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  • Evaluating a function at a particular value in parallel

    - by Gaurav Kalra
    Hi. The question may seem vague, but let me explain it. Suppose we have a function f(x,y,z ....) and we need to find its value at the point (x1,y1,z1 .....). The most trivial approach is to just replace (x,y,z ...) with (x1,y1,z1 .....). Now suppose that the function is taking a lot of time in evaluation and I want to parallelize the algorithm to evaluate it. Obviously it will depend on the nature of function, too. So my question is: what are the constraints that I have to look for while "thinking" to parallelize f(x,y,z...)? If possible, please share links to study.

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  • math library in gcc

    - by Betamoo
    I am writing a program on linux gcc... When I tried to include <math.h> I found that I need to link math library by using command gcc -lm But I am searching for another way to link the math library 'in code', that does not require the user to compile using any options.. Can gcc -lm be done in c code using #pragma or something? EDIT: I have changed -ml to -lm

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  • MPAPI vs MPI.NET vs ?

    - by Olexandr
    I'm working on college project. I have to develop distributed computing system. And i decided to do some research to make this task fun :) I've found MPAPI and MPI.NET libraries. Yes, they are .NET libraries(Mono, in my case). Why .NET ? I'm choosing between Ada, C++ and C# so to i've choosed C# because of lower development time. I have two goals: Simplicity; Performance; Cluster computing. So, what to choose - MPAPI or MPI.NET or something else ?

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  • XML RSS to HTML parser doesn't work

    - by mstr
    I'm using MCX (I don't even know if someone here is familiar with it, pretty unkown derivate of COBOL and Fortran, look it up in google when you don't believe me) Note: I'm using MCX on the MCX-WebServices server as it does neither support apache or ISS, mabye that is one problem. The thing is that I want to use the XML library to read in an XML file and convert it into an output format readable by the user. The XML lib already has all the functions I need for that, yet my program fails. #!usr/bin/mcx $PGRM.ID: index.mcx $PGRM.AT: /mstr SHOWERROR: WRITE XML.LastError --> OUTPUT DO_FLUSH xcit end\ MAIN: IMPORT Extras.XML USE Extras $XML_RSS_FILE: XML.ReadIn "rss.xml" ! $XML_RSS_FILE --> GOTO SHOWERROR $XML_RSS: XML.FormatRSS1 <-- $XML_RSS_FILE ! $XML_RSS --> GOTO SHOWERROR WRITE $XML_RSS --> OUTPUT DO_FLUSH FLUSH xcit end\ Program output: Nothing The rss.xml file 100% exists and is readable Thanks in advance

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  • n++ vs n=n+1. Which one is faster

    - by piemesons
    Somebody asked me Is n++ faster than n=n+1? My answer:-- ++ is a unary operator in C which(n++) takes only one machine instruction to execute while n=n+1 takes more than one machine instructions to execute. Anyone correct me if I am wrong, but in Assembler it take something like this: n++: inc n n = n + 1; mov ax n add ax 1 mov n ax its not exactli this, but it's near it.but in most cases a good compiler will change n = n + 1 to ++n.So A good compiler will generate same code for both and hence the same time to execute.

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  • FTP to SFTP in shell scripting

    - by Kimi
    This script is to connect to different servers and copy a file from a loaction defined. It is mandatory to use sftp and not ftp. #!/usr/bin/ksh -xvf Detail="jyotibo|snv4915|/tlmusr1/tlm/rt/jyotibo/JyotiBo/ jyotibo|snv4915|/tlmusr1/tlm/rt/jyotibo/JyotiBo/" password=Unix11! c_filename=import.log localpath1=`pwd` for i in $Detail do echo $i UserName=`echo $i | cut -d'|' -f1` echo $UserName remotehost=`echo $i | cut -d'|' -f2` echo $remotehost remote_path=`echo $i | cut -d'|' -f3` echo $remote_path { echo "open $remotehost user $UserName $password lcd $localpath1 cd $remote_path bi prompt mget $c_filename prompt " } |ftp -i -n -v 2>&1 done I want to do the similar thing using sftp instead of ftp.

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  • How to declare a vector or array of reducer objects in Cilk++?

