default program - Page 583

Prototyping Qt/C++ in Python

- by tstenner

I want to write a C++ application with Qt, but build a prototype first using Python and then gradually replace the Python code with C++. Is this the right approach, and what tools (bindings, binding generators, IDE) should I use? Ideally, everything should be available in the Ubuntu repositories so I wouldn't have to worry about incompatible or old versions and have everything set up with a simple aptitude install. Is there any comprehensive documentation about this process or do I have to learn every single component, and if yes, which ones? Right now I have multiple choices to make: Qt Creator, because of the nice auto completion and Qt integration. Eclipse, as it offers support for both C++ and Python. Eric (haven't used it yet) Vim PySide as it's working with CMake and Boost.Python, so theoretically it will make replacing python code easier. PyQt as it's more widely used (more support) and is available as a Debian package. Edit: As I will have to deploy the program to various computers, the C++-solution would require 1-5 files (the program and some library files if I'm linking it statically), using Python I'd have to build PyQt/PySide/SIP/whatever on every platform and explain how to install Python and everything else.

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Memory Leak in returning NSMutableArray from class

- by Structurer

Hi I am quite new to Objective C for the iPhone, so I hope you wont kill me for asking a simple question. I have made an App that works fine, except that Instruments reports memory leaks from the class below. I use it to store settings from one class and then retrieve them from another class. These settings are stored on a file so they can be retrieved every time the App is ran. What can I do do release the "setting" and is there anything that can be done to call (use) the class in a smarter way? Thanks ----- Below is Settings.m ----- import "Settings.h" @implementation Settings @synthesize settings; -(NSString *)dataFilePath // Return path for settingfile, including filename { NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *documentsDirectory = [paths objectAtIndex:0]; return [documentsDirectory stringByAppendingPathComponent:kUserSettingsFileName]; } -(NSMutableArray *)getParameters // Return settings from disk after checking if file exist (if not create with default values) { NSString *filePath = [self dataFilePath]; if ([[NSFileManager defaultManager] fileExistsAtPath:filePath]) // Getting data from file { settings = [[NSMutableArray alloc] initWithContentsOfFile:filePath]; } else // Creating default settings { settings = [[NSMutableArray alloc] initWithObjects: [NSNumber numberWithInteger:50], [NSNumber numberWithInteger:50], nil]; [settings writeToFile:[self dataFilePath] atomically:YES]; } return settings; } ----- Below is my other class from where I call my Settings class ----- // Get settings from file Settings *aSetting = [[Settings alloc] init]; mySettings = [aSetting getParameters]; [aSetting release];

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F# - POCO Class

- by ebb

Hey there! I'm trying to write a POCO class in proper F#... But something is wrong.. The C# code that I want to "translate" to proper F# is: public class MyTest { [Key] public int ID { get; set; } public string Name { get; set; } } The closest I can come to the above code in F# is something like: type Mytest() = let mutable _id : int = 0; let mutable _name : string = null; [<KeyAttribute>] member x.ID with public get() : int = _id and public set(value) = _id <- value member x.Name with public get() : string = _name and public set value = _name <- value However when I try to access the properties of the F# version it just returns a compile error saying "Lookup on object of indeterminate type based on information prior to this program point. A type annotation may be needed prior to this program point to constrain the type of the object. This may allow the lookup to be resolved." The code thats trying to get the property is a part of my Repository (I'm using EF Code First). module Databasethings = let GetEntries = let ctx = new SevenContext() let mydbset = ctx.Set<MyTest>() let entries = mydbset.Select(fun item -> item.Name).ToList() // This line comes up with a compile error at "item.Name" (the compile error is written above) entries What the hell is going on? Thanks in advance!

