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• Computing, storing, and retrieving values to and from an N-Dimensional matrix

  - by Adam S

  This question is probably quite different from what you are used to reading here - I hope it can provide a fun challenge. Essentially I have an algorithm that uses 5(or more) variables to compute a single value, called outcome. Now I have to implement this algorithm on an embedded device which has no memory limitations, but has very harsh processing constraints. Because of this, I would like to run a calculation engine which computes outcome for, say, 20 different values of each variable and stores this information in a file. You may think of this as a 5(or more)-dimensional matrix or 5(or more)-dimensional array, each dimension being 20 entries long. In any modern language, filling this array is as simple as having 5(or more) nested for loops. The tricky part is that I need to dump these values into a file that can then be placed onto the embedded device so that the device can use it as a lookup table. The questions now, are: What format(s) might be acceptable for storing the data? What programs (MATLAB, C#, etc) might be best suited to compute the data? C# must be used to import the data on the device - is this possible given your answer to #1?

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• Python vs all the major professional languages [closed]

  - by Matt

  I've been reading up a lot lately on comparisons between Python and a bunch of the more traditional professional languages - C, C++, Java, etc, mainly trying to find out if its as good as those would be for my own purposes. I can't get this thought out of my head that it isn't good for 'real' programming tasks beyond automation and macros. Anyway, the general idea I got from about two hundred forum threads and blog posts is that for general, non-professional-level progs, scripts, and apps, and as long as it's a single programmer (you) writing it, a given program can be written quicker and more efficiently with Python than it could be with pretty much any other language. But once its big enough to require multiple programmers or more complex than a regular person (read: non-professional) would have any business making, it pretty much becomes instantly inferior to a million other languages. Is this idea more or less accurate? (I'm learning Python for my first language and want to be able to make any small app that I want, but I plan on learning C eventually too, because I want to get into driver writing eventually. So I've been trying to research each ones strengths and weaknesses as much as I can.) Anyway, thanks for any input

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• What is the nicest way to parse this in C++ ?

  - by ereOn

  Hi, In my program, I have a list of "server address" in the following format: host[:port] The brackets here, indicate that the port is optional. host can be a hostname, an IPv4 or IPv6 address. port, if present can be a numeric port number or a service string (like: "http" or "ssh"). If port is present and host is an IPv6 address, host must be in "bracket-enclosed" notation (Example: [::1]) Here are some valid examples: localhost localhost:11211 127.0.0.1:http [::1]:11211 ::1 [::1] And an invalid example: ::1:80 // Invalid: Is this the IPv6 address ::1:80 and a default port, or the IPv6 address ::1 and the port 80 ? ::1:http // This is not ambigous, but for simplicity sake, let's consider this is forbidden as well. My goal is to separate such entries in two parts (obviously host and port). I don't care if either the host or port are invalid as long as they don't contain a : (290.234.34.34.5 is ok for host, it will be rejected in the next process); I just want to separate the two parts, or if there is no port part, to know it somehow. I tried to do something with std::stringstream but everything I come up to seems hacky and not really elegant. How would you do this in C++ ? I don't mind answers in C but C++ is prefered. Any boost solution is welcome as well. Thank you.

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• Repository layout and sparse checkouts

  - by chuanose

  My team is considering to move from Clearcase to Subversion and we are thinking of organising the repository like this: \trunk\project1 \trunk\project2 \trunk\project3 \trunk\staticlib1 \trunk\staticlib2 \trunk\staticlib3 \branches\.. \tags\.. The issue here is that we have lots of projects (1000+) and each project is a dll that links in several common static libraries. Therefore checking out everything in trunk is a non-starter as it will take way too long (~2 GB), and is unwieldy for branching. Using svn:externals to pull out relevant folders for each project doesn't seem ideal because it results in several working copies for each static library folder. We also cannot do an atomic commit if the changes span the project and some static libraries. Sparse checkouts sounds very suitable for this as we can write a script to pull out only the required directories. However when we want to merge changes from a branch back to the trunk we will need to first check out a full trunk. Wonder if there is some advice on 1) a better repository organization or 2) a way to merge over branch changes to a trunk working copy that is sparse?

