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• Stored procedure performance randomly plummets; trivial ALTER fixes it. Why?

  - by gWiz

  I have a couple of stored procedures on SQL Server 2005 that I've noticed will suddenly take a significantly long time to complete when invoked from my ASP.NET MVC app running in an IIS6 web farm of four servers. Normal, expected completion time is less than a second; unexpected anomalous completion time is 25-45 seconds. The problem doesn't seem to ever correct itself. However, if I ALTER the stored procedure (even if I don't change anything in the procedure, except to perhaps add a space to the script created by SSMS Modify command), the completion time reverts to expected completion time. IIS and SQL Server are running on separate boxes, both running Windows Server 2003 R2 Enterprise Edition. SQL Server is Standard Edition. All machines have dual Xeon E5450 3GHz CPUs and 4GB RAM. SQL Server is accessed using its TCP/IP protocol over gigabit ethernet (not sure what physical medium). The problem is present from all web servers in the web farm. When I invoke the procedure from a query window in SSMS on my development machine, the procedure completes in normal time. This is strange because I was under the impression that SSMS used the same SqlClient driver as in .NET. When I point my development instance of the web app to the production database, I again get the anomalous long completion time. If my SqlCommand Timeout is too short, I get System.Data.SqlClient.SqlException: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. Question: Why would performing ALTER on the stored procedure, without actually changing anything in it, restore the completion time to less than a second, as expected? Edit: To clarify, when the procedure is running slow for the app, it simultaneously runs fine in SSMS with the same parameters. The only difference I can discern is login credentials (next time I notice the behavior, I'll be checking from SSMS with the same creds). The ultimate goal is to get the procs to sustainably run with expected speed without requiring occasional intervention. Resolution: I wanted to to update this question in case others are experiencing this issue. Following the leads of the answers below, I was able to consistently reproduce this behavior. In order to test, I utilize sp_recompile and pass it one of the susceptible sprocs. I then initiate a website request from my browser that will invoke the sproc with atypical parameters. Lastly, I initiate a website request to a page that invokes the sproc with typical parameters, and observe that the request does not complete because of a SQL timeout on the sproc invocation. To resolve this on SQL Server 2005, I've added OPTIMIZE FOR hints to my SELECT. The sprocs that were vulnerable all have the "all-in-one" pattern described in this article. This pattern is certainly not ideal but was a necessary trade-off given the timeframe for the project.

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• how to develop a program to minimize errors in human transcription of hand written surveys

  - by Alex. S.

  I need to develop custom software to do surveys. Questions may be of multiple choice, or free text in a very few cases. I was asked to design a subsystem to check if there is any error in the manual data entry for the multiple choices part. We're trying to speed up the user data entry process and to minimize human input differences between digital forms and the original questionnaires. The surveys are filled with handwritten marks and text by human interviewers, so it's possible to find hard to read marks, or also the user could accidentally select a different value in some question, and we would like to avoid that. The software must include some automatic control to detect possible typing differences. Each answer of the multiple choice questions has the same probability of being selected. This question has two parts: The GUI. The most simple thing I have in mind is to implement the most usable design of the questions display: use of large and readable fonts and space generously the choices. Is there something else? For faster input, I would like to use drop down lists (favoring keyboard over mouse). Given the questions are grouped in sections, I would like to show the answers selected for the questions of that section, but this could slow down the process. Any other ideas? The error checking subsystem. What else can I do to minimize or to check human typos in the multiple choice questions? Is this a solvable problem? is there some statistical methodology to check values that were entered by the users are the same from the hand filled forms? For example, let's suppose the survey has 5 questions, and each has 4 options. Let's say I have n survey forms filled in paper by interviewers, and they're ready to be entered in the software, then how to minimize the accidental differences that can have the manual transcription of the n surveys, without having to double check everything in the 5 questions of the n surveys? My first suggestion is that at the end of the processing of all the hand filled forms, the software could choose some forms randomly to make a double check of the responses in a few instances, but on what criteria can I make this selection? This validation would be enough to cover everything in a significant way? The actual survey is nation level and it has 56 pages with over 200 questions in total, so it will be a lot of hand written pages by many people, and the intention is to reduce the likelihood of errors and to optimize speed in the data entry process. The surveys must filled in paper first, given the complications of taking laptops or handhelds with the interviewers.

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• How do you combine "Revision Control" with "WorkFlow" for R?

  - by Tal Galili

  Hello all, I remember coming across R users writing that they use "Revision control" (e.g: "Source control"), and I am curious to know: How do you combine "Revision control" with your statistical analysis WorkFlow? Two (very) interesting discussions talk about how to deal with the WorkFlow. But neither of them refer to the revision control element: http://stackoverflow.com/questions/1266279/how-to-organize-large-r-programs http://stackoverflow.com/questions/1429907/workflow-for-statistical-analysis-and-report-writing A Long Update To The Question: Following some of the people's answers, and Dirk's question in the comment, I would like to direct my question a bit more. After reading the Wiki article about "revision control" (which I was previously not familiar with), it was clear to me that when using revision control, what one does is to build a development structure of his code. This structure either leads to a "final product" or to several branches. When building something like, let's say, a website. There is usually one end product you work towards (the website), with some prototypes along the way. But when doing a statistical analysis, the work (to my view) is different. Sometimes you know where you want to get to. But more often, you explore. Explore cleaning the dataset. Explore different methods for statistical analysis, and ask various questions of your data (and I am writing this, knowing how Frank Harrell, and other experience statisticians feels about Data dredging). That is way the WorkFlow question with statistical programming is (in my view) a serious and deep question, raising many issues, The simpler ones are technical: Which revision control software do you use (and why) ? Which IDE do you use(and why) ? The more interesting question are about work process: How do you structure your files? What do you keep as a separate file and what as a revision? or asking in a different way - What should be a "branch" and what should be a "sub project" in your code? For example: When starting to explore your data, should a plot be creating and then erased because it didn't lead any where (but kept as a revision) or should there be a backup file of that path? How you solve this tension was my initial curiosity. The second question is "what might I be missing?". What rules (of thumb) should one follow so to avoid common pitfalls doing statistical programming with version control? In my intuition, I feel that statistical programming is inherently different then software development (I am writing this without being a real expert in statistical programming, and even less so in software development). That's way I am unsure which of the lessons I have read here about version control would be applicable. Thanks a lot, Tal

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• BufferedReader no longer buffering after a while?