    - by Jin
    Hi All, I had a problem when I am using Cilk++, an extension to C++ for parallel computing. I found that I can't declare a vector of reducer objects: typedef cilk::reducer_opadd<int> T_reducer; vector<T_reducer> bitmiss_vec; for (int i = 0; i < 24; ++i) { T_reducer r; bitmiss_vec.push_back(r); } However, when I compile the code with Cilk++, it complains at the push_back() line: cilk++ geneAttack.cilk -O1 -g -lcilkutil -o geneAttack /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/cilk++/reducer_opadd.h: In member function ‘void __gnu_cxx::new_allocator<_Tp>::construct(_Tp*, const _Tp&) [with _Tp = cilk::reducer_opadd<int>]’: /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_vector.h:601: instantiated from ‘void std::vector<_Tp, _Alloc>::push_back(const _Tp&) [with _Tp = cilk::reducer_opadd<int>, _Alloc = std::allocator<cilk::reducer_opadd<int> >]’ geneAttack.cilk:667: instantiated from here /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/cilk++/reducer_opadd.h:229: error: ‘cilk::reducer_opadd<Type>::reducer_opadd(const cilk::reducer_opadd<Type>&) [with Type = int]’ is private /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/ext/new_allocator.h:107: error: within this context /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/cilk++/reducer_opadd.h: In member function ‘void std::vector<_Tp, _Alloc>::_M_insert_aux(__gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> >, const _Tp&) [with _Tp = cilk::reducer_opadd<int>, _Alloc = std::allocator<cilk::reducer_opadd<int> >]’: /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_vector.h:605: instantiated from ‘void std::vector<_Tp, _Alloc>::push_back(const _Tp&) [with _Tp = cilk::reducer_opadd<int>, _Alloc = std::allocator<cilk::reducer_opadd<int> >]’ geneAttack.cilk:667: instantiated from here /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/cilk++/reducer_opadd.h:229: error: ‘cilk::reducer_opadd<Type>::reducer_opadd(const cilk::reducer_opadd<Type>&) [with Type = int]’ is private /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/vector.tcc:252: error: within this context /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_vector.h:605: instantiated from ‘void std::vector<_Tp, _Alloc>::push_back(const _Tp&) [with _Tp = cilk::reducer_opadd<int>, _Alloc = std::allocator<cilk::reducer_opadd<int> >]’ geneAttack.cilk:667: instantiated from here /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/cilk++/reducer_opadd.h:230: error: ‘cilk::reducer_opadd<Type>& cilk::reducer_opadd<Type>::operator=(const cilk::reducer_opadd<Type>&) [with Type = int]’ is private /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/vector.tcc:256: error: within this context /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/cilk++/reducer_opadd.h: In static member function ‘static _BI2 std::__copy_backward<_BoolType, std::random_access_iterator_tag>::__copy_b(_BI1, _BI1, _BI2) [with _BI1 = cilk::reducer_opadd<int>*, _BI2 = cilk::reducer_opadd<int>*, bool _BoolType = false]’: /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_algobase.h:465: instantiated from ‘_BI2 std::__copy_backward_aux(_BI1, _BI1, _BI2) [with _BI1 = cilk::reducer_opadd<int>*, _BI2 = cilk::reducer_opadd<int>*]’ /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_algobase.h:474: instantiated from ‘static _BI2 std::__copy_backward_normal<<anonymous>, <anonymous> >::__copy_b_n(_BI1, _BI1, _BI2) [with _BI1 = cilk::reducer_opadd<int>*, _BI2 = cilk::reducer_opadd<int>*, bool <anonymous> = false, bool <anonymous> = false]’ /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_algobase.h:540: instantiated from ‘_BI2 std::copy_backward(_BI1, _BI1, _BI2) [with _BI1 = cilk::reducer_opadd<int>*, _BI2 = cilk::reducer_opadd<int>*]’ /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/vector.tcc:253: