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  • Problem with .release behavior in file_operations

    - by Yannick
    Hello, I'm dealing with a problem in a kernel module that get data from userspace using a /proc entry. I set open/write/release entries for my own defined /proc entry, and manage well to use it to get data from userspace. I handle errors in open/write functions well, and they are visible to user as open/fopen or write/fwrite/fprintf errors. But some of the errors can only be checked at close (because it's the time all the data is available). In these cases I return something different than 0, which I supposed to be in some way the value 'close' or 'fclose' will return to user. But whatever the value I return my close behave like if all is fine. To be sure I replaced all the release() code by a simple 'return(-1);' and wrote a program that open/write/close the /proc entry, and prints the close return value (and the errno). It always return '0' whatever the value I give. Behavior is the same with 'fclose', or by using shell mechanism (echo "..." /proc/my/entry). Any clue about this strange behavior that is not the one claimed in many tutorials I found? BTW I'm using RHEL5 kernel (2.6.18, redhat modified), on a 64bit system. Thanks. Regards, Yannick

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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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  • Java Generic Type and Reflection

    - by Tom Tucker
    I have some tricky generic type problem involving reflection. Here's the code. public @interface MyConstraint { Class<? extends MyConstraintValidator<?>> validatedBy(); } public interface MyConstraintValidator<T extends Annotation> { void initialize(T annotation); } /** @param annotation is annotated with MyConstraint. */ public void run(Annotation annotation) { Class<? extends MyConstraintValidator<? extends Annotation>> validatorClass = annotation.annotationType().getAnnotation(MyConstraint.class).validatedBy(); validatorClass.newInstance().initialize(annotation) // will not compile! } The run() method above will not compile because of the following error. The method initialize(capture#10-of ? extends Annotation) in the type MyConstraintValidator<capture#10-of ? extends Annotation> is not applicable for the arguments (Annotation) If I remove the wild cards, then it compiles and works fine. What would be the propert way to declare the type parameter for the vairable validatorClass? Thanks.

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  • Do you think the AI industry will ever come back?

    - by Isaiah
    I just spent some time reading about the collapse of the AI industry and realized a lot of the reason it failed was because technology was slow to catch up with their theories on when it would be available. I also read that it is believed computers that will be able to emulate human synapses may be made round 2015-2025. It's 2010 now and were getting pretty close to that time frame. I was wondering if anyone thinks that the AI industry will return as the technology lands? And if so, will it change the language market? Could Lisp like languages suddenly experience a burst of growth if it does? Idk I just thought it was interesting thinking about it.

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  • Applying a function to a custom type in F#

    - by Frederik Wordenskjold
    On my journey to learning F#, I've run into a problem I cant solve. I have defined a custom type: type BinTree = | Node of int * BinTree * BinTree | Empty I have made a function which takes a tree, traverses it, and adds the elements it visits to a list, and returns it: let rec inOrder tree = seq{ match tree with | Node (data, left, right) -> yield! inOrder left yield data; yield! inOrder right | Empty -> () } |> Seq.to_list; Now I want to create a function, similar to this, which takes a tree and a function, traverses it and applies a function to each node, then returns the tree: mapInOrder : ('a -> 'b) -> 'a BinTree -> 'b BinTree This seems easy, and it probably is! But I'm not sure how to return the tree. I've tried this: let rec mapInOrder f tree = match tree with | Node(data, left, right) -> mapInOrder f left Node(f(data), left, right) mapInOrder f right | Empty -> () but this returns a unit. I havent worked with custom types before, so I'm probably missing something there!

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  • Reason for not properly closed socket?

    - by gc
    Here is what I am trying to do: The server sends message to connected clients when new messages are available. The client, on the other hand, when connected, tries to send a message to the server using send() and then receive message using recv(), right after that, the client calls close() to close the connection. Sometimes, after the client finishes, the server tries to receive message from client will result in a 104 - "connection reset by peer" error. When this happens, Wireshark reveals that the last two segments sent by the client is: 1. an ACK acknowledging the receipt of the message sent by the server 2. a RST/ACK No FIN is sent by the client. Why is this happening and how can I close the socket "properly" at the client?

