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  • PostGres - run a query in batches?

    - by CaffeineIV
    Is it possible to loop through a query so that if (for example) 500,000 rows are found, it'll return results for the first 10,000 and then rerun the query again? So, what I want to do is run a query and build an array, like this: $result = pg_query("SELECT * FROM myTable"); $i = 0; while($row = pg_fetch_array($result) ) { $myArray[$i]['id'] = $row['id']; $myArray[$i]['name'] = $row['name']; $i++; } But, I know that there will be several hundred thousand rows, so I wanted to do it in batches of like 10,000... 1- 9,999 and then 10,000 - 10,999 etc... The reason why is because I keep getting this error: Fatal error: Allowed memory size of 536870912 bytes exhausted (tried to allocate 3 bytes) Which, incidentally, I don't understand how 3 bytes could exhaust 512M... So, if that's something that I can just change, that'd be great, although, still might be better to do this in batches?

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  • Effecient data structure design

    - by Sway
    Hi there, I need to match a series of user inputed words against a large dictionary of words (to ensure the entered value exists). So if the user entered: "orange" it should match an entry "orange' in the dictionary. Now the catch is that the user can also enter a wildcard or series of wildcard characters like say "or__ge" which would also match "orange" The key requirements are: * this should be as fast as possible. * use the smallest amount of memory to achieve it. If the size of the word list was small I could use a string containing all the words and use regular expressions. however given that the word list could contain potentially hundreds of thousands of enteries I'm assuming this wouldn't work. So is some sort of 'tree' be the way to go for this...? Any thoughts or suggestions on this would be totally appreciated! Thanks in advance, Matt

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  • Measuring debug vs release of ASP.NET applications

    - by Alex Angas
    A question at work came up about building ASP.NET applications in release vs debug mode. When researching further (particularly on SO), general advice is that setting <compilation debug="true"> in web.config has a much bigger impact. Has anyone done any testing to get some actual numbers about this? Here's the sort of information I'm looking for (which may give away my experience with testing such things): Execution time | Debug build | Release build -------------------+---------------+--------------- Debug web.config | average 1 | average 2 Retail web.config | average 3 | average 4 Max memory usage | Debug build | Release build -------------------+---------------+--------------- Debug web.config | average 1 | average 2 Retail web.config | average 3 | average 4 Output file size | Debug build | Release build -------------------+---------------+--------------- | size 1 | size 2

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  • Why freed struct in C still has data?

    - by kliketa
    When I run this code: #include <stdio.h> typedef struct _Food { char name [128]; } Food; int main (int argc, char **argv) { Food *food; food = (Food*) malloc (sizeof (Food)); snprintf (food->name, 128, "%s", "Corn"); free (food); printf ("%d\n", sizeof *food); printf ("%s\n", food->name); } I still get 128 Corn although I have freed food. Why is this? Is memory really freed?

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  • Garbage Collection in Java

    - by simion
    On the slides I am revising from it says the following: Live objects can be identified either by maintaining a count of the number of references to each object, or by tracing chains of references from the roots. Reference counting is expensive – it needs action every time a reference changes and it doesn’t spot cyclical structures, but it can reclaim space incrementally. Tracing involves identifying live objects only when you need to reclaim space – moving the cost from general access to the time at which the GC runs, typically only when you are out of memory. I understand the principles of why reference counting is expensive but do not understand what "doesn’t spot cyclical structures, but it can reclaim space incrementally." means. Could anyone help me out a little bit please? Thanks

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  • If free() knows the length of my array, why can't I ask for it in my own code?

    - by Chris Cooper
    I know that it's a common convention to pass the length of dynamically allocated arrays to functions that manipulate them: void initializeAndFree(int* anArray, int length); int main(){ int arrayLength = 0; scanf("%d", &arrayLength); int* myArray = (int*)malloc(sizeof(int)*arrayLength); initializeAndFree(myArray, arrayLength); } void initializeAndFree(int* anArray, int length){ int i = 0; for (i = 0; i < length; i++) { anArray[i] = 0; } free(anArray); } but if there's no way for me to get the length of the allocated memory from a pointer, how does free() "automagically" know what to deallocate? Why can't I get in on the magic, as a C programmer? Where does free() get its free (har-har) knowledge from?

