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• size of an image

  - by Mike

  From times to times I have to know the width and height of images. I am using the following code: UIImage *imageU = [UIImage imageWithContentsOfFile:[[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"myImage.png"]]; CGFloat imageW = CGImageGetWidth(imageU.CGImage); CGFloat imageH = CGImageGetHeight(imageU.CGImage); My question is that if it is there any other way to know the width and height of an image, in pixels, without having to load the image on a variable, that's probably consuming memory. Can the dimensions be read from the file directly without loading the whole image? thanks.

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• .net Compiler Optimizations

  - by Dested

  I am writing an application that I need to run at incredibly low speeds. The application creates and destroys memory in creative ways throughout its run, and it works just fine. I am wondering what compiler optimizations occur so I can try to build to that. One trick off hand is that the CLR handles arrays much faster than lists, so if you need to handle a ton of elements in a List, you may be better off calling ToArray() and handling it rather than calling ElementAt() again and again. I am wondering if there is any sort of comprehensive list for this kind of thing, or maybe the SO community can create one :-)

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• Where is the chink in Google Chrome's armor?

  - by kudlur

  While browsing with Chrome, I noticed that it responds extremely fast (in comparison with IE and Firefox on my laptop) in terms of rendering pages, including JavaScript heavy sites like gmail. This is what googlebook on Chrome has to say tabs are hosted in process rather than thread. compile javascript using V8 engine as opposed to interpreting. Introduce new virtual machine to support javascript heavy apps introduce "hidden class transitions" and apply dynamic optimization to speed up things. Replace inefficient "Conservative garbage colllection" scheme with more precise garbage collection scheme. Introduce their own task scheduler and memory manager to manage the browser environment. All this sounds so familiar, and Microsoft has been doing such things for long time.. Windows os, C++, C# etc compilers, CLR, and so on. So why isn't Microsoft or any other browser vendor taking Chrome's approach? Is there a flaw in Chrome's approach? If not, is the rest of browser vendor community caught unaware with Google's approach?

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• How to find the jmp address during a x86 function call?

  - by Bruce

  Suppose we have a call foo statement. So when the assembler encounters a call statement it breaks it down into - push ip + 6 jmp <addr of foo> I have the return address in a register ebx. Now I want to find out the "addr of foo". How do I do it? I want to confirm that the push statement is present before the jmp. Will the memory map look something like this? ------- push (what will be the value stored in this byte?? opcode ??) ------- jmp (what will be the value stored in this byte?? opcode ??) ------- jmp byte 1 ------- jmp byte 2 ------- jmp byte 3 ------- jmp byte 4 ------- return address stored in ebx ------- What are the opcodes for push and jmp?

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• Are @property's necessary for Interface Builder?

  - by Rits

  In my UIViewController subclass, I have 3 UIView's with each a @property as an IBOutlet. I do not use these properties at all in my code. The views get instantiated as soon as the view controller is created and they are deallocated when the view controller is deallocated. I was thinking; can't I just remove the @property's? I did, and I could still connect my instance variables (with IBOutlet) in Interface Builder. So my question now is; is there any use for properties in combination with Interface Builder, or is it OK to leave them out? Is it required for some memory management or something? Or are they really just for use in your own code? And if I do leave them out, do I still need to release them in dealloc?

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• How to remove duplicate records in a table?

  - by Mason Wheeler

  I've got a table in a testing DB that someone apparently got a little too trigger-happy on when running INSERT scripts to set it up. The schema looks like this: ID UNIQUEIDENTIFIER TYPE_INT SMALLINT SYSTEM_VALUE SMALLINT NAME VARCHAR MAPPED_VALUE VARCHAR It's supposed to have a few dozen rows. It has about 200,000, most of which are duplicates in which TYPE_INT, SYSTEM_VALUE, NAME and MAPPED_VALUE are all identical and ID is not. Now, I could probably make a script to clean this up that creates a temporary table in memory, uses INSERT .. SELECT DISTINCT to grab all the unique values, TRUNCATE the original table and then copy everything back. But is there a simpler way to do it, like a DELETE query with something special in the WHERE clause?

