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  • Beginner assembly programming memory usage question

    - by Daniel
    I've been getting into some assembly lately and its fun as it challenges everything i have learned. I was wondering if i could ask a few questions When running an executable, does the entire executable get loaded into memory? From a bit of fiddling i've found that constants aren't really constants? Is it just a compiler thing? const int i = 5; _asm { mov i, 0 } // i is now 0 and compiles fine So are all variables assigned with a constant value embedded into the file as well? Meaning: int a = 1; const int b = 2; void something() { const int c = 3; int d = 4; } Will i find all of these variables embedded in the file (in a hex editor or something)? If the executable is loaded into memory then "constants" are technically using memory? I've read around on the net people saying that constants don't use memory, is this true?

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  • Python: Does one of these examples waste more memory?

    - by orokusaki
    In a Django view function which uses manual transaction committing, I have: context = RequestContext(request, data) transaction.commit() return render_to_response('basic.html', data, context) # Returns a Django ``HttpResponse`` object which is similar to a dictionary. I think it is a better idea to do this: context = RequestContext(request, data) response = render_to_response('basic.html', data, context) transaction.commit() return response If the page isn't rendered correctly in the second version, the transaction is rolled back. This seems like the logical way of doing it albeit there won't likely be many exceptions at that point in the function when the application is in production. But... I fear that this might cost more and this will be replete through a number of functions since the application is heavy with custom transaction handling, so now is the time to figure out. If the HttpResponse instance is in memory already (at the point of render_to_response()), then what does another reference cost? When the function ends, doesn't the reference (response variable) go away so that when Django is done converting the HttpResponse into a string for output Python can immediately garbage collect it? Is there any reason I would want to use the first version (other than "It's 1 less line of code.")?

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  • Explanation of `self` usage during dealloc?

    - by Greg
    I'm trying to lock down my understanding of proper memory management within Objective-C. I've gotten into the habit of explicitly declaring self.myProperty rather than just myProperty because I was encountering occasional scenarios where a property would not be set to the reference that I intended. Now, I'm reading Apple documentation on releasing IBOutlets, and they say that all outlets should be set to nil during dealloc. So, I put this in place as follows and experienced crashes as a result: - (void)dealloc { [self.dataModel close]; [self.dataModel release], self.dataModel = nil; [super dealloc]; } So, I tried taking out the "self" references, like so: - (void)dealloc { [dataModel close]; [dataModel release], dataModel = nil; [super dealloc]; } This second system seems to work as expected. However, it has me a bit confused. Why would self cause a crash in that case, when I thought self was a fairly benign reference more used as a formality than anything else? Also, if self is not appropriate in this case, then I have to ask: when should you include self references, and when should you not?

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  • efficient android rendering

    - by llll
    I've read quite a few tutorials on game programming on android, and all of them provide basically the same solution as to drawing the game, that is having a dedicated thread spinning like this: public void run() { while(true) { if(!surfaceHolder.getSurface().isValid()) continue; Canvas canvas = surfaceHolder.lockCanvas(); drawGame(canvas); /* do actual drawing here */ surfaceHolder.unlockCanvasAndPost(canvas); } } now I'm wondering, isn't this wasteful? Suppose I've a game with very simple graphics, so that the actual time in drawGame is little; then I'm going to draw the same things on and on, stealing cpu from the other threads; a possibility could be skipping the drawing and sleeping a bit if the game state hasn't changed, which I could check by having the state update thread mantaining a suitable status flag. But maybe there are other options. For example, couldn'it be possible to synchronize with rendering, so that I don't post updates too often? Or am I missing something and that is precisely what lockCanvas does, that is it blocks and burns no cpu until proper time? Thanks in advance L.

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  • C/C++ usage of special CPU features

    - by b-gen-jack-o-neill
    Hi, I am curious, do new compilers use some extra features built into new CPUs such as MMX SSE,3DNow! and so? I mean, in original 8086 there was even no FPU, so compiler that old cannot even use it, but new compilers can, since FPU is part of every new CPU. So, does new compilers use new features of CPU? Or, it should be more right to ask, does new C/C++ standart library functions use new features? Thanks for answer.

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  • What really is the purpose of "base" keyword in c#?

    - by Pandiya Chendur
    Thus for used base class for some commom reusable methods in every page of my application... public class BaseClass:System.Web.UI.Page { public string GetRandomPasswordUsingGUID(int length) { string guidResult = System.Guid.NewGuid().ToString(); guidResult = guidResult.Replace("-", string.Empty); return guidResult.Substring(0, length); } } So if i want to use this method i would just do, public partial class forms_age_group : BaseClass { protected void Page_Load(object sender, EventArgs e) { //i would just call it like this string pass = GetRandomPasswordUsingGUID(10); } } It does what i want but there is a "Base" keyword that deals with base class in c# ... I really want to know when should use base keyword in my derived class.... Any good example...

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  • what exactly does system.totalMemory test in Actionscript 3.0?

    - by vasion
    before somebody screaming RTFM, let me clarify. does system.totalMemory test the memory used in movie which invokes it, or used by all movies running on the browser/system? I want to initiate garbage collaction for my app when it reaches a certain limit and i dont want the process to be initialized by the user watching funny cats youtube video.