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• How to "pin" C++/CLI pointers

  - by Kumar

  I am wrapping up a class which reading a custom binary data file and makes the data available to a .net/c# class However a couple of lines down the code, i start getting the memory access violation error which i believe is due to the GC moving memory around, the class is managed Here's the code if ( ! reader.OpenFile(...) ) return ; foreach(string fieldName in fields) { int colIndex = reader.GetColIndex( fieldName ); int colType = reader.GetColType( colIndex ); // error is raised here on 2nd iteration } for ( int r = 0 ; r < reader.NumFields(); r++ ) { foreach(string fieldName in fields) { int colIndex = reader.GetColIndex( fieldName ); int colType = reader.GetColType( colIndex ); // error is raised here on 2nd iteration switch ( colType ) { case 0 : // INT processField( r, fieldName, reader.GetInt(r,colIndex) ); break ; .... } } } .... i've looked at interior_ptr, pin_ptr but they give an error c3160 cannot be in a managed class Any workaround ? BTW, this is my 1st C++ program in a very long time !

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• JPA - Can an @JoinColumn be an @Id as well? SerializationException occurs.

  - by Shivago

  Hi everyone, I am trying to use an @JoinColumn as an @Id using JPA and I am getting SerializationExceptions, "Could not serialize." UserRole.java: @Entity @Table(name = "authorities") public class UserRole implements Serializable { @Column(name = "authority") private String role; @Id @ManyToOne @JoinColumn(name = "username") private User owner; ... } User.java: @Entity @Table(name = "users") public class User implements Serializable { @Id @GeneratedValue protected Long id; @Column(name = "username") protected String email; @OneToMany(mappedBy = "owner", fetch = FetchType.LAZY, cascade = CascadeType.ALL) protected Set<UserRole> roles = new HashSet<UserRole>(); .... } "username" is set up as a unique index in my Users table but not as the primary key. Is there any way to make "username" act as the ID for UserRole? I don't want to introduce a numeric key in UserRole. Have I totally lost the plot here? I am using MySQL and Hibernate under the hood.

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• How do you unit test new code that uses a bunch of classes that cannot be instantiated in a test har

  - by trendl

  I'm writing a messaging layer that should handle communication with a third party API. The API has a bunch of classes that cannot be easily (if at all) instantiated in a test harness. I decided to wrap each class that I need in my unit tests with an adapter/wrapper and expose the members I need through this adapter class. Often I need to expose the wrapped type as well which I do by exposing it as an object. I have also provided an interface for for each or the adapter classes to be able to use them with a mocking framework. This way I can substitute the classes in test for whatever I need. The downside is that I have a bunch of adapter classes that so far server no other reason but testing. For me this is a good reason by itself but others may find this not enough. Possibly, when I write an implementation for another third party vendor's API, I may be able to reuse much of my code and only provide the adapters specific to the vendor's API. However, this is a bit of a long shot and I'm not actually sure it will work. What do you think? Is this approach viable or am I writing unnecessary code that serves no real purpose? Let me say that I do want to write unit tests for my messaging layer and I do now know how to do it otherwise.

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• Circumvent c++ null-terminated string frustration

  - by ypnos

  I'm using boost::program_options and it suffers from the same as many other c++ libs, even std itself: It still uses C-style null-terminated strings, because nobody really likes the weak std::string. The method in question is: options_description_easy_init& operator()(const char* name, const value_semantic* s, const char* description); The typical use case is just fine: options.add_options() ("graphical", bool_switch(&isGraphical)->default_value(false), "Show any graphical output during runtime") However, I need the name of the option to be set dynamically. The reason is that in some cases I nead a custom prefix, which is added to the string by my function std::string key(const std::string& k): options.add_options() (key("graphical"), bool_switch(&isGraphical)->default_value(false), "Show any graphical output during runtime") This fails. I could now use c_str() on the std::string but that's evil -- I don't know how long program_options keeps the variable around and if my string is still alive when needed. I could also reserve memory in a buffer etc. and hand in that. The buffer is never freed and it sucks/is evil. Is there anything else I can do to circumvent the C-style string mess in this situation?

