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  • Handling large integers in python [migrated]

    - by Sushma Palimar
    I had written a program in python to find b such that a prime number p divides b^2-8. The range for b is [1, (p+1)/2]. For small integers it works, say only up to 7 digits. But not for large integers, say for p = 140737471578113. I get the error message for i in range (2,p1,1): MemoryError I wrote the program as #!/usr/bin/python3 p=long(raw_input('enter the prime number:')) p1=long((p+1)/2) for i in range (2,p1,1): s = long((i*i)-8) if (s%p==0): print i

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  • Returning status code where one of many errors could have occured

    - by yttriuszzerbus
    I'm developing a PHP login component which includes functions to manipulate the User object, such as $User->changePassword(string $old, string $new) What I need some advice with is how to return a status, as the function can either succeed (no further information needs to be given) or fail (and the calling code needs to know why, for example incorrect password, database problem etc.) I've come up with the following ideas: Unix-style: return 0 on success, another code on failure. This doesn't seem particularly common in PHP and the language's type-coercion messes with this (a function returning FALSE on success?) This seems to be the best I can think of. Throw an exception on error. PHP's exception support is limited, and this will make life harder for anybody trying to use the functions. Return an array, containing a boolean for "success" or not, and a string or an int for "failure status" if applicable. None of these seem particularly appealing, does anyone have any advice or better ideas?

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  • Difference between '\n' and '\r\n'

    - by sukhbir
    Yes yes, I am aware that '\n' writes a newline in UNIX while for Windows there is the two character sequence: '\r\n'. All this is very nice in theory, but my question is why? Why the carriage return character is extra in Windows? If UNIX can do it in \n why does it take Windows two characters to do this? I am reading David Beazley's Python book and he says: For example, on Windows, writing the character '\n' actually outputs the two- character sequence '\r\n' (and when reading the file back, '\r\n' is translated back into a single '\n' character). Why the extra effort? I will be honest. I have known the difference for a long time but have never bothered to ask WHY. I hope that is answered today. Thanks for your time.

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  • Basic SDL2 Code which "Stop working" when calling SDL_Quit() [migrated]

    - by Rivten
    So I got into SDL2 with C++ quite recently and I did this very simple code : int main(int argc, char** argv) { SDL_Event *event; bool done = false; if(SDL_Init(SDL_INIT_VIDEO) != 0) { std::cerr << "Problèmes pour initialiser la SDL : " << SDL_GetError() << std::endl; return 1; } SDL_Window *window = 0; window = SDL_CreateWindow("Mopion", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, WIDTH, HEIGHT, SDL_WINDOW_SHOWN); if(window == 0) { done = true; } while(!done) { while(SDL_PollEvent(event)) { switch(event->type) { case SDL_QUIT: done = true; break; case SDL_KEYUP: if(event->key.keysym.sym == SDLK_q) { done = true; } break; default: break; } } } SDL_DestroyWindow(window); SDL_Quit(); return 0; } While that code executes at first quite well, when I hit the "Q" key, the window closes but I got a Windows Error Window saying that "My program stopped working." which is not very convenient. Using the debugger, I found that everything is fine until SDL_Quit() is called. Anyone has any idea why this is going on ? Thanks a lot !

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  • What is the best practice for reading a large number of custom settings from a text file?

    - by jawilmont
    So I have been looking through some code I wrote a few years ago for an economic simulation program. Each simulation has a large number of settings that can be saved to a file and later loaded back into the program to re-run the same/similar simulation. Some of the settings are optional or depend on what is being simulated. The code to read back the parameters is basically one very large switch statement (with a few nested switch statements). I was wondering if there is a better way to handle this situation. One line of the settings file might look like this: #RA:1,MT:DiscriminatoryPriceKDoubleAuction,OF:Demo Output.csv,QM:100,NT:5000,KP:0.5 //continues... And some of the code that would read that line: switch( Character.toUpperCase( s.charAt(0) ) ) { case 'R': randSeed = Integer.valueOf( s.substring(3).trim() ); break; case 'M': marketType = s.substring(3).trim(); System.err.println("MarketType: " + marketType); break; case 'O': outputFileName = s.substring(3).trim() ; break; case 'Q': quantityOfMarkets = Integer.valueOf( s.substring(3).trim() ); break; case 'N': maxTradesPerRound = Integer.valueOf( s.substring(3).trim() ); break; case 'K': kParameter = Float.valueOf( s.substring(3).trim() ); break; // continues... }

