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• Running an allocation simulation repeatedly breaks after the first run.

  - by Az

  Background I have a bunch of students, their desired projects and the supervisors for the respective projects. I'm running a battery of simulations to see which projects the students end up with, which will allow me to get some useful statistics required for feedback. So, this is essentially a Monte-Carlo simulation where I'm randomising the list of students and then iterating through it, allocating projects until I hit the end of the list. Then the process is repeated again. Note that, within a single session, after each successful allocation of a project the following take place: + the project is set to allocated and cannot be given to another student + the supervisor has a fixed quota of students he can supervise. This is decremented by 1 + Once the quota hits 0, all the projects from that supervisor become blocked and this has the same effect as a project being allocated Code def resetData(): for student in students.itervalues(): student.allocated_project = None for supervisor in supervisors.itervalues(): supervisor.quota = 0 for project in projects.itervalues(): project.allocated = False project.blocked = False The role of resetData() is to "reset" certain bits of the data. For example, when a project is successfully allocated, project.allocated for that project is flipped to True. While that's useful for a single run, for the next run I need to be deallocated. Above I'm iterating through thee three dictionaries - one each for students, projects and supervisors - where the information is stored. The next bit is the "Monte-Carlo" simulation for the allocation algorithm. sesh_id = 1 for trial in range(50): for id in randomiseStudents(1): stud_id = id student = students[id] if not student.preferences: # Ignoring the students who've not entered any preferences for rank in ranks: temp_proj = random.choice(list(student.preferences[rank])) if not (temp_proj.allocated or temp_proj.blocked): alloc_proj = student.allocated_proj_ref = temp_proj.proj_id alloc_proj_rank = student.allocated_rank = rank successActions(temp_proj) temp_alloc = Allocated(sesh_id, stud_id, alloc_proj, alloc_proj_rank) print temp_alloc # Explained break sesh_id += 1 resetData() # Refer to def resetData() above All randomiseStudents(1) does is randomise the order of students. Allocated is a class defined as such: class Allocated(object): def __init__(self, sesh_id, stud_id, alloc_proj, alloc_proj_rank): self.sesh_id = sesh_id self.stud_id = stud_id self.alloc_proj = alloc_proj self.alloc_proj_rank = alloc_proj_rank def __repr__(self): return str(self) def __str__(self): return "%s - Student: %s (Project: %s - Rank: %s)" %(self.sesh_id, self.stud_id, self.alloc_proj, self.alloc_proj_rank) Output and problem Now if I run this I get an output such as this (truncated): 1 - Student: 7720 (Project: 1100241 - Rank: 1) 1 - Student: 7832 (Project: 1100339 - Rank: 1) 1 - Student: 7743 (Project: 1100359 - Rank: 1) 1 - Student: 7820 (Project: 1100261 - Rank: 2) 1 - Student: 7829 (Project: 1100270 - Rank: 1) . . . 1 - Student: 7822 (Project: 1100280 - Rank: 1) 1 - Student: 7792 (Project: 1100141 - Rank: 7) 2 - Student: 7739 (Project: 1100267 - Rank: 1) 3 - Student: 7806 (Project: 1100272 - Rank: 1) . . . 45 - Student: 7806 (Project: 1100272 - Rank: 1) 46 - Student: 7714 (Project: 1100317 - Rank: 1) 47 - Student: 7930 (Project: 1100343 - Rank: 1) 48 - Student: 7757 (Project: 1100358 - Rank: 1) 49 - Student: 7759 (Project: 1100269 - Rank: 1) 50 - Student: 7778 (Project: 1100301 - Rank: 1) Basically, it works perfectly for the first run, but on subsequent runs leading upto the nth run, in this case 50, only a single student-project allocation pair is returned. Thus, the main issue I'm having trouble with is figuring out what is causing this anomalous behaviour especially since the first run works smoothly. Thanks in advance, Az

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• A methology that allows for a single Java code base covering many different versions?

  - by Thorbjørn Ravn Andersen

  I work in a small shop where we have a LOT of legacy Cobol code and where a methology has been adopted to allow us to minimize forking and branching as much as possible. For a given release we have three levels: CORE - bottom layer, this code is common to all releases GROUP - optional code common to several customers. CUSTOMER - optional code specific for a single customer. When a program is needed, it is first searched for in CUSTOMER, then in GROUP and finally in CORE. A given application for us invokes many programs which all are looked for in this sequence (think exe files and PATH under Windows). We also have Java programs interacting with this legacy code, and as the core-group-customer lookup mehchanism does not lend it self easily to Java it has tended to grow in a CVS branch for each customer, requiring much too much maintainance. The Java part and the backend part tend to be developed in parallel. I have been assigned to figure out a way to make the two worlds meet. Essentially we want a Java enviornment which allows us to have a single code base with sources for each release, where we easily can select a group and a customer and work with the application as it goes for that customer, and then easily switch to another codeset and THAT customer. I was thinking of perhaps a scenario with an Eclipse project for each core, customer, and group and then use Project Sets to select those we need for a given scenario. The problem I cannot get my head about, is how we would create robust code in the CORE projects which will work regardless of which group and customer is selected. A Factory class which knows which sub class of a passed Class object to invoke instead of each and every new? Others must have had similar code base management problems. Anybody with experiences to share? EDIT: The conclusion to this problem above has been that CVS needs to be replaced with a source code management system better suited for dealing with many branches concurrently and the migration of source from one component to the other while keeping history. Inspired by the recent migration by slf4j and logback we are currently looking at git as it handles branches very well. We've considered subversion and mercurial too but git appears to be better for single location, multibranched projects. I've asked about Perforce in another question, but my personal inclination is towards open source solutions for something as crucial as this. EDIT: After some more pondering, we've found that our actual pain point is that we use branches in CVS, and that branches in CVS are the easiest to work with if you branch ALL files! The revised conclusion is that we can do this with CVS alone, by switching to a forest of java projects, each corresponding to one of the levels above, and use the Eclipse build paths to tie them together so each CUSTOMER version pulls in the appropriate GROUP and CORE project. We still want to switch to a better versioning system but this is so important a decision so we want to delay it as much as possible. EDIT: I now have a proof-of-concept implementation of the CORE-GROUP-CUSTOMER concept using Google Guice 2.0 - the @ImplementedBy tag is just what we need. I wonder what everybody else does? Using if's all over the place? EDIT: Now I also need this functionality for web applications. Guice was until the JSR-330 is in place. Anybody with versioning experience? EDIT: JSR-330/299 is now in place with the JEE6 reference implementation Weld based on JBoss Seam and I have reimplemented the proof-of-concept with Weld and can see that if we use @Alternative along with ... in beans.xml we can get the behaviour we desire. I.e. provide a new implementation for a given functionality in CORE without changing a bit in the CORE jars. Initial reading up on the Servlet 3.0 specification indicates that it may support the same functionality for web application resources (not code). We will now do initial testing on the real application.

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• Running 32 bit assembly code on a 64 bit Linux & 64 bit Processor : Expalin the anomaly.

  - by claws

  Hello, I'm in an interesting problem.I forgot I'm using 64bit machine & OS and wrote a 32 bit assembly code. I don't know how to write 64 bit code. This is the x86 32-bit assembly code for Gnu Assembler (AT&T syntax) on Linux. #include <asm/unistd.h> #include <syscall.h> #define STDOUT 1 .data hellostr: .ascii "hello wolrd\n"; helloend: .text .globl _start _start: movl $(SYS_write) , %eax //ssize_t write(int fd, const void *buf, size_t count); movl $(STDOUT) , %ebx movl $hellostr , %ecx movl $(helloend-hellostr) , %edx int $0x80 movl $(SYS_exit), %eax //void _exit(int status); xorl %ebx, %ebx int $0x80 ret Now, This code should run fine on a 32bit processor & 32 bit OS right? As we know 64 bit processors are backward compatible with 32 bit processors. So, that also wouldn't be a problem. The problem arises because of differences in system calls & call mechanism in 64-bit OS & 32-bit OS. I don't know why but they changed the system call numbers between 32-bit linux & 64-bit linux. asm/unistd_32.h defines: #define __NR_write 4 #define __NR_exit 1 asm/unistd_64.h defines: #define __NR_write 1 #define __NR_exit 60 Anyway using Macros instead of direct numbers is paid off. Its ensuring correct system call numbers. when I assemble & link & run the program. Its not printing helloworld. In gdb its showing: Program exited with code 01. I don't know how to debug in gdb. using tutorial I tried to debug it and execute instruction by instruction checking registers at each step. its always showing me "program exited with 01". It would be great if some on could show me how to debug this. (gdb) break _start Note: breakpoint -10 also set at pc 0x4000b0. Breakpoint 8 at 0x4000b0 (gdb) start Function "main" not defined. Make breakpoint pending on future shared library load? (y or [n]) y Temporary breakpoint 9 (main) pending. Starting program: /home/claws/helloworld Program exited with code 01. (gdb) info breakpoints Num Type Disp Enb Address What 8 breakpoint keep y 0x00000000004000b0 <_start> 9 breakpoint del y <PENDING> main I tried running strace. This is its output: execve("./helloworld", ["./helloworld"], [/* 39 vars */]) = 0 write(0, NULL, 12 <unfinished ... exit status 1> Explain the parameters of write(0, NULL, 12) system call in the output of strace? What exactly is happening? I want to know the reason why exactly its exiting with exitstatus=1? Can some one please show me how to debug this program using gdb? Why did they change the system call numbers? Change this program appropriately so that it can run correctly on this machine.