  - by BobTurbo

  Sorry I can't post code but I have a bufferedreader with 50000000 bytes set as the buffer size. It works as you would expect for half an hour, the HDD light flashing every two minutes or so, reading in the big chunk of data, and then going quiet again as the CPU processes it. But after about half an hour (this is a very big file), the HDD starts thrashing as if it is reading one byte at a time. It is still in the same loop and I think I checked free ram to rule out swapping (heap size is default). Probably won't get any helpful answers, but worth a try. OK I have changed heap size to 768mb and still nothing. There is plenty of free memory and java.exe is only using about 300mb. Now I have profiled it and heap stays at about 200MB, well below what is available. CPU stays at 50%. Yet the HDD starts thrashing like crazy. I have.. no idea. I am going to rewrite the whole thing in c#, that is my solution. Here is the code (it is just a throw-away script, not pretty): BufferedReader s = null; HashMap<String, Integer> allWords = new HashMap<String, Integer>(); HashSet<String> pageWords = new HashSet<String>(); long[] pageCount = new long[78592]; long pages = 0; Scanner wordFile = new Scanner(new BufferedReader(new FileReader("allWords.txt"))); while (wordFile.hasNext()) { allWords.put(wordFile.next(), Integer.parseInt(wordFile.next())); } s = new BufferedReader(new FileReader("wikipedia/enwiki-latest-pages-articles.xml"), 50000000); StringBuilder words = new StringBuilder(); String nextLine = null; while ((nextLine = s.readLine()) != null) { if (a.matcher(nextLine).matches()) { continue; } else if (b.matcher(nextLine).matches()) { continue; } else if (c.matcher(nextLine).matches()) { continue; } else if (d.matcher(nextLine).matches()) { nextLine = s.readLine(); if (e.matcher(nextLine).matches()) { if (f.matcher(s.readLine()).matches()) { pageWords.addAll(Arrays.asList(words.toString().toLowerCase().split("[^a-zA-Z]"))); words.setLength(0); pages++; for (String word : pageWords) { if (allWords.containsKey(word)) { pageCount[allWords.get(word)]++; } else if (!word.isEmpty() && allWords.containsKey(word.substring(0, word.length() - 1))) { pageCount[allWords.get(word.substring(0, word.length() - 1))]++; } } pageWords.clear(); } } } else if (g.matcher(nextLine).matches()) { continue; } words.append(nextLine); words.append(" "); }

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• Exporting classes containing std:: objects (vector, map, etc) from a dll

  - by RnR

  I'm trying to export classes from a DLL that contain objects such as std::vectors and std::stings - the whole class is declared as dll export through: class DLL_EXPORT FontManager { The problem is that for members of the complex types I get this warning: warning C4251: 'FontManager::m__fonts' : class 'std::map<_Kty,_Ty' needs to have dll-interface to be used by clients of class 'FontManager' with [ _Kty=std::string, _Ty=tFontInfoRef ] I'm able to remove some of the warnings by putting the following forward class declaration before them even though I'm not changing the type of the member variables themselves: template class DLL_EXPORT std::allocator<tCharGlyphProviderRef>; template class DLL_EXPORT std::vector<tCharGlyphProviderRef,std::allocator<tCharGlyphProviderRef> >; std::vector<tCharGlyphProviderRef> m_glyphProviders; Looks like the forward declaration "injects" the DLL_EXPORT for when the member is compiled but is it safe? Does it realy change anything when the client compiles this header and uses the std container on his side? Will it make all future uses of such a container DLL_EXPORT (and possibly not inline?)? And does it really solve the problem that the warning tries to warn about? Is this warning anything I should be worried about or would it be best to disable it in the scope of these constructs? The clients and the dll will always be built using the same set of libraries and compilers and those are header only classes... I'm using Visual Studio 2003 with the standard STD library. ---- Update ---- I'd like to target you more though as I see the answers are general and here we're talking about std containers and types (such as std::string) - maybe the question really is: Can we disable the warning for standard containers and types available to both the client and the dll through the same library headers and treat them just as we'd treat an int or any other built-in type? (It does seem to work correctly on my side.) If so would should be the conditions under which we can do this? Or should maybe using such containers be prohibited or at least ultra care taken to make sure no assignment operators, copy constructors etc will get inlined into the dll client? In general I'd like to know if you feel designing a dll interface having such objects (and for example using them to return stuff to the client as return value types) is a good idea or not and why - I'd like to have a "high level" interface to this functionality... maybe the best solution is what Neil Butterworth suggested - creating a static library?

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• How can a C/C++ program put itself into background?

  - by Larry Gritz

  What's the best way for a running C or C++ program that's been launched from the command line to put itself into the background, equivalent to if the user had launched from the unix shell with '&' at the end of the command? (But the user didn't.) It's a GUI app and doesn't need any shell I/O, so there's no reason to tie up the shell after launch. But I want a shell command launch to be auto-backgrounded without the '&' (or on Windows). Ideally, I want a solution that would work on any of Linux, OS X, and Windows. (Or separate solutions that I can select with #ifdef.) It's ok to assume that this should be done right at the beginning of execution, as opposed to somewhere in the middle. One solution is to have the main program be a script that launches the real binary, carefully putting it into the background. But it seems unsatisfying to need these coupled shell/binary pairs. Another solution is to immediately launch another executed version (with 'system' or CreateProcess), with the same command line arguments, but putting the child in the background and then having the parent exit. But this seems clunky compared to the process putting itself into background. Edited after a few answers: Yes, a fork() (or system(), or CreateProcess on Windows) is one way to sort of do this, that I hinted at in my original question. But all of these solutions make a SECOND process that is backgrounded, and then terminate the original process. I was wondering if there was a way to put the EXISTING process into the background. One difference is that if the app was launched from a script that recorded its process id (perhaps for later killing or other purpose), the newly forked or created process will have a different id and so will not be controllable by any launching script, if you see what I'm getting at. Edit #2: fork() isn't a good solution for OS X, where the man page for 'fork' says that it's unsafe if certain frameworks or libraries are being used. I tried it, and my app complains loudly at runtime: "The process has forked and you cannot use this CoreFoundation functionality safely. You MUST exec()." I was intrigued by daemon(), but when I tried it on OS X, it gave the same error message, so I assume that it's just a fancy wrapper for fork() and has the same restrictions. Excuse the OS X centrism, it just happens to be the system in front of me at the moment. But I am indeed looking for a solution to all three platforms.

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• Project Euler #18 - how to brute force all possible paths in tree-like structure using Python?