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  • Key Handling mechanics

    - by Max
    I am new to game development and am working on my first game using OpenGL and C++. I have a game class which handles everything necessary in an update() function. Now i want to handle keyboard inputs. I use GLFW which supports key callbacks. However i wonder how to deal with inputs. Should i record the keys pressed and poll on it the next time my game updates or should the callback immediately perform the necessary actions? And why? Thanks :)

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  • Handling Backups for Rapid Resilience

    The backup and restore system in SQL Server hasn't changed a great deal over the years despite a huge growth in the typical size of databases. When disaster strikes, and an important service is taken offline while a restore is performed, there is often time to reflect on whether it might be possible to design databases for a more rapid recovery of the most critical parts of a database application. Uncover the flexibility of custom metricsKeep up to date from anywhere with SQL Monitor, and monitor the most important data for your servers and applications. Download a free trial.

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  • Handling timeout in network application

    - by user2175831
    How can I handle timeouts in a network application. I'm implementing a provisioning system on a Linux server, the code is huge so I'm going to put the algorithm, it works as like this Read provisioning commands from file Send it to another server using TCP Save the request in hash. Receive the response then if successful response received then remove request from hash if failed response received then retry the message The problem I'm in now is when the program didn't receive the response for a timeout reason then the request will be waiting for a response forever and won't be retried. And please note that I'll be sending hundreds of commands and I have to monitor the timeout commands for all of them. I tried to use timer but that didn't help because I'll end up with so many waiting timers and I'm not sure if this is a good way of doing this. The question is how can I save the message in some data structure and check to remove or retry it later when there is no response from the other end? Please note that I'm willing to change the algorithm to anything you suggest that could deal with the timeouts.

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  • When should I decline to make a requested change?

    - by reuscam
    I work on the software side of a company that provides custom hardware with software running on top of it. Often times the hardware is not engineered well. In those cases, I am often asked first to troubleshoot the problem - of course the symptom is always "your software crashed" or something along those lines. Just recently we had another one of these incidents where power on a USB line is not reliable, and it causes a USB device to fail. This causes a usability problem in one of our applications. I have been asked by upper management to handle this better - continually monitor the USB device, and if it disappears, then reboot, or try to reset it. Doing either of these is not guaranteed to fix anything. Ultimately, the real fix is to correct the reliability of the device from the hardware side. I could improve performance, but not to 100%, and of course I would be using my already limited time to bloat code and add yet another device monitoring thread. So with all that said, how do I make a good decision about when to say that this needs to be a hardware fix, and only a hardware fix? Can I approach this quantitatively, and come up with some sort of definitive yes/no test? I'm sure its not that easy.

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  • Multiple joysticks event handling

    - by hbaktir
    I want to make a game which is totally same idea with "Who pressed the button answers the question" I got 2 joysticks and both connected to a pc.My application will be Winforms and i will develop it on Visual studio 2012 . I 've used SlimDX,Sharpx so far i ' ve nothing for multiple joysticks.I can get the pressed button with timer . All i want to know is which joystick / gamepad pressed 1 button first.Then my problem will be solved Any idea how can i achive this or somebody did it before

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  • handle SIGSEGV in Linux?

    - by user303967
    Hi all, I need handle the SIGSEGV in my Linux app. The reason is some clean up(3-partry lib) must be done before generate core-dump. What is more, the clean up must be performed in the context of calling thread, cannot do in signal handler. So I plan in signal handler to pass the control to the calling thread, after the clean up finished, then use raise(SIGSEGV) to generate the core-dump. The real problem seems the signal_handler cannot pass the control to calling thread, no matter I use post_sem or some others. Any idea to handle this case? Possbile to hijack the SIGSEGV, then in SIGSEGV hander return to another thread to perform some clean up? signal(SIGSEGV, signal_handler); signal_handler() { ... post_sem(); ... } calling thread() { wait_sem(); clean_up(); ... }

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  • Measuring "real" phone signal strength on a mobile phone

