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  • Why is my multithreaded Java program not maxing out all my cores on my machine?

    - by James B
    Hi, I have a program that starts up and creates an in-memory data model and then creates a (command-line-specified) number of threads to run several string checking algorithms against an input set and that data model. The work is divided amongst the threads along the input set of strings, and then each thread iterates the same in-memory data model instance (which is never updated again, so there are no synchronization issues). I'm running this on a Windows 2003 64-bit server with 2 quadcore processors, and from looking at Windows task Manager they aren't being maxed-out, (nor are they looking like they are being particularly taxed) when I run with 10 threads. Is this normal behaviour? It appears that 7 threads all complete a similar amount of work in a similar amount of time, so would you recommend running with 7 threads instead? Should I run it with more threads?...Although I assume this could be detrimental as the JVM will do more context switching between the threads. Alternatively, should I run it with fewer threads? Alternatively, what would be the best tool I could use to measure this?...Would a profiling tool help me out here - indeed, is one of the several profilers better at detecting bottlenecks (assuming I have one here) than the rest? Note, the server is also running SQL Server 2005 (this may or may not be relevant), but nothing much is happening on that database when I am running my program. Note also, the threads are only doing string matching, they aren't doing any I/O or database work or anything else they may need to wait on. Thanks in advance, -James

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  • how to manage a "resource" array efficiently

    - by Haiyuan Zhang
    The senario of my question is that one need to use a fixed size of array to keep track of certain number of "objects" . The object here can be as simply as a integer or as complex as very fancy data structure. And "keep track" here means to allocate one object when other part of the app need one instance of object and recyle it for future allocation when one instance of the object is returned .Finally ,let me use c++ to put my problme in a more descriptive way . #define MAX 65535 /* 65535 just indicate that many items should be handled . performance demanding! */ typedef struct { int item ; }Item_t; Item_t items[MAX] ; class itemManager { private : /* up to you.... */ public : int get() ; /* get one index to a free Item_t in items */ bool put(int index) ; /* recyle one Item_t indicate by one index in items */ } how will you implement the two public functions of itemManager ? it's up to you to add any private member .

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  • Javascript/PHP and timezones

    - by James
    Hi, I'd like to be able to guess the user's timezone offset and whether or not daylight savings is being applied. Currently, the most definitive code that I've found for this is here: http://www.michaelapproved.com/articles/daylight-saving-time-dst-detect/ So this gives me the offset along with the DST indicator. Now, I want to use these in my PHP scripts in order to ouput the local date/time for the user....but what's best for this? I figure I have 2 options: a) Pick a random timezone which has the same offset and DST setting from the output of timezone_abbreviations_list(). Then call date_timezone_set() with this in order to apply the correct treatment to the time. b) Continue treating the date as UTC but just do some timestamp addition to add the appropriate number of hours on. My feeling is that option B is the best way. The reason for this is that with A, I could be using a timezone which although correct in terms of offset/dst, may have some obscur rules in place behind the scene that could give surprising results (I don't know of any but nonetheless I don't think I can rule it out). I'd then re-check the timezone using Javascript at the start of each session in order to capture when either the user's timezone changes (very unlikely) or they pass in to the DST period. Sorry for the brain dump - I'm really just after some sort of reassurance that the approaches above are valid. Thanks, James.

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  • Disable chaching in JPA (eclipselink)

    - by James
    Hi, I want to use JPA (eclipselink) to get data from my database. The database is changed by a number of other sources and I therefore want to go back to the database for every find I execute. I have read a number of posts on disabling the cache but this does not seem to be working. Any ideas? I am trying to execute the following code: EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("default"); EntityManager em = entityManagerFactory.createEntityManager(); MyLocation one = em.createNamedQuery("MyLocation.findMyLoc").getResultList().get(0); MyLocation two = em.createNamedQuery("MyLocation.findMyLoc").getResultList().get(0); System.out.println(one==two); one==two is true while I want it to be false. I have tried adding each/all the following to my persistence.xml <property name="eclipselink.cache.shared.default" value="false"/> <property name="eclipselink.cache.size.default" value="0"/> <property name="eclipselink.cache.type.default" value="None"/> I have also tried adding the @Cache annotation to the Entity itself: @Cache( type=CacheType.NONE, // Cache nothing expiry=0, alwaysRefresh=true ) Am I misunderstanding something? Thank you, James

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  • Data Mappers, Models and Images

