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• Database sharing/versioning

  - by DarkJaff

  Hi everyone, I have a question but I'm not sure of the word to use. My problem: I have an application using a database to stock information. The database can ben in access (local) or in a server (SQL Server or Oracle). We support these 3 kind of database. We want to give the possibility to the user to do what I think we can call versioning. Let me explain : We have a database 1. This is the master. We want to be able to create a database 2 that will be the same thing as database 1 but we can give it to someone else. They each work on each other side, adding, modifying and deleting records on this very complex database. After that, we want the database 1 to include the change from database 2, but with the possibility to dismiss some of the change. For you information, ou application is already multiuser so why don't we just use this multi-user and forget about this versionning? It's because sometimes, we need to give a copy of the database to another company on another site and they can't connect on our server. They work on their side and then, we want to merge. Is there anyone here with experience with this type of requirement? We have a lot of ideas but most of them require a LOT of work, massive modification to the database or to the existing queries. This is a 2 millions and growing C++ app, so rewriting it is not possible! Thanks for any ideas that you may give us! J-F

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• Trying to calculate large numbers in Python with gmpy. Python keeps crashing?

  - by Ryan Peschel

  I was recommended to use gmpy to assist with calculating large numbers efficiently. Before I was just using python and my script ran for a day or two and then ran out of memory (not sure how that happened because my program's memory usage should basically be constant throughout.. maybe a memory leak?) Anyways, I keep getting this weird error after running my program for a couple seconds: mp_allocate< 545275904->545275904 > Fatal Python error: mp_allocate failure This application has requested the Runtime to terminate it in an unusual way. Please contact the application's support team for more information. Also, python crashes and Windows 7 gives me the generic python.exe has stopped working dialog. This wasn't happening with using standard python integers. Now that I switch to gmpy I am getting this error just seconds in to running my script. I thought gmpy was specialized in dealing with large number arithmetic? For reference, here is a sample program that produces the error: import gmpy2 p = gmpy2.xmpz(3000000000) s = gmpy2.xmpz(2) M = s**p for x in range(p): s = (s * s) % M I have 10 gigs of RAM and without gmpy this script ran for days without running out of memory (still not sure how that happened considering s never really gets larger.. Anyone have any ideas? EDIT: Forgot to mention I am using Python 3.2

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• How can I make hundreds of simultaneously running processes communicate with a database through one

  - by Olfan

  Long speech short: How can I make hundreds of simultaneously running processes communicate with a database through one or few permanent sessions? The whole story: I once built a number crunching engine that handles vast amounts of large data files by forking off one child after another giving each a small number of files to work on. File locking, progress monitoring and result propagation happen in an Oracle database which all (sub-)processes access at various times using an application-specific module which encapsulates DBI. This worked well at first, but now with higher volumes of input data, the number of database sessions (one per child, and they can be very short-lived) constantly being opened and closed is becoming an issue. I now want to centralise database access so that there are only one or few fixed database sessions which handle all database access for all the (sub-)processes. The presence of the database abstraction module should make the changes easy because the function calls in the worker instances can stay the same. My problem is that I cannot think of a suitable way to enhance said module in order to establish communication between all the processes and the database connector(s). I thought of message queueing, but couldn't come up with a way of connecting a large herd of requestors with one or few database connectors in a way so that bidirectional communication is possible (for collecting the query result). An asynchronous approach could help here in that all requests are written to the same queue and the database connector servicing the request will "call back" to submit the result. But my mind fails me in generating an image clear enough so that I can paint into code. Threading instead of forking might have given me an easier start, but this would now require massive changes to the code base that I'm not prepared to do to a live system. The more I think of it, the more the base idea looks like a pre-forked web server to me only that it doesn't serve web pages but database queries. Any ideas on what to dig into, and where? Sample (pseudo) code to inspire me, links to possibly related articles, ready solutions on CPAN maybe?

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• Qt: QStackedWidget solution

  - by Martin

  I'm building a Qt application that have about 30 different views (QWidgets). My idea is to use a QStackedWidget to make it easy to switch between the different views in the application. I have two different solutions of how to implement this and use as little memory as possible when the user navigates through the application. Solution 1: Everytime I need to show a view I check if it is already in the stack. (The user might open the same view many times, maybe a view showing an item from a database). If the view is in the stack already it doesn't need to be created again and I can just show the view. The good thing with this solution is that I reuse the views (widgets) so they only need to be created once. This is good as the UI and other stuff should look the same everytime the user show a view, so why not reuse it? The problem with this solution is that every view has childrens. Maybe an object, a QList with objects or other things. A good thing with Qt is that you can use the parent-children mechanism so that the children will be deleted when the parent is deleted. As I never delete the parent (view) I need to handle this myself as the children might need to be deleted from different times when the view is shown. (Maybe the view show a list with objects and the list should be updated from a database each time the view is shown.) Solution 2: Everytime I need to show a QWidget I create a new one and show it. When it is not shown anymore, I delete it from memory. This is a quite easy solution. And as I delete the views when they are not shown both the view and it's children should be deleted from memory so it shouldn't increase memory, am I right? Which one of the solutions do you recommend?

