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  • Is SQL DATEDIFF(year, ..., ...) an Expensive Computation?

    - by rlb.usa
    I'm trying to optimize up some horrendously complicated SQL queries because it takes too long to finish. In my queries, I have dynamically created SQL statements with lots of the same functions, so I created a temporary table where each function is only called once instead of many, many times - this cut my execution time by 3/4. So my question is, can I expect to see much of a difference if say, 1,000 datediff computations are narrowed to 100?

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  • For what else I can use MySQL?

    - by ilhan
    I know how to store data in MySQL. Shortly, I know the basics: design, storing strings, integers, date. Is there something else that could be done/achieve with MySQL? Like some kind of functions, temprory bla blas? I don't know. (I know PHP)

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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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  • Javascript/jQuery HasLoaded or equivalent?

    - by maxp
    I know in jquery it is possible to call the javascript/jquery onload()/load() functions on, for example an image (<img>). However, if in jquery if i use .html(htmlString) to insert an image after the dom has loaded, how can i add a listener to handle the images onload event? Is there a property I can check to see various images and if they have loaded?

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  • class vs structure c#

    - by Enriquev
    I'm doing course 3354 (Implementing System Types and Interfaces in the .NET Framework 2.0) and it is said that for simple classes, with members variables and functions, it is better to use a struct than a class because of overhead. I have never heard of such a thing, what is the validity of this claim?

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  • On OSX, how do I gradient fill a path stroke?

    - by Emiel
    Using the plethora of drawing functions in Cocoa or Quartz it's rather easy to draw paths, and fill them using a gradient. I can't seem to find an acceptable way however, to 'stroke'-draw a path with a line width of a few pixels and fill this stroke using a gradient. How is this done?

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  • a class function with if(this==NULL) test got compiled?

    - by James
    I saw this code snippet during our lab and it actually compiles in MSVC2008 and G++. void LinkList< class T ::Insert(T n) { if (this == NULL) // some code here } As far as I know the this must not be null since you cannot call a class functions in c++ if it wasn't instantiated. Is this a valid code? if so what's the reason behind and where it can be useful?

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  • mvc external javascript referencing problem

    - by user281180
    I recently asked this question but to my suprise, it worked fine for some time and now has stopped again! I have a javascript in my script and I have added the link in my view as follows: It has certain functions which I can access once I have the script in my view. But when running I can see that the fucntions are not called instead i`m getting the error message Object expected at line 104. Why am I having this error and how can I solve it?

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  • Is there a substitute for blockproc in Matlab?

    - by SetchSen
    I've been using blockproc for processing images blockwise. Unfortunately, blockproc is part of the Image Processing Toolbox, which I don't have on my personal computer. Is there a combination of functions in base Matlab that can substitute for blockproc? My initial guess was to use im2col to transform each block into columns, and then arrayfun to process each column. Then I realized that im2col is also a part of the Image Processing Toolbox, so that doesn't solve my problem.

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  • Experiences with IKVM.NET

    - by Kottan
    Is IKVM.NET a good way to use Java Code or Java Libs in .NET applications ? Has anybody experiences with this tool ? Are there alternatives ? Are there possibilities to call Java functions / code in COM-based applications like Visual Basic 6 or Classical ASP ?

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  • How can I get/set default printers on a per-user basis in Terminal Services with C#?

    - by Charlie
    I want to be able to get and set the default printer for users within Windows Terminal Services, but I don't see any relevant functions. (The closest I've seen is RDS User Config, but it doesn't appear to do what I need.) It can be done by name or by ID (however necessary). For example, something like this pseudocode: For each user, u: p = u.GetDefaultPrinter() if p.name=='Inkjet' then: p2 = GetPrinterByName('Laser') u.SetDefaultPrinter( p2 )

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  • Does this incorporate JavaScript closures?

