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  • Memory allocation in case of static variables

    - by eSKay
    I am always confused about static variables, and the way memory allocation happens for them. For example: int a = 1; const int b = 2; static const int c = 3; int foo(int &arg){ arg++; return arg; } How is the memory allocated for a,b and c? What is the difference (in terms of memory) if I call foo(a), foo(b) and foo(c)?

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  • Is there an NSCFTimer memory leak?

    - by mystify
    I tracked down a memory leak with instruments. I always end up with the information that the responsible library is Foundation. When I track that down in my code, I end up here, but there's nothing wrong with my memory management: - (void)setupTimer { // stop timer if still there [self stopAnimationTimer]; NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:0.2 target:self selector:@selector(step:) userInfo:nil repeats:YES]; self.animationTimer = timer; // retain property, -release in -dealloc method } the property animationTimer is retaining the timer. In -dealloc I -release it. Now that looks like a framework bug? I checked with iPhone OS 3.0 and 3.1, both have that problem every time I use NSTimer like this. Any idea what else could be the problem? (my memory leak scan interval was 0.1 seconds. but same thing with 5 seconds)

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  • UIWebView memory management

    - by wolfrevo
    Hello, I have a problem with memory management. I am developing an application that makes heavy use of UIWebView. This app generates dynamically lots of UIWebViews while loading content from my server. Some of these UIWebViews are quite large and have a lot of pictures. If I use instruments to detect leaks, I do not detect any. However, lots of objects are allocated and I suspect that has to do with the UIWebViews. When the webviews release because no longer needed, it appears that not all memory is released. I mean, after a request to my server the app creates an UITableView and many webviews (instruments say about 8Mb). When user tap back, all of them are released but memory usage only decrements about 2-3 Mb, and after 5-10 minutes using the app it crashes. Am I missing something? Anyone know what could be happening? Thank you!

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  • Does it take time to deallocate memory?

    - by jm1234567890
    I have a C++ program which, during execution, will allocate about 3-8Gb of memory to store a hash table (I use tr1/unordered_map) and various other data structures. However, at the end of execution, there will be a long pause before returning to shell. For example, at the very end of my main function I have std::cout << "End of execution" << endl; But the execution of my program will go something like $ ./program do stuff... End of execution [long pause of maybe 2 min] $ -- returns to shell Is this expected behavior or am I doing something wrong? I'm guessing that the program is deallocating the memory at the end. But, commercial applications which use large amounts of memory (such as photoshop) do not exhibit this pause when you close the application. Please advise :)

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  • How does VirtualBox's memory usage work?

    - by DrFredEdison
    I've been running several VM's with VirtualBox, and the memory usage reported from various perspectives, and I'm having trouble figuring how much memory my VMs actually use. Here is an example: I have a VM running Windows 7 (as the Guest OS) on my windows XP Host machine. The Host Machine Has 3 GB of RAM The Guest VM is setup to have a base memory of 1 GB If I run Task Manger on the Guest OS, I see memory usage of 430 MB If I run Task Manger on the host OS, I see 3 processes that seem to belong to VirtualBox: VirtualBox.exe (1), using 60 MB of memory (This one seems to have the most CPU usage) VirtualBox.exe (2), using 20 MB of memory VBoxSvc.exe, using 11.5 MB of memory While running the VM, the Host OS's memory usage is about 2 GB When I shut down the VM, the Host OS's it goes back to memory usage goes down to about 900 MB So clearly, there are some huge differences here. I really don't understand how the GuestOS can use 400+ MB, while the Host OS only shows about 75 MB allocated to the VM. Are there other processes used by VirtualBox that aren't as obviously named? Also, I'd like to know if I run a machine with 1 GB, is that going to take 1 GB away from my host OS, or only the amount of memory the Guest machine is currently using? update Somene expressed distrust over my memory usage numbers, and I'm not sure if that distrust was directed at me, or my Host OS's Task Manager's reporting (which is perhaps the culprit), but for any skeptics, here is a screenshot of those processes on the host machine:

