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• Single Responsibility Principle vs Anemic Domain Model anti-pattern

  - by Niall Connaughton

  I'm in a project that takes the Single Responsibility Principle pretty seriously. We have a lot of small classes and things are quite simple. However, we have an anemic domain model - there is no behaviour in any of our model classes, they are just property bags. This isn't a complaint about our design - it actually seems to work quite well During design reviews, SRP is brought out whenever new behaviour is added to the system, and so new behaviour typically ends up in a new class. This keeps things very easily unit testable, but I am perplexed sometimes because it feels like pulling behaviour out of the place where it's relevant. I'm trying to improve my understanding of how to apply SRP properly. It seems to me that SRP is in opposition to adding business modelling behaviour that shares the same context to one object, because the object inevitably ends up either doing more than one related thing, or doing one thing but knowing multiple business rules that change the shape of its outputs. If that is so, then it feels like the end result is an Anemic Domain Model, which is certainly the case in our project. Yet the Anemic Domain Model is an anti-pattern. Can these two ideas coexist? EDIT: A couple of context related links: SRP - http://www.objectmentor.com/resources/articles/srp.pdf Anemic Domain Model - http://martinfowler.com/bliki/AnemicDomainModel.html I'm not the kind of developer who just likes to find a prophet and follow what they say as gospel. So I don't provide links to these as a way of stating "these are the rules", just as a source of definition of the two concepts.

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• Manage multiple UDP calls

  - by rayman

  Hi all, I would like to have an advice for this issue: I am using Jbos 5.1.0, EJB3.0 I have system, which sending requests via UDP'S to remote modems, and suppose to wait for an answer from the target modem. the remote modems support only UDP calls, therefor I o design asynchronous mechanism. (also coz I want to request X modems parallel) this is what I try to do: all calls are retrieved from Data Base, then each call will be added as a message to JMS QUE. let's say i will set X MDB'S on that que, so I can work asynchronous. now each MDB will send UDP request to the IP-address(remote modem) which will be parsed from the que message. so basicly each MDB, which takes a message is sending a udp request to the remote modem and [b]waiting [/b]for an answer from that modem. [u]now here is the BUG:[/u] could happen a scenario where MDB will get an answer, but not from the right modem( which it requested in first place). that bad scenario cause two wrong things: a. the sender which sent the message will wait forever since the message never returned to him(it got accepted by another MDB). b. the MDB which received the message is not the right one, and probablly if it was on a "listener" mode, then it supposed to wait for an answer from diffrent sender.(else it wouldnt get any messages) so ofcourse I can handle everything with a RETRY mechanisem. so both mdb's(the one who got message from the wrong sender, and the one who never got the answer) will try again, to do thire operation with a hope that next time it will success. This is the mechanism, mybe you could tell me if there is any design pattren, or any other effective solution for this problem? Thanks, ray.

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• Testing subpackage modules in Python 3

  - by Mitchell Model

  I have been experimenting with various uses of hierarchies like this and the differences between absolute and relative imports, and can't figure out how to do routine things with the package, subpackages, and modules without simply putting everything on sys.path. I have a two-level package hierarchy: MyApp __init__.py Application __init__.py Module1 Module2 ... Domain __init__.py Module1 Module2 ... UI __init__.py Module1 Module2 ... I want to be able to do the following: Run test code in a Module's "if main" when the module imports from other modules in the same directory. Have one or more test code modules in each subpackage that runs unit tests on the modules in the subpackage. Have a set of unit tests that reside in someplace reasonable, but outside the subpackages, either in a sibling package, at the top-level package, or outside the top-level package (though all these might end up doing is running the tests in each subpackage) "Enter" the structure from any of the three subpackage levels, e.g. run code that just uses Domain modules, run code that just uses Application modules, but Application uses code from both Application and Domain modules, and run code from GUI uses code from both GUI and Application; for instance, Application test code would import Application modules but not Domain modules. After developing the bulk of the code without subpackages, continue developing and testing after organizing the modules into this hierarchy. I know how to use relative imports so that external code that puts MyApp on its sys.path can import MyApp, import any subpackages it wants, and import things from their modules, while the modules in each subpackage can import other modules from the same subpackage or from sibling packages. However, the development needs listed above seem incompatible with subpackage structuring -- in other words, I can't have it both ways: a well-structured multi-level package hierarchy used from the outside and also used from within, in particular for testing but also because modules from one design level (in particular the UI) should not import modules from a design level below the next one down. Sorry for the long essay, but I think it fairly represents the struggles a lot of people have been having adopting to the new relative import mechanisms.

