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  • streaming XML serialization in .net

    - by Luca Martinetti
    Hello, I'm trying to serialize a very large IEnumerable<MyObject> using an XmlSerializer without keeping all the objects in memory. The IEnumerable<MyObject> is actually lazy.. I'm looking for a streaming solution that will: Take an object from the IEnumerable<MyObject> Serialize it to the underlying stream using the standard serialization (I don't want to handcraft the XML here!) Discard the in memory data and move to the next I'm trying with this code: using (var writer = new StreamWriter(filePath)) { var xmlSerializer = new XmlSerializer(typeof(MyObject)); foreach (var myObject in myObjectsIEnumerable) { xmlSerializer.Serialize(writer, myObject); } } but I'm getting multiple XML headers and I cannot specify a root tag <MyObjects> so my XML is invalid. Any idea? Thanks

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  • Algorithm: How to tell if an array is a permutation in O(n)?

    - by Iulian Serbanoiu
    Hello, Input: A read-only array of N elements containing integer values from 1 to N. And a memory zone of a fixed size (10, 100, 1000 etc - not depending on N). How to tell in O(n) if the array represents a permutation? --What I achieved so far:-- I use the limited memory area to store the sum and the product of the array. I compare the sum with N*(N+1)/2 and the product with N! I know that if condition (2) is true I might have a permutation. I'm wondering if there's a way to prove that condition (2) is sufficient to tell if I have a permutation. So far I haven't figured this out ... Thanks, Iulian

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  • gcc/g++: error when compiling large file

    - by Alexander
    Hi, I have a auto-generated C++ source file, around 40 MB in size. It largely consists of push_back commands for some vectors and string constants that shall be pushed. When I try to compile this file, g++ exits and says that it couldn't reserve enough virtual memory (around 3 GB). Googling this problem, I found that using the command line switches --param ggc-min-expand=0 --param ggc-min-heapsize=4096 may solve the problem. They, however, only seem to work when optimization is turned on. 1) Is this really the solution that I am looking for? 2) Or is there a faster, better (compiling takes ages with these options acitvated) way to do this? Best wishes, Alexander Update: Thanks for all the good ideas. I tried most of them. Using an array instead of several push_back() operations reduced memory usage, but as the file that I was trying to compile was so big, it still crashed, only later. In a way, this behaviour is really interesting, as there is not much to optimize in such a setting -- what does the GCC do behind the scenes that costs so much memory? (I compiled with deactivating all optimizations as well and got the same results) The solution that I switched to now is reading in the original data from a binary object file that I created from the original file using objcopy. This is what I originally did not want to do, because creating the data structures in a higher-level language (in this case Perl) was more convenient than having to do this in C++. However, getting this running under Win32 was more complicated than expected. objcopy seems to generate files in the ELF format, and it seems that some of the problems I had disappeared when I manually set the output format to pe-i386. The symbols in the object file are by standard named after the file name, e.g. converting the file inbuilt_training_data.bin would result in these two symbols: binary_inbuilt_training_data_bin_start and binary_inbuilt_training_data_bin_end. I found some tutorials on the web which claim that these symbols should be declared as extern char _binary_inbuilt_training_data_bin_start;, but this does not seem to be right -- only extern char binary_inbuilt_training_data_bin_start; worked for me.

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  • Handling exception form unmanaged dll in C#

    - by StuffHappens
    Hello. I have the following function written in C# public static string GetNominativeDeclension(string surnameNamePatronimic) { if(surnameNamePatronimic == null) throw new ArgumentNullException("surnameNamePatronimic"); IntPtr[] ptrs = null; try { ptrs = StringsToIntPtrArray(surnameNamePatronimic); int resultLen = MaxResultBufSize; int err = decGetNominativePadeg(ptrs[0], ptrs[1], ref resultLen); ThrowException(err); return IntPtrToString(ptrs, resultLen); } catch { return surnameNamePatronimic; } finally { FreeIntPtr(ptrs); } } Function decGetNominativePadeg is in unmanaged dll [DllImport("Padeg.dll", EntryPoint = "GetNominativePadeg")] private static extern Int32 decGetNominativePadeg(IntPtr surnameNamePatronimic, IntPtr result, ref Int32 resultLength); and throws an exception: Attempted to read or write protected memory. This is often an indication that other memory is corrupt. The catch that is in C# code doesn't actually catch it. Why? How to handle this exception? Thank you for your help!