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  • Bios Memory settings and Virtualization + Ubuntu (Unofficial Answers Welcome) [closed]

    - by TardisGuy
    Attempting to optimize my (Main Windowless) Ubuntu system for my uses I will detail questions below, I understand this might be the wrong place to ask these questions. If so, my apologies and I thank you so much for your patience. Thanks to all the volenteers that have helped me learn ubuntu over the years (Since 5.10) This is a "short" list of questions I have been trying to figure out for some time. If you feel you can answer one but not another, that's already more than I could ask for. I have wrote this up in a format for easy navigation to important points Hopefully to less annoy your eyes. You're welcome :) or i'm sorry i annoy you. :( If you would be so kind, Please format answers as follows: question 1: _ _ _ _ _ or question 1-a: _ _ _ _ _ If you want to simply link me to relevant information, rather than type up something really detailed; that would be more than awesome! Memory Specific Questions Goal: Maximizing memory bandwith to better perform in Virtualization, and Large file compression. (Possible conflict?) Ganged vs Unganged "which is better?"** is relative, i know. But what about ganged vs unganged - With or without Bank/channel interleaving? a: Speculation - If i understand correctly, "channel interleaving has something to do with using both channels to read or write in a kind of "striping" pattern, as opposed to a standard half duplex operation.(probably wrong) but wouldn't ganged channels make this irrelevant? Memory Interleaving(bank). Does it have a down side? Does it require a ratio of clocks? (If I run 4x4gig ddr3) a. If im reading correctly(trying to learn), this is designed to spread operations between latency cycles to work around the higher latency of "normal" operation. b. However it seems to me that it has to be: divisible by fractions of a master clock? So if i run memory at 1333mhz, then the mean between 2 (physical) banks would operate every (roughly) 600Mhz? Warning! Possibly utter nonsense: (1333/2 interleaving to act like 1 memory module per 2 sticks of a total of 4 sticks, meaning 2x channels@4) c. which makes me wonder if there would be left over clock cycles the system would have to... "truncate/balance" or something? But I'm certain theres a feature somewhere i don't understand. Virtualization Questions AMD-V - Option of IOMMU Turned it on, why do i have extra option of "64MB"? If IOMMU is on, but "64MB" is "disabled", Is it on? (have scoured google, I still dont know) a. I think i understand that its supposed to (kind of) "set aside" a part of ram to act as a faster interactive zone for "stuff" (usb, Graphics, and... what?) b. I am using Nvidia graphics on AMD (Used kernel option "iommu=pt iommu=1, pt "passthrough"? No idea what they do, found it on google to solve boot up issue) c. Will this option help me use low latency sound hardware, like my midi keyboard? Can you recommend any additional tweaks? a. sysctl settings? b. swap settings? Grats, youve reached the end. Thanks for Reading.

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  • XNA WP7 Texture memory and ContentManager