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• Thread Synchronisation 101

  - by taspeotis

  Previously I've written some very simple multithreaded code, and I've always been aware that at any time there could be a context switch right in the middle of what I'm doing, so I've always guarded access the shared variables through a CCriticalSection class that enters the critical section on construction and leaves it on destruction. I know this is fairly aggressive and I enter and leave critical sections quite frequently and sometimes egregiously (e.g. at the start of a function when I could put the CCriticalSection inside a tighter code block) but my code doesn't crash and it runs fast enough. At work my multithreaded code needs to be a tighter, only locking/synchronising at the lowest level needed. At work I was trying to debug some multithreaded code, and I came across this: EnterCriticalSection(&m_Crit4); m_bSomeVariable = true; LeaveCriticalSection(&m_Crit4); Now, m_bSomeVariable is a Win32 BOOL (not volatile), which as far as I know is defined to be an int, and on x86 reading and writing these values is a single instruction, and since context switches occur on an instruction boundary then there's no need for synchronising this operation with a critical section. I did some more research online to see whether this operation did not need synchronisation, and I came up with two scenarios it did: The CPU implements out of order execution or the second thread is running on a different core and the updated value is not written into RAM for the other core to see; and The int is not 4-byte aligned. I believe number 1 can be solved using the "volatile" keyword. In VS2005 and later the C++ compiler surrounds access to this variable using memory barriers, ensuring that the variable is always completely written/read to the main system memory before using it. Number 2 I cannot verify, I don't know why the byte alignment would make a difference. I don't know the x86 instruction set, but does mov need to be given a 4-byte aligned address? If not do you need to use a combination of instructions? That would introduce the problem. So... QUESTION 1: Does using the "volatile" keyword (implicity using memory barriers and hinting to the compiler not to optimise this code) absolve a programmer from the need to synchronise a 4-byte/8-byte on x86/x64 variable between read/write operations? QUESTION 2: Is there the explicit requirement that the variable be 4-byte/8-byte aligned? I did some more digging into our code and the variables defined in the class: class CExample { private: CRITICAL_SECTION m_Crit1; // Protects variable a CRITICAL_SECTION m_Crit2; // Protects variable b CRITICAL_SECTION m_Crit3; // Protects variable c CRITICAL_SECTION m_Crit4; // Protects variable d // ... }; Now, to me this seems excessive. I thought critical sections synchronised threads between a process, so if you've got one you can enter it and no other thread in that process can execute. There is no need for a critical section for each variable you want to protect, if you're in a critical section then nothing else can interrupt you. I think the only thing that can change the variables from outside a critical section is if the process shares a memory page with another process (can you do that?) and the other process starts to change the values. Mutexes would also help here, named mutexes are shared across processes, or only processes of the same name? QUESTION 3: Is my analysis of critical sections correct, and should this code be rewritten to use mutexes? I have had a look at other synchronisation objects (semaphores and spinlocks), are they better suited here? QUESTION 4: Where are critical sections/mutexes/semaphores/spinlocks best suited? That is, which synchronisation problem should they be applied to. Is there a vast performance penalty for choosing one over the other? And while we're on it, I read that spinlocks should not be used in a single-core multithreaded environment, only a multi-core multithreaded environment. So, QUESTION 5: Is this wrong, or if not, why is it right? Thanks in advance for any responses :)

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• How can I handle parameterized queries in Drupal?

  - by Anthony Gatlin

  We have a client who is currently using Lotus Notes/Domino as their content management system and web server. For many reasons, we are recommending they sunset their Notes/Domino implementation and transition onto a more modern platform--such as Drupal. The client has several web applications which would be a natural fit for Drupal. However, I am unsure of the best way to implement one of the web applications in Drupal. I am running into a knowledge barrier and wondered if any of you could fill in the gaps. Situation The client has a Lotus Domino application which serves as a front-end for querying a large DB2 data store and returning a result set (generally in table form) to a user via the web. The web application provides access to approximately 100 pre-defined queries--50 of which are public and 50 of which are secured. Most of the queries accept some set of user selected parameters as input. The output of the queries is typically returned to users in a list (table) format. A limited number of result sets allow drill-down through the HTML table into detail records. The query parameters often involve database queries themselves. For example, a single query may pull a list of company divisions into a drop-down. Once a division is selected, second drop-down with the departments from that division is populated--but perhaps only departments which meet some special criteria--such as those having taken a loss within a specific time frame. Most queries have 2-4 parameters with the average probably being 3. The application involves no data entry. None of the back-end data is ever modified by the web application. All access is purely based around querying data and viewing results. The queries change relatively infrequently, and the current system has been in place for approximately 10 years. There may be 10-20 query additions, modifications, or other changes in a given year. The client simply desires to change the presentation platform but absolutely does not want to re-do the 100 database queries. Once the project is implemented, the client wants their staff to take over and manage future changes. The client's staff have no background in Drupal or PHP but are somewhat willing to learn as necessary. How would you transition this into Drupal? My major knowledge void relates to how we would manage the query parameters and access the queries themselves. Here are a few specific questions but feel free to chime in on any issue related to this implementation. Would we have to build 100 forms by hand--with each form containing the parameters for a given query? If so, how would we do this? Approximately how long would it take to build/configure each of these forms? Is there a better way than manually building 100 forms? (I understand using CCK to enter data into custom content types but since we aren't adding any nodes, I am a little stuck as to how this might work.) Would it be possible for the internal staff to learn to create these query parameter forms--even if they are unfamiliar with Drupal today? Would they be required to do any PHP programming? How would we take the query parameters from a form and execute a query against DB2? Would this require a custom module? If so, would it require one module total or one module per query? (Note: There is apparently a DB2 driver available for Drupal. See http://groups.drupal.org/node/5511.) Note: I am not looking for CMS recommendations other than Drupal as Drupal nicely fits all of the client's other requirements, and I hope to help them standardize on a single platform. Any assistance you can provide would be helpful. Thank you in advance for your help!

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• Slow Jquery Animation

  - by Pyronaut

  I have this webpage : http://miloarc.pyrogenicmedia.com/ Which atm is nothing special. It has a few effects but none that break the bank. If you mouse over a tile, it should change it's opacity to give it a fade effect. This is done through the Jquery Animation, not through CSS (I do this so it can fade, instead of being a straight change). Everything looks nice when the page loads, and the fades look perfect. Infact if you drag your mouse all over the place, if gives you a "trail" almost like a snake. Anyway, My next problem is that you will see there is a box in the top left, which is going to tell you information about the tile you are hovering over. This seems to work fine. When you mouse over that information box, it switches it's position (So that you can reach the tiles that were previously hidden underneath it). From my understanding, this is all working fine, and to the letter. However, After one move of the info box (One hover). Viewing the page in Firefox turns slugish. As in, after a successful move of the info box, the fade effects become very stuttered, and it doesn't pick up events as fast meaning you can't draw a "trail" on the screen. Chrome doesn't have this issue. It seems to work fine no matter what. Safari also seems ok. Although I do notice if I move my mouse really fast, it does jump a bit but not as much as firefox. Internet explorer doesn't work at all. Seems to crash the browser... And there is an error with the rounded corner plugin im using (Not sure why...). All in all, I think whatever I'm doing inside my code must be heavily sluggish. But I don't know where it is happening. Here is the full code, but I would advise go to the link to view everything. <script type="text/javascript"> $(document).ready(function() { var WindowWidth = $(window).width(); var WindowMod = WindowWidth % 20; var WindowWidth = WindowWidth - WindowMod; var BoxDimension = WindowWidth / 20; var BoxDimensionFixed = BoxDimension - 12; var dimensions = BoxDimensionFixed + 'px'; $('.gamebutton').each(function(i) { $(this).css('width', dimensions); $(this).css('height', dimensions); }); var OuterDivHeight = BoxDimension * 10; var TopMargin = ($(window).height() - OuterDivHeight) / 2; var OuterDivWidth = BoxDimension * 20; var LeftMargin = ($(window).width() - OuterDivWidth) / 2; $('#gamePort').css('margin-top', TopMargin).css('margin-left', LeftMargin).css('margin-right', LeftMargin); $('.gamebutton img').each(function(i) { $(this).hover( function () { $(this).animate({'opacity': 0.65}); }, function () { $(this).animate({'opacity': 1}); } ); }); $('.rounded').corners(); $('.gamebutton').each(function(i) { $(this).hover(function() { $('.gameTitlePopup').html($(this).attr('title')); FadeActive(); }); }); function FadeActive() { $('.activeInfo').fadeIn('slow'); } $('#gameInfoLeft').hover(function() { $(this).removeClass('activeInfo'); $(this).fadeOut('slow', function() { $('#gameInfoRight').addClass('activeInfo'); FadeActive(); }); }); $('#gameInfoRight').hover(function() { $(this).removeClass('activeInfo'); $(this).fadeOut('slow', function() { $('#gameInfoLeft').addClass('activeInfo'); FadeActive(); }); }); }); </script> Thanks for any help :).

