parties that historically passed laws in Greece where so technologically illiterate that they banned all electronic games ( http://news.cnet.com/2100-1040-956357.html ) “by accident” a few years ago to combat online gambling.

This country needs educated representatives on issues of the digital age , and although I know that most of the older generation voters are “programmed” to vote what their family voted for , gradually I hope for some decent representation on the Greek parliament.!

http://www.pirateparty.gr/

Typical Greek Voter , I believe that these people cant even begin to understand what a pirate party stands for..!

Typical Greek Politician saying in parliament that if the greek national power company stops working that all the computers in the country will lose all their data..

Well , things aren`t going very well in Greece..
Stocks are falling , strikes and riots everyday and a general anxiety and disappointment about where this country is heading. Although I can`t say I belong to a social class directly pressured (yet) by the economic meltdown happening all around ( and if I did I would probably not blog about it ) it is sad to see the pessimism diffused everywhere and especially in everyone aged 23-28 , a generation that has just now reached the point to enter the working force after finishing with the educational cycle of life.
Even if there is unemployment and even if we are the 600euro generation ( a term coined up by Greek media , as it is the average post-reductions monthly wage for most junior positions at Greek companies ) I cant stop but think that I am lucky to be part of it.
People have always had problems and always were tormented , in the past , in the present and will probably continue to do so in the future. But it just isn`t possible for past “primitive” societies to be able to produce men like Plato , Fermat , DaVinci , Kant, Nietzsche and at this day and age with all the wonderful possibilities opened with tools such as the internet to see the public acting so foolishly panicked and such a lack of leadership from the Greek financial and political leaders.
It is this attitude that produces the biggest part of the crisis as members of the Greek community dont trust each other , and don`t even trust themselves.
And its a natural consequence that when people fail to stand up to a crisis as units they will also fail as a group.

This is my first real post , apart for blogs about technical details of work I’ve done and I don`t want to babble a lot.

In a few words I wish that people would realize the possibilities laid before them and grab life by the throat instead of passively whine about it and blame everyone else.

I guess it is a gift most people lack, to be able to see possibility where most people don`t..

Some Greek shows which featured us , live on air..
GuarddoG @ Robotics Exhibition – 76η ΔΕΘ 13-9-2011 , Ant1 Ellate
GuarddoG @ Robotics Exhibition – 76η ΔΕΘ 13-9-2011 , SKAI τώρα
GuarddoG @ Robotics Exhibition – 76η ΔΕΘ 13-9-2011 , Alpha Ειδήσεις

The GuarddoG project will be part of the 76th International Fair of Thessaloniki , at the Innovation and Inventions event..

IFT is the largest international exhibition in the country , so this is very important , and although the new cameras are not installed and the chassis is looking , well kind of ragged , I still hope to give a good show …

http://www.helexpo.gr/default.aspx?lang=en-US&loc=1&page=2065