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  • Usage of autorelease pools for fetch method

    - by Matthias
    Hi, I'm a little bit confused regarding the autorelease pools when programming for the iPhone. I've read a lot and the oppionions seem to me from "Do-NOT-use" to "No problem to use". My specific problem is, I would like to have a class which encapsulates the SQLite3 Access, so I have for example the following method: -(User*)fetchUserWithId:(NSInteger)userId Now, within this method a SQL query is done and a new user object is created with the data from the database and then returned. Within this DB Access class I don't need this object anymore, so I can do a release, but since the calling method needs it, I would do an autorelease, wouldn't I? So, is it okay to use autorelease here oder would it gain too much memory, if this method is called quite frequently? Some websites say, that the autorelease pool is released first at the end of the application, some say, at every event (e.g. user touches something). If I should not use autorelease, how can I make sure, that the object is released correctly? Can I do a release in the fetch method and hope, that the object is still there until the calling method can do a retain? Thanks for your help! Regards Matthias

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  • What percent of web sites use JavaScript?

    - by Claudiu
    I'm wondering just how pervasive JavaScript is. This article states that 73% of websites they tested rely on JavaScript for important functionality, but it seems to me that the number must be larger. Have any surveys been done on this topic? Maybe a better way to phrase this question is - are there any sites that don't use JavaScript? EDIT: By 'use', I don't necessarily mean "rely on for important functionality" - that was just the statistic that one article gave.

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  • not null usage in mysql

    - by pradeep
    Hi, I use syntax like name varchar(20) NOT NULL in mysql..i have a big confusion over here. typically does it mean that this field is mandatory? but when i store a space in this field it accepts it.is it correct. its like while insert i say '".$_POST['name']."'. even if the name does not have any value query is executed. can any1 just clarify me on this ? is NULL and blank space same ?

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  • The best alternative for String flyweight implementation in Java

    - by Dan
    My application is multithreaded with intensive String processing. We are experiencing excessive memory consumption and profiling has demonstrated that this is due to String data. I think that memory consumption would benefit greatly from using some kind of flyweight pattern implementation or even cache (I know for sure that Strings are often duplicated, although I don't have any hard data in that regard). I have looked at Java Constant Pool and String.intern, but it seems that it can provoke some PermGen problems. What would be the best alternative for implementing application-wide, multithreaded pool of Strings in java?

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  • Usage of atoi in the c language

    - by maddy
    I don't understand the results of the following C code. main() { char s[] = "AAA"; advanceString(s); } void advanceString(p[3]) { int val = atoi(p); printf("The atoi val is %d\n",val); } Here the atoi val is shown as 0. But I could not figure out the exact reason. As per my understanding, it should be the summation of decimal equivalent of each values in the array.? Please correct me if I am wrong.

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  • What is the best way to find a processed memory allocations in terms of C# objects

    - by Shantaram
    I have written various C# console based applications, some of them long running some not, which can over time have a large memory foot print. When looking at the windows perofrmance monitor via the task manager, the same question keeps cropping up in my mind; how do I get a break down of the number objects by type that are contributing to this footprint; and which of those are f-reachable and those which aren't and hence can be collected. On numerous occasions I've performed a code inspection to ensure that I am not unnecessarily holding on objects longer than required and disposing of objects with the using construct. I have also recently looked at employing the CG.Collect method when I have released a large number of objects (for example held in a collection which has just been cleared). However, I am not so sure that this made that much difference, so I threw that code away. I am guessing that there are tools in sysinternals suite than can help to resolve these memory type quiestions but I am not sure which and how to use them. The alternative would be to pay for a third party profiling tool such as JetBrains dotTrace; but I need to make sure that I've explored the free options first before going cap in hand to my manager.

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  • in java, which is better - three arrays of booleans or 1 array of bytes?

    - by joe_shmoe
    I know the question sounds silly, but consider this: I have an array of items and a labelling algorithm. at any point the item is in one of three states. The current version holds these states in a byte array, where 0, 1 and 2 represent the three states. alternatively, I could have three arrays of boolean - one for each state. which is better (consumes less memory) depends on how jvm (sun's version) stores the arrays - is a boolean represented by 1 bit? (p.s. don't start with all that "this is not the way OO/Java works" - I know, but here performance comes in front. plus the algorithm is simple and perfectly readable even in such form). Thanks a lot

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  • Replacement for java.util.zip for streaming usage?

    - by evilfred
    java.util.zip sucks for stream compression. The longer you leave an Inflator/Deflator open without calling end(), the more native memory it uses up. This is a known issue: http://bugs.sun.com/view_bug.do?bug_id=4797189 which nobody seems to care about fixing. What is a good alternative? Preferably one that is free and is still actively supported by its developers.