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• How does Crystal Reports Runtime Licensing work?

  - by GluedHands

  I am designing an application in C# and I want to use some Crystal Reports in my application. I am selling this application as freelance to a small business. This is my first program that I have ever sold. I have Crystal Reports 2008 that I am using to design reports with. Do I need to get any kind of licensing from Business Objects to include the Crystal Reports Runtime for report printing in my application? Or do I not need to worry about it as long as I have a licensed version of Crystal Reports 2008 on my development machine. The client would only need be able to print the reports that I have designed on my machine, not design their own. The reports would be saved as a file. The application will load the saved report and print it with provided data. I did see this article which answers the most part of my question. However, it does not include whether it covers loading saved report documents? Any additional related information for a commercial product newbie is gladly appreciated.

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• Benefits of "Don't Fragment" on TCP Packets?

  - by taspeotis

  One of our customers is having trouble submitting data from our application (on their PC) to a server (different geographical location). When sending packets under 1100 bytes everything works fine, but above this we see TCP retransmitting the packet every few seconds and getting no response. The packets we are using for testing are about 1400 bytes (but less than 1472). I can send an ICMP ping to www.google.com that is 1472 bytes and get a response (so it's not their router/first few hops). I found that our application sets the DF flag for these packets, and I believe a router along the way to the server has an MTU less than/equal to 1100 and dropping the packet. This affects 1 client in 5000, but since everybody's routes will be different this is expected. The data is a SOAP envelope and we expect a SOAP response back. I can't justify WHY we do it, the code to do this was written by a previous developer. So... Are there are benefits OR justification to setting the DF flag on TCP packets for application data? I can think of reasons it is needed for network diagnostics applications but not in our situation (we want the data to get to the endpoint, fragmented or not). One of our sysadmins said that it might have something to do with us using SSL, but as far as I know SSL is like a stream and regardless of fragmentation, as long as the stream is rebuilt at the end, there's no problem. If there's no good justification I will be changing the behaviour of our application. Thanks in advance.

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• What's a good way to do testing a plug-in on multiple Windows and Outlook versions?

  - by Andrei

  Hello, We're building a plug-in for Outlook that should work on multiple Windows versions (XP, Vista, 7) and also with different Outlook versions (2003, 2007, 2010). The testing problem I am facing right now, is that I can't figure out a good/convenient/thorough way to test the application on multiple Windows and Outlook versions. At the moment, I have a VirtualBox which runs many virtual machines, with different Windows versions and Outlook versions. So I would have a virtual machine with Windows 7 testing Outlook 2010, and another one with Windows 7 testing Outlook 2007, Windows Vista with Outlook 2010 and so on, going through some of the possible combinations. It kind of gets the job done, although it is cumbersome and takes a long time to test. Some of the testing included in the application is unit testing, but this is also rather tied in with the machine I test it on (windows 7 with outlook 2010). For example, I was using ManagementObject recently, which worked fine on my system (and thus passed the unit test for that method), however, using that object threw an exception in another person's system, which crashed the application. I work on Visual Studio 2010 Ultimate. The questions: Is there a more elegant way to make the testing process more streamline and more efficient? Any other testing methods you recommend? How would you deal with this problem? Thanks! Looking forward to your replies.

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• Is there any time estimation about sqlite3's open speed?

