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Search found 271 results on 11 pages for 'jian zhang()'.

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  • push_back of STL list got bad performance?

    - by Leon Zhang
    I wrote a simple program to test STL list performance against a simple C list-like data structure. It shows bad performance at "push_back()" line. Any comments on it? $ ./test2 Build the type list : time consumed -> 0.311465 Iterate over all items: time consumed -> 0.00898 Build the simple C List: time consumed -> 0.020275 Iterate over all items: time consumed -> 0.008755 The source code is: #include <stdexcept> #include "high_resolution_timer.hpp" #include <list> #include <algorithm> #include <iostream> #define TESTNUM 1000000 /* The test struct */ struct MyType { int num; }; /* * C++ STL::list Test */ typedef struct MyType* mytype_t; void myfunction(mytype_t t) { } int test_stl_list() { std::list<mytype_t> mylist; util::high_resolution_timer t; /* * Build the type list */ t.restart(); for(int i = 0; i < TESTNUM; i++) { mytype_t aItem = (mytype_t) malloc(sizeof(struct MyType)); if(aItem == NULL) { printf("Error: while malloc\n"); return -1; } aItem->num = i; mylist.push_back(aItem); } std::cout << " Build the type list : time consumed -> " << t.elapsed() << std::endl; /* * Iterate over all item */ t.restart(); std::for_each(mylist.begin(), mylist.end(), myfunction); std::cout << " Iterate over all items: time consumed -> " << t.elapsed() << std::endl; return 0; } /* * a simple C list */ struct MyCList; struct MyCList{ struct MyType m; struct MyCList* p_next; }; int test_simple_c_list() { struct MyCList* p_list_head = NULL; util::high_resolution_timer t; /* * Build it */ t.restart(); struct MyCList* p_new_item = NULL; for(int i = 0; i < TESTNUM; i++) { p_new_item = (struct MyCList*) malloc(sizeof(struct MyCList)); if(p_new_item == NULL) { printf("ERROR : while malloc\n"); return -1; } p_new_item->m.num = i; p_new_item->p_next = p_list_head; p_list_head = p_new_item; } std::cout << " Build the simple C List: time consumed -> " << t.elapsed() << std::endl; /* * Iterate all items */ t.restart(); p_new_item = p_list_head; while(p_new_item->p_next != NULL) { p_new_item = p_new_item->p_next; } std::cout << " Iterate over all items: time consumed -> " << t.elapsed() << std::endl; return 0; } int main(int argc, char** argv) { if(test_stl_list() != 0) { printf("ERROR: error at testcase1\n"); return -1; } if(test_simple_c_list() != 0) { printf("ERROR: error at testcase2\n"); return -1; } return 0; }

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  • why can't I comment lines in visual mode

    - by Haiyuan Zhang
    I want to comment several lines in my .vimrc, the usual way I do it is :x,ys/^/"/ and x stands for the start line number and y stands for the line number of the last line. I read some post which said in visual mode this task can be done by the following step: 1 Select your lines with VISUAL BLOCK 2 press I to insert before all highlighted lines. 3 type your comment charact , in this case should be " 4 then ESC I fllowed the above steps and met met problems in step 2 . the thing is when I select the lines in Visual mode and press I , vim ( I use version7.2) go back to insert mode and the cursor back to the start of the first line. so if you continue to do the step 3 and step 4, you end up in just inserting " at the start the first line , far from what I want to achieve. so could you point out what's wrong with the recipe ? thanks in advance

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  • how to manage vim plugin

    - by Haiyuan Zhang
    I want to know how do you manage your vim plugins. As it is, One of the biggest fun of using is that one can easily try many interesing new plugins, just download it and unzip it in under ~/.vim. But if you try too often and try too much, you might get trouble as confilct of key mapping , in compatitble script version, dpendency between different plugin ..... Then you want to remove some plugin ,kind of like rollback your vim to a sound condition. But, the rollback could be very painful . cus for some "giant" plugin, like perl-support ( it's great plugin, anyway), will consist of many vim scripts which spread in different dirctories. To remove single one giant plugin will be anoying, not too mention if you remvoe many plugin at one time. In a word , I'm looking for good practice for managing vim plugins.

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  • how to bind a link local address to an ipv6 socket

    - by Haiyuan Zhang
    This thread can be treated as a sister thread of this. It's will be very tedious that when you want to bind a link local adress to a ipv6 socket you need to the set sin6_scope_id field of sockaddr_in6 struct as well. I'm wondering if someone can provide a good practise like solution here for me or anyone who interested in this topic to learn from.

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  • How to update the original InfoPath form from within Workflow?

