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  • Is select() Ok to implemnet single socket read/write timeout ?

    - by chmike
    I have an application processing network communication with blocking calls. Each thread manages a single connection. I've added a timeout on the read and write operation by using select prior to read or write on the socket. Select is known to be inefficient when dealing with large number of sockets. But is it ok, in term of performance to use it with a single socket or are there more efficient methods to add timeout support on single sockets calls ? The benefit of select is to be portable.

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  • Understanding configuration for parallel calling in web app (IIS + MS SQL)

    - by mmcteam.com.ua
    We have an ASP.NET MVC application + IIS 7.5 + SQL Server 2008 R2. We have to load a lot of aggregate counters on the each page. We decided to use ajax and call with javascript for each counter or groups of counters and return them as JSON result. We solve the problem that user doesn't wait for page loading, page loads fast. User waits for counters loading while seeing other page content. But we thought that if we make calls from javascript - our queries will be make async, but we notice, that it is not. All our javascipt calls runs immediately, but action that they invoke are in queue. If we use Async Controller ability - all counters calculating simultaneously, but user has to wait for the longest counter calculating before page loads. The question: We want to understand what is happens if we use ajax and call two or more actions simultaneously. And how can we configuring this. (also in each action we make some queries to sql server)

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  • Forcing LINQ to SQL to make one single call for all child rows

    - by zaph0d
    Let say I have a method (example taken from another post): public IQueryable<CityBlock> GetCityBlocks(){ var results = from o in db.city_blocks let buildings = GetBuildingsOnBlock(o.block_id) //returns Iqueryable select new CityBlock { BuildingsOnBlock = buildings, BlockOwner = o.block_owner }; return results; } In the calling method I add Skip() and Take() methods plus some filtering and then do a ToList(). The trouble is that I am getting dozens of database calls - one for all the city blocks and then a separate one for each building. Is there a way that I can refactor this code to just make two calls: one for the city blocks and one for all the buildings

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  • Strange profiler behavior: same functions, different performances

    - by arthurprs
    I was learning to use gprof and then i got weird results for this code: int one(int a, int b) { return a / (b + 1); } int two(int a, int b) { return a / (b + 1); } int main() { for (int i = 1; i < 30000000; i++) { two(i, i * 2); one(i, i * 2); } return 0; } and this is the profiler output % cumulative self self total time seconds seconds calls ns/call ns/call name 48.39 0.90 0.90 29999999 30.00 30.00 one(int, int) 40.86 1.66 0.76 29999999 25.33 25.33 two(int, int) 10.75 1.86 0.20 main If i call one then two the result is the inverse, two takes more time than one both are the same functions, but the first calls always take less time then the second Why is that? Note: The assembly code is exactly the same and code is being compiled with no optimizations

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  • C++11: thread_local or array of OpenCL 1.2 cl_kernel objects?

    - by user926918
    I need to run several C++11 threads (GCC 4.7.1) parallely in host. Each of them needs to use a device, say a GPU. As per OpenCL 1.2 spec (p. 357): All OpenCL API calls are thread-safe75 except clSetKernelArg. clSetKernelArg is safe to call from any host thread, and is safe to call re-entrantly so long as concurrent calls operate on different cl_kernel objects. However, the behavior of the cl_kernel object is undefined if clSetKernelArg is called from multiple host threads on the same cl_kernel object at the same time. An elegant way would be to use thread_local cl_kernel objects and the other way I can think of is to use an array of these objects such that i'th thread uses i'th object. As I have not implemented these earlier I was wondering if any of the two are good or are there better ways of getting things done. TIA, S

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  • Vector Troubles in C++

    - by DistortedLojik
    I am currently working on a project that deals with a vector of objects of a People class. The program compiles and runs just fine, but when I use the debugger it dies when trying to do anything with the PersonWrangler object. I currently have 3 different classes, one for the person, a personwrangler which handles all of the people collectively, and a game class that handles the game input and output. Edit: My basic question is to understand why it is dying when it calls outputPeople. Also I would like to understand why my program works exactly as it should unless I use the debugger. The outputPeople function works the way I intended that way. Edit 2: The callstack has 3 bad calls which are: std::vector ::begin(this=0xbaadf00d) std::vector ::size(this=0xbaadf00d) PersonWrangler::outputPeople(this=0xbaadf00d) Relevant code: class Game { public: Game(); void gameLoop(); void menu(); void setStatus(bool inputStatus); bool getStatus(); PersonWrangler* hal; private: bool status; }; which calls outputPeople where it promptly dies from a baadf00d error. void Game::menu() { hal->outputPeople(); } where hal is an object of PersonWrangler type class PersonWrangler { public: PersonWrangler(int inputStartingNum); void outputPeople(); vector<Person*> peopleVector; vector<Person*>::iterator personIterator; int totalPeople; }; and the outputPeople function is defined as void PersonWrangler::outputPeople() { int totalConnections = 0; cout << " Total People:" << peopleVector.size() << endl; for (unsigned int i = 0;i < peopleVector.size();i++) { sort(peopleVector[i]->connectionsVector.begin(),peopleVector[i]->connectionsVector.end()); peopleVector[i]->connectionsVector.erase( unique (peopleVector[i]->connectionsVector.begin(),peopleVector[i]->connectionsVector.end()),peopleVector[i]->connectionsVector.end()); peopleVector[i]->outputPerson(); totalConnections+=peopleVector[i]->connectionsVector.size(); } cout << "Total connections:" << totalConnections/2 << endl; }