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• Implementing Database Settings Using Policy Based Management

  - by Ashish Kumar Mehta

  Introduction Database Administrators have always had a tough time to ensuring that all the SQL Servers administered by them are configured according to the policies and standards of organization. Using SQL Server’s  Policy Based Management feature DBAs can now manage one or more instances of SQL Server 2008 and check for policy compliance issues. In this article we will utilize Policy Based Management (aka Declarative Management Framework or DMF) feature of SQL Server to implement and verify database settings on all production databases. It is best practice to enforce the below settings on each Production database. However, it can be tedious to go through each database and then check whether the below database settings are implemented across databases. In this article I will explain it to you how to utilize the Policy Based Management Feature of SQL Server 2008 to create a policy to verify these settings on all databases and in cases of non-complaince how to bring them back into complaince. Database setting to enforce on each user database : Auto Close and Auto Shrink Properties of database set to False Auto Create Statistics and Auto Update Statistics set to True Compatibility Level of all the user database set as 100 Page Verify set as CHECKSUM Recovery Model of all user database set to Full Restrict Access set as MULTI_USER Configure a Policy to Verify Database Settings 1. Connect to SQL Server 2008 Instance using SQL Server Management Studio 2. In the Object Explorer, Click on Management > Policy Management and you will be able to see Policies, Conditions & Facets as child nodes 3. Right click Policies and then select New Policy…. from the drop down list as shown in the snippet below to open the  Create New Policy Popup window. 4. In the Create New Policy popup window you need to provide the name of the policy as “Implementing and Verify Database Settings for Production Databases” and then click the drop down list under Check Condition. As highlighted in the snippet below click on the New Condition… option to open up the Create New Condition window. 5. In the Create New Condition popup window you need to provide the name of the condition as “Verify and Change Database Settings”. In the Facet drop down list you need to choose the Facet as Database Options as shown in the snippet below. Under Expression you need to select Field value as @AutoClose and then choose Operator value as ‘ = ‘ and finally choose Value as False. Now that you have successfully added the first field you can now go ahead and add rest of the fields as shown in the snippet below. Once you have successfully added all the above shown fields of Database Options Facet, click OK to save the changes and to return to the parent Create New Policy – Implementing and Verify Database Settings for Production Database windows where you will see that the newly created condition “Verify and Change Database Settings” is selected by default. Continues…

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• SQL SERVER – Shard No More – An Innovative Look at Distributed Peer-to-peer SQL Database

  - by pinaldave

  There is no doubt that SQL databases play an important role in modern applications. In an ideal world, a single database can handle hundreds of incoming connections from multiple clients and scale to accommodate the related transactions. However the world is not ideal and databases are often a cause of major headaches when applications need to scale to accommodate more connections, transactions, or both. In order to overcome scaling issues, application developers often resort to administrative acrobatics, also known as database sharding. Sharding helps to improve application performance and throughput by splitting the database into two or more shards. Unfortunately, this practice also requires application developers to code transactional consistency into their applications. Getting transactional consistency across multiple SQL database shards can prove to be very difficult. Sharding requires developers to think about things like rollbacks, constraints, and referential integrity across tables within their applications when these types of concerns are best handled by the database. It also makes other common operations such as joins, searches, and memory management very difficult. In short, the very solution implemented to overcome throughput issues becomes a bottleneck in and of itself. What if database sharding was no longer required to scale your application? Let me explain. For the past several months I have been following and writing about NuoDB, a hot new SQL database technology out of Cambridge, MA. NuoDB is officially out of beta and they have recently released their first release candidate so I decided to dig into the database in a little more detail. Their architecture is very interesting and exciting because it completely eliminates the need to shard a database to achieve higher throughput. Each NuoDB database consists of at least three or more processes that enable a single database to run across multiple hosts. These processes include a Broker, a Transaction Engine and a Storage Manager.  Brokers are responsible for connecting client applications to Transaction Engines and maintain a global view of the network to keep track of the multiple Transaction Engines available at any time. Transaction Engines are in-memory processes that client applications connect to for processing SQL transactions. Storage Managers are responsible for persisting data to disk and serving up records to the Transaction Managers if they don’t exist in memory. The secret to NuoDB’s approach to solving the sharding problem is that it is a truly distributed, peer-to-peer, SQL database. Each of its processes can be deployed across multiple hosts. When client applications need to connect to a Transaction Engine, the Broker will automatically route the request to the most available process. Since multiple Transaction Engines and Storage Managers running across multiple host machines represent a single logical database, you never have to resort to sharding to get the throughput your application requires. NuoDB is a new pioneer in the SQL database world. They are making database scalability simple by eliminating the need for acrobatics such as sharding, and they are also making general administration of the database simpler as well.  Their distributed database appears to you as a user like a single SQL Server database.  With their RC1 release they have also provided a web based administrative console that they call NuoConsole. This tool makes it extremely easy to deploy and manage NuoDB processes across one or multiple hosts with the click of a mouse button. See for yourself by downloading NuoDB here. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: CodeProject, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLServer, T SQL, Technology Tagged: NuoDB