    - by James
    Hi, I've seen and read plenty of blog posts and forum topics talking about and giving examples of Data Mapper / Model implementations in PHP, but I've not seen any that also deal with saving files/images. I'm currently working on a Zend Framework based project and I'm doing some image manipulation in the model (which is being passed a file path), and then I'm leaving it to the mapper to save that file to the appropriate location - is this common practise? But then, how do you deal with creating say 3 different size images from the one passed in? At the moment I have a "setImage($path_to_tmp_name)" which checks the image type, resizes and then saves back to the original filename. A call to "getImagePath()" then returns the current file path which the data mapper can use and then change with a call to "setImagePath($path)" once it's saved it to the appropriate location, say "/content/my_images". Does this sound practical to you? Also, how would you deal with getting the URL to that image? Do you see that as being something that the model should be providing? It seems to me like that model should worry about where the images are being stored or ultimately how they're accessed through a browser and so I'm inclined to put that in the ini file and just pass the URL prefix to the view through the controller. Does that sound reasonable? I'm using GD for image manipulation - not that that's of any relevance. UPDATE: I've been wondering if the image resizing should be done in the model at all. The model could require that it's provided a "main" image and a "thumb" image, both of certain dimensions. I've thought about creating a "getImageSpecs()" function in the model that would return something that defines the required sizes, then a separate image manipulation class could carry out the resizing and (perhaps in the controller?) and just pass the final paths in to the model using something like "setImagePaths($images)". Any thoughts much appreciated :) James.

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  • How to drag item out from Iframe and drop onto parent

    - by ethan.zhang
    Hi, I have a folder tree view on the left page which was in a tag, left page was the iframe container which contain the file list, when I want to drag the files out from the iframe, I got a headache. no matter the containment option was set to 'parent' or 'window', I just can't drag out elements in the iframe container can any one help on this?

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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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  • Stopping and Play button for Audio (Android)

    - by James Rattray
    I have this problem, I have some audio I wish to play... And I have two buttons for it, 'Play' and 'Stop'... Problem is, after I press the stop button, and then press the Play button, nothing happens. -The stop button stops the song, but I want the Play button to play the song again (from the start) Here is my code: final MediaPlayer mp = MediaPlayer.create(this, R.raw.megadeth); And then the two public onclicks: (For playing...) button.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { // Perform action on click button.setText("Playing!"); try { mp.prepare(); } catch (IllegalStateException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } mp.start(); // } }); And for stopping the track... final Button button2 = (Button) findViewById(R.id.cancel); button2.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { mp.stop(); mp.reset(); } }); Can anyone see the problem with this? If so could you please fix it... (For suggest) Thanks alot... James

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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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  • Returning a variable in a public void...

    - by James Rattray
    Hello, I'm abit new to programming Android App's, however I have come across a problem, I can't find a way to make global variables -unlike other coding like php or VB.NET, are global variables possible? If not can someone find a way (and if possible implement the way into the code I will provide below) to get a value from the variable 'songtoplay' so I can use in another Public Void... Here is the code: final Spinner hubSpinner = (Spinner) findViewById(R.id.myspinner); ArrayAdapter adapter = ArrayAdapter.createFromResource( this, R.array.colours, android.R.layout.simple_spinner_item); adapter .setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); hubSpinner.setAdapter(adapter); // hubSpinner.setOnItemSelectedListener(new OnItemSelectedListener() { public void onItemSelected(AdapterView<?> parentView, View selectedItemView, int position, long id) { //code Object ttestt = hubSpinner.getSelectedItem(); final String test2 = ttestt.toString(); Toast message1 = Toast.makeText(Textbox.this, test2, Toast.LENGTH_LONG); message1.show(); String songtoplay = test2; // Need songtoplay to be available in another 'Public Void' } public void onNothingSelected(AdapterView<?> parentView) { //Code } }); Basically, it gets the value from the Spinner 'hubSpinner' and displays it in a Toast. I then want it to return a value for string variable 'songtoplay' -or find a way to make it global or useable in another Public Void, (Which is will a button, -loading the song to be played) Please help me, Thanks alot. James

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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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  • When to use certain optimizations such as -fwhole-program and -fprofile-generate with several shared libraries

    - by James
    Probably a simple answer; I get quite confused with the language used in the GCC documentation for some of these flags! Anyway, I have three libraries and a programme which uses all these three. I compile each of my libraries seperately with individual (potentially) different sets of warning flags. However, I compile all three libraries with the same set of optimisation flags. I then compile my main programme linking in these three libraries with its own set of warning flags and the same optimisation flags used during the libraries' compilation. 1) Do I have to compile the libraries with optimisation flags present or can I just use these flags when compiling the final programme and linking to the libraries? If the latter, will it then optimise all or just some (presumably that which is called) of the code in these libraries? 2) I would like to use -fwhole-program -flto -fuse-linker-plugin and the linker plugin gold. At which stage do I compile with these on ... just the final compilation or do these flags need to be present during the compilation of the libraries? 3) Pretty much the same as 2) however with, -fprofile-generate -fprofile-arcs and -fprofile-use. I understand one first runs a programme with generate, and then with use. However, do I have to compile each of the libraries with generate/use etc. or just the final programme? And if it is just the last programme, when I then compeil with -fprofile-use will it also optimise the libraries functionality? Many thanks, James

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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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