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  • Efficient banner rotation with PHP

    - by reggie
    I rotate a banner on my site by selecting it randomly from an array of banners. Sample code as demonstration: <?php $banners = array( '<iframe>...</iframe>', '<a href="#"><img src="#.jpg" alt="" /></a>', //and so on ); echo $banners(rand(0, count($banners))); ?> The array of banners has become quite big. I am concerned with the amount of memory that this array adds to the execution of my page. But I can't figure out a better way of showing a random banner without loading all the banners into memory...

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  • How do I improve the efficiency of the queries executed by this generic Linq-to-SQL data access clas

    - by Lee D
    Hi all, I have a class which provides generic access to LINQ to SQL entities, for example: class LinqProvider<T> //where T is a L2S entity class { DataContext context; public virtual IEnumerable<T> GetAll() { return context.GetTable<T>(); } public virtual T Single(Func<T, bool> condition) { return context.GetTable<T>().SingleOrDefault(condition); } } From the front end, both of these methods appear to work as you would expect. However, when I run a trace in SQL profiler, the Single method is executing what amounts to a SELECT * FROM [Table], and then returning the single entity that meets the given condition. Obviously this is inefficient, and is being caused by GetTable() returning all rows. My question is, how do I get the query executed by the Single() method to take the form SELECT * FROM [Table] WHERE [condition], rather than selecting all rows then filtering out all but one? Is it possible in this context? Any help appreciated, Lee

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  • Node.js for lua?

    - by Shahbaz
    I've been playing around with node.js (nodejs) for the past few day and it is fantastic. As far as I can tell, lua doesn't have a similar integration of libev and libio which let's one avoid almost any blocking calls and interact with the network and the filesystem in an asynchronous manner. I'm slowly porting my java implementation to nodejs, but I'm shocked that luajit is much faster than v8 JavaScript AND uses far less memory! I imagine writing my server in such an environment (very fast and responsive, very low memory usage, very expressive) will improve my project immensly. Being new to lua, I'm just not sure if such a thing exists. I'll appreciate any pointers. Thanks

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  • Can you decode a mutable Bitmap from an InputStream?

    - by Daniel Lew
    Right now I've got an Android application that: Downloads an image. Does some pre-processing to that image. Displays the image. The dilemma is that I would like this process to use less memory, so that I can afford to download a higher-resolution image. However, when I download the image now, I use BitmapFactory.decodeStream(), which has the unfortunate side effect of returning an immutable Bitmap. As a result, I'm having to create a copy of the Bitmap before I can start operating on it, which means I have to have 2x the size of the Bitmap's memory allocated (at least for a brief period of time; once the copy is complete I can recycle the original). Is there a way to decode an InputStream into a mutable Bitmap?

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  • Java Heap Overflow, Forcing Garbage Collection

    - by Nicholas
    I've create a trie tree with an array of children. When deleting a word, I set the children null, which I would assume deletes the node(delete is a relative term). I know that null doesn't delete the child, just sets it to null, which when using a large amount of words it causes to overflow the heap. Running a top on linux, I can see my memory usage spike to 1gb pretty quickly, but if I force garbage collection after the delete (Runtime.gc()) the memory usage goes to 50mb and never above that. From what I'm told, java by default runs garbage collection before a heap overflow happens, but I can't see to make that happen.

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  • Fluent nHibernate and mapping IDictionary<DaysOfWeek,IDictionay<int, decimal>> how to?

    - by JS Future Software
    Hello, I have problem with making mapping of classes with propert of type Dictionary and value in it of type Dictionary too, like this: public class Class1 { public virtual int Id { get; set; } public virtual IDictionary<DayOfWeek, IDictionary<int, decimal>> Class1Dictionary { get; set; } } My mapping looks like this: Id(i => i.Id); HasMany(m => m.Class1Dictionary); This doesn't work. The important thing I want have everything in one table not in two. WHet I had maked class from this second IDictionary I heve bigger problem. But first I can try like it is now.

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  • MySQL query cache vs caching result-sets in the application layer

    - by GetFree
    I'm running a php/mysql-driven website with a lot of visits and I'm considering the possibility of caching result-sets in shared memory in order to reduce database load. However, right now MySQL's query cache is enabled and it seems to be doing a pretty good job since if I disable query caching, the use of CPU jumps to 100% immediately. Given that situation, I dont know if caching result-sets (or even the generated HTML code) locally in shared memory with PHP will result in any noticeable performace improvement. Does anyone out there have any experience on this matter? PS: Please avoid suggesting heavy-artillery solutions like memcached. Right now I'm looking for simple solutions that dont require too much time to implement, deploy and maintain.