  - by sxingfeng

  I am using SQLite3 in C++, I found the opening time of sqlite seems unstable at the first time( I mean ,open windows and open the db at the first time) It takes a long tiom on 50M db, about 10s in windows? and vary on different times. Has any one met the same problem? I am writting an desktop application in windows, so the openning speed is really important for me. Thanks in advance! int nRet; #if defined(_UNICODE) || defined(UNICODE) nRet = sqlite3_open16(szFile, &mpDB); // not tested under window 98 #else // For Ansi Version //*************- Added by Begemot szFile must be in unicode- 23/03/06 11:04 - **** OSVERSIONINFOEX osvi; ZeroMemory(&osvi, sizeof(OSVERSIONINFOEX)); osvi.dwOSVersionInfoSize = sizeof(OSVERSIONINFOEX); GetVersionEx ((OSVERSIONINFO *) &osvi); if ( osvi.dwMajorVersion == 5) { WCHAR pMultiByteStr[MAX_PATH+1]; MultiByteToWideChar( CP_ACP, 0, szFile, _tcslen(szFile)+1, pMultiByteStr, sizeof(pMultiByteStr)/sizeof(pMultiByteStr[0]) ); nRet = sqlite3_open16(pMultiByteStr, &mpDB); } else nRet = sqlite3_open(szFile,&mpDB); #endif //************************* if (nRet != SQLITE_OK) { LPCTSTR szError = (LPCTSTR) _sqlite3_errmsg(mpDB); throw CppSQLite3Exception(nRet, (LPTSTR)szError, DONT_DELETE_MSG); } setBusyTimeout(mnBusyTimeoutMs);

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• NHibernate + Cannot insert the value NULL into...

  - by mybrokengnome

  I've got a MS-SQL database with a table created with this code CREATE TABLE [dbo].[portfoliomanager]( [idPortfolioManager] [int] NOT NULL PRIMARY KEY IDENTITY, [name] [varchar](45) NULL ) so that idPortfolioManager is my primary key and also auto-incrementing. Now on my Windows WPF application I'm using NHibernate to help with adding/updating/removing/etc. data from the database. Here is the class that should be connecting to the portfoliomanager table namespace PortfolioManager { [Class(Table="portfoliomanager",NameType=typeof(PortfolioManagerClass))] public class PortfolioManagerClass { [Id(Name = "idPortfolioManager")] [Generator(1, Class = "identity")] public virtual int idPortfolioManager { get; set; } [NHibernate.Mapping.Attributes.Property(Name = "name")] public virtual string name { get; set; } public PortfolioManagerClass() { } } } and some short code to try and insert something PortfolioManagerClass portfolio = new PortfolioManagerClass(); Portfolio.name = "Brad's Portfolios"; The problem is, when I try running this, I get this error: {System.Data.SqlClient.SqlException: Cannot insert the value NULL into column 'idPortfolioManager', table 'PortfolioManagementSystem.dbo.portfoliomanager'; column does not allow nulls. INSERT fails. The statement has been terminated... with an outer exception of {"could not insert: [PortfolioManager.PortfolioManagerClass][SQL: INSERT INTO portfoliomanager (name) VALUES (?); select SCOPE_IDENTITY()]"} I'm hoping this is the last error I'll have to solve with NHibernate just to get it to do something, it's been a long process. Just as a note, I've also tried setting Class="native" and unsaved-value="0" with the same error. Thanks! Edit: Ok removing the 1, from Generator actually allows the program to run (not sure why that was even in the samples I was looking at) but it actually doesn't get added to the database. I logged in to the server and ran the sql server profiler tool and I never see the connection coming through or the SQL its trying to run, but NHibernate isn't throwing an error anymore. Starting to think it would be easier to just write SQL statements myself :(

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• Calling a WPF Appliaction and modify exposed properties?