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  • Best Functional Approach

    - by dbyrne
    I have some mutable scala code that I am trying to rewrite in a more functional style. It is a fairly intricate piece of code, so I am trying to refactor it in pieces. My first thought was this: def iterate(count:Int,d:MyComplexType) = { //Generate next value n //Process n causing some side effects return iterate(count - 1, n) } This didn't seem functional at all to me, since I still have side effects mixed throughout my code. My second thought was this: def generateStream(d:MyComplexType):Stream[MyComplexType] = { //Generate next value n return Stream.cons(n, generateStream(n)) } for (n <- generateStream(initialValue).take(2000000)) { //process n causing some side effects } This seemed like a better solution to me, because at least I've isolated my functional value-generation code from the mutable value-processing code. However, this is much less memory efficient because I am generating a large list that I don't really need to store. This leaves me with 3 choices: Write a tail-recursive function, bite the bullet and refactor the value-processing code Use a lazy list. This is not a memory sensitive app (although it is performance sensitive) Come up with a new approach. I guess what I really want is a lazily evaluated sequence where I can discard the values after I've processed them. Any suggestions?

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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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  • 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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  • C: socket connection timeout

    - by The.Anti.9
    I have a simple program to check if a port is open, but I want to shorten the timeout length on the socket connection because the default is far too long. I'm not sure how to do this though. Here's the code: #include <sys/socket.h> #include <sys/time.h> #include <sys/types.h> #include <arpa/inet.h> #include <netinet/in.h> #include <errno.h> #include <fcntl.h> #include <stdio.h> #include <netdb.h> #include <stdlib.h> #include <string.h> #include <unistd.h> int main(int argc, char **argv) { u_short port; /* user specified port number */ char addr[1023]; /* will be a copy of the address entered by u */ struct sockaddr_in address; /* the libc network address data structure */ short int sock = -1; /* file descriptor for the network socket */ if (argc != 3) { fprintf(stderr, "Usage %s <port_num> <address>", argv[0]); return EXIT_FAILURE; } address.sin_addr.s_addr = inet_addr(argv[2]); /* assign the address */ address.sin_port = htons(atoi(argv[2])); /* translate int2port num */ sock = socket(AF_INET, SOCK_STREAM, 0); if (connect(sock,(struct sockaddr *)&address,sizeof(address)) == 0) { printf("%i is open\n", port); } close(sock); return 0; }

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  • AIMA in disgrace?

    - by lmsasu
    Hi, according to some reviews on Amazon, the AIMA 3rd Edition is quite a disappointment... minor update not worth the money. In your opinion, which is then a more suitable introductory textbook on artificial intelligence?

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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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  • What happens when we say "listen to a port" ?

    - by smwikipedia
    Hi, When we start a server application, we always need to speicify the port number it listens to. But how is this "listening mechanism" implemented under the hood? My current imagination is like this: The operating system associate the port number with some buffer. The server application's responsibiligy is to monitor this buffer. If there's no data in this buffer, the server application's listen operation will just block the application. When some data arrives from the wire, the operating system will know that check the data and see if it is targed at this port number. And then it will fill the buffer. And then OS will notify the blocked server application and the server application will get the data and continue to run. Question is: If the above scenario is correct, how could the opearting system know there's data arriving from wire? It cannot be a busy pooling. Is it some kind of interrupt-based mechanism? If there's too much data arriving and the buffer is not big enough, will there be data loss? Is the "listen to a port" operation really a blocking operation? Many thanks.

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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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  • From a programmer's perspective, which is your everyday Python uses?

    - by Vimvq1987
    I've finished my thesis and now having a free time. I intend to learn another language, and Python seems to be a good choice. I'll probably have to use .NET for every day works, but I heard that Python helps programmer a lot, in mean of automation. That would be great if I can write "small" Python scripts to do something automatically. From a programmer's perspective, which is your everyday Python's uses? What did it do to have your works done?

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  • Replace ",**" with a linebreak using RegEx (or something else)

    - by John
    I'm getting started with RegEx and I was wondering if anyone could help me craft a statement to convert coordinates as follows: 145.00694,-37.80421,9 145.00686,-37.80382,9 145.00595,-37.8035,16 145.00586,-37.80301,16 to 145.00694,-37.80421 145.00686,-37.80382 145.00595,-37.8035 145.00586,-37.80301 (Strip off the last comma and value and turn it into a line break.) I can't figure out how to use wildcards to do something like that. Any help would be greatly appreciated! Thanks.

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