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• Using CURL within a loop to download a file, 1st one works, 2nd one times out

  - by kitenski

  Morning all, I am using CURL to download an image file within a loop. The first time it runs fine and I see the image appear in the directory. The second time it fails with a timeout, despite it being a valid URL. Can anyone suggest why it always fails on the 2nd time and how to fix it? The snippet of code is: // download image $extension = "gif"; $ch = curl_init(); curl_setopt($ch, CURLOPT_TIMEOUT, 90); curl_setopt($ch, CURLOPT_URL, $imgurl); curl_setopt($ch, CURLOPT_RETURNTRANSFER, true); curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true); echo $imgurl . " attempting to open URL "; $i = curl_exec($ch); if ( $i==false ) { echo curl_errno($ch).' '.curl_error($ch); } $image_name=time().'.'.$extension; $f = fopen('/fulldirectorypath/' . $image_name ,'w+'); fwrite($f,$i); fclose($f); I have put an echo in there to display the $IMGURL, to check it is valid, and upped the timeout to 90 secs, but it still fails. This is what I see on screen: http://images.eu-xmedia.de/thumbnails/34555861/5676051/pt=pic,lang=2,origfile=yes/image.gif attempting to open URL 28 Operation timed out after 90 seconds with 0 bytes received an empty file is created in my directory. thanks alot, Greg

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• Atomic swap in GNU C++

  - by Steve

  I want to verify that my understanding is correct. This kind of thing is tricky so I'm almost sure I am missing something. I have a program consisting of a real-time thread and a non-real-time thread. I want the non-RT thread to be able to swap a pointer to memory that is used by the RT thread. From the docs, my understanding is that this can be accomplished in g++ with: // global Data *rt_data; Data *swap_data(Data *new_data) { #ifdef __GNUC__ // Atomic pointer swap. Data *old_d = __sync_lock_test_and_set(&rt_data, new_data); #else // Non-atomic, cross your fingers. Data *old_d = rt_data; rt_data = new_data; #endif return old_d; } This is the only place in the program (other than initial setup) where rt_data is modified. When rt_data is used in the real-time context, it is copied to a local pointer. For old_d, later on when it is sure that the old memory is not used, it will be freed in the non-RT thread. Is this correct? Do I need volatile anywhere? Are there other synchronization primitives I should be calling? By the way I am doing this in C++, although I'm interested in whether the answer differs for C. Thanks ahead of time.

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• How to rename goals in Maven?

  - by mjs

  In the Maven document Introduction to the Build Lifecycle, a goal of display:time is described that outputs the current time. The plugin is as follows: ... <plugin> <groupId>com.mycompany.example</groupId> <artifactId>maven-touch-plugin</artifactId> <version>1.0</version> <executions> <execution> <phase>process-test-resources</phase> <goals> <goal>timestamp</goal> </goals> </execution> </executions> </plugin> ... I have several questions relating to this plugin: How can I change the name of the goal to, for example, foo:bar? (Why does neither display nor time appear anywhere in the XML fragment? How can you tell, from looking at the fragment, what goals it defines?) How can I manually run this goal? (For similar constructs, the equivalent of mvn display:time sometimes works, but this doesn't work consistently.) How can I see if this goal exists? (i.e. list available goals; this question suggests this is impossible.)

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• Python: circular imports needed for type checking

  - by phild

  First of all: I do know that there are already many questions and answers to the topic of the circular imports. The answer is more or less: "Design your Module/Class structure properly and you will not need circular imports". That is true. I tried very hard to make a proper design for my current project, I in my opinion I was successful with this. But my specific problem is the following: I need a type check in a module that is already imported by the module containing the class to check against. But this throws an import error. Like so: foo.py: from bar import Bar class Foo(object): def __init__(self): self.__bar = Bar(self) bar.py: from foo import Foo class Bar(object): def __init__(self, arg_instance_of_foo): if not isinstance(arg_instance_of_foo, Foo): raise TypeError() Solution 1: If I modified it to check the type by a string comparison, it will work. But I dont really like this solution (string comparsion is rather expensive for a simple type check, and could get a problem when it comes to refactoring). bar_modified.py: from foo import Foo class Bar(object): def __init__(self, arg_instance_of_foo): if not arg_instance_of_foo.__class__.__name__ == "Foo": raise TypeError() Solution 2: I could also pack the two classes into one module. But my project has lots of different classes like the "Bar" example, and I want to seperate them into different module files. After my own 2 solutions are no option for me: Has anyone a nicer solution for this problem?