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  • mysql stored funtion usage

    - by shikhar
    I just wrote a stored function to calculate the working days between two dates. This works select CountWeekDays('2010-03-07','2010-04-07') This doesn't work select CountWeekDays(o.order_date,o.created_date) from orders o; Any idea how to make this one work ?? function definition delimiter $$; CREATE FUNCTION CountWeekDays (sdate VARCHAR(50), edate VARCHAR(50)) RETURNS INT BEGIN DECLARE wdays, tdiff, counter, thisday smallint; DECLARE newdate DATE; SET newdate := sdate; SET wdays = 0; if DATEDIFF(edate, sdate) = 0 THEN RETURN 1; END IF; if DATEDIFF(edate, sdate) < 0 THEN RETURN 0; END IF; label1: LOOP SET thisday = DAYOFWEEK(newdate); IF thisday BETWEEN 2 AND 6 THEN SET wdays := wdays + 1; END IF; SET newdate = DATE_ADD(newdate, INTERVAL 1 DAY); IF DATEDIFF(edate, newdate) < 0 THEN LEAVE label1; END IF; END LOOP label1; RETURN wdays; END

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  • JVM cannot use 8 CPUon Linux

    - by Trustin
    I have observed that JVM cannot user 8 CPU advantage. Because when a thread runs more than 1 secs, other threds are waiting for it. there is no lock beetween these threds is there any jvm option for this ?

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  • SPSS - sum of squares change radically with slight model changes in ANOVA??

    - by Pat
    I have noticed that the sum of squares in my models can change fairly radically with even the slightest adjustment to my models???? Is this normal???? I'm using SPSS 16, and both models presented below used the same data and variables with only one small change - categorizing one of the variables as either a 2 level or 3 level variable. Details - using a 2 x 2 x 6 mixed model ANOVA with the 6 being the repeated measure i get the following in the between group analysis ------------------------------------------------------------ Source | Type III SS | df | MS | F | Sig ------------------------------------------------------------ intercept | 4086.46 | 1 | 4086.46 | 104.93 | .000 X | 224.61 | 1 | 224.61 | 5.77 | .019 Y | 2.60 | 1 | 2.60 | .07 | .80 X by Y | 19.25 | 1 | 19.25 | .49 | .49 Error | 2570.40 | 66 | 38.95 | Then, when I use the exact same data but a slightly different model in which variable Y has 3 levels instead of 2 levels I get the following ------------------------------------------------------------ Source | Type III SS | df | MS | F | Sig ------------------------------------------------------------ intercept | 3603.88 | 1 | 3603.88 | 90.89 | .000 X | 171.89 | 1 | 171.89 | 4.34 | .041 Y | 19.23 | 2 | 9.62 | .24 | .79 X by Y | 17.90 | 2 | 17.90 | .80 | .80 Error | 2537.76 | 64 | 39.65 | I don't understand why variable X would have a different sum of squares simply because variable Y gets devided up into 3 levels instead of 2. This is also the case in the within groups analysis too. Please help me understand :D Thank you in advance Pat

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  • Boost any usage

    - by Ockonal
    Hello, how can I insert my own class objects into ptr_map from boost. The objects are templated so I can't use some static typename in the map. So I did: ptr_map<string, any> someMap; My class inherits the boost::noncopyable. someMap.insert("Test", new MyClass()); The error is: error: no matching function for call to ‘boost::ptr_map.

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  • usage of 2 charectors in single qoutes in c

    - by user1632141
    #include<stdio.h> int main() { char ch = 'A'; printf("%d\n",'ag'); printf("%d\n",'a'); printf("%d, %d, %d, %d", sizeof(ch), sizeof('a'), sizeof('Ag'), sizeof(3.14f)); return 0; } I used to have many doubts on the output of this question while running on g++ and gcc. But I have cleared almost all the doubts by referring these links: Single and double quotes in C/C++ Single quotes vs. double quotes in C I still need to understand one thing about the output of this question. Can someone please explain the output of printf("%d\n",'ag'); mentioned above in the program. How is it actually stored in the memory? The output for the program on the Linux/GCC platform is: 24935 97 1, 4, 4, 4

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  • Limit CPU usage of a process

    - by jb
    I have a service running which periodically checks a folder for a file and then processes it. (Reads it, extracts the data, stores it in sql) So I ran it on a test box and it took a little longer thaan expected. The file had 1.6 million rows, and it was still running after 6 hours (then I went home). The problem is the box it is running on is now absolutely crippled - remote desktop was timing out so I cant even get on it to stop the process, or attach a debugger to see how far through etc. It's solidly using 90%+ CPU, and all other running services or apps are suffering. The code is (from memory, may not compile): List<ItemDTO> items = new List<ItemDTO>(); using (StreamReader sr = fileInfo.OpenText()) { while (!sr.EndOfFile) { string line = sr.ReadLine() try { string s = line.Substring(0,8); double y = Double.Parse(line.Substring(8,7)); //If the item isnt already in the collection, add it. if (items.Find(delegate(ItemDTO i) { return (i.Item == s); }) == null) items.Add(new ItemDTO(s,y)); } catch { /*Crash*/ } } return items; } - So I am working on improving the code (any tips appreciated). But it still could be a slow affair, which is fine, I've no problems with it taking a long time as long as its not killing my server. So what I want from you fine people is: 1) Is my code hideously un-optimized? 2) Can I limit the amount of CPU my code block may use? Cheers all

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