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• Simple wrapping of C code with cython

  - by Jose

  Hi, I have a number of C functions, and I would like to call them from python. cython seems to be the way to go, but I can't really find an example of how exactly this is done. My C function looks like this: void calculate_daily ( char *db_name, int grid_id, int year, double *dtmp, double *dtmn, double *dtmx, double *dprec, double *ddtr, double *dayl, double *dpet, double *dpar ) ; All I want to do is to specify the first three parameters (a string and two integers), and recover 8 numpy arrays (or python lists. All the double arrays have N elements). My code assumes that the pointers are pointing to an already allocated chunk of memory. Also, the produced C code ought to link to some external libraries.

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• Good Silverlight 4.0 chart / graph component?

  - by Duncan Bayne

  I've been using the Silverlight Toolkit but I'm finding the quality lacking; in particular this memory leak / phantom point bug renders the Chart component completely unusable. Can anyone recommend a good chart / graph component for Silverlight 4.0? I'm looking for one that provides: multiple simultaneous series, both scatter and line multi-select of points configurable tool-tips automatic axis scaling real-time update of data That last point sounds trivial but is tripping up the Silverlight Toolkit Chart; if you rapidly change the axis range, it sometimes leaves phantom points behind in addition to the points it should be displaying.

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• Objective-C NSString Assignment Problem

  - by golfromeo

  In my Cocoa application, in the header file, I declare a NSString ivar: NSString *gSdkPath; Then, in awakeFromNib, I assign it to a value: gSdkPath = @"hello"; Later, it's value is changed in the code: gSdkPath = [NSString stringWithString:[folderNames objectAtIndex:0]]; (the object returned from objectAtIndex is an NSString) However, after this point, in another method when I try to NSLog() (or do anything with) the gSdkPath variable, the app crashes. I'm sure this has something to do with memory management, but I'm beginning with Cocoa and not sure exactly how this all works. Thanks for any help in advance.

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• Free object/widget in GTK?

  - by wag2639

  I've got a pack box in my GTK application and I'm replacing it every once in a while with a completely new entry (at least for now cause I'm in a hurry). Since I'm replacing it with a new instance, do I need to explicitly free from memory the old pack box contents or is there some garbage collection in GTK? If I do need to explicitly need to free the object, is there a command that will recursively go to all objects in that tree (like will it clear my button in a box container inside my main pack box)? I'm using C/GTK-2.0 (gcc v4.4.3 and GTK 2.20.0).

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• Storing object into cache using Linq classes and velocity

  - by Arun

  I careated couple of linq classes & marked the datacontext as unidirectional. Out of four classes; one is main class while other three are having the one to many relationship with first one; When I load the object of main class & put into the memory OR serialize it into an XML file; I never get the child class data while it is maked as DataContractAttribute. How can I force object to put the child class data into XML file or into cache ?

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• k-means clustering in R on very large, sparse matrix?

  - by movingabout

  Hello, I am trying to do some k-means clustering on a very large matrix. The matrix is approximately 500000 rows x 4000 cols yet very sparse (only a couple of "1" values per row). The whole thing does not fit into memory, so I converted it into a sparse ARFF file. But R obviously can't read the sparse ARFF file format. I also have the data as a plain CSV file. Is there any package available in R for loading such sparse matrices efficiently? I'd then use the regular k-means algorithm from the cluster package to proceed. Many thanks

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• Strange errors in Visual C++ :: 'malloc' : function does not take 1 arguments

  - by pecker

  Error 38 error C2660: 'malloc' : function does not take 1 arguments C:\VolumeRenderer\render.cpp 296 1 VolumeRenderer Error 39 error C2660: 'malloc' : function does not take 1 arguments C:\VolumeRenderer\render.cpp 412 1 VolumeRenderer Error 40 error C2660: 'malloc' : function does not take 1 arguments C:\VolumeRenderer\render.cpp 414 1 VolumeRenderer Error 41 error C2660: 'read_den' : function does not take 4 arguments C:\VolumeRenderer\render.cpp 506 1 VolumeRenderer My all malloc sections are like this: /* allocate space for the raw data */ density_size = BRAIN_XLEN * BRAIN_YLEN * BRAIN_ZLEN; density = (unsigned char*)malloc(density_size); if (density == NULL) { fprintf(stderr, "out of memory\n"); exit(1); } regarding read_den (last error) unsigned char *read_den(char *filename,int *xptr,int *yptr,int *zptr)// function prototype src_volume = read_den(src_file, &src_xlen, &src_ylen, &src_zlen);// fucntion call Is it my code or the errors that are absurd. How to rectify them?

