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  • How to program a connection pool?

    - by the_drow
    Is there a known algorithm for implementing a connection pool? If not what are the known algorithms and what are their trade-offs? What design patterns are common when designing and programming a connection pool? Are there any code examples implement a connection pool using boost.asio? Is it a good idea to use a connection pool for presisting connections (not http)? How is threading related to connection pooling? When do you need a new thread?

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  • Force an object to be allocated on the heap

    - by Warren Seine
    A C++ class I'm writing uses shared_from_this() to return a valid boost::shared_ptr<>. Besides, I don't want to manage memory for this kind of object. At the moment, I'm not restricting the way the user allocates the object, which causes an error if shared_from_this() is called on a stack-allocated object. I'd like to force the object to be allocated with new and managed by a smart pointer, no matter how the user declares it. I thought it could be done through a proxy or an overloaded new operator, but I can't find a proper way of doing that. Is there a common design pattern for such usage? If it's not possible, how can I test it at compile time?

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  • How to get the next prefix in C++?

    - by Vicente Botet Escriba
    Given a sequence (for example a string "Xa"), I want to get the next prefix in order lexicographic (i.e "Xb"). As I don't want to reinvent the wheel, I'm wondering if there is any function in C++ STL or boost that can help to define this generic function easily? If not, do you think that this function can be useful? Notes The next of "aZ" should be "b". Even if the examples are strings, the function should work for any Sequence. The lexicographic order should be a template parameter of the function.

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  • TCP 30 small packets per second polutes connection with server

    - by Denis Ermolin
    I'm testing connection with flash client and cloud server(boost::asio for software) over TCP connection. My connection with server already is really poor - 120 ms ping in average. I found when i start to send packets with 2 bytes size (without tcp header) with speed 30 packets/s ping grow to 170-200 average. I think that it's really bad and my bad connection and bad cloud provider is reason for this high ping without any load. What do you think? (I tested my software and can compute about 50k packets/s so software is not a problem).

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  • How to know if the argument that is passed to the function is a class, union or enum in c++?

    - by Narek
    I want to define an operator<< for all enums, to cout the value and print that it is an enum like this: code: enum AnyEnum{A,B,C}; AnyEnum enm = A; cout << enm <<endl; output: This is an enum which has a value equal to 0 I know a way of doing this with Boost library by using is_enum struct. But I don’t understand how it works. So that's why, in general, I am interested how to identify if the veriable is a class type, union type or an enum (in compile time).

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  • Portable Socket programming in C/C++ possible?

    - by questions
    I am thinking of creating a multi-platform portable C++ server-client application. Is it even possible while using only standard libraries? If no, what other libraries are there? Are there any improvements in this direction in C++11x? Like for threads, now we have std::threads. To make it more clear.. I want something like boost::thread, which provides multiplatform portable multithreading, for networking. And why C++ doesn't have libraries(standard) for such basic things like networking?

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  • How to copy a structure with pointers to data inside (so to copy pointers and data they point to)?

    - by Kabumbus
    so I have a structure like struct GetResultStructure { int length; char* ptr; }; I need a way to make a full copy of it meaning I need a copy to have a structure with new ptr poinnting on to copy of data I had in original structure. Is It any how possible? I mean any structure I have which contains ptrs will have some fields with its lengths I need a function that would copy my structure coping all ptrs and data they point to by given array of lengthes... Any cool boost function for it? Or any way how to create such function?