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  • Do I need to syncronize thread access to an int

    - by Martin Harris
    I've just written a method that is called by multiple threads simultaneously and I need to keep track of when all the threads have completed, the code uses this pattern: private void RunReport() { _reportsRunning++; try { //code to run the report } finally { _reportsRunning--; } } This is the only place within the code that _reportsRunning's value is changed, and the method takes about a second to run. Occasionally when I have more than six or so threads running reports together the final result for _reportsRunning can get down to -1, if I wrap the calls to _runningReports++ and _runningReports-- in a lock then the behaviour appears to be correct and consistant. So, to the question: When I was learning multithreading in C++ I was taught that you didn't need to synchronize calls to increment and decrement operations because they were always one assembly instruction and therefore it was impossible for the thread to be switched out mid-call. Was I taught correctly, and if so how come that doesn't hold true for C#?

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  • C++ Vector at/[] operator speed

    - by sub
    In order to give functions the option to modify the vector I can't do curr = myvec.at( i ); doThis( curr ); doThat( curr ); doStuffWith( curr ); But I have to do: doThis( myvec.at( i ) ); doThat( myvec.at( i ) ); doStuffWith( myvec.at( i ) ); (as the answers of my other question pointed out) I'm going to make a hell lot of calls to myvec.at() then. How fast is it, compared to the first example using a variable to store the result? Is there a different option for me? Can I somehow use pointers? When it's getting serious there will be thousands of calls to myvec.at() per second. So every little performance-eater is important.

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  • Through Java, make a call to Javascript functions on networked device?

    - by stjowa
    I am doing device monitoring on a networked system. I need to know how to make Javascript calls on that device via its IP address to get certain status information (this device's status is only available through Javascript APIs, not SNMP, etc). I am working in Java. ADDED: The specific device is an Amino set-top-box. It has what it calls JMACX: JavaScript Media Access Control Extensions API specification. It allows you within an HTML document to use that API to get MUCH information about the device (cpu usage, channel info, remote-control options, etc.). I need to get this information within a Java program for specific monitoring purposes. Perhaps possible with HTTP requests? Any input would be greatly appreciated. Thanks, Steve

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  • Trying to understand the Zend_Auth OpenId

    - by Will Olbrys
    I'm using a slightly modified version of the Zend_Auth_OpenId classes to get openid logins from google apps. The results are very positive, as I seem to be getting successful results from Google. I cannot get successful results passed to Zend_Auth, though. For example, Zend_Auth_Adapter_OpenId on line 241: if (!$consumer->login($id, $this->_returnTo, $this->_root, $this->_extensions, $this->_response)) { return new Zend_Auth_Result( Zend_Auth_Result::FAILURE, $id, array("Authentication failed", $consumer->getError())); } The consumer calls login() which in turn calls the private method _checkId() in Zend_OpenId_Consumer. _checkId() always ends in redirecting to the openid server. How is this ever supposed to return a valid Zend_Auth_Result object? I'm pretty close to giving up and trying to implement another OpenId library, but I'm so close to just making this work. I must be missing something so obvious! Maybe I don't understand how openid works exactly, but if someone could help me understand I would really appreciate it.

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  • Simple Search and Replace use of Regular Expression

    - by nunos
    So, I am adapting some code I found online to suit my needs. However, my set_pixel function has two more parameters. Since there are lots of calls to this function even doing a quick paste over would be very tedious. So, I thought this would be a good time for me to learn some simple regular expressions. So, I have calls of this type: set_pixel(arg1, arg2); which I want to change to something like: set_pixel(arg1, arg2, arg3, arg4); Note: arg1 and and 2 should be preserved, whereas arg3 and arg4 are most of the time the same. How can I achieve this?