  - by euler user

  Am trying to learn Python the Atlantic way and am stuck on Project Euler #18. All of the stuff I can find on the web (and there's a LOT more googling that happened beyond that) is some variation on 'well you COULD brute force it, but here's a more elegant solution'... I get it, I totally do. There are really neat solutions out there, and I look forward to the day where the phrase 'acyclic graph' conjures up something more than a hazy, 1 megapixel resolution in my head. But I need to walk before I run here, see the state, and toy around with the brute force answer. So, question: how do I generate (enumerate?) all valid paths for the triangle in Project Euler #18 and store them in an appropriate python data structure? (A list of lists is my initial inclination?). I don't want the answer - I want to know how to brute force all the paths and store them into a data structure. Here's what I've got. I'm definitely looping over the data set wrong. The desired behavior would be to go 'depth first(?)' rather than just looping over each row ineffectually.. I read ch. 3 of Norvig's book but couldn't translate the psuedo-code. Tried reading over the AIMA python library for ch. 3 but it makes too many leaps. triangle = [ [75], [95, 64], [17, 47, 82], [18, 35, 87, 10], [20, 4, 82, 47, 65], [19, 1, 23, 75, 3, 34], [88, 2, 77, 73, 7, 63, 67], [99, 65, 4, 28, 6, 16, 70, 92], [41, 41, 26, 56, 83, 40, 80, 70, 33], [41, 48, 72, 33, 47, 32, 37, 16, 94, 29], [53, 71, 44, 65, 25, 43, 91, 52, 97, 51, 14], [70, 11, 33, 28, 77, 73, 17, 78, 39, 68, 17, 57], [91, 71, 52, 38, 17, 14, 91, 43, 58, 50, 27, 29, 48], [63, 66, 4, 68, 89, 53, 67, 30, 73, 16, 69, 87, 40, 31], [04, 62, 98, 27, 23, 9, 70, 98, 73, 93, 38, 53, 60, 4, 23], ] def expand_node(r, c): return [[r+1,c+0],[r+1,c+1]] all_paths = [] my_path = [] for i in xrange(0, len(triangle)): for j in xrange(0, len(triangle[i])): print 'row ', i, ' and col ', j, ' value is ', triangle[i][j] ??my_path = somehow chain these together??? if my_path not in all_paths all_paths.append(my_path) Answers that avoid external libraries (like itertools) preferred.

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• How do I create a thread-safe write-once read-many value in Java?

  - by Software Monkey

  This is a problem I encounter frequently in working with more complex systems and which I have never figured out a good way to solve. It usually involves variations on the theme of a shared object whose construction and initialization are necessarily two distinct steps. This is generally because of architectural requirements, similar to applets, so answers that suggest I consolidate construction and initialization are not useful. By way of example, let's say I have a class that is structured to fit into an application framework like so: public class MyClass { private /*ideally-final*/ SomeObject someObject; MyClass() { someObject=null; } public void startup() { someObject=new SomeObject(...arguments from environment which are not available until startup is called...); } public void shutdown() { someObject=null; // this is not necessary, I am just expressing the intended scope of someObject explicitly } } I can't make someObject final since it can't be set until startup() is invoked. But I would really like it to reflect it's write-once semantics and be able to directly access it from multiple threads, preferably avoiding synchronization. The idea being to express and enforce a degree of finalness, I conjecture that I could create a generic container, like so: public class WoRmObject<T> { private T object; WoRmObject() { object=null; } public WoRmObject set(T val) { object=val; return this; } public T get() { return object; } } and then in MyClass, above, do: private final WoRmObject<SomeObject> someObject; MyClass() { someObject=new WoRmObject<SomeObject>(); } public void startup() { someObject.set(SomeObject(...arguments from environment which are not available until startup is called...)); } Which raises some questions for me: Is there a better way, or existing Java object (would have to be available in Java 4)? Is this thread-safe provided that no other thread accesses someObject.get() until after it's set() has been called. The other threads will only invoke methods on MyClass between startup() and shutdown() - the framework guarantees this. Given the completely unsynchronized WoRmObject container, it is ever possible under either JMM to see a value of object which is neither null nor a reference to a SomeObject? In other words, does has the JMM always guaranteed that no thread can observe the memory of an object to be whatever values happened to be on the heap when the object was allocated.

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• Truth tables in code? How to structure state machine?

  - by HanClinto

  I have a (somewhat) large truth table / state machine that I need to implement in my code (embedded C). I anticipate the behavior specification of this state machine to change in the future, and so I'd like to keep this easily modifiable in the future. My truth table has 4 inputs and 4 outputs. I have it all in an Excel spreadsheet, and if I could just paste that into my code with a little formatting, that would be ideal. I was thinking I would like to access my truth table like so: u8 newState[] = decisionTable[input1][input2][input3][input4]; And then I could access the output values with: setOutputPin( LINE_0, newState[0] ); setOutputPin( LINE_1, newState[1] ); setOutputPin( LINE_2, newState[2] ); setOutputPin( LINE_3, newState[3] ); But in order to get that, it looks like I would have to do a fairly confusing table like so: static u8 decisionTable[][][][][] = {{{{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }}, {{ 0, 0, 0, 0 }, { 0, 0, 0, 0 }}}, {{{ 0, 0, 1, 1 }, { 0, 1, 1, 1 }}, {{ 0, 1, 0, 1 }, { 1, 1, 1, 1 }}}}, {{{{ 0, 1, 0, 1 }, { 1, 1, 1, 1 }}, {{ 0, 1, 0, 1 }, { 1, 1, 1, 1 }}}, {{{ 0, 1, 1, 1 }, { 0, 1, 1, 1 }}, {{ 0, 1, 0, 1 }, { 1, 1, 1, 1 }}}}; Those nested brackets can be somewhat confusing -- does anyone have a better idea for how I can keep a pretty looking table in my code? Thanks! Edit based on HUAGHAGUAH's answer: Using an amalgamation of everyone's input (thanks -- I wish I could "accept" 3 or 4 of these answers), I think I'm going to try it as a two dimensional array. I'll index into my array using a small bit-shifting macro: #define SM_INPUTS( in0, in1, in2, in3 ) ((in0 << 0) | (in1 << 1) | (in2 << 2) | (in3 << 3)) And that will let my truth table array look like this: static u8 decisionTable[][] = { { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 0, 0 }, { 0, 0, 1, 1 }, { 0, 1, 1, 1 }, { 0, 1, 0, 1 }, { 1, 1, 1, 1 }, { 0, 1, 0, 1 }, { 1, 1, 1, 1 }, { 0, 1, 0, 1 }, { 1, 1, 1, 1 }, { 0, 1, 1, 1 }, { 0, 1, 1, 1 }, { 0, 1, 0, 1 }, { 1, 1, 1, 1 }}; And I can then access my truth table like so: decisionTable[ SM_INPUTS( line1, line2, line3, line4 ) ] I'll give that a shot and see how it works out. I'll also be replacing the 0's and 1's with more helpful #defines that express what each state means, along with /**/ comments that explain the inputs for each line of outputs. Thanks for the help, everyone!