    - by jlongstreet
    I'm trying to get my WP7 XNA game's memory under control and under the 90MB limit for submission. One target I identified was UI textures, especially fullscreen ones, that would never get unloaded. So I moved UI texture loads to their own ContentManager so I can unload them. However, this doesn't seem to affect the value of Microsoft.Phone.Info.DeviceExtendedProperties.GetValue("ApplicationCurrentMemoryUsage"), so it doesn't look like the memory is actually being released. Example: splash screens. In Game.LoadContent(): Application.Instance.SetContentManager("UI"); // set the current content manager for (int i = 0; i < mSplashTextures.Length; ++i) { // load the splash textures mSplashTextures[i] = Application.Instance.Content.Load<Texture2D>(msSplashTextureNames[i]); } // set the content manager back to the global one Application.Instance.SetContentManager("Global"); When the initial load is done and the title screen starts, I do: Application.Instance.GetContentManager("UI").Unload(); The three textures take about 6.5 MB of memory. Before unloading the UI ContentManager, I see that ApplicationCurrentMemoryUsage is at 34.29 MB. After unloading the ContentManager (and doing a full GC.Collect()), it's still at 34.29 MB. But after that, I load another fullscreen texture (for the title screen background) and memory usage still doesn't change. Could it be keeping the memory for these textures allocated and reusing it? edit: very simple test: protected override void LoadContent() { // Create a new SpriteBatch, which can be used to draw textures. spriteBatch = new SpriteBatch(GraphicsDevice); PrintMemUsage("Before texture load: "); // TODO: use this.Content to load your game content here red = this.Content.Load<Texture2D>("Untitled"); PrintMemUsage("After texture load: "); } private void PrintMemUsage(string tag) { Debug.WriteLine(tag + Microsoft.Phone.Info.DeviceExtendedProperties.GetValue("ApplicationCurrentMemoryUsage")); } protected override void Update(GameTime gameTime) { // Allows the game to exit if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed) this.Exit(); // TODO: Add your update logic here if (count++ == 100) { GC.Collect(); GC.WaitForPendingFinalizers(); PrintMemUsage("Before CM unload: "); this.Content.Dispose(); GC.Collect(); GC.WaitForPendingFinalizers(); PrintMemUsage("After CM unload: "); red = null; spriteBatch.Dispose(); GC.Collect(); GC.WaitForPendingFinalizers(); PrintMemUsage("After SpriteBatch Dispose(): "); } base.Update(gameTime); } protected override void Draw(GameTime gameTime) { GraphicsDevice.Clear(Color.CornflowerBlue); // TODO: Add your drawing code here if (red != null) { spriteBatch.Begin(); spriteBatch.Draw(red, new Vector2(0,0), Color.White); spriteBatch.End(); } base.Draw(gameTime); } This prints something like (it changes every time): Before texture load: 7532544 After texture load: 10727424 Before CM unload: 9875456 After CM unload: 9953280 After SpriteBatch Dispose(): 9953280

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  • What is the maximum memory a process (MySQL) can consume on a 32-bit OS?

    - by mmattax
    I have MySQL running on a 32-bit RHEL box. The server itself has 4GB total memory with 2GB allocated to MySQL. I would like to know the max amount of memory I can put in the box and how much of that I can allocate to MySQL. I have heard both 2GB and 4GB as the per-process-limit on a 32-bit OS... Ultimately I'd like to know if I can increase the memory for MySQL without upgrading to a 64-bit OS.

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  • The Hot-Add Memory Hogs

    - by Andrew Clarke
    One of the more difficult tasks, when virtualizing a server, is to determine the amount of memory that Hypervisor should assign to the virtual machine. This requires accurate monitoring and, because of the consequences of setting the value too low, there is a great temptation to err on the side of over-provisioning. This results in fewer guest VMs and, in fact, with more accurate memory provisioning, many virtual environments could support 30% more VMs. In order to achieve a better consolidation (aka VM density) ratio, Windows Server 2008 R2 SP1 has introduced what Microsoft calls ‘Dynamic Memory’. This means that the start-up RAM VM memory assigned to guest virtual machines can be allowed to vary according to demand, changing dynamically while the VM is running, based on the workload of applications running inside. If demand outstrips supply, then memory can be rationed according to the ‘memory weight’ assigned to the guest VM. By this mechanism, memory becomes a shared resource that can be reallocated automatically as demand patterns vary. Unlike VMWare’s Memory Overcommit technology, the sum of all the memory allocations to each virtual machine will not exceed the total memory of the host computer. This is fine for applications that are self-regulating in their demands for memory, releasing memory back into the 'pool' when not under peak load. Other applications however, such as SQL Server Standard and Enterprise, are by nature, memory hogs under high workload; they can grab hot-add memory whilst running under load and then never release it. This requires more careful setting-up and the SQLOS team have provided some guidelines from for configuring SQL Server in virtual environments. Whereas VMWare’s Memory Overcommit is well-proven in a number of different configurations, Hyper-V’s ‘Dynamic Memory’ is new. So far, the indications are that it will improve the business case for virtualizing and it is probably a far more intuitive technology for the average IT professional to grasp. It is certainly worth testing to see whether it works for you.