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• UIDatePicker date method is picking wrong date: iPhone Dev

  - by prd

  Hi, I am getting very strange behaviour on UIDatePicker. I have a view with date picker declared in .h file as IBOutlet UIDatePicker *datePicker; with property nonatomic and retain. datePicker is properly linked in IB file. In the code I am setting the minimum, maximum, initial date and action to call for UICOntrolEventValueChanged using following code If (!currentDate) { initialDate = [NSDate date]; } else { initialDate = currentdate; } [datePicker setMinimumDate:[NSDate date]]; [datePicker setMaximumDate:[[NSDate date] addTimeInterval:5 * 365.25 * 24 * 60 * 60]]; // to get upto 5 years [datePicker setDate:initialDate animated:YES]; [datePicker addTarget:self action:@selector(getDatePickerValue:) forControlEvents:UIControlEventValueChanged]; In getDatePickerValue, I get the new date using datePicker.date. When the view is closed (using a done button), I get the current value of the date using datePicker.date. Now if the view is called with no 'currentDate', the picker returns 'todays date'. This is what happens the 'first' time my pickerView is called. Each subsequent call to the view, with no 'current date' gives me a different and later date from today. So, first time I get today's date say 9 Jun 2010 second time datePicker.date returns 10 Jun 2010 third time 11 Jun 2010 and so on. Though its not always incremental, but mostly it is. I have put NSLogs, and verified the initial date is set correctly. The problem is only on the device (on OS 3.0), the issue is not replicated on simulator. I can't find what I have done wrong. I hope somebody else has come across similar problem and can help me resolve this.

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• Is my objective possible using WCF (and is it the right way to do things?)

  - by David

  I'm writing some software that modifies a Windows Server's configuration (things like MS-DNS, IIS, parts of the filesystem). My design has a server process that builds an in-memory object graph of the server configuration state and a client which requests this object graph. The server would then serialize the graph, send it to the client (presumably using WCF), the server then makes changes to this graph and sends it back to the server. The server receives the graph and proceeds to make modifications to the server. However I've learned that object-graph serialisation in WCF isn't as simple as I first thought. My objects have a hierarchy and many have parametrised-constructors and immutable properties/fields. There are also numerous collections, arrays, and dictionaries. My understanding of WCF serialisation is that it requires use of either the XmlSerializer or DataContractSerializer, but DCS places restrictions on the design of my object-graph (immutable data seems right-out, it also requires parameter-less constructors). I understand XmlSerializer lets me use my own classes provided they implement ISerializable and have the de-serializer constructor. That is fine by me. I spoke to a friend of mine about this, and he advocates going for a Data Transport Object-only route, where I'd have to maintain a separate DataContract object-graph for the transport of data and re-implement my server objects on the client. Another friend of mine said that because my service only has two operations ("GetServerConfiguration" and "PutServerConfiguration") it might be worthwhile just skipping WCF entirely and implementing my own server that uses Sockets. So my questions are: Has anyone faced a similar problem before and if so, are there better approaches? Is it wise to send an entire object graph to the client for processing? Should I instead break it down so that the client requests a part of the object graph as it needs it and sends only bits that have changed (thus reducing concurrency-related risks?)? If sending the object-graph down is the right way, is WCF the right tool? And if WCF is right, what's the best way to get WCF to serialise my object graph?

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• Why does Microsoft advise against readonly fields with mutable values?