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Avoiding repeated subqueries when 'WITH' is unavailable

- by EloquentGeek

MySQL v5.0.58. Tables, with foreign key constraints etc and other non-relevant details omitted for brevity: CREATE TABLE `fixture` ( `id` int(11) NOT NULL auto_increment, `competition_id` int(11) NOT NULL, `name` varchar(50) NOT NULL, `scheduled` datetime default NULL, `played` datetime default NULL, PRIMARY KEY (`id`) ); CREATE TABLE `result` ( `id` int(11) NOT NULL auto_increment, `fixture_id` int(11) NOT NULL, `team_id` int(11) NOT NULL, `score` int(11) NOT NULL, `place` int(11) NOT NULL, PRIMARY KEY (`id`) ); CREATE TABLE `team` ( `id` int(11) NOT NULL auto_increment, `name` varchar(50) NOT NULL, PRIMARY KEY (`id`) ); Where: A draw will set result.place to 0 result.place will otherwise contain an integer representing first place, second place, and so on The task is to return a string describing the most recently played result in a given competition for a given team. The format should be "def Team X,Team Y" if the given team was victorious, "lost to Team X" if the given team lost, and "drew with Team X" if there was a draw. And yes, in theory there could be more than two teams per fixture (though 1 v 1 will be the most common case). This works, but feels really inefficient: SELECT CONCAT( (SELECT CASE `result`.`place` WHEN 0 THEN "drew with" WHEN 1 THEN "def" ELSE "lost to" END FROM `result` WHERE `result`.`fixture_id` = (SELECT `fixture`.`id` FROM `fixture` LEFT JOIN `result` ON `result`.`fixture_id` = `fixture`.`id` WHERE `fixture`.`competition_id` = 2 AND `result`.`team_id` = 1 ORDER BY `fixture`.`played` DESC LIMIT 1) AND `result`.`team_id` = 1), ' ', (SELECT GROUP_CONCAT(`team`.`name`) FROM `fixture` LEFT JOIN `result` ON `result`.`fixture_id` = `fixture`.`id` LEFT JOIN `team` ON `result`.`team_id` = `team`.`id` WHERE `fixture`.`id` = (SELECT `fixture`.`id` FROM `fixture` LEFT JOIN `result` ON `result`.`fixture_id` = `fixture`.`id` WHERE `fixture`.`competition_id` = 2 AND `result`.`team_id` = 1 ORDER BY `fixture`.`played` DESC LIMIT 1) AND `team`.`id` != 1) ) Have I missed something really obvious, or should I simply not try to do this in one query? Or does the current difficulty reflect a poor table design?

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deserializing multiple types from a stream

- by clanier9

I have a card game program, and so far, the chat works great back and forth over the TCPClient streams between host and client. I want to make it do this with serializing and deserializing so that I can also pass cards between host and client. I tried to create a separate TCPClient stream for the passing of cards but it didn't work and figured it may be easier to keep one TCPClient stream that gets the text messages as well as cards. So I created a class, called cereal, which has the properties for the cards that will help me rebuild the card from an embedded database of cards on the other end. Is there a way to make my program figure out whether a card has been put in the stream or if it's just text in the stream so I can properly deserialize it to a string or to a cereal? Or should I add a string property to my cereal class and when that property is filled in after deserializing to the cereal, i'll know it's just text (if that field is empty after deserializing i'll know it's a card)? I'm thinking a try catch, where it tries to deserialize to a string, and if it fails it will catch and cast as a cereal. Or am I just way off base with this and should choose another route? I'm using visual studio 2011, am using a binaryformatter, and am new to serializing/deserializing.

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jquery question

- by OM The Eternity

I am using the Jquery library to copy the text enter in one textfield to another textfield using a check box when clicked.. which is as follows <html> <head> <script src="js/jquery.js" ></script> </head> <body> <form> <input type="text" name="startdate" id="startdate" value=""/> <input type="text" name="enddate" id="enddate" value=""/> <input type="checkbox" name="checker" id="checker" /> </form> <script> $(document).ready(function(){ $("input#checker").bind("click",function(o){ if($("input#checker:checked").length){ $("#enddate").val($("#startdate").val()); }else{ $("#enddate").val(""); } }); } ); </script> </body> </html> now here i want the check box to be selected by default, so that the data entered in start date get copied automatically as check box is checked by default... so what event should be called here in jquery script? please help me in resolving this issue...

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PHP Function parameters - problem with var not being set

- by Marty

So I am obviously not a very good programmer. I have written this small function: function dispAdjuggler($atts) { extract(shortcode_atts(array( 'slot' => '' ), $atts)); $adspot = ''; $adtype = ''; // Get blog # we're on global $blog_id; switch ($blog_id) { case 1: // root blog HOME page if (is_home()) { switch ($slot) { case 'top_leaderboard': $adspot = '855525'; $adtype = '608934'; break; case 'right_halfpage': $adspot = '855216'; $adtype = '855220'; break; case 'right_med-rectangle': $adspot = '858222'; $adtype = '613526'; break; default: throw new Exception("Ad slot is not defined"); break; } When I reference the function on a page like so: <?php dispAdjuggler("top_leaderboard"); ?> The switch is throwing the default exception. What am I doing wrong here? Thanks!!