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  • Python memory leaks

    - by Fragsworth
    I have a long-running script which, if let to run long enough, will consume all the memory on my system. Without going into details about the script, I have two questions: Are there any "Best Practices" to follow, which will help prevent leaks from occurring? What techniques are there to debug memory leaks in Python?

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  • SQL SERVER – Weekly Series – Memory Lane – #050

    - by Pinal Dave
    Here is the list of selected articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2007 Executing Remote Stored Procedure – Calling Stored Procedure on Linked Server In this example we see two different methods of how to call Stored Procedures remotely.  Connection Property of SQL Server Management Studio SSMS A very simple example of the how to build connection properties for SQL Server with the help of SSMS. Sample Example of RANKING Functions – ROW_NUMBER, RANK, DENSE_RANK, NTILE SQL Server has a total of 4 ranking functions. Ranking functions return a ranking value for each row in a partition. All the ranking functions are non-deterministic. T-SQL Script to Add Clustered Primary Key Jr. DBA asked me three times in a day, how to create Clustered Primary Key. I gave him following sample example. That was the last time he asked “How to create Clustered Primary Key to table?” 2008 2008 – TRIM() Function – User Defined Function SQL Server does not have functions which can trim leading or trailing spaces of any string at the same time. SQL does have LTRIM() and RTRIM() which can trim leading and trailing spaces respectively. SQL Server 2008 also does not have TRIM() function. User can easily use LTRIM() and RTRIM() together and simulate TRIM() functionality. http://www.youtube.com/watch?v=1-hhApy6MHM 2009 Earlier I have written two different articles on the subject Remove Bookmark Lookup. This article is as part 3 of original article. Please read the first two articles here before continuing reading this article. Query Optimization – Remove Bookmark Lookup – Remove RID Lookup – Remove Key Lookup Query Optimization – Remove Bookmark Lookup – Remove RID Lookup – Remove Key Lookup – Part 2 Query Optimization – Remove Bookmark Lookup – Remove RID Lookup – Remove Key Lookup – Part 3 Interesting Observation – Query Hint – FORCE ORDER SQL Server never stops to amaze me. As regular readers of this blog already know that besides conducting corporate training, I work on large-scale projects on query optimizations and server tuning projects. In one of the recent projects, I have noticed that a Junior Database Developer used the query hint Force Order; when I asked for details, I found out that the basic concept was not properly understood by him. Queries Waiting for Memory Allocation to Execute In one of the recent projects, I was asked to create a report of queries that are waiting for memory allocation. The reason was that we were doubtful regarding whether the memory was sufficient for the application. The following query can be useful in similar cases. Queries that do not have to wait on a memory grant will not appear in the result set of following query. 2010 Quickest Way to Identify Blocking Query and Resolution – Dirty Solution As the title suggests, this is quite a dirty solution; it’s not as elegant as you expect. However, it works totally fine. Simple Explanation of Data Type Precedence While I was working on creating a question for SQL SERVER – SQL Quiz – The View, The Table and The Clustered Index Confusion, I had actually created yet another question along with this question. However, I felt that the one which is posted on the SQL Quiz is much better than this one because what makes that more challenging question is that it has a multiple answer. Encrypted Stored Procedure and Activity Monitor I recently had received questionable if any stored