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  • Quickest way to compute the number of shared elements between two vectors

    - by shn
    Suppose I have two vectors of the same size vector< pair<float, NodeDataID> > v1, v2; I want to compute how many elements from both v1 and v2 have the same NodeDataID. For example if v1 = {<3.7, 22>, <2.22, 64>, <1.9, 29>, <0.8, 7>}, and v2 = {<1.66, 7>, <0.03, 9>, <5.65, 64>, <4.9, 11>}, then I want to return 2 because there are two elements from v1 and v2 that share the same NodeDataIDs: 7 and 64. What is the quickest way to do that in C++ ? Just for information, note that the type NodeDataIDs is defined as I use boost as: typedef adjacency_list<setS, setS, undirectedS, NodeData, EdgeData> myGraph; typedef myGraph::vertex_descriptor NodeDataID; But it is not important since we can compare two NodeDataID using the operator == (that is, possible to do v1[i].second == v2[j].second)

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  • Core i5 Turboboost/C states Freezing computer

    - by Aaron Smith
    I'm not sure which, but I just had a heck of a time getting my computer to boot up and not freeze. It would run until it finished booting windows, then everything would freeze. This happened until I turned off turboboost and all the c states on the processor. What could be causing this? Is the processor going bad?

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  • can I force server to always use turboboost?

    - by javapowered
    I'm using HP DL360p Gen8 with 2 * Xeon E5-2640. I do not load CPU 100%, i load it only ~10% and so I guess turboboost is not activated. However I'm using my server for trading so I absolutely don't care about CPU loading but I always want to process my data asap. So I want server to operate using maximum 3 GHz. I.e. 90% of CPU time I don't have anything to process. 10% of CPU time I have data to process. But I need to process it ASAP. I need every single microsecond. So I want server to operate always at maximum "turboboosted" mode. Is it possible?

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  • How to bind to localStorage change event using jQuery for all browsers?

    - by David Glenn
    How do I bind a function to the HTML5 localStorage change event using jQuery? $(function () { $(window).bind('storage', function (e) { alert('storage changed'); }); localStorage.setItem('a', 'test'); }); I've tried the above but the alert is not showing. Update: It works in Firefox 3.6 but it doesn't work in Chrome 8 or IE 8 so the question should be more 'How to bind to localStorage change event using jQuery for all browsers?'

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  • How to change socket bind port of program? without source code.

    - by hunmr
    Hello everyone, PROBLEM: I have a program dummy.exe on windows. this program will bind to UDP port 5060, after started. but another program also want to bind port 5060. WHAT I HAVE DONE: using windbg to start dummy.exe, and set breakpoint on ws2_32!bind when the breakpoint hit, i changed the parameter (port value) with command ew this dummy.exe will bind to the new port, and worked well. QUESTION: How can i do that easily? write a simple windows debugger? Maybe i can hacking or modify the dummy.exe file, but how to do that? what's your way to achieve this? thanks

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  • How to bind a label inside a gridview to another table?

    - by Kolten
    I have a very standard Gridview, with Edit and Delete buttons auto-generated. It is bound to a tableadapter which is linked to my "RelationshipTypes" table. dbo.RelationshipTypes: ID, Name, OriginConfigTypeID, DestinationConfigTypeID I wish to use a label that will pull the name from the ConfigTypes table, using the "OriginConfigTypeID" and "DestinationTypeID" as the link. dbo.ConfigTypes: ID, Name My problem is, I can't automatically generate Edit and Delete buttons using an Inner Join in my dataset. Or can I? FOllowing is my code: <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" AutoGenerateDeleteButton="True" AutoGenerateEditButton="True" CssClass="TableList" DataKeyNames="ID" DataSourceID="dsRelationShipTypes1"> <Columns> <asp:BoundField DataField="ID" HeaderText="ID" InsertVisible="False" ReadOnly="True" SortExpression="ID" Visible=False/> <asp:TemplateField HeaderText="Origin" SortExpression="OriginCIType_ID"> <EditItemTemplate> &nbsp;<asp:DropDownList Enabled=true ID="DropDownList2" runat="server" DataSourceID="dsCIType1" DataTextField="Name" DataValueField="ID" SelectedValue='<%# Bind("OriginCIType_ID") %>'> </asp:DropDownList> </EditItemTemplate> <ItemTemplate> &nbsp; <asp:Label ID="Label2" runat="server" Text='<%# Bind("OriginCIType_ID") %>'></asp:Label> </ItemTemplate> </asp:TemplateField> <asp:TemplateField HeaderText="Name" SortExpression="Name"> <EditItemTemplate> <asp:TextBox ID="TextBox3" runat="server" Text='<%# Bind("Name") %>'></asp:TextBox> </EditItemTemplate> <ItemTemplate> <asp:Label ID="Label3" runat="server" Text='<%# Bind("Name") %>'></asp:Label> </ItemTemplate> </asp:TemplateField> <asp:TemplateField HeaderText="Destination" SortExpression="DestinationCIType_ID"> <EditItemTemplate> <asp:DropDownList ID="DropDownList3" runat="server" DataSourceID="dsCIType1" DataTextField="Name" DataValueField="ID" SelectedValue='<%# Bind("DestinationCIType_ID") %>'> </asp:DropDownList> </EditItemTemplate> <ItemTemplate> <asp:Label ID="Label1" runat="server" Text='<%# Bind("DestinationCIType_ID") %>'></asp:Label> </ItemTemplate> </asp:TemplateField> </Columns> </asp:GridView> So I did try to create my own edit and delete buttons, but kept receiving the error "cannot find update method" or something similar. Do I have to manually code the delete and update methods in my code-behind?

