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• Required Working Precision for the BBP Algorithm?

  - by brainfsck

  Hello, I'm looking to compute the nth digit of Pi in a low-memory environment. As I don't have decimals available to me, this integer-only BBP algorithm in Python has been a great starting point. I only need to calculate one digit of Pi at a time. How can I determine the lowest I can set D, the "number of digits of working precision"? D=4 gives me many correct digits, but a few digits will be off by one. For example, computing digit 393 with precision of 4 gives me 0xafda, from which I extract the digit 0xa. However, the correct digit is 0xb. No matter how high I set D, it seems that testing a sufficient number of digits finds an one where the formula returns an incorrect value. I've tried upping the precision when the digit is "close" to another, e.g. 0x3fff or 0x1000, but cannot find any good definition of "close"; for instance, calculating at digit 9798 gives me 0xcde6 , which is not very close to 0xd000, but the correct digit is 0xd. Can anyone help me figure out how much working precision is needed to calculate a given digit using this algorithm? Thank you,

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• EXC_BAD_ACCESS when executing ABAddressBookSave !

  - by Horatiu Paraschiv

  Hi everybody, I'm trying to create a new contact and add it to the AddressBook but when I get to the ABAddressSave line of code I get EXC_BAD_ACCESS. I cannot see what am I doing wrong, I enabled NSZombie to check if this is a memory related error but it didn't spot any. Can anybody tell me what is wrong with this code? Thank you in advance! CFErrorRef error = NULL; ABAddressBookRef iPhoneAddressBook = ABAddressBookCreate(); ABRecordRef newRecord = ABPersonCreate(); ABRecordSetValue(newRecord, kABPersonFirstNameProperty, @"Xxxxxx", &error); ABRecordSetValue(newRecord, kABPersonURLProperty, @"Yyyyyy", &error); //Add phone numbers to record ABMutableMultiValueRef phones = ABMultiValueCreateMutable(kABMultiStringPropertyType); ABMultiValueAddValueAndLabel(phones, @"1-555-555-5555", kABWorkLabel, NULL); ABRecordSetValue(newRecord, kABPersonPhoneProperty, phones, &error); CFRelease(phones); //Add email address to record ABMutableMultiValueRef emails = ABMultiValueCreateMutable(kABMultiStringPropertyType); ABMultiValueAddValueAndLabel(emails, @"[email protected]", kABWorkLabel, NULL); ABRecordSetValue(newRecord, kABPersonEmailProperty, emails, &error); CFRelease(emails); ABMutableMultiValueRef multiAddress = ABMultiValueCreateMutable(kABMultiDictionaryPropertyType); NSMutableDictionary *addressDict = [[NSMutableDictionary alloc] init]; [addressDict setObject:@"xxx1" forKey:(NSString *)kABPersonAddressStreetKey]; [addressDict setObject:@"xxx2" forKey:(NSString *)kABPersonAddressCityKey]; [addressDict setObject:@"xxx3" forKey:(NSString *)kABPersonAddressStateKey]; [addressDict setObject:@"xxx4" forKey:(NSString *)kABPersonAddressZIPKey]; ABMultiValueAddValueAndLabel(multiAddress, addressDict, kABWorkLabel, NULL); ABRecordSetValue(newRecord, kABPersonAddressProperty, multiAddress, &error); CFRelease(multiAddress); [addressDict release]; ABAddressBookAddRecord(iPhoneAddressBook, newRecord, &error); ABAddressBookSave(iPhoneAddressBook, NULL); if(error != nil){ NSLog(@"Error creating contact:%@", error); }

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• Static Data Structures on Embedded Devices (Android in particular)

  - by Mark

  I've started working on some Android applications and have a question regarding how people normally deal with situations where you have a static data set and have an application where that data is needed in memory as one of the standard java collections or as an array. In my current specific issue i have a spreadsheet with some pre-calculated data. It consists of ~100 rows and 3 columns. 1 Column is a string, 1 column is a float, 1 column is an integer. I need access to this data as an array in java. It seems like i could: 1) Encode in XML - This would be cpu intensive to decode in my experience. 2) build into SQLite database - seems like a lot of overhead for static access to data i only need array style access to in ram. 3) Build into binary blob and read in. (never done this in java, i miss void *) 4) Build a python script to take the CSV version of my data and spit out a java function that adds the values to my desired structure with hard coded values. 5) Store a string array via androids resource mechanism and compute the other 2 columns on application load. In my case the computation would require a lot of calls to Math.log, Math.pow and Math.floor which i'd rather not have to do for load time and battery usage reasons. I mostly work in low power embedded applications in C and as such #4 is what i'm used to doing in these situations. It just seems like it should be far easier to gain access to static data structures in java/android. Perhaps I'm just being too battery usage conscious and in my single case i imagine the answer is that it doesn't matter much, but if every application took that stance it could begin to matter. What approaches do people usually take in this situation? Anything I missed?

