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  • Java Thread - Synchronization issue

    - by Yatendra Goel
    From Sun's tutorial: Synchronized methods enable a simple strategy for preventing thread interference and memory consistency errors: if an object is visible to more than one thread, all reads or writes to that object's variables are done through synchronized methods. (An important exception: final fields, which cannot be modified after the object is constructed, can be safely read through non-synchronized methods, once the object is constructed) This strategy is effective, but can present problems with liveness, as we'll see later in this lesson. Q1. Is the above statements mean that if an object of a class is going to be shared among multiple threads, then all instance methods of that class (except getters of final fields) should be made synchronized, since instance methods process instance variables?

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  • Does anyone else think instance variables are problematic in database-backed applications?

    - by Ben Aston
    It occurs to me that state control in languages like C# is not well supported. By this, I mean, it is left upto the programmer to manage the state of in-memory objects. A common use-case is that instance variables in the domain-model are copies of information residing in persistent storage (i.e. the database). Clearly this violates the single point of authority principle, and "synchronisation" has to be managed by the developer. I envisage a system where instead of instance variables, we have simple public access/mutator methods marked with attributes that link them to the database, and where reads and writes are mediated by a framework that decides whether to hit the database. Does such a system exist? Am I completely missing the point, or is there some truth to this idea?

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  • Shortest command to calculate the sum of a column of output on Unix?

    - by Andrew
    I'm sure there is a quick and easy way to calculate the sum of a column of values on Unix systems (using something like awk or xargs perhaps), but writing a shell script to parse the rows line by line is the only thing that comes to mind at the moment. For example, what's the simplest way to modify the command below to compute and display the total for the SEGSZ column (70300)? ipcs -mb | head -6 IPC status from /dev/kmem as of Mon Nov 17 08:58:17 2008 T ID KEY MODE OWNER GROUP SEGSZ Shared Memory: m 0 0x411c322e --rw-rw-rw- root root 348 m 1 0x4e0c0002 --rw-rw-rw- root root 61760 m 2 0x412013f5 --rw-rw-rw- root root 8192

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  • Maven easyb plugin java heap space settings?

    - by vinnu
    Hi, I attempted to change my heap size for maven easyb plugin http://www.easyb.org/maven-easyb-plugin/. In my easyb test I added standard code to print the heap size using the code Runtime.getFreeMemory() and Runtime.getTotalMemory(). I tried setting the MAVEN_OPTS=-Xmx1024m -Xms1024m and also set the maven opts in Maven surefire plugin. Now when I run the same class from the Junit I can see the getTotalMemory() displaying a number close 1Gig but the when the same classes are invoked from easyb plugin they do not reflect the memory size. Shouldn't there be a way of passing JVM opts to maven easyb plugin when it runs these easyb tests? At the very minimum it should atleast pick up the MAVEN_OPTS settings from the environment. Has someone bumped into problems like this? (A search on this group's archive does not reveal much)

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  • Codeigniter - Is it ok to add functionality to the constructor in controllers?

    - by Irro
    I'm making a project where I want the user to search for shops in different cities and would like the url to be like this: domain/shop/city/name. So I created a controller in codeigniter called Shop. But I cant create a city function since the city part of the url changes dependent on city name. One easy way to do it would be to add a function called "search" and add the functionality there but then I get url's like: domain/shop/search/city/name which I really would like to avoid. So my question is if it's ok to add my functionality directly into the constructor to avoid that extra "search" part in the url? I'm afraid that there might be some performance tricks involved that potentially keeps the class in memory so the constructor will not be called every time.

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  • Why is volatile not considered useful in multithreaded C or C++ programming?

    - by Michael E
    As demonstrated in this answer I recently posted, I seem to be confused about the utility (or lack thereof) of volatile in multi-threaded programming contexts. My understanding is this: any time a variable may be changed outside the flow of control of a piece of code accessing it, that variable should be declared to be volatile. Signal handlers, I/O registers, and variables modified by another thread all constitute such situations. So, if you have a global int foo, and foo is read by one thread and set atomically by another thread (probably using an appropriate machine instruction), the reading thread sees this situation in the same way it sees a variable tweaked by a signal handler or modified by an external hardware condition and thus foo should be declared volatile (or, for multithreaded situations, accessed with memory-fenced load, which is probably a better a solution). How and where am I wrong?

