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  • Does a servlet-based stack have significant overheads?

    - by John
    I don't know if it's simply because page-loads take a little time, or the way servlets have an abstraction framework above the 'bare metal' of HTTP, or just because of the "Enterprise" in Jave-EE, but in my head I have the notion that a servlet-based app is inherently adding overhead compared to a Java app which simply deals with sockets directly. Forget web-pages, imagine instead a Java server app where you send it a question over an HTTP request and it looks up an answer from memory and returns the answer in the response. You can easily write a Java socket-based app which does this, you can also do a servlet approach and get away from the "bare metal" of sockets. Is there any measurable performance impact to be expected implementing the same approach using Servlets rather than a custom socket-based HTTP listening app? And yes, I am hazy on the exact data sent in HTTP requests and I know it's a vague question. It's really about whether servlet implementations have lots of layers of indirection or anything else that would add up to a significant overhead per call, where by significant I mean maybe an additional 0.1s or more.

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  • Reason for different segments in Linux on x86

    - by anjruu
    Hey all, So, I know that Linux uses four default segments for an x86 processor (kernel code, kernel data, user code, user data), but they all have the same base and limit (0x00000000 and 0xfffff), meaning each segment maps to the same set of linear addresses. Given this, why even have user/kernel segments? I understand why there should be separate segments for code and data (just due to how the x86 processor deals with the cs and ds registers), but why not have a single code segment and a single data segment? Memory protection is done through paging, and the user and kernel segments map to the same linear addresses anyway. Thanks! anjruu

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  • Android app crashes on second run

    - by Nick
    I have been working on my app and it runs on the simulator fine. I loaded it into my phone and now I have a problem. It runs fine when I first start it and also if I pick home and then restart it; however, if I use the back arrow and then restart it it crashes on that time, but will work out the next time I start it. I think it has to do with some kind of memory build up, but I verified onDestroy is being called, I figured that deletes everything my program created, right?

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  • In Perl, can I limit the length of a line as I read it in from a file (like fgets)

    - by SB
    I'm trying to write a piece of code that reads a file line by line and stores each line, up to a certain amount of input data. I want to guard against the end-user being evil and putting something like a gig of data on one line in addition to guarding against sucking in an abnormally large file. Doing $str = <FILE> will still read in a whole line, and that could be very long and blow up my memory. fgets lets me do this by letting me specify a number of bytes to read during each call and essentially letting me split one long line into my max length. Is there a similar way to do this in perl? I saw something about sv_gets but am not sure how to use it (though I only did a cursory Google search). Thanks.

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  • merge three file into one big file

    - by davit-datuashvili
    suppose that we have three array int a[]=new int[]{4,6,8,9,11,12}; int b[]=new int[]{3,5,7,13,14}; int c[]=new int[]{1,2,15,16,17}; and we want to merge it into one big d array where d.length=a.length+b.length+c.length but we have memory problem it means that we must need use only this d array where we should merge these these three array of course we can use merge sort but can we use merge algorithm without sorting method? like two sorted array we can merge in one sorted array what about three or more array?

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  • PHP find if file data is an image

    - by Christian Sciberras
    Imagine I have some file data in a variable $data. I need to determine whether it is an image or not. No need for details such as corrupt images etc. Firs thought would be getting the file mime type by looking at the magic number and then see whether "image" is in the mime type. No such luck, even if I have a "file extension to mime type" script, I don't have a reliable way to get mime from magic number. My next option was to have a reasonable list of image file magic numbers and consult them. However, it relatively difficult to find such magic numbers (gif for instance has different magic numbers, some of which could pretty rare - if memory serves me right). A better idea would be some linux program which can do this kind of thing. Any ideas? I'm running RHEL and PHP 5.3. I've got root access - ie able to install stuff if needed. - Chris.

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  • What is the result of "new int[ 0 ]"? [closed]

    - by ArunSaha
    Possible Duplicates: What does zero-sized array allocation do/mean? C++ new int[0] — will it allocate memory? int * p; p = new int[ 0 ]; What is the expected outcome when new is called for zero number of elements? Is the outcome defined or undefined? Further, is it okay to call delete [] p; on that pointer? What is the intuition/analogy to this situation of pointer to an array of zero elements? Thanks in advance. Regards, Arun

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  • Why does C++ linking use virtually no CPU? (updated)

    - by John
    On a native C++ project, linking right now can take a minute or two, yet during this time CPU drops from 100% during compilation to virtually zero. Does this mean linking is primarily a disk activity? If so, is this the main area an SSD would make big changes? But, why aren't all my OBJ files (or as many as possible) kept in RAM after compilation to avoid this? With 4Gb of RAM I should be able to save a lot of disk access and make it CPU-bound again, no? update: so the obvious follow-up is, can VC++ compiler and linker talk together better to streamline things and keep OBJ files in memory, similar to how Delphi does?

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  • C# array problem

    - by user208080
    Hi there. I am a newbie in C# and here are 2 questions: I have a 2d array a[3,3], how can I express one dimension as a new array and pass to some function. i.e. int[,] a = new int[3,3]; a[0,0] = 1; ... string b = concatenate(a[0]); // where concatenate is a function take a one dimension array as param Can I create a 65000x65000 array with C#? I got some "out of memory" error. Thanks in advance.

