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  • Are programming languages and methods inefficient? (assembler and C knowledge needed)

    - by b-gen-jack-o-neill
    Hi, for a long time, I am thinking and studying output of C language compiler in assembler form, as well as CPU architecture. I know this may be silly to you, but it seems to me that something is very ineffective. Please, don´t be angry if I am wrong, and there is some reason I do not see for all these principles. I will be very glad if you tell me why is it designed this way. I actually truly believe I am wrong, I know the genius minds of people which get PCs together knew a reason to do so. What exactly, do you ask? I´ll tell you right away, I use C as a example: 1: Stack local scope memory allocation: So, typical local memory allocation uses stack. Just copy esp to ebp and than allocate all the memory via ebp. OK, I would understand this if you explicitly need allocate RAM by default stack values, but if I do understand it correctly, modern OS use paging as a translation layer between application and physical RAM, when address you desire is further translated before reaching actual RAM byte. So why don´t just say 0x00000000 is int a,0x00000004 is int b and so? And access them just by mov 0x00000000,#10? Because you wont actually access memory blocks 0x00000000 and 0x00000004 but those your OS set the paging tables to. Actually, since memory allocation by ebp and esp use indirect addressing, "my" way would be even faster. 2: Variable allocation duplicity: When you run application, Loader load its code into RAM. When you create variable, or string, compiler generates code that pushes these values on the top o stack when created in main. So there is actual instruction for do so, and that actual number in memory. So, there are 2 entries of the same value in RAM. One in form of instruction, second in form of actual bytes in the RAM. But why? Why not to just when declaring variable count at which memory block it would be, than when used, just insert this memory location?

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  • Interchange structured data between Haskell and C

    - by Eonil
    First, I'm a Haskell beginner. I'm planning integrating Haskell into C for realtime game. Haskell does logic, C does rendering. To do this, I have to pass huge complexly structured data (game state) from/to each other for each tick (at least 30 times per second). So the passing data should be lightweight. This state data may laid on sequential space on memory. Both of Haskell and C parts should access every area of the states freely. In best case, the cost of passing data can be copying a pointer to a memory. In worst case, copying whole data with conversion. I'm reading Haskell's FFI(http://www.haskell.org/haskellwiki/FFICookBook#Working_with_structs) The Haskell code look specifying memory layout explicitly. I have a few questions. Can Haskell specify memory layout explicitly? (to be matched exactly with C struct) Is this real memory layout? Or any kind of conversion required? (performance penalty) If Q#2 is true, Any performance penalty when the memory layout specified explicitly? What's the syntax #{alignment foo}? Where can I find the document about this? If I want to pass huge data with best performance, how should I do that? *PS Explicit memory layout feature which I said is just C#'s [StructLayout] attribute. Which is specifying in-memory position and size explicitly. http://www.developerfusion.com/article/84519/mastering-structs-in-c/ I'm not sure Haskell has matching linguistic construct matching with fields of C struct.

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  • Are programming languages and methods ineffective? (assembler and C knowledge needed)

    - by b-gen-jack-o-neill
    Hi, for a long time, I am thinking and studying output of C language compiler in asemlber form, as well as CPU architecture. I know this may be silly to you, but it seems to me that something is very ineffective. Please, don´t be angry if I am wrong, and there is some reason I do not see for all these principles. I will be very glad if you tell me why is it designed this way. I actually trully believe I am wrong, I know the genius minds of people which get PCs together knew a reason to do so. What exactly, do you ask? I´ll tell you right away, I use C as a example: 1, Stack local scope memory allocation: So, typical local memory allocation uses stack. Just copy esp to ebp and than allocate all the memory via ebp. OK, I would understand this if you explicitly need allocate RAM by default stack values, but if I do understand it correctly, modern OS use paging as a translation layer between application and physical RAM, when adress you desire is further translated before reaching actuall RAM byte. So why don´t just say 0x00000000 is int a,0x00000004 is int b and so? And access them just by mov 0x00000000,#10? Becouse you wont actually access memory blocks 0x00000000 and 0x00000004 but those your OS set the paging tables to. Actually, since memory allocation by ebp and esp use indirect adressing, "my" way would be even faster. 2, Variable allocation duplicitly: When you run aaplication, Loader load its code into RAM. When you create variable, or string, compiler generates code that pushes these values on the top o stack when created in main. So there is actuall instruction for do so, and that actuall number in memory. So, there are 2 entries of the same value in RAM. One in fomr of instruction, second in form of actuall bytes in the RAM. But why? Why not to just when declaring variable count at which memory block it would be, than when used, just insert this memory location?

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  • iPhone: How to store a location (CLLocationCoordinate2D) inside a class w/o leaking memory?