    - by Serafeim
    I want to programmatically measure the phone signal strength in a mobile phone. I don't actually care about the mobile phone or the programming environment: It can be based on android or windows mobile or even J2ME and can be from any manufacturer (please no iPhone). However, it needs to be a real, commercial mobile phone and not a special measurement device. This problem is not as easy as it seems with a first look. I am aware that there already exist a number of methods that claim to return the phone signal strength. Some of these are: SystemState.PhoneSignalStrength for WM6 RIL_GetCellTowerInfo for WinCe (dwRxLevel member of returned RILCELLTOWERINFO struct) android.telephony.NeighboringCellInfo.getRssi() for android The problem with the above is that they only return a few (under 10) discrete values, meaning that, for instance, the return values of SystemState.PhoneSignalStrength can only be translated to (for instance) -100 dbm, -90 dbm, -80 dbm, -70 dbm and -60 dbm, something that is not useful for my application, since I'd like to have as much precision as possible. It doesn't matter if there is an undocumented solution that only works on only one phone, if you can tell me a way I'd be grateful. Thanks in advance

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  • Binding a member signal to a function

    - by the_drow
    This line of code compiles correctly without a problem: boost::bind(boost::ref(connected_), boost::dynamic_pointer_cast<session<version> >(shared_from_this()), boost::asio::placeholders::error); However when assigning it to a boost::function or as a callback like this: socket_->async_connect(connection_->remote_endpoint(), boost::bind(boost::ref(connected_), boost::dynamic_pointer_cast<session<version> >(shared_from_this()), boost::asio::placeholders::error)); I'm getting a whole bunch of incomprehensible errors (linked since it's too long to fit here). On the other hand I have succeeded binding a free signal to a boost::function like this: void print(const boost::system::error_code& error) { cout << "session connected"; } int main() { boost::signal<void(const boost::system::error_code &)> connected_; connected_.connect(boost::bind(&print, boost::asio::placeholders::error)); client<>::connection_t::socket_ptr socket_(new client<>::connection_t::socket_t(conn->service())); // shared_ptr of a tcp socket socket_->async_connect(conn->remote_endpoint(), boost::bind(boost::ref(connected_), boost::asio::placeholders::error)); conn->service().run(); // io_service.run() return 0; } This works and prints session connected correctly. What am I doing wrong here?

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  • Django's post_save signal behaves weirdly with models using multi-table inheritance

    - by hekevintran
    Django's post_save signal behaves weirdly with models using multi-table inheritance I am noticing an odd behavior in the way Django's post_save signal works when using a model that has multi-table inheritance. I have these two models: class Animal(models.Model): category = models.CharField(max_length=20) class Dog(Animal): color = models.CharField(max_length=10) I have a post save callback called echo_category: def echo_category(sender, **kwargs): print "category: '%s'" % kwargs['instance'].category post_save.connect(echo_category, sender=Dog) I have this fixture: [ { "pk": 1, "model": "animal.animal", "fields": { "category": "omnivore" } }, { "pk": 1, "model": "animal.dog", "fields": { "color": "brown" } } ] In every part of the program except for in the post_save callback the following is true: from animal.models import Dog Dog.objects.get(pk=1).category == u'omnivore' # True When I run syncdb and the fixture is installed, the echo_category function is run. The output from syncdb is: $ python manage.py syncdb --noinput Installing json fixture 'initial_data' from '~/my_proj/animal/fixtures'. category: '' Installed 2 object(s) from 1 fixture(s) The weird thing here is that the dog object's category attribute is an empty string. Why is it not 'omnivore' like it is everywhere else? As a temporary (hopefully) workaround I reload the object from the database in the post_save callback: def echo_category(sender, **kwargs): instance = kwargs['instance'] instance = sender.objects.get(pk=instance.pk) print "category: '%s'" % instance.category post_save.connect(echo_category, sender=Dog) This works but it is not something I like because I must remember to do it when the model inherits from another model and it must hit the database again. The other weird thing is that I must do instance.pk to get the primary key. The normal 'id' attribute does not work (I cannot use instance.id). I do not know why this is. Maybe this is related to the reason why the category attribute is not doing the right thing?