    - by Allen.Zhang
    Hi All, I have created an InfoPath form (e.g. Form_ExpenseReport) for collect data from end users, and a number of task forms (also InfoPath form, e.g. TaskForm_1, TaskForm_2) for my state machine workflow use. The users want to see all the comments of Task forms (TaskForm_1 & TaskForm_2) in the original IP form (Form_ExpenseReport). How can I update the first form from within workflow? Can anybody give me some tips? My environment: MOSS 2007 Enterprise license VS 2008

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  • can't create socket using IO::Socket

    - by Haiyuan Zhang
    when I run the following code, the execution is just hanging there, No response at all. does any of you can tell me what's wrong with the sample code? use strict; use warnings; use IO::Select; use IO::Socket; my $s = new IO::Socket ( LocalPort => 8889, Proto => 'tcp', Listen => 16, Reuse => 1 ); die "could not create socket $!\n" unless $s;

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  • how to handle "unknown error" in perl module compilation

    - by Haiyuan Zhang
    when I try to use a "third part module" in my perl script, I got some error message like "unknown error, compilation failed in require at ... line xxx" nothing else and the line mentioned in the error message is exact the same line I "use the module"... my question is: are there any good practice to handle this situation? like a list to check or something else. thanks in advance.

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  • Is it possible ot mix named pipe with select in perl

    - by Haiyuan Zhang
    I need to write a daemon that supposed to have one TCP socket and one named pipe. Usually if I need to implement a multi IO server with "pure" sockets, the select based multi-IO model is always the one I will choose. so does anyone of you have ever used named pipe in select or you can just tell me it is impossible. thanks in advance.

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  • Initialize a static member ( an array) in C++

    - by Jimmy zhang
    I intended to create a class which only have static members and static functions. One of the member variable is an array. Would it be possible to initialize it without using constructors? I am having lots of linking errors right now... Class A{ public: static char a[128]; static void do_something(); } How would you initialize a[128]? Why can't I initialize a[128] by directly specifying its value like in C? a[128={1,2,3,...};

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  • approximating log10[x^k0 + k1]

    - by Yale Zhang
    Greetings. I'm trying to approximate the function Log10[x^k0 + k1], where .21 < k0 < 21, 0 < k1 < ~2000, and x is integer < 2^14. k0 & k1 are constant. For practical purposes, you can assume k0 = 2.12, k1 = 2660. The desired accuracy is 5*10^-4 relative error. This function is virtually identical to Log[x], except near 0, where it differs a lot. I already have came up with a SIMD implementation that is ~1.15x faster than a simple lookup table, but would like to improve it if possible, which I think is very hard due to lack of efficient instructions. My SIMD implementation uses 16bit fixed point arithmetic to evaluate a 3rd degree polynomial (I use least squares fit). The polynomial uses different coefficients for different input ranges. There are 8 ranges, and range i spans (64)2^i to (64)2^(i + 1). The rational behind this is the derivatives of Log[x] drop rapidly with x, meaning a polynomial will fit it more accurately since polynomials are an exact fit for functions that have a derivative of 0 beyond a certain order. SIMD table lookups are done very efficiently with a single _mm_shuffle_epi8(). I use SSE's float to int conversion to get the exponent and significand used for the fixed point approximation. I also software pipelined the loop to get ~1.25x speedup, so further code optimizations are probably unlikely. What I'm asking is if there's a more efficient approximation at a higher level? For example: Can this function be decomposed into functions with a limited domain like log2((2^x) * significand) = x + log2(significand) hence eliminating the need to deal with different ranges (table lookups). The main problem I think is adding the k1 term kills all those nice log properties that we know and love, making it not possible. Or is it? Iterative method? don't think so because the Newton method for log[x] is already a complicated expression Exploiting locality of neighboring pixels? - if the range of the 8 inputs fall in the same approximation range, then I can look up a single coefficient, instead of looking up separate coefficients for each element. Thus, I can use this as a fast common case, and use a slower, general code path when it isn't. But for my data, the range needs to be ~2000 before this property hold 70% of the time, which doesn't seem to make this method competitive. Please, give me some opinion, especially if you're an applied mathematician, even if you say it can't be done. Thanks.

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  • how to adjust the default width of taglist window in vim

    - by Haiyuan Zhang
    The default width of taglist window is too narrow for me and sometimes I can't see the whole function name in the window so I'd like to adujct the width of the window. I know use ctr-w > or ctr-w < I can adjust the window manually , but really want to change the default value of the taglisst window. so how I can actually do it ? thansk in advance.

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  • [Three20] How to adjust width of TTStyledTextLabel ?

    - by Chi Zhang
    Hi I am implementing an IM app on iOS. I found that three20 library has a TTStyledTextLabel which provides cool features like showing images and url links. However I want to embed the TTStyledTextLabel in a message bubble (just like the sms app shipped with iphone does), where I need the label to adjust its size according to the text length. I found that TTStyledTextLabel can adjust its height according to its width, but I don't know how to make it shrink horizontally when the text is very short and can't fill up a whole line. Any suggestions?