  - by Weeble

  In the Design Guidelines for Developing Class Libraries, Microsoft say: Do not assign instances of mutable types to read-only fields. The objects created using a mutable type can be modified after they are created. For example, arrays and most collections are mutable types while Int32, Uri, and String are immutable types. For fields that hold a mutable reference type, the read-only modifier prevents the field value from being overwritten but does not protect the mutable type from modification. This simply restates the behaviour of readonly without explaining why it's bad to use readonly. The implication appears to be that many people do not understand what "readonly" does and will wrongly expect readonly fields to be deeply immutable. In effect it advises using "readonly" as code documentation indicating deep immutability - despite the fact that the compiler has no way to enforce this - and disallows its use for its normal function: to ensure that the value of the field doesn't change after the object has been constructed. I feel uneasy with this recommendation to use "readonly" to indicate something other than its normal meaning understood by the compiler. I feel that it encourages people to misunderstand the meaning of "readonly", and furthermore to expect it to mean something that the author of the code might not intend. I feel that it precludes using it in places it could be useful - e.g. to show that some relationship between two mutable objects remains unchanged for the lifetime of one of those objects. The notion of assuming that readers do not understand the meaning of "readonly" also appears to be in contradiction to other advice from Microsoft, such as FxCop's "Do not initialize unnecessarily" rule, which assumes readers of your code to be experts in the language and should know that (for example) bool fields are automatically initialised to false, and stops you from providing the redundancy that shows "yes, this has been consciously set to false; I didn't just forget to initialize it". So, first and foremost, why do Microsoft advise against use of readonly for references to mutable types? I'd also be interested to know: Do you follow this Design Guideline in all your code? What do you expect when you see "readonly" in a piece of code you didn't write?

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• How can I track the last location of a shipment effeciently using latest date of reporting?

  - by hash

  I need to find the latest location of each cargo item in a consignment. We mostly do this by looking at the route selected for a consignment and then finding the latest (max) time entered against nodes of this route. For example if a route has 5 nodes and we have entered timings against first 3 nodes, then the latest timing (max time) will tell us its location among the 3 nodes. I am really stuck on this query regarding performance issues. Even on few hundred rows, it takes more than 2 minutes. Please suggest how can I improve this query or any alternative approach I should acquire? Note: ATA= Actual Time of Arrival and ATD = Actual Time of Departure SELECT DISTINCT(c.id) as cid,c.ref as cons_ref , c.Name, c.CustRef FROM consignments c INNER JOIN routes r ON c.Route = r.ID INNER JOIN routes_nodes rn ON rn.Route = r.ID INNER JOIN cargo_timing ct ON c.ID=ct.ConsignmentID INNER JOIN (SELECT t.ConsignmentID, Max(t.firstata) as MaxDate FROM cargo_timing t GROUP BY t.ConsignmentID ) as TMax ON TMax.MaxDate=ct.firstata AND TMax.ConsignmentID=c.ID INNER JOIN nodes an ON ct.routenodeid = an.ID INNER JOIN contract cor ON cor.ID = c.Contract WHERE c.Type = 'Road' AND ( c.ATD = 0 AND c.ATA != 0 ) AND (cor.contract_reference in ('Generic','BP001','020-543-912')) ORDER BY c.ref ASC

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• Family Tree :- myheritage.com

  - by Nitesh Panchal

  Hello, The other day i just accidently visited the site myheritage.com. I was just wondering, how they must have created one? Can anybody tell me what can be their database design? and if possible, algorithm that we can use to generate such a tree? Generating simple binary tree is very easy using recursion. But if you have a look at the site(if you have time please make account on it and add few nodes to feel) when we add son to a father, it's mother is automatically added(if you don't add explicitly). Mother's family tree is also generated side by side and many such fancy things are happening. In a simple binary tree we have a root node and then many nodes below it. Thus we cannot show wife and husband in the tree and then show a line from wife and husband to child. In spare time, can anybody discuss what can be it's database design and the recursive algorithm that we can follow to generate it? I hope i am not asking too much from you :).

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• How to interrupt a thread performing a blocking socket connect?

  - by Jason R

  I have some code that spawns a pthread that attempts to maintain a socket connection to a remote host. If the connection is ever lost, it attempts to reconnect using a blocking connect() call on its socket. Since the code runs in a separate thread, I don't really care about the fact that it uses the synchronous socket API. That is, until it comes time for my application to exit. I would like to perform some semblance of an orderly shutdown, so I use thread synchronization primitives to wake up the thread and signal for it to exit, then perform a pthread_join() on the thread to wait for it to complete. This works great, unless the thread is in the middle of a connect() call when I command the shutdown. In that case, I have to wait for the connect to time out, which could be a long time. This makes the application appear to take a long time to shut down. What I would like to do is to interrupt the call to connect() in some way. After the call returns, the thread will notice my exit signal and shut down cleanly. Since connect() is a system call, I thought that I might be able to intentionally interrupt it using a signal (thus making the call return EINTR), but I'm not sure if this is a robust method in a POSIX threads environment. Does anyone have any recommendations on how to do this, either using signals or via some other method? As a note, the connect() call is down in some library code that I cannot modify, so changing to a non-blocking socket is not an option.