  - by Justin

  I have a WPF Keyboard Application, it is developed in such a way that an application could call it and modify its properties to adapt the Keyboard to do what it needs to. Right now I have a file *.Keys.Set which tells the appliaction (on open) to style itself according to that new style. I know this file could be passed as a command line argument into the appliaction. That would not be a problem. My concern is, is thier a way via a managed environment to change the properties of the executable as long as they are exposed properly, an example: 'Creates a new instance of the Keyboard Appliaction Dim e_key as new WpfAppliaction("C:\egt\components\keyboard.exe") 'Sets the style path e_key.SetStylePath("c:\users\joe\apps\me\default.keys.set") e_key.Refresh() 'Applies the style e_key.HideMenu() 'Hides the menu e_key.ShowDeck("PIN") 'Shows the custom "deck" of keyboard keys the developer 'Created in the style appliaction. ''work with events and resposne 'Clear the instance from memory e_key.close e_key.dispose e_key = nothing This would allow my application to become easily accessible to other Touch Screen Application Developers, allowing them to use my key_board and keep the functionality they need. It seems like it might be possible because (name of executable).application shows all the exposed functions, properties, and values. I just have never done this before. Any help would be appreciated, thank you in advance.

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• Can someone please explain Cursor in android ?

  - by Prabhat

  Can some one explain how the cursor exactly works ? Or the flow of the following part of the code ? I know that this is sub activity and all but I did not understand how Cursor works exactly. final Uri data = Uri.parse("content://contacts/people/"); final Cursor c = managedQuery(data, null, null, null, null); String[] from = new String[] { People.NAME }; int[] to = new int[] { R.id.itemTextView }; SimpleCursorAdapter adapter = new SimpleCursorAdapter(this,R.layout.listitemlayout, c, from, to); ListView lv = (ListView) findViewById(R.id.contactListView); lv.setAdapter(adapter); lv.setOnItemClickListener(new OnItemClickListener() { public void onItemClick(AdapterView<?> parent, View view, int pos, long id) { c.moveToPosition(pos); int rowId = c.getInt(c.getColumnIndexOrThrow("_id")); Uri outURI = Uri.parse(data.toString() + rowId); Intent outData = new Intent(); outData.setData(outURI); setResult(Activity.RESULT_OK, outData); finish(); } }); Thanks.

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• Margically appearing margin in footer. Could use some fresh eye's on this.

  - by Banderdash

  Hi chaps! Got a nearly finished coded comp here: http://clients.pixelbleed.net/biodesign/ I realize it's not completely valid, what with my nesting of li's and ul's within A tags. Unfortunately that's the way it has to be. My issue is with the very bottom of the footer. It has a space showing the body's background color beneath it. Tried a number of things and this space after the black link bar on the very bottom is a resistant little bugger. Ideally the black box on the bottom should rest against the very base of the view-port, at least when the content is sufficiently long--which it is in this case. If someone would like to take a quick peak at my source and give me some ideas I'd be very grateful. The CSS can be found here: http://clients.pixelbleed.net/biodesign/css/core.css And, yes, I've tried removing the height:100%. Makes no difference it seems. I do believe the issue to be with the footer, as when I remove these Div's the content rests as it should. Just don't see anything in my CSS to cause the margin/spacing issue though. Thanks so much.

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• PDFBox Pagebreak strange Nullpointer exception