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• Reducing unnecessary same values in Class member variables ....

  - by Freshblood

  class A { public int a; public int c; } i will create 10 instances from A.Then i will create 15 instances from A again... go on. first 10 instance will have same value for a variable and next 15 instances will have again same value for a.But I don't mean that both group has same values for a .Problem is create same a value 10 times in first group and 15 times in second group on memory unnecessary. What would be Best solution or solutions for reduce unnecessary datas in this situation?

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• Simplest one-to-many Map case in Hibernate doesn't work in MySQL

  - by Malvolio

  I think this is pretty much the simplest case for mapping a Map (that is, an associative array) of entities. @Entity @AccessType("field") class Member { @Id protected long id; @OneToMany(cascade = CascadeType.ALL, fetch=FetchType.LAZY) @MapKey(name = "name") private Map<String, Preferences> preferences = new HashMap<String, Preferences>(); } @Entity @AccessType("field") class Preferences { @ManyToOne Member member; @Column String name; @Column String value; } This looks like it should work, and it does, in HSQL. In MySQL, there are two problems: First, it insists that there be a table called Members_Preferences, as if this were a many-to-many relationship. Second, it just doesn't work: since it never populates Members_Preferences, it never retrieves the Preferences. [My theory is, since I only use HSQL in memory-mode, it automatically creates Members_Preferences and never really has to retrieve the preferences map. In any case, either Hibernate has a huge bug in it or I'm doing something wrong.]

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• Does AsEnumerable() cache all result (LINQ)

  - by Akshay

  When we call a query operator on a sequence, a sequence-specific operator gets called. I mean if i call Where<>() operator on IEnumerable<>, the operator that will be called will be defined in Enumerable class and if it's called on IQueryable<>, the one defined in Queryable class will be called. Consider the operator Reverse, defined in the Enumerable class. If i want to call it on Iqueryable<> then I must use the AsEnumerable<>() operator to first convert it into IEnumerable<>. db.Countries.OrderBy(cntry=>cntry.CountryName).AsEnumerable().Reverse() But the Reverse operator got to have all records at the same time so that it can reverse them. In the above code do all the records get loaded in memory first and then the Reverse() operator is reversing it ?

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• what changes when your input is giga/terabyte sized?

  - by Wang

  I just took my first baby step today into real scientific computing today when I was shown a data set where the smallest file is 48000 fields by 1600 rows (haplotypes for several people, for chromosome 22). And this is considered tiny. I write Python, so I've spent the last few hours reading about HDF5, and Numpy, and PyTable, but I still feel like I'm not really grokking what a terabyte-sized data set actually means for me as a programmer. For example, someone pointed out that with larger data sets, it becomes impossible to read the whole thing into memory, not because the machine has insufficient RAM, but because the architecture has insufficient address space! It blew my mind. What other assumptions have I been relying in the classroom that just don't work with input this big? What kinds of things do I need to start doing or thinking about differently? (This doesn't have to be Python specific.)

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• Why does tokyo tyrant slow down exponentially even after adjusting bnum?

  - by HenryL

  Has anyone successfully used Tokyo Cabinet / Tokyo Tyrant with large datasets? I am trying to upload a subgraph of the Wikipedia datasource. After hitting about 30 million records, I get exponential slow down. This occurs with both the HDB and BDB databases. I adjusted bnum to 2-4x the expected number of records for the HDB case with only a slight speed up. I also set xmsiz to 1GB or so but ultimately I still hit a wall. It seems that Tokyo Tyrant is basically an in memory database and after you exceed the xmsiz or your RAM, you get a barely usable database. Has anyone else encountered this problem before? Were you able to solve it?

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• What is the best way to pass server side variables to JavaScript on the client side?

  - by steve_c

  Our application uses a lot of configuration options. Those options need to be reflected on the client side in the form of User preferences, site wide preferences, etc. Currently, we pass server side settings down to the client side in the form of JSON that is stored in custom attributes in the markup for a specific element (and no, our application currently doesn't worry about W3C validation). We then retrieve the data from the custom attribute, and parse it into a JSON object for use in script using jQuery. One drawback to this is referencing attributes on elements from within event handlers. I know this is frowned upon, as it can create circular references, and subsequently memory leaks. I would much prefer to use jQuery's data function, but you can't invoke this from the server side at page render time. What does everyone else do in this type of scenario?