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• Large Object Heap Fragmentation

  - by Paul Ruane

  The C#/.NET application I am working on is suffering from a slow memory leak. I have used CDB with SOS to try to determine what is happening but the data does not seem to make any sense so I was hoping one of you may have experienced this before. The application is running on the 64 bit framework. It is continuously calculating and serialising data to a remote host and is hitting the Large Object Heap (LOH) a fair bit. However, most of the LOH objects I expect to be transient: once the calculation is complete and has been sent to the remote host, the memory should be freed. What I am seeing, however, is a large number of (live) object arrays interleaved with free blocks of memory, e.g., taking a random segment from the LOH: 0:000> !DumpHeap 000000005b5b1000 000000006351da10 Address MT Size ... 000000005d4f92e0 0000064280c7c970 16147872 000000005e45f880 00000000001661d0 1901752 Free 000000005e62fd38 00000642788d8ba8 1056 <-- 000000005e630158 00000000001661d0 5988848 Free 000000005ebe6348 00000642788d8ba8 1056 000000005ebe6768 00000000001661d0 6481336 Free 000000005f214d20 00000642788d8ba8 1056 000000005f215140 00000000001661d0 7346016 Free 000000005f9168a0 00000642788d8ba8 1056 000000005f916cc0 00000000001661d0 7611648 Free 00000000600591c0 00000642788d8ba8 1056 00000000600595e0 00000000001661d0 264808 Free ... Obviously I would expect this to be the case if my application were creating long-lived, large objects during each calculation. (It does do this and I accept there will be a degree of LOH fragmentation but that is not the problem here.) The problem is the very small (1056 byte) object arrays you can see in the above dump which I cannot see in code being created and which are remaining rooted somehow. Also note that CDB is not reporting the type when the heap segment is dumped: I am not sure if this is related or not. If I dump the marked (<--) object, CDB/SOS reports it fine: 0:015> !DumpObj 000000005e62fd38 Name: System.Object[] MethodTable: 00000642788d8ba8 EEClass: 00000642789d7660 Size: 1056(0x420) bytes Array: Rank 1, Number of elements 128, Type CLASS Element Type: System.Object Fields: None The elements of the object array are all strings and the strings are recognisable as from our application code. Also, I am unable to find their GC roots as the !GCRoot command hangs and never comes back (I have even tried leaving it overnight). So, I would very much appreciate it if anyone could shed any light as to why these small (<85k) object arrays are ending up on the LOH: what situations will .NET put a small object array in there? Also, does anyone happen to know of an alternative way of ascertaining the roots of these objects? Thanks in advance. Update 1 Another theory I came up with late yesterday is that these object arrays started out large but have been shrunk leaving the blocks of free memory that are evident in the memory dumps. What makes me suspicious is that the object arrays always appear to be 1056 bytes long (128 elements), 128 * 8 for the references and 32 bytes of overhead. The idea is that perhaps some unsafe code in a library or in the CLR is corrupting the number of elements field in the array header. Bit of a long shot I know... Update 2 Thanks to Brian Rasmussen (see accepted answer) the problem has been identified as fragmentation of the LOH caused by the string intern table! I wrote a quick test application to confirm this: static void Main() { const int ITERATIONS = 100000; for (int index = 0; index < ITERATIONS; ++index) { string str = "NonInterned" + index; Console.Out.WriteLine(str); } Console.Out.WriteLine("Continue."); Console.In.ReadLine(); for (int index = 0; index < ITERATIONS; ++index) { string str = string.Intern("Interned" + index); Console.Out.WriteLine(str); } Console.Out.WriteLine("Continue?"); Console.In.ReadLine(); } The application first creates and dereferences unique strings in a loop. This is just to prove that the memory does not leak in this scenario. Obviously it should not and it does not. In the second loop, unique strings are created and interned. This action roots them in the intern table. What I did not realise is how the intern table is represented. It appears it consists of a set of pages -- object arrays of 128 string elements -- that are created in the LOH. This is more evident in CDB/SOS: 0:000> .loadby sos mscorwks 0:000> !EEHeap -gc Number of GC Heaps: 1 generation 0 starts at 0x00f7a9b0 generation 1 starts at 0x00e79c3c generation 2 starts at 0x00b21000 ephemeral segment allocation context: none segment begin allocated size 00b20000 00b21000 010029bc 0x004e19bc(5118396) Large object heap starts at 0x01b21000 segment begin allocated size 01b20000 01b21000 01b8ade0 0x00069de0(433632) Total Size 0x54b79c(5552028) ------------------------------ GC Heap Size 0x54b79c(5552028) Taking a dump of the LOH segment reveals the pattern I saw in the leaking application: 0:000> !DumpHeap 01b21000 01b8ade0 ... 01b8a120 793040bc 528 01b8a330 00175e88 16 Free 01b8a340 793040bc 528 01b8a550 00175e88 16 Free 01b8a560 793040bc 528 01b8a770 00175e88 16 Free 01b8a780 793040bc 528 01b8a990 00175e88 16 Free 01b8a9a0 793040bc 528 01b8abb0 00175e88 16 Free 01b8abc0 793040bc 528 01b8add0 00175e88 16 Free total 1568 objects Statistics: MT Count TotalSize Class Name 00175e88 784 12544 Free 793040bc 784 421088 System.Object[] Total 1568 objects Note that the object array size is 528 (rather than 1056) because my workstation is 32 bit and the application server is 64 bit. The object arrays are still 128 elements long. So the moral to this story is to be very careful interning. If the string you are interning is not known to be a member of a finite set then your application will leak due to fragmentation of the LOH, at least in version 2 of the CLR. In our application's case, there is general code in the deserialisation code path that interns entity identifiers during unmarshalling: I now strongly suspect this is the culprit. However, the developer's intentions were obviously good as they wanted to make sure that if the same entity is deserialised multiple times then only one instance of the identifier string will be maintained in memory.