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  • reading specific lines from a file

    - by MacUsers
    What's the best way of reading only the specific lines (based on matching text) from a file? This is what I'm doing now: match_txt = "lhcb" for inFile in os.listdir('.'): readFile = open(inFile, 'r') lines = readFile.readlines() readFile.close() for line in lines: if line.find(match_txt)==0: #< do stuff here > i.e. I'm reading the lines, only with "lhcb" in it, from all the files in the present directory one by one. Is it the best way of doing that? Can it be done without loading the whole file in the memory in the first place?

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  • iphone - how to properly handle exceptional situations (signals ?)

    - by pmilosev
    Hi In my iphone app, I want to provide some sort of app termination handler that will do some final work (delete some sensitive data) before the application terminates. I want to handle as much of the termination situations as possible: 1) User terminates the app 2) The device runs out of battery 3) The system terminates the app due to some reason (e.g. out of memory or app freeze) 4) Application crashes (EXC_BAD_ACCESS or SIGSEGV) Any other exceptional situation ? What is the best way to achieve this (e.g. is applicationWillTerminate method called in situation 2) ? Is it possible to do the cleanup in a signal handler (includes iPhone Security framework calls) ? regards

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  • Performing regex on a stream

    - by takoi
    I have some large text files which im going to preform consecutive matching on (just capturing, not replacing). Im thinking its not such a good idea to keep the whole file in memory, but rather use a Reader. What i know about the input is that if there's a match, its not going to span more than 5 lines. So my idea was to have some sort of buffer which just keeps these 5 lines, or so, do the first search, and continue. But it has to "know" where the regex match ended for this to work. e.g if the match ends at line 2 it should start the next search from here. Is it possible to do something like this in an efficient way?

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  • How to Return A File and a strongly Typed data at the same time?

    - by chobo2
    Hi I am using asp.net mvc 1.0 and I want to return a XML file but I also want to return a strongly typed data back so I can update some fields. Like the XML file will contain users who failed to be inserted into the database. So I want that to appear as a dialog save box what asp.net mvc return file() would do. However I also want to return on the page like values like how many users failed to be added, how many users where added, etc. So I want to use scafolding with the class file I want to pass it along. If this was a view I could pass it along as an object model but I don't see a parameter for that in File(). I also don't want to save the xml file onto the harddrive I want to do it through memory. So have a link that would display on the page to download the file and show the the data I want would not be desired.

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  • Problems opening large csv file

    - by John Tyler
    I have a csv file that is 100mb in size. I need to parse some data out of it into a new format. I tried PHP, but keep running into memory issues. After around the first 150 "rows" or so, the script poops out. This is even on the localhost, and doing everything I can to tune the PHP settings, including max_memory and script_execution_time. Now before I continue, I'd like to know if Python will poop out on me too. Or if I will have to use C++. Can someone name good csv libraries for for these programmin langueage? The file is quoted csv. I mean scheiza I can't even open this text file in OpenOffice without it dying on me. (then again, Java sux as bad as PHP)

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  • C string program

    - by mrblippy
    Hi, i have been given a task to do ar school that must read three strings in, store the third string in dynamically allocated memory and print out the last 4 letters of the first word alphabetically. Here is the program i have so far but the strings are all stored in different variables, making them hard to sort. if anyone could give me a hand and help me finish this program i would be very grateful. thanks #include <stdio.h> #include <stdlib.h> #include <string.h> int main() { char word1[101]; char word2[101]; char* word3; char buffer[101]; scanf("%s", word1); scanf("%s", word2); scanf("%s", buffer); word3 = (char *) malloc(strlen(buffer)+1); strcpy(word3, buffer); return 0; }

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  • How do stream rows from a MSSQL table into a .NET app, in 10000 row chunks?