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  • Android Signal 11 (SIGSEGV)

    - by Naturjoghurt
    I read many posts here and on other sites, but can not find the problem creating my Error: I use an AsyncTask because I want to easily manipulate the UI Thread before and after Execution. In doInBackground I create a ThreadPoolExecutor and execute Runnables. If I only execute 1 Runnable with the Executor, there is no Problem, but if I execute another Runnable I get following Error: 06-26 18:00:42.288: A/libc(25073): Fatal signal 11 (SIGSEGV) at 0x7f486162 (code=1), thread 25106 (pool-1-thread-2) 06-26 18:00:42.304: D/dalvikvm(25073): GC_CONCURRENT freed 119K, 2% free 8908K/9056K, paused 4ms+4ms, total 45ms 06-26 18:00:42.327: I/System.out(25073): In Check All with Prefix: a and Length: 4 06-26 18:00:42.390: I/DEBUG(126): *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** 06-26 18:00:42.390: I/DEBUG(126): Build fingerprint: 'google/yakju/maguro:4.2.2/JDQ39/573038:user/release-keys' 06-26 18:00:42.390: I/DEBUG(126): Revision: '9' 06-26 18:00:42.390: I/DEBUG(126): pid: 25073, tid: 25106, name: pool-1-thread-2 >>> de.uni_duesseldorf.cn.distributed_computing2 <<< 06-26 18:00:42.390: I/DEBUG(126): signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 7f486162 ... 06-26 18:00:42.538: I/DEBUG(126): memory map around fault addr 7f486162: 06-26 18:00:42.538: I/DEBUG(126): 60292000-60391000 06-26 18:00:42.538: I/DEBUG(126): (no map for address) 06-26 18:00:42.538: I/DEBUG(126): bed14000-bed35000 [stack] I set up the ThreadPoolExecutor like this: // numberOfPackages: Number of Runnables to be executed public void initializeThreadPoolExecutor (int numberOfPackages) { int corePoolSize = Runtime.getRuntime().availableProcessors(); int maxPoolSize = numberOfPackages; long keepAliveTime = 60; final BlockingQueue workingQueue = new LinkedBlockingQueue(); executor = new ThreadPoolExecutor(corePoolSize, maxPoolSize, keepAliveTime, TimeUnit.SECONDS, workingQueue); } I have no clue, why it fails when starting the second Thread. Maybe Memory Leaks? Any Help appreciated. Thanks in Advance

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  • pthread_join from a signal handler

    - by liv2hak
    I have a capture program which in addition do capturing data and writing it into a file also prints some statistics.The function that prints the statistics static void* report(void) { /*Print statistics*/ } is called roughly every second using an ALARM that expires every second.So The program is like void capture_program() { pthread_t report_thread while(!exit_now) { if(pthread_create(&report_thread,NULL,report,NULL)){ fprintf(stderr,"Error creating reporting thread! \n"); } /* Capturing code -------------- -------------- */ if(doreport) usleep(5); } } void *report(void *param) { while(true) { if(doreport) { doreport = 0 //access some register from hardware usleep(5) } } } The expiry of the timer sets the doreport flag.If this flag is set report() is called which clears the flag.I am using usleep to alternate between two threads in the program.This seems to work fine. I also have a signal handler to handle SIGINT (i.e CTRL+C) static void anysig(int sig) { if (sig != SIGINT) dagutil_set_signal_handler(SIG_DFL); /* Tell the main loop to exit */ exit_now = 1; return; } My question: 1) Is it safe to call pthread_join from inside the signal handler? 2) Should I use exit_now flag for the report thread as well?

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  • Why my linux signal handler run only once

    - by Henry Fané
    #include <iostream> #include <signal.h> #include <fenv.h> #include <string.h> void signal_handler(int sig, siginfo_t *siginfo, void* context) { std::cout << " signal_handler " << fetestexcept(FE_ALL_EXCEPT) << std::endl; throw "exception"; } void divide() { float a = 1000., b = 0., c, f = 1e-300; c = a / b; std::cout << c << " and f = " << f << std::endl; } void init_sig_hanlder() { feenableexcept(FE_ALL_EXCEPT); struct sigaction sa, initial_sa; sa.sa_sigaction = &signal_handler ; sigemptyset( &sa.sa_mask ) ; sa.sa_flags = SA_SIGINFO; // man sigaction(3) // allows for void(*)(int,siginfo_t*,void*) handler sigaction(SIGFPE, &sa, &initial_sa); } int main(int argc, char** argv) { init_sig_hanlder(); while(true) { try { sleep(1); divide(); } catch(const char * a) { std::cout << "Exception in catch: " << a << std::endl; } catch(...) { std::cout << "Exception in ..." << std::endl; } } return 0; } Produce the following results on Linux/g++4.2: signal_handler 0 Exception in catch: exception inf and f = 0 inf and f = 0 inf and f = 0 inf and f = 0 So, signal handler is executed the first time but the next fp exception does not trigger the handler again. Where am I wrong ?