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• Mono-LibreOffice System.TypeLoadException

  - by Marco

  In the past I wrote a C# library to work with OpenOffice and this worked fine both in Windows than under Ubuntu with Mono. Part of this library is published here as accepted answer. In these days I discovered that Ubuntu decided to move to LibreOffice, so I tried my library with LibreOffice latest stable release. While under Windows it's working perfectly, under Linux I receive this error: Unhandled Exception: System.TypeLoadException: A type load exception has occurred. [ERROR] FATAL UNHANDLED EXCEPTION: System.TypeLoadException: A type load exception has occurred. Usually Mono tells us which library can't load, so I can install correct package and everything is OK, but in this case I really don't know what's going bad. I'm using Ubuntu oneiric and my library is compiled with Framework 4.0. Under Windows I had to write this into app.config: <?xml version="1.0"?> <configuration> <startup useLegacyV2RuntimeActivationPolicy="true"> <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0,Profile=Client"/> </startup> </configuration> because LibreOffice assemblies uses Framework 2.0 (I think). How can I find the reason of this error to solve it? Thanks UPDATE: Even compiling with Framework 2.0 problem (as expected) is the same. Problem (I think) is that Mono is not finding cli-uno-bridge package (installable on previous Ubuntu releases and now marked as superseded), but I cannot be sure. UPDATE 2: I created a test console application referencing cli-uno dlls on Windows (they are registered in GAC_32 and GAC_MSIL). CONSOLE app static void Main(string[] args) { Console.WriteLine("Starting"); string dir = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location); string doc = Path.Combine(dir, "Liberatoria siti web.docx"); using (QOpenOffice.OpenOffice oo = new QOpenOffice.OpenOffice()) { if (!oo.Init()) return; oo.Load(doc, true); oo.ExportToPdf(Path.ChangeExtension(doc, ".pdf")); } } LIBRARY: using unoidl.com.sun.star.lang; using unoidl.com.sun.star.uno; using unoidl.com.sun.star.container; using unoidl.com.sun.star.frame; using unoidl.com.sun.star.beans; using unoidl.com.sun.star.view; using unoidl.com.sun.star.document; using System.Collections.Generic; using System.IO; using System; namespace QOpenOffice { class OpenOffice : IDisposable { private XComponentContext context; private XMultiServiceFactory service; private XComponentLoader component; private XComponent doc; public bool Init() { Console.WriteLine("Entering Init()"); try { context = uno.util.Bootstrap.bootstrap(); service = (XMultiServiceFactory)context.getServiceManager(); component = (XComponentLoader)service.createInstance("com.sun.star.frame.Desktop"); XNameContainer filters = (XNameContainer)service.createInstance("com.sun.star.document.FilterFactory"); return true; } catch (System.Exception ex) { Console.WriteLine(ex.Message); if (ex.InnerException != null) Console.WriteLine(ex.InnerException.Message); return false; } } } } but I'm not able to see "Starting" !!! If I comment using(...) on application, I see line on console... so I think it's something wrong in DLL. There I'm not able to see "Entering Init()" message on Init(). Behaviour is the same when LibreOffice is not installed and when it is !!! try..catch block is not executed...

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• Variable mysteriously changing value

  - by Eitan

  I am making a simple tcp/ip chat program for practicing threads and tcp/ip. I was using asynchronous methods but had a problem with concurrency so I went to threads and blocking methods (not asynchronous). I have two private variables defined in the class, not static: string amessage = string.Empty; int MessageLength; and a Thread private Thread BeginRead; Ok so I call a function called Listen ONCE when the client starts: public virtual void Listen(int byteLength) { var state = new StateObject {Buffer = new byte[byteLength]}; BeginRead = new Thread(ReadThread); BeginRead.Start(state); } and finally the function to receive commands and process them, I'm going to shorten it because it is really long: private void ReadThread(object objectState) { var state = (StateObject)objectState; int byteLength = state.Buffer.Length; while (true) { var buffer = new byte[byteLength]; int len = MySocket.Receive(buffer); if (len <= 0) return; string content = Encoding.ASCII.GetString(buffer, 0, len); amessage += cleanMessage.Substring(0, MessageLength); if (OnRead != null) { var e = new CommandEventArgs(amessage); OnRead(this, e); } } } Now, as I understand it only one thread at a time will enter BeginRead, I call Receive, it blocks until I get data, and then I process it. The problem: the variable amessage will change it's value between statements that do not touch or alter the variable at all, for example at the bottom of the function at: if (OnRead != null) "amessage" will be equal to 'asdf' and at if (OnRead != null) "amessage" will be equal to qwert. As I understand it this is indicative of another thread changing the value/running asynchronously. I only spawn one thread to do the receiving and the Receive function is blocking, how could there be two threads in this function and if there is only one thread how does amessage's value change between statements that don't affect it's value. As a side note sorry for spamming the site with these questions but I'm just getting a hang of this threading story and it's making me want to sip cyanide. Thanks in advance. EDIT: Here is my code that calls the Listen Method in the client: public void ConnectClient(string ip,int port) { client.Connect(ip,port); client.Listen(5); } and in the server: private void Accept(IAsyncResult result) { var client = new AbstractClient(MySocket.EndAccept(result)); var e = new CommandEventArgs(client, null); Clients.Add(client); client.Listen(5); if (OnClientAdded != null) { var target = (Control) OnClientAdded.Target; if (target != null && target.InvokeRequired) target.Invoke(OnClientAdded, this, e); else OnClientAdded(this, e); } client.OnRead += OnRead; MySocket.BeginAccept(new AsyncCallback(Accept), null); } All this code is in a class called AbstractClient. The client inherits the Abstract client and when the server accepts a socket it create's it's own local AbstractClient, in this case both modules access the functions above however they are different instances and I couldn't imagine threads from different instances combining especially as no variable is static.

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• JSTL c:forEach causes @ViewScoped bean to invoke @PostConstruct on every request

  - by Nitesh Panchal

  Hello, Again i see that the @PostConstruct is firing every time even though no binding attribute is used. See this code :- <?xml version='1.0' encoding='UTF-8' ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xmlns:h="http://java.sun.com/jsf/html" xmlns:ui="http://java.sun.com/jsf/facelets" xmlns:c="http://java.sun.com/jsp/jstl/core"> <h:head> <title>Facelet Title</title> </h:head> <h:body> <h:form> <c:forEach var="item" items="#{TestBean.listItems}"> <h:outputText value="#{item}"/> </c:forEach> <h:commandButton value="Click" actionListener="#{TestBean.actionListener}"/> </h:form> </h:body> </html> And this is the simplest possible bean in JSF :- package managedBeans; import java.io.Serializable; import java.util.ArrayList; import java.util.List; import javax.annotation.PostConstruct; import javax.faces.bean.ManagedBean; import javax.faces.bean.ViewScoped; @ManagedBean(name="TestBean") @ViewScoped public class TestBean implements Serializable { private List<String> listItems; public List<String> getListItems() { return listItems; } public void setListItems(List<String> listItems) { this.listItems = listItems; } public TestBean() { } @PostConstruct public void init(){ System.out.println("Post Construct fired!"); listItems = new ArrayList<String>(); listItems.add("Mango"); listItems.add("Apple"); listItems.add("Banana"); } public void actionListener(){ System.out.println("Action Listener fired!"); } } Do you see any behaviour that should cause postconstruct callback to fire each time? I think JSF 2.0 is highly unstable. If it has to fire PostConstruct each and every time what purpose does @ViewScoped serve. Why not to use @RequestScoped only? I thought i have made some mistake in my application. But when i created this simplest possible in JSF, i still get this error. Am i not understanding the scopes of JSF? or are they not testing it properly? Further, if you remove c:forEach and replace it with ui:repeat, then it works fine. Waiting for replies to confirm whether it is bug or it is intentional to stop the programmers from using jstl?