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• How would i down-sample a .wav file then reconstruct it using nyquist? - in MATLAB

  - by Andrew

  This is all done in MATLAB 2010 My objective is to show the results of: undersampling, nyquist rate/ oversampling First i need to downsample the .wav file to get an incomplete/ or impartial data stream that i can then reconstuct. Heres the flow chart of what im going to be doing So the flow is analog signal - sampling analog filter - ADC - resample down - resample up - DAC - reconstruction analog filter what needs to be achieved: F= Frequency F(Hz=1/s) E.x. 100Hz = 1000 (Cyc/sec) F(s)= 1/(2f) Example problem: 1000 hz = Highest frequency 1/2(1000hz) = 1/2000 = 5x10(-3) sec/cyc or a sampling rate of 5ms This is my first signal processing project using matlab. what i have so far. % Fs = frequency sampled (44100hz or the sampling frequency of a cd) [test,fs]=wavread('test.wav'); % loads the .wav file left=test(:,1); % Plot of the .wav signal time vs. strength time=(1/44100)*length(left); t=linspace(0,time,length(left)); plot(t,left) xlabel('time (sec)'); ylabel('relative signal strength') **%this is were i would need to sample it at the different frequecys (both above and below and at) nyquist frequency.*I think.*** soundsc(left,fs) % shows the resaultant audio file , which is the same as original ( only at or above nyquist frequency however) Can anyone tell me how to make it better, and how to do the sampling at verious frequencies?

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• How to benchmark on multi-core processors

  - by Pascal Cuoq

  I am looking for ways to perform micro-benchmarks on multi-core processors. Context: At about the same time desktop processors introduced out-of-order execution that made performance hard to predict, they, perhaps not coincidentally, also introduced special instructions to get very precise timings. Example of these instructions are rdtsc on x86 and rftb on PowerPC. These instructions gave timings that were more precise than could ever be allowed by a system call, allowed programmers to micro-benchmark their hearts out, for better or for worse. On a yet more modern processor with several cores, some of which sleep some of the time, the counters are not synchronized between cores. We are told that rdtsc is no longer safe to use for benchmarking, but I must have been dozing off when we were explained the alternative solutions. Question: Some systems may save and restore the performance counter and provide an API call to read the proper sum. If you know what this call is for any operating system, please let us know in an answer. Some systems may allow to turn off cores, leaving only one running. I know Mac OS X Leopard does when the right Preference Pane is installed from the Developers Tools. Do you think that this make rdtsc safe to use again? More context: Please assume I know what I am doing when trying to do a micro-benchmark. If you are of the opinion that if an optimization's gains cannot be measured by timing the whole application, it's not worth optimizing, I agree with you, but I cannot time the whole application until the alternative data structure is finished, which will take a long time. In fact, if the micro-benchmark were not promising, I could decide to give up on the implementation now; I need figures to provide in a publication whose deadline I have no control over.

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• Representing complex scheduled reoccurance in a database

  - by David Pfeffer

  I have the interesting problem of representing complex schedule data in a database. As a guideline, I need to be able to represent the entirety of what the iCalendar -- ics -- format can represent, but in a database. I'm not actually implementing anything relating to ics, but it gives a good scope of the type of rules I need to be able to model. I need to allow allow representation of a single event or a reoccurring event based on multiple times per day, days of the week, week of a month, month, year, or some combination of those. For example, the third Thursday in November annually, or the 25th of December annually, or every two weeks starting November 2 and continuing until September 8 the following year. I don't care about insertion efficiency but query efficiency is critical. The operation I will be doing most often is providing either a single date/time or a date/time range, and trying to determine if the defined schedule matches any part of the date/time range. Other operations can be slower. For example, given January 15, 2010 at 10:00 AM through January 15, 2010 at 11:00 AM, find all schedules that match at least part of that time. (i.e. a schedule that covers 10:30 - 11:00 still matches.) Any suggestions? I looked at http://stackoverflow.com/questions/1016170/how-would-one-represent-scheduled-events-in-an-rdbms but it doesn't cover the scope of the type of reoccurance rules I'd like to model.

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• Visual Studio 2010: very slow web applications debugging!