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  • Weird seg fault problem

    - by bluedaemon
    Greetings, I'm having a weird seg fault problem. My application dumps a core file at runtime. After digging into it I found it died in this block: #include <lib1/c.h> ... x::c obj; obj.func1(); I defined class c in a library lib1: namespace x { struct c { c(); ~c(); void fun1(); vector<char *> _data; }; } x::c::c() { } x::c::~c() { for ( int i = 0; i < _data.size(); ++i ) delete _data[i]; } I could not figure it out for some time till I ran nm on the lib1.so file: there are more function definitions than I defined: x::c::c() x::c::c() x::c::~c() x::c::~c() x::c::func1() x::c::func2() After searching in code base I found someone else defined a class with same name in same namespace, but in another library lib2 as follows: namespace x { struct c { c(); ~c(); void func2(); vector<string> strs_; }; } x::c::c() { } x::c::~c() { } My application links to lib2, which has dependency on lib1. This interesting behavior brings several questions: Why would it even work? I would expect a "multiple definitions" error while linking against lib2 (which depends upon lib1) but never had such. The application seems to be doing what's defined in func1 except it dumps a core at runtime. After attaching debugger, I found my application calls the ctor of class c in lib2, then calls func1 (defined in lib1). When going out of scope it calls dtor of class c in lib2, where the seg fault occurs. Can anybody teach me how this could even occur? How can I prevent such problems from happening again? Is there any C++ syntax I can use? Forgot to mention I'm using g++ 4.1 on RHEL4, thank you very much!

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  • Call external library from PHP. What is faster: exec or extension?

    - by robusta
    Hi, I need to make calls from webpage to external library written in C++ and display the result. Platform is Linux, Apache, PHP. My current idea is to use PHP service which will call my library/program. I found that there are two possible ways to do this: 1) use PHP 'exec' function 2) write PHP extension I am curious what works more effective? Faster? Less load the server? I will probably need to do 4 calls per second, so I want to be as optimal as possible. P.S. If you are aware of some other (more effective) way of calling C++ library or program from webpage, please let me know. Thanks a lot, Robusta

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  • Is an iPhone Call Recorder theoretically possible?

    - by Adam Dempsey
    NOTE: I know neither the iPhone SDK or Objective C, just wondering if possible. I know obviously it would have to be on a Jailbroken device anyway, but it is technically possible for a iPhone call recording application to be made, or is it not possible to hook into the calls or the audio input/output? I know obviously there would be no 'official' way of doing it and certainly not from an App Store application. And I know there are call recording apps which place outgoing calls through their own servers. Just wondering if the reason it doesn't exist yet is just because no-one has coded it or if it's not actually possible?

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  • Changing the value of a macro at run time

    - by BrandiNo
    I'm working in Visual Studio 2010, using C++ code. What I'm trying to do is change the value of a preprocessor directive during run time, not sure if it's possible but i've tried this.. somefile.h static int mValue = 0; #define POO = mValue; ... #if POO 0 //define class methods #else //define class methods differently } main.cpp main() { //Code calls constructor and methods allowed when POO is 0 //Code increments mValue //Code calls constructor and methods allowed when POO is 1 } How can POO be changed so that class objects uses a different implementation of other methods? Or if it's not possible, what's a another approach to this?

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  • What's some simple F# code that generates the .tail IL instruction?

    - by kld2010
    I'd like to see the .tail IL instruction, but the simple recursive functions using tail calls that I've been writing are apparently optimized into loops. I'm actually guessing on this, as I'm not entirely sure what a loop looks like in Reflector. I definitely don't see any .tail opcodes though. I have "Generate tail calls" checked in my project's properties. I've also tried both Debug and Release builds in Reflector. The code I used is from Programming F# by Chris Smith, page 190: let factorial x = // Keep track of both x and an accumulator value (acc) let rec tailRecursiveFactorial x acc = if x <= 1 then acc else tailRecursiveFactorial (x - 1) (acc * x) tailRecursiveFactorial x 1 Can anyone suggest some simple F# code which will indeed generate .tail?

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  • Java classloader delegation model ?

    - by Tony
    When calling a loadClass() on a class loader, the class loader firstly check the class if had been loaded or directly delegate this check to it's parent class loader ? Java api says: When requested to find a class or resource, a ClassLoader instance will delegate the search for the class or resource to its parent class loader before attempting to find the class or resource itself. But there's a specific chapter about class loader in the book <java reflection in action> and says: Class loader calls findLoadedClass to check if the class has been loaded already.If a class loader does not find a loaded class, calls loadClass on the parent class loader. which is correct ?

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  • radio button group matlab

    - by vijisai
    i have two set of button groups. first button groups has two radio buttons and second group has four radio buttons. if button 1 is selected in group1 and any one from the group 2. similarly for button2 in group 1 and any one from group2, respective function calls must be made on click of push button with these combinations. how to do it. there will be 8 separate function calls for their respective combinations. how to do the combination of button groups. switch case or if else statement did not work out?? kindly help.

