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  • What's the most trivial function that would benfit from being computed on a GPU?

    - by hanDerPeder
    Hi. I'm just starting out learning OpenCL. I'm trying to get a feel for what performance gains to expect when moving functions/algorithms to the GPU. The most basic kernel given in most tutorials is a kernel that takes two arrays of numbers and sums the value at the corresponding indexes and adds them to a third array, like so: __kernel void add(__global float *a, __global float *b, __global float *answer) { int gid = get_global_id(0); answer[gid] = a[gid] + b[gid]; } __kernel void sub(__global float* n, __global float* answer) { int gid = get_global_id(0); answer[gid] = n[gid] - 2; } __kernel void ranksort(__global const float *a, __global float *answer) { int gid = get_global_id(0); int gSize = get_global_size(0); int x = 0; for(int i = 0; i < gSize; i++){ if(a[gid] > a[i]) x++; } answer[x] = a[gid]; } I am assuming that you could never justify computing this on the GPU, the memory transfer would out weight the time it would take computing this on the CPU by magnitudes (I might be wrong about this, hence this question). What I am wondering is what would be the most trivial example where you would expect significant speedup when using a OpenCL kernel instead of the CPU?

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  • How can c let a function declaration with any parameter type ?

    - by kamil çakir
    I forgot to write void parameter but it works the i put void it gives error it lets this: print(int size,int table[size][size]){ int i,j; printf("-------TABLE-------\n"); for(i = 0;i it says"previos implicit declaration was here " (means the call in main) void print(int size,int table[size][size]){ int i,j; printf("-------TABLE-------\n"); for(i = 0;i

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  • Weirdness using jquery's .html() function to set <a></a> with a special character &#10003; (checkmar

    - by Sam
    Hey all, I'm trying to have the following tag toggle between a "-" and the checkmark character (✓) <a id='p_4' class='fancy_button orange bls_button' href='#'>-</a> And here's the jquery code: if (button.text() == '-') { button.html('&#10003'); } This works in FF3.6 and IE8, but not in WebKit (Chrome or iPhone safari). Is there something I'm doing wrong, or does webkit just not like .html("✓") Thanks, Sam

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  • How to find the jmp address during a x86 function call?

    - by Bruce
    Suppose we have a call foo statement. So when the assembler encounters a call statement it breaks it down into - push ip + 6 jmp <addr of foo> I have the return address in a register ebx. Now I want to find out the "addr of foo". How do I do it? I want to confirm that the push statement is present before the jmp. Will the memory map look something like this? ------- push (what will be the value stored in this byte?? opcode ??) ------- jmp (what will be the value stored in this byte?? opcode ??) ------- jmp byte 1 ------- jmp byte 2 ------- jmp byte 3 ------- jmp byte 4 ------- return address stored in ebx ------- What are the opcodes for push and jmp?

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  • How to get an array to check in the in_array function? See description Below...

    - by Parth
    I am fetching the data using mysql_fetch_array like : while($row = mysql_fetch_array($select)) { $tables[] =$row; } Now i need this $tables array as one dimensional array only, so that i can use it in if(in_array($val['table_name'],$tables)) { //Some Code } to check for whether the $val['table_name'] is in the $tables or not.. As for now I am getting $tables array as Array ( [0] => Array ( [TABLE_NAME] => jos_audittrail ) [1] => Array ( [TABLE_NAME] => jos_banner ) [2] => Array ( [TABLE_NAME] => jos_bannerclient ) .. .. .. .. } But I need the $tables is form of.. Array ( [0] => jos_audittrail [TABLE_NAME] => jos_audittrail [1] => jos_banner [TABLE_NAME] => jos_banner [2] => jos_bannerclient [TABLE_NAME] => jos_bannerclient .. .. .. } How can i get the above array after applying "while loop" to "$row"?

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  • A quick way to map unordered list of longs to buffer location ?