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• ntpd on Fedora Core 6 with high negative time rest values

  - by Mark White

  The basic problem is we have a FC6 server instance running on a virtual machine, and the system time seems to have been slowly varying until it is now causing a problem. The server runs 24/7 and has been up for 155 days. It has been changed to show GMT, and reports the time as (example) 00:15:15 GMT whereas the actual time is 00:00:00 GMT. This is an offset of 915 seconds. selinux has been changed to 'setenforce 0' for testing and I am running as root. I stop the ntpd service and change the time in System|Administration|Date & Time. The time still shows the same with 'date' in bash. There are no error logs. I change the date with 'date --set' in bash. The response confirms the changed date. I run 'date' and the incorrect date is shown. There are no error logs. I start the ntpd service and /var/log/messages shows success with 'time reset -915.720139s'. The date remains unchanged. ntpq -p shows three three time servers all have offsets of around -915 seconds. I stop ntpd service and try 'ntpd -gqx' and get the same result as above - success, but a large negative time reset. I've tried varying combinations of the above, and a few more settings in System|Administration|Date & Time - no change. I just need to reset the system time to GMT. No offset. But I can't wait for ntpd to slew the time over the next few weeks. Any advice is welcome, cheers! Sure this shouldn't be this difficult... Mark...

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• stock management of assemblys and its sub parts

  - by The Disintegrator

  I have to track the stock of individual parts and kits (assembly) and can't find a satisfactory way of doing this. Sample bogus and hyper simplified database: Table prod: prodID 1 prodName Flux capacitor prodCost 900 prodPrice 1350 (900*1.5) prodStock 3 - prodID 2 prodName Mr Fusion prodCost 300 prodPrice 600 (300*2) prodStock 2 - prodID 3 prodName Time travel kit prodCost 1650 (1350+300) prodPrice 2145 (1650*1.3) prodStock 2 Table rels relID 1 relSrc 1 (Flux capacitor) relType 4 (is a subpart of) relDst 3 (Time travel kit) - relID 2 relSrc 2 (Mr Fusion) relType 4 (is a subpart of) relDst 3 (Time travel kit) prodPrice: it's calculated based on the cost but not in a linear way. In this example for costs of 500 or less, the markup is a 200%. For costs of 500-1000 the markup is 150%. For costs of 1000+ the markup is 130% That's why the time travel kit is much cheaper than the individual parts prodStock: here is my problem. I can sell kits or the individual parts, So the stock of the kits is virtual. The problem when I buy: Some providers sell me the Time Travel kit as a whole (with one barcode) and some sells me the individual parts (with a different barcode) So when I load the stock I don't know how to impute it. The problem when I sell: If I only sell kits, calculate the stock would be easy: "I have 3 Flux capacitors and 2 Mr Fusions, so I have 2 Time travel kits and a Flux Capacitor" But I can sell Kits or individual parts. I have to track the stock of the individual parts and the possible kits at the same time (and I have to compensate for the sell price) Probably this is really simple, but I can't see a simple solution. Resuming: I have to find a way of tracking the stock and the database/program is the one who has to do it (I cant ask the clerk to correct the stock) I'm using php+MySql. But this is more a logical problem than a programing one

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• Joining on a common table, how do you get a FULL OUTER JOIN to expand on another table?

  - by stimpy77

  I've scoured StackOverflow and Google for an answer to this problem. I'm trying to create a Microsot SQL Server 2008 view. Not a stored procedure. Not a function. Just a query (i.e. a view). I have three tables. The first table defines a common key, let's say "CompanyID". The other two tables have a sometimes-common field, let's say "EmployeeName". I want a single table result that, when my WHERE clause says "WHERE CompanyID = 12" looks like this: CompanyID | TableA | TableB 12 | John Doe | John Doe 12 | Betty Sue | NULL 12 | NULL | Billy Bob I've tried a FULL OUTER JOIN that looks like this: SELECT Company.CompanyID, TableA.EmployeeName, TableB.EmployeeName FROM Company FULL OUTER JOIN TableA ON Company.CompanyID = TableA.CompanyID FULL OUTER JOIN TableB ON Company.CompanyID = TableB.CompanyID AND (TableA.EmployeeName IS NULL OR TableB.EmployeeName IS NULL OR TableB.EmployeeName = TableA.EmployeeName) I'm only getting the NULL from one matched table, I'm not getting the expansion for the other table. In the above sample, I'm basically only getting the first and third rows and not the second. Can someone help me create this query and show me how this is done correctly? BTW I already have a stored procedure that looks very clean and populates an in-memory table, but that isn't what I want. Thanks.