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• Get license file from a folder in C# project

  - by daft

  I have a license file that I need to access at runtime in order to create pdf-files. After I have created the in memory pdf, I need to call a method on that pdf to set the license, like this: pdf.SetLicense("pathToLicenseFileHere"); The license file is located in the same project as the.cs-file that creates the pdf, but is in a separate folder. I cannot get this simple thing to behave correctly, which makes me a bit sad, since it really shouldn't be that hard. :( I try to set the path like this: string path = @"\Resources\File.lic"; But it just isn't working out for me.

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• Fault exception trashes a register causing a crash in [NSInvocation invoke]

  - by Mike Weller

  I have an NSOperation which fetches some objects from a core data persistent store and sums up a few totals. Sometimes an object is deleted while the operation in in progress, so a core data fault exception occurs. I try/catch the exception while summing to ignore it because I just want to skip objects that cannot be faulted in. However, when one of these fault exceptions occurs (and I swallow it) there is a crash after the invocation returns in [NSInvocation invoke]. It's a bad memory access when dereferencing the value in r10 which according to GDB on a successful run points to one of these: (gdb) x 0x38388348 0x38388348 <OBJC_IVAR_$_NSInvocation._retdata>: 0x00000008 If a fault exception occured a value of 0x02 is in the register which causes the crash. A quick google search tells me that r10 should be saved by the callee, meaning it is not being restored by whatever code is changing it when this exception occurs. Can anybody explain this? I'm not an expert when it comes to these kinds of low-level details

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• C# 2D Vector Graphics Game using DirectX or OpenGL?

  - by Brian

  Hey Guys, So it has been a while since I have done any game programming in C#, but I have had a recent bug to get back into it, and I wanted some opinions on what configuration I should use. I wanted to use C# as that is what I use for work, and have become vary familiar with. I have worked with both DirectX and OpenGL in the past, but mostly in 3D, but now I am interested in writing a 2D game with all vector graphics, something that resembles the look of Geometry Wars or the old Star Wars arcade game. Key points I am interested in: • Ease of use/implementation. • Easy on memory. (I plan on having a lot going on at once) • Looks good, I don't want curve to look pixelated. • Maybe some nice effects like glow or particle. I am open to any and all suggestions, maybe even something I have not thought of... Thanks in advance!

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• append versus resize for numpy array

  - by Abruzzo Forte e Gentile

  Hi all I would like to append a value at the end of my numpy.array. I saw numpy.append function but this performs an exact copy of the original array adding at last my new value. I would like to avoid copies since my arrays are big. I am using resize method and then set the last index available to the new value. Can you confirm that resize is the best way to append a value at the end? Is it not moving memory around someway? Thanks AFG oldSize = myArray,shape(0) myArray.resize( oldSize + 1 ) myArray[oldSize] = newValue

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• A way of allocating multidimensional arrays dynamically

  - by C77431

  salute.. I am learning dynamic allocations for multidimensional arrays in a book and I found some ways for that, And now haven't problem in it. But the author of the book shows us a way, but it doesn't work correctly. It is this: pbeans = new double [3][4]; // Allocate memory for a 3x4 array And this is the error: error C2440: '=' : cannot convert from 'int (*)[4]' to 'int *' how should i define pbeans ( if this type of coding is legal)? and what is the problem exactly? Regards.

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• Joomla article not showing in the frontend but its visible in administrative part.

  - by user248674

  I have a very big article to be put into our joomla site. At first I was getting "Fatal error: Allowed memory size of 8388608 bytes exhausted (tried to allocate 285487 bytes) in..." . But then I increased the memory_limit in php.ini . And I was able to create the article. Now I can view the article by logging into backend. But the article is not at all visible in the front end. If I click on the menu item pointing to that article, all I can see is a blank page with nothing in it. All other articles in the site are visible properly. Any idea? ps: I have enabled the error reporting to maximum, also ran the site in debugging mode. But saw nothing unusual.

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