instantiated from ‘void std::vector<_Tp, _Alloc>::_M_insert_aux(__gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> >, const _Tp&) [with _Tp = cilk::reducer_opadd<int>, _Alloc = std::allocator<cilk::reducer_opadd<int> >]’ /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_vector.h:605: instantiated from ‘void std::vector<_Tp, _Alloc>::push_back(const _Tp&) [with _Tp = cilk::reducer_opadd<int>, _Alloc = std::allocator<cilk::reducer_opadd<int> >]’ geneAttack.cilk:667: instantiated from here /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/cilk++/reducer_opadd.h:230: error: ‘cilk::reducer_opadd<Type>& cilk::reducer_opadd<Type>::operator=(const cilk::reducer_opadd<Type>&) [with Type = int]’ is private /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_algobase.h:433: error: within this context /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/cilk++/reducer_opadd.h: In function ‘void std::_Construct(_T1*, const _T2&) [with _T1 = cilk::reducer_opadd<int>, _T2 = cilk::reducer_opadd<int>]’: /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_uninitialized.h:87: instantiated from ‘_ForwardIterator std::__uninitialized_copy_aux(_InputIterator, _InputIterator, _ForwardIterator, std::__false_type) [with _InputIterator = cilk::reducer_opadd<int>*, _ForwardIterator = cilk::reducer_opadd<int>*]’ /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_uninitialized.h:114: instantiated from ‘_ForwardIterator std::uninitialized_copy(_InputIterator, _InputIterator, _ForwardIterator) [with _InputIterator = cilk::reducer_opadd<int>*, _ForwardIterator = cilk::reducer_opadd<int>*]’ /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_uninitialized.h:254: instantiated from ‘_ForwardIterator std::__uninitialized_copy_a(_InputIterator, _InputIterator, _ForwardIterator, std::allocator<_Tp>) [with _InputIterator = cilk::reducer_opadd<int>*, _ForwardIterator = cilk::reducer_opadd<int>*, _Tp = cilk::reducer_opadd<int>]’ /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/vector.tcc:275: instantiated from ‘void std::vector<_Tp, _Alloc>::_M_insert_aux(__gnu_cxx::__normal_iterator<typename std::_Vector_base<_Tp, _Alloc>::_Tp_alloc_type::pointer, std::vector<_Tp, _Alloc> >, const _Tp&) [with _Tp = cilk::reducer_opadd<int>, _Alloc = std::allocator<cilk::reducer_opadd<int> >]’ /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_vector.h:605: instantiated from ‘void std::vector<_Tp, _Alloc>::push_back(const _Tp&) [with _Tp = cilk::reducer_opadd<int>, _Alloc = std::allocator<cilk::reducer_opadd<int> >]’ geneAttack.cilk:667: instantiated from here /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/cilk++/reducer_opadd.h:229: error: ‘cilk::reducer_opadd<Type>::reducer_opadd(const cilk::reducer_opadd<Type>&) [with Type = int]’ is private /usr/local/cilk/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.2.4/../../../../include/c++/4.2.4/bits/stl_construct.h:81: error: within this context make: *** [geneAttack] Error 1 jinchen@galactica:~/workspace/biometrics/genAttack$ make cilk++ geneAttack.cilk -O1 -g -lcilkutil -o geneAttack geneAttack.cilk: In function ‘int cilk cilk_main(int, char**)’: geneAttack.cilk:670: error: expected primary-expression before ‘,’ token geneAttack.cilk:670: error: expected primary-expression before ‘}’ token geneAttack.cilk:674: error: ‘bitmiss_vec’ was not declared in this scope make: *** [geneAttack] Error 1 The Cilk++ manule says it supports array/vector of reducers, although there are performance issues to consider: "If you create a large number of reducers (for example, an array or vector of reducers) you must be aware that there is an overhead at steal and reduce that is proportional to the number of reducers in the program. " Anyone knows what is going on? How should I declare/use vector of reducers? Thank you