procedure is encrypted can we see its definition in Activity Monitor.Answer is - No. Let us do a quick test. Let us create following Stored Procedure and then launch the Activity Monitor and check the text. Indexed View always Use Index on Table A single table can have maximum 249 non clustered indexes and 1 clustered index. In SQL Server 2008, a single table can have maximum 999 non clustered indexes and 1 clustered index. It is widely believed that a table can have only 1 clustered index, and this belief is true. I have some questions for all of you. Let us assume that I am creating view from the table itself and then create a clustered index on it. In my view, I am selecting the complete table itself. 2011 Detecting Database Case Sensitive Property using fn_helpcollations() I received a question on how to determine the case sensitivity of the database. The quick answer to this is to identify the collation of the database and check the properties of the collation. I have previously written how one can identify database collation. Once you have figured out the collation of the database, you can put that in the WHERE condition of the following T-SQL and then check the case sensitivity from the description. Server Side Paging in SQL Server CE (Compact Edition) SQL Server Denali is coming up with new T-SQL of Paging. I have written about the same earlier.SQL SERVER – Server Side Paging in SQL Server Denali – A Better Alternative,  SQL SERVER – Server Side Paging in SQL Server Denali Performance Comparison, SQL SERVER – Server Side Paging in SQL Server Denali – Part2 What is very interesting is that SQL Server CE 4.0 have the same feature introduced. Here is the quick example of the same. To run the script in the example, you will have to do installWebmatrix 4.0 and download sample database. Once done you can run following script. Why I am Going to Attend PASS Summit Unite 2011 The four-day event will be marked by a lot of learning, sharing, and networking, which will help me increase both my knowledge and contacts. Every year, PASS Summit provides me a golden opportunity to build my network as well as to identify and meet potential customers or employees. 2012 Manage Help Settings – CTRL + ALT + F1 This is very interesting read as my daughter once accidently came across a screen in SQL Server Management Studio. It took me 2-3 minutes to figure out how she has created the same screen. Recover the Accidentally Renamed Table “I accidentally renamed table in my SSMS. I was scrolling very fast and I made mistakes. It was either because I double clicked or clicked on F2 (shortcut key for renaming). However, I have made the mistake and now I have no idea how to fix this. If you have renamed the table, I think you pretty much is out of luck. Here are few things which you can do which can give you an idea about what your table name can be if you are lucky. Identify Numbers of Non Clustered Index on Tables for Entire Database Here is the script which will give you numbers of non clustered indexes on any table in entire database. Identify Most Resource Intensive Queries – SQL in Sixty Seconds #029 – Video Here is the complete complete script which I have used in the SQL in Sixty Seconds Video. Thanks Harsh for important Tip in the comment. http://www.youtube.com/watch?v=3kDHC_Tjrns Advanced Data Quality Services with Melissa Data – Azure Data Market For the purposes of the review, I used a database I had in an Excel spreadsheet with name and address information. Upon a cursory inspection, there are miscellaneous problems with these records; some addresses are missing ZIP codes, others missing a city, and some records are slightly misspelled or have unparsed suites. With DQS, I can easily add a knowledge base to help standardize my values, such as for state abbreviations. But how do I know that my address is correct? Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Allocated memory address clash