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Returning reference to object is not changing the address in c++

- by ashish-sangwan

I am trying to understand functions returning a reference. For that I have written a simple program: #include<iostream> using namespace std; class test { int i; friend test& func(); public: test(int j){i=j;} void show(){cout<<i<<endl;} }; test& func() { test temp(10); return temp; //// Address of temp=0xbfcb2874 } int main() { test obj1(50); // Address of obj1=0xbfcb28a0 func()=obj1; <= Problem:The address of obj1 is not changing obj1.show(); // // Address of obj1=0xbfcb28a0 return 0; } I ran the program using gdb and observed that the address of obj1 still remains same, but I expect it to get changed to 0xbfcb2874. I am not clear with the concept. Please help.

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MySQL left outer join is slow

- by Ryan Doherty

Hi, hoping to get some help with this query, I've worked at it for a while now and can't get it any faster: SELECT date, count(id) as 'visits' FROM dates LEFT OUTER JOIN visits ON (dates.date = DATE(visits.start) and account_id = 40 ) WHERE date >= '2010-12-13' AND date <= '2011-1-13' GROUP BY date ORDER BY date ASC That query takes about 8 seconds to run. I've added indexes on dates.date, visits.start, visits.account_id and visits.start+visits.account_id and can't get it to run any faster. Table structure (only showing relevant columns in visit table): create table visits ( `id` int(11) NOT NULL AUTO_INCREMENT, `account_id` int(11) NOT NULL, `start` DATETIME NOT NULL, `end` DATETIME NULL, PRIMARY KEY (`id`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8; CREATE TABLE `dates` ( `date` date NOT NULL, PRIMARY KEY (`date`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1; dates table contains all days from 2010-1-1 to 2020-1-1 (~3k rows). visits table contains about 400k rows dating from 2010-6-1 to yesterday. I'm using the date table so the join will return 0 visits for days there were no visits. Results I want for reference: +------------+--------+ | date | visits | +------------+--------+ | 2010-12-13 | 301 | | 2010-12-14 | 356 | | 2010-12-15 | 423 | | 2010-12-16 | 332 | | 2010-12-17 | 346 | | 2010-12-18 | 226 | | 2010-12-19 | 213 | | 2010-12-20 | 311 | | 2010-12-21 | 273 | | 2010-12-22 | 286 | | 2010-12-23 | 241 | | 2010-12-24 | 149 | | 2010-12-25 | 102 | | 2010-12-26 | 174 | | 2010-12-27 | 258 | | 2010-12-28 | 348 | | 2010-12-29 | 392 | | 2010-12-30 | 395 | | 2010-12-31 | 278 | | 2011-01-01 | 241 | | 2011-01-02 | 295 | | 2011-01-03 | 369 | | 2011-01-04 | 438 | | 2011-01-05 | 393 | | 2011-01-06 | 368 | | 2011-01-07 | 435 | | 2011-01-08 | 313 | | 2011-01-09 | 250 | | 2011-01-10 | 345 | | 2011-01-11 | 387 | | 2011-01-12 | 0 | | 2011-01-13 | 0 | +------------+--------+ Thanks in advance for any help!

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user enter data to different arrays

- by user2900469

This is fragment of my code (arrays as you can see): double[] Price; String[] names; int[] Quantity; Price = new double[5]; names = new String[5]; Quantity = new int[5]; Price[1] = 3.10; Price[2] = 7.80; Price[3] = 0.20; names[1] = "Ballpen"; names[2] = "Notebook"; names[3] = "Envelope"; Quantity[1] = 20; Quantity[2] = 5; Quantity[3] = 140; I enter data to arrays by myself in this case. Now i want to change my code so that my program asks user for names, price and quantity (using the Scanner class). After user enter data, program keep this in three different arrays. I dont know how to transfer data from user to arrays. I would be grateful for some example code or any help.

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[FIXED] Scan file contents into an array of a structure.