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  • Java object caching, which is faster, reading from a file or from a remote machine?

    - by Kumar225
    I am at a point where I need to take the decision on what to do when caching of objects reaches the configured threshold. Should I store the objects in a indexed file (like provided by JCS) and read them from the file (file IO) when required or have the object stored in a distributed cache (network, serialization, deserialization) We are using Solaris as OS. ============================ Adding some more information. I have this question so as to determine if I can switch to distributed caching. The remote server which will have cache will have more memory and better disk and this remote server will only be used for caching. One of the problems we cannot increase the locally cached objects is , it stores the cached objects in JVM heap which has limited memory(using 32bit JVM). ======================================================================== Thanks, we finally ended up choosing Coherence as our Cache product. This provides many cache configuration topologies, in process vs remote vs disk ..etc.

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  • Do I need to force the GAC to reload an assembly? Is this possible?

    - by Ben McCormack
    I've added types to my .NET classes that I'm using for COM interop. To get it to work with my VB6 application, I unregistered the DLL and re-registered it (using regasm). I then uninstalled and reinstalled it to the GAC (using gacutil). The types are showing up in the VB6 object explorer, but when I run the application in the VB6 IDE, it breaks on the line that instantiates the new types with the error: Automation Errror - The System cannot find the file specified. I thought this odd since I had already updated the GAC, so I uninstalled the dll from the GAC and got the exact same error, which seems to indicate that the older version of the dll is already in memory and needs to be "reloaded" so that the newer DLL is in memory. Is this possible, and if so, what do I need to do?

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  • How to insert HTML into a UIWebView

    - by Mohan Gulati
    I have HTML Content which was being displayed in a text. The next iteration of my app is display the HTML contents into a UIWebView. So I basically replaced my UITextView with UIWebView. However I could not figure out how to inset my HTML snippit into the view. It seems to need a URLRequest which I do not want. I have already stored the HTML content in memory and want to load and display it from memory. Any ideas how I should proceed?

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  • pushScene and popScene or replaceScene . which should we use and when ?

    - by srikanth rongali
    I am using push scene to get the next scene. But, I read that for each PushScene the scene is stored in stack. The memory usage is more. So, I am using the replaceScene in place of pushScene. But, with replace scene I am getting the memory-bad-access message in debugger. So, I want to popScene after using it, so that the retain count is zero. But, I am confused in using popScene. If I have a Scene1 and Scene2. I used the following to go in to Scene2. Now I need to remove Scene1 from stack. [[CCDirector sharedDirector] pushScene:Scene2]; Where should I write the popScene to popScene1. How to get the previous scene in current running scene ? Thank you/

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  • generated service mock: everything but RhinoMocks fails?

    - by hko
    I have the "quest" to search for the next Mocking Framework for my company, and basically it's down to NSubstitute (simplest syntax, but no strict mocks), FakeItEasy(best reviews, Roy Osherove bonus, and slightly better lib support than NSubstitute), Moq (best "other libs support", biggest featureset, downside: mock.Object). We definitely want to move on from RhinoMocks, e.g. because of the unusefull interactiontest error messages (it should tell me what the parameter was instead, when a verification fails). So I was pretty surprised the other day (that was yesterday) when I found out RhinoMocks could do a thing where every other mock framework fails at: Mocking an autogenerated SomethingService (a typical VS autogenerated service with a default construtor in a partial class). Please don't argue about the design.. I intend to write lightweight integration tests (and some unit tests), and I can't mess around with the service, the product is installed on too many customers system. See this code: // here the NSubstitute and FakeItEasy equivalents throw an exception.. see below TicketStoreService fakeTicketStoreService = MockRepository.GenerateMock<TicketStoreService>(); fakeTicketStoreService.Expect(service => service.DoSomething(Arg.Is(new Guid())).Return(new Guid()); fakeTicketStoreService.DoSomething(Arg.Is(new Guid())); fakeTicketStoreService.VerifyAllExpectations(); Note that DoSomething is a non-virtual methodcall in an autogenerated class. So it shouldn't work, according to common knowledge. But it does. Problem is that it's the only (non commercial) framework that can do this: Rhino.Mocks works, and verification works too FakeItEasy says it doesn't find a default constructor (probably just wrong exception message): No default constructor was found on the type SomeNamespace.TicketStoreService Moq gives something sane and understandable: Invalid setup on a non-virtual (overridable in VB) member: service=> service.DoSomething Nsubstitute gives a message System.NotSupportedException: Cannot serialize member System.ComponentModel.Component.Site of type System.ComponentModel.ISite because it is an interface. I'm really wondering what's going on here with the frameworks, except Moq. The "fancy new" frameworks seem to have an initial perf hit too, probably preparing some Type cache and serializing stuff, whilst RhinoMocks somehow manages to create a very "slim" mock without recursion. I have to admit I didn't like RhinoMocks very well, but here it shines.. unfortunately. So, is there a way to get that to work with newer (non-commercial!) mocking frameworks, or somehow get a sane error message out of Rhino.Mocks? And why can Rhino.Mocks achieve this, when clearly every Mocking framework states it can only work with virtual methods when given a concrete class? Let's not derail the discussion by talking about alternative approaches like Extract&Override or runtime-proxy Mocking frameworks like JustMock/TypeMock/Moles or the new Fakes framework, I know these, but that would be less ideal solutions, for reasons beyond this topic. Any help appreciated..

