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• Best computer-science universities in Europe?

  - by Tom

  I am in 11th grade and only one year left when I finish my school. I am sure I want to dedicate my life to programming. In my country the education's level is not so high as in Europe, so I want to emigrate and study not just for a diploma, but for knowledge too. So, what universities would you suggest me which has subject Computer-Science? I prefer web programming. Please do not delete this message though it is quite offtopic, but it's the best place for me to get suggestions from advanced programmers who have already finished their university. And I hope here comes also teenagers who can make the best decision choosing university. Thank you. Please read the whole my message before voting to close this thread, thanks.

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• How to monitor MySQL query errors, timeouts and logon attempts?

  - by Abel

  While setting up a third party closed source CMS (Sitefinity) the setup doesn't create all tables and procedures necessary to run it. The software lacks a logging system itself and it made me wonder: could I trace and monitor failing SQL statements from MySQL? This serves more than only the purpose of solving my issue with Sitefinity. More often I wonder what's send to the MySQL server, not wanting to dive into the software products or setup a debugging environment etc. I tried JetProfiler (only performance) and looked through a few others, but although they monitor a lot, they don't monitor query failures, timeouts or logon attempts. Does anyone know a profiler, tracer, monitoring tool, commercial or free, that can show me this information?

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• "Out of Memory" error in Lotus Notes automation from VBA

  - by PowerUser

  This VBA function sporadically fails with a Notes automation error "Run-Time Error '7' Out of Memory". Naturally, when I try to manually reproduce it, everything runs fine. Function ToGMT(ByVal X As Date) As Date Static NtSession As NotesSession If NtSession Is Nothing Then Set NtSession = New NotesSession NtSession.Initialize End If (do stuff) End function To put this in context, this VBA function is being called by an Access query, 3-4 times per record, with 20,000 records. For performance reasons, the NotesSession has been made static. Any ideas why it is sporadically giving an out-of-memory error? (Also, I'm initiating the NotesSession just so I can convert a datetime to GMT using Lotus's rules. If you know a better way, I'm listening).

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• Rss Feed for youtube channel?

  - by Praveen Chandrasekaran

  Suggest me to how to get the HD video url for the youtube channel uploads as a RSS Feed. its to play on android phones. the formats should be Format File Type H.263 3GPP (.3gp) and MPEG-4 (.mp4) H.264 AVC 3GPP (.3gp) and MPEG-4 (.mp4) MPEG-4 SP 3GPP (.3gp) if i use this link: http://gdata.youtube.com/feeds/api/users/youtube/uploads i get only the 3gpp format media-content tag? i want high definition mp4 video link. resolution must be 320X480.How can i? Any Idea?

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• Trying to reduce the speed overhead of an almost-but-not-quite-int number class