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  • How can I bind the second argument in a function but not the first (in an elegant way)?

    - by Frank Osterfeld
    Is there a way in Haskell to bind the second argument but not the first of a function without using lambda functions or defining another "local" function? Example. I have a binary function like: sub :: Int -> Int -> Int sub x y = x - y Now if I want to bind the first argument, I can do so easily using (sub someExpression): mapSubFrom5 x = map (sub 5) x *Main> mapSubFrom5 [1,2,3,4,5] [4,3,2,1,0] That works fine if I want to bind the first n arguments without "gap". If I want to bind the second argument but not the first, the two options I am aware of are more verbose: Either via another, local, function: mapSub5 x = map sub5 x where sub5 x = sub x 5 *Main> mapSub5 [1,2,3,4,5] [-4,-3,-2,-1,0] Or using lambda: mapSub5 x = map (\x -> sub x 5) x While both are working fine, I like the elegance of "sub 5" and wonder if there is a similarly elegant way to bind the n-th (n 1) argument of a function?

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  • Why does Network-Manager close when it cannot bind to any connection?

    - by Agmenor
    When Network-Manager is not able to bind my Ubuntu to any connection, after a while it closes. The icon in the notification area (or indicator area) disappears, and it does not run any more. For instance this happens when there is really no ethernet network nor wireless one. Nonetheless this is a problem, since I often plug in my ethernet cable long after having booted my computer. As a hack I therefore hit Alt + F2, and type nm-applet. But I am not satisfied with this solution, because I think it is not intuitive enough. Is there a way to keep Network-Manager always running? I have Network-Manager 0.8.1 on Ubuntu 10.10, but this has been so for a long time, at least for one year.

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  • How many textures can usually I bind at once?

    - by Avi
    I'm developing a game engine, and it's only going to work on modern (Shader model 4+) hardware. I figure that, by the time I'm done with it, that won't be such an unreasonable requirement. My question is: how many textures can I bind at once on a modern graphics card? 16 would be sufficient. Can I expect most modern graphics cards to support that amount? My GTX 460 appears to support 32, but I have no idea if that's representative of most modern video cards.

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  • How can I bind an interface to a class decided by an xml or database configuration at the launch of the application?

    - by ipohfly
    I'm re-working on the design of an existing application which is build using WebForms. Currently the plan is to work it into a MVP pattern application while using Ninject as the IoC container. The reason for Ninject to be there is that the boss had wanted a certain flexibility within the system so that we can build in different flavor of business logic in the model and let the programmer to choose which to use based on the client request, either via XML configuration or database setting. I know that Ninject have no need for XML configuration, however I'm confused on how it can help to dynamically inject the dependency into the system? Imagine I have a interface IMember and I need to bind this interface to the class decided by a xml or database configuration at the launch of the application, how can I achieve that?