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• Maximum nametable char count exceeded

  - by doc

  I'm having issues with the maximum nametable char count quota, I followed a couple of answers here and it solved the problem for a while, but now I'm having the same issue. My Server side config is as follows: <system.serviceModel> <bindings> <netTcpBinding> <binding name="GenericBinding" maxBufferPoolSize="2147483647" maxBufferSize="2147483647" maxReceivedMessageSize="2147483647"> <readerQuotas maxDepth="2147483647" maxStringContentLength="2147483647" maxArrayLength="2147483647" maxBytesPerRead="2147483647" maxNameTableCharCount="2147483647" /> <security mode="None" /> </binding> </netTcpBinding> </bindings> <behaviors> <serviceBehaviors> <behavior> <serviceMetadata httpGetEnabled="false" /> <serviceDebug includeExceptionDetailInFaults="true" /> <dataContractSerializer maxItemsInObjectGraph="1000000" /> </behavior> </serviceBehaviors> </behaviors> <services> <service name="REMWCF.RemWCFSvc"> <endpoint address="" binding="netTcpBinding" contract="REMWCF.IRemWCFSvc" bindingConfiguration="GenericBinding" /> <endpoint address="mex" binding="mexTcpBinding" contract="IMetadataExchange" /> <host> <baseAddresses> <add baseAddress="net.tcp://localhost:9081/RemWCFSvc" /> </baseAddresses> </host> </service> </services> </system.serviceModel> I also have the same tcp binding on the devenv configuration. Have I reached the limit of contracts supported? Is there a way to turn off that quota? EDIT Error Message: Error: Cannot obtain Metadata from net.tcp://localhost:9081/RemWCFSvc/mex If this is a Windows (R) Communication Foundation service to which you have access, please check that you have enabled metadata publishing at the specified address. For help enabling metadata publishing, please refer to the MSDN documentation at http://go.microsoft.com/fwlink/?LinkId=65455.WS-Metadata Exchange Error URI: net.tcp://localhost:9081/RemWCFSvc/mex Metadata contains a reference that cannot be resolved: 'net.tcp://localhost:9081/RemWCFSvc/mex'. There is an error in the XML document. The maximum nametable character count quota (16384) has been exceeded while reading XML data. The nametable is a data structure used to store strings encountered during XML processing - long XML documents with non-repeating element names, attribute names and attribute values may trigger this quota. This quota may be increased by changing the MaxNameTableCharCount property on the XmlDictionaryReaderQuotas object used when creating the XML reader. I'm getting that error when trying to run the WCF (which is hosted in a windows service app).

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• Converting C source to C++

  - by Barry Kelly

  How would you go about converting a reasonably large (300K), fairly mature C codebase to C++? The kind of C I have in mind is split into files roughly corresponding to modules (i.e. less granular than a typical OO class-based decomposition), using internal linkage in lieu private functions and data, and external linkage for public functions and data. Global variables are used extensively for communication between the modules. There is a very extensive integration test suite available, but no unit (i.e. module) level tests. I have in mind a general strategy: Compile everything in C++'s C subset and get that working. Convert modules into huge classes, so that all the cross-references are scoped by a class name, but leaving all functions and data as static members, and get that working. Convert huge classes into instances with appropriate constructors and initialized cross-references; replace static member accesses with indirect accesses as appropriate; and get that working. Now, approach the project as an ill-factored OO application, and write unit tests where dependencies are tractable, and decompose into separate classes where they are not; the goal here would be to move from one working program to another at each transformation. Obviously, this would be quite a bit of work. Are there any case studies / war stories out there on this kind of translation? Alternative strategies? Other useful advice? Note 1: the program is a compiler, and probably millions of other programs rely on its behaviour not changing, so wholesale rewriting is pretty much not an option. Note 2: the source is nearly 20 years old, and has perhaps 30% code churn (lines modified + added / previous total lines) per year. It is heavily maintained and extended, in other words. Thus, one of the goals would be to increase mantainability. [For the sake of the question, assume that translation into C++ is mandatory, and that leaving it in C is not an option. The point of adding this condition is to weed out the "leave it in C" answers.]

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• ASP.Net MVC Ajax form with jQuery validation

  - by Tomas Lycken

  I have an MVC view with a form built with the Ajax.BeginForm() helper method, and I'm trying to validate user input with the jQuery Validation plugin. I get the plugin to highlight the inputs with invalid input data, but despite the invalid input the form is posted to the server. How do I stop this, and make sure that the data is only posted when the form validates? My code The form: <fieldset> <legend>leave a message</legend> <% using (Ajax.BeginForm("Post", new AjaxOptions { UpdateTargetId = "GBPostList", InsertionMode = InsertionMode.InsertBefore, OnSuccess = "getGbPostSuccess", OnFailure = "showFaliure" })) { %> <div class="column" style="width: 230px;"> <p> <label for="Post.Header"> Rubrik</label> <%= Html.TextBox("Post.Header", null, new { @style = "width: 200px;", @class="text required" }) %></p> <p> <label for="Post.Post"> Meddelande</label> <%= Html.TextArea("Post.Post", new { @style = "width: 230px; height: 120px;" }) %></p> </div> <p> <input type="submit" value="OK!" /></p> </fieldset> The JavaScript validation: $(document).ready(function() { // for highlight var elements = $("input[type!='submit'], textarea, select"); elements.focus(function() { $(this).parents('p').addClass('highlight'); }); elements.blur(function() { $(this).parents('p').removeClass('highlight'); }); // for validation $("form").validate(); }); EDIT: As I was getting downvotes for publishing follow-up problems and their solutions in answers, here is also the working validate method... function ajaxValidate() { return $('form').validate({ rules: { "Post.Header": { required: true }, "Post.Post": { required: true, minlength: 3 } }, messages: { "Post.Header": "Please enter a header", "Post.Post": { required: "Please enter a message", minlength: "Your message must be 3 characters long" } } }).form(); }

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• How to handle very frequent updates to a Lucene index