- by ZaZu

Hello, I have a structure in my program that contains a particular array. I want to scan a random file with numbers and put the contents into that array. This is my code : ( NOTE : This is a sample from a bigger program, so I need the structure and arrays as declared ) The contents of the file are basically : 5 4 3 2 5 3 4 2 #include<stdio.h> #define first 500 #define sec 500 struct trial{ int f; int r; float what[first][sec]; }; int trialtest(trial *test); main(){ trial test; trialtest(&test); } int trialtest(trial *test){ int z,x,i; FILE *fin; fin=fopen("randomfile.txt","r"); for(i=0;i<5;i++){ fscanf(fin,"%5.2f\t",(*test).what[z][x]); } fclose(fin); return 0; } But the problem is, whenever this I run this code, I get this error : (25) : warning 508 - Data of type 'double' supplied where a pointer is required I tried adding do{ for(i=0;i<5;i++){ q=fscanf(fin,"%5.2f\t",(*test).what[z][x]); } }while(q!=EOF); But that didnt work either, it gives the same error. Does anyone have a solution to this problem ?

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After calling a COM-dll component, C# exceptions are not caught by the debugger

- by shlomil

I'm using a COM dll provided to me by 3rd-party software company (I don't have the source code). I do know for sure they used Java to implement it because their objects contain property names like 'JvmVersion'. After I instantiated an object introduced by the provided COM dll, all exceptions in my C# program cannot be caught by the VS debugger and every time an exception occurs I get the default Windows Debugger Selection dialog (And that's while executing my program in debug mode under a full VisualStudio debugging environment). To illustrate: throw new Exception("exception 1"); m_moo = new moo(); // Component taken from the COM-dll throw new Exception("exception 2"); Exception 1 will be caught by VS and show the "yellow exception window". Exception 2 will open a dialog titled "Visual Studio Just-In-Time Debugger" containing the text "An unhandled win32 exception occurred in myfile.vshost.exe[1348]." followed by a list of the existing VS instances on my system to select from. I guess the instantiation of "moo" object overrides C#'s exception handler or something like that. Am I correct and is there a way to preserve C#'s exception handler?

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Convert enumeration to string

- by emptyheaded

I am trying to build a function that converts an item from an enum to its corresponding string. The enums I use are fairly long, so I didn't want to use a switch-case. I found a method using boost::unordered_map very convenient, but I don't know how to make a default return (when there is no item matching the enum). const boost::unordered_map<enum_type, const std::string> enumToString = boost::assign::map_list_of (data_1, "data_1") (data_2, "data_2"); I tried to create an additional function: std::string convert(enum_type entry) { if (enumToString.find(entry)) // not sure what test to place here, return enumToString.at(entry); //because the find method returns an iter else return "invalid_value"; } I even tried something exceedingly wrong: std::string convert(enum_type entry) { try{ return enumToString.at(entry); } catch(...){ return "invalid_value"; } } Result: evil "Debug" runtime error. Can somebody give me a suggestion on how to either 1) find an easier method to convert enum to a string with the same name as the enum item 2) find a way to use already built boost methods to get a default value from a hash map (best option) 3) find what to place in the test to use a function that returns either the pair of the key-value, or a different string if the key is not found in the map. Thank you very much.

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Proper QUuid usage in Qt ? (7-Zip DLL usage problems (QLibrary, QUuid GUID conversion, interfaces))

- by whipsnap

Hi, I'm trying to write a program that would use 7-Zip DLL for reading files from inside archive files (7z, zip etc). Here's where I'm so far: #include QtCore/QCoreApplication #include QLibrary #include QUuid #include iostream using namespace std; #include "7z910/CPP/7zip/Archive/IArchive.h" #include "7z910/CPP/7zip/IStream.h" #include "MyCom.h" // {23170F69-40C1-278A-1000-000110070000} QUuid CLSID_CFormat7z(0x23170F69, 0x40C1, 0x278A, 0x10, 0x00, 0x00, 0x01, 0x10, 0x07, 0x00, 0x00); typedef int (*CreateObjectFunc)( const GUID *clsID, const GUID *interfaceID, void **outObject); void readFileInArchive() { QLibrary myLib("7z.dll"); CreateObjectFunc myFunction = (CreateObjectFunc)myLib.resolve("CreateObject"); if (myFunction == 0) { cout outArchive; myFunction(&CLSID_CFormat7z, &IID_IOutArchive, (void **)&outArchive); } int main(int argc, char *argv[]) { QCoreApplication a(argc, argv); readFileInArchive(); return a.exec(); } Trying to build that in Qt Creator will lead to following error: cannot convert 'QUuid*' to 'const GUID*' in argument passing How should QUuid be correctly used in this context? Also, being a C++ and Qt newbie I haven't yet quite grasped templates or interfaces, so overall I'm having trouble getting through these first steps. If someone could give tips or even example code on how for example an image file could be extracted from ZIP file (to be shown in Qt GUI later on*), I would highly appreciate that. My main goal at the moment is to write a program with GUI for selecting archive files containing image files (PNG, JPG etc) and displaying those files one at a time in the GUI. A Qt based CDisplayEx in short.