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• What is my peak total memory usage? How much of my RAM is actually being actively used?

  - by William C

  Hi, Is there an app or utility in Windows that shows me the peak value of in-use memory (i.e., the total of the shareable and private memory of processes, drivers and the operating system) (not standby nor free)? I've got lots of memory and I'm installing an in-memory file cache, called "eBoostr", and would like an idea how much memory to allocate for it and still avoid deteriorating page faults. Essentially, I want the answer to the question, "How much of my RAM is actually being actively used?" W

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• Design approach, string table data, variables, stl memory usage

  - by howieh

  I have an old structure class like this: typedef vector<vector<string>> VARTYPE_T; which works as a single variable. This variable can hold from one value over a list to data like a table. Most values are long,double, string or double [3] for coordinates (x,y,z). I just convert them as needed. The variables are managed in a map like this : map<string,VARTYPE_T *> where the string holds the variable name. Sure, they are wrapped in classes. Also i have a tree of nodes, where each node can hold one of these variablemaps. Using VS 2008 SP1 for this, i detect a lot of memory fragmentation. Checking against the stlport, stlport seemed to be faster (20% ) and uses lesser memory (30%, for my test cases). So the question is: What is the best implementation to solve this requirement with fast an properly used memory ? Should i write an own allocator like a pool allocator. How would you do this ? Thanks in advance, Howie

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• UIWebView rotation and memory problem

  - by Fer

  Hi. I have an UIWebView that loads a embedded XHTML like this: body = [[UIWebView alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)]; body.scalesPageToFit = YES; body.backgroundColor = [UIColor scrollViewTexturedBackgroundColor]; body.autoresizingMask = UIViewAutoresizingFlexibleBottomMargin | UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleRightMargin; [self.view addSubview:body]; [body loadRequest:[NSURLRequest requestWithURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:@"article16" ofType:@"xhtml"]isDirectory:NO]]]; This XHTML have a lot of images, and when I rotate the device I got some memory warnings, and sometimes the app crashes. If I remove the autoresizing mask, specifically the UIViewAutoresizingFlexibleWidth (I have tryed with only UIViewAutoresizingFlexibleLeftMargin and UIViewAutoresizingFlexibleRightMargin with no problems), the memory warning stops, and the app does not crash anymore. If I remove all autoresizing mask, and set the new webView frame in didRotate or willRotate, I got the same warnings as using the UIViewAutoresizingFlexibleWidth. There's a app, called Atomic Web that could open the same XHTML and rotate with no memory warnings, and safari can open it as well, but if I create a project with only that UIWebView, the app sometimes crashes. Someone knows what this may be? Can I set the webview frame in other way? Why can't I use the autoresizing mask? Thanks for your attention.