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  • Computer speakers receive radio station signal

    - by squircle
    I have a set of Logitech 5.1 speakers where each speaker and the source plug into the subwoofer. I'm using a Griffin Firewave with output from my MacBook Pro, and output from my custom-built desktop with a switch in the middle (built it myself out of an old Belkin A/B parallel switch). Recently, I've noticed that I can hear a local Punjabi radio station being picked up by my speakers, and the volume of this interference increases as I increase the volume of the speakers. I'm fairly sure that this radio station is at the low-end of the FM spectrum, below 90MHz (or it may be at the high end, above 105MHz, my memory isn't infallible). It gets quite annoying as I can't put my audio very loud without the interference. I've tried to put a ferrite core on the input cable just before the 3.5mm jacks plug into the subwoofer. I don't know if putting the same core around all three of the cables (green, black, orange) would negate the effects, but I'm assuming not. There has been no change. Is there any reason why this would be happening? I'm assuming the interference is coming somewhere between the FireWave and the subwoofer, because the noise gets amplified with volume increases. If anybody has any suggestions, I'd be grateful!

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  • Reload signal for UWSGI when using Supervisord?

    - by Kerem Ulutas
    I have been using UWSGI behind Nginx and I've set supervisord to restart the Nginx and UWSGI instances in case of a server reboot. I am debugging my application and sometimes need to reload the application. According to this page I should be sending SIGHUP in order to do a graceful reload. I could find a stopsignal config setting on this page, but I couldn't find any entry related to something like "reloadsignal" or "restartsignal". Any ideas?

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  • How to extend Wi-Fi signal across rooms?

    - by Sriram Krishnan
    I moved into a new place and my old Wi-Fi router just doesn't have the range to get into all the rooms. I've been investigating a lot of options and I'm wondering what other folks have done here. Moving the current location of my primary Wi-Fi router is not an option thanks to our cable provider and our landlord. Buy a bigger, beefier router (seems expensive). If so, should I go for one of those draft 802.11n ones to avoid microwave/other Wi-Fi router interference? Set up a router with DD-WRT as a repeater Leech the neighbors' open Wi-Fi access point. Alright, I was kidding about the last one but I'm genuinely curious as to what my best option is.

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  • Improving ANTLR DSL parse-error messages

    - by Dan Fabulich
    I'm working on a domain-specific language (DSL) for non-programmers. Non-programmers make a lot of grammar mistakes: they misspell keywords, they don't close parentheses, they don't terminate blocks, etc. I'm using ANTLR to generate my parser; it provides a nifty mechanism for handling RecognitionExceptions to improve error handling. But I'm finding it pretty hard to develop good error-handling code for my DSL. At this point, I'm considering ways to simplify the language to make it easier for me to provide users with high-quality error messages, but I'm not really sure how to go about this. I think I want to reduce the ambiguity of errors somehow, but I'm not sure how to implement that idea in a grammar. In what ways can I simplify my language to improve parse-error messages for my users? EDIT: Updated to clarify that I'm interested in ways to simplify my language, not just ANTLR error-handling tips in general. (Though, thanks for those!)

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  • Django "comment_was_flagged" signal

    - by tsoporan
    Hello, This is my first time working with django signals and I would like to hook the "comment_was_flagged" signal provided by the comments app to notify me when a comment is flagged. This is my code, but it doesn't seem to work, am I missing something? from django.contrib.comments.signals import comment_was_flagged from django.core.mail import send_mail def comment_flagged_notification(sender, **kwargs): send_mail('testing moderation', 'testing', 'test@localhost', ['[email protected]',]) comment_was_flagged.connect(comment_flagged_notification) (I am just testing the email for now, but I have assured the email is sending properly.) Thanks!

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  • Signal Handling in C

    - by Dave
    How can I implement signal Handling for Ctrl-C and Ctrl-D in C....So If Ctrl-C is pressed then the program will ignore and try to get the input from the user again...If Ctrl-D is pressed then the program will terminate... My program follows: int main(){ char msg[400]; while(1){ printf("Enter: "); fgets(msg,400,stdin); printf("%s\n",msg); } } Thanks, Dave

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