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• How can I get PowerShell Added-Types to use Added References

  - by Scott Weinstein

  I'm working on a PoSh project that generates CSharp code, and then Add-Types it into memory. The new types use existing types in an on disk DLL, which is loaded via Add-Type. All is well and good untill I actualy try to invoke methods on the new types. Here's an example of what I'm doing: $PWD = "." rm -Force $PWD\TestClassOne* $code = " namespace TEST{ public class TestClassOne { public int DoNothing() { return 1; } } }" $code | Out-File tcone.cs Add-Type -OutputAssembly $PWD\TestClassOne.dll -OutputType Library -Path $PWD\tcone.cs Add-Type -Path $PWD\TestClassOne.dll $a = New-Object TEST.TestClassOne "Using TestClassOne" $a.DoNothing() "Compiling TestClassTwo" Add-Type -Language CSharpVersion3 -TypeDefinition " namespace TEST{ public class TestClassTwo { public int CallTestClassOne() { var a = new TEST.TestClassOne(); return a.DoNothing(); } } }" -ReferencedAssemblies $PWD\TestClassOne.dll "OK" $b = New-Object TEST.TestClassTwo "Using TestClassTwo" $b.CallTestClassOne() Running the above script gives the following error on the last line: Exception calling "CallTestClassOne" with "0" argument(s): "Could not load file or assembly 'TestClassOne,...' or one of its dependencies. The system cannot find the file specified." At AddTypeTest.ps1:39 char:20 + $b.CallTestClassOne <<<< () + CategoryInfo : NotSpecified: (:) [], MethodInvocationException + FullyQualifiedErrorId : DotNetMethodException What am I doing wrong?

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• AST with fixed nodes instead of error nodes in antlr

  - by ahe

  I have an antlr generated Java parser that uses the C target and it works quite well. The problem is I also want it to parse erroneous code and produce a meaningful AST. If I feed it a minimal Java class with one import after which a semicolon is missing it produces two "Tree Error Node" objects where the "import" token and the tokens for the imported class should be. But since it parses the following code correctly and produces the correct nodes for this code it must recover from the error by adding the semicolon or by resyncing. Is there a way to make antlr reflect this fixed input it produces internally in the AST? Or can I at least get the tokens/text that produced the "Tree Node Errors" somehow? In the C targets antlr3commontreeadaptor.c around line 200 the following fragment indicates that the C target only creates dummy error nodes so far: static pANTLR3_BASE_TREE errorNode (pANTLR3_BASE_TREE_ADAPTOR adaptor, pANTLR3_TOKEN_STREAM ctnstream, pANTLR3_COMMON_TOKEN startToken, pANTLR3_COMMON_TOKEN stopToken, pANTLR3_EXCEPTION e) { // Use the supplied common tree node stream to get another tree from the factory // TODO: Look at creating the erronode as in Java, but this is complicated by the // need to track and free the memory allocated to it, so for now, we just // want something in the tree that isn't a NULL pointer. // return adaptor->createTypeText(adaptor, ANTLR3_TOKEN_INVALID, (pANTLR3_UINT8)"Tree Error Node"); } Am I out of luck here and only the error nodes the Java target produces would allow me to retrieve the text of the erroneous nodes?

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• JSON: Jackson stream parser - is it really worth it?

  - by synic

  I'm making pretty heavy use of JSON parsing in an app I'm writing. Most of what I have done is already implemented using Android's built in JSONObject library (is it json-lib?). JSONObject appears to create instances of absolutely everything in the JSON string... even if I don't end up using all of them. My app currently runs pretty well, even on a G1. My question is this: are the speed and memory benefits from using a stream parser like Jackson worth all the trouble? By trouble, I mean this: As far as I can tell, there are three downsides to using Jackson instead of the built in library: Dependency on an external library. This makes your .apk bigger in the end. Not a huge deal. Your app is more fragile. Since the parsing is not done automatically, it is more vulnerable to changes in the JSON text that it's parsing. I'm extremely worried that malformed JSON will result in infinite loops (as pull parsing requires a lot of while loops). Writing code to parse JSON via a stream parser is ugly and tedious.