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loop is cut one element of the array

- by Walaa

The problem is : Write a program that reads a number n and then declares an array of n elements. The program then fills the array with the first n numbers, where each number is two to the power of the previous. Finally, display array’s contents. My code : import java.util.*; public class Q1 { static Scanner scan = new Scanner (System.in); public static void main(String args [] ) { int num; int i = 0; System.out.println("Enter a number :"); num = scan.nextInt(); double [] a=new double[num]; a[0]= num ; for ( ;i<=a.length-1 ; i++) { a[i+1] = Math.pow(2,a[i]); System.out.println((int)(a[i]) ); } } } The error is : ----jGRASP exec: java Q1 Enter a number : 4 4 16 65536 Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 4 at Q1.main(Q1.java:16) ----jGRASP wedge2: exit code for process is 1. why it says that? And the number by user printed twice!

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wpf progress bar slows 10x times serial port communications... how could be possible that?

- by D_Guidi

I know that this could look a dumb question, but here's my problem. I have a worker dialog that "hides" a backgroundworker, so in a worker thread I do my job, I report the progress in a standard way and then I show the results in my WPF program. The dialog contains a simply animated gif and a standard wpf progress bar, and when a progress is notified I set Value property. All lokks as usual and works well for any kind of job, like web service calls, db queries, background elaboration and so on. For my job we use also many "couplers", card readers that reads data from smart card, that are managed with native C code that access to serial port (so, I don't use .NET SerialPort object). I have some nunit tests and I read a sample card in 10 seconds, but using my actual program, under the backgroundworker and showing my worker dialog, I need 1.30 minutes to do the SAME job. I struggled into problem for days until I decide to remove the worker dialog, and without dialog I obtain the same performances of the tests! So I investigated, and It's not the dialog, not the animated gif, but the wpf progress bar! Simply the fact that a progress bar is shown (so, no animation, no Value set called, nothing of nothing) slows serialport communicatitons. Looks incredible? I've tested this behavior and it's exactly what happens.

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c++ figuring out memory layout of members programatically

- by anon

Suppose in one program, I'm given: class Foo { int x; double y; char z; }; class Bar { Foo f1; int t; Foo f2; }; int main() { Bar b; bar.f1.z = 'h'; bar.f2.z = 'w'; ... some crap setting value of b; FILE *f = fopen("dump", "wb"); // c-style file fwrite(&b, sizeof(Bar), 1, f); } Suppose in another program, I have: int main() { File *f = fopen("dump", "rb"); std::string Foo = "int x; double y; char z;"; std::string Bar = "Foo f1; int t; Foo f2;"; // now, given this is it possible to read out // the value of bar.f1.z and bar.f2.z set earlier? } WHat I'm asking is: given I have the types of a class, can I figure out how C++ lays it out?

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Is glDisableClientState required?