  - by Fumiyo Eda

  I have implemented a C++ class which behaves very similarly to the standard int type. The difference is that it has an additional concept of "epsilon" which represents some tiny value that is much less than 1, but greater than 0. One way to think of it is as a very wide fixed point number with 32 MSBs (the integer parts), 32 LSBs (the epsilon parts) and a huge sea of zeros in between. The following class works, but introduces a ~2x speed penalty in the overall program. (The program includes code that has nothing to do with this class, so the actual speed penalty of this class is probably much greater than 2x.) I can't paste the code that is using this class, but I can say the following: +, -, +=, <, > and >= are the only heavily used operators. Use of setEpsilon() and getInt() is extremely rare. * is also rare, and does not even need to consider the epsilon values at all. Here is the class: #include <limits> struct int32Uepsilon { typedef int32Uepsilon Self; int32Uepsilon () { _value = 0; _eps = 0; } int32Uepsilon (const int &i) { _value = i; _eps = 0; } void setEpsilon() { _eps = 1; } Self operator+(const Self &rhs) const { Self result = *this; result._value += rhs._value; result._eps += rhs._eps; return result; } Self operator-(const Self &rhs) const { Self result = *this; result._value -= rhs._value; result._eps -= rhs._eps; return result; } Self operator-( ) const { Self result = *this; result._value = -result._value; result._eps = -result._eps; return result; } Self operator*(const Self &rhs) const { return this->getInt() * rhs.getInt(); } // XXX: discards epsilon bool operator<(const Self &rhs) const { return (_value < rhs._value) || (_value == rhs._value && _eps < rhs._eps); } bool operator>(const Self &rhs) const { return (_value > rhs._value) || (_value == rhs._value && _eps > rhs._eps); } bool operator>=(const Self &rhs) const { return (_value >= rhs._value) || (_value == rhs._value && _eps >= rhs._eps); } Self &operator+=(const Self &rhs) { this->_value += rhs._value; this->_eps += rhs._eps; return *this; } Self &operator-=(const Self &rhs) { this->_value -= rhs._value; this->_eps -= rhs._eps; return *this; } int getInt() const { return(_value); } private: int _value; int _eps; }; namespace std { template<> struct numeric_limits<int32Uepsilon> { static const bool is_signed = true; static int max() { return 2147483647; } } }; The code above works, but it is quite slow. Does anyone have any ideas on how to improve performance? There are a few hints/details I can give that might be helpful: 32 bits are definitely insufficient to hold both _value and _eps. In practice, up to 24 ~ 28 bits of _value are used and up to 20 bits of _eps are used. I could not measure a significant performance difference between using int32_t and int64_t, so memory overhead itself is probably not the problem here. Saturating addition/subtraction on _eps would be cool, but isn't really necessary. Note that the signs of _value and _eps are not necessarily the same! This broke my first attempt at speeding this class up. Inline assembly is no problem, so long as it works with GCC on a Core i7 system running Linux!

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• P/Invoke or C++/CLI for wrapping a C library

  - by Ian G

  Have a moderate size (40-odd function) C API that needs to be called from a C# project. The functions logically break up to form a few classes that will be API presented to the rest of the project. Are there any objective reasons to prefer P/Invoke or C++/CLI for the interoperability underneath that API, in terms of robustness, maintainability, deployment, ...? The issues I could think of that might be, but aren't problematic are: C++/CLI will require an separate assembly, the P/Invoke classes can be in the main assembly. (We've already got multiple assemblies and there'll be the C dlls anyway so not a major issue). Performance doesn't seem differ noticeable between the two methods. Issues that I'm not sure about are: My feeling is C++/CLI will be easier to debug if there's inter-op problem, is this true? Language familiarity enough people know C# and C++ but knowledge of details of C++/CLI are rarer here. Anything else?

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• Will GTK's pango and cairo work well in Cocoa and MFC applications.

  - by Lothar

  I'm writing a GUI program and decided to go native on all platforms. But for all the stuff i need to draw myself i would like to use the same drawing routines because font and unicode handling is so difficult and complex. Do you see any negative points in useing Pango/Cairo. Well on MacOSX i havent succeded installing Pango/Cairo yet. Looks like a bad Omen. I would also like to hear about the performance penality. The first time i looked at Pango i thought, yes thats the reason why Software is still getting despite better hardware.

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• How do I draw an ellipse with arbitrary orientation pixel by pixel?

  - by amc

  Hi, I have to draw an ellipse of arbitrary size and orientation pixel by pixel. It seems pretty easy to draw an ellipse whose major and minor axes align with the x and y axes, but rotating the ellipse by an arbitrary angle seems trickier. Initially I though it might work to draw the unrotated ellipse and apply a rotation matrix to each point, but it seems as though that could cause errors do to rounding, and I need rather high precision. Is my suspicion about this method correct? How could I accomplish this task more precisely? I'm programming in C++ (although that shouldn't really matter since this is a more algorithm-oriented question).

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• Is Pex (Test generation) really usefull tool?