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• Using StringBuilder to process csv files to save heap space

  - by portoalet

  I am reading a csv file that has about has about 50,000 lines and 1.1MiB in size (and can grow larger). In Code1, I use String to process the csv, while in Code2 I use StringBuilder (only one thread executes the code, so no concurrency issues) Using StringBuilder makes the code a little bit harder to read that using normal String class. Am I prematurely optimizing things with StringBuilder in Code2 to save a bit of heap space and memory? Code1 fr = new FileReader(file); BufferedReader reader = new BufferedReader(fr); String line = reader.readLine(); while ( line != null ) { int separator = line.indexOf(','); String symbol = line.substring(0, seperator); int begin = separator; separator = line.indexOf(',', begin+1); String price = line.substring(begin+1, seperator); // Publish this update publisher.publishQuote(symbol, price); // Read the next line of fake update data line = reader.readLine(); } Code2 fr = new FileReader(file); StringBuilder stringBuilder = new StringBuilder(reader.readLine()); while( stringBuilder.toString() != null ) { int separator = stringBuilder.toString().indexOf(','); String symbol = stringBuilder.toString().substring(0, separator); int begin = separator; separator = stringBuilder.toString().indexOf(',', begin+1); String price = stringBuilder.toString().substring(begin+1, separator); publisher.publishQuote(symbol, price); stringBuilder.replace(0, stringBuilder.length(), reader.readLine()); }

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• Reading from serial port with Boost Asio?

  - by trikri

  Hi! I'm going to check for incoming messages (data packages) on the serial port, using Boost Asio. Each message will start with a header that is one byte long, and will specify which type of the message has been sent. Each different type of message has an own length. The function I'm about to write should check for new incoming messages continually, and when it finds one it should read it, and then some other function should parse it. I thought that the code might look something like this: void check_for_incoming_messages() { boost::asio::streambuf response; boost::system::error_code error; std::string s1, s2; if (boost::asio::read(port, response, boost::asio::transfer_at_least(0), error)) { s1 = streambuf_to_string(response); int msg_code = s1[0]; if (msg_code < 0 || msg_code >= NUM_MESSAGES) { // Handle error, invalid message header } if (boost::asio::read(port, response, boost::asio::transfer_at_least(message_lengths[msg_code]-s1.length()), error)) { s2 = streambuf_to_string(response); // Handle the content of s1 and s2 } else if (error != boost::asio::error::eof) { throw boost::system::system_error(error); } } else if (error != boost::asio::error::eof) { throw boost::system::system_error(error); } } Is boost::asio::streambuf is the right thing to use? And how do I extract the data from it so I can parse the message? I also want to know if I need to have a separate thread which only calls this function, so that it get called more often? Isn't there a risk for loosing data in between two calls to the function otherwise, because so much data comes in that it can't be stored in the serial ports memory? I'm using Qt as a widget toolkit and I don't really know how long time it needs to process all it's events.

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• Haskell Linear Algebra Matrix Library for Arbitrary Element Types

  - by Johannes Weiß

  I'm looking for a Haskell linear algebra library that has the following features: Matrix multiplication Matrix addition Matrix transposition Rank calculation Matrix inversion is a plus and has the following properties: arbitrary element (scalar) types (in particular element types that are not Storable instances). My elements are an instance of Num, additionally the multiplicative inverse can be calculated. The elements mathematically form a finite field (??2256). That should be enough to implement the features mentioned above. arbitrary matrix sizes (I'll probably need something like 100x100, but the matrix sizes will depend on the user's input so it should not be limited by anything else but the memory or the computational power available) as fast as possible, but I'm aware that a library for arbitrary elements will probably not perform like a C/Fortran library that does the work (interfaced via FFI) because of the indirection of arbitrary (non Int, Double or similar) types. At least one pointer gets dereferenced when an element is touched (written in Haskell, this is not a real requirement for me, but since my elements are no Storable instances the library has to be written in Haskell) I already tried very hard and evaluated everything that looked promising (most of the libraries on Hackage directly state that they wont work for me). In particular I wrote test code using: hmatrix, assumes Storable elements Vec, but the documentation states: Low Dimension : Although the dimensionality is limited only by what GHC will handle, the library is meant for 2,3 and 4 dimensions. For general linear algebra, check out the excellent hmatrix library and blas bindings I looked into the code and the documentation of many more libraries but nothing seems to suit my needs :-(. Update Since there seems to be nothing, I started a project on GitHub which aims to develop such a library. The current state is very minimalistic, not optimized for speed at all and only the most basic functions have tests and therefore should work. But should you be interested in using or helping out developing it: Contact me (you'll find my mail address on my web site) or send pull requests.