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  • how to store a file handle in perl class

    - by Haiyuan Zhang
    please look at the following code first. #! /usr/bin/perl package foo; sub new { my $pkg = shift; my $self = {}; my $self->{_fd} = undef; bless $self, $pkg; return $self; } sub Setfd { my $self = shift; my $fd = shift; $self_->{_fd} = $fd; } sub write { my $self = shift; print $self->{_fd} "hello word"; } my $foo = new foo; My intention is to store a file handle within a class using hash. the file handle is undefined at first, but can be initilized afterwards by calling Setfd function. then write can be called to actually write string "hello word" to a file indicated by the file handle, supposed that the file handle is the result of a success "write" open. but, perl compiler just complains that there are syntax error in the "print" line. can anyone of you tells me what's wrong here? thanks in advance.

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  • why can't i bind ipv6 socket to a linklocal address

    - by Haiyuan Zhang
    #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <netdb.h> #include <stdio.h> void error(char *msg) { perror(msg); exit(0); } int main(int argc, char *argv[]) { int sock, length, fromlen, n; struct sockaddr_in6 server; struct sockaddr_in6 from; int portNr = 5555; char buf[1024]; length = sizeof (struct sockaddr_in6); sock=socket(AF_INET6, SOCK_DGRAM, 0); if (sock < 0) error("Opening socket"); bzero((char *)&server, length); server.sin6_family=AF_INET6; server.sin6_addr=in6addr_any; server.sin6_port=htons(portNr); inet_pton( AF_INET6, "fe80::21f:29ff:feed:2f7e", (void *)&server.sin6_addr.s6_addr); //inet_pton( AF_INET6, "::1", (void *)&server.sin6_addr.s6_addr); if (bind(sock,(struct sockaddr *)&server,length)<0) error("binding"); fromlen = sizeof(struct sockaddr_in6); while (1) { n = recvfrom(sock,buf,1024,0,(struct sockaddr *)&from,&fromlen); if (n < 0) error("recvfrom"); write(1,"Received a datagram: ",21); write(1,buf,n); n = sendto(sock,"Got your message\n",17, 0,(struct sockaddr *)&from,fromlen); if (n < 0) error("sendto"); } } when I compile and run the above code I got : binding: Invalid argument and if change to bind the ::1 and leave other thing unchanged in the source code, the code works! so could you tell me what's wrong with my code ? thanks in advance.

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  • how to find files in a given branch

    - by Haiyuan Zhang
    I noticed that when doing code view, people here in my company usually just give the branch in which his work is done, and nothing else. So I guess there must be a easy way to find out all the files that has a version in the given branch which is the same thing to find all the files that has been the changed. Yes, I don't know the expected "easy way" to find files in certain branch, so need your help and thanks in advance.

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  • Is it possible to mix a named pipe with select in perl?

    - by Haiyuan Zhang
    I need to write a daemon that supposed to have one TCP socket and one named pipe. Usually if I need to implement a multi IO server with "pure" sockets, the select based multi-IO model is always the one I will choose. so does anyone of you have ever used named pipe in select or you can just tell me it is impossible. thanks in advance.

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  • Return lines in input code causing gaps/whitespace between elements in output?

    - by Jenny Zhang
    I am trying to put images next to each other on a webpage. Here is my HTML: <img class="pt" src="Yellow Tulip.jpg" title="Yellow Tulip" alt="Yellow Tulip" /> <img class="pt" src="Pink Tulip.jpg" title="Pink Tulip" alt="Pink Tulip" /> <img class="pt" src="Purple Tulip.jpg" title="Purple Tulip" alt="Purple Tulip" /> However, on my webpage, this shows a gap between each image. I've noticed that once I remove the return line that makes the elements separate and readable and instead just put all the elements on one line, the gaps go away. <img class="pt" src="Yellow Tulip.jpg" title="Yellow Tulip" alt="Yellow Tulip" /><img class="pt" src="Pink Tulip.jpg" title="Pink Tulip" alt="Pink Tulip" /><img class="pt" src="Purple Tulip.jpg" title="Purple Tulip" alt="Purple Tulip" /> Is there anyway I can achieve the output of the latter but still have the code/input look like the former? I really like the readability that the return lines (enter spaces) bring to the code, but I don't want the whitespace it creates on the actual page. If someone could explain why this is and/or how to fix it, I'd be really grateful! :)

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  • why does perl allow mutually "use" relationship between modules

    - by Haiyuan Zhang
    let's say there two modules mutualy use each othe as: package a; use b; sub p {} 1; package b; use a; 1; I think symatically it's wrong to wrote code like the above code, cus the two modules will endlessly copy each other's code to themselves...but I can successfully run the following code, which makes me very surprised. so could any of you explain all of this to me? #! /usr/bin/perl use a; a->p();

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  • Manage bad_alloc exception in C++ construtor

    - by Jimmy zhang
    I have Java experience and recently am doing some C++ coding. My question is that if I have class A, in which I have to instantiate class B and class C as two of the member variables of A. If in the constructor of A, should I assume that allocations of class B and C never fail, and handle the bad allocation exception in the destructor of A? If I don't make that assumption, meaning that I add some try catch block to catch bad_alloc of class B and class C, then if the allocation exception occurs, should I do clean up in the constructor of A? What are the recommended practices? If "new" generates a bad allocation, what value does the pointer carry?

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