  - by schneiti

  I currently try printing out text on multiple pages. For this, I count the number of rows and when they reach a fixed amount a method called pagebreakis executed. After the first pagebreak, when I try setting a font using contentstream.setFont(PDType1Font.HELVETICA, 12); it yields the following errormessage occuring at the described setFont-row. java.lang.NullPointerException at org.apache.pdfbox.pdmodel.edit.PDPageContentStream.setFont(PDPageContentStream.java:321) at com.xy.deu.xy.abc.db.schemavergleich.PDFDocumenter.drawBGCS(PDFDocumenter.java:781) at com.xy.deu.xy.abc.db.schemavergleich.PDFDocumenter.createPDFDocumentation(PDFDocumenter.java:205) at com.xy.deu.xy.abc.db.schemavergleich.MainClass.createPDFandOutput(MainClass.java:361) at com.xy.deu.xy.abc.db.schemavergleich.MainClass.start(MainClass.java:231) at com.xy.deu.xy.abc.db.schemavergleich.MainClass.main(MainClass.java:180) Below is the code that gets executed as the error occurs. ... // If Table gets to long for a page -> pagebreak: if(currentLines > 37) { pageBreak(currentLinePos); // TODO Currently causing app to crash } ... private void pageBreak(int currentLine) throws Exception { contentStream.endText(); contentStream.close(); // Create new page page = new PDPage(PDPage.PAGE_SIZE_A4); doc.addPage( page ); // Create a new font object selecting one of the PDF base fonts font = PDType1Font.HELVETICA; // Start a new content stream which will "hold" the to be created content contentStream = new PDPageContentStream(doc, page); currentLines = 0; mediabox = page.findMediaBox(); contentStream.beginText(); contentStream.moveTextPositionByAmount(startX, startY); contentStream.setFont(PDType1Font.HELVETICA, 12); } Now comes the strange thing: Debugging yields into nothing that is not set. I'll attach a screenshot for you right at the position where the error occurs:

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• The best way to predict performance without actually porting the code?

  - by ardiyu07

  I believe there are people with the same experience with me, where he/she must give a (estimated) performance report of porting a program from sequential to parallel with some designated multicore hardwares, with a very few amount of time given. For instance, if a 10K LoC sequential program was given and executes on Intel i7-3770k (not vectorized) in 100 ms, how long would it take to run if one parallelizes the code to a Tesla C2075 with NVIDIA CUDA, given that all kinds of parallelizing optimization techniques were done? (but you're only given 2-4 days to report the performance? assume that you didn't know the algorithm at all. Or perhaps it'd be safer if we just assume that it's an impossible situation to finish the job) Therefore, I'm wondering, what most likely be the fastest way to give such performance report? Is it safe to calculate solely by the hardware's capability, such as GFLOPs peak and memory bandwidth rate? Is there a mathematical way to calculate it? If there is, please prove your method with the corresponding problem description and the algorithm, and also the target hardwares' specifications. Or perhaps there already exists such tool to (roughly) estimate code porting? (Please don't the answer: 'kill yourself is the fastest way.')

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• Clear listview content?

  - by Slash

  I have a little problem with listview. How do i clear a listview content, knowing that it has a custom adapter? edit : the custom adapter class extends BaseAdapter, it looks like this : import android.app.Activity; import android.content.Context; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.TextView; public class MyAdapter extends BaseAdapter { private Activity activity; private String[] data; private static LayoutInflater inflater=null; public MyAdapter(Activity _a, String[] _str) { activity = _a; data = _str; inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE); } public static class ViewHolder{ public TextView text; } @Override public int getCount() { return data.length; } @Override public Object getItem(int position) { return position; } @Override public long getItemId(int position) { return position; } @Override public View getView(int position, View view, ViewGroup parent) { View v = view; ViewHolder holder; if(v == null) { v = inflater.inflate(R.layout.rowa, null); holder=new ViewHolder(); holder.text=(TextView)v.findViewById(R.id.dexter); v.setTag(holder); }else{ holder=(ViewHolder)v.getTag(); } holder.text.setText(data[position]); return v; } }

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• Help renaming svn repository

  - by rascher

  Here is the deal: I created an SVN repository, say, foo. It is at http://www.example.com/foo. Then I did an svn checkout. I made some updates and changes to my local copy of the code over the week. I haven't committed yet. I realized that I wanted to rename the repository. So I did this: svn copy http://example.com/foo http://example.com/bar svn delete http://example.com/foo I finish my changes (and local svn still thinks I'm working under "foo".) svn commit fails because the repo has been renamed. I try to use svn switch --relocate but it yells at me because svn is awful. I try using the script here to replace "foo" with "bar" in my billion .svn/ folders. This replace is taking a long time. I wonder if something hung? Or maybe sshfs failed? I kill it. Ctrl-C. I look and see that half my files have "foo" and the others have "bar" in the URLs in the sundry .svn/ folders. All I want to do is commit my files with the new name. I could re-checkout the branch, but then I have no way to remember which files I changed, which is why I was using version control in the first place, and svn is so godawful at moving and renaming things. What do I need to do to: Have a "clean" copy of my "bar" svn branch? and, most importantly: Commit the changes I made?