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  • Is there a way to change the maximum width of a window without using the WM_GETMINMAXINFO message?

    - by David
    I want to change the imposed Windows maximum width that a window can be resized to, for an external application's window (not my C#/WinForms program's window). The documentation of GetSystemMetrics for SM_CXMAXTRACK says: "The default maximum width of a window that has a caption and sizing borders, in pixels. This metric refers to the entire desktop. The user cannot drag the window frame to a size larger than these dimensions. A window can override this value by processing the WM_GETMINMAXINFO message." Is there a way to modify this SM_CXMAXTRACK value (either system wide or for one particular window), without processing the WM_GETMINMAXINFO message? Maybe an undocumented function, a registry setting, etc.? (Or: The documentation for MINMAXINFO.ptMaxTrackSize says: "This value is based on the size of the virtual screen and can be obtained programmatically from the system metrics SM_CXMAXTRACK and SM_CYMAXTRACK." Maybe there is a way to change the size of the virtual screen?) Thank you

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  • Core dump utility for .NET

    - by Dave
    In my past life as a COBOL mainframe developer I made extensive use of a tool called Abendaid which, in the event of an exception, would give me a complete memory dump including a formatted list of every variable in memory as well as a complete stack trace of the program with the offending statement highlighted. This made pinpointing the cause of an error much simpler and saved a lot of step-through debugging and/or trace statements. Now I've made the transition to C# and .NET web development I find that the information provided by ASP.NET only tells half the story, giving me a stack trace, but not any of the variable or class information. This makes debugging more difficult as you then have to run the process again with the debugger to try and reproduce the error, not easy with intermittent errors or with assemblies that run under the likes of SQL Server or CRM. I've looked around quite a lot for something that does this but I can't find anything obvious. Does anyone have any idea if there is one, or if not, what I'd need to start with in order to write one?

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  • Taming the malloc/free beast -- tips & tricks

    - by roufamatic
    I've been using C on some projects for a master's degree but have never built production software with it. (.NET & Javascript are my bread and butter.) Obviously, the need to free() memory that you malloc() is critical in C. This is fine, well and good if you can do both in one routine. But as programs grow, and structs deepen, keeping track of what's been malloc'd where and what's appropriate to free gets harder and harder. I've looked around on the interwebs and only found a few generic recommendations for this. What I suspect is that some of you long-time C coders have come up with your own patterns and practices to simplify this process and keep the evil in front of you. So: how do you recommend structuring your C programs to keep dynamic allocations from becoming memory leaks?

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  • Strange behavior with gcc inline assembly