    - by alex
    In trying to learn JavaScript closures, I've confused myself a bit. From what I've gathered over the web, a closure is... Declaring a function within another function, and that inner function has access to its parent function's variables, even after that parent function has returned. Here is a small sample of script from a recent project. It allows text in a div to be scrolled up and down by buttons. var pageScroll = (function() { var $page, $next, $prev, canScroll = true, textHeight, scrollHeight; var init = function() { $page = $('#secondary-page'); // reset text $page.scrollTop(0); textHeight = $page.outerHeight(); scrollHeight = $page.attr('scrollHeight'); if (textHeight === scrollHeight) { // not enough text to scroll return false; }; $page.after('<div id="page-controls"><button id="page-prev">prev</button><button id="page-next">next</button></div>'); $next = $('#page-next'); $prev = $('#page-prev'); $prev.hide(); $next.click(scrollDown); $prev.click(scrollUp); }; var scrollDown = function() { if ( ! canScroll) return; canScroll = false; var scrollTop = $page.scrollTop(); $prev.fadeIn(500); if (scrollTop == textHeight) { // can we scroll any lower? $next.fadeOut(500); } $page.animate({ scrollTop: '+=' + textHeight + 'px'}, 500, function() { canScroll = true; }); }; var scrollUp = function() { $next.fadeIn(500); $prev.fadeOut(500); $page.animate({ scrollTop: 0}, 500); }; $(document).ready(init); }()); Does this example use closures? I know it has functions within functions, but is there a case where the outer variables being preserved is being used? Am I using them without knowing it? Thanks Update Would this make a closure if I placed this beneath the $(document).ready(init); statement? return { scrollDown: scrollDown }; Could it then be, if I wanted to make the text scroll down from anywhere else in JavaScript, I could do pageScroll.scrollDown(); I'm going to have a play around on http://www.jsbin.com and report back

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  • color objects in C or C ++ [closed]

    - by jazz
    Possible Duplicate: Colors in C language i copied a game from a book which name is paratrooper i ask this question again i also provide the code of the objects which i create there i want to change the color of these objects but i didn't understand how to do that so can any one plz help me how to do that.Listen guys they are not the standard functions but i use the graphics library for these functions and i can't find the function in the library file of graphics. i hope u understand know.this code will not run properly so plz tell me something about the function which color it i can't put the image other wize i show u the image it will make alot easieer #include "graphics.h" #include "stdio.h" #include "conio.h" #include "process.h" #include "alloc.h" #include "stdlib.h" #include "math.h" #include "dos.h" main() { int gm=CGAHI, gd=CGA, key=0, area; initgraph(&gd, &gm, "C:\\tc\\bgi"); helidraw(246,50,-1); getch(); return 0; } helidraw ( int x, int y, int d ) { int direction, i, j ; if ( d ) direction = -1 ; else direction = 1 ; i = 3 ; j = 8 ; line ( x - j - 8, y - i - 2, x + j + 8, y - i - 2 ) ; line ( x - j + 5, y - i - 1, x + j - 5, y - i - 1 ) ; line ( x - j, y - i, x + j, y - i ) ; for ( ; i > 0 ; i--, j += 2 ) { putpixel ( x - ( direction * j ), y - i, 1 ) ; line ( x + ( direction * j ), y - i, x + ( direction * ( j - 8 ) ), y - i ) ; } i = 0 ; j -= 2 ; line ( x - ( direction * j ), y - i, x - ( direction * ( j + 17 ) ), y - i ) ; line ( x - ( direction * j ), y - i + 1, x - ( direction * ( j + 7 ) ), y - i + 1 ) ; putpixel ( x - ( direction * ( j + 19 ) ), y - i - 1, 1 ) ; for ( ; i < 3 ; i++, j -= 2 ) { putpixel ( x - j, y + i, 1 ) ; putpixel ( x + j, y + i, 1 ) ; } line ( x - j, y + i, x + j, y + i ) ; putpixel ( x - j + 3, y + i + 1, 1 ) ; putpixel ( x + j - 3, y + i + 1, 1 ) ; line ( x - j - 10, y + i + 2, x + j + 10, y + i + 2 ) ; putpixel ( x + ( direction * ( j + 12 ) ), y + i + 1, 1 ) ; }

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  • wordpress my_deregister plugin from page