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  • Find node level in a tree

    - by Álvaro G. Vicario
    I have a tree (nested categories) stored as follows: CREATE TABLE `category` ( `category_id` int(10) unsigned NOT NULL AUTO_INCREMENT, `category_name` varchar(100) NOT NULL, `parent_id` int(10) unsigned DEFAULT NULL, PRIMARY KEY (`category_id`), UNIQUE KEY `category_name_UNIQUE` (`category_name`,`parent_id`), KEY `fk_category_category1` (`parent_id`,`category_id`), CONSTRAINT `fk_category_category1` FOREIGN KEY (`parent_id`) REFERENCES `category` (`category_id`) ON DELETE SET NULL ON UPDATE CASCADE ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_spanish_ci I need to feed my client-side language (PHP) with node information (child+parent) so it can build the tree in memory. I can tweak my PHP code but I think the operation would be way simpler if I could just retrieve the rows in such an order that all parents come before their children. I could do that if I knew the level for each node: SELECT category_id, category_name, parent_id FROM category ORDER BY level -- No `level` column so far :( Can you think of a way (view, stored routine or whatever...) to calculate the node level? I guess it's okay if it's not real-time and I need to recalculate it on node modification.

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  • Response Time is different for mulitiple execution of the application with the same request Performa

    - by sivananda
    My java application functionality is to provide reference data (basically loads lots of data from xml files into hashmap) and hence we request for one such data from the hashmap based on a id and we have such multiple has map for different set of business data. The problem is that when i tried executing the java application for the same request multiple times, the response times are different like 31ms, 48ms, 72ms, 120ms, 63ms etc. hence there is a considerable gap between the min and max time taken for the execution to complete. Ideally, i would expect the response times to be like, 63ms, 65ms, 61ms, 70ms, 61ms, but in my case the variation of the response time for the same request is varying hugely. I had used a opensource profile to understand if there is any extra execution of the methods or memory leak, but as per my understanding there was no problem. Please let me know what could be the reasons and how can i address this problem.

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  • What happens if an asynchronous delegate call never returns?

    - by RichardHowells
    I found a decent looking example of how to call a delegate asynchronously with a timeout... http://www.eggheadcafe.com/tutorials/aspnet/847c94bf-4b8d-4a66-9ae5-5b61f049019f/basics-make-any-method-c.aspx. In summary it uses WaitOne with a timeout to determine if the call does not return before the timeout expires. I also know that you should have an EndInvoke to match each BeginInvoke. So what happens if the wait timeout expires? We (presumably) DON'T want to call EndInvoke as that will block. The code can go on to do 'other things', but have we leaked anything? Is there some poor thread someplace blocked waiting for a return that's never going to happen? Have we leaked some memory where the result-that-will-never-return was going to be placed?

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  • How to run stored procedure 1000 times

    - by subt13
    I have a stored procedure that I'm using to populate a table with about 60 columns. I have genereated 1000 exec statements that look like this: exec PopulateCVCSTAdvancement 174, 213, 1, 0, 7365 exec PopulateCVCSTAdvancement 174, 214, 1, 0, 7365 exec PopulateCVCSTAdvancement 175, 213, 0, 0, 7365 Each time the stored procedure will be inserting anywhere from 1 to 3,000 records (usually around 2,000 records). The "server" is running desktop hardware with 4 gigs of available memory on a server OS. The problem I have is that after the first 10-15 executes of an average of 1-2 seconds each time, the next 10-15 seem to never finish. Am I doing this correctly? How should I do this? Thanks! Top 10 waiters: LAZYWRITER_SLEEP SQLTRACE_INCREMENTAL_FLUSH_SLEEP REQUEST_FOR_DEADLOCK_SEARCH XE_TIMER_EVENT FT_IFTS_SCHEDULER_IDLE_WAIT CHECKPOINT_QUEUE LOGMGR_QUEUE SLEEP_TASK BROKER_TO_FLUSH BROKER_TASK_STOP

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  • Speed of running a test suite in Rails

    - by Milan Novota
    I have 357 tests (534 assertions) for my app (using Shoulda). The whole test suite runs in around 80 seconds. Is this time OK? I'm just curious, since this is one of my first apps where I write tests extensively. No fancy stuff in my app. Btw.: I tried to use in memory sqlite3 database, but the results were surprisingly worse (around 83 seconds). Any clues here? I'm using Macbook with 2GB of RAM and 2GHz Intel Core Duo processor as my development machine.

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  • C++ MFC how to compare LPCTSTR in a if statement?

    - by user1078510
    I have the following code: LPCTSTR strPermission = Method(); if (strPermission == L"0") { return true; } else { return false; } While debugging I can see that strPermission does equal "0", yet when I compare it like in the if statement it always returns false. The only thing I can think of is that it is comparing the memory address of the variable rather than the variable value. How do I compare strPermission to L"0" so that it would return true if strPermission equals "0". Thank you!