    - by Henry
    I am creating a library which contains an API for setting the current location based off some value collected by the GPS. I want to store this location in my class and later, change the behavior of my library if it is set. What I had in mind was: @interface myLib { @property (nonatomic, retain) CLLocationCoordinate2D *location; } @implementation myLib { @synthesize location = _location; - (void)setLocation:(CLLocationCoordinate2D *)loc { location = loc; } - (void)someFunc { if (location != nil) ... } } However, retain isn't a valid property for a CLLocationCoordinate2D object. So, what is the proper way to save CLLocationCoordinate2D for later use w/o wasting memory? Thanks in advance!

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  • How to save the view count of a question in memory?

    - by Freewind
    My website is like stackoverflow, there are many questions. I want to record how many times a question has been visited. I have a column called "view_count" in the question table to save it. If a user visits a question many times, the view_count should be increased only 1. So I have to record which user has visited which question, and I think it is too much expensive to save this information in the database because the records will be huge. So, I would like to keep the information in memory and only persist the number to the database every 10 minutes. I have searched about "cache" in Rails, but I haven't found an example. I would like a simple sample of how to do this, thanks for help~

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  • How to the view count of a question in memory?

    - by Freewind
    My website is like stackoverflow, there are many questions. I want to record how many times a question has been visited. I have a column called "view_count" in the question table to save it. If a user visits a question many times, the view_count should be increased only 1. So I have to record which user has visited which question, and I think it is too much expensive to save this information in the database because the records will be huge. So, I would like to keep the information in memory and only persist the number to the database every 10 minutes. I have searched about "cache" in Rails, but I haven't found an example. I would like a simple sample of how to do this, thanks for help~

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  • Can the Windows Media Player COM control play AVI files from memory (instead of from a file)?

    - by MusiGenesis
    I have a C# app, and I'm looking at using the Windows Media Player COM control to play animation and audio. So far, the only way I see of programatically controlling what the control is playing is to set its URL property to point to some file (I assume there's some way to pass in a playlist). Is there any way the WMP can render an AVI that is entirely in-memory, like a MemoryStream or something? If so, can WMP skip from one AVI to the next seamlessly (i.e. no glitch in either the audio or the video as it transitions from one to the next)? If WMP only plays files, is there some way to cue up a list of the files in advance of play start? If so, can WMP be made to skip from one file to the next without a brief interruption? Any knowledge or links to knowledge would be much appreciated.

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  • Using Parallel Extensions with ThreadStatic attribute. Could it leak memory?

    - by the-locster
    I'm using Parallel Extensions fairly heavily and I've just now encountered a case where using thread locla storrage might be sensible to allow re-use of objects by worker threads. As such I was lookign at the ThreadStatic attribute which marks a static field/variable as having a unique value per thread. It seems to me that it would be unwise to use PE with the ThreadStatic attribute without any guarantee of thread re-use by PE. That is, if threads are created and destroyed to some degree would the variables (and thus objects they point to) remain in thread local storage for some indeterminate amount of time, thus causing a memory leak? Or perhaps the thread storage is tied to the threads and disposed of when the threads are disposed? But then you still potentially have threads in a pool that are longed lived and that accumulate thread local storage from various pieces of code the threads are used for. Is there a better approach to obtaining thread local storage with PE? Thankyou.

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  • How to implement a memory transaction scope in C#?

    - by theburningmonk
    Hi, we have a cache which I would like to put some transaction scopes around so that any process have to explicitly 'commit' the changes it wants to do to the cached objects and make it possible to rollback any changes when the process fails halfway as well. Right now, we're deep cloning the cached objects on get requests, it works but it's not a clean solution and involves a fair bit of maintenance too. I remember hearing about some MTS (memory transaction scope) solution on .NetRocks a while back but can't remember the name of it! Does anyone know of a good MTS framework out there? Alternatively, if I was to implement my own, are there any good guidelines/patterns on how to do this? Thanks,

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  • How to measure sum of collected memory of Young Generation?

    - by Marcel
    Hi, I'd like to measure memory allocation data from my java application, i.e. the sum of the size of all objects that were allocated. Since object allocation is done in young generation this seems to be the right place. I know jconsole and I know the JMX beans but I just can't find the right variable... Right at the moment we are parsing the gc log output file but that's quite hard. Ideally we'd like to measure it via JMX... How can I get this value? Thanks, Marcel

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  • Does `throw` cause stack variables (full types) to be freed from memory in C++?

    - by nbolton
    I'm pondering a question on Brainbench. I actually realised that I could answer my question easily by compiling the code, but it's an interesting question nonetheless, so I'll ask the question anyway and answer it myself shortly. Take a look at this snippet: The question considers what happens when we throw from a destructor (which causes terminate() to be called). It's become clear to me by asking the question that the memory is indeed freed and the destructor is called, but, is this before or after throw is called from foo? Perhaps the issue here is that throw is used while the stack is unwinding that is the problem... Actually this is slightly confusing.