- by Shawn

Every example I've come across for rendering array data is similar to the following code, in which in your drawing loop you first call glEnableClientState for what you will be using and when you are done you call glDisableClientState: void drawScene(void) { glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT); glEnableClientState(GL_VERTEX_ARRAY); glEnableClientState(GL_TEXTURE_COORD_ARRAY); glBindTexture(GL_TEXTURE_2D, texturePointerA); glTexCoordPointer(2, GL_FLOAT, 0,textureCoordA); glVertexPointer(3, GL_FLOAT, 0, verticesA); glDrawElements(GL_QUADS, numPointsDrawnA, GL_UNSIGNED_BYTE, drawIndicesA); glBindTexture(GL_TEXTURE_2D, texturePointerB); glTexCoordPointer(2, GL_FLOAT, 0,textureCoordB); glVertexPointer(3, GL_FLOAT, 0, verticesB); glDrawElements(GL_QUADS, numPointsDrawnB, GL_UNSIGNED_BYTE, drawIndicesB); glDisableClientState(GL_TEXTURE_COORD_ARRAY); glDisableClientState(GL_VERTEX_ARRAY); } In my program I am always using texture coordinates and vertex arrays, so I thought it was pointless to keep enabling and disabling them every frame. I moved the glEnableClientState outside of the loop like so: bool initGL(void) { //... glEnableClientState(GL_VERTEX_ARRAY); glEnableClientState(GL_TEXTURE_COORD_ARRAY); } void drawScene(void) { glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT); glBindTexture(GL_TEXTURE_2D, texturePointerA); glTexCoordPointer(2, GL_FLOAT, 0,textureCoordA); glVertexPointer(3, GL_FLOAT, 0, verticesA); glDrawElements(GL_QUADS, numPointsDrawnA, GL_UNSIGNED_BYTE, drawIndicesA); glBindTexture(GL_TEXTURE_2D, texturePointerB); glTexCoordPointer(2, GL_FLOAT, 0,textureCoordB); glVertexPointer(3, GL_FLOAT, 0, verticesB); glDrawElements(GL_QUADS, numPointsDrawnB, GL_UNSIGNED_BYTE, drawIndicesB); } It seems to work fine. My question is: Do I need to call glDisableClientState somewhere; perhaps when the program is closed?. Also, is it ok to do it like this? Is there something I'm missing since everyone else enables and disables each frame?

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Threadpool design question

- by ZeroVector

I have a design question. I want some feedback to know if a ThreadPool is appropriate for the client program I am writing. I am having a client running as a service processing database records. Each of these records contains connection information to external FTP sites [basically it is a queue of files to transfer]. A lot of them are to the same host, just moving different files. Therefore, I am grouping them together by host. I want to be able to create a new thread per host. I really don't care when the transfers finish, they just need to do all the work (or try to do) they were assigned, and then terminate once they are finished, cleaning up all resources they used in the process. I anticipate no more than 10-25 connections to be established. Once the transfer queue is empty, the program will simply wait until there are records in the queue again. Is the ThreadPool a good candidate for this or should I use a different approach? Edit: For the most part, this is the only significant custom application running on the server.

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Java Out of memory - Out of heap size

- by user1907849

I downloaded the sample program , for file transfer between the client and server. When I try running the program with 1 GB file , I get the Exception in thread "main" java.lang.OutOfMemoryError: Java heap space at Client.main(Client.java:31). Edit: Line no 31: byte [] mybytearray = new byte [FILE_SIZE]; public final static int FILE_SIZE = 1097742336; // receive file long startTime = System.nanoTime(); byte [] mybytearray = new byte [FILE_SIZE]; InputStream is = sock.getInputStream(); fos = new FileOutputStream(FILE_TO_RECEIVED); bos = new BufferedOutputStream(fos); bytesRead = is.read(mybytearray,0,mybytearray.length); current = bytesRead; do { bytesRead = is.read(mybytearray, current, (mybytearray.length-current)); if(bytesRead >= 0) current += bytesRead; } while(bytesRead > -1); bos.write(mybytearray, 0 , current); bos.flush(); Is there any fix for this?

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Populate table fields on query execution

- by Jason

I'm trying to build an ASP site that populates a Table based on the results of a selection in a ListBox. In order to do this, I've created a GridView table inside a div element. Currently the default behavior is to show all the items in the specified table in sortable order. However, I'd like to refine this further to allow for display of matches based on the results from the ListBox selection, but am not sure how to execute this. The ListBox fires off a OnSelectionChanged event to the method defined below and the GridView element is defined as <asp:GridView ID="dataListings" runat="server" AllowSorting="True" AutoGenerateColumns="False" DataSourceID="LinqDataSource1" OnDataBinding="ListBox1_SelectedIndexChanged"> protected void ListBox1_SelectedIndexChanged(object sender, EventArgs e) { int itemSelected = selectTopics.SelectedIndex; string[] listing = null; switch (itemSelected)//assign listing the array of course numbers { case 0: break; case 1: listing = arts; break; case 2: listing = currentEvents; break; .... More cases here default: listing = arts; break; } using (OLLIDBDataContext odb = new OLLIDBDataContext()) { var q = from c in odb.tbl_CoursesAndWorkshops where listing.Contains(c.tbl_Course_Description.tbl_CoursesAndWorkshops.course_workshop_number) select c; dataListings.DataSource = q; dataListings.DataBind(); } } However, this method never gets fired. I can see a request being made when changing the selection, but setting a breakpoint at the method declaration does nothing at all. Based on this, setup, I have three related questions What do I need to modify to get the OnSelectionChanged event handler to fire? How can I alter the GridView area to be empty on page load? How do I send the results from the dataListings.DataBind() execution to show in the GridView?