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• Per-pixel per-component alpha blending in Windows

  - by Crend King

  I have a 24-bit bitmaps with R, G, B color channels and a 24-bit bitmap with R, G, B alpha channels. I want to alpha blend the first bitmap to a HDC in GDI or RenderTarget in Direct2D with the alpha channels respectively. For example, suppose for one pixel, the bitmap color is (192, 192, 192), the HDC color is (0, 255, 255) and the alpha channels are (30, 40, 50). The final HDC color should be (22, 245, 242). I know I can BitBlt the HDC to a memory HDC first, do alpha blending by manually calculating the color of each pixel and finally BitBlt back. I just want to avoid the additional blitting and leave APIs do their job (faster since they are in kernel space). The first idea comes to my mind is to split the source bitmap into 3 red-only, green-only and blue-only 8-bit bitmaps, do normal alpha blending, then composite the 3 output bitmaps into the HDC. But I don't find a way to do the splitting and composition natively in Windows (would Direct2D layer help?). Also, the splitting and compositing may require many additional copying. The performance overhead would be too high. Or maybe do the alpha blending in 3 passes. Each pass apply the blending for one channel, while maintaining the other 2 unchanged. Thanks for any comment. EDIT: I found this question, and the answer should be good reference to this problem. However, besides AC_SRC_OVER, there is no other blending operation supported. Why don't Microsoft improve their API?

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• ASP.NET Chart Control errors in Event Viewer

  - by Richard Reddy

  Hi, I have been using the ASP.NET chart controls for a while on win2k3 (32bit) setups without any issue but have noticed that on our new win2k8 (64bit) box I am getting a warning message showing up in the event viewer from the chart control. In my web.config file I have the following tag telling the Chart Control where I can store the Temp Files: <add key="ChartImageHandler" value="storage=file;timeout=20;dir=c:\TempImageFiles\;" /> Below is the warning message produced by the control: Event code: 3005 Event message: An unhandled exception has occurred. Event time: 10/7/2009 2:40:03 PM Event time (UTC): 10/7/2009 2:40:03 PM Event ID: 237c3b208962429e8bbc5a48ffd177f0 Event sequence: 2860 Event occurrence: 26 Event detail code: 0 Application information: Application domain: /LM/W3SVC/2/ROOT-1-128993655360497729 Trust level: Full Application Virtual Path: / Application Path: C:\data\sites\mydomain.com\ Machine name: 231692-WEB Process information: Process ID: 4068 Process name: w3wp.exe Account name: NT AUTHORITY\NETWORK SERVICE Exception information: Exception type: ArgumentException Exception message: The image is not found. Request information: Request URL: http://www.mydomain.com/ChartImg.axd?i=chart%5F0%5F3.png&g=bccc8aa11abb470980c60e8cf1e71e15 Request path: /ChartImg.axd User host address: my domain ip User: Is authenticated: False Authentication Type: Thread account name: NT AUTHORITY\NETWORK SERVICE Thread information: Thread ID: 7 Thread account name: NT AUTHORITY\NETWORK SERVICE Is impersonating: False Stack trace: at System.Web.UI.DataVisualization.Charting.ChartHttpHandler.ProcessSavedChartImage(HttpContext context) at System.Web.UI.DataVisualization.Charting.ChartHttpHandler.System.Web.IHttpHandler.ProcessRequest(HttpContext context) at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) It's worth pointing out that ALL of the chart images are displayed correctly on the screen so I'm not sure when/where the image not found error is being caused. Is this a 64bit issue? Thanks, Rich

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• Call long running operation in WSS feature OnActivated Event

  - by dirq

  More specifically - How do I reference SPContext in Web Service with [SoapDocumentMethod(OneWay=true)]? We are creating a feature that needs to run a job when a site is created. The job takes about 4 minutes to complete. So, we made a web service that we can call when the feature is activated. This works but we want it to run asynchronously now. We've found the SoapDocumentMethod's OneWay property and that would work awesomely but the SPContext is now NULL. We have our web services in the _vti_bin virtual directory so it's available in each Windows Sharepoint Services site. I was using the SPContext.Current.Web to get the site and perform the long running operation. I wanted to just fire and forget about it by returning a soap response right away and letting the process run. How can I get the current SPContext? I used to be able to do this in my web service: SPWeb mySite = SPContext.Current.Web; Can I get the same context when I have the [SoapDocumentMethod(OneWay=true)] attribute applied to my web service? Or must I recreate the SPWeb from the url? This is similar to this thread: http://stackoverflow.com/questions/340192/webservice-oneway-and-new-spsitemyurl Update: I've tried these two ways but they didn't work: SPWeb targetSite = SPControl.GetContextWeb(this.Context); SPWeb targetSite2 = SPContext.GetContext(this.Context).Web;

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• Validation without ServiceLocator