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  • How to control the memory size of continuously running windows service?

    - by Snowill
    Hi, I have created a windows service which is continuously polling a database. For this purpose i have a timer in place. Ever time i am querying a database table i open a connection and close it immediately after my work is done. Right now i am doing this every 20 seconds for testing purpose, but later this time might increase to 5 - 10 minutes. What happens is everytime the database table is polled there is an increase of 10-12 KB in the size of the memory of the service running. This i can see in the task manager. Is there any way to control this.

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  • Does `throw` cause stack variables to be freed from memory in C++?

    - by nbolton
    I'm pondering a question on Brainbench. I actually realised that I could answer my question easily by compiling the code, but it's an interesting question nonetheless, so I'll ask the question anyway and answer it myself shortly. Take a look at this snippet: The question considers what happens when we throw from a destructor (which causes terminate() to be called). It's become clear to me by asking the question that the memory is indeed freed and the destructor is called, but, is this before or after throw is called from foo? Perhaps the issue here is that throw is used while the stack is unwinding that is the problem... Actually this is slightly confusing.

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  • Does lamda in List.ForEach leads to memory leaks and performance problems ?

    - by Monomachus
    I have a problem which I could solve using something like this sortedElements.ForEach((XElement el) => PrintXElementName(el,i++)); And this means that I have in ForEach a lambda which permits using parameters like int i. I like that way of doing it, but i read somewhere that anonymous methods and delegates with lambda leads to a lot of memory leaks because each time when lambda is executed something is instantiated but is not released. Something like that. Could you please tell me if this is true in this situation and if it is why?

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  • Count of memory copies in *nix systems between packet at NIC and user application?

    - by Michael_73
    Hi there, This is just a general question relating to some high-performance computing I've been wondering about. A certain low-latency messaging vendor speaks in its supporting documentation about using raw sockets to transfer the data directly from the network device to the user application and in so doing it speaks about reducing the messaging latency even further than it does anyway (in other admittedly carefully thought-out design decisions). My question is therefore to those that grok the networking stacks on Unix or Unix-like systems. How much difference are they likely to be able to realise using this method? Feel free to answer in terms of memory copies, numbers of whales rescued or areas the size of Wales ;) Their messaging is UDP-based, as I understand it, so there's no problem with establishing TCP connections etc. Any other points of interest on this topic would be gratefully thought about! Best wishes, Mike

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  • Any strategies for assessing the trade-off between CPU loss and memory gain from compression of data

    - by indiehacker
    Are very large TextProperties a burden? Should they be compressed? Say I have a information stored in 2 attributes of type TextProperty in my datastore entities. The strings are always the same length of 65,000 characters and have lots of repeating integers, a sample appearing as follows: entity.pixel_idx = 0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,5,5,5,5,5,5,5,5,5,5,5,5....etc. entity.pixel_color = 2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,1,1,1,1,1,1,1,1,1,1,1,1,...etc. So these above could also be represented using much less storage memory by compressing say using only each integer and the length of its series ( '0,8' for '0,0,0,0,0,0,0,0') but then its takes time and CPU to compress and decompress? Any general ideas? Are there some tricks for testing different attempts to the problem?

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  • Where could I get the information about the in-memory layout info of .NET Object Model?

    - by smwikipedia
    I want to know the in-memory representation of .NET constructs such as "interface", "class", "struct", etc. There's an excellent book for C++ object model - <Inside the C++ Object Model by Stanley. Lippman, I want a similar book for .NET and C#. Could someone provide some hints about books and articles? I have read about the "Drill Into .NET Framework Internals to See How the CLR Creates Runtime Objects" Anything more? If this info is not publicly avaialble. Shared source one like Mono or Shared Source CLI could be an option. Many thanks.

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  • Getting Memory allocation problem at UIBarButtonItem in Iphone sdk.

    - by monish
    Hi guys, Here I am getting memory allocation problem at UIBarButtonItem and the related code for that is: toolbar = [UIToolbar new]; toolbar.barStyle = UIBarStyleBlackOpaque; [toolbar setFrame:CGRectMake(0, 350,320,20)]; [self.view addSubview:toolbar]; UIBarButtonItem* barItem1 = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:self action:@selector(categoryConfig:)] ; rightBarItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemBookmarks target:self action:@selector(dialogOtherAction:)] ; UIBarButtonItem* barItem2 = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:self action:@selector(categoryConfig:)] ; NSArray *items = [NSArray arrayWithObjects: barItem1,rightBarItem,barItem2, nil]; [barItem1 release]; [barItem2 release]; [rightBarItem release]; [toolbar setItems:items animated:NO]; after adding UIBarButtonItems into the array items I released them.even though its showing allocations at barbuttons. can any help me for this? Thank you, Monish.