    - by alhazen
    I have a large number of points (indexed by long) that are processed by multiple threads and I'm using a buffer to hold the output results in order. As the number of points processed is huge, what would be an efficient way to map the indexes of the points to the corresponding ordered position in the buffer ? Example: long bufferIndex bufferIndex index (if BufferSize = 2) (if BufferSize = 4) ---------------------------------------------- 2938 0 0 2939 1 1 2941 1 3 2940 0 2 Thanks.

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  • Why some pictures are are crooked aftes using my function?

    - by Miko Kronn
    struct BitmapDataAccessor { private readonly byte[] data; private readonly int[] rowStarts; public readonly int Height; public readonly int Width; public BitmapDataAccessor(byte[] data, int width, int height) { this.data = data; this.Height = height; this.Width = width; rowStarts = new int[height]; for (int y = 0; y < Height; y++) rowStarts[y] = y * width; } public byte this[int x, int y, int color] // Maybe use an enum with Red = 0, Green = 1, and Blue = 2 members? { get { return data[(rowStarts[y] + x) * 3 + color]; } set { data[(rowStarts[y] + x) * 3 + color] = value; } } public byte[] Data { get { return data; } } } public static byte[, ,] Bitmap2Byte(Bitmap obraz) { int h = obraz.Height; int w = obraz.Width; byte[, ,] wynik = new byte[w, h, 3]; BitmapData bd = obraz.LockBits(new Rectangle(0, 0, w, h), ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb); int bytes = Math.Abs(bd.Stride) * h; byte[] rgbValues = new byte[bytes]; IntPtr ptr = bd.Scan0; System.Runtime.InteropServices.Marshal.Copy(ptr, rgbValues, 0, bytes); BitmapDataAccessor bda = new BitmapDataAccessor(rgbValues, w, h); for (int i = 0; i < h; i++) { for (int j = 0; j < w; j++) { wynik[j, i, 0] = bda[j, i, 2]; wynik[j, i, 1] = bda[j, i, 1]; wynik[j, i, 2] = bda[j, i, 0]; } } obraz.UnlockBits(bd); return wynik; } public static Bitmap Byte2Bitmap(byte[, ,] tablica) { if (tablica.GetLength(2) != 3) { throw new NieprawidlowyWymiarTablicyException(); } int w = tablica.GetLength(0); int h = tablica.GetLength(1); Bitmap obraz = new Bitmap(w, h, PixelFormat.Format24bppRgb); for (int i = 0; i < w; i++) { for (int j = 0; j < h; j++) { Color kol = Color.FromArgb(tablica[i, j, 0], tablica[i, j, 1], tablica[i, j, 2]); obraz.SetPixel(i, j, kol); } } return obraz; } Now, if I do: private void btnLoad_Click(object sender, EventArgs e) { if (dgOpenFile.ShowDialog() == DialogResult.OK) { try { Bitmap img = new Bitmap(dgOpenFile.FileName); byte[, ,] tab = Grafika.Bitmap2Byte(img); picture.Image = Grafika.Byte2Bitmap(tab); picture.Size = img.Size; } catch (Exception ex) { MessageBox.Show(ex.Message); } } } Most of pictures are handled correctly butsome not. Example of picture that doesn't work: It produce following result (this is only fragment of picture) : Why is that?

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  • Function templates for arbitrary STL containers containing arbitrary types.

    - by Chad Brewbaker
    I have an arbitrary STL container C, which contains elements of an arbitrary type T. I want to create an std::vector that has a copy of all the elements. What is the cleanest way to do this? template <typename C> void myfunction(C container){ /*Derive the type T of elements within the container*/ std::vector<T> mystack; /* Iterate over container and push_back() the elements into mystack*/ }

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  • Cuboid inside generic polyhedron

    - by DOFHandler
    I am searching for an efficient algorithm to find if a cuboid is completely inside or completely outside or (not-inside and not-outside) a generic (concave or convex) polyhedron. The polyhedron is defined by a list of 3D points and a list of facets. Each facet is defined by the subset of the contour points ordinated such as the right-hand normal points outward the solid. Any suggestion? Thank you