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  • servlet authentication and further reference to the credentials

    - by user553592
    What I got so far: It all begins with an HTML form which prompts the user for a username and password. From there it post the acquired user/pass to a servlet, GateKeeper. GateKeeper determines if the user/pass combination match any records in the MySQL database. Here is the sql I use: SELECT id FROM Users WHERE username='?' AND password=MD5('?') where the ? indicate information provided the previous HTML form. What I need now: I need some way to store the username and id of the record in the database. GateKeeper redirects the user to a control panel upon success. Therefore, I need a method to reference the username to display simple greetings, etc and also the id so it eliminates unnecessary calls to the database. The control panel may make AJAX calls to Servlets that preform some sort of task to the MySQL database.

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  • Best way to develop a secured application. With .net

    - by John S
    Hello, we are developing a windows application, and as most apps out there, there is a login form. What I don't like is that the login form validates the user and opens the main form if user and pass are correct. Simple as is. All the function calls etc are called without verifying the user and pass again, what should be the right thing to do. What's the best way to develop a secured application that if for any reason, the login form is by passed, the other function calls won't run? Some devs suggested that we include an user and pass params on each function, which seems to be wrong... thanks!

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  • What will or won't cause a thread to block (a question from a test)

    - by fingerprint211b
    I've had a test, and there was a question I lost some points on, because I wasn't able to answer it : Which of the following is NOT a condition which can cause a thread to block : Calling an objects's wait() method Waiting for an I/O operation Calling sleep() Calling yield() Calling join() As far as I know, all of these are blocking calls : wait() returns when an something calls notify(), blocks until then If the thread is WAITING for an I/O operation then it's obviously blocked sleep(), obviously, blocks until the time runs out, or something wakes up the thread yield() "cancels the rest of the thread's timeslice" (lacking a better term), and returns only when the thread is active again join() blocks until the thread it's waiting for terminates. Am I missing something here?

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  • Windows 7 .NET 3.5.1 - 2.0 Slightly Corrupted, How to Repair?

    - by Quinxy von Besiex
    My Windows 7 included .NET installation (3.5 to 2.0) appears very slightly and particularly corrupted and I am trying to fix it without reinstalling Windows or trying to revert to backups. Everything was working and then my hard drive started corrupting a few files and checkdisk found bad clusters so I imaged the drive to a new one. As soon as I booted on the new drive everything worked except programs which call the System.Net.NetworkInformation methods within .NET 3.5 to 2.0 (like Ping() and IsNetworkAvailable()), which immediately crash the app in which the calls are (those calls in .NET 4.0 works fine). Those methods are found inside System.dll, and I assume call native methods which I believe are inside winnsi.dll or iphlpapi.dll or something else (I've not found this yet); I assume it calls native methods because the exception which causes the crash is Fatal Execution Engine Error which people mention is usually related to calling native methods and marshaling data between them. A huge clue about the culprit is likely found in the fact that when I launch the exact same crashing application through a code profiler (which executes the exe and captures stats on which methods took the longest) the app works fine, no crash at all! How could running it within the profiler work and running it outside not work? That seems the key to the mystery. I've used procmon to catch all the registry, filesystem, and network events from the crashing execution and the profiler-run successful execution and compared the two outputs but didn't learn much (I see the moment at which the non-profiled app crashes, but up until then they behave the same, loaded the same modules, ). The only big difference seems to be that at the moment before the app crash the profiler-executed code creates 4-6 new threads and the directly executed code only creates 1-2. I have diffed the files/directories which seemed most relevant (the .NET stuff under Windows and Program Files) pre- and post- disk trouble and seen no changes where I didn't expect any (no obvious file corruption). I have diffed the software and system registry hives pre- and post- disk trouble and seen no changes which seemed relevant. I have created a new user account and cleaned up any environment variables in case environment was related. No change. I did "sfc /scannow" and it found no integrity problems. I tried "ngen update" to regenerate pre-compiled code in case I missed something that might be damaged and nothing changed. I assume I need to repair my .NET installation but because Windows 7 included .NET 3.5 - 2.0 you can't just re-run a .NET installer to redo it. I do not have access to the Windows disks to try to re-install Windows over itself (the computer has a recovery partition but it is unusable); also the drive uses a whole-disk encryption solution and re-installing would be difficult. I absolutely do not want to start from scratch here and install a fresh Windows, reinstall dozens of software packages, try and remember dozens of development-related customizations/etc. Given all that... does anyone have any helpful advice? I need .NET 3.5 - 2.0 working as I am a developer and need to build and test against it. Thanks! Quinxy

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