  - by fsm

  I am trying to prototype an indexing/search application which uses very volatile indexing data sources (forums, social networks etc), here are some of the performance requirements, Very fast turn-around time (by this I mean that any new data (such as a new message on a forum) should be available in the search results very soon (less than a minute)) I need to discard old documents on a fairly regular basis to ensure that the search results are not dated. Last but not least, the search application needs to be responsive. (latency on the order of 100 milliseconds, and should support at least 10 qps) All of the requirements I have currently can be met w/o using Lucene (and that would let me satisfy all 1,2 and 3), but I am anticipating other requirements in the future (like search relevance etc) which Lucene makes easier to implement. However, since Lucene is designed for use cases far more complex than the one I'm currently working on, I'm having a hard time satisfying my performance requirements. Here are some questions, a. I read that the optimize() method in the IndexWriter class is expensive, and should not be used by applications that do frequent updates, what are the alternatives? b. In order to do incremental updates, I need to keep committing new data, and also keep refreshing the index reader to make sure it has the new data available. These are going to affect 1 and 3 above. Should I try duplicate indices? What are some common approaches to solving this problem? c. I know that Lucene provides a delete method, which lets you delete all documents that match a certain query, in my case, I need to delete all documents which are older than a certain age, now one option is to add a date field to every document and use that to delete documents later. Is it possible to do range queries on document ids (I can create my own id field since I think that the one created by lucene keeps changing) to delete documents? Is it any faster than comparing dates represented as strings? I know these are very open questions, so I am not looking for a detailed answer, I will try to treat all of your answers as suggestions and use them to inform my design. Thanks! Please let me know if you need any other information.

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• Find the closest palindrome number C#

  - by user294837

  Hi All, I am trying to create a console application that reads number from a file all underneath each other like so: 101 9 and then outputs into another file the closest palindrome number. So far what I have is not quite rightm i.e. I don't think I can put the class inside a method which is a bit more Java I was wandering if anyone could help at all? Thanks :) namespace PalidromeC { class Program { static public void Main(string[] args) { #region WriteAnswers try { StreamWriter sw = new StreamWriter("C://Temp/PalindromeAnswers.txt"); sw.WriteLine("Answers"); sw.Close(); }//try catch (Exception e) { Console.WriteLine("Exception: " + e.Message); }//catch #endregion #region ReadFile try { string numbers; StreamReader sr = new StreamReader("C://Temp/Palindrome.txt"); numbers = sr.ReadLine(); while (numbers != null) { Console.WriteLine(numbers); numbers = sr.ReadLine(); }//while sr.Close(); Console.ReadLine(); }//try catch (Exception e) { Console.WriteLine("Exception: " + e.Message); }//catch #endregion NearPalindromeFinder f = new NearPalindromeFinder(); int palindrome = f.findNearPalindrome(n); Console.WriteLine("Nearest Palindrome = " + palindrome); }//main public static void testFindNearestPalindrome(int n) { class NearPalindromeFinder { int findNearPalindrome(int start) { if (testPalindrome(start)) return start; else { int neg = start; int pos = start; for (int i = 0; i < start; i++) { if (testPalindrome(start-i)) { neg = start-i; break; }//if if (testPalindrome(start+i)) { pos = start+i; break; }//if }//for return (start == neg) ? pos : neg; }//else }//findNearPalindrome bool testPalindrome(int start) { if (start == 0 || start == 1) return true; String str = String.valueOf(start); String rev = new if (str.equals(rev)) return true; else return false; }//testPalindrome }//NearPalindromeFinder class }//testFindNearestPalindrome }//Program Class

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• Custom cell in list in Flash AS3

  - by Stian Flatby

  I am no expert in Flash, and I need some quick help here, without needing to learn everything from scratch. Short story, I have to make a list where each cell contains an image, two labels, and a button. List/Cell example: img - label - label - button img - label - label - button As a Java-programmer, I have tried to quicly learn the syntax and visualness of Flash and AS3, but with no luck so far. I have fairly understood the basics of movie clips etc. I saw a tutorial on how to add a list, and add some text to it. So I dragged in a list, and in the code went list.addItem({label:"hello"}); , and that worked ofc. So i thought if I double-clicked the MC of the list, i would get to tweak some things. In there I have been wandering around different halls of cell-renderers etc. I have now come to the point that I entered the CellRenderer_skinUp or something, and customized it to my liking. When this was done, I expected i could use list.addItem(); and get an empty "version" of my cell, with the img, labels and the button. But AS3 expects an input in addItem. From my object-oriented view, I am thinking that i have to create an object of the cell i have made, but i have no luck reaching it.. I tried to go var test:CellRenderer = list.listItem; list.addItem(test); ..But with no luck. This is just for funsies, but I really want to make this work, however not so much that I am willing to read up on ALOT of Flash and AS3. I felt that I was closing in on the prize, but the compiler expected a semicolon after the variable (list.addItem({test:something});). Note: If possible, I do NOT want this: list.addItem({image:"src",label:"text",label"text",button:"text"}); Well.. It actually is what I want, but I would really like to custom-draw everything. Does anyone get what I am trying to do, and has any answers for me? Am I approaching this the wrong way? I have searched the interwebs for custom list-cells, but with no luck. Please, any guiding here is appreciated! Sti

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• Race condition for thread startup

  - by Ozzah

  A similar question was asked here, but the answers generally all seem to relate to the lambda notation. I get a similar result without the lambda so I thought I'd ask for some clarification: Say I have something like this: for (int i = 0; i < 5; i++) (new Thread(new ThreadStart(delegate() { Console.WriteLine("Thread " + i); }))).Start(); One would expect the following output: Thread 0 Thread 1 Thread 2 Thread 3 Thread 4 Now I realise that the threads aren't started in any particular order, so let's just assume that the above lines can come out in any order. But that is not what happens. What instead happens: Thread 3 Thread 4 Thread 4 Thread 4 Thread 4 or something similar, which leads me to believe that rather than passing the value if i, it is passing the reference. (Which is weird, since an int is a value type). Doing something like this: for (int i = 0; i < 5; i++) (new Thread(new ThreadStart(delegate() { int j = i; Console.WriteLine("Thread " + j); }))).Start(); does not help either, even though we have made a copy of i. I am assuming the reason is that it hasn't made a copy of i in time. Doing something like this: for (int i = 0; i < 5; i++) { (new Thread(new ThreadStart(delegate() { Console.WriteLine("Thread " + i); }))).Start(); Thread.Sleep(50); } seems to fix the problem, however it is extremely undesirable as we're wasting 50ms on each iteration, not to mention the fact that if the computer is heavily loaded then maybe 50ms may not be enough. Here is a sample with my current, specific problem: Thread t = new Thread(new ThreadStart(delgate() { threadLogic(param1, param2, param3, param4); })); t.Start(); param1 = param2 = param3 = param4 = null; with: void threadLogic(object param1, object param2, object param3, object param4) { // Do some stuff here... } I want threadLogic() to run in its own thread, however the above code gives a null reference exception. I assume this is because the values are set to null before the thread has had a chance to start. Again, putting a Thread.Sleep(100) works, but it is an awful solution from every aspect. What do you guys recommend for this particular type of race condition?