    - by musiC addicted
    i try to use the next code to load cforms II plugin only on my CONTACT PAGE (http://www.deliciousdays.com/cforms-plugin/) #/template/functions.php add_action( 'wp_print_scripts', ' ', 100 ); function my_deregister_javascript() { if ( !is_page('Contact') ) { wp_deregister_script( 'cforms' ); } } add_action( 'wp_print_styles', 'my_deregister_styles', 100 ); function my_deregister_styles() { if ( !is_page('contact') ) { wp_deregister_style( 'cforms' ); wp_deregister_style( 'style' ); } } but doesn't work the code worked for contact form 7 ( http://wordpress.org/extend/plugins/contact-form-7/)

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  • How can I perform a reverse string search in Excel without using VBA?

    - by e.James
    I have an Excel spreadsheet containing a list of strings. Each string is made up of several words, but the number of words in each string is different. Using built in Excel functions (no VBA), is there a way to isolate the last word in each string? Examples: Are you classified as human? - human? Negative, I am a meat popsicle - popsicle Aziz! Light! - Light!

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  • Where are the function literals in c++?

    - by academicRobot
    First of all, maybe literals is not the right term for this concept, but its the closest I could think of (not literals in the sense of functions as first class citizens). The idea is that when you make a conventional function call, it compiles to something like this: callq <immediate address> But if you make a function call using a function pointer, it compiles to something like this: mov <memory location>,%rax callq *%rax Which is all well and good. However, what if I'm writing a template library that requires a callback of some sort with a specified argument list and the user of the library is expected to know what function they want to call at compile time? Then I would like to write my template to accept a function literal as a template parameter. So, similar to template <int int_literal> struct my_template {...};` I'd like to write template <func_literal_t func_literal> struct my_template {...}; and have calls to func_literal within my_template compile to callq <immediate address>. Is there a facility in C++ for this, or a work around to achieve the same effect? If not, why not (e.g. some cataclysmic side effects)? How about C++0x or another language? Solutions that are not portable are fine. Solutions that include the use of member function pointers would be ideal. I'm not particularly interested in being told "You are a <socially unacceptable term for a person of low IQ>, just use function pointers/functors." This is a curiosity based question, and it seems that it might be useful in some (albeit limited) applications. It seems like this should be possible since function names are just placeholders for a (relative) memory address, so why not allow more liberal use (e.g. aliasing) of this placeholder. p.s. I use function pointers and functions objects all the the time and they are great. But this post got me thinking about the don't pay for what you don't use principle in relation to function calls, and it seems like forcing the use of function pointers or similar facility when the function is known at compile time is a violation of this principle, though a small one.

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  • Need to have testing server work with https: but don't have an SSL

    - by Cyrcle
    I'm working on an online store. I have it setup on my testing server. I'm having a problem where when it goes to the checkout functions it wants to start calling https pages. I don't have an SSL certificate for this server. Is there something I can do with Apache to get this to work? Mod_Rewrite perhaps? I've played a little with rewrites but haven't had any success.

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  • Delphi - Differences between CompareStr and CompareString

    - by Bourgui
    Hi all, I'm hoping someone can shed some light on this for me What are the differences, in Delphi 2009, between the CompareStr (defined in SysUtils) and CompareString (from Windows API) functions? Both let you specify the locale to be used, is the Windows one simply more "complete", due to the available comparison flags? Is one consequently faster than the other? Thanks!

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  • Is there something like clock() that works better for parallel code?

    - by Jared P
    So I know that clock() measures clock cycles, and thus isn't very good for measuring time, and I know there are functions like omp_get_wtime() for getting the wall time, but it is frustrating for me that the wall time varies so much, and was wondering if there was some way to measure distinct clock cycles (only one cycle even if more than one thread executed in it). It has to be something relatively simple/native. Thanks

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  • GL_MULTISAMPLING_ARB is not defined

    - by user146780
    I downloaded this: http://www.videotutorialsrock.com/opengl2.exe . I'm trying to follow a tutorial to setup multisampling but GL_MULTISAMPLING_ARB is not defined, and many necessary wgl functions do not seem to be defined. Wht's wrong exactly? Thanks

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