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The way cores, processes, and threads work exactly?

- by unknownthreat

I need a bit of an advice for understanding how this whole procedure work exactly. If I am incorrect in any part described below, please correct me. In a single core CPU, it runs each process in the OS, jumping around from one process to another to utilize the best of itself. A process can also have many threads, in which the CPU core runs through these threads when it is running on the respective process. Now, on a multiple core CPU, Do the cores run in every process together, or can the cores run separately in different processes at one particular point of time? For instance, you have program A running two threads, can a duo core CPU run both threads of this program? I think the answer should be yes if we are using something like OpenMP. But while the cores are running in this OpenMP-embedded process, can one of the core simply switch to other process? For programs that are created for single core, when running at 100%, why the CPU utilization of each core are distributed? (ex. A duo core CPU of 80% and 20%. The utilization percentage of all cores always add up to 100% for this case.) Do the cores try help each other run each thread of each process in some ways? Frankly, I'm not sure how this works exactly. Any advice is appreciated.

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Complex sorting on MySQL database

- by ChrisR

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When is a try catch not a try catch?

- by Dearmash

I have a fun issue where during application shutdown, try / catch blocks are being seemingly ignored in the stack. I don't have a working test project (yet due to deadline, otherwise I'd totally try to repro this), but consider the following code snippet. public static string RunAndPossiblyThrow(int index, bool doThrow) { try { return Run(index); } catch(ApplicationException e) { if(doThrow) throw; } return ""; } public static string Run(int index) { if(_store.Contains(index)) return _store[index]; throw new ApplicationException("index not found"); } public static string RunAndIgnoreThrow(int index) { try { return Run(index); } catch(ApplicationException e) { } return ""; } During runtime this pattern works famously. We get legacy support for code that relies on exceptions for program control (bad) and we get to move forward and slowly remove exceptions used for program control. However, when shutting down our UI, we see an exception thrown from "Run" even though "doThrow" is false for ALL current uses of "RunAndPossiblyThrow". I've even gone so far as to verify this by modifying code to look like "RunAndIgnoreThrow" and I'll still get a crash post UI shutdown. Mr. Eric Lippert, I read your blog daily, I'd sure love to hear it's some known bug and I'm not going crazy. EDIT This is multi-threaded, and I've verified all objects are not modified while being accessed

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How to compare two structure strings in C++

- by Arvandor

Ok, so this week in class we're working with arrays. I've got an assignment that wanted me to create a structure for an employee containing an employee ID, first name, last name, and wages. Then it has me ask users for input for 5 different employees all stored in an array of this structure, then ask them for a search field type, then a search value. Lastly, display all the information for all positive search results. I'm still new, so I'm sure it isn't a terribly elegant program, but what I'm trying to do now is figure out how to compare a user entered string with the string stored in the structure... I'll try to give all the pertinent code below. struct employee { int empid, string firstname, string lastname, float wage }; employee emparray[] = {}; employee value[] = {}; //Code for populating emparray and structure, then determine search field etc. cout << "Enter a search value: "; cin >> value.lastname; for(i = 0; i < 5; i++) { if(strcmp(value.lastname.c_str, emparray[i].lastname.c_str) == 0) { output(); } } Which... I thought would work, but it's giving me the following error.. Error 1 error C3867: 'std::basic_string<_Elem,_Traits,_Alloc>::c_str': function call missing argument list; use '&std::basic_string<_Elem,_Traits,_Alloc>::c_str' to create a pointer to member d:\myfile Any thoughts on what's going on? Is there a way to compare two .name notated strings without totally revamping the program? IF you want to drill me on best practices, please feel free, but also please try to solve my particular problem.

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