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• Allowed memory size of 33554432 bytes exhausted (tried to allocate 93 bytes) error in php

  - by Chris

  I inserted the following code: $counter = 1; while($_POST['additional_contact1'] != '' || $_POST['additional_contact2'] != '' || $_POST['additional_contact3'] != '') { if($_POST['additional_contact' . $counter] != '') { $_SESSION['contact'][$counter]['additional_contact'] = $_POST['additional_contact' . $counter]; $_SESSION['contact'][$counter]['additional_int_prefix'] = $_POST['additional_int_prefix' . $counter]; $_SESSION['contact'][$counter]['additional_prefix'] = $_POST['additional_prefix' . $counter]; $_SESSION['contact'][$counter]['additional_first'] = $_POST['additional_first' . $counter]; $_SESSION['contact'][$counter]['additional_last'] = $_POST['additional_last' . $counter]; } else { $_SESSION['contact'][$counter]['additional_contact'] = null; $_SESSION['contact'][$counter]['additional_int_prefix'] = null; $_SESSION['contact'][$counter]['additional_prefix'] = null; $_SESSION['contact'][$counter]['additional_first'] = null; $_SESSION['contact'][$counter]['additional_last'] = null; } $counter++; } and I received this error: Fatal error: Allowed memory size of 33554432 bytes exhausted (tried to allocate 93 bytes) I tried to increase the memory limit with ini_set(), but it still won't work at 96M. What am I doing wrong with my code to make it need so much memory? How can I solve this problem?

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• Can't connect to SQL Server 2008 - looks like Shared Memory problem

  - by Proposition Joe

  I am unable to connect to my local instance of SQL Server 2008 Express using SQL Server Management Studio. I believe the problem is related to a change I made to the connection protocols. Before the error occurred, I had Shared Memory enabled and Named Pipes and TCP/IP disabled. I then enabled both Named Pipes and TCP/IP, and this is when I started experiencing the problem. When I try to connect to the server with SSMS (with either my SQL server sysadmin login or with windows authentication), I get the following error message: A connection was successfully established with the server, but then an error occurred during the login process. (provider: Named Pipes Provider, error: 0 - No process is on the other end of the pipe.) (Microsoft SQL Server, Error: 233) Why is it returning a Named Pipes error? Why would it not just use Shared Memory, as this has a higher priority order in the list of connection protocols? It seems like it is not listening on Shared Memory for some reason? When I set Named Pipes to enabled and try to connect, I get the same error message. My windows account is does not have administrator priviliges on my computer - perhaps this is making a difference in some way (as some of the discussions in this post about an "SuperSocketNetLib\Lpc" registry key seems to suggest).

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• Cocoa memory management

  - by silvio

  At various points during my application's workflow, I need so show a view. That view is quite memory intensive, so I want it to be deallocated when it gets discarded by the user. So, I wrote the following code: - (MyView *)myView { if (myView != nil) return myView; myView = [[UIView alloc] initWithFrame:CGRectZero]; // allocate memory if necessary. // further init here return myView; } - (void)discardView { [myView discard]; // the discard methods puts the view offscreen. [myView release]; // free memory! } - (void)showView { view = [self myView]; // more code that puts the view onscreen. } Unfortunately, this methods only works the first time. Subsequent requests to put the view onscreen result in "message sent to deallocated instance" errors. Apparently, a deallocated instance isn't the same thing as nil. I thought about putting an additional line after [myView release] that reads myView = nil. However, that could result in errors (any calls to myView after that line would probably yield errors). So, how can I solve this problem?

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• stack and heap issue for iPhone memory management

  - by Forrest

  From this post I got know that the Objective-C runtime does not allow objects to be instantiated on the stack, but only on the heap; this means that you don’t have “automatic objects”, nor things like auto_ptr objects to help you manage memory; Someone give one example in post Objective C: Memory Allocation on stack vs. heap NSString* str = @"hello"; but this NSString is also not allocated in stack. Feel odd that this str is static. (Who can explain this ? ) Question here is that why there is no heap ? even mixing c++ together with Object C ? /////////////////////////////// Clear my question /////////////////////////////// I am confused , so questions are not clear. Let me put in this way. 1) All Object C objects should be alloc in stack ? ( I think yes ) 2)In C++, there are stack for memory, so for iOS app, also have stack ? ( I think yes ) 3) for iOS app, if only use Object C, so what is the usage of stack ? what kind of objects should use stack then ?

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• Determining failing sectors on portable flash memory

  - by Faxwell Mingleton

  I'm trying to write a program that will detect signs of failure for portable flash memory devices (thumb drives, etc). I have seen tools in the past that are able to detect failing sectors and other kinds of trouble on conventional mechanical hard drives, but I fear that flash memory does not have the same kind of predictable low-level access to the hardware due to the internal workings of the storage. Things like wear-leveling and other block-remapping techniques (to skip over 'dead' sectors?) lead me to believe that determining if a flash drive is failing will be difficult at best, if not impossible (short of having constant read failures and device unmounts). Flash drives at their end-of-life should be easy to detect (constant CRC discrepancies during reads and all-out failure). But what about drives that might be failing early? Are there any tell-tale signs like slower throughput speeds that might indicate a flash drive is going to fail much sooner than normal? Along the lines of detecting potentially bad blocks, I had considered attempting random reads/writes to a file close to or exactly the size of the entire volume, but even then is it possible that the drive might report sizes under its maximum capacity to account for 'dead' blocks? In short, is there any way to circumvent or at least detect (algorithmically or otherwise) the use of block-remapping or other life extension techniques for flash memory? Let me end this question by expressing my uncertainty as to whether or not this belongs on serverfault.com . This is definitely a hardware-related question, but I also desire a software solution - preferably one that I can program myself. If this question is misplaced, I will be happy to migrate it to serverfault - but I do need a programming solution. Please let me know if you need clarification :) Thanks!