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  • How to gain greater control of network packets on Android

    - by mauvehead
    I'm looking to design an application that will require some deep control over IP packets. Looking over the reference guide on the developers site at Android I see very limited control over packets from java.net:SocketOptions and java.net:DatagramPacket. Specifically I'm looking to control the individual bits within the packet to set TCP Flags, SYN/ACK/RST, and so forth. Based on the docs I am assuming I cannot do this within the Java API provided by Android and I'm guessing I'll have to do it some other way? Anyone have any insight on this?

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  • Channels in Socket.io

    - by mat3001
    Hi, I am trying to broadcast a message through the Node.js service socket.io (http://socket.io/) to certain subset of all subscribers. To be more exact, I would like to use channels that users can subscribe to, in order to efficiently push messages to a couple hundred people at the same time. I'm not really sure if addEvent('channel_name',x) is the way to go. I have not found anything in the docs. Any ideas? Thanks Mat

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  • Is it possible to call a user-space callback function from kernel space in Linux (ioctl)?

    - by Makis
    Is it possible to expand the ioctl interface in Linux so that the user-space application can send a pointer to a function to the kernel space driver? I'm in particular thinking of ways to handle the stream in user-controllable way but doing it in the kernel. Those operations could be attached to the kernel module but this would make development a lot easier as I wouldn't need to mess with the kernel during development. More specifically, this would be the process: Data is read by the driver to a buffer. Data is handled by these user-defined functions in place. Some more handling is done, possibly with some HW blocks. Data is used by a user-space application.

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  • Jquery each loop with json array

    - by Ben
    I'm trying to use Jquery's each loop to go through this Json and add it to a div named #contentHere. The Json is as follows: { "justIn": [ { "textId": "123", "text": "Hello", "textType": "Greeting" }, { "textId": "514", "text":"What's up?", "textType": "Question" }, { "textId": "122", "text":"Come over here", "textType": "Order" } ], "recent": [ { "textId": "1255", "text": "Hello", "textType": "Greeting" }, { "textId": "6564", "text":"What's up?", "textType": "Question" }, { "textId": "0192", "text":"Come over here", "textType": "Order" } ], "old": [ { "textId": "5213", "text": "Hello", "textType": "Greeting" }, { "textId": "9758", "text":"What's up?", "textType": "Question" }, { "textId": "7655", "text":"Come over here", "textType": "Order" } ] } I'm getting this Json through use of this code: $.get("data.php", function(data){ }) Any solutions?

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  • Why Do You Use Delphi?

    - by lkessler
    Nick Bradbury (the author of HomeSite, TopStyle and FeedDemon) just posted a fascinating explanation of why he uses Delphi: http://nick.typepad.com/blog/2009/07/why-i-use-delphi.html I'd like to know if there are other reasons. Why do you use Delphi? (I'm making this community wiki from the onset. I'm interested in hearing your answers, not in points.)

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  • Find three numbers appeared only once

    - by shilk
    In a sequence of length n, where n=2k+3, that is there are k unique numbers appeared twice and three numbers appeared only once. The question is: how to find the three unique numbers that appeared only once? for example, in sequence 1 1 2 6 3 6 5 7 7 the three unique numbers are 2 3 5. Note: 3<=n<1e6 and the number will range from 1 to 2e9 Memory limits: 1000KB , this implies that we can't store the whole sequence. Method I have tried(Memory limit exceed): I initialize a tree, and when read in one number I try to remove it from the tree, if the remove returns false(not found), I add it to the tree. Finally, the tree has the three numbers. It works, but is Memory limit exceed. I know how to find one or two such number(s) using bit manipulation. So I wonder if we can find three using the same method(or some method similar)? Method to find one/two number(s) appeared only once: If there is one number appeared only once, we can apply XOR to the sequence to find it. If there are two, we can first apply XOR to the sequence, then separate the sequence into 2 parts by one bit of the result that is 1, and again apply XOR to the 2 parts, and we will find the answer.

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  • Persistent (purely functional) Red-Black trees on disk performance

    - by Waneck
    I'm studying the best data structures to implement a simple open-source object temporal database, and currently I'm very fond of using Persistent Red-Black trees to do it. My main reasons for using persistent data structures is first of all to minimize the use of locks, so the database can be as parallel as possible. Also it will be easier to implement ACID transactions and even being able to abstract the database to work in parallel on a cluster of some kind. The great thing of this approach is that it makes possible implementing temporal databases almost for free. And this is something quite nice to have, specially for web and for data analysis (e.g. trends). All of this is very cool, but I'm a little suspicious about the overall performance of using a persistent data structure on disk. Even though there are some very fast disks available today, and all writes can be done asynchronously, so a response is always immediate, I don't want to build all application under a false premise, only to realize it isn't really a good way to do it. Here's my line of thought: - Since all writes are done asynchronously, and using a persistent data structure will enable not to invalidate the previous - and currently valid - structure, the write time isn't really a bottleneck. - There are some literature on structures like this that are exactly for disk usage. But it seems to me that these techniques will add more read overhead to achieve faster writes. But I think that exactly the opposite is preferable. Also many of these techniques really do end up with a multi-versioned trees, but they aren't strictly immutable, which is something very crucial to justify the persistent overhead. - I know there still will have to be some kind of locking when appending values to the database, and I also know there should be a good garbage collecting logic if not all versions are to be maintained (otherwise the file size will surely rise dramatically). Also a delta compression system could be thought about. - Of all search trees structures, I really think Red-Blacks are the most close to what I need, since they offer the least number of rotations. But there are some possible pitfalls along the way: - Asynchronous writes -could- affect applications that need the data in real time. But I don't think that is the case with web applications, most of the time. Also when real-time data is needed, another solutions could be devised, like a check-in/check-out system of specific data that will need to be worked on a more real-time manner. - Also they could lead to some commit conflicts, though I fail to think of a good example of when it could happen. Also commit conflicts can occur in normal RDBMS, if two threads are working with the same data, right? - The overhead of having an immutable interface like this will grow exponentially and everything is doomed to fail soon, so this all is a bad idea. Any thoughts? Thanks! edit: There seems to be a misunderstanding of what a persistent data structure is: http://en.wikipedia.org/wiki/Persistent_data_structure