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  • imported vm gives "failed to open/create network" error

    - by Colleen
    steps: 1. created a vm in windows 2. partitioned drive and installed ubuntu 3. exported the vm I created 4. mounted windows drive in ubuntu 5. imported the vm from the export, in the mounted drive 6. tried to start vm, got the following error: "Failed to open a session for the virtual machine XXXX. Failed to open/create the internal network 'HostInterfaceNetworking-Intel(R) 82579LM Gigabit Network Connection' (you might need to modprobe vboxnetflt to make it accessible) (VERR_INTNET_FLT_IF_NOT_FOUND). Result Code: NS_ERROR_FAILURE (0x80004005) Component: Console Interface: IConsole {1968b7d3-e3bf-4ceb-99e0-cb7c913317bb} " Network settings: Adapter 1: PCnet-FAST III (Bridged adapter, Intel(R) 82579LM Gigabit Network Connection)

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  • Allocated Private Bytes keeps going up in one computer but not the other

    - by Jacob
    OK, this may sound weird, but here goes. There are 2 computers, A (Pentium D) and B (Quad Core) with almost the same amount of RAM. If I run the same code on both computers, the allocated private bytes in A never goes down resulting in a crash later on. In B it looks like the private bytes is constantly deallocated and everything looks fine. In both computers, the working set is deallocated and allocated similarly. Could this be an issue with manifests or DLLs (system)? I'm clueless. Note: I observed the utilized memory with Process Explorer.

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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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  • release viewcontroller after presenting modally

    - by Jonathan
    I was watching CS193P Stanford course on Itunes, and in one of the lectures a demo was given and There it was said you could present the viewcontroller modally and then release it. Roughly like this (I know this isn't perfect but I'm on my PC atm) [self.view presentcontentmodally:myVC] [myVC release]; However this seems to produce problems. If I put a NSLog(@"%d", [myVC retainCount]) between those two lines then it returns 2 implying it is ok to release. However when I dismiss the myVC the app crashes. Nothing in the NSlog and the debugger won't show where it stopped. But I used malloc-history or something that some blog said would help. And found that it was the myVC. So should I be releasing myVC? (also when the modalVC has been dissmissed should the app's memory usuage go back to before the modalVC was presented?)

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  • In what circumstances can large pages produce a speedup ?

    - by timday
    Modern x86 CPUs have the ability to support larger page sizes than the legacy 4K (ie 2MB or 4MB), and there are OS facilities (Linux, Windows) to access this functionality. The Microsoft link above states large pages "increase the efficiency of the translation buffer, which can increase performance for frequently accessed memory". Which isn't very helpful in predicting whether large pages will improve any given situation. I'm interested in concrete, preferably quantified, examples of where moving some program logic (or a whole application) to use huge pages has resulted in some performance improvement. Anyone got any success stories ? There's one particular case I know of myself: using huge pages can dramatically reduce the time needed to fork a large process (presumably as the number of TLB records needing copying is reduced by a factor on the order of 1000). I'm interested in whether huge pages can also benefit more mundane applications though.

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  • How do I release an object allocated in a different AutoReleasePool ?

    - by ajcaruana
    Hi, I have a problem with the memory management in Objective-C. Say I have a method that allocates an object and stores the reference to this object as a member of the class. If I run through the same function a second time, I need to release this first object before creating a new one to replace it. Supposing that the first line of the function is: NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; This means that a different auto-release pool will be in place. The code to allocate the object is as follows: if (m_object != nil) [m_object release]; m_object = [[MyClass alloc] init]; [m_object retain]; The problem is that the program crashes when running the last line of the method: [pool release]; What am I doing wrong ? How can I fix this ? Regards Alan

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  • Force download menu for remote files