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• WPF User Control is causing Out of Memory Exception

  - by Chairman Meow

  Looking for a free spell checking solution, I thought I was so smart in doing this but I guess not. I have created a windows form based application and I want the form to add a user specified amount of user controls (with textboxes) on to a panel. The user can then click some button and the controls on this panel are cleared and new ones are added. The user does something and the process is repeated. Now, I wanted these textboxes to support spell checking and looked all over for a free solution. WPF textboxes support spell checking where the ones in regular win forms do not. I thought I would be able to use these WPF textboxes by adding them to an ElementHost object which is, in turn, within a panel. This panel would be a user control. So, in my application, I would be able to add instances of these user controls onto the form and make use of .NET's spell checking goodness. This actually worked but after using the application for a while, found that the application would eventually freeze on me due to out of memory errors. I have pinpointed the memory errors to these WPF controls since this problem does not happen with normal textboxes. When the window is opened and the number of controls is specified, this is pretty much how the controls are added: Dim xOffset As Integer = 0 For i As Integer = 0 To theNumber Dim myUserControl As New SpecialUserControl() myPanel.Controls.Add(myUserControl) myUserControl.Location = New Point(7, 7) myUserControl.Location = New Point(xOffset, 7) xOffset = xOffset + 207 Next Note that: myPanel is a panel on a form SpecialUserControl is the user control with WPF textbox (within an ElementHost object) When the user pressed a button, the panel is cleared: myUserControl.Controls.Clear() The user can then repeat the process. There are a lot of results on the internet when I tried to find a solution and I'm thinking that the problem I am having is due to the fact that the WPF control is not going away even after clearing the panel. Following this conclusion, I have tried different solutions regarding disposing these controls or setting them to nothing but the memory problem keeps occurring. If someone could give me some advice or ideas here, I'd really appreciate it.

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• Memory leak for NSDictionary loaded by plist file

  - by Pask

  I have a memory leak problem that just can not understand! Watch this initialization method: - (id)initWithNomeCompositore:(NSString *)nomeCompositore nomeOpera:(NSString *)nomeOpera { if (self = [super init]) { NSString *pathOpere = [[NSBundle mainBundle] pathForResource:kNomeFilePlistOpere ofType:kTipoFilePlist]; NSDictionary *dicOpera = [NSDictionary dictionaryWithDictionary: [[[NSDictionary dictionaryWithContentsOfFile:pathOpere] objectForKey:nomeCompositore] objectForKey:nomeOpera]]; self.nomeCompleto = [[NSString alloc] initWithString:nomeOpera]; self.compositore = [[NSString alloc] initWithString:nomeCompositore]; self.tipologia = [[NSString alloc] initWithString:[dicOpera objectForKey:kKeyTipologia]]; } return self;} Then this little variation (note self.tipologia): - (id)initWithNomeCompositore:(NSString *)nomeCompositore nomeOpera:(NSString *)nomeOpera { if (self = [super init]) { NSString *pathOpere = [[NSBundle mainBundle] pathForResource:kNomeFilePlistOpere ofType:kTipoFilePlist]; NSDictionary *dicOpera = [NSDictionary dictionaryWithDictionary: [[[NSDictionary dictionaryWithContentsOfFile:pathOpere] objectForKey:nomeCompositore] objectForKey:nomeOpera]]; self.nomeCompleto = [[NSString alloc] initWithString:nomeOpera]; self.compositore = [[NSString alloc] initWithString:nomeCompositore]; self.tipologia = [[NSString alloc] initWithString:@"Test"]; } return self;} In the first variant is generated a memory leak, the second is not! And I just can not understand why! The memory leak is evidenced by Instruments, highlighted the line: [NSDictionary dictionaryWithContentsOfFile:pathOpere] This is the dealloc method: - (void)dealloc { [tipologia release]; [compositore release]; [nomeCompleto release]; [super dealloc];}

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• WPF Spellcheck Engine takes up too much memory.

  - by Matt H.

  Each datatemplate in my WPF ItemsControl contains FIVE custom bindable richtextbox controls. It is a data-driven app that for authoring multiple-choice questions -- The question and four answer choices must all support: 1) Spell check 2) Rich formatting (otherwise I'd use regular textboxes) The spell check object in .NET 4 has a Friend constructor that takes a single argument of owner As TextBoxBase This means every richtextbox in the ItemsControl has 5 Spellcheck objects! This is the problem -- every spell check engine is consuming about 500k memory. So after you favor in the spellcheck, bindings, additional controls in the DataTemplate, etc.. a single multi choice question consumes more than 3MB memory. Users with 100--200 questions will quickly see the App raise it's memory consumption to 500+ MB. Management is definitely not OK with this. Is there a way to minimimze this problem? The best suggestion I've heard is to enable/disable spellcheck if the richtextbox is in the ItemsControl's scrollviewer: I haven't gotten an answer to how to go about it: (http://stackoverflow.com/questions/2869012/possible-to-implement-an-isviewportvisible-dependencyproperty-for-an-item-in-an-i) Any good ideas?