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• What's the C strategy to "imitate" a C++ template ?

  - by Andrei Ciobanu

  After reading some examples on stackoverflow, and following some of the answers for my previous questions (1), I've eventually come with a "strategy" for this. I've come to this: 1) Have a declare section in the .h file. Here I will define the data-structure, and the accesing interface. Eg.: /** * LIST DECLARATION. (DOUBLE LINKED LIST) */ #define NM_TEMPLATE_DECLARE_LIST(type) \ typedef struct nm_list_elem_##type##_s { \ type data; \ struct nm_list_elem_##type##_s *next; \ struct nm_list_elem_##type##_s *prev; \ } nm_list_elem_##type ; \ typedef struct nm_list_##type##_s { \ unsigned int size; \ nm_list_elem_##type *head; \ nm_list_elem_##type *tail; \ int (*cmp)(const type e1, const type e2); \ } nm_list_##type ; \ \ nm_list_##type *nm_list_new_##type##_(int (*cmp)(const type e1, \ const type e2)); \ \ (...other functions ...) 2) Wrap the functions in the interface inside MACROS: /** * LIST INTERFACE */ #define nm_list(type) \ nm_list_##type #define nm_list_elem(type) \ nm_list_elem_##type #define nm_list_new(type,cmp) \ nm_list_new_##type##_(cmp) #define nm_list_delete(type, list, dst) \ nm_list_delete_##type##_(list, dst) #define nm_list_ins_next(type,list, elem, data) \ nm_list_ins_next_##type##_(list, elem, data) (...others...) 3) Implement the functions: /** * LIST FUNCTION DEFINITIONS */ #define NM_TEMPLATE_DEFINE_LIST(type) \ nm_list_##type *nm_list_new_##type##_(int (*cmp)(const type e1, \ const type e2)) \ {\ nm_list_##type *list = NULL; \ list = nm_alloc(sizeof(*list)); \ list->size = 0; \ list->head = NULL; \ list->tail = NULL; \ list->cmp = cmp; \ }\ void nm_list_delete_##type##_(nm_list_##type *list, \ void (*destructor)(nm_list_elem_##type elem)) \ { \ type data; \ while(nm_list_size(list)){ \ data = nm_list_rem_##type(list, tail); \ if(destructor){ \ destructor(data); \ } \ } \ nm_free(list); \ } \ (...others...) In order to use those constructs, I have to create two files (let's call them templates.c and templates.h) . In templates.h I will have to NM_TEMPLATE_DECLARE_LIST(int), NM_TEMPLATE_DECLARE_LIST(double) , while in templates.c I will need to NM_TEMPLATE_DEFINE_LIST(int) , NM_TEMPLATE_DEFINE_LIST(double) , in order to have the code behind a list of ints, doubles and so on, generated. By following this strategy I will have to keep all my "template" declarations in two files, and in the same time, I will need to include templates.h whenever I need the data structures. It's a very "centralized" solution. Do you know other strategy in order to "imitate" (at some point) templates in C++ ? Do you know a way to improve this strategy, in order to keep things in more decentralized manner, so that I won't need the two files: templates.c and templates.h ?

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• Benchmark of Java Try/Catch Block

  - by hectorg87

  I know that going into a catch block has some significance cost when executing a program, however, I was wondering if entering a try{} block also had any impact so I started looking for an answer in google with many opinions, but no benchmarking at all. Some answers I found were: Java try/catch performance, is it recommended to keep what is inside the try clause to a minimum? Try Catch Performance Java Java try catch blocks However they didn't answer my question with facts, so I decided to try it for myself. Here's what I did. I have a csv file with this format: host;ip;number;date;status;email;uid;name;lastname;promo_code; where everything after status is optional and will not even have the corresponding ; , so when parsing a validation has to be done to see if the value is there, here's where the try/catch issue came to my mind. The current code that in inherited in my company does this: StringTokenizer st=new StringTokenizer(line,";"); String host = st.nextToken(); String ip = st.nextToken(); String number = st.nextToken(); String date = st.nextToken(); String status = st.nextToken(); String email = ""; try{ email = st.nextToken(); }catch(NoSuchElementException e){ email = ""; } and it repeats what it's done for email with uid, name, lastname and promo_code. and I changed everything to: if(st.hasMoreTokens()){ email = st.nextToken(); } and in fact it performs faster. When parsing a file that doesn't have the optional columns. Here are the average times: --- Trying:122 milliseconds --- Checking:33 milliseconds however, here's what confused me and the reason I'm asking: When running the example with values for the optional columns in all 8000 lines of the CSV, the if() version still performs better than the try/catch version, so my question is Does really the try block does not have any performance impact on my code? The average times for this example are: --- Trying:105 milliseconds --- Checking:43 milliseconds Can somebody explain what's going on here? Thanks a lot

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• Code Golf: Countdown Number Game