  - by Dmitriy Nagirnyak

  Hi, I am getting back again and again to it thinking about the best way to perform validation on POCO objects that need access to some context (ISession in NH, IRepository for example). The only option I still can see is to use S*ervice Locator*, so my validation would look like: public User : ICanValidate { public User() {} // We need this constructor (so no context known) public virtual string Username { get; set; } public IEnumerable<ValidationError> Validate() { if (ServiceLocator.GetService<IUserRepository>().FindUserByUsername(Username) != null) yield return new ValidationError("Username", "User already exists.") } } I already use Inversion Of control and Dependency Injection and really don't like the ServiceLocator due to number of facts: Harder to maintain implicit dependencies. Harder to test the code. Potential threading issues. Explicit dependency only on the ServiceLocator. The code becomes harder to understand. Need to register the ServiceLocator interfaces during the testing. But on the other side, with plain POCO objects, I do not see any other way of performing the validation like above without ServiceLocator and only using IoC/DI. So the question would be: is there any way to use DI/IoC for the situation described above? Thanks, Dmitriy.

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• 3D Web Sites and Applications

  - by Scott Evernden

  I have for the last several years been struggling to understand why the Internet has so few actually useful 3D web applications. It's 2009 and still everything looks like pages from a Sears catalog. You can turn on your TV and find flying logos every night. After that you can get nostalgic and flip on ol' N-64 and play some Zelda or Mario Kart. On the PC, Sims 2 is approaching 6 years old already.. And then there's WoW. Current generation of users - the Facebook crowd, let's say - has ~no~ problem dealing with multi-dimensional environments.. And yet, nothing really immersive seems to happen on the web. I've been hearing about VRML and X3D for at least 10 years and ... pffft .. - nothing earth shaking going on there. Java 3D ? .. cool ! .. but ...... Still .... waiting and waiting. Do you think it will take a killer-web app before people become accustomed-to or will seek to use what could more more engaging web experiences? I am not talking about Second Life and other dedicated downloaded applications. I probably am more focused on apps like Lively or SceneCaster or Hangout or a half dozen others that are delivered 'painlessly' directly into web pages. My own particular interest is in the domain of virtual stores and immersive shopping. Its been a challenge trying to understand why an average user would not want to browse and wander a changing mall-space - like in the real world -- entertained by unexpected discovery. Is the 3D web always going to be 5 years in the future ?

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• Unknown Exception on trying to initialize the web service stub created by Axis C++

  - by Harsha Reddy

  Hi, I am trying out the sample calculator program given in the folder of axis c++. I am mainly interested in the client side. So I used the wsdl to create the stubs and my main is pretty much the same as given in the sample. However on executing the call Calculator ws (endpoint) I get an unknown exception "First-chance exception at 0x7c0024b9 in CalculatorClient.exe: 0xC0000005: Access violation reading location 0x00000000. First-chance exception at 0x7c812afb in CalculatorClient.exe: Microsoft C++ exception: [rethrow] at memory location 0x00000000.. Unhandled exception at 0x7c0024b9 in CalculatorClient.exe: 0xC0000005: Access violation reading location 0x00000000." and the exception causing code is Calculator::Calculator(const char* pchEndpointUri, AXIS_PROTOCOL_TYPE eProtocol) :Stub(pchEndpointUri, eProtocol) { } I had earlier tried to run a a webservice using Axis C++ but had received the same error. At that time my web service was a java ws on WAS. Then I later tried the calculator client (but this time I did not have any server hosting the ws as I just wanted to check if the Client could initialize). Is the problem caused due to the web service not being hosted on Apache in C++ (though I highly doubt it). Any help would be appreciated. Thanks, Harsha

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• evaluation of a java thread dump