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• How to show form in front in C#

  - by corlettk

  Folks, Please does anyone know how to show a Form from an otherwise invisible application, and have it get the focus (i.e. appear on top of other windows)? I'm working in C# .NET 3.5. I suspect I've taken "completely the wrong approach"... I do not Application.Run(new TheForm ()) instead I (new TheForm()).ShowModal()... The Form is basically a modal dialogue, with a few check-boxes; a text-box, and OK and Cancel Buttons. The user ticks a checkbox and types in a description (or whatever) then presses OK, the form disappears and the process reads the user-input from the Form, Disposes it, and continues processing. This works, except when the form is show it doesn't get the focus, instead it appears behind the "host" application, until you click on it in the taskbar (or whatever). This is a most annoying behaviour, which I predict will cause many "support calls", and the existing VB6 version doesn't have this problem, so I'm going backwards in usability... and users won't accept that (and nor should they). So... I'm starting to think I need to rethink the whole shebang... I should show the form up front, as a "normal application" and attach the remainer of the processing to the OK-button-click event. It should work, But that will take time which I don't have (I'm already over time/budget)... so first I really need to try to make the current approach work... even by quick-and-dirty methods. So please does anyone know how to "force" a .NET 3.5 Form (by fair means or fowl) to get the focus? I'm thinking "magic" windows API calls (I know Twilight Zone: This only appears to be an issue at work, we're I'm using Visual Studio 2008 on Windows XP SP3... I've just failed to reproduce the problem with an SSCCE (see below) at home on Visual C# 2008 on Vista Ulimate... This works fine. Huh? WTF? Also, I'd swear that at work yesterday showed the form when I ran the EXE, but not when F5'ed (or Ctrl-F5'ed) straight from the IDE (which I just put up with)... At home the form shows fine either way. Totaly confusterpating! It may or may not be relevant, but Visual Studio crashed-and-burned this morning when the project was running in debug mode and editing the code "on the fly"... it got stuck what I presumed was an endless loop of error messages. The error message was something about "can't debug this project because it is not the current project, or something... So I just killed it off with process explorer. It started up again fine, and even offered to recover the "lost" file, an offer which I accepted. using System; using System.Windows.Forms; namespace ShowFormOnTop { static class Program { [STAThread] static void Main() { Application.EnableVisualStyles(); Application.SetCompatibleTextRenderingDefault(false); //Application.Run(new Form1()); Form1 frm = new Form1(); frm.ShowDialog(); } } } Background: I'm porting an existing VB6 implementation to .NET... It's a "plugin" for a "client" GIS application called MapInfo. The existing client "worked invisibly" and my instructions are "to keep the new version as close as possible to the old version", which works well enough (after years of patching); it's just written in an unsupported language, so we need to port it. About me: I'm pretty much a noob to C# and .NET generally, though I've got a bottoms wiping certificate, I have been a professional programmer for 10 years; So I sort of "know some stuff". Any insights would be most welcome... and Thank you all for taking the time to read this far. Consiseness isn't (apparently) my forte. Cheers. Keith.

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• c - fork() and wait()

  - by Joe

  Hi there, I need to use the fork() and wait() functions to complete an assignment. We are modelling non-deterministic behaviour and need the program to fork() if there is more than one possible transition. In order to try and work out how fork and wait work, I have just made a simple program. I think I understand now how the calls work and would be fine if the program only branched once because the parent process could use the exit status from the single child process to determine whether the child process reached the accept state or not. As you can see from the code that follows though, I want to be able to handle situations where there must be more than one child processes. My problem is that you seem to only be able to set the status using an _exit function once. So, as in my example the exit status that the parent process tests for shows that the first child process issued 0 as it's exit status, but has no information on the second child process. I tried simply not _exit()-ing on a reject, but then that child process would carry on, and in effect there would seem to be two parent processes. Sorry for the waffle, but I would be grateful if someone could tell me how my parent process could obtain the status information on more than one child process, or I would be happy for the parent process to only notice accept status's from the child processes, but in that case I would successfully need to exit from the child processes which have a reject status. My test code is as follows: #include <stdio.h> #include <unistd.h> #include <stdlib.h> #include <errno.h> #include <sys/wait.h> int main(void) { pid_t child_pid, wpid, pid; int status = 0; int i; int a[3] = {1, 2, 1}; for(i = 1; i < 3; i++) { printf("i = %d\n", i); pid = getpid(); printf("pid after i = %d\n", pid); if((child_pid = fork()) == 0) { printf("In child process\n"); pid = getpid(); printf("pid in child process is %d\n", pid); /* Is a child process */ if(a[i] < 2) { printf("Should be accept\n"); _exit(1); } else { printf("Should be reject\n"); _exit(0); } } } if(child_pid > 0) { /* Is the parent process */ pid = getpid(); printf("parent_pid = %d\n", pid); wpid = wait(&status); if(wpid != -1) { printf("Child's exit status was %d\n", status); if(status > 0) { printf("Accept\n"); } else { printf("Complete parent process\n"); if(a[0] < 2) { printf("Accept\n"); } else { printf("Reject\n"); } } } } return 0; } Many thanks Joe

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• Facebook, Yimg and google-analytics CDNs is freaking me out

  - by Millisami

  Hi, Its been a couple of weeks that some sites just keeps on hanging. e.g. Facebooks = static.ak.fbcdn.net FLicker = l.yimg.com GoogleAnalytics I've googled and found many problems like this and some answers which are outdated or just doesn't solve the problem. I did: Cookies clearing, ran cc cleaner and several other nifty methods. None solved my problem?? Only with facebook, if I enter https:// manually instead of http:// on every url on facebook, it works and when it does the redirection to http://, everytime I have to type 's' on the address bar to make it https:// It is driving me nuts coz I'm developing Facebook App and this problem in being pain in my ass. What might be the reason for these CDNs hanging behaviour?? Update: Mon Feb 8, 2010 Well when I viewed the source with firefox, this is the header part: <link type="text/css" rel="stylesheet" href="http://b.static.ak.fbcdn.net/rsrc.php/zDO0B/hash/8jpbog60.css" /> <link type="text/css" rel="stylesheet" href="http://static.ak.fbcdn.net/rsrc.php/zA96O/hash/8jqnsh63.css" /> <link type="text/css" rel="stylesheet" href="http://b.static.ak.fbcdn.net/rsrc.php/z9X8U/hash/5zy5e7ns.css" /> <link type="text/css" rel="stylesheet" href="http://b.static.ak.fbcdn.net/rsrc.php/z7XWB/hash/b881ctjq.css" /> <link type="text/css" rel="stylesheet" href="http://static.ak.fbcdn.net/rsrc.php/zEMLE/hash/6n3druoq.css" /> <link type="text/css" rel="stylesheet" href="http://b.static.ak.fbcdn.net/rsrc.php/zEEQQ/hash/3et16vbl.css" /> <link type="text/css" rel="stylesheet" href="http://b.static.ak.fbcdn.net/rsrc.php/zF0BN/hash/4ey03a8b.css" /> #<link type="text/css" rel="stylesheet" href="http://b.static.ak.fbcdn.net/rsrc.php/zD46U/hash/4ctxkmr7.css" /> <script type="text/javascript" src="http://b.static.ak.fbcdn.net/rsrc.php/z5KPU/hash/f92tjc5l.js"></script> When I clicked the each link, all links open with its contents except the last link with -# sign prefixed. So the url -#http://b.static.ak.fbcdn.net/rsrc.php/zD46U/hash/4ctxkmr7.css is not opening and this css file is not downloaded and the facebook page looks horrible and all left aligned?? Update: Tue Feb 9, 2010 Today the link with the -# sign is just keeps hanging and looping: <link type="text/css" rel="stylesheet" href="http://static.ak.fbcdn.net/rsrc.php/zEMLE/hash/6n3druoq.css" /> <link type="text/css" rel="stylesheet" href="http://b.static.ak.fbcdn.net/rsrc.php/z9X8U/hash/5zy5e7ns.css" /> <link type="text/css" rel="stylesheet" href="http://b.static.ak.fbcdn.net/rsrc.php/zF0BN/hash/4ey03a8b.css" /> <link type="text/css" rel="stylesheet" href="http://static.ak.fbcdn.net/rsrc.php/z1580/hash/4l5utauj.css" /> #<link type="text/css" rel="stylesheet" href="http://b.static.ak.fbcdn.net/rsrc.php/z4851/hash/532htj7z.css" /> <link type="text/css" rel="stylesheet" href="http://static.ak.fbcdn.net/rsrc.php/z1GEW/hash/dh01t0zv.css" /> <link type="text/css" rel="stylesheet" href="http://static.ak.fbcdn.net/rsrc.php/z80UK/hash/3a6o59ih.css" /> <link type="text/css" rel="stylesheet" href="http://b.static.ak.fbcdn.net/rsrc.php/zD46U/hash/4ctxkmr7.css" /> <script type="text/javascript" src="http://b.static.ak.fbcdn.net/rsrc.php/z5KPU/hash/f92tjc5l.js"></script> Why that url http://b.static.ak.fbcdn.net acting weird? Has something Akamai got to do with this?

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• JAXB: Unmarshalling does not always populate certain classes?