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  • Reading a child process's /proc/pid/mem file from the parent

    - by Amittai Aviram
    In the program below, I am trying to cause the following to happen: Process A assigns a value to a stack variable a. Process A (parent) creates process B (child) with PID child_pid. Process B calls function func1, passing a pointer to a. Process B changes the value of variable a through the pointer. Process B opens its /proc/self/mem file, seeks to the page containing a, and prints the new value of a. Process A (at the same time) opens /proc/child_pid/mem, seeks to the right page, and prints the new value of a. The problem is that, in step 6, the parent only sees the old value of a in /proc/child_pid/mem, while the child can indeed see the new value in its /proc/self/mem. Why is this the case? Is there any way that I can get the parent to to see the child's changes to its address space through the /proc filesystem? #include <fcntl.h> #include <stdbool.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/stat.h> #include <sys/wait.h> #include <unistd.h> #define PAGE_SIZE 0x1000 #define LOG_PAGE_SIZE 0xc #define PAGE_ROUND_DOWN(v) ((v) & (~(PAGE_SIZE - 1))) #define PAGE_ROUND_UP(v) (((v) + PAGE_SIZE - 1) & (~(PAGE_SIZE - 1))) #define OFFSET_IN_PAGE(v) ((v) & (PAGE_SIZE - 1)) # if defined ARCH && ARCH == 32 #define BP "ebp" #define SP "esp" #else #define BP "rbp" #define SP "rsp" #endif typedef struct arg_t { int a; } arg_t; void func1(void * data) { arg_t * arg_ptr = (arg_t *)data; printf("func1: old value: %d\n", arg_ptr->a); arg_ptr->a = 53; printf("func1: address: %p\n", &arg_ptr->a); printf("func1: new value: %d\n", arg_ptr->a); } void expore_proc_mem(void (*fn)(void *), void * data) { off_t frame_pointer, stack_start; char buffer[PAGE_SIZE]; const char * path = "/proc/self/mem"; int child_pid, status; int parent_to_child[2]; int child_to_parent[2]; arg_t * arg_ptr; off_t child_offset; asm volatile ("mov %%"BP", %0" : "=m" (frame_pointer)); stack_start = PAGE_ROUND_DOWN(frame_pointer); printf("Stack_start: %lx\n", (unsigned long)stack_start); arg_ptr = (arg_t *)data; child_offset = OFFSET_IN_PAGE((off_t)&arg_ptr->a); printf("Address of arg_ptr->a: %p\n", &arg_ptr->a); pipe(parent_to_child); pipe(child_to_parent); bool msg; int child_mem_fd; char child_path[0x20]; child_pid = fork(); if (child_pid == -1) { perror("fork"); exit(EXIT_FAILURE); } if (!child_pid) { close(child_to_parent[0]); close(parent_to_child[1]); printf("CHILD (pid %d, parent pid %d).\n", getpid(), getppid()); fn(data); msg = true; write(child_to_parent[1], &msg, 1); child_mem_fd = open("/proc/self/mem", O_RDONLY); if (child_mem_fd == -1) { perror("open (child)"); exit(EXIT_FAILURE); } printf("CHILD: child_mem_fd: %d\n", child_mem_fd); if (lseek(child_mem_fd, stack_start, SEEK_SET) == (off_t)-1) { perror("lseek"); exit(EXIT_FAILURE); } if (read(child_mem_fd, buffer, sizeof(buffer)) != sizeof(buffer)) { perror("read"); exit(EXIT_FAILURE); } printf("CHILD: new value %d\n", *(int *)(buffer + child_offset)); read(parent_to_child[0], &msg, 1); exit(EXIT_SUCCESS); } else { printf("PARENT (pid %d, child pid %d)\n", getpid(), child_pid); printf("PARENT: child_offset: %lx\n", child_offset); read(child_to_parent[0], &msg, 1); printf("PARENT: message from child: %d\n", msg); snprintf(child_path, 0x20, "/proc/%d/mem", child_pid); printf("PARENT: child_path: %s\n", child_path); child_mem_fd = open(path, O_RDONLY); if (child_mem_fd == -1) { perror("open (child)"); exit(EXIT_FAILURE); } printf("PARENT: child_mem_fd: %d\n", child_mem_fd); if (lseek(child_mem_fd, stack_start, SEEK_SET) == (off_t)-1) { perror("lseek"); exit(EXIT_FAILURE); } if (read(child_mem_fd, buffer, sizeof(buffer)) != sizeof(buffer)) { perror("read"); exit(EXIT_FAILURE); } printf("PARENT: new value %d\n", *(int *)(buffer + child_offset)); close(child_mem_fd); printf("ENDING CHILD PROCESS.\n"); write(parent_to_child[1], &msg, 1); if (waitpid(child_pid, &status, 0) == -1) { perror("waitpid"); exit(EXIT_FAILURE); } } } int main(void) { arg_t arg; arg.a = 42; printf("In main: address of arg.a: %p\n", &arg.a); explore_proc_mem(&func1, &arg.a); return EXIT_SUCCESS; } This program produces the output below. Notice that the value of a (boldfaced) differs between parent's and child's reading of the /proc/child_pid/mem file. In main: address of arg.a: 0x7ffffe1964f0 Stack_start: 7ffffe196000 Address of arg_ptr-a: 0x7ffffe1964f0 PARENT (pid 20376, child pid 20377) PARENT: child_offset: 4f0 CHILD (pid 20377, parent pid 20376). func1: old value: 42 func1: address: 0x7ffffe1964f0 func1: new value: 53 PARENT: message from child: 1 CHILD: child_mem_fd: 4 PARENT: child_path: /proc/20377/mem CHILD: new value 53 PARENT: child_mem_fd: 7 PARENT: new value 42 ENDING CHILD PROCESS.

