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  • Free Optimization Library in C#

    - by Ngu Soon Hui
    Is there any optimization library in C#? I have to optimize a complicated equation in excel, for this equation there are a few coefficients. And I have to optimize them according to a fitness function that I define. So I wonder whether there is such a library that does what I need?

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  • Performance Optimization for Matrix Rotation

    - by Summer_More_More_Tea
    Hello everyone: I'm now trapped by a performance optimization lab in the book "Computer System from a Programmer's Perspective" described as following: In a N*N matrix M, where N is multiple of 32, the rotate operation can be represented as: Transpose: interchange elements M(i,j) and M(j,i) Exchange rows: Row i is exchanged with row N-1-i A example for matrix rotation(N is 3 instead of 32 for simplicity): ------- ------- |1|2|3| |3|6|9| ------- ------- |4|5|6| after rotate is |2|5|8| ------- ------- |7|8|9| |1|4|7| ------- ------- A naive implementation is: #define RIDX(i,j,n) ((i)*(n)+(j)) void naive_rotate(int dim, pixel *src, pixel *dst) { int i, j; for (i = 0; i < dim; i++) for (j = 0; j < dim; j++) dst[RIDX(dim-1-j, i, dim)] = src[RIDX(i, j, dim)]; } I come up with an idea by inner-loop-unroll. The result is: Code Version Speed Up original 1x unrolled by 2 1.33x unrolled by 4 1.33x unrolled by 8 1.55x unrolled by 16 1.67x unrolled by 32 1.61x I also get a code snippet from pastebin.com that seems can solve this problem: void rotate(int dim, pixel *src, pixel *dst) { int stride = 32; int count = dim >> 5; src += dim - 1; int a1 = count; do { int a2 = dim; do { int a3 = stride; do { *dst++ = *src; src += dim; } while(--a3); src -= dim * stride + 1; dst += dim - stride; } while(--a2); src += dim * (stride + 1); dst -= dim * dim - stride; } while(--a1); } After carefully read the code, I think main idea of this solution is treat 32 rows as a data zone, and perform the rotating operation respectively. Speed up of this version is 1.85x, overwhelming all the loop-unroll version. Here are the questions: In the inner-loop-unroll version, why does increment slow down if the unrolling factor increase, especially change the unrolling factor from 8 to 16, which does not effect the same when switch from 4 to 8? Does the result have some relationship with depth of the CPU pipeline? If the answer is yes, could the degrade of increment reflect pipeline length? What is the probable reason for the optimization of data-zone version? It seems that there is no too much essential difference from the original naive version. EDIT: My test environment is Intel Centrino Duo processor and the verion of gcc is 4.4 Any advice will be highly appreciated! Kind regards!

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  • Need help with basic optimization problem

    - by ??iu
    I know little of optimization problems, so hopefully this will be didactic for me: rotors = [1, 2, 3, 4...] widgets = ['a', 'b', 'c', 'd' ...] assert len(rotors) == len(widgets) part_values = [ (1, 'a', 34), (1, 'b', 26), (1, 'c', 11), (1, 'd', 8), (2, 'a', 5), (2, 'b', 17), .... ] Given a fixed number of widgets and a fixed number of rotors, how can you get a series of widget-rotor pairs that maximizes the total value where each widget and rotor can only be used once?

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  • Any Javascript optimization benchmarks?

    - by int3
    I watched Nicholas Zakas' talk, Speed up your Javascript, with some interest. I liked how he benchmarked the various performance improvements created by various optimization techniques, e.g. reducing calls to deeply nested objects, changing loops to count down instead of up, etc. I would like to run these benchmarks myself though, to see exactly how our current browsers are faring. I guess it wouldn't be too difficult to cook up some timed loops, but I'd like to know if there are any existing implementations out there.