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  • cannot receive UDP broadcast packets

    - by user292792
    Hello I have 2 boxes: - an embedded device (ARM Omap with linux) which I'll call "Omap". - a PC (can either be Windows or linux). Scenario 1 Both boxes are in the same network (example: my office). The Omap gets its address from a DHCP server (ex: 192.168.10.110). The PC has always the same address (ex. 192.168.10.104). I can successfully exchange UDP broadcast packets on any port. Success. Scenario 2 The 2 boxes are in a network withOUT a DHCP server. The PC has a static IP address (example: 10.10.10.20). The Omap boots, looks for a DHCP server, doesn't find it, and is in what I call "bad IP address" state. Now... Broadcasting UDP packets from the Omap works: the PC can see them. The opposite doesn't work: UDP packets broadcasted by the PC are not seen by the Omap. I am using Wireshark on another PC to verify that the packets are being sent. Failure. I tried to change the Omap ip address (with ifconfig)... no luck. What am I missing? To complete the picture, when the Omap is in Scenario 2, if I run udhcpc ... it can communicate with the DHCP server and get an IP address. I also see the packets with Wireshark. So this means that the DHCP client is able to broadcast UDP packets. (Yes, I tried to use DHCP ports 67/68 but it doesn't work). I am using Boost C++ Asio UDP sockets. Specifically, I took the multicast examples and changed them to do broadcasting. Any help is appreciated. Thanks, Benedetto

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  • Reinterpret a CGImageRef using PyObjC in Python

    - by Michael Rondinelli
    Hi, I'm doing something that's a little complicated to sum up in the title, so please bear with me. I'm writing a Python module that provides an interface to my C++ library, which provides some specialized image manipulation functionality. It would be most convenient to be able to access image buffers as CGImageRefs from Python, so they could be manipulated further using Quartz (using PyObjC, which works well). So I have a C++ function that provides a CGImageRef representation from my own image buffers, like this: CGImageRef CreateCGImageRefForImageBuffer(shared_ptr<ImageBuffer> buffer); I'm using Boost::Python to create my Python bridge. What is the easiest way for me to export this function so that I can use the CGImageRef from Python? Problems: The CGImageRef type can't be exported directly because it is a pointer to an undefined struct. So I could make a wrapper function that wraps it in a PyCObject or something to get it to send the pointer to Python. But then how do I "cast" this object to a CGImageRef from Python? Is there a better way to go about this?

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  • Instantiating class with custom allocator in shared memory

    - by recipriversexclusion
    I'm pulling my hair due to the following problem: I am following the example given in boost.interprocess documentation to instantiate a fixed-size ring buffer buffer class that I wrote in shared memory. The skeleton constructor for my class is: template<typename ItemType, class Allocator > SharedMemoryBuffer<ItemType, Allocator>::SharedMemoryBuffer( unsigned long capacity ){ m_capacity = capacity; // Create the buffer nodes. m_start_ptr = this->allocator->allocate(); // allocate first buffer node BufferNode* ptr = m_start_ptr; for( int i = 0 ; i < this->capacity()-1; i++ ) { BufferNode* p = this->allocator->allocate(); // allocate a buffer node } } My first question: Does this sort of allocation guarantee that the buffer nodes are allocated in contiguous memory locations, i.e. when I try to access the n'th node from address m_start_ptr + n*sizeof(BufferNode) in my Read() method would it work? If not, what's a better way to keep the nodes, creating a linked list? My test harness is the following: // Define an STL compatible allocator of ints that allocates from the managed_shared_memory. // This allocator will allow placing containers in the segment typedef allocator<int, managed_shared_memory::segment_manager> ShmemAllocator; //Alias a vector that uses the previous STL-like allocator so that allocates //its values from the segment typedef SharedMemoryBuffer<int, ShmemAllocator> MyBuf; int main(int argc, char *argv[]) { shared_memory_object::remove("MySharedMemory"); //Create a new segment with given name and size managed_shared_memory segment(create_only, "MySharedMemory", 65536); //Initialize shared memory STL-compatible allocator const ShmemAllocator alloc_inst (segment.get_segment_manager()); //Construct a buffer named "MyBuffer" in shared memory with argument alloc_inst MyBuf *pBuf = segment.construct<MyBuf>("MyBuffer")(100, alloc_inst); } This gives me all kinds of compilation errors related to templates for the last statement. What am I doing wrong?

