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• Can I force MySQL to output results before query is completed?

  - by Gordon Royle

  I have a large MySQL table (about 750 million rows) and I just want to extract a couple of columns. SELECT id, delid FROM tbl_name; No joins or selection criteria or anything. There is an index on both fields (separately). In principle, it could just start reading the table and spitting out the values immediately, but in practice the whole system just chews up memory and basically grinds to a halt. It seems like the entire query is being executed and the output stored somewhere before ANY output is produced... I've searched on unbuffering, turning off caches etc, but just cannot find the answer. (mysqldump is almost what I want except it dumps the whole table - but at least it just starts producing output immediately)

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• XNA Multi-Thread Jitters

  - by Ice Phoenix

  Hi guys, brand new question. Just implemented multi-threading into my XNA game as it was unable to keep up with using 1 processor. MT is all implemented fine and everything, however the player seems to jitter all over the spot every now and then. I originally thought it was a loss of data between the update and render, but even when i did the player update in the render it did the same thing. It's not a memory/processor issue as i'm no where near maxing out my RAM or processors. It's strange aswell because none of the other entities in the game seem to have any of these issues. Any ideas at all??

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• Showing a hidden form

  - by Arcadian

  Newb question: how do i show a from that have been hidden using this.Hide(); I have tried MainMenuForm.Show(); and this just says i need an object ref have tried: MainMenuForm frmMainMenu = new MainMenuForm(); frmMainMenu.Show(); which seems to show the appropriate form. but when you exit the app, it is still held in memory because it hasn't shown the form that was hidden, instead it has shown a new version of the form. in effect having 2 instances of the form (one hidden, one visible). whats the correct procedure here Thanks in advance

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• Improving the performance of an nHibernate Data Access Layer.

  - by Amitabh

  I am working on improving the performance of DataAccess Layer of an existing Asp.Net Web Application. The scenerios are. Its a web based application in Asp.Net. DataAccess layer is built using NHibernate 1.2 and exposed as WCF Service. The Entity class is marked with DataContract. Lazy loading is not used and because of the eager-fetching of the relations there is huge no of database objects are loaded in the memory. No of hits to the database is also high. For example I profiled the application using NHProfiler and there were about 50+ sql calls to load one of the Entity object using the primary key. I also can not change code much as its an existing live application with no NUnit test cases at all. Please can I get some suggestions here?

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• Programatically determining file "size on disk" in advance

  - by porkchop

  I need to know how big a given in-memory buffer will be as an on-disk (usb stick) file before I write it. I know that unless the size falls on the block size boundary, its likely to get rounded up, e.g. a 1 byte file takes up 4096 bytes on-disk. I'm currently doing this using GetDiskFreeSpace() to work out the disk block size, then using this to calculate the on-disk size like this: GetDiskFreeSpace(szDrive, &dwSectorsPerCluster, &dwBytesPerSector, NULL, NULL); dwBlockSize = dwSectorsPerCuster * dwBytesPerSector; if (dwInMemorySize % dwBlockSize != 0) { dwSizeOnDisk = ((dwInMemorySize / dwBlockSize) * dwBlockSize) + dwBlockSize; } else { dwSizeOnDisk = dwInMemorySize; } Which seems to work fine, BUT GetDiskFreeSpace() only works on disks up to 2GB according to MSDN. GetDiskFreeSpaceEx() doesn't return the same information, so my question is, how else can I calculate this information for drives 2GB? Is there an API call I've missed? Can I assume some hard values depending on the overall disk size?

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• What is the difference between the * and the & operators in c programming?

  - by Wesley

  I am just making sure I understand this concept correctly. With the * operator, I make a new variable, which is allocated a place in memory. So as to not unnecessarily duplicate variables and their values, the & operator is used in passing values to methods and such and it actually points to the original instance of the variable, as opposed to making new copies...Is that right? It is obviously a shallow understanding, but I just want to make sure I am not getting them mixed up. Thanks!