    - by Gravitas
    I have a table with 300 million rows in Microsoft SQL Server 2008 R2. There is a clustered index on the date column [DataDate] which means that the entire table is ordered by the date column. How do I stream out the data from this table, into my .NET application, in 10000 row chunks? Environment: Using C#. Have to be able to pause the data stream at any point, to allow the client to process the rows. Unfortunately, cannot use a select * from as this will select the entire table (its 50GB - it won't fit into memory).

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  • Bitmap.Save problems

    - by user284026
    Hello, can anyone tell me if you know to be a problem with Bitmap and steganography for WM 6? I am working on a project and i have to hide a digital signature in a bitmap. The algorithm works perfect, as in untill i have the image on the memory the bitmap contains the modified bytes. But after i save the image (Bitmap.Save()) and I reopen the image, than those bytes are lost. When i say lost i mean they are the orriginal bytes from when the picture was taken. Thank you.

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  • Way around ASP.NET session being shared across multiple tab windows

    - by ace
    I'm storing some value in an asp.net session on the first page. On the next page, this session value is being read. However if multiple tabs are opened and there are multiple page 1-page 2 navigation going on, the value stored in session gets mixed up since the session is shared between the browser tabs. I'm wondering what are the options around this : Query String: Passing value between the pages using query string, I don't want to take this approach since there can be multiple anchor tags on page 1 linking to page 2 and I can not rewrite the URLs of each tag since they are dynamic. Cookies??? In-memory cookies are shared across browser tabs too, same as the session cookie, rite ? Any other option?

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  • How can I disable Java garbage collector ?

    - by Nelson
    Hi, we have a PHP webapp that calls a java binary to produce a pdf report (with jasperreport), the java binary outpus pdf to standart output and exits, the php then send the pdf to browser. This java command lasts about 3 to 6 seconds, I think when it lasts 6 second it's because the GC kicks in, so I would like to disable it because anyway when the command exits all memory is returned.. I would like to know how to disable it for Java 1.4.2 and for Java 1.6.0 because we are currently testing both JVM to see which performs faster.. Thanks

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  • What's your development setup? (Talking right now to my boss)

    - by Flinkman
    How do I tell my boss, that I need endless cpu power to automate my daily job? By the way, what's your setup, now in sep, 2008. How fast disks? How much memory? How many cores? How big screen? (Ok, what the hell are you doing, you may ask. I'm working in multiple environments, vmware. Have couple of build-systems running, for compatibility tests. These build systems are automated. The setup of the build system is also. Is there an another way?) Thanks!

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  • Question regrarding declaring a property

    - by Simon
    Hi. We declare properties using the @property keyword and synthesize it in the implementation file. My question is, What if I declare a property using the @property keyword and also declare a variable in the interface block with the same name? For example, consider the following code, Interface: @interface myClass : NSObject { NSString *myClass_name; // LINE 1 } @property(nonatomic, retain) NSString *myClass_name; // LINE 2 @end Implementation: @implementation myClass @synthesize myClass_name @end Declaring myClass_name in LINE 1 will make any problem? Like any reference problem or any unnecessary memory consumption problem?

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  • Image gets slightly erased on SWT/Windows

    - by zvikico
    I have an Eclipse plugin which includes a view. The view has several icons in the toolbar. I'm experiencing a very strange problem: on Windows, in some occasions (after prolonged use), one of the icons gets slightly erased. This does not happen on other platforms. This looks like a memory leak or some other resource misuse, but I just can't figure out where. The rest of the icons, which are initialized and used in the exact same manner are not affected. I tried working with Sleak, but I really don't see anything out of the ordinary. Any help would be appreciated.

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  • iPhone xcode array losing state after load

    - by Frames84
    Right i've had a search around and can't find anything. @synthesize list; // this is an NSArry -(void) viewDidLoad { NSArray *arr = [self getJSONFeed]; self.List = [arr retain]; // if i copy the access code into here it works fine. } -(void) tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { NSUInteger row = [indexPath row]; NSArray *vals = [list objectAtIndex:row] retain]; NSString *id = [vals valueForKey:@"id"]; // ERROR } right i've taken some of the code to try and provide it as simple as possible, ignore typo's and memory leaks this is sorted. Basically when I select a row I can't get data out of my 'list' array object. Please can anyone help me out?