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  • How can a class's memory-allocated address be determined from within the contructor?

    - by Jim Fell
    Is it possible to get the memory-allocated address of a newly instantiated class from within that class's constructor during execution of said constructor? I am developing a linked list wherein multiple classes have multiple pointers to like classes. Each time a new class instantiates, it needs to check its parent's list to make sure it is included. If I try to do something like this: MyClass() // contructor { extern MyClass * pParent; for ( int i = 0; i < max; i++ ) { pParent->rels[i] == &MyClass; // error } } I get this error: error C2275: 'namespace::MyClass' : illegal use of this type as an expression Any thoughts or suggestions would be appreciated. Thanks.

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  • Is there any way to store full size image returned from camera activity in internal memory ?

    - by SimpleGuy
    I am using Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE); intent.putExtra(MediaStore.EXTRA_OUTPUT,Uri.fromFile(externalFileObj)); intent to call default camera activity. To get full image you need to specify intent.putExtra(). But this always requires URI that works only for external storage files. I tried to create a temp.jpg image in internal memory and pass its URI Uri.fromFile(new File(getFilesDir() + "/temp.jpg")); but the camera activity won't return back after the image is captured. So there is no way to get Full size image from default camera application in our activity without using any external storage ? Assuming that the device do not have SD card or currently in use is there no way I can avoid using it ? Yes I know we can create our own camerapreview surface but I want to use the default camera application as it is natural with many more options. Thanks.

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  • Core Data strategy using in memory cache, or no core data at all?

    - by randombits
    I have a user interface where the user can check off a bunch of items from a tableview, almost like a todo list. The items are populated from a Core Data stack. I need to be able to take all of the items they're clicking through and put them into a "temporary" shopping cart. Once they're in the shopping cart, users can go through the list and remove the items, or just submit them to a server. The thing is, the selected items are temporary just like an internet based shopping cart. It's nothing something that gets persisted once the application closes. Once the view is no longer in display, I can assume that the shopping cart is safe to discard. What's the best way to approach this? Since the user is essentially clicking on instances that map back to a Core Data entity .. should I setup a different persistence store such as in memory and add that store to my managed object context?

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  • How do game trainers change an address in memory that's dynamic?

    - by GameTrainersWTF
    Lets assume I am a game and I have a global int* that contains my health. A game trainer's job is to modify this value to whatever in order to achieve god mode. I've looked up tutorials on game trainers to understand how they work, and the general idea is to use a memory scanner to try and find the address of a certain value. Then modify this address by injecting a dll or whatever. But I made a simple program with a global int* and its address changes every time I run the app, so I don't get how game trainers can hard code these addresses? Or is my example wrong? What am I missing?

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  • How do game trainers change a address in memory thats dynamic?

    - by GameTrainersWTF
    Lets assume i am a game and i have a global int* that contains my health. A game trainers job is to modify this value to whatever in order to achieve god mode. I've looked up tutorials on game trainers to understand how they work, and the general idea is to use a memory scanner to try and find the address of a certain value. Then modify this address by injecting a dll or whatever. But i made a simple program with a global int* and its address changes every time i run the app, so i don't get how game trainers can hard code these addresses? Or is my example wrong? What am i missing?

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  • Need data on disk drive management by OS: getting base I/O unit size, “sync” option, Direct Memory A

    - by Richard T
    Hello All, I want to ensure I have done all I can to configure a system's disks for serious database use. The three areas I know of (any others?) to be concerned about are: I/O size: the database engine and disk's native size should either match, or the database's native I/O size should be a multiple of the disk's native I/O size. Disks that are capable of Direct Memory Access (eg. IDE) should be configured for it. When a disk says it has written data persistently, it must be so! No keeping it in cache and lying about it. I have been looking for information on how to ensure these are so for CENTOS and Ubuntu, but can't seem to find anything at all! I want to be able to check these things and change them if needed. Any and all input appreciated.

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  • How to get the entire code of a method in memory so I can calculate its hash at runtime?

    - by bejo
    Hello stackoverflow, How to get the entire code of a method in memory so I can calculate its hash at runtime? I need to make a function like this: type TProcedureOfObject = procedure of object; function TForm1.CalculateHashValue (AMethod: TProcedureOfObject): string; var MemStream: TMemoryStream; begin result:=''; MemStream:=TMemoryStream.Create; try //how to get the code of AMethod into TMemoryStream? result:=MD5(MemStream); //I already have the MD5 function finally MemStream.Free; end; end; I use Delphi 7. Thank you.

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