  - by user278458

  Hello, I have a JAXB class generation problem I was hoping to get some help with. Here's the part of the XML that is the source of my problem... Code: <xs:complexType name="IDType"> <xs:choice minOccurs="0" maxOccurs="2"> <xs:element name="DriversLicense" minOccurs="0" maxOccurs="1" type="an..35" /> <xs:element name="SSN" minOccurs="0" maxOccurs="1" type="an..35" /> <xs:element name="CompanyID" minOccurs="0" maxOccurs="1" type="an..35" /> </xs:choice> </xs:complexType> <xs:simpleType name="an..35"> <xs:restriction base="an"> <xs:maxLength value="35" /> </xs:restriction> </xs:simpleType> <xs:simpleType name="an"> <xs:restriction base="xs:string"> <xs:pattern value="[ !-~]*" /> </xs:restriction> </xs:simpleType> ...now this will generate JAXBElement types due the the "choice" with a "maxOccurs 1" . I want to avoid those, so I did that by modifying the code to use a "Wrapper" element and move the maxOccurs up to a sequence tag as follows... Code: <xs:complexType name="IDType"> <xs:sequence maxOccurs="2"> <xs:element name=Wrapper> <xs:complexType> <xs:choice> <xs:element name="DriversLicense" minOccurs="0" maxOccurs="1" type="an..35" /> <xs:element name="SSN" minOccurs="0" maxOccurs="1" type="an..35" /> <xs:element name="CompanyID" minOccurs="0" maxOccurs="1" type="an..35" /> </xs:choice> </xs:complexType> </xs:element> </xs:sequence> </xs:complexType> <xs:simpleType name="an..35"> <xs:restriction base="an"> <xs:maxLength value="35" /> </xs:restriction> </xs:simpleType> <xs:simpleType name="an"> <xs:restriction base="xs:string"> <xs:pattern value="[ !-~]*" /> </xs:restriction> </xs:simpleType> For class generating, looks like it works great - the JAXB element is replaced with a list of wrappers as String (i.e. List ) and compiles fine. However, when I unmarshall the actual XML data into the generated classes the data in the wrapper class is not populated - yet JAXB does not throw an exception. My question is: Do I need to change the schema a different way to make this work? Or is there something I can add/change/delete to the generated code or annotations? Appreciate any help you can offer! Thanks.

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• c - dereferencing issue

  - by Joe

  Hi, I have simplified an issue that I've been having trying to isolate the problem, but it is not helping. I have a 2 dimensional char array to represent memory. I want to pass a reference to that simulation of memory to a function. In the function to test the contents of the memory I just want to iterate through the memory and print out the contents on each row. The program prints out the first row and then I get seg fault. My program is as follows: #include <stdio.h> #include <stdlib.h> #include <ctype.h> #include <string.h> void test_memory(char*** memory_ref) { int i; for(i = 0; i < 3; i++) { printf("%s\n", *memory_ref[i]); } } int main() { char** memory; int i; memory = calloc(sizeof(char*), 20); for(i = 0; i < 20; i++) { memory[i] = calloc(sizeof(char), 33); } memory[0] = "Mem 0"; memory[1] = "Mem 1"; memory[2] = "Mem 2"; printf("memory[1] = %s\n", memory[1]); test_memory(&memory); return 0; } This gives me the output: memory[1] = Mem 1 Mem 0 Segmentation fault If I change the program and create a local version of the memory in the function by dereferencing the memory_ref, then I get the right output: So: #include <stdio.h> #include <stdlib.h> #include <ctype.h> #include <string.h> void test_memory(char*** memory_ref) { char** memory = *memory_ref; int i; for(i = 0; i < 3; i++) { printf("%s\n", memory[i]); } } int main() { char** memory; int i; memory = calloc(sizeof(char*), 20); for(i = 0; i < 20; i++) { memory[i] = calloc(sizeof(char), 33); } memory[0] = "Mem 0"; memory[1] = "Mem 1"; memory[2] = "Mem 2"; printf("memory[1] = %s\n", memory[1]); test_memory(&memory); return 0; } gives me the following output: memory[1] = Mem 1 Mem 0 Mem 1 Mem 2 which is what I want, but making a local version of the memory is useless because I need to be able to change the values of the original memory from the function which I can only do by dereferencing the pointer to the original 2d char array. I don't understand why I should get a seg fault on the second time round, and I'd be grateful for any advice. Many thanks Joe

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• Why isn't this javascript with else if working?

  - by Uni

  I'm sorry I can't be any more specific - I have no idea where the problem is. I'm a total beginner, and I've added everything I know to add to the coding, but nothing happens when I push the button. I don't know at this point if it's an error in the coding, or a syntax error that makes it not work. Basically I am trying to get this function "Rip It" to go through the list of Dewey decimal numbers, change some of them, and return the new number and a message saying it's been changed. There is also one labeled "no number" that has to return an error (not necessarily an alert box, a message in the same space is okay.) I am a total beginner and not particularly good at this stuff, so please be gentle! Many thanks! <!DOCTYPE html> <html> <head> <script type="text/javascript"> function RipIt() { for (var i = l; i <=10 i=i+l) { var dewey=document.getElementById(i); dewey=parseFloat(dewey); if (dewey >= 100 && 200 >= dewey) { document.getElementById('dewey'+ 100) } else if (dewey >= 400 && 500 >= dewey) { document.getElementById('dewey'+ 200) } else if (dewey >= 850 && 900 >= dewey) { document.getElementById('dewey'-100) } else if (dewey >= 600 && 650 >= dewey) { document.getElementById('dewey'+17) } } } </script> </head> <body> <h4>Records to Change</h4> <ul id="myList"> <li id ="1">101.33</li> <li id = "2">600.01</li> <li id = "3">001.11</li> <li id = "4">050.02</li> <li id = "5">199.52</li> <li id = "6">400.27</li> <li id = "7">401.73</li> <li id = "8">404.98</li> <li id = "9">no number</li> <li id = "10">850.68</li> <li id = "11">853.88</li> <li id = "12">407.8</li> <li id = "13">878.22</li> <li id = "14">175.93</li> <li id = "15">175.9</li> <li id = "16">176.11</li> <li id = "17">190.97</li> <li id = "18">90.01</li> <li id = "19">191.001</li> <li id = "20">600.95</li> <li id = "21">602.81</li> <li id = "22">604.14</li> <li id = "23">701.31</li> <li id = "24">606.44</li> <li id = "25">141.77</li> </ul> <b> </b> <input type="button" value="Click To Run" onclick="RipIt()"> <!-- <input type="button" value="Click Here" onClick="showAlert();"> --> </body> </html>

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• which control in vs08 aspx c# will be able to take html tags as input and display it formatted accor

  - by user287745

  i asked a few questions regarding this and got answers that indicate i will have to make an costum build editor using ,markdown, .... to achieve something like stackoverflow.com/questions/ask page. there is time limitation and the requirements are that much, i have to achieve 1) allow users to using html tags when giving input 2) save that complete input to sql db 3) display the data in db withing a contol which renders the formatting as the tags specify. i am aware label and literal controls support html tags, the problem is how to allow the user to input the textbox does not seem the support html tags? thank you Need help in implementing the affect of the WRITE A NEW POST On stackoverflow.com <%--The editor--% <asp:UpdatePanel ID="UpdatePanel7" runat="server"> <ContentTemplate> <asp:Label ID="Label4" runat="server" Text="Label"></asp:Label> <div id="textchanging" onkeyup="textoftextbox('TextBox3'); return false;"> <asp:TextBox ID="TextBox3" runat="server" CausesValidation="True" ></asp:TextBox> </div> <%-- OnTextChanged="textoftextbox('TextBox3'); return false;" gives too man literals error. --%> <asp:Button ID="Button6" runat="server" Text="Post The Comment, The New, Write on Wall" onclick="Button6_Click" /> <asp:Label ID="Label2" runat="server" Text="Label"></asp:Label> <asp:TextBox ID="TextBox4" runat="server" CausesValidation="True"></asp:TextBox> <asp:Literal ID="Literal2" runat="server" Text="this must change" here comes the div <div id="displayingarea" runat="server">This area will change</div> </ContentTemplate> </asp:UpdatePanel> <%--The editor ends--%> protected void Button6_Click(object sender, EventArgs e) { Label3.Text = displayingarea.InnerHtml; } As you see, I have implemented the effect of typing text in textbox which appears as a reflection in the div WITH FULLY FORMATTED TEXT ACCORDIG TO THE HTML TAGS USED The textbox does not allow html! Well the text box doesnot have too, script just extracts what is typed, within letting the server know. The html of the div tag also changes as typed in textbox. Now, There is a “post” button within an update plane a avoid full post back of page What I needis when the button is clicked on the value withing the div tag “innerhtml” is passed on to the label. Yes I know the chnages are only made on the client side, So when the button click event occurs the server is not aware of the new data within the div tag, Therefore the server assign the original html withing the div to the lab. Need help to overcome this, How is it that what we enter text in the textbox press the button with coding like label1.text=textbox1.text; and it works even in update panel, but the aabove code for extracting innerhtml typed at users end similar to yping in textbox does not work?