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• C++ Dynamic Allocation Mismatch: Is this problematic?

  - by acanaday

  I have been assigned to work on some legacy C++ code in MFC. One of the things I am finding all over the place are allocations like the following: struct Point { float x,y,z; }; ... void someFunc( void ) { int numPoints = ...; Point* pArray = (Point*)new BYTE[ numPoints * sizeof(Point) ]; ... //do some stuff with points ... delete [] pArray; } I realize that this code is atrociously wrong on so many levels (C-style cast, using new like malloc, confusing, etc). I also realize that if Point had defined a constructor it would not be called and weird things would happen at delete [] if a destructor had been defined. Question: I am in the process of fixing these occurrences wherever they appear as a matter of course. However, I have never seen anything like this before and it has got me wondering. Does this code have the potential to cause memory leaks/corruption as it stands currently (no constructor/destructor, but with pointer type mismatch) or is it safe as long as the array just contains structs/primitive types?

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• How can I make hundreds of simultaneously running processes communicate with a database through one

  - by Olfan

  Long speech short: How can I make hundreds of simultaneously running processes communicate with a database through one or few permanent sessions? The whole story: I once built a number crunching engine that handles vast amounts of large data files by forking off one child after another giving each a small number of files to work on. File locking, progress monitoring and result propagation happen in an Oracle database which all (sub-)processes access at various times using an application-specific module which encapsulates DBI. This worked well at first, but now with higher volumes of input data, the number of database sessions (one per child, and they can be very short-lived) constantly being opened and closed is becoming an issue. I now want to centralise database access so that there are only one or few fixed database sessions which handle all database access for all the (sub-)processes. The presence of the database abstraction module should make the changes easy because the function calls in the worker instances can stay the same. My problem is that I cannot think of a suitable way to enhance said module in order to establish communication between all the processes and the database connector(s). I thought of message queueing, but couldn't come up with a way of connecting a large herd of requestors with one or few database connectors in a way so that bidirectional communication is possible (for collecting the query result). An asynchronous approach could help here in that all requests are written to the same queue and the database connector servicing the request will "call back" to submit the result. But my mind fails me in generating an image clear enough so that I can paint into code. Threading instead of forking might have given me an easier start, but this would now require massive changes to the code base that I'm not prepared to do to a live system. The more I think of it, the more the base idea looks like a pre-forked web server to me only that it doesn't serve web pages but database queries. Any ideas on what to dig into, and where? Sample (pseudo) code to inspire me, links to possibly related articles, ready solutions on CPAN maybe?

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• How to get a checkout-able revision info from subversion?

  - by zhongshu

  I want to check a svn url and to get the latest revision, then checkout it, I don't want to use HEAD because I will compare the latest revision to others. so I use "svn info" to get the "Last Changed Rev" for the url like this: D:\Project>svn info svn://.../branches/.../path Path: ... URL: svn://.../branches/.../path Repository Root: svn://yt-file-srv/ Repository UUID: 9ed5ffd7-7585-a14e-96b2-4aab7121bb21 Revision: 2400 Node Kind: directory Last Changed Author: xxx Last Changed Rev: 2396 Last Changed Date: 2010-03-12 09:31:52 +0800 but, I found the 2396 revision is not checkout-able, because this path is in a branch copied from trunk, and the 2396 is the revision modified in the trunk. so when I use svn checkout -r 2396, I will get a workcopy for the path in the trunk, then I can not do checkin for the branch. D:\Project>svn checkout svn://.../branches/.../path -r 2396 workcopy ..... ..... D:\Project>svn info workcopy Path: workcopy URL: svn://.../trunk/.../path Repository Root: svn://yt-file-srv/ Repository UUID: 9ed5ffd7-7585-a14e-96b2-4aab7121bb21 Revision: 2396 Node Kind: directory Schedule: normal Last Changed Author: xxx Last Changed Rev: 2396 Last Changed Date: 2010-03-12 09:31:52 +0800 So, my question is how to get a checkout-able revision for the branch path, for this example, I want to get 2397 (because 2397 is the revision which copy occur). And I know "svn log" can get the info, but "svn log" output maybe very long and parse it will be difficult than "svn info". I just want know which revision is the latest checkout-able revision for the path.