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  • How to use Application Verifier to find memory leaks

    - by Patrick
    I want to find memory leaks in my application using standard utilities. Previously I used my own memory allocator, but other people (yes, you Neil) suggested to use Microsoft's Application Verifier, but I can't seem to get it to report my leaks. I have the following simple application: #include <iostream> #include <conio.h> class X { public: X::X() : m_value(123) {} private: int m_value; }; void main() { X *p1 = 0; X *p2 = 0; X *p3 = 0; p1 = new X(); p2 = new X(); p3 = new X(); delete p1; delete p3; } This test clearly contains a memory leak: p2 is new'd but not deleted. I build the executable using the following command lines: cl /c /EHsc /Zi /Od /MDd test.cpp link /debug test.obj I downloaded Application Verifier (4.0.0665) and enabled all checks. If I now run my test application I can see a log of it in Application Verifier, but I don't see the memory leak. Questions: Why doesn't Application Verifier report a leak? Or isn't Application Verifier really intended to find leaks? If it isn't which other tools are available to clearly report leaks at the end of the application (i.e. not by taking regular snapshots and comparing them since this is not possible in an application taking 1GB or more), including the call stack of the place of allocation (so not the simple leak reporting at the end of the CRT) If I don't find a decent utility, I still have to rely on my own memory manager (which does it perfectly).

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  • IE doesnot clear Flash Object from memory

    - by Abhi
    Hi, I have dynamically added a Flex Object in a HTML page through JavaScript. The Flex object is located in a "div" tag. Now when I call the "removeChild" JavScript function to remove the dynamically added "Object" tag, the object tag gets removed succesfully; however the memory that has increased due to the loading of the Flex Object is never recollected by IE. Even if I refresh the browser the memory is still not cleared. How do I recollect the memory that was allocayed to my Flex Object?

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  • Display Image from Byte Array in WPF - Memory Issues

    - by ChrisFletcher
    Hi, I've developed an application to capture and save images to a database, but I'm having an issue with memory usage. On my domain object I have 3 properties: Image - Byte array, contents are a jpg RealImageThumb - The byte array converted to a BitmapImage and shrunk, displayed to the user in a gridview with other thumbnails RealImage - Has no setter, the byte array converted to a bitmap source, this is shown in a tooltip when the user hovers over it. The issue I have is that if a user hovers over each image in turn the memory usage spirals. I realise that as a user hovers over bitmap sources are generated and the memory isn't freed up, I've tried giving RealImage a backing property and assigning this to null after but again the memory isn't freed up (waiting for the garbage colelctor?.

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  • What are some Java memory management best practices?

    - by Ascalonian
    I am taking over some applications from a previous developer. When I run the applications through Eclipse, I see the memory usage and the heap size increase a lot. Upon further investigation, I see that they were creating an object over-and-over in a loop as well as other things. I started to go through and do some clean up. But the more I went through, the more questions I had like "will this actually do anything?" For example, instead of declaring a variable outside the loop mentioned above and just setting its value in the loop... they created the object in the loop. What I mean is: for(int i=0; i < arrayOfStuff.size(); i++) { String something = (String) arrayOfStuff.get(i); ... } versus String something = null; for(int i=0; i < arrayOfStuff.size(); i++) { something = (String) arrayOfStuff.get(i); } Am I incorrect to say that the bottom loop is better? Perhaps I am wrong. Also, what about after the second loop above, I set "something" back to null? Would that clear out some memory? In either case, what are some good memory management best practices I could follow that will help keep my memory usage low in my applications? Update: I appreciate everyones feedback so far. However, I was not really asking about the above loops (although by your advice I did go back to the first loop). I am trying to get some best practices that I can keep an eye out for. Something on the lines of "when you are done using a Collection, clear it out". I just really need to make sure not as much memory is being taken up by these applications.

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  • COM C# Memory leak Tracing

    - by maxfridbe
    Is there a way to find out the memory usage of each dll within a c# application using com dll's? Or what would you say is the best way to find out why memory grows exponentially when using a com object (IE. Whether the COM object has a memory leak, or whether some special freeing up of objects passed to managed code has to occur(and/or how to do that)).

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  • Memory Allocation Profiling in C++

    - by Amit Kumar
    I am writing an application and am surprised to see its total memory usage is already too high. I want to profile the dynamic memory usage of my application: How many objects of each kind are there in the heap, and which functions created these objects? Also, how much memory is used by each of the object? Is there a simple way to do this? I am working on both linux and windows, so tools of any of the platforms would suffice. NOTE: I am not concerned with memory leaks here.