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• Simple integer encryption

  - by tloflin

  Is there a simple algorithm to encrypt integers? That is, a function E(i,k) that accepts an n-bit integer and a key (of any type) and produces another, unrelated n-bit integer that, when fed into a second function D(i,k) (along with the key) produces the original integer? Obviously there are some simple reversible operations you can perform, but they all seem to produce clearly related outputs (e.g. consecutive inputs lead to consecutive outputs). Also, of course, there are cryptographically strong standard algorithms, but they don't produce small enough outputs (e.g. 32-bit). I know any 32-bit cryptography can be brute-forced, but I'm not looking for something cryptographically strong, just something that looks random. Theoretically speaking it should be possible; after all, I could just create a dictionary by randomly pairing every integer. But I was hoping for something a little less memory-intensive.

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• What could cause a returning function to crash? C++

  - by JeanOTF

  So I have been debugging this error for hours now. I writing a program using Ogre3d relevant only because it doesn't load symbols so it doesn't let me stack trace which made finding the location of the crash even harder. So, write before I call a specific function I print out "Starting" then I call the function and immediately after I print "Stopping". Throughout the function I print out letters A-F where F is printed right before the function returns (one line above the last '}') The weird thing is when the crash occurs it is after the 'F' is printed but there is no 'Stopping'. Does this mean that the crash is happening in between somewhere? The only thing I can think of is something going wrong during the deallocation of some of the memory allocated during the function. I've never had anything happen like this, I will keep checking to make sure it's going wrong where I think it is.

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• Load python module not from a file

  - by user575061

  Hello, I've got some python code in a library that attempts to load a simple value from a module that will exist for the applications that use this library from somemodule import simplevalue Normally, the application that uses the library will have the module file and everything works fine. However, in the unit tests for this library the module does not exist. I know that I can create a temporary file and add that file to my path at runtime, but I was curious if there is a way in python to load something in to memory that would allow the above import to work. This is more of a curiosity, saying "add the module to your test path" is not helpful :P

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• DataSet XML export is empty

  - by Shaine

  I've got in-memory dataset with couple of tables that is populated in code. Data-bound grids on the gui show table contents without a problem. Then I try to export the dataset into XML: ds.WriteXml(fdSave.FileName, XmlWriteMode.WriteSchema); and get empty XML (with couple of lines regarding dataset names but without any tables) If I export table directly I've got all the data but dataset name is obviously wrong: ds.Fields.WriteXml(fdSave.FileName, XmlWriteMode.WriteSchema); What am I missing? Is there any reasonable way to write the whole dataset into file?

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• Do you know of a C dictionary that supports COW transactions?

  - by Tim Post

  I'm looking for a key - value dictionary library written in C that supports a theoretically unlimited number of cheap transactions. I'd like to have one dictionary in memory, with hundreds of threads starting transactions, possibly modifying the dictionary, ending (completing) the transaction or potentially aborting the transaction. Only 50% of the time will these threads actually modify the dictionary. Most dictionary transaction implementations that I've seen copy always, instead of copying on write, whenever a transaction is started. Given the expected size ( 1GB) of the dictionary, I'm hoping to find something that COWs only when something is actually changed during a transaction. I'm also hoping for something that is packaged by most major GNU/Linux distributions. Any suggestions or links are very much appreciated.

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• How does the WP7 Pivot control dynamically load pivot items?

  - by mztan

  IIRC, the Pivot control only loads a child PivotItem if it is the currently shown child. I would then guess that the previously seen child is also somehow unloaded, presumably still stored in memory, but hidden from the UI. What I'm wondering is, how does the Pivot control dynamically load/unload a child control, and can that behavior be imitated within a custom UserControl? As for unloading, is it as simple as collapsing the previous child's visibility, or is something trickier going on? That is to say, supposing I use my own UserControl like: <my:CustomUserControl> <TextBlock x:Name="_textBlock" Text="wait for it ..." /> </my:CustomUserControl> Normally, the child TextBlock is instantiated when the surrounding PhoneApplicationPage is instantiated, via InitializeComponent and all that. Is there any way to postpone this behavior and load the child programmatically?

