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  • functional, bind1st and mem_fun

    - by Neil G
    Why won't this compile? #include <functional> #include <boost/function.hpp> class A { A() { typedef boost::function<void ()> FunctionCall; FunctionCall f = std::bind1st(std::mem_fun(&A::process), this); } void process() {} }; Errors: In file included from /opt/local/include/gcc44/c++/bits/stl_function.h:712, from /opt/local/include/gcc44/c++/functional:50, from a.cc:1: /opt/local/include/gcc44/c++/backward/binders.h: In instantiation of 'std::binder1st<std::mem_fun_t<void, A> >': a.cc:7: instantiated from here /opt/local/include/gcc44/c++/backward/binders.h:100: error: no type named 'second_argument_type' in 'class std::mem_fun_t<void, A>' /opt/local/include/gcc44/c++/backward/binders.h:103: error: no type named 'first_argument_type' in 'class std::mem_fun_t<void, A>' /opt/local/include/gcc44/c++/backward/binders.h:106: error: no type named 'first_argument_type' in 'class std::mem_fun_t<void, A>' /opt/local/include/gcc44/c++/backward/binders.h:111: error: no type named 'second_argument_type' in 'class std::mem_fun_t<void, A>' /opt/local/include/gcc44/c++/backward/binders.h:117: error: no type named 'second_argument_type' in 'class std::mem_fun_t<void, A>' /opt/local/include/gcc44/c++/backward/binders.h: In function 'std::binder1st<_Operation> std::bind1st(const _Operation&, const _Tp&) [with _Operation = std::mem_fun_t<void, A>, _Tp = A*]': a.cc:7: instantiated from here /opt/local/include/gcc44/c++/backward/binders.h:126: error: no type named 'first_argument_type' in 'class std::mem_fun_t<void, A>' In file included from /opt/local/include/boost/function/detail/maybe_include.hpp:13, from /opt/local/include/boost/function/detail/function_iterate.hpp:14, from /opt/local/include/boost/preprocessor/iteration/detail/iter/forward1.hpp:47, from /opt/local/include/boost/function.hpp:64, from a.cc:2: /opt/local/include/boost/function/function_template.hpp: In static member function 'static void boost::detail::function::void_function_obj_invoker0<FunctionObj, R>::invoke(boost::detail::function::function_buffer&) [with FunctionObj = std::binder1st<std::mem_fun_t<void, A> >, R = void]': /opt/local/include/boost/function/function_template.hpp:913: instantiated from 'void boost::function0<R>::assign_to(Functor) [with Functor = std::binder1st<std::mem_fun_t<void, A> >, R = void]' /opt/local/include/boost/function/function_template.hpp:722: instantiated from 'boost::function0<R>::function0(Functor, typename boost::enable_if_c<boost::type_traits::ice_not::value, int>::type) [with Functor = std::binder1st<std::mem_fun_t<void, A> >, R = void]' /opt/local/include/boost/function/function_template.hpp:1064: instantiated from 'boost::function<R()>::function(Functor, typename boost::enable_if_c<boost::type_traits::ice_not::value, int>::type) [with Functor = std::binder1st<std::mem_fun_t<void, A> >, R = void]' a.cc:7: instantiated from here /opt/local/include/boost/function/function_template.hpp:153: error: no match for call to '(std::binder1st<std::mem_fun_t<void, A> >) ()'

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  • Efficient algorithm to distribute work?

    - by Zwei Steinen
    It's a bit complicated to explain but here we go. We have problems like this (code is pseudo-code, and is only for illustrating the problem. Sorry it's in java. If you don't understand, I'd be glad to explain.). class Problem { final Set<Integer> allSectionIds = { 1,2,4,6,7,8,10 }; final Data data = //Some data } And a subproblem is: class SubProblem { final Set<Integer> targetedSectionIds; final Data data; SubProblem(Set<Integer> targetedSectionsIds, Data data){ this.targetedSectionIds = targetedSectionIds; this.data = data; } } Work will look like this, then. class Work implements Runnable { final Set<Section> subSections; final Data data; final Result result; Work(Set<Section> subSections, Data data) { this.sections = SubSections; this.data = data; } @Override public void run(){ for(Section section : subSections){ result.addUp(compute(data, section)); } } } Now we have instances of 'Worker', that have their own state sections I have. class Worker implements ExecutorService { final Map<Integer,Section> sectionsIHave; { sectionsIHave = {1:section1, 5:section5, 8:section8 }; } final ExecutorService executor = //some executor. @Override public void execute(SubProblem problem){ Set<Section> sectionsNeeded = fetchSections(problem.targetedSectionIds); super.execute(new Work(sectionsNeeded, problem.data); } } phew. So, we have a lot of Problems and Workers are constantly asking for more SubProblems. My task is to break up Problems into SubProblem and give it to them. The difficulty is however, that I have to later collect all the results for the SubProblems and merge (reduce) them into a Result for the whole Problem. This is however, costly, so I want to give the workers "chunks" that are as big as possible (has as many targetedSections as possible). It doesn't have to be perfect (mathematically as efficient as possible or something). I mean, I guess that it is impossible to have a perfect solution, because you can't predict how long each computation will take, etc.. But is there a good heuristic solution for this? Or maybe some resources I can read up before I go into designing? Any advice is highly appreciated!