  - by Noldorin

  Challenge Here is the task, inspired by the well-known British TV game show Countdown. The challenge should be pretty clear even without any knowledge of the game, but feel free to ask for clarifications. And if you fancy seeing a clip of this game in action, check out this YouTube clip. It features the wonderful late Richard Whitely in 1997. You are given 6 numbers, chosen at random from the set {1, 2, 3, 4, 5, 6, 8, 9, 10, 25, 50, 75, 100}, and a random target number between 100 and 999. The aim is to make use the six given numbers and the four common arithmetic operations (addition, subtraction, multiplication, division; all over the rational numbers) to generate the target - or as close as possible either side. Each number may only be used once at most, while each arithmetic operator may be used any number of times (including zero.) Note that it does not matter how many numbers are used. Write a function that takes the target number and set of 6 numbers (can be represented as list/collection/array/sequence) and returns the solution in any standard numerical notation (e.g. infix, prefix, postfix). The function must always return the closest-possible result to the target, and must run in at most 1 minute on a standard PC. Note that in the case where more than one solution exists, any single solution is sufficient. Examples: {50, 100, 4, 2, 2, 4}, target 203 e.g. 100 * 2 + 2 + (4 / 4) e.g. (100 + 50) * 4 * 2 / (4 + 2) {25, 4, 9, 2, 3, 10}, target 465 e.g. (25 + 10 - 4) * (9 * 2 - 3) {9, 8, 10, 5, 9, 7), target 241 e.g. ((10 + 9) * 9 * 7) + 8) / 5 Rules Other than mentioned in the problem statement, there are no further restrictions. You may write the function in any standard language (standard I/O is not necessary). The aim as always is to solve the task with the smallest number of characters of code. Saying that, I may not simply accept the answer with the shortest code. I'll also be looking at elegance of the code and time complexity of the algorithm! My Solution I'm attempting an F# solution when I find the free time - will post it here when I have something! Format Please post all answers in the following format for the purpose of easy comparison: Language Number of characters: ??? Fully obfuscated function: (code here) Clear (ideally commented) function: (code here) Any notes on the algorithm/clever shortcuts it takes.

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• NVIDIA graphics driver in Ubuntu 12.04

  - by user924501

  So my overall goal is that I want to be able to code with CUDA enabled applications. However, upon many days of searching, using installation walkthroughs, and reinstalling countless times after driver failure... I'm now here as a last resort. I cannot get Ubuntu 12.04 LTS to install the NVIDIA 295.59 driver for my GeForce GT 540M NVIDIA graphics card. My main system specs is as follows... (I believe having the Intel processor may be the problem) DELL Laptop XPS L502X Intel® Core™ i7-2620M CPU @ 2.70GHz × 4 Intel Integrated Graphics 64 bit NVIDIA GeForce GT 540M Ubuntu 12.04 LTS All other specs are irrelevant unless I forgot something? Methods Tried: aptitude install nvidia-current (all packages) Results: Nothing really happened. Nothing in the additional drivers menu appeared, nor was the NVIDIA X Server settings application allowing access because it thought there was no NVIDIA X Server installed. Downloaded driver from nvidia.com. Set nomodeset in the grub boot menu through /boot/grub/grub.cfg Went to console and turned off lightdm. Installed the driver, but it said the pre-install failed? (mean anything?) Started up lightdm again. Results: NVIDIA X Server settings still didn't notice it. Even tried to do nvidia-xconfig multiple times. I also went into the config file to make sure the driver setting said "nvidia". aptitude install nvidia-173 (all packages) Results: Couldn't find the xorg-video-abi-10 virtual package. It was nowhere to be found and the ubuntu forums everywhere had no answers. Lots of people were having this problem. This is easily done in windows, simply download the driver and debug in visual studio with no problems at all. I'd like clear step-by-step instructions on how I should go about this. I'm relatively new to linux but I can find my way around pretty well so you aren't talking to a straight-up beginner. Also, if you think another thread may have the answer please post because I was having a hard time looking for my specific type of problem. TL;DR I want to have access to my GPU so I can code with CUDA while in Ubuntu 12.04 on my 64 bit laptop that also has Intel integrated graphics on the processor. Solution: sudo apt-add-repository ppa:ubuntu-x-swat/x-updates && sudo apt-get update && sudo apt-get upgrade && sudo apt-get install nvidia-current

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• Multiple choice test GUI with serialization of Q&A

  - by Bobby

  I'm working on a project for school in Java programming. I need to design a GUI that will take in questions and answers and store them in a file. It should be able to contain an unlimited number of questions. We have covered binary I/O. How do I write the input they give to a file? How would I go about having them add multiple questions from this GUI? package multiplechoice; import java.awt.*; import javax.swing.*; public class MultipleChoice extends JFrame { public MultipleChoice() { /* * Setting Layout */ setLayout(new GridLayout(10,10)); /* * First Question */ add(new JLabel("What is the category of the question?: ")); JTextField category = new JTextField(); add(category); add(new JLabel("Please enter the question you wish to ask: ")); JTextField question = new JTextField(); add(question); add(new JLabel("Please enter the correct answer: ")); JTextField correctAnswer = new JTextField(); add(correctAnswer); add(new JLabel("Please enter a reccomended answer to display: ")); JTextField reccomendedAnswer = new JTextField(); add(reccomendedAnswer); add(new JLabel("Please enter a choice for multiple choice option " + "A")); JTextField A = new JTextField(); add(A); add(new JLabel("Please enter a choice for multiple choice option " + "B")); JTextField B = new JTextField(); add(B); add(new JLabel("Please enter a choice for multiple choice option " + "C")); JTextField C = new JTextField(); add(C); add(new JLabel("Please enter a choice for multiple choice option " + "D")); JTextField D = new JTextField(); add(D); add(new JButton("Compile Questions")); add(new JButton("Next Question")); } public static void main(String[] args) { /* * Creating JFrame to contain questions */ FinalProject frame = new FinalProject(); // FileOutputStream output = new FileOutputStream("Questions.dat"); JPanel panel = new JPanel(); // button.setLayout(); // frame.add(panel); panel.setSize(100,100); // button.setPreferredSize(new Dimension(100,100)); frame.setTitle("FinalProject"); frame.setSize(600, 400); frame.setLocationRelativeTo(null); // Center the frame frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setVisible(true); } }

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• c++ global operator not playing well with template class

  - by John

  ok, i found some similar posts on stackoverflow, but I couldn't find any that pertained to my exact situation and I was confused with some of the answers given. Ok, so here is my problem: I have a template matrix class as follows: template <typename T, size_t ROWS, size_t COLS> class Matrix { public: template<typename, size_t, size_t> friend class Matrix; Matrix( T init = T() ) : _matrix(ROWS, vector<T>(COLS, init)) { /*for( int i = 0; i < ROWS; i++ ) { _matrix[i] = new vector<T>( COLS, init ); }*/ } Matrix<T, ROWS, COLS> & operator+=( const T & value ) { for( vector<T>::size_type i = 0; i < this->_matrix.size(); i++ ) { for( vector<T>::size_type j = 0; j < this->_matrix[i].size(); j++ ) { this->_matrix[i][j] += value; } } return *this; } private: vector< vector<T> > _matrix; }; and I have the following global function template: template<typename T, size_t ROWS, size_t COLS> Matrix<T, ROWS, COLS> operator+( const Matrix<T, ROWS, COLS> & lhs, const Matrix<T, ROWS, COLS> & rhs ) { Matrix<T, ROWS, COLS> returnValue = lhs; return returnValue += lhs; } To me, this seems to be right. However, when I try to compile the code, I get the following error (thrown from the operator+ function): binary '+=' : no operator found which takes a right-hand operand of type 'const matrix::Matrix<T,ROWS,COLS>' (or there is no acceptable conversion) I can't figure out what to make of this. Any help if greatly appreciated!