    - by o-logn
    Hey, I would like users to upload links on my site. When another user clicks on the link (e.g. PDF file), then I would like the download popup to show instead of actually displaying the PDF in browser. I know I can use Response.AddHeader/Response.WriteFile to achieve this, but the WriteFile method required a virtual path. However, the links uploaded by the user will be pointing to external servers. Can I still force the download popup to show and, if so, what would be the most efficient way of doing it? Thanks for any advice

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  • Writing to pointer out of bounds after malloc() not causing error

    - by marr
    Hi, when I try the code below it works fine. Am I missing something? main() { int *p; p=malloc(sizeof(int)); printf("size of p=%d\n",sizeof(p)); p[500]=999999; printf("p[0]=%d",p[500]); return 0; } I tried it with malloc(0*sizeof(int)) or anything but it works just fine. The program only crashes when I don't use malloc at all. So even if I allocate 0 memory for the array p, it still stores values properly. So why am I even bothering with malloc then?

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  • Wastage of resources in Virtualization

    - by Sabeen Malik
    I am not sure if this is the write place to ask the question. However i hope it is. When looking for a VPS earlier today, I was trying to understand how each container would work in the background. Keeping in mind the fact that the operating system uses most of the power and power on a system, wouldn't having multiple operating systems in the same machine mean more wastage of resources. For instance if i was running centOS on a dedicated box and it was running lets say 20 background OS level processes. Then i go and install a virtualization platform and install 5 more centOS virtual machines in the same system which are exactly the same as the host operating system. Doesn't this mean duplication of those 20 processes 6 times? So internally the context switching is happening between 120 processes instead of 20?

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  • Configure multiple keystores in JBoss depending on requested hostname

    - by Mo
    Hello, I have my J2EE application deployed into a JBossAS. My Application has to respond to two different hostnames (https://foo.com/myApp and https://bar.com/myApp). It is the same instance of the app serving those two hostnames. But I don't know how to configure the keystores. I need different keystores for each hostname. Is there a way to tie a virtual host in JBoss' server.xml to a specific connector? Or do I have to use two different IP-addresses and create a connector for each? A solution that does not require a second IP-address would be greatly appreciated.

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  • Looking at the C++ new[] cookie. How portable is this code?

    - by carleeto
    I came up with this as a quick solution to a debugging problem - I have the pointer variable and its type, I know it points to an array of objects allocated on the heap, but I don't know how many. So I wrote this function to look at the cookie that stores the number of bytes when memory is allocated on the heap. template< typename T > int num_allocated_items( T *p ) { return *((int*)p-4)/sizeof(T); } //test #include <iostream> int main( int argc, char *argv[] ) { using std::cout; using std::endl; typedef long double testtype; testtype *p = new testtype[ 45 ]; //prints 45 std::cout<<"num allocated = "<<num_allocated_items<testtype>(p)<<std::endl; delete[] p; return 0; } I'd like to know just how portable this code is.

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  • Force an object to be allocated on the heap

    - by Warren Seine
    A C++ class I'm writing uses shared_from_this() to return a valid boost::shared_ptr<>. Besides, I don't want to manage memory for this kind of object. At the moment, I'm not restricting the way the user allocates the object, which causes an error if shared_from_this() is called on a stack-allocated object. I'd like to force the object to be allocated with new and managed by a smart pointer, no matter how the user declares it. I thought it could be done through a proxy or an overloaded new operator, but I can't find a proper way of doing that. Is there a common design pattern for such usage? If it's not possible, how can I test it at compile time?

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  • Code corresponding to leaks with Visual Leak Detector

    - by matt
    I am trying to use Visual Leak Detector in Visual Studio 2008, here is an example of the output I get: Detected memory leaks! Dumping objects -> {204} normal block at 0x036C1568, 1920 bytes long. Data: < > 80 08 AB 03 00 01 AB 03 80 F9 AA 03 00 F2 AA 03 {203} normal block at 0x0372CC68, 40 bytes long. Data: <( > 28 00 00 00 80 02 00 00 E0 01 00 00 01 00 18 00 {202} normal block at 0x0372CC00, 44 bytes long. Data: << E > 3C 16 45 00 80 02 00 00 E0 01 00 00 01 00 00 00 The user's guide says to click on any line to jump to the corresponding file/line of code ; I tried clicking on every line but nothing happens! What am I missing?