    - by Louis
    Hi, i don't understand how this happen. This is portion of my code.. int isGoal(Node *node, int startNode){ int i; . . } When i debug this using gdb i found out that 'i' was allocated at the memory address that have been previously allocated. (gdb)print &node->path->next $26 = (struct intNode **) 0xffbff2f0 (gdb) print &i $22 = (int *) 0xffbff2f0 node-path-next has been already defined outside this function. But as u can see they share the same address which at some point make the pointer point to another place when the i counter is changed. I compiled it using gcc on solaris platform Any helps would be really appreciated..

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  • Report Direct3D memory usage

    - by Jazz
    I have a Direct3D 9 application and I would like to monitor the memory usage. Is there a tool to know how much system and video memory is used by Direct3D? Ideally, it would also report how much is allocated for textures, vertex buffers, index buffers...

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  • Memory layout of executable

    - by Ross
    Hi all, When loading an executable then segments like the code, data, bss and so on need to be placed in memory. I am just wondering, if someone could tell me where on a standard x86 for example the libc library is placed. Is that at the top or bottom of memory. My guess is at the bottom, close to the application code, ie., that would look something like this here: --------- 0x1000 Stack | V ^ | Heap ---------- Data + BSS ---------- App Code ---------- libc ---------- 0x0000 Thanks a lot, Ross

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  • Help Finding Memory Leak

    - by Neal L
    Hi all, I am writing an iPad app that downloads a rather large .csv file and parses the file into objects stored in Core Data. The program keeps crashing, and I've run it along with the Allocations performance tool and can see that it's eating up memory. Nothing is alloc'ed or init'ed in the code, so why am I gobbling up memory? Code at: http://pastie.org/955960 Thanks! -Neal

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  • Please help with iPhone Memory & Images, memory usage crashing app

    - by Andrew Gray
    I have an issue with memory usage relating to images and I've searched the docs and watched the videos from cs193p and the iphone dev site on memory mgmt and performance. I've searched online and posted on forums, but I still can't figure it out. The app uses core data and simply lets the user associate text with a picture and stores the list of items in a table view that lets you add and delete items. Clicking on a row shows the image and related text. that's it. Everything runs fine on the simulator and on the device as well. I ran the analyzer and it looked good, so i then starting looking at performance. I ran leaks and everything looked good. My issue is when running Object Allocations as every time i select a row and the view with the image is shown, the live bytes jumps up a few MB and never goes down and my app eventually crashes due to memory usage. Sorting the live bytes column, i see 2 2.72MB mallocs (5.45Mb total), 14 CFDatas (3.58MB total), 1 2.74MB malloc and everything else is real small. the problem is all the related info in instruments is really technical and all the problem solving examples i've seen are just missing a release and nothing complicated. Instruments shows Core Data as the responsible library for all but one (libsqlite3.dylib the other) with [NSSQLCore _prepareResultsFromResultSet:usingFetchPlan:withMatchingRows:] as the caller for all but one (fetchResultSetReallocCurrentRow the other) and im just not sure how to track down what the problem is. i've looked at the stack traces and opened the last instance of my code and found 2 culprits (below). I havent been able to get any responses at all on this, so if anyone has any tips or pointers, I'd really appreciate it!!!! //this is from view controller that shows the title and image - (void)viewWillAppear:(BOOL)animated { [super viewWillAppear:animated]; self.title = item.title; self.itemTitleTextField.text = item.title; if ([item.notes length] == 0) { self.itemNotesTextView.hidden = YES; } else { self.itemNotesTextView.text = item.notes; } //this is the line instruments points to UIImage *image = item.photo.image; itemPhoto.image = image; } - (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath { if (editingStyle == UITableViewCellEditingStyleDelete) { // Delete the managed object for the given index path NSManagedObjectContext *context = [fetchedResultsController managedObjectContext]; [context deleteObject:[fetchedResultsController objectAtIndexPath:indexPath]]; // Save the context. NSError *error = nil; if (![context save:&error]) //this is the line instruments points to { NSLog(@"Unresolved error %@, %@", error, [error userInfo]); exit(-1); } } }

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  • Freeing memory twice

    - by benjamin button
    Hi, AFAIK, freeing a NULL pointer will result in nothing. I mean nothing is being done by the compiler/no functionality is performed. Still, I do see some statements where people say that one of the scenarios where memory corruption can occur is "freeing memory twice"? Is this still true?

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  • Simulate memory warnings from the code, possible?

    - by krasnyk
    I know i can simulate a memory warning on the simulator by selecting 'Simulate Memory Warning' from the drop down menu of the iPhone Simulator. I can even make a hot key for that. But this is not what I'd like to achieve. I'd like to do that from the code by simply, lets say doing it every 5 seconds. Is that possible?

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  • Available memory for iPhone OS app

    - by hgpc
    Is there a function or constant defining the amount of available memory for an app in iPhone OS? I'm looking for a device-independent way (iPod touch, iPhone, iPad) to know how much memory the app has left.