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• Which class will be instantiated

  - by Michael

  Say I have 2 subclasses from UIViewController, class A and class B. In Main nib file an object is representing class A and it is set to load file from Secondary nib file. The owner of Secondary nib is of class B. The question is - from which class an object in Main nib file will be instanciated once the nib files unarchived in the memory? The reason this question arised is that I have to take care myself if such reference to external NIB file present, to ensure that the first nib's object and second nib's owner is same. Please correct me if my statement is wrong.

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• Reaplaceing the Import Table in PE file by standart LoadLibrary...

  - by user308368

  Hello. I have an executable (PE) file that load a dll file as represented in the Import table... let say: PEFile.exe Modules.dll my question is how can i remove Modules.dll's import_descriptor from the imports and do its work by loadLibrary without the rely on the import table and without destroy the file???... My bigger problem his i could not understand exactly how the Import thing works... after the loader read the information he needs to do the import's thing, i believe he use the LoadLibrary, GetProcAddress APIs... but i couldn't understated what he doing with the pointers he get... he putting them somewhere in memory... and then what just call them?!? all the papers i found in the net explain the structure of the import table, but i didn't found a paper that explain how it is really work and get used... i hope you cold understand my Gibberish English... Thank you!

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• soft stoppped working

  - by Jack Morton

  this is might be really weird, but I have no idea what kinda wizardry of this. Basically, my Visual Studio stopped responding to my changes, it stopped building solution. I can comment code, which would completely ruin the logic of program, and Visual Studio will still run program that I guess it has in memory. It's really annoying, and I have no idea what it is. I keep restarting software, but it's still does the same. It's a licensed software. I was wondering If someone knew what was going on. Thanks!

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• Quick way to get an NSDictionary from an XML NSData representation?

  - by dontWatchMyProfile

  I've loaded an XML file as NSData into memory and parse over the elements using NSXMLParser. Although it works, it's a very ugly and hard to maintain code since there are about 150 different elements to parse. I know there are nice third-party solutions, but I want to keep it with the iPhone SDK for purpose of practice and fun. So I thought: Why not convert that XML file into an NSDictionary? Having this, I could use fast enumeration to go over the elements. Or is it just the same amount of ugly code needed to parse and process an XML right away with NSXMLParser? Would I build up an NSDictionary for every found node in the XML and create a huge one, containing the whole structure and data? Or is there an even simpler way?

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• Aptana Studio is opening but not ever closing a python.exe process

  - by SC Ghost

  I am developing a small testing website using Django 1.2 in Aptana Studio build 2.0.4.1268158907. I have a Django project that I test by running the command "runserver 8001" on my project. This command runs the project on a small server that comes with Django. However the problem arises that every time I run this command Aptana opens two instances of the process "python.exe". Upon terminating the command only one of these instances is ended. The other process continues to run and use memory. My server is not online, and the process doesn't seem to do anything that I can find. This happens every time i run the runserver command on my project and therefore more and more python.exe instances will open up through my development period. Any help discovering either the purpose of this extra python.exe or a way to prevent it from opening would be much appreciated.

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• How do I read UTF-8 characters via a pointer?

  - by Jen

  Suppose I have UTF-8 content stored in memory, how do I read the characters using a pointer? I presume I need to watch for the 8th bit indicating a multi-byte character, but how exactly do I turn the sequence into a valid Unicode character? Also, is wchar_t the proper type to store a single Unicode character? This is what I have in mind: wchar_t readNextChar (char** p) { char ch = *p++; if (ch & 128) { // This is a multi-byte character, what do I do now? // char chNext = *p++; // ... but how do I assemble the Unicode character? ... } ... }

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• What is tha CAUSE of Error 523 and Error 200 in Blackberry handhelds

  - by voipsecuritydigest.com

  I'm Blackberry developer, customers using my application experiencing Error 523 and Error 200. Remedies to those errors are in first case - remove application, my application. In second case totally reload OS! This is very bad, and customers blame me! But this is I don't do anything illegal to make blackberry crash. I just used a lot of memory, which is obvious because customer want that. Everywhere including Blackberry knowledge base people talking how to fix the problem, which may happened to everybody using application from well known brands, for example Yahoo! finances. But nobody explains what is the mechanism behind this, and if it is possible to avoid the problem. I would like to know what is that CAUSE of Error 523 and Error 200?