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  • help me understand cuda

    - by scatman
    i am having some troubles understanding threads in NVIDIA gpu architecture with cuda. please could anybody clarify these info: an 8800 gpu has 16 SMs with 8 SPs each. so we have 128 SPs. i was viewing stanford's video presentation and it was saying that every SP is capable of running 96 threads cuncurrently. does this mean that it (SP) can run 96/32=3 warps concurrently? moreover, since every SP can run 96 threads and we have 8 SPs in every SM. does this mean that every SM can run 96*8=768 threads concurrently?? but if every SM can run a single Block at a time, and the maximum number of threads in a block is 512, so what is the purpose of running 768 threads concurrently and have a max of 512 threads? a more general question is:how are blocks,threads,and warps distributed to SMs and SPs? i read that every SM gets a single block to execute at a time and threads in a block is divided into warps (32 threads), and SPs execute warps.

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  • How do I split up a long value (32 bits) into four char variables (8bits) using C?

    - by Jordan S
    I have a 32 bit long variable, CurrentPosition, that I want to split up into 4, 8bit characters. How would I do that most efficiently in C? I am working with an 8bit MCU, 8051 architectecture. unsigned long CurrentPosition = 7654321; unsigned char CP1 = 0; unsigned char CP2 = 0; unsigned char CP3 = 0; unsigned char CP4 = 0; // What do I do next? Should I just reference the starting address of CurrentPosition with a pointer and then add 8 two that address four times? It is little Endian. ALSO I want CurrentPosition to remain unchanged.

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  • file_operations Question, how do i know if a process that opened a file for writing has decided to c

    - by djTeller
    Hi Kernel Gurus, I'm currently writing a simple "multicaster" module. Only one process can open a proc filesystem file for writing, and the rest can open it for reading. To do so i use the inode_operation .permission callback, I check the operation and when i detect someone open a file for writing I set a flag ON. i need a way to detect if a process that opened a file for writing has decided to close the file so i can set the flag OFF, so someone else can open for writing. Currently in case someone is open for writing i save the current-pid of that process and when the .close callback is called I check if that process is the one I saved earlier. Is there a better way to do that? Without saving the pid, perhaps checking the files that the current process has opened and it's permission... Thanks!

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  • How to handle server-client requests

    - by Layne
    Currently I'm working on a Server-Client system which will be the backbone of my application. I have to find the best way to send requests and handle them on the server-side. The server-side should be able to handle requests like this one: getPortfolio -i 2 -d all In an old project I decided to send such a request as string and the server application had to look up the first part of the string ("getPortfolio"). Afterwards the server application had to find the correct method in a map which linked the methods with the the first part of the string ("getPortfolio"). The second part ("-i 2 -d all") got passed as parameter and the method itself had to handle this string/parameter. I doubt that this is the best solution in order to handle many different requests. Rgds Layne

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  • International JRE6 or JDK6 or reading a file in "cp037" encoding scheme

    - by Reddy
    I have been trying to read a file in "cp037" encoding scheme using JAVA. I able to read a file in basic encoding schemes like UTF-8, UTF16 etc...After a bit of research on the internet i came to know that we need charset.jar or international version of JRE be installed to support extended encoding schemes. Can anyone send me a link for international version of JRE6 or JDK6. or is there any better way that i could read a file in cp037 encoding scheme. P.S: cp037 is a character encoding scheme supported by IBM Mainframes. All i need is to display a file in windows, which is being generated on IBM Mainframes machine, using a java program. Thanks in advance for your help... :-)

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  • How do you manage tasks within your work?