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  • No more memory available in Mathematica, Fit the parameters of system of differential equation

    - by user1058051
    I encountered a memory problem in Mathematica, when I tried to process my experimental data. It's a system of two differential equations and I need to find most suitable parameters. Unfortunately I am not a Pro in Mathematica, so the program used a lot of memory, when the parameter epsilon is more than 0.4. When it less than 0.4, the program work properly. The command 'historylength = 0' and attempts to reduce the Accuracy Goal and WorkingPrecision didn`t help. I can't use ' clear Cache ', because there isnt a circle. I'm trying to understand what mistakes I made, and how I may limit the memory usage. I have already bought extra-RAM, now its 4GB, and now I haven't free memory-slots in motherboard Remove["Global`*"]; T=13200; L = 0.085; e = 0.41; v = 0.000557197; q = 0.1618; C0 = 0.0256; R = 0.00075; data = {{L,600,0.141124587},{L,1200,0.254134509},{L,1800,0.342888644}, {L,2400,0.424476295},{L,3600,0.562844542},{L,4800,0.657111356}, {L,6000,0.75137817},{L,7200,0.815876516},{L,8430,0.879823594}, {L,9000,0.900771775},{L,13200,1}}; model[(De_)?NumberQ, (Kf_)?NumberQ, (Y_)?NumberQ] := model[De, Kf, Y] = yeld /.Last[Last[ NDSolve[{ v (Ci^(1,0))[z,t]+(Ci^(0,1))[z,t]== -((3 (1-e) Kf (Ci[z,t]-C0))/ (R e (1-(R Kf (1-R/r[z,t]))/De))), (r^(0,1))[z,t]== (R^2 Kf (Ci[z,t]-C0))/ (q r[z,t]^2 (1-(R Kf (1-R/r[z,t]))/De)), (yeld^(0,1))[z,t]== Y*(v e Ci[z,t])/(L q (1-e)), r[z,0]==R, Ci[z,0]==0, Ci[0,t]==0, yeld[z,0]==0}, {r[z,t],Ci[z,t],yeld},{z,0,L},{t,0,T}]]] fit = FindFit[data, {model[De, Kf, Y][z, t], {Y > 0.97, Y < 1.03, Kf > 10^-6, Kf < 10^-4, De > 10^-13, De < 10^-9}}, {{De,7*10^-13}, {Kf, 10^-5}, {Y, 1}}, {z, t}, Method -> NMinimize] data = {{600,0.141124587},{1200,0.254134509},{1800,0.342888644}, {2400,0.424476295},{3600,0.562844542},{4800,0.657111356}, {6000,0.75137817},{7200,0.815876516},{8430,0.879823594}, {9000,0.900771775},{13200,1}}; YYY = model[ De /. fit[[1]], Kf /. fit[[2]], Y /. fit[[3]]]; Show[Plot[Evaluate[YYY[L,t]],{t,0,T},PlotRange->All], ListPlot[data,PlotStyle->Directive[PointSize[Medium],Red]]] the link on the .nb file http://www.4shared.com/folder/249TSjlz/_online.html

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  • How to guard against memory leaks?

    - by just_wes
    I was recently interviewing for a C++ position, and I was asked how I guard against creating memory leaks. I know I didn't give a satisfactory answer to that question, so I'm throwing it to you guys. What are the best ways to guard against memory leaks? Thanks!

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  • Logging IP address for uniqueness without storing the IP address itself for privacy

    - by szabgab
    In a web application when logging some data I'd like to make sure I can identify data that came at differetn times but from the same IP address. On the other hand for privacy concerns as the data will be released publicly I'd like to make sure the actual IP cannot be retrieved. So I need some one way mapping of the IP addresses to some other strings that ensures 1-1 mapping. If I understand correctly then MD5, SHA1 or SHA256 could be a solution. I wonder if they are not too expensive in terms of processing needed? I'd be interested in any solution though if there is implementation in Perl that would be even better.

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