  - by raticulin

  I got a thread dump of one of my processes. It has a bunch of these threads. I guess they are keeping a bunch of memory so I am getting OOM. "Thread-8264" prio=6 tid=0x4c94ac00 nid=0xf3c runnable [0x4fe7f000] java.lang.Thread.State: RUNNABLE at java.util.zip.Inflater.inflateBytes(Native Method) at java.util.zip.Inflater.inflate(Inflater.java:223) - locked <0x0c9bc640 (a java.util.zip.Inflater) at org.apache.commons.compress.archivers.zip.ZipArchiveInputStream.read(ZipArchiveInputStream.java:235) at com.my.ZipExtractorCommonsCompress.extract(ZipExtractorCommonsCompress.java:48) at com.my.CustomThreadedExtractorWrapper$ExtractionThread.run(CustomThreadedExtractorWrapper.java:151) Locked ownable synchronizers: - None "Thread-8241" prio=6 tid=0x4c94a400 nid=0xb8c runnable [0x4faef000] java.lang.Thread.State: RUNNABLE at java.util.zip.Inflater.inflateBytes(Native Method) at java.util.zip.Inflater.inflate(Inflater.java:223) - locked <0x0c36b808 (a java.util.zip.Inflater) at org.apache.commons.compress.archivers.zip.ZipArchiveInputStream.read(ZipArchiveInputStream.java:235) at com.my.ZipExtractorCommonsCompress.extract(ZipExtractorCommonsCompress.java:48) at com.my.CustomThreadedExtractorWrapper$ExtractionThread.run(CustomThreadedExtractorWrapper.java:151) Locked ownable synchronizers: - None I am trying to find out how it arrived to this situation. CustomThreadedExtractorWrapper is a wrapper class that fires a thread to do some work (ExtractionThread, which uses ZipExtractorCommonsCompress to extract zip contents from a compressed stream). If the task is taking too long, ExtractionThread.interrupt(); is called to cancel the operation. I can see in my logs that the cancellation happened 25 times. And I see 21 of these threads in my dump. My questions: What is the status of these threads? Alive and running? Blocked somehow? They did not die with .interrupt() apparently? Is there a sure way to really kill a thread? What does really mean 'locked ' in the stack trace? Line 223 in Inflater.java is: public synchronized int inflate(byte[] b, int off, int len) { ... //return is line 223 return inflateBytes(b, off, len); }

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• STLport crash (race condition, Darwin only?)

  - by Jonas Byström

  When I run STLport on Darwin I get a strange crash. (Haven't seen it anywhere else than on Mac, but exactly same thing crash on both i686 and PowerPC.) This is what it looks like in gdb: Program received signal EXC_BAD_ACCESS, Could not access memory. Reason: 13 at address: 0x0000000000000000 [Switching to process 21097] 0x000000010120f47c in stlp_std::__node_alloc_impl::_M_allocate () It may be some setting in STLport, I noticed that Mac.h and MacOSX.h seemed far behind on features. I also know that it it must be some type of race condition, since it doesn't occur just by calling this method (implicity called). The crash happens mainly when I push the system, running 10 simultaneous threads that do a lot of string handling. Other theories I come up with have to do with compiler flags (configure script) and g++ 4.2 bugs (seems like 4.4.3 isn't on Mac yet with Objective-C support, which I need to link with). HELP!!! :) Edit: I run unit tests, which do all sorts of things. This problem arise when I start 10 threads that push the system; and it always comes down to std::string::append which eventually boils down to _M_allocate. Since I can't even get a descent dump of the code that's causing the problem, I figure I'm doing something bad. Could it be so since it's trying to execute at instruction pointer 0x000...000? Are dynlibs built as DLLs in Windows with a jump table? Could it perhaps be that such a jump table has been overwritten for some reason? That would probably explain this behavior. (The code is huge, if I run out of other ideas, I'll post a minimum crashing sample here.)

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• Implementing the ‘defer’ statement from Go in Objective-C?

  - by zoul

  Hello! Today I read about the defer statement in the Go language: A defer statement pushes a function call onto a list. The list of saved calls is executed after the surrounding function returns. Defer is commonly used to simplify functions that perform various clean-up actions. I thought it would be fun to implement something like this in Objective-C. Do you have some idea how to do it? I thought about dispatch finalizers, autoreleased objects and C++ destructors. Autoreleased objects: @interface Defer : NSObject {} + (id) withCode: (dispatch_block_t) block; @end @implementation Defer - (void) dealloc { block(); [super dealloc]; } @end #define defer(__x) [Defer withCode:^{__x}] - (void) function { defer(NSLog(@"Done")); … } Autoreleased objects seem like the only solution that would last at least to the end of the function, as the other solutions would trigger when the current scope ends. On the other hand they could stay in the memory much longer, which would be asking for trouble. Dispatch finalizers were my first thought, because blocks live on the stack and therefore I could easily make something execute when the stack unrolls. But after a peek in the documentation it doesn’t look like I can attach a simple “destructor” function to a block, can I? C++ destructors are about the same thing, I would create a stack-based object with a block to be executed when the destructor runs. This would have the ugly disadvantage of turning the plain .m files into Objective-C++? I don’t really think about using this stuff in production, I’m just interested in various solutions. Can you come up with something working, without obvious disadvantages? Both scope-based and function-based solutions would be interesting.