    - by Chris
    When inlining assembly in gcc, I find myself regularly having to add empty asm blocks in order to keep variables alive in earlier blocks, for example: asm("rcr $1,%[borrow];" "movq 0(%[b_],%[i],8),%%rax;" "adcq %%rax,0(%[r_top],%[i],8);" "rcl $1,%[borrow];" : [borrow]"+r"(borrow) : [i]"r"(i),[b_]"r"(b_.data),[r_top]"r"(r_top.data) : "%rax","%rdx"); asm("" : : "r"(borrow) : ); // work-around to keep borrow alive ... Another example of weirdness is that the code below works great without optimizations, but with -O3 it seg-faults: ulong carry = 0,hi = 0,qh = s.data[1],ql = s.data[0]; asm("movq 0(%[b]),%%rax;" "mulq %[ql];" "movq %%rax,0(%[sb]);" "movq %%rdx,%[hi];" : [hi]"=r"(hi) : [ql]"r"(ql),[b]"r"(b.data),[sb]"r"(sb.data) : "%rax","%rdx","memory"); for (long i = 1; i < b.size; i++) { asm("movq 0(%[b],%[i],8),%%rax;" "mulq %[ql];" "xorq %%r10,%%r10;" "addq %%rax,%[hi];" "adcq %%rdx,%[carry];" "adcq $0,%%r10;" "movq -8(%[b],%[i],8),%%rax;" "mulq %[qh];" "addq %%rax,%[hi];" "adcq %%rdx,%[carry];" "adcq $0,%%r10;" "movq %[hi],0(%[sb],%[i],8);" "movq %[carry],%[hi];" "movq %%r10,%[carry];" : [carry]"+r"(carry),[hi]"+r"(hi) : [i]"r"(i),[ql]"r"(ql),[qh]"r"(qh),[b]"r"(b.data),[sb]"r"(sb.data) : "%rax","%rdx","%r10","memory"); } asm("movq -8(%[b],%[i],8),%%rax;" "mulq %[qh];" "addq %%rax,%[hi];" "adcq %%rdx,%[carry];" "movq %[hi],0(%[sb],%[i],8);" "movq %[carry],8(%[sb],%[i],8);" : [hi]"+r"(hi),[carry]"+r"(carry) : [i]"r"(long(b.size)),[qh]"r"(qh),[b]"r"(b.data),[sb]"r"(sb.data) : "%rax","%rdx","memory"); I think it has to do with the fact that it's using so many registers. Is there something I'm missing here or is the register allocation just really buggy with gcc inline assembly?

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  • What is the best way to implement an object cache with Entity Framework?

    - by Harshal
    Say I have a table of "BlogPosts" in a database and i want to be able to cache the ones that were retrieved already in memory, for further reads, I can just use a standard hashtable type memory cache like System.Web.Caching.Cache, but if i then need to update a property on one of these blog posts e.g. blogPost.Title and update the record in DB, i cannot do this without fetching it again from database as the Entity Framework context used to fetch this record when it was loaded into my cache is already disposed? How do I write code so that I am getting an object from my cache, updating one property and just calling the SaveChanges method without incurring an extra read.

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  • Oracle Professional Developer, Ver. 6.0.33 for MS-DOS

    - by Frank Developer
    Hi, I'm trying to install this fossil in DOS 6.22, which is running in Microsoft Virtual PC 2007. I'm hoping that some of you veteran Oracle developers have any recollection of in what order do these diskette images need to be loaded, since I don't have any documentation available for 6.0.33. A friend emailed me the following 720K diskette images: INSTALLE.IMG RDBMS1.IMG RDBMS2.IMG RDBMS3.IMG RSF.IMG SQLLDR1.IMG SQLLDR2.IMG UTIL1.IMG UTIL2.IMG UTIL3.IMG Within Virtual PC, I capture a diskette image, one at a time, into Drive A: VPC's floppy disk emulation supports FAT12, so the supported diskette formats can be: 720K or 1.44MB. If anyone happens to have documentation for this legacy version, I would greatly appreciate a copy of it! Thank You.

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  • Unresolved symbol when inheriting interface

    - by LeopardSkinPillBoxHat
    It's late at night here and I'm going crazy trying to solve a linker error. If I have the following abstract interface: class IArpPacketBuilder { public: IArpPacketBuilder(const DslPortId& aPortId); virtual ~IArpPacketBuilder(); // Other abstract (pure virtual methods) here... }; and I instantiate it like this: class DummyArpPacketBuilder : public IArpPacketBuilder { public: DummyArpPacketBuilder(const DslPortId& aPortId) : IArpPacketBuilder(aPortId) {} ~DummyArpPacketBuilder() {} }; why am I getting the following error when linking? Unresolved symbol references: IArpPacketBuilder::IArpPacketBuilder(DslPortId const&): ppc603_vxworks/_arpPacketQueue.o IArpPacketBuilder::~IArpPacketBuilder(): ppc603_vxworks/_arpPacketQueue.o typeinfo for IArpPacketBuilder: ppc603_vxworks/_arpPacketQueue.o *** Error code 1 IArpPacketBuilder is an abstract interface, so as long as I define the constructors and destructions in the concrete (derived) interface, I should be fine, no? Well it appears not.

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