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• Object for storing strings geted from prints

  - by evg

  class MyWriter: def __init__(self, stdout): self.stdout = stdout self.dumps = [] def write(self, text): self.stdout.write(smart_unicode(text).encode('cp1251')) self.dumps.append(text) def close(self): self.stdout.close() writer = MyWriter(sys.stdout) save = sys.stdout sys.stdout = writer I use self.dumps list to store geted data from prints. Is it exists more convinient object for storing string lines in memory? ideally i want dump it to one big string. I can get it like this "\n".join(self.dumps) from code above. Mb it's better to just concat strings - self.dumps += text ?

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• Differences between extension methods in C#3 & 4

  - by Buh Buh

  I think I remember reading a long time ago that in C#3 extension methods could only be applied to primitive types and interfaces; and that in C#4 they could be used to extend any type. This doesn't seam to match up with what I am seeing now and I am finding it difficult to find this documented. Is there any truth to this or did my memory make it all up? What are the rules relating to which types can be extended? Are there any differences between C# 3 and 4?

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• Cache bandwidth per tick for modern CPUs

  - by osgx

  Hello What is a speed of cache accessing for modern CPUs? How many bytes can be read or written from memory every processor clock tick by Intel P4, Core2, Corei7, AMD? Please, answer with both theoretical (width of ld/sd unit with its throughput in uOPs/tick) and practical numbers (even memcpy speed tests, or STREAM benchmark), if any. PS it is question, related to maximal rate of load/store instructions in assembler. There can be theoretical rate of loading (all Instructions Per Tick are widest loads), but processor can give only part of such, a practical limit of loading.

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• Address of array vs. address of array[0] - C language

  - by user324994

  My question is why does the address of an array differ from the address of its first position? I'm trying to write my own malloc, but to start out I'm just allocating a chunk of memory and playing around with the addresses. My code looks roughly like this: #define BUFF_SIZE 1024 static char *mallocbuff; int main(){ mallocbuff = malloc(BUFF_SIZE); printf("The address of mallocbuff is %d\n", &mallocbuff); printf("The address of mallocbuff[0] is %d\n", &mallocbuff[0]); } &mallocbuff is the same address every time I run it. &mallocbuff[0] is some random address every time. I was expecting the addresses to match each other. Can anyone explain why this isn't the case?

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• Why does C++ allow variable length arrays that aren't dynamically allocated?

  - by Maulrus

  I'm relatively new to C++, and from the beginning it's been drilled into me that you can't do something like int x; cin >> x; int array[x]; Instead, you must use dynamic memory. However, I recently discovered that the above will compile (though I get a -pedantic warning saying it's forbidden by ISO C++). I know that it's obviously a bad idea to do it if it's not allowed by the standard, but I previously didn't even know this was possible. My question is, why does g++ allow variable length arrays that aren't dynamically allocated if it's not allowed by the standard? Also, if it's possible for the compiler to do it, why isn't it in the standard?

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• Fast, cross-platform timer?

  - by dsimcha

  I'm looking to improve the D garbage collector by adding some heuristics to avoid garbage collection runs that are unlikely to result in significant freeing. One heuristic I'd like to add is that GC should not be run more than once per X amount of time (maybe once per second or so). To do this I need a timer with the following properties: It must be able to grab the correct time with minimal overhead. Calling core.stdc.time takes an amount of time roughly equivalent to a small memory allocation, so it's not a good option. Ideally, should be cross-platform (both OS and CPU), for maintenance simplicity. Super high resolution isn't terribly important. If the times are accurate to maybe 1/4 of a second, that's good enough. Must work in a multithreaded/multi-CPU context. The x86 rdtsc instruction won't work.

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