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• Learning about the low level

  - by Anoners

  I'm interested in learning more about the PC from a lower (machine) level. I graduated from a school which taught us concepts using the Java language which abstracted out that level almost completely. As a result I only learned a bit from the one required assembly language course. In order to cram in ASM and quite a few details about architecture, it was hard to get a very deep picture of what is going on there. At work I focus on unix socket programming in C, so i'm much closer to the hardware now, but I feel I should learn a bit more about what streams really are, how memory management and paging works, what goes on when you call "paint()" on a graphics buffer, etc. I missed out on a lot of this and i'm looking for a good resource to get me started. I've heard a lot about the "Pink Book" by Peter Norton (Programmer's Guide to the IBM PC, Programmer's Guide to inside the PC, etc). It seems like this is on the right track, however the original is quite out dated and the newer ones have had conflicting reviews, with many people saying to stay away from it. I'm not sure what the SO crowd thinks about this book or if they have some suggestions for similar books, online resources, etc that may be good primers for this sort of thing. Any suggestions would be appreciated.

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• Flash video slooow in AIR 2 HTMLLoader component

  - by shane

  I am working on a full screen kiosk application in Flex 4/Air 2 using Flash Builder 4. We have a company training website which staff can access via the kiosk, and the main content is interactive flash training videos. Our target machines are by no means 'beefy', they are Atom n270s @ 1.6Ghz with 1Gb RAM. As it stands the videos are all but unusable when used from within the Air application, the application becomes completely unresponsive (100% cpu usage, click events take approx 5-10 seconds to register). So far I have tried: increasing the default frame rate from 24fps to 60. No improvement. nativeWindow.stage.frameRate = 60; running the videos in a stripped down version of my app, just a full screen HTMLLoader component pointed at the training website. No better than before. disabled hyper threading. The Atom CPU is split into two virtual cores, and the AIR app was only able to use one thread so maxed out at 50% CPU usage. Since the kiosk will only run the AIR app I am happy to loose hyper threading to increase the performance of the Air app. Marginal Improvement. The same website with the same videos is responsive if viewed in ie7 on the same machine, although Internet Explorer takes advantage of the CPU’s hyper threading. The flash videos are built with Adobe Captivate and from what I understand employee JavaScript to relay results back to the server. I will add more information about the video content asap as the training guru is back in the office later this week.

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• Getting a binary file from resource in C#

  - by Jesse Knott

  Hello, I am having a bit of a problem, I am trying to get a PDF as a resource in my application. At this point I have a fillable PDF that I have been able to store as a file next to the binary, but now I am trying to embed the PDF as a resource in the binary. byte[] buffer; try { s = typeof(BattleTracker).Assembly.GetManifestResourceStream("libReports.Resources.DAForm1594.pdf"); buffer = new byte[s.Length]; int read = 0; do { read = s.Read(buffer, read, 32768); } while (read > 0); } catch (Exception e) { throw new Exception("Error: could not import report:", e); } // read existing PDF document PdfReader r = new PdfReader( // optimize memory usage buffer, null ); Every time I run the code I get an error saying "Rebuild trailer not found. Original Error: PDF startxref not found" When I was just opening the file via a path to the static file in my directory it worked fine. I have tried using different encodings UTF-8, UTF-32, UTF-7, ASCII, etc etc.... As a side note I had the same problem with getting a Powerpoint file as a resource, I was finally able to fix that problem by converting the Powerpoint to xml and using that. I have considered doing the same for the PDF but I am referencing elements by field name which does not seem to work with XML PDFs. Can anyone help me out with this? Thanks in advance!

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• x86 CMP Instruction Difference

  - by Pindatjuh

  Question What is the (non-trivial) difference between the following two x86 instructions? 39 /r CMP r/m32,r32 Compare r32 with r/m32 3B /r CMP r32,r/m32 Compare r/m32 with r32 Background I'm building a Java assembler, which will be used by my compiler's intermediate language to produce Windows-32 executables. Currently I have following code: final ModelBase mb = new ModelBase(); // create new memory model mb.addCode(new Compare(Register.ECX, Register.EAX)); // add code mb.addCode(new Compare(Register.EAX, Register.ECX)); // add code final FileOutputStream fos = new FileOutputStream(new File("test.exe")); mb.writeToFile(fos); fos.close(); To output a valid executable file, which contains two CMP instruction in a TEXT-section. The executable outputted to "text.exe" will do nothing interesting, but that's not the point. The class Compare is a wrapper around the CMP instruction. The above code produces (inspecting with OllyDbg): Address Hex dump Command 0040101F |. 3BC8 CMP ECX,EAX 00401021 |. 3BC1 CMP EAX,ECX The difference is subtle: if I use the 39 byte-opcode: Address Hex dump Command 0040101F |. 39C1 CMP ECX,EAX 00401021 |. 39C8 CMP EAX,ECX Which makes me wonder about their synonymity and why this even exists.

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