    - by Michael
    Just wondering how you all manage your workload effectively when there's a lot of your plate? What do you do to break it down into bite-size chunks and how do you track progress of each task? Do you find TDD helps to focus your attention of getting areas of functionality complete before moving onto the next one? I quite often find myself getting a bit overwhelmed when I have an involving task on the go (even if it can be broken down into lots of small chunks), even though I know I'm more than capable of doing the work. We have a kind of agile approach Interested to hear how everyone manages things effectively.

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  • running examples in package-Ex.R failed

    - by swarna
    Hi,My name is Swarna,I'm new to R,when i was checking my package i got a error message saying "Running examples in package-Ex.R failed" and series of statement saying where error might have occurred name of the package -package flush(stderr());flush(stdout()) name: title alias keywords Can any one please help me with this. Thank you,

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  • recvfrom returns invalid argument when *from* is passed

    - by Aditya Sehgal
    I am currently writing a small UDP server program in linux. The UDP server will receive packets from two different peers and will perform different operations based on from which peer it received the packet. I am trying to determine the source from where I receive the packet. However, when select returns and recvfrom is called, it returns with an error of Invalid Argument. If I pass NULL as the second last arguments, recvfrom succeeds. I have tried declaring fromAddr as struct sockaddr_storage, struct sockaddr_in, struct sockaddr without any success. Is their something wrong with this code? Is this the correct way to determine the source of the packet? The code snippet follows. ` /*TODO : update for TCP. use recv */ if((pkInfo->rcvLen=recvfrom(psInfo->sockFd, pkInfo->buffer, MAX_PKTSZ, 0, /* (struct sockaddr*)&fromAddr,*/ NULL, &(addrLen) )) < 0) { perror("RecvFrom failed\n"); } else { /*Apply Filter */ #if 0 struct sockaddr_in* tmpAddr; tmpAddr = (struct sockaddr_in* )&fromAddr; printf("Received Msg From %s\n",inet_ntoa(tmpAddr->sin_addr)); #endif printf("Packet Received of len = %d\n",pkInfo->rcvLen); } `

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  • Serializing persistent/functional data structures

    - by Rob
    Persistent data structures depend on the sharing of structure for efficiency. For an example, see here. How can I preserve the structure sharing when I serialize the data structures and write them to a file or database? If I just naively traverse the datastructures, I'll store the correct values, but I'll lose the structure sharing. I'd like to be able to save data-structures with shared components to a file, restore them, and still have most of the structure shared in the restored data.

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  • simple question on C

    - by lego69
    I have this snippet of the code char *str = “123”; if(str[0] == 1) printf("Hello\n"); why I can't receive my Hello thanks in advance! how exactly compiler does this comparison if(str[0] == 1)?

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  • Picking the right language

    - by simion
    I am a student at University so my experience is limited, hence the question. If someone says to you, here is a task to code, what are you looking at in order to choose the language or paradigm in which you will do it in? Hope the question makes sense?

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  • Result of Long Positive Integers & Search and element in array..

    - by AGeek
    Hi, I have two Questions for which I cannot find answers by googling, but I find these questions very important for preparation.. Kindly explain only the logic, I will be able to code. In Search of Efficient Logic..... in terms of Memory and Time. WAP to add two long positive integers. What Data structure / data type we can use to store the numbers and result. What is the best way to search an element from an array in shortest time. Size of the array could be large enough, and any elements could be stored in the array(i.e. no range). Thanks.

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  • Linux - Programmatically write to a proc file

    - by Zach
    I have found several examples online where we can create a proc file, assign read and write methods that are called every time the proc file is opened for read or written to. However, I can't seem to find any documentation on how to programatically write to a proc file. Ideally, I would like to add a timestamp with other user details every time the proc file is opened for read or for write. Again, I've found where I can add the read and write functions that are triggered when the proc file is opened, but I can't find documentation on how to actually write to a proc file programatically. This would be different from a regular IO read/write, correct?

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  • tutorials/books to create a plugin/module/library?

    - by fayer
    i wonder if there are tutorials/books explaining how you create a library/plugin/module for other to implement? libraries/frameworks like solr, doctrine, codeigniter etc. cause it seems that they follow the same pattern. having one "bootstrap" file to load configurations, other classes and so on. i aim to understand the basics, so i can create a such library. cause at the moment i want to code an address book that other can use. just include a bootstrap file and they are ready to use my classes (like Doctrine). recommendations of sources to learn these things of stuff? you experienced guys, how did you learn it? thanks.

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  • heeeeeeeeeeeeeeelp

    - by Yassin
    plz help me i need to make asimple calculator using c for example (1+2-44)/7 but it requiers reverse polish notation which i cant under stand if any one could help me giving me the code i'll be greatfull cause i have an exam after 2 days

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