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• How to design a C / C++ library to be usable in many client languages?

  - by Brian Schimmel

  I'm planning to code a library that should be usable by a large number of people in on a wide spectrum of platforms. What do I have to consider to design it right? To make this questions more specific, there are four "subquestions" at the end. Choice of language Considering all the known requirements and details, I concluded that a library written in C or C++ was the way to go. I think the primary usage of my library will be in programs written in C, C++ and Java SE, but I can also think of reasons to use it from Java ME, PHP, .NET, Objective C, Python, Ruby, bash scrips, etc... Maybe I cannot target all of them, but if it's possible, I'll do it. Requirements It would be to much to describe the full purpose of my library here, but there are some aspects that might be important to this question: The library itself will start out small, but definitely will grow to enormous complexity, so it is not an option to maintain several versions in parallel. Most of the complexity will be hidden inside the library, though The library will construct an object graph that is used heavily inside. Some clients of the library will only be interested in specific attributes of specific objects, while other clients must traverse the object graph in some way Clients may change the objects, and the library must be notified thereof The library may change the objects, and the client must be notified thereof, if it already has a handle to that object The library must be multi-threaded, because it will maintain network connections to several other hosts While some requests to the library may be handled synchronously, many of them will take too long and must be processed in the background, and notify the client on success (or failure) Of course, answers are welcome no matter if they address my specific requirements, or if they answer the question in a general way that matters to a wider audience! My assumptions, so far So here are some of my assumptions and conclusions, which I gathered in the past months: Internally I can use whatever I want, e.g. C++ with operator overloading, multiple inheritance, template meta programming... as long as there is a portable compiler which handles it (think of gcc / g++) But my interface has to be a clean C interface that does not involve name mangling Also, I think my interface should only consist of functions, with basic/primitive data types (and maybe pointers) passed as parameters and return values If I use pointers, I think I should only use them to pass them back to the library, not to operate directly on the referenced memory For usage in a C++ application, I might also offer an object oriented interface (Which is also prone to name mangling, so the App must either use the same compiler, or include the library in source form) Is this also true for usage in C# ? For usage in Java SE / Java EE, the Java native interface (JNI) applies. I have some basic knowledge about it, but I should definitely double check it. Not all client languages handle multithreading well, so there should be a single thread talking to the client For usage on Java ME, there is no such thing as JNI, but I might go with Nested VM For usage in Bash scripts, there must be an executable with a command line interface For the other client languages, I have no idea For most client languages, it would be nice to have kind of an adapter interface written in that language. I think there are tools to automatically generate this for Java and some others For object oriented languages, it might be possible to create an object oriented adapter which hides the fact that the interface to the library is function based - but I don't know if its worth the effort Possible subquestions is this possible with manageable effort, or is it just too much portability? are there any good books / websites about this kind of design criteria? are any of my assumptions wrong? which open source libraries are worth studying to learn from their design / interface / souce? meta: This question is rather long, do you see any way to split it into several smaller ones? (If you reply to this, do it as a comment, not as an answer)

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• How can I get SQL Server transactions to use record-level locks?

  - by Joe White

  We have an application that was originally written as a desktop app, lo these many years ago. It starts a transaction whenever you open an edit screen, and commits if you click OK, or rolls back if you click Cancel. This worked okay for a desktop app, but now we're trying to move to ADO.NET and SQL Server, and the long-running transactions are problematic. I found that we'll have a problem when multiple users are all trying to edit (different subsets of) the same table at the same time. In our old database, each user's transaction would acquire record-level locks to every record they modified during their transaction; since different users were editing different records, everyone gets their own locks and everything works. But in SQL Server, as soon as one user edits a record inside a transaction, SQL Server appears to get a lock on the entire table. When a second user tries to edit a different record in the same table, the second user's app simply locks up, because the SqlConnection blocks until the first user either commits or rolls back. I'm aware that long-running transactions are bad, and I know that the best solution would be to change these screens so that they no longer keep transactions open for a long time. But since that would mean some invasive and risky changes, I also want to research whether there's a way to get this code up and running as-is, just so I know what my options are. How can I get two different users' transactions in SQL Server to lock individual records instead of the entire table? Here's a quick-and-dirty console app that illustrates the issue. I've created a database called "test1", with one table called "Values" that just has ID (int) and Value (nvarchar) columns. If you run the app, it asks for an ID to modify, starts a transaction, modifies that record, and then leaves the transaction open until you press ENTER. I want to be able to start the program and tell it to update ID 1; let it get its transaction and modify the record; start a second copy of the program and tell it to update ID 2; have it able to update (and commit) while the first app's transaction is still open. Currently it freezes at step 4, until I go back to the first copy of the app and close it or press ENTER so it commits. The call to command.ExecuteNonQuery blocks until the first connection is closed. public static void Main() { Console.Write("ID to update: "); var id = int.Parse(Console.ReadLine()); Console.WriteLine("Starting transaction"); using (var scope = new TransactionScope()) using (var connection = new SqlConnection(@"Data Source=localhost\sqlexpress;Initial Catalog=test1;Integrated Security=True")) { connection.Open(); var command = connection.CreateCommand(); command.CommandText = "UPDATE [Values] SET Value = 'Value' WHERE ID = " + id; Console.WriteLine("Updating record"); command.ExecuteNonQuery(); Console.Write("Press ENTER to end transaction: "); Console.ReadLine(); scope.Complete(); } } Here are some things I've already tried, with no change in behavior: Changing the transaction isolation level to "read uncommitted" Specifying a "WITH (ROWLOCK)" on the UPDATE statement

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• One letter game problem?

  - by Alex K

  Recently at a job interview I was given the following problem: Write a script capable of running on the command line as python It should take in two words on the command line (or optionally if you'd prefer it can query the user to supply the two words via the console). Given those two words: a. Ensure they are of equal length b. Ensure they are both words present in the dictionary of valid words in the English language that you downloaded. If so compute whether you can reach the second word from the first by a series of steps as follows a. You can change one letter at a time b. Each time you change a letter the resulting word must also exist in the dictionary c. You cannot add or remove letters If the two words are reachable, the script should print out the path which leads as a single, shortest path from one word to the other. You can /usr/share/dict/words for your dictionary of words. My solution consisted of using breadth first search to find a shortest path between two words. But apparently that wasn't good enough to get the job :( Would you guys know what I could have done wrong? Thank you so much. import collections import functools import re def time_func(func): import time def wrapper(*args, **kwargs): start = time.time() res = func(*args, **kwargs) timed = time.time() - start setattr(wrapper, 'time_taken', timed) return res functools.update_wrapper(wrapper, func) return wrapper class OneLetterGame: def __init__(self, dict_path): self.dict_path = dict_path self.words = set() def run(self, start_word, end_word): '''Runs the one letter game with the given start and end words. ''' assert len(start_word) == len(end_word), \ 'Start word and end word must of the same length.' self.read_dict(len(start_word)) path = self.shortest_path(start_word, end_word) if not path: print 'There is no path between %s and %s (took %.2f sec.)' % ( start_word, end_word, find_shortest_path.time_taken) else: print 'The shortest path (found in %.2f sec.) is:\n=> %s' % ( self.shortest_path.time_taken, ' -- '.join(path)) def _bfs(self, start): '''Implementation of breadth first search as a generator. The portion of the graph to explore is given on demand using get_neighboors. Care was taken so that a vertex / node is explored only once. ''' queue = collections.deque([(None, start)]) inqueue = set([start]) while queue: parent, node = queue.popleft() yield parent, node new = set(self.get_neighbours(node)) - inqueue inqueue = inqueue | new queue.extend([(node, child) for child in new]) @time_func def shortest_path(self, start, end): '''Returns the shortest path from start to end using bfs. ''' assert start in self.words, 'Start word not in dictionnary.' assert end in self.words, 'End word not in dictionnary.' paths = {None: []} for parent, child in self._bfs(start): paths[child] = paths[parent] + [child] if child == end: return paths[child] return None def get_neighbours(self, word): '''Gets every word one letter away from the a given word. We do not keep these words in memory because bfs accesses a given vertex only once. ''' neighbours = [] p_word = ['^' + word[0:i] + '\w' + word[i+1:] + '$' for i, w in enumerate(word)] p_word = '|'.join(p_word) for w in self.words: if w != word and re.match(p_word, w, re.I|re.U): neighbours += [w] return neighbours def read_dict(self, size): '''Loads every word of a specific size from the dictionnary into memory. ''' for l in open(self.dict_path): l = l.decode('latin-1').strip().lower() if len(l) == size: self.words.add(l) if __name__ == '__main__': import sys if len(sys.argv) not in [3, 4]: print 'Usage: python one_letter_game.py start_word end_word' else: g = OneLetterGame(dict_path = '/usr/share/dict/words') try: g.run(*sys.argv[1:]) except AssertionError, e: print e