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  • A map and set which uses contiguous memory and has a reserve function

    - by edA-qa mort-ora-y
    I use several maps and sets. The lack of contiguous memory, and high number of (de)allocations, is a performance bottleneck. I need a mainly STL-compatbile map and set class which can use a contiguous block of memory for internal objects (or multiple blocks). It also needs to have a reserve function so that I can preallocate for expected sizes. Before I write my own I'd like to check what is available first. Is there something in Boost which does this? Does somebody know of an available implementation elsewhere? Intrusive collection types are not usable here as the same objects need to exist in several collections. As far as I know STL memory pools are per-type, not per instance. These global pools are not efficient with respect to memory locality in mutli-cpu/core processing. Object pools don't work as the types will be shared between instance but their pool should not. In many cases a hash map may be an option in some cases.

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  • Parallel version of loop not faster than serial version

    - by Il-Bhima
    I'm writing a program in C++ to perform a simulation of particular system. For each timestep, the biggest part of the execution is taking up by a single loop. Fortunately this is embarassingly parallel, so I decided to use Boost Threads to parallelize it (I'm running on a 2 core machine). I would expect at speedup close to 2 times the serial version, since there is no locking. However I am finding that there is no speedup at all. I implemented the parallel version of the loop as follows: Wake up the two threads (they are blocked on a barrier). Each thread then performs the following: Atomically fetch and increment a global counter. Retrieve the particle with that index. Perform the computation on that particle, storing the result in a separate array Wait on a job finished barrier The main thread waits on the job finished barrier. I used this approach since it should provide good load balancing (since each computation may take differing amounts of time). I am really curious as to what could possibly cause this slowdown. I always read that atomic variables are fast, but now I'm starting to wonder whether they have their performance costs. If anybody has some ideas what to look for or any hints I would really appreciate it. I've been bashing my head on it for a week, and profiling has not revealed much.

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  • What makes deployment successful for some users and unsuccessful for others?

    - by Julien
    I am trying to deploy a Visual C++ application (developed with Microsoft Visual Studio 2008) using a Setup and Deployment Project. After installation, users on some target computers get the following error message after launching the application executable: “This application has failed to start because the application configuration is incorrect. Reinstalling the application may fix the problem.” Another user after installation could run the application properly. I cannot find the root cause of this problem, despite spending several hours on the Visual Studio help files and online forums (most postings date back to 2006). Does anyone at Stack Overflow have a suggestion? Thanks in advance. Additional details appear below. The application uses FLTK 1.1.9 for a GUI library, as well as some Boost 1.39 libraries (regex, lexical_cast, date_time, math). I made sure I am trying to deploy the release version (not the debug version) of the application. The Runtime library in the Code Generation settings is Multi-threaded DLL (/MD). The dependency walker of myapp.exe lists the following DLLs: wsock32.dll, comctl32.dll, kernel32.dll, user32.dll, gdi32.dll, shell32.dll, ole32.dll, mvcp90.dll, msvcr90.dll. In the Setup and Deployment Project, I add the following DLLs to the File System on Target Machine: fltkdlld.dll, and a folder named Microsoft.VC90.CRT with msvcm90.dll, msvcp90.dll, mcvcr90.dll and Microsoft.VC90.CRT.manifest. The installation process on the target computers getting the error message requires having the .Net Framework 3.5 installed first. Any suggestion? Thanks in advance!

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