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• IPhone SDK - Leaking Memory with performSelectorInBackground

  - by Steblo

  Hi. Maybe someone can help me with this strange thing: If a user clicks on a button, a new UITableView is pushed to the navigation controller. This new view is doing some database querying which takes some time. Therefore I wanted to do the loading in background. What works WITHOUT leaking memory (but freezes the screen until everything is done): WorkController *tmp=[[WorkController alloc] initWithStyle:UITableViewStyleGrouped]; self.workController=tmp; [tmp release]; [self.workController loadList]; // Does the DB Query [self.workController pushViewController:self.workController animated:YES]; Now I tried to do this: // Show Wait indicator .... WorkController *tmp=[[WorkController alloc] initWithStyle:UITableViewStyleGrouped]; self.workController=tmp; [tmp release]; [self performSelectorInBackground:@selector(getController) withObject:nil]; } -(void) getController { [self.workController loadList]; // Does the DB Query [self.navigationController pushViewController:self.workController animated:YES]; } This also works but is leaking memory and I don't know why ! Can you help ? By the way - is it possible for an App to get into AppStore with a small memory leak ? Or will this be checked first of all ? Thanks in advance !

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• C#: Accessing PerformanceCounters for the ".NET CLR Memory category"

  - by Mads Ravn

  I'm trying to access the performance counters located in ".NET CLR Memory category" through C# using the PerformanceCounter class. However a cannot instantiate the categories with what I would expect was the correct category/counter name new PerformanceCounter(".NET CLR Memory", "# bytes in all heaps", Process.GetCurrentProcess().ProcessName); I tried looping through categories and counters using the following code string[] categories = PerformanceCounterCategory.GetCategories().Select(c => c.CategoryName).OrderBy(s => s).ToArray(); string toInspect = string.Join(",\r\n", categories); System.Text.StringBuilder interestingToInspect = new System.Text.StringBuilder(); string[] interestingCategories = categories.Where(s => s.StartsWith(".NET") || s.Contains("Memory")).ToArray(); foreach (string interestingCategory in interestingCategories) { PerformanceCounterCategory cat = new PerformanceCounterCategory(interestingCategory); foreach (PerformanceCounter counter in cat.GetCounters()) { interestingToInspect.AppendLine(interestingCategory + ":" + counter.CounterName); } } toInspect = interestingToInspect.ToString(); But could not find anything that seems to match. Is it not possible to observe these values from within the CLR or am I doing something wrong. The environment, should it matter, is .NET 4.0 running on a 64-bit windows 7 box.

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• Free Memory Occupied by Std List, Vector, Map etc

  - by Graviton

  Coming from a C# background, I have only vaguest idea on memory management on C++-- all I know is that I would have to free the memory manually. As a result my C++ code is written in such a way that objects of the type std::vector, std::list, std::map are freely instantiated, used, but not freed. I didn't realize this point until I am almost done with my programs, now my code is consisted of the following kinds of patterns: struct Point_2 { double x; double y; }; struct Point_3 { double x; double y; double z; }; list<list<Point_2>> Computation::ComputationJob(list<Point_3> pts3D, vector<Point_2> vectors) { map<Point_2, double> pt2DMap=ConstructPointMap(pts3D); vector<Point_2> vectorList = ConstructVectors(vectors); list<list<Point_2>> faceList2D=ConstructPoints(vectorList , pt2DMap); return faceList2D; } My question is, must I free every.single.one of the list usage ( in the above example, this means that I would have to free pt2DMap, vectorList and faceList2D)? That would be very tedious! I might just as well rewrite my Computation class so that it is less prone to memory leak. Any idea how to fix this?

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• Boost Unit testing memory reuse causing tests that should fail to pass