  - by micha12

  I recently installed Visual Studio 2010 (Ultimate edition, final version released in April), and found that debugging a web application became very slow (2-3 times slower than in Visual Studio 2008)! I took the same web application and checked the speed of loading of one of its pages in VS 2008 and VS 2010, and compared the time it takes to load the page. I tested it using 2 approaches: 1) debugging under ASP.NET Development Server (by pressing the "Start" button) and 2) using ASP.NET Development Server without debugging (by using the "View in Browser" menu command). And I got the following results for Visual Studio 2008 and 2010. 1) ASP.NET Development Server withoud debugging ("View in Browser"): the speed of page loading is the same in VS 2008 and 2010. 2) Debugging under ASP.NET Development Server ("Start" button): in VS 2010 the page takes more time to load than in VS 2008 - VS 2010 debugging is 2-3 times slower than in VS 2008! 3) At the same time, when debugging a web application in VS 2008, it takes the same time to load the page compared to when using only the "View in Browser" command. That is, VS 2008 debugging does not introduce any overhead to page loading in the web browser! I wanted to make sure that other people have the same problem with slow debugging of web applications in VS 2010. Can this issue be solved by any means? BTW, I am using Windows XP SP3. Thank you.

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• SQL Server performance issue.

  - by Jit

  Hi Friends, I have been trying to analyze performance issue with SQL Server 2005. We have 30 jobs, one for each databases (30 databases, one per each client). The jobs run at early morning at an interval of 5 minutes. When I run the job individually for testing, for most of the databases it finishes in 7 to 9 minutes. But when these jobs run at early morning, I see few jobs taking 2 to 3 hours to finish and the same takes few minutes as mentioned above if ran independently. We dont have any other job scheduled during that time, other than these 30 jobs. If we restart the server then for 2 or so days all the jobs finishes in few minutes, but over the period of time (from 3rd day suddenly), few jobs start taking hours to finish. What could be the possible reason of performance degradation over the period of time? I verified all the SPs and we uses temp tables and I made sure none of the temp table is left without dropping at the end of SP. Let me know what are the possible reasons for such behavior. Appreciate your time and help. Thanks

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• Career Choice in JEE, are EJBs standard?

  - by John Baker

  I have chosen to go the JEE route for a career path but I have been having a hard time determining which core technologies that I need to be most familiar with. I'm at the point I can write web apps without a problem with JSP's and regular servlets using JDBC or some basic Hibernate stuff (I know, HTML, CSS and have used MVC extensively on a number of different platforms). What I'm trying to find out is if there is some standard as far as J2EE technologies go. When I look at most of the Job listings, occasionally you will see someone mention Struts or Spring but rarely do I see any mention of EJB's. So my question is really, are EJB's basically required by most JEE employers? Or are most of them working with POJO's? Is it a mix? I have a hard time figuring out if I should put the majority of my time into Struts, Spring/Hibernate, EJB's, etc. And if I do need to master EJB's what version should I learn? 2.1 or 3.0. 3.0 has some obviously better features but I figure a lot of companies probably chose to write their apps in 2.1 just because it was the standard of the time and now migrating would be a big deal. Any advice on this is greatly appreciated.

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• java GC periodically enters into several full GC cycles

  - by Peter

  Environment: sun JDK 1.6.0_16 vm settings: -XX:+DisableExplicitGC -XX:+UseConcMarkSweepGC -Xms1024 -Xmx1024M -XX:MaxNewSize=448m -XX:NewSize=448m -XX:SurvivorRatio=4(6 also checked) -XX:MaxPermSize=128M OS: windows server 2003 processor: 4 cores of INTEL XEON 5130, 2000 Hz my application description: high intensity of concurrent(java 5 concurrency used) operations completed each time by commit to oracle. it's about 20-30 threads run non stop, doing tasks. application runs in JBOSS web container. My GC starts work normally, I see a lot of small GCs and all that time CPU shows good load, like all 4 cores loaded to 40-50%, CPU graph is stable. Then , after 1 min of good work, CPU starts drop to 0% on 2 cores from 4, it's graph becomes unstable, goes up and down("teeth"). I see, that my threads work slower(I have monitoring), I see that GC starts produce a lot of FULL GC during that time and next 4-5 minutes this situation remains as is, then for short period of time, like 1 minute, it gets back to normal situation, but shortly after that all bad thing repeats. Question: Why I have so frequent full GC??? How to prevent that? I played with SurvivorRatio - does not help. I noticed, that application behaves normally until first FULL GC occurs, while I have enough memory. Then it runs badly. my GC LOG: starts good then long period of FULL GCs(many of them) 1027.861: [GC 942200K-623526K(991232K), 0.0887588 secs] 1029.333: [GC 803279K(991232K), 0.0927470 secs] 1030.551: [GC 967485K-625549K(991232K), 0.0823024 secs] 1030.634: [GC 625957K(991232K), 0.0763656 secs] 1033.126: [GC 969613K-632963K(991232K), 0.0850611 secs] 1033.281: [GC 649899K(991232K), 0.0378358 secs] 1035.910: [GC 813948K(991232K), 0.3540375 secs] 1037.994: [GC 967729K-637198K(991232K), 0.0826042 secs] 1038.435: [GC 710309K(991232K), 0.1370703 secs] 1039.665: [GC 980494K-972462K(991232K), 0.6398589 secs] 1040.306: [Full GC 972462K-619643K(991232K), 3.7780597 secs] 1044.093: [GC 620103K(991232K), 0.0695221 secs] 1047.870: [Full GC 991231K-626514K(991232K), 3.8732457 secs] 1053.739: [GC 942140K(991232K), 0.5410483 secs] 1056.343: [Full GC 991232K-634157K(991232K), 3.9071443 secs] 1061.257: [GC 786274K(991232K), 0.3106603 secs] 1065.229: [Full GC 991232K-641617K(991232K), 3.9565638 secs] 1071.192: [GC 945999K(991232K), 0.5401515 secs] 1073.793: [Full GC 991231K-648045K(991232K), 3.9627814 secs] 1079.754: [GC 936641K(991232K), 0.5321197 secs]