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• Efficient way to get highly correlated pairs from large data set in Python or R

  - by Akavall

  I have a large data set (Let's say 10,000 variables with about 1000 elements each), we can think of it as 2D list, something like: [[variable_1], [variable_2], ............ [variable_n] ] I want to extract highly correlated variable pairs from that data. I want "highly correlated" to be a parameter that I can choose. I don't need all pairs to be extracted, and I don't necessarily want the most correlated pairs. As long as there is an efficient method that gets me highly correlated pairs I am happy. Also, it would be nice if a variable does not show up in more than one pair. Although this might not be crucial. Of course, there is a brute force way to finding such pairs, but it is too slow for me. I've googled around for a bit and found some theoretical work on this issue, but I wasn't able for find a package that could do what I am looking for. I mostly work in python, so a package in python would be most helpful, but if there exists a package in R that does what I am looking for it will be great. Does anyone know of a package that does the above in Python or R? Or any other ideas? Thank You in Advance

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• please check my MYSQL query & give me advice?

  - by Suba

  select s.s_nric as NRIC,s.s_name as NAME,s.s_psle_eng as PSLE_ENG,s.s_psle_math as PSLE_MATHS,s.s_psle_aggr as PSLE_AGGR, (SELECT re.re_mark FROM si_results re WHERE re.re_code like 'FEEN%' AND re.re_year='2008' AND re.re_semester='2' AND re.re_nric=s.s_nric ) as English_2008, (SELECT re.re_mark FROM si_results re WHERE re.re_code like 'FEMA%' AND re.re_year='2008' AND re.re_semester='2' AND re.re_nric=s.s_nric ) Maths_2008, (SELECT re.re_mark FROM si_results re WHERE re.re_code like 'FEEN%' AND re.re_year='2009' AND re.re_semester='2' AND re.re_nric=s.s_nric ) as English_2009, (SELECT re.re_mark FROM si_results re WHERE re.re_code like 'FEMA%' AND re.re_year='2009' AND re.re_semester='2' AND re.re_nric=s.s_nric ) Maths_2009 ,isc.isc_g_gpa as ISC_GPA from si_student_data as s LEFT JOIN si_isc_gpa as isc ON isc.isc_g_nric=s.s_nric where 1=1 AND s.s_admission_year='2008' GROUP BY s.s_nric ORDER BY s.s_gender,s.s_name asc This is my query. please check my sub query this is my sub query (SELECT re.re_mark FROM si_results re WHERE re.re_code like 'FEEN%' AND re.re_year='2008' AND re.re_semester='2' AND re.re_nric=s.s_nric ) as English_2008, (SELECT re.re_mark FROM si_results re WHERE re.re_code like 'FEMA%' AND re.re_year='2008' AND re.re_semester='2' AND re.re_nric=s.s_nric ) Maths_2008, (SELECT re.re_mark FROM si_results re WHERE re.re_code like 'FEEN%' AND re.re_year='2009' AND re.re_semester='2' AND re.re_nric=s.s_nric ) as English_2009, (SELECT re.re_mark FROM si_results re WHERE re.re_code like 'FEMA%' AND re.re_year='2009' AND re.re_semester='2' AND re.re_nric=s.s_nric ) Maths_2009 When I execute my query, server take long time to execute. So how to make simple? please advice me. Thanks.

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