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  • How to check if a process is running or got segfaulted or terminated in linux from its pid in my mai

    - by rkbang
    Hello all, I am invoking several processes in my main and I can get the pid of that processes. Now I want to wait until all this processes have been finished and then clear the shared memory block from my parent process. Also if any of the process not finished and segfaulted I want to kill that process. So how to check from the pid of processes in my parent process code that a process is finished without any error or it gave broke down becoz of runtime error or any other cause, so that I can kill that process. Also what if I want to see the status of some other process which is not a child process but its pid is known. Code is appreciated( I am not looking for script but code ).

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  • How do I bind a key to "the function represented by the following key sequence"?

    - by katrielalex
    I'm just starting to learn emacs (woohoo!) and I've been mucking around in my .emacs quite happily. Unfortunately, I don't know Lisp yet, so I'm having issues with the basics. I've already remapped a few keys until I fix my muscle memory: (global-set-key (kbd "<f9>") 'recompile) That's fine. But how can I tell a key to 'simulate pressing several keys'? For instance, I don't know, make <f1> do the same as C-u 2 C-x } (widen buffer by two chars). One way is to look up that C-x } calls shrink-window-horizontally, and do some sort of lambda thing. This is of course the neat and elegant way (how do you do this?). But surely there's a way to define <f1> to send the keystrokes C-u 2 C-x }?

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  • Linq To Sql Entity Updated from Trigger

    - by James Helms
    I have a Table called Address. I have a Trigger for insert on that table that does some spacial calculations on the address that determines what neighborhood boundaries it is in. address = new Address { Street = this.Street, City = this.City, State = this.State, ZipCode = this.ZipCode, latitude = this.Latitude, longitude = this.Longitude, YearBuilt = this.YearBuilt, LotSize = this.LotSize, FinishedSize = this.FinishedSize, Bedrooms = this.Bedrooms, Bathrooms = this.Bathrooms, UseCode = this.UseCode, HOA = this.HOA, UpdateDate = DateTime.Now }; db.AddToAddresses(address); db.SaveChanges(); In the database i can clearly see that the Trigger ran and updated the neighborhoodID in the address table for the row. I tried to just reload that record to get the assigned id like this: address = (from a in db.Addresses where a.AddressID == address.AddressID select a).First(); In the debugger i can clearly see that the address.AddressID is correct, entity doesn't update in memory. Is there any work around for this?

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  • delete & new in c++

    - by singh
    Hi This may be very simple question,But please help me. i wanted to know what exactly happens when i call new & delete , For example in below code char * ptr=new char [10]; delete [] ptr; call to new returns me memory address. Does it allocate exact 10 bytes on heap, Where information about size is stored.When i call delete on same pointer,i see in debugger that there are a lot of byte get changed before and after the 10 Bytes. Is there any header for each new which contain information about number of byte allocated by new. Thanks a lot

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  • What is the correct way of handling a reloaded view after it was dismissed?

    - by favo
    Hi, I have the same problem as the guy here: http://stackoverflow.com/questions/2682844/uiimagepickercontroller-reloads-view-after-its-dismissed I have a UIView with a UIDatePicker within a Popover. When the Popover is dismissed and presented again, it sometimes resets the Picker in the view because hidden views are unloaded when a memory warning occurs. This is the part displaying the view: endCompareDateTimePicker.picker.maximumDate = [NSDate dateWithTimeIntervalSinceNow:0]; [endCompareDateTimePopover presentPopoverFromRect:sender.frame inView:self.view permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES]; The picker (IBOutlet UIDatePicker) does not stay initiated. Adding a [endCompareDateTimePicker loadView] helped out and got me the picker initiated to set the correct date values before displaying the view. While this is working, I dont think this is the proper way doing this. What would be the correct way to handle this situation?

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