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• NHibernate. DTO -> Domain

  - by Andrew Kalashnikov

  Hello guys. I've got SOA which processing data for diff clients(asp,sl). The base of this design is domains of my business model. For transporting,showing it to clients I use DTO. For mapping domain to DTO I use AutoMapper. Now I should persist new entities from clients. I want use my DTO's at this scenario too. So i've got some questions as I'm not much familiar with this design 1) Is it a good practice build DTO on client and send it to web-service on the wire? MayBe i should pass my domains? 2) Is it possible have several DTO's to one domain (one show at grid, and one to save). For saving I need set all nonprimitive props at client. 3) DTO - to Domain. If I've got int can I use AutoMapper to generate NHibernate Proxy for this ID, or I should do i manually. Your expierence and practice are very interesting. Thanks for answer!!!

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• High Runtime for Dictionary.Add for a large amount of items

  - by aaginor

  Hi folks, I have a C#-Application that stores data from a TextFile in a Dictionary-Object. The amount of data to be stored can be rather large, so it takes a lot of time inserting the entries. With many items in the Dictionary it gets even worse, because of the resizing of internal array, that stores the data for the Dictionary. So I initialized the Dictionary with the amount of items that will be added, but this has no impact on speed. Here is my function: private Dictionary<IdPair, Edge> AddEdgesToExistingNodes(HashSet<NodeConnection> connections) { Dictionary<IdPair, Edge> resultSet = new Dictionary<IdPair, Edge>(connections.Count); foreach (NodeConnection con in connections) { ... resultSet.Add(nodeIdPair, newEdge); } return resultSet; } In my tests, I insert ~300k items. I checked the running time with ANTS Performance Profiler and found, that the Average time for resultSet.Add(...) doesn't change when I initialize the Dictionary with the needed size. It is the same as when I initialize the Dictionary with new Dictionary(); (about 0.256 ms on average for each Add). This is definitely caused by the amount of data in the Dictionary (ALTHOUGH I initialized it with the desired size). For the first 20k items, the average time for Add is 0.03 ms for each item. Any idea, how to make the add-operation faster? Thanks in advance, Frank

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• Is a call to the following method considered late binding?

  - by AspOnMyNet

  1) Assume: • B1 defines methods virtualM() and nonvirtualM(), where former method is virtual while the latter is non-virtual • B2 derives from B1 • B2 overrides virtualM() • B2 is defined inside assembly A • Application app doesn’t have a reference to assembly A In the following code application app dynamically loads an assembly A, creates an instance of a type B2 and calls methods virtualM() and nonvirtualM(): Assembly a=Assembly.Load(“A”); Type t= a.GetType(“B2”); B1 a = ( B1 ) Activator.CreateInstance ( “t” ); a.virtualM(); a.nonvirtualM(); a) Is call to a.virtualM() considered early binding or late binding? b) I assume a call to a.nonvirtualM() is resolved during compilation time? 2) Does the term late binding refer only to looking up the target method at run time or does it also refer to creating an instance of given type at runtime? thanx EDIT: 1) A a=new A(); a.M(); As far as I know, it is not known at compile time where on the heap (thus at which memory address ) will instance a be created during runtime. Now, with early binding the function calls are replaced with memory addresses during compilation process. But how can compiler replace function call with memory address, if it doesn’t know where on the heap will object a be created during runtime ( here I’m assuming the address of method a.M will also be at same memory location as a )? 2) The method slot is determined at compile time I assume that by method slot you’re referring to the entry point in V-table?