  - by Knyphe

  We have started using the boost unit testing library for a large existing code base, and I have run into some trouble with unit tests incorrectly passing, seemingly due to the reuse of memory on the stack. Here is my situation: BOOST_AUTO_TEST_CASE(test_select_base_instantiation_default) { SelectBase selectBase(); BOOST_CHECK_EQUAL( selectBase.getSelectType(), false); BOOST_CHECK_EQUAL( selectBase.getTypeName(_T("")); BOOST_CHECK_EQUAL( selectBase.getEntityType(), -1); BOOST_CHECK_EQUAL( selectBase.getDataPos(), -1); } BOOST_AUTO_TEST_CASE(test_select_base_instantiation_default) { SelectBase selectBase(true, _T("abc")); BOOST_CHECK_EQUAL( selectBase.getSelectType(), false); BOOST_CHECK_EQUAL( selectBase.getTypeName(_T("abc")); BOOST_CHECK_EQUAL( selectBase.getEntityType(), -1); BOOST_CHECK_EQUAL( selectBase.getDataPos(), -1); } The first test passed correctly, initializing all the variables. The constructor in the second unit test did not correctly set EntityType or DataPosition, but the unit test passed. I was able to get it to fail by placing some variables on the stack in the second test, like so: BOOST_AUTO_TEST_CASE(test_select_base_instantiation_default) { int a, b; SelectBase selectBase(true, _T("abc")); BOOST_CHECK_EQUAL( selectBase.getSelectType(), false); BOOST_CHECK_EQUAL( selectBase.getTypeName(_T("abc")); BOOST_CHECK_EQUAL( selectBase.getEntityType(), -1); BOOST_CHECK_EQUAL( selectBase.getDataPos(), -1); } If there is only one int, only the dataPos CHECK_EQUAL fails, but if there are two, both EntityType and DataPos fail, so it seems pretty clear that this is an issue with the variables being created on the same stack memory or some such. Is there a good way to clear the memory between each unit test, or am I potentially using the library incorrectly or writing bad tests? Any help would be appreciated.

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• Linux C debugging library to detect memory corruptions

  - by calandoa

  When working sometimes ago on an embedded system with a simple MMU, I used to program dynamically this MMU to detect memory corruptions. For instance, at some moment at runtime, the foo variable was overwritten with some unexpected data (probably by a dangling pointer or whatever). So I added the additional debugging code : at init, the memory used by foo was indicated as a forbidden region to the MMU; each time foo was accessed on purpose, access to the region was allowed just before then forbidden just after; a MMU irq handler was added to dump the master and the address responsible of the violation. This was actually some kind of watchpoint, but directly self-handled by the code itself. Now, I would like to reuse the same trick, but on a x86 platform. The problem is that I am very far from understanding how is working the MMU on this platform, and how it is used by Linux, but I wonder if any library/tool/system call already exist to deal with this problem. Note that I am aware that various tools exist like Valgrind or GDB to manage memory problems, but as far as I know, none of these tools car be dynamically reconfigured by the debugged code. I am mainly interested for user space under Linux, but any info on kernel mode or under Windows is also welcome!

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• Memory leaks while using array of double

  - by Gacek

  I have a part of code that operates on large arrays of double (containing about 6000 elements at least) and executes several hundred times (usually 800) . When I use standard loop, like that: double[] singleRow = new double[6000]; int maxI = 800; for(int i=0; i<maxI; i++) { singleRow = someObject.producesOutput(); //... // do something with singleRow // ... } The memory usage rises for about 40MB (from 40MB at the beggining of the loop, to the 80MB at the end). When I force to use the garbage collector to execute at every iteration, the memory usage stays at the level of 40MB (the rise is unsignificant). double[] singleRow = new double[6000]; int maxI = 800; for(int i=0; i<maxI; i++) { singleRow = someObject.producesOutput(); //... // do something with singleRow // ... GC.Collect() } But the execution time is 3 times longer! (it is crucial) How can I force the C# to use the same area of memory instead of allocating new ones? Note: I have the access to the code of someObject class, so if it would be needed, I can change it.

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• Usage of VIsual Memory Leak Detector

  - by Yan Cheng CHEOK

  I found a very interesting memory leak detector by using Visual C++. http://www.codeproject.com/KB/applications/visualleakdetector.aspx I try it out, but cannot make it works to detect a memory leak code. I am using MS Visual Studio 2008. Any step I had missed out? #include "stdafx.h" #include "vld.h" #include <iostream> void fun() { new int[1000]; } int _tmain(int argc, _TCHAR* argv[]) { fun(); std::cout << "lead?" << std::endl; getchar(); return 0; } The output when I run in debug mode is : ... ... 'Test.exe': Loaded 'C:\WINDOWS\WinSxS\x86_Microsoft.VC80.CRT_1fc8b3b9a1e18e3b_8.0.50727.4053_x-ww_e6967989\msvcr80.dll', Symbols loaded. 'Test.exe': Loaded 'C:\WINDOWS\system32\msvcrt.dll', Symbols loaded (source information stripped). 'Test.exe': Loaded 'C:\WINDOWS\WinSxS\x86_Microsoft.VC90.DebugCRT_1fc8b3b9a1e18e3b_9.0.30729.1_x-ww_f863c71f\msvcp90d.dll', Symbols loaded. 'Test.exe': Loaded 'C:\Program Files\Visual Leak Detector\bin\dbghelp.dll', Symbols loaded (source information stripped). Visual Leak Detector Version 1.9d installed. No memory leaks detected. Visual Leak Detector is now exiting. The program '[5468] Test.exe: Native' has exited with code 0 (0x0).

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