  - by Yauheni Sivukha

  Yes, it is possible to generate tests on boundary values for functions like "Sum" or "Divide". Pex is a good tool here. But more often we create tests on business behaviour. Let's consider example from classic Beck's tdd book: [Test] public void ShouldRoundOnCreation() { Money money = new Money(20.678); Assert.AreEqual(20.68,money.Amount); Assert.AreEqual(2068,money.Cents); } Can this test be generated? No :) 95 % of tests in my projects check business logic, and can not be generated. Pex (Especially in pair with Moles) can give 100% code coverage, but a high code coverage rate of a test suite does never indicate, that code is well tested - It only gives false confidence that everything is tested. And this is very dangerous. So, the question is - Is Pex really usefull tool?

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• What are your favorite extension methods for C#/.NET? (codeplex.com/extensionoverflow)

  - by bovium

  Let's make a list of answers where you post your excellent and favorite extension methods. The requirement is that the full code must be posted and a example and an explanation on how to use it. Based on the high interest in this topic I have setup an Open Source Project called extensionoverflow on Codeplex. Please mark your answers with an acceptance to put the code in the Codeplex project. Please post the full sourcecode and not a link. Codeplex News: 11.11.2008 XmlSerialize / XmlDeserialize is now Implemented and Unit Tested. 11.11.2008 There is still room for more developers. ;-) Join NOW! 11.11.2008 Third contributer joined ExtensionOverflow, welcome to BKristensen 11.11.2008 FormatWith is now Implemented and Unit Tested. 09.11.2008 Second contributer joined ExtensionOverflow. welcome to chakrit. 09.11.2008 We need more developers. ;-) 09.11.2008 ThrowIfArgumentIsNull in now Implemented and Unit Tested on Codeplex.

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• Javscript filter vs map problem

  - by graham.reeds

  As a continuation of my min/max across an array of objects I was wondering about the performance comparisons of filter vs map. So I put together a test on the values in my code as was going to look at the results in FireBug. This is the code: var _vec = this.vec; min_x = Math.min.apply(Math, _vec.filter(function(el){ return el["x"]; })); min_y = Math.min.apply(Math, _vec.map(function(el){ return el["x"]; })); The mapped version returns the correct result. However the filtered version returns NaN. Breaking it out, stepping through and finally inspecting the results, it would appear that the inner function returns the x property of _vec but the actual array returned from filter is the unfiltered _vec. I believe my usage of filter is correct - can anyone else see my problem?

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• Asp .Net MVC Viewmodel should be class or struct?

  - by Jonas Everest

  Hey guys, I have just been thinking about the concept of view model object we create in asp.net MVC. Our purpose is to instantiate it and pass it from controller to view and view read it and display the data. Those view model are usually instantiated through constructor. We won't need to initialize the members, we may not need to redefine/override parameterless constructor and we don't need inheritance feature there. So, why don't we use struct type for our view model instead of class. It will enhance the performance.

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• Possible to InvalidateVisual() on a given region instead of entire WPF control?

  - by Scott Bilas

  I have a complex WPF control that draws a lot of primitives in its OnRender (it's sort of like a map). When a small portion of it changes, I'd only like to re-issue render commands for the affected elements, instead of running the entire OnRender over. While I'm fine with my OnRender function's performance on a resize or whatever, it's not fast enough for mouse hover-based highlighting of primitives. Currently the only way I know how to force a screen update is to call InvalidateVisual(). No way to send in a dirty rect region to invalidate. Is the lowest granularity of WPF screen composition the UI element? Will I need to do my renders of primitives into an intermediate target and then have that use InvalidateVisual() to update to the screen?

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• What languages allow cross-platform native executables to be created?

  - by JT

  I'm frustrated to discover that Java lacks an acceptable solution for creating programs that will run via double-click. Other than .NET for Windows, what modern and high-level programming languages can I write code in that can be compiled for various platforms and run as a native/binary in each (Windows, Linux, OSX (optional)) Assuming I wanted to write code in python, for instance, is there a cohesive way that I could distribute my software which wouldn't require users to do anything special to get it to run? I want to write and distribute software for computer-illiterate and Java has turned out to be a real pain in this respect.