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  • C++ deleting a pointer

    - by eSKay
    On this page, its written that One reason is that the operand of delete need not be an lvalue. Consider: delete p+1; delete f(x); Here, the implementation of delete does not have a pointer to which it can assign zero. Adding a number to a pointer shifts it forward in memory by those many number of sizeof(*p) units. So, what is the difference between delete p and delete p+1, and why would making the pointer 0 only be a problem with delete p+1?

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  • Freeing a character pointer returns error

    - by Kraffs
    I'm trying to free a character pointer after having used it but it returns a strange error. The error says: "_CrtDbgREport: String too long or IO Error" The debugger itself returns no errors while compiling. The code currently looks like this: void RespondToUser(SOCKET client, SOCKET server) { char buffer[80]; char *temp = malloc(_scprintf("HTTP/1.1 200 OK\r\n%s\r\nServer: %s\r\nConnection: close\r\n\r\nHi!", buffer, SERVER_NAME)); sprintf(temp, "HTTP/1.1 200 OK\r\n%s\r\nServer: %s\r\nConnection: close\r\n\r\nHi!", buffer, SERVER_NAME); send(client, temp, strlen(temp), 0); closesocket(client); free(temp); ListenToUsers(server); } The problem only occurs when I try to free the temp pointer from the memory and not otherwise. What might be causing this?

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  • C# class code loaded in RAM ?

    - by Spi1988
    hi, I would like to know whether the actual code of a C# class gets loaded in RAM when you instantiate the class? So for example if I have 2 Classes CLASS A , CLASS B, where class A has 10000 lines of code but just 1 field, an int. And class B has 10 lines of code and also 1 field an int as well. If I instantiate Class A will it take more RAM than Class B due to its lines of code ? A supplementary question, If the lines of code are loaded in memory together with the class, will they be loaded for every instance of the class? or just once for all the instances? Thanks in advance.

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  • Is Private Bytes >> Working Set?

    - by Jacob
    OK, this may sound weird, but here goes. There are 2 computers, A (Pentium D) and B (Quad Core) with almost the same amount of RAM running Windows XP. If I run the same code on both computers, the allocated private bytes in A never goes down resulting in a crash later on. In B it looks like the private bytes is constantly deallocated and everything looks fine. In both computers, the working set is deallocated and allocated similarly. Could this be an issue with manifests or DLLs (system)? I'm clueless. Note: I observed the utilized memory with Process Explorer. Question: During execution (where we have several allocations and deallocations) is it normal for the number of private bytes to be much bigger (1.5 GB vs 70 MB) than the working set?

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  • Split query result by half in TSQL (obtain 2 resultsets/tables)

    - by rubdottocom
    I have a query that returns a large number of heavy rows. When I transform this rows in a list of CustomObject I have a big memory peak, and this transformation is made by a custom dotnet framework that I can't modify. I need to retrieve a less number of rows to do "the transform" in two passes and then avoid the momery peak. How can I split the result of a query by half? I need to do it in DB layer. I thing to do a "Top count(*)/2" but how to get the other half? Thank you!

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  • What is the fastest way to write hundreds of files to disk using C#?

    - by Ehsan
    My program should write hundreds of files to disk, received by external resources (network) each file is a simple document that I'm currently store it with the name of GUID in a specific folder but creating hundred files, writing, closing is a lengthy process. Is there any better way to store these amount of files to disk? I've come to a solution, but I don't know if it is the best. First, I create 2 files, one of them is like allocation table and the second one is a huge file storing all the content of my documents. But reading from this file would be a nightmare; maybe a memory-mapped file technique could help. Could working with 30GB or more create a problem?

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