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  • Stack memory in Android

    - by Matt
    I'm writing an app that has a foreground service, content provider, and a Activity front end that binds to the service and gets back a List of objects using AIDL. The service does work and updates a database. If I leave the activity open for 4-8+ hours, and go to the "Running Services" section under settings on the phone (Nexus One) an unusually large amount of memory being used is shown (~42MB). I figure there is a leak. When I check the heap memory i get Heap size:~18MB, ~2MB allocated, ~16MB free. Analyzing the hprof in Eclipse MAT seems fine, which leads me to theorize that memory is leaking on the stack. Is this even possible? If it is, what can I do to stop or investigate the leak? Is the reported memory usage on the "Running Services" section of android even correct (I assume it is)? Another note: I have been unable to reproduce this issue when the UI is not up (with only the service running)

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  • Silverlight 4 seems like starving of memory

    - by Marco
    I have been playing a bit with Silverlight and try to port my Silverlight 3.0 application to Silverlight 4.0. My application loads different XAP files and upon a user request create an instance of a Xaml user control and adds it to the main container, in a sort of MEF approach in order I can have an extensible and pluggable application. The application is pretty huge and to keep acceptable the performances and the initial loading I have built up some helper classes to load in the background all pages and user controls that might be used later on. On Silverlight 3.0 everything was running smoothly without any problem so far. Switching to SL 4.0 I have noticed that when the process approaches to create the instances of the user controls the layout freezes unexpectedly for a minute and sometimes for more. Looking at the task manager the memory usage of IE jumps from 50MB to 400MB and sometimes up to 1.5 GB. If the process won't take that much the layout is rendered properly even though the memory usage is still extremely high. Otherwise everything crashes due to out of memory exception. Running the same application compiled in SL3, the memory used is about 200MB when all the usercontrols are loaded. Time spent to load the application in SL3 is about 10 seconds, while it takes up to 3 mins in SL4 There are no transparencies, no opacities set, no effects and animations in the layout. User controls are instantied on the fly and added or removed in the visual tree on purpose when the user switches from one screen to another. The resources are all cleaned properly when a usercontrol is removed from the visual tree to allow the GC to operate in the background. I may do something wrong but I could not figure out where exactly nail out the source of this problem. As far as I know there is no memory profiler in SL4 that can help me out to find where to look at. But again I could not be updated on new debugging tools available.

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  • Objective-C memory leak in loading remote content

    - by Ican Zilb
    I try to load a plist file from my server. I can think of 2 ways to do that, but for both Instruments says there's huge memory leak : NSData* plistData = [NSData dataWithContentsOfURL:url]; and NSDictionary* updateDigest = [NSDictionary dictionaryWithContentsOfURL: [NSURL URLWithString:updateURL] ]; The backtrace of the memory leak leads to __CFURLCache in CFNetwork and I am wondering if something can be done to fix the leak? Any other way to load a remote plist xml, without the memory leakage ? Thanks

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  • Why can .NET not have memory leaks?

    - by Dinah
    Ignoring unsafe code, .NET cannot have memory leaks. I've read this endlessly from many experts and I believe it. However, I do not understand why this is so. It is my understanding that the framework itself is written in C++ and C++ is susceptible to memory leaks. Is the underlying framework so well-written, that it absolutely does not have any possibility of internal memory leaks? Is there something within the framework's code that self-manages and even cures its own would-be memory leaks? Is the answer something else that I haven't considered?

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  • imagejpeg memory exhaustion

    - by 0plus1
    I'm creating thumbnails cycling through a lot of images, when I find a large image I get: Fatal error: Allowed memory size of 33554432 bytes exhausted (tried to allocate 13056 bytes) Now I already know how to circumvent this with: ini_set('memory_limit', '-1'); What I want to know is why it exhaust the memory! Is there some debug tools that will show me exactly when memory is exhausting? And specifically that will show me if there are variables/arrays that are killing my memory? OR, are there better way to resize images other then: $thumb=imagecreatetruecolor($newwidth,$newheight); $source=imagecreatefromjpeg($imgfile); imagecopyresampled($thumb,$source,0,0,0,0,$newwidth,$newheight,$width,$height); imagejpeg($thumb,$destinationfile,85); ? Thank you very much!

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  • Objective-C Memory Management: When do I [release]?

    - by Sahat
    I am still new to this Memory Management stuff (Garbage Collector took care of everything in Java), but as far as I understand if you allocate memory for an object then you have to release that memory back to the computer as soon as you are finished with your object. myObject = [Object alloc]; and [myObject release]; Right now I just have 3 parts in my Objective-C .m file: @Interface, @Implementation and main. I released my object at the end of the program next to these guys: [pool drain]; return 0; But what if this program were to be a lot more complicated, would it be okay to release myObject at the end of the program? I guess a better question would be when do I release an object's allocated memory? How do I know where to place [myObject release];?