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• Copying data from STDOUT to a remote machine using SFTP

  - by freddie

  In order to backup large database partitions to a remote machine using SFTP, I'd like to use the databases dump command and send it directly over using SFTP to a remote location. This is useful when needing to dump large data sets when you don't have enough local disk space to create the backup file, and then copy it to a remote location. I've tried using python + paramiko which provides this functionality, but the performance much worse than using the native openssh/sftp binary to transfer files. Does anyone have any idea on how to do this either with the native sftp client on linux, or some library like paramiko? (but one that performs close to the native sftp client)?

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• foreign key constraints on primary key columns - issues ?

  - by zzzeek

  What are the pros/cons from a performance/indexing/data management perspective of creating a one-to-one relationship between tables using the primary key on the child as foreign key, versus a pure surrogate primary key on the child? The first approach seems to reduce redundancy and nicely constrains the one-to-one implicitly, while the second approach seems to be favored by DBAs, even though it creates a second index: create table parent ( id integer primary key, data varchar(50) ) create table child ( id integer primary key references parent(id), data varchar(50) ) pure surrogate key: create table parent ( id integer primary key, data varchar(50) ) create table child ( id integer primary key, parent_id integer unique references parent(id), data varchar(50) ) the platforms of interest here are Postgresql, Microsoft SQL Server.

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• Java 2D clip area to shape

  - by user2923880

  I'm quite new to graphics in java and I'm trying to create a shape that clips to the bottom of another shape. Here is an example of what I'm trying to achieve: Where the white line at the base of the shape is the sort of clipped within the round edges. The current way I am doing this is like so: g2.setColor(gray); Shape shape = getShape(); //round rectangle g2.fill(shape); Rectangle rect = new Rectangle(shape.getBounds().x, shape.getBounds().y, width, height - 3); Area area = new Area(shape); area.subtract(new Area(rect)); g2.setColor(white); g2.fill(area); I'm still experimenting with the clip methods but I can't seem to get it right. Is this current method ok (performance wise, since the component repaints quite often) or is there a more efficient way? Thanks in advance.

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• how to translate Haskell into Scalaz?

  - by TOB

  One of my high school students and I are going to try to do a port of Haskell's Parsec parser combinator library into Scala. (It has the advantage over Scala's built-in parsing library that you can pass state around fairly easily because all the parsers are monads.) The first hitch I've come across is trying to figure out how Functor works in scalaz. Can someone explain how to convert this Haskell code: data Reply s u a = Ok a !(State s u) ParseError | Error ParseError instance Functor (Reply s u) where fmap f (Ok x s e) = Ok (f x) s e fmap _ (Error e) = Error e -- XXX into Scala (using Scalaz, I assume). I got as far as sealed abstract class Reply[S, U, A] case class Ok[S, U, A](a: A, state: State[S, U], error: ParseError) extends Reply[S, U, A] case class Error[S, U, A](error: ParseError) extends Reply[S, U, A] and know that I should make Reply extend the scalaz.Functor trait, but I can't figure out how to do that. (Mostly I'm having trouble figuring out what the F[_] parameter does.) Any help appreciated! Thanks, Todd

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• Thread.sleep vs Monitor.Wait vs RegisteredWaitHandle?

  - by Royi Namir

  (the following items has different goals , but im interesting knowing how they "PAUSEd") questions Thread.sleep - Does it impact performance on a system ?does it tie up a thread with its wait ? what about Monitor.Wait ? what is the difference in the way they "wait"? do they tie up a thread with their wait ? what aboutRegisteredWaitHandle ? This method accepts a delegate that is executed when a wait handle is signaled. While it’s waiting, it doesn’t tie up a thread. so some thread are paused and can be woken by a delegate , while others just wait ? spin ? can someone please make things clearer ? edit http://www.albahari.com/threading/part2.aspx

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• What format do I use to store a relatively small amount of user data

  - by wcm

  I am writing a small program for our local high school (pro bono). The program has an interface allows the user to enter school holidays. This is a simple stand alone Windows app. What format should I use to store the data? A big relational data is obviously overkill. My initial plan was to store the data in an XML file. Co-workers have been suggesting that I use JSON files, Access Databases, SQL Lite, and SQL Server Express. There was even a suggestion of old school INI files.