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• Problem on getting the vendor id and product id of a usb device

  - by new

  Hi... my application comes and prints this "\?\usb#vid_04f2&pid_0111#5&1ba5a77f&0&2#{a5dcbf1 0-6530-11d2-901f-00c04fb951ed}" again it goes to while loop .... here it gets breaked in the else statement... Qt Code: if (GetLastError() == ERROR_INSUFFICIENT_BUFFER) { // Change the buffer size. if (buffer) LocalFree(buffer); buffer = (LPTSTR)LocalAlloc(LPTR,buffersize); } else { qDebug ()<<"Here it quits the application"; // Insert error handling here. break; } Any ideas in this.... full source code comes here static GUID GUID_DEVINTERFACE_USB_DEVICE = { 0xA5DCBF10L, 0x6530, 0x11D2, { 0x90, 0x1F, 0x00, 0xC0, 0x4F, 0xB9, 0x51, 0xED } }; HANDLE hInfo = SetupDiGetClassDevs(&GUID_DEVINTERFACE_USB_DEVICE,NULL,NULL, DIGCF_PRESENT | DIGCF_INTERFACEDEVICE); if ( hInfo == INVALID_HANDLE_VALUE ) { qDebug ()<<"invalid"; } else { qDebug ()<<"valid handle"; SP_DEVINFO_DATA DeviceInfoData; DeviceInfoData.cbSize = sizeof(SP_DEVINFO_DATA); SP_INTERFACE_DEVICE_DATA Interface_Info; Interface_Info.cbSize = sizeof(Interface_Info); BYTE Buf[1024]; DWORD i; DWORD InterfaceNumber= 0; PSP_DEVICE_INTERFACE_DETAIL_DATA pspdidd = (PSP_DEVICE_INTERFACE_DETAIL_DATA) Buf; for (i=0;SetupDiEnumDeviceInfo(hInfo,i,&DeviceInfoData);i++) { DWORD DataT; LPTSTR buffer = NULL; DWORD buffersize = 0; while (!SetupDiGetDeviceRegistryProperty( hInfo, &DeviceInfoData,SPDRP_DEVICEDESC, &DataT,(PBYTE)buffer,buffersize, &buffersize)) { if (GetLastError() == ERROR_INSUFFICIENT_BUFFER) { // Change the buffer size. if (buffer) LocalFree(buffer); buffer = (LPTSTR)LocalAlloc(LPTR,buffersize); } else { // Insert error handling here. break; } qDebug ()<<(TEXT("Device Number %i is: %s\n"),i, buffer); if (buffer) LocalFree(buffer); if ( GetLastError() != NO_ERROR && GetLastError() != ERROR_NO_MORE_ITEMS ) { // Insert error handling here. qDebug ()<<"return false"; } InterfaceNumber = 0; // this just returns the first one, you can iterate on this if (SetupDiEnumDeviceInterfaces(hInfo, NULL, &GUID_DEVINTERFACE_USB_DEVICE, InterfaceNumber, &Interface_Info)) { printf("Got interface"); DWORD needed; pspdidd->cbSize = sizeof(*pspdidd); SP_DEVICE_INTERFACE_DETAIL_DATA *pDetData = NULL; DWORD dwDetDataSize = sizeof (SP_DEVICE_INTERFACE_DETAIL_DATA) + 256; pDetData = (SP_DEVICE_INTERFACE_DETAIL_DATA*) malloc (dwDetDataSize); pDetData->cbSize = sizeof (SP_DEVICE_INTERFACE_DETAIL_DATA); SetupDiGetDeviceInterfaceDetail(hInfo,&Interface_Info, pDetData,dwDetDataSize, NULL,&DeviceInfoData); qDebug ()<<pDetData->DevicePath; qDebug ()<<QString::fromWCharArray(pDetData->DevicePath); free(pDetData); } else { printf("\nNo interface"); //ErrorExit((LPTSTR) "SetupDiEnumDeviceInterfaces"); if ( GetLastError() == ERROR_NO_MORE_ITEMS) printf(", since there are no more items found."); else printf(", unknown reason."); } // Cleanup SetupDiDestroyDeviceInfoList(hInfo); } } }

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• Link Error : xxx is already defined in *****.LIB :: What exactly is wrong?

  - by claws

  Problem: I'm trying to use a library named DCMTK which used some other external libraries ( zlib, libtiff, libpng, libxml2, libiconv ). I've downloaded these external libraries (*.LIB & *.h files ) from the same website. Now, when I compile the DCMTK library I'm getting link errors (793 errors) like this: Error 2 error LNK2005: __encode_pointer already defined in MSVCRTD.lib(MSVCR90D.dll) LIBCMTD.lib dcmmkdir Error 3 error LNK2005: __decode_pointer already defined in MSVCRTD.lib(MSVCR90D.dll) LIBCMTD.lib dcmmkdir Error 4 error LNK2005: __CrtSetCheckCount already defined in MSVCRTD.lib(MSVCR90D.dll) LIBCMTD.lib dcmmkdir Error 5 error LNK2005: __invoke_watson already defined in MSVCRTD.lib(MSVCR90D.dll) LIBCMTD.lib dcmmkdir Error 6 error LNK2005: __errno already defined in MSVCRTD.lib(MSVCR90D.dll) LIBCMTD.lib dcmmkdir Error 7 error LNK2005: __configthreadlocale already defined in MSVCRTD.lib(MSVCR90D.dll) LIBCMTD.lib dcmmkdir Error 8 error LNK2005: _exit already defined in MSVCRTD.lib(MSVCR90D.dll) LIBCMTD.lib dcmmkdir Documentation: This seems to be a popular error for this library so, they do have a FAQ entry addressing this issue which ( http://forum.dcmtk.org/viewtopic.php?t=35 ) says: The problem is that the linker tries to combine different, incompatible versions of the Visual C++ runtime library into a single binary. This happens when not all parts of your project and the libraries you link against are generated with the same code generation options in Visual C++. Do not use the /NODEFAULTLIB workaround, because strange software crashes may follow. Fix the problem! DCMTK is by default compiled with the "Multithreaded" or "Multithreaded Debug" code generation option (the latter for Debug mode). Either change the project settings of all of your code to use these code generation options, or change the code generation for all DCMTK modules and re-compile. MFC users beware: DCMTK should be compiled with "Multithreaded DLL" or "Multithreaded DLL Debug" settings if you want to link the libraries into an MFC application. Solution to same problem for others: http://stackoverflow.com/questions/2259697/vscopengl-huge-amount-of-linker-issues-with-release-build-only says: It seems that your release build is trying to link to something that was built debug. You probably have a broken dependency in your build, (or you missed rebuilding something to release by hand if your project is normally built in pieces). More technically, you seem to be linking projects built with different C Run Time library settings, one with "Multi-Threaded", another one with "Multi-Threaded Debug". Adjust the settings for all the projects to use the very same flavour of the library and the issue should go away Questions: Till now I used to think that Name mangling is the only problem that may cause linking failures if its not been standardized. Just now I knew there are other things also which can cause same effect. Whats up with the "Debug Mode" (Multi-Threaded Debug) and "Release Mode" (Multi-Threaded)? What exactly is happening under the hood? Why exactly this thing is causing linking error? I wonder if there is something called "Single-Threaded Debug" and "Single-Threaded" which again causes the same thing. Documentation talks something about "Code Generation Options". What Code Generation Options? WTH are they? Documentation specifically warns us not to use /NODEFAULTLIB workaround. (example /NODEFAULTLIB :msvcrt ). Why? How would I cause troubles? what exactly is it? Please explain the last point in the documentation for MFC users. Because I'm going to use MFC later in this project. Explain Why should we do it? What troubles would it cause if I don't. Anything more you'd like to mention? I mean regarding similar errors. I'm very interested in Linker & its problems. So, if there are any similar things you can mentions them or some keywords atleast.

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• Better, simpler example of 'semantic conflict'?