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  • Solving iPhone/iPad out of memory issues

    - by Joonas Trussmann
    I have a strange issue where I'm scrolling through a paged UIScrollView which displays the pages of a PDF document (using Quartz 2D and CATiledLayer). When I page through memory allocation looks fine with it going up with a few initial pages and then keeping it steady as it obviously releases the memory kept for earlier pages. Upon hitting page x (not a certain PDF page or a certain number per se) memory usage goes from a couple of megs to 308 megs and the app crashes. So my question is: how to best try to find what's causing this? The object alloc tool in instruments shows the memory as simply going to malloc. (in huge chunks).

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  • Virtual Memory and Paging

    - by Kenshin
    Hello, I am doing some exercices to understand how the virtual memory and paging works, my question is as follows : Suppose we use a paged memory with pages of 1024 bytes, the virtual address space is of 8 pages but the physical memory can only contain 4 frames of pages. Replacement policy is LRU. What is the physical address in main memory that corresponds to virtual address 4096? and how do you get to that result? Same thing as question 1 but with virtual address 1024 A page fault occurs when accessing a word in page 0, which page frame will be used to receive the virtual page 0? Page Image

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  • renderInContext creating memory that is not promptly released

    - by iworkinprogress
    While debugging in instruments using 'ObjectAlloc' I'm noticing 7megs of memory being allocated for the renderInContext call, but it never is released. When I comment out the renderInContext call this doesn't happen, and future renderInContext calls does not continue to increase the memory allotment. UIGraphicsBeginImageContext(contentHolder.bounds.size); [contentHolder.layer renderInContext:UIGraphicsGetCurrentContext()]; UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); Is there a way to force this memory to be released?

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  • Memory leak with preg_replace

    - by Silvio Donnini
    I'm using the preg_replace function to replace accents in a string, I'm working with UTF-8. I have incurred in what seems to be a memory leak, but I can't isolate the root cause, my code is rather simple: preg_replace( array_keys($aToNoAccents), array_values($aToNoAccents), $sText ); where $aToNoAccents is an associative array with entries like '~[A]~u' => 'A', '~[C]~u' => 'C',. My script prints this error for the above line: Fatal error: Allowed memory size of 1073741824 bytes exhausted (tried to allocate 3039 bytes) Obviously it's not a matter of increasing the allowed memory for PHP, (a 1Gb footprint is way off the scale of my application). Also, that line is executed thousands of times without problems but, just for some cases which are difficult to reproduce, it yields the error. Is anyone aware of memory problems with preg_replace and UTF-8 strings? Am I to use special care in passing actual parameters to such function? I'm using PHP 5.2.6-3 with Suhosin-Patch thanks Silvio

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  • Loading machinecode from file into memory and executing in C -- mprotect failing

    - by chartreusekitsune
    Hi I'm trying to load raw machine code into memory and run it from within a C program, right now when the program executes it breaks when trying to run mprotect on the memory to make it executable. I'm also not entirely sure that if the memory does get set right it will execute. What I currently have is the following: #include <memory.h> #include <sys/mman.h> #include <stdio.h> int main ( int argc, char **argv ) { FILE *fp; int sz = 0; char *membuf; int output = 0; fp = fopen(argv[1],"rb"); if(fp == NULL) { printf("Failed to open file, aborting!\n"); exit(1); } fseek(fp, 0L, SEEK_END); sz = ftell(fp); fseek(fp, 0L, SEEK_SET); membuf = (char *)malloc(sz*sizeof(char)); if(membuf == NULL) { printf("Failed to allocate memory, aborting!\n"); exit(1); } memset(membuf, 0x90, sz*sizeof(char)); if( mprotect(membuf, sz*sizeof(char), PROT_EXEC | PROT_READ | PROT_WRITE) == -1) { printf("mprotect failed!!! aborting!\n"); exit(1); } if((sz*sizeof(char)) != fread(membuf, sz*sizeof(char), 1, fp)) { printf("Read failed, aborting!\n"); exit(1); } __asm__ ( "call %%eax;" : "=a" (output) : "a" (membuf) ); printf("Output = %x\n", output); return 0; }

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