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  • Modeling software for network serialization protocol design

    - by Aurélien Vallée
    Hello, I am currently designing a low level network serialization protocol (in fact, a refinement of an existing protocol). As the work progress, pen and paper documents start to show their limits: i have tons of papers, new and outdated merged together, etc... And i can't show anything to anyone since i describe the protocol using my own notation (a mix of flow chart & C structures). I need a software that would help me to design a network protocol. I should be able to create structures, fields, their sizes, their layout, etc... and the software would generate some nice UMLish diagrams.

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  • How can I generate the Rowland prime sequence idiomatically in J?

    - by Gregory Higley
    If you're not familiar with the Rowland prime sequence, you can find out about it here. I've created an ugly, procedural monadic verb in J to generate the first n terms in this sequence, as follows: rowland =: monad define result =. 0 $ 0 t =. 1 $ 7 while. (# result) < y do. a =. {: t n =. 1 + # t t =. t , a + n +. a d =. | -/ _2 {. t if. d > 1 do. result =. ~. result , d end. end. result ) This works perfectly, and it indeed generates the first n terms in the sequence. (By n terms, I mean the first n distinct primes.) Here is the output of rowland 20: 5 3 11 23 47 101 7 13 233 467 941 1889 3779 7559 15131 53 30323 60647 121403 242807 My question is, how can I write this in more idiomatic J? I don't have a clue, although I did write the following function to find the differences between each successive number in a list of numbers, which is one of the required steps. Here it is, although it too could probably be refactored by a more experienced J programmer than I: diffs =: monad : '}: (|@({.-2&{.) , $:@}.) ^: (1 < #) y'

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  • shell script passing subset of arguments

    - by arav
    From the wrapper shell scripts i am calling the Java program. I want the Unix shell script to pass all the arguments to java program except the EMAIL argument. HOW Can i remove the EMAIL argument and pass the rest of the arguments to the java program. EMAIL argument can come at any position. valArgs() { until [ $# -eq 0 ]; do case $1 in -EMAIL) MAILFLAG=Y shift break ;; esac done } main() { valArgs "$@" $JAVA_HOME/bin/java -d64 -jar WEB-INF/lib/test.jar "$@"

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