  - by rhubbarb

  I like to distinguish three different types of conflict from a version control system (VCS): textual syntactic semantic A textual conflict is one that is detected by the merge or update process. This is flagged by the system. A commit of the result is not permitted by the VCS until the conflict is resolved. A syntactic conflict is not flagged by the VCS, but the result will not compile. Therefore this should also be picked up by even a slightly careful programmer. (A simple example might be a variable rename by Left and some added lines using that variable by Right. The merge will probably have an unresolved symbol. Alternatively, this might introduce a semantic conflict by variable hiding.) Finally, a semantic conflict is not flagged by the VCS, the result compiles, but the code may have problems running. In mild cases, incorrect results are produced. In severe cases, a crash could be introduced. Even these should be detected before commit by a very careful programmer, through either code review or unit testing. My example of a semantic conflict uses SVN (Subversion) and C++, but those choices are not really relevant to the essence of the question. The base code is: int i = 0; int odds = 0; while (i < 10) { if ((i & 1) != 0) { odds *= 10; odds += i; } // next ++ i; } assert (odds == 13579) The Left (L) and Right (R) changes are as follows. Left's 'optimisation' (changing the values the loop variable takes): int i = 1; // L int odds = 0; while (i < 10) { if ((i & 1) != 0) { odds *= 10; odds += i; } // next i += 2; // L } assert (odds == 13579) Right's 'optimisation' (changing how the loop variable is used): int i = 0; int odds = 0; while (i < 5) // R { odds *= 10; odds += 2 * i + 1; // R // next ++ i; } assert (odds == 13579) This is the result of a merge or update, and is not detected by SVN (which is correct behaviour for the VCS). int i = 1; // L int odds = 0; while (i < 5) // R { odds *= 10; odds += 2 * i + 1; // R // next i += 2; // L } assert (odds == 13579) The assert fails because odds is 37. So my question is as follows. Is there a simpler example than this? Is there a simple example where the compiled executable has a new crash? As a secondary question, are there cases of this that you have encountered in real code? Again, simple examples are especially welcome.

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• ScriptManager emits ScriptReferences after ClientScriptIncludes. Why?

  - by Chris F

  I have an application that uses a lot of javascript in a lot of different .js files. Each page can have any number and combination of different controls and each control can use a different set of js files. Instead of including all possible js files as <script src="xxx.js"> in the head of my master page, I thought I would reduce the amount of included files by getting each control to call ScriptManager.Scripts.Add(new ScriptReference("xxx.js")) - thus only the scripts that are actually needed by the page will be included. Well that bit works fine. But...the controls also use ScriptManager.RegisterClientScriptBlock fairly extensively too. (There are scenarios where the controls are inside update panels). I was disappointed to see that the ScriptManager emits the client script includes before the ScriptReferences. For example - see the test file and output at the end (this results in a JS error because $ is not defined). Am I being dumb or is this to be expected? I would have thought that a sensible thing for the ScriptManger to do would be to emit the ScriptReferences first and then the other stuff. Short of rolling my own ScriptManager like object to manage static JS file references, does anyone have any suggestions as to get the behaviour that I want from ScriptManager?? Thanks in advance. Example File <%@ Page Language="C#" AutoEventWireup="true" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" > <head runat="server"> <script runat="server"> protected void Page_Load(object sender, EventArgs e) { ScriptManager.RegisterClientScriptBlock(Page, Page.GetType(), "Test", "$(function() {alert('hello');});", true); } </script> </head> <body> <form id="form1" runat="server"> <asp:ScriptManager runat="server" > <Scripts> <asp:ScriptReference Path="~/jquery/jquery.js" /> </Scripts> </asp:ScriptManager> </form> </body> </html> Output <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" > ... boring stuff removed .... <script src="/js/WebResource.axd?d=-nOHbla bla " type="text/javascript"></script> <script type="text/javascript"> //<![CDATA[ $(function() {alert('hello');});//]]> </script> ... boring stuff removed .... <script src="/js/ScriptResource.axd?d=qgCbla bla bla" type="text/javascript"></script> <script src="jquery/jquery.js" type="text/javascript"></script> ... boring stuff removed .... </form> </body> </html>

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• What is the fastest way to Initialize a multi-dimensional array to non-default values in .NET?

  - by AMissico

  How do I initialize a multi-dimensional array of a primitive type as fast as possible? I am stuck with using multi-dimensional arrays. My problem is performance. The following routine initializes a 100x100 array in approx. 500 ticks. Removing the int.MaxValue initialization results in approx. 180 ticks just for the looping. Approximately 100 ticks to create the array without looping and without initializing to int.MaxValue. Routines similiar to this are called a few hundred-thousand to several million times during a "run". The array size will not change during a run and arrays are created one-at-a-time, used, then discarded, and a new array created. A "run" which may last from one minute (using 10x10 arrays) to forty-five minutes (100x100). The application creates arrays of int, bool, and struct. There can be multiple "runs" executing at same time, but are not because performance degrades terribly. I am using 100x100 as a base-line. I am open to suggestions on how to optimize this non-default initialization of an array. One idea I had is to use a smaller primitive type when available. For instance, using byte instead of int, saves 100 ticks. I would be happy with this, but I am hoping that I don't have to change the primitive data type. public int[,] CreateArray(Size size) { int[,] array = new int[size.Width, size.Height]; for (int x = 0; x < size.Width; x++) { for (int y = 0; y < size.Height; y++) { array[x, y] = int.MaxValue; } } return array; } Down to 450 ticks with the following: public int[,] CreateArray1(Size size) { int iX = size.Width; int iY = size.Height; int[,] array = new int[iX, iY]; for (int x = 0; x < iX; x++) { for (int y = 0; y < iY; y++) { array[x, y] = int.MaxValue; } } return array; } Down to approximately 165 ticks after a one-time initialization of 2800 ticks. (See my answer below.) If I can get stackalloc to work with multi-dimensional arrays, I should be able to get the same performance without having to intialize the private static array. private static bool _arrayInitialized5; private static int[,] _array5; public static int[,] CreateArray5(Size size) { if (!_arrayInitialized5) { int iX = size.Width; int iY = size.Height; _array5 = new int[iX, iY]; for (int x = 0; x < iX; x++) { for (int y = 0; y < iY; y++) { _array5[x, y] = int.MaxValue; } } _arrayInitialized5 = true; } return (int[,])_array5.Clone(); } Down to approximately 165 ticks without using the "clone technique" above. (See my answer below.) I am sure I can get the ticks lower, if I can just figure out the return of CreateArray9. public unsafe static int[,] CreateArray8(Size size) { int iX = size.Width; int iY = size.Height; int[,] array = new int[iX, iY]; fixed (int* pfixed = array) { int count = array.Length; for (int* p = pfixed; count-- > 0; p++) *p = int.MaxValue; } return array; }

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• Is there a way to delay compilation of a stored procedure's execution plan?

  - by Ian Henry

  (At first glance this may look like a duplicate of http://stackoverflow.com/questions/421275 or http://stackoverflow.com/questions/414336, but my actual question is a bit different) Alright, this one's had me stumped for a few hours. My example here is ridiculously abstracted, so I doubt it will be possible to recreate locally, but it provides context for my question (Also, I'm running SQL Server 2005). I have a stored procedure with basically two steps, constructing a temp table, populating it with very few rows, and then querying a very large table joining against that temp table. It has multiple parameters, but the most relevant is a datetime "@MinDate." Essentially: create table #smallTable (ID int) insert into #smallTable select (a very small number of rows from some other table) select * from aGiantTable inner join #smallTable on #smallTable.ID = aGiantTable.ID inner join anotherTable on anotherTable.GiantID = aGiantTable.ID where aGiantTable.SomeDateField > @MinDate If I just execute this as a normal query, by declaring @MinDate as a local variable and running that, it produces an optimal execution plan that executes very quickly (first joins on #smallTable and then only considers a very small subset of rows from aGiantTable while doing other operations). It seems to realize that #smallTable is tiny, so it would be efficient to start with it. This is good. However, if I make that a stored procedure with @MinDate as a parameter, it produces a completely inefficient execution plan. (I am recompiling it each time, so it's not a bad cached plan...at least, I sure hope it's not) But here's where it gets weird. If I change the proc to the following: declare @LocalMinDate datetime set @LocalMinDate = @MinDate --where @MinDate is still a parameter create table #smallTable (ID int) insert into #smallTable select (a very small number of rows from some other table) select * from aGiantTable inner join #smallTable on #smallTable.ID = aGiantTable.ID inner join anotherTable on anotherTable.GiantID = aGiantTable.ID where aGiantTable.SomeDateField > @LocalMinDate Then it gives me the efficient plan! So my theory is this: when executing as a plain query (not as a stored procedure), it waits to construct the execution plan for the expensive query until the last minute, so the query optimizer knows that #smallTable is small and uses that information to give the efficient plan. But when executing as a stored procedure, it creates the entire execution plan at once, thus it can't use this bit of information to optimize the plan. But why does using the locally declared variables change this? Why does that delay the creation of the execution plan? Is that actually what's happening? If so, is there a way to force delayed compilation (if that indeed is what's going on here) even when not using local variables in this way? More generally, does anyone have sources on when the execution plan is created for each step of a stored procedure? Googling hasn't provided any helpful information, but I don't think I'm looking for the right thing. Or is my theory just completely unfounded? Edit: Since posting, I've learned of parameter sniffing, and I assume this is what's causing the execution plan to compile prematurely (unless stored procedures indeed compile all at once), so my question remains -- can you force the delay? Or disable the sniffing entirely? The question is academic, since I can force a more efficient plan by replacing the select * from aGiantTable with select * from (select * from aGiantTable where ID in (select ID from #smallTable)) as aGiantTable Or just sucking it up and masking the parameters, but still, this inconsistency has me pretty curious.

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