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• Cache data in SQL CE database

  - by user93422

  Background I have an SQL CE database, that is constantly updated (every second). I have a (web) application that allows a user to look at the data in real-time. At some point a user can click "take a snapshot" button, and it will open the snapshot in a different window. And then on that form, there is "print" and "download" buttons that will either generate a page for printing, or will stream the data as CSV file - but same data snapshot has to be used, i.e. I can't go to the DB to get latest data for that. Details SQL CE dabatase is exposed through WCF web service. Snapshot consists of up to 500 records, 10 columns each. Expiration time on the snapshot of 2 hours is sufficient. It is a low-traffic application, so I don't expect more than few (5) connections at the same time. Loosing snapshot is not a big deal, user can simply generate new one. database is accessed by self-hosted WCF web service using Linq-to-SQL. Web site is ASP.NET MVC hosted on UltiDev Cassini. database, and web site are most likely be on the same box, when deployed. The entire app is intranet bound. Problem I need to cache the snapshot of the data at the moment user pressed "take a snapshot" button, so that I can use same data to generate print page, or generate a file for download. Solution 1: Each time there is a need to generate a snapshot, I will create a table in the database. Since there are no temp tables in SQL CE, I will need to clean it up myself. Solution 2: Cache the snapshot in-memory on either DB server, or web server. Question: Is there anything wrong with proposed solutions? Any different solution suggestions?

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• Static Property losing its value intermittently ?

  - by joedotnot

  Is there something fundamentally wrong with the following design, or can anyone see why would the static properties sometimes loose their values ? I have a class library project containing a class AppConfig; this class is consumed by a Webforms project. The skeleton of AppConfig class is as follows: Public Class AppConfig Implements IConfigurationSectionHandler Private Const C_KEY1 As String = "WebConfig.Key.1" Private Const C_KEY2 As String = "WebConfig.Key.2" Private Const C_KEY1_DEFAULT_VALUE as string = "Key1defaultVal" Private Const C_KEY2_DEFAULT_VALUE as string = "Key2defaultVal" Private Shared m_field1 As String Private Shared m_field2 As String Public Shared ReadOnly Property ConfigValue1() As String Get ConfigValue1= m_field1 End Get End Property Public Shared ReadOnly Property ConfigValue2() As String Get ConfigValue2 = m_field2 End Get End Property Public Shared Sub OnApplicationStart() m_field1 = ReadSetting(C_KEY1, C_KEY1_DEFAULT_VALUE) m_field2 = ReadSetting(C_KEY2, C_KEY1_DEFAULT_VALUE) End Sub Public Overloads Shared Function ReadSetting(ByVal key As String, ByVal defaultValue As String) As String Try Dim setting As String = System.Configuration.ConfigurationManager.AppSettings(key) If setting Is Nothing Then ReadSetting = defaultValue Else ReadSetting = setting End If Catch ReadSetting = defaultValue End Try End Function Public Function Create(ByVal parent As Object, ByVal configContext As Object, ByVal section As System.Xml.XmlNode) As Object Implements System.Configuration.IConfigurationSectionHandler.Create Dim objSettings As NameValueCollection Dim objHandler As NameValueSectionHandler objHandler = New NameValueSectionHandler objSettings = CType(objHandler.Create(parent, configContext, section), NameValueCollection) Return 1 End Function End Class The Static Properties get set once on application start, from the Application_Start event of the Global.asax Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs) //Fires when the application is started AppConfig.OnApplicationStart() End Sub Thereafter, whenever we want to access a value in the Web.Config from anywhere, e.g. aspx page code-behind or another class or referenced class, we simply call the static property. For example, AppConfig.ConfigValue1() AppConfig.ConfigValue2() This is turn returns the value stored in the static backing fields m_field1, m_field2 Problem is sometimes these values are empty string, when clearly the Web.Config entry has values. Is there something fundamentally wrong with the above design, or is it reasonable to expect the static properties would keep their value for the life of the Application session?

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