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• Is MySQL Replication Appropriate in this case?

  - by MJB

  I have a series of databases, each of which is basically standalone. It initially seemed like I needed a replication solution, but the more I researched it, the more it felt like replication was overkill and not useful anyway. I have not done MySQL replication before, so I have been reading up on the online docs, googling, and searching SO for relevant questions, but I can't find a scenario quite like mine. Here is a brief description of my issue: The various databases almost never have a live connection to each other. They need to be able to "sync" by copying files to a thumb drive and then moving them to the proper destination. It is OK for the data to not match exactly, but they should have the same parent-child relationships. That is, if a generated key differs between databases, no big deal. But the visible data must match. Timing is not critical. Updates can be done a week later, or even a month later, as long as they are done eventually. Updates cannot be guaranteed to be in the proper order, or in any order for that matter. They will be in order from each database; just not between databases. Rather than a set of master-slave relationships, it is more like a central database (R/W) and multiple remote databases (also R/W). I won't know how many remote databases I have until they are created. And the central DB won't know that a database exists until data arrives from it. (To me, this implies I cannot use the method of giving each its own unique identity range to guarantee uniqueness in the central database.) It appears to me that the bottom line is that I don't want "replication" so much as I want "awareness". I want the central database to know what happened in the remote databases, but there is no time requirement. I want the remote databases to be aware of the central database, but they don't need to know about each other. WTH is my question? It is this: Does this scenario sound like any of the typical replication scenarios, or does it sound like I have to roll my own? Perhaps #7 above is the only one that matters, and given that requirement, out-of-the-box replication is impossible. EDIT: I realize that this question might be more suited to ServerFault. I also searched there and found no answers to my questions. And based on the replication questions I did find both on SO and SF, it seemed that the decision was 50-50 over where to put my question. Sorry if I guessed wrong.

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• Problem with pointers and getstring function

  - by volting

  I am trying to write a function to get a string from the uart1. Its for an embedded system so I don't want to use malloc. The pointer that is passed to the getstring function seems to point to garbage after the gets_e_uart1() is called. I don't use pointers too often so I'm sure it is something really stupid and trivial that Im doing wrong. Regards, V int main() { char *ptr = 0; while(1) { gets_e_uart1(ptr, 100); puts_uart1(ptr); } return 0; }*end main*/ //------------------------------------------------------------------------- //gets a string and echos it //returns 0 if there is no error char getstring_e_uart1(char *stringPtr_, const int SIZE_) { char buffer_[SIZE_]; stringPtr_ = buffer_; int start_ = 0, end_ = SIZE_ - 1; char errorflag = 0; /*keep geting chars until newline char recieved*/ while((buffer_[start_++] = getchar_uart1())!= 0x0D) { putchar_uart1(buffer_[start_]);//echo it /*check for end of buffer wraparound if neccesary*/ if(start_ == end_) { start_ = 0; errorflag = 1; } } putchar_uart1('\n'); putchar_uart1('\r'); /*check for end of buffer wraparound if neccesary*/ if(start_ == end_) { buffer_[0] = '\0'; errorflag = 1; } else { buffer_[start_++] = '\0'; } return errorflag; } Update: I decided to go with approach of passing a pointer an array to the function. This works nicely, thanks to everyone for the informative answers. Updated Code: //------------------------------------------------------------------------- //argument 1 should be a pointer to an array, //and the second argument should be the size of the array //gets a string and echos it //returns 0 if there is no error char getstring_e_uart1(char *stringPtr_, const int SIZE_) { char *startPtr_ = stringPtr_; char *endPtr_ = startPtr_ + (SIZE_ - 1); char errorflag = 0; /*keep geting chars until newline char recieved*/ while((*stringPtr_ = getchar_uart1())!= 0x0D) { putchar_uart1(*stringPtr_);//echo it stringPtr_++; /*check for end of buffer wraparound if neccesary*/ if(stringPtr_ == endPtr_) { stringPtr_ = startPtr_; errorflag = 1; } } putchar_uart1('\n'); putchar_uart1('\r'); /*check for end of buffer wraparound if neccesary*/ if(stringPtr_ == endPtr_) { stringPtr_ = startPtr_; *stringPtr_ = '\0'; errorflag = 1; } else { *stringPtr_ = '\0'; } return errorflag; }

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• How much time should it take to find the sum of all prime numbers less than 2 million?

  - by Shahensha

  I was trying to solve this Project Euler Question. I implemented the sieve of euler as a helper class in java. It works pretty well for the small numbers. But when I input 2 million as the limit it doesn't return the answer. I use Netbeans IDE. I waited for a lot many hours once, but it still didn't print the answer. When I stopped running the code, it gave the following result Java Result: 2147483647 BUILD SUCCESSFUL (total time: 2,097 minutes 43 seconds) This answer is incorrect. Even after waiting for so much time, this isn't correct. While the same code returns correct answers for smaller limits. Sieve of euler has a very simple algo given at the botton of this page. My implementation is this: package support; import java.util.ArrayList; import java.util.List; /** * * @author admin */ public class SieveOfEuler { int upperLimit; List<Integer> primeNumbers; public SieveOfEuler(int upperLimit){ this.upperLimit = upperLimit; primeNumbers = new ArrayList<Integer>(); for(int i = 2 ; i <= upperLimit ; i++) primeNumbers.add(i); generatePrimes(); } private void generatePrimes(){ int currentPrimeIndex = 0; int currentPrime = 2; while(currentPrime <= Math.sqrt(upperLimit)){ ArrayList<Integer> toBeRemoved = new ArrayList<Integer>(); for(int i = currentPrimeIndex ; i < primeNumbers.size() ; i++){ int multiplier = primeNumbers.get(i); toBeRemoved.add(currentPrime * multiplier); } for(Integer i : toBeRemoved){ primeNumbers.remove(i); } currentPrimeIndex++; currentPrime = primeNumbers.get(currentPrimeIndex); } } public List getPrimes(){ return primeNumbers; } public void displayPrimes(){ for(double i : primeNumbers) System.out.println(i); } } I am perplexed! My questions is 1) Why is it taking so much time? Is there something wrong in what I am doing? Please suggest ways for improving my coding style, if you find something wrong.

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