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• How to reliably measure available memory in Linux?

  - by Alex B

  Linux /proc/meminfo shows a number of memory usage statistics. MemTotal: 4040732 kB MemFree: 23160 kB Buffers: 163340 kB Cached: 3707080 kB SwapCached: 0 kB Active: 1129324 kB Inactive: 2762912 kB There is quite a bit of overlap between them. For example, as far as I understand, there can be active page cache (belongs to "cached" and "active") and inactive page cache ("inactive" + "cached"). What I want to do is to measure "free" memory, but in a way that it includes used pages that are likely to be dropped without a significant impact on overall system's performance. At first, I was inclined to use "free" + "inactive", but Linux's "free" utility uses "free" + "cached" in its "buffer-adjusted" display, so I am curious what a better approach is. When the kernel runs out of memory, what is the priority of pages to drop and what is the more appropriate metric to measure available memory?

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• NHibernate parent-childs save redundant sql update executed

  - by Broken Pipe

  I'm trying to save (insert) parent object with a collection of child objects, all objects are new. I prefer to manually specify what to save\update and when so I do not use any cascade saves in mappings and flush sessions by myself. So basically I save this object graph like: session.Save(Parent) foreach (var child in Parent.Childs) { session.Save(child); } session.Flush() I expect this code to insert Parent row, then each child row, however NHibernate executes this SQL: INSERT INTO PARENT.... INSERT INTO CHILD .... UPDATE CHILD SET ParentId=@1 WHERE Id=@2 This update statement is absolutely unnecessary, ParentId was already set correctly in INSERT. How do I get rid of it? Performance is very important for me.

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• Hibernate criteria with projection not performing query for @OneToMany mapping

  - by Josh

  I have a domain object, Expense, that has a field called initialFields. It's annotated as so: @OneToMany(fetch = FetchType.EAGER, cascade = { CascadeType.ALL }, orphanRemoval = true) @JoinTable(blah blah) private final List<Field> initialFields; Now I'm trying to use Projections in order to only pull certain fields for performance reasons, but when doing so the initialFields field is always null. It's the only OneToMany field and the only field I am trying to retrieve with the projection that is behaving this way. If I use a regular HQL query initialFields is populated appropriately, but of course I can't limit the fields. Anyone ever seen anything like this?

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• Programatically determining maximum transfer rate

  - by dauphic

  I have a problem that requires me to calculate the maximum upload and download available, then limit my program's usage to a percentage of it. However, I can't think of a good way to find the maximums. At the moment, the only solution I can come up with is transfering a few megabytes between the client and server, then measuring how ling the transfer took. This solution is very undesirable, however, because with 100,000 clients it could potentially result in too much of an increase to our server's bandwidth usage (which is already too high). Does anyone have any solutions to this problem?

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• Is ReaderWriterLockSlim.EnterUpgradeableReadLock() essentially the same as Monitor.Enter()?

  - by Neil Barnwell

  So I have a situation where I may have many, many reads and only the occasional write to a resource shared between multiple threads. A long time ago I read about ReaderWriterLock, and have read about ReaderWriterGate which attempts to mitigate the issue where many writes coming in trump reads and hurt performance. However, now I've become aware of ReaderWriterLockSlim... From the docs, I believe that there can only be one thread in "upgradeable mode" at any one time. In a situation where the only access I'm using is EnterUpgradeableReadLock() (which is appropriate for my scenario) then is there much difference to just sticking with lock(){}? Here's the excerpt: A thread that tries to enter upgradeable mode blocks if there is already a thread in upgradeable mode, if there are threads waiting to enter write mode, or if there is a single thread in write mode. Or, does the recursion policy make any difference to this?

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