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  • Returning the address of local or temporary variable

    - by Dave18
    #include <iostream> int& foo() { int i = 6; std::cout << &i << std::endl; return i; } int main() { int i = foo(); std::cout << &i << std::endl; } I know it doesn't return the address of local variable so that is why the warning but why does it still works and assign the variable i in main() to '6'? How does it only return the value if the variable the was removed from stack memory?

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  • I want to make my own Malloc

    - by Unknown
    I want to make my own malloc/free so I can make a precise copying allocator. Any gurus have any tips and suggestions? I have a few questions for now: Should I just malloc large chunks of memory, and then distribute from that so I don't have to call the system calls? How are copying collectors usually done? I would imagine that this part is a bit complicated to do efficiently. My naive implementation would just malloc a block the size of the remaining objects which would require 2x the space.

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  • Does the Internet make us less good programmers? [closed]

    - by stagas
    With all the information and code available nowadays on the Internet has that diminished our capability of remembering or learning stuff just because we know they're available somewhere out there, just a Google away or a StackOverflow question away? For example I find myself visiting php.net quite often to check the syntax of the same functions over and over again, not because my memory sucks, but I don't feel like keeping the information in me, since I know I'll find it again on the net. And about StackOverflow, isn't the process of figuring things out on your own supposed to improve your programming skills? If the answers are all just clicks away, do we actually learn something or just keep a pointer in our heads where to search for it again when we need it? Your thoughts are welcome. Hope it doesn't shut down as subjective or anything, the answers would be really interesting ;)

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  • Efficient questions

    - by rayman
    Hi, I have to manage xml's and Strings in my app. by efficenty and memory saving, is collection(ArrayList) will be much more 'expensive' then array of Strings? another issue is: i could use the content as regular String, or XML.. is working with XML also makes it more 'expensive' ? when i say i expensive i talk about taking system sources. please tell me by any of your exprience if the diffrences are significant? thanks, ray.

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  • C# how to store those information?

    - by 5YrsLaterDBA
    I have a PrivilegeGroup table, a Privileges table and a link table because the PrivilegeGroup table and the Privileges table is a many to many relationship. I am thinking about load all contents of PrivilegeGroup table and Privilege table into memory from database at beginning when application started. I want to save them in a form easily to look up. Usually we will look up the PrivilegeCode via GroupId. Which structure is good for this purpose? array of list? dictionary?

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  • C/C++ function definitions without assembly

    - by Jack
    Hi, I always thought that functions like printf() are in the last step defined using inline assembly. That deep into stdio.h is burried some asm code that actually tells CPU what to do. Something like in dos, first mov bagining of the string to some memory location or register and than call some int. But since x64 version of Visual Studio doesent support inline assembler at all, it made me think that there are really no assembler-defined functions in C/C++. So, please, how is for example printf() defined in C/C++ without using assembler code? What actually executes the right software interrupt? Thanks.

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  • Good way to send a large file over a network in C#?

    - by BFreeman
    I am trying to build an application that can request files from a service running on another machine in the network. These files can be fairly large (500mb + at times). I was looking into sending it via TCP but I'm worried that it may require that the entire file be stored in memory. There will probably only be one client. Copying to a shared directory isn't acceptable either. The only communication required is for the client to say "gimme xyz" and the server to send it (and whatever it takes to ensure this happens correctly). Any suggestions?

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  • Using temporary arrays to cut down on code - inefficient?

    - by tommaisey
    I'm new to c++ (and SO) so sorry if this is obvious. I've started using temporary arrays in my code to cut down on repetition and to make it easier to do the same thing to multiple objects. So instead of: MyObject obj1, obj2, obj3, obj4; obj1.doSomming(arg); obj2.doSomming(arg); obj3.doSomming(arg); obj4.doSomming(arg); I'm doing: MyObject obj1, obj2, obj3, obj4; MyObject* objs[] = {&obj1, &obj2, &obj3, &obj4}; for (int i = 0; i !=4; ++i) objs[i]->doSomming(arg); Is this detrimental to performance? Like, does it cause unnecessary memory allocation? Is it good practice? Thanks.

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  • Forcing an app to run single core only?

    - by Kevin
    I have this strange issue with some third party DLL's. The third party provider references some open source DLL's that have a memory exception whenever I try to use a certain method. This issue does not appear when the app is run on a single core machine, but obviously we cannot assume a user will have that. Is there a way to force an app, or even better yet a referenced DLL to run on a single core? Any other way to possibly fix this? Getting the third party to rebuild the OS dll's is apparently out of the question (its a bit of a sore spot with me currently :) ) so I have to handle it myself or just forget about providing this functionality.

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  • C# thread safety for class instances

    - by Steveng
    I am learning C# and I am confused with the thread safety of the copies of the class instances as below: eg: classA objA; classA objB = objA; objA.field1 = value2; //do I need lock around modification of field1? //let say we pass the objB to another thread objB.field1 = value1 //do I need a lock for objB because of the modification of field1? I am confused because coming from the background of C++, the class in C# is the reference type. If both objA and objB refer to the same memory underlying, then I would need a lock to protect the simultaneous writing to the field1. Could someone confirm with this or am I missing something? Thanks.

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