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  • Variable scope problem in JavaScript

    - by dfjhdfjhdf
    I declare a variable with the var word inside a function that handles Ajax requests, then later on in the function I have another function that should change the value of the variable but - my problem - it fails. How to settle the problem down? Here's similiar code I use: function sendRuest(someargums) { /* some code */ var the_variable; /* some code */ //here's that other function request.onreadystatechange = function() { if (request.readyState == 4) { switch (request.status) { case 200: //here the variable should be changed the_variable = request.responseXML; /* a lot of code */ //somewhere here the function closes } return the_variable; } var data = sendRequest(someargums); //and trying to read the data I get the undefined value

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  • Speed comparison - Template specialization vs. Virtual Function vs. If-Statement

    - by Person
    Just to get it out of the way... Premature optimization is the root of all evil Make use of OOP etc. I understand. Just looking for some advice regarding the speed of certain operations that I can store in my grey matter for future reference. Say you have an Animation class. An animation can be looped (plays over and over) or not looped (plays once), it may have unique frame times or not, etc. Let's say there are 3 of these "either or" attributes. Note that any method of the Animation class will at most check for one of these (i.e. this isn't a case of a giant branch of if-elseif). Here are some options. 1) Give it boolean members for the attributes given above, and use an if statement to check against them when playing the animation to perform the appropriate action. Problem: Conditional checked every single time the animation is played. 2) Make a base animation class, and derive other animations classes such as LoopedAnimation and AnimationUniqueFrames, etc. Problem: Vtable check upon every call to play the animation given that you have something like a vector<Animation>. Also, making a separate class for all of the possible combinations seems code bloaty. 3) Use template specialization, and specialize those functions that depend on those attributes. Like template<bool looped, bool uniqueFrameTimes> class Animation. Problem: The problem with this is that you couldn't just have a vector<Animation> for something's animations. Could also be bloaty. I'm wondering what kind of speed each of these options offer? I'm particularly interested in the 1st and 2nd option because the 3rd doesn't allow one to iterate through a general container of Animations. In short, what is faster - a vtable fetch or a conditional?

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  • Can I set a timeout for a InputStream's read() function?

    - by Zombies
    I have a DataInputStream that I obtained from a Socket. Is there any way I can set a timeout for dis.read(...)? Currently I spawn a new thread to do the read. While the parent thread does a thread.join(timeout) to wait before interrupting it. I am aware of nio, but I don't think I want to refactor that much at this point. Thanks.

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  • C++ vector<T>::iterator operator +

    - by Tom
    Hi, Im holding an iterator that points to an element of a vector, and I would like to compare it to the next element of the vector. Here is what I have Class Point{ public: float x,y; } //Somewhere in my code I do this vector<Point> points = line.getPoints(); foo (points.begin(),points.end()); where foo is: void foo (Vector<Point>::iterator begin,Vector<Point>::iterator end) { std::Vector<Point>::iterator current = begin; for(;current!=end-1;++current) { std::Vector<Point>::iterator next = current + 1; //Compare between current and next. } } I thought that this would work, but current + 1 is not giving me the next element of the vector. I though operator+ was the way to go, but doesnt seem so. Is there a workaround on this? THanks

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  • How can I take any function as input for my Scala wrapper method?

    - by pr1001
    Let's say I want to make a little wrapper along the lines of: def wrapper(f: (Any) => Any): Any = { println("Executing now") val res = f println("Execution finished") res } wrapper { println("2") } Does this make sense? My wrapper method is obviously wrong, but I think the spirit of what I want to do is possible. Am I right in thinking so? If so, what's the solution? Thanks!

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  • How do I bind a key to "the function represented by the following key sequence"?

    - by katrielalex
    I'm just starting to learn emacs (woohoo!) and I've been mucking around in my .emacs quite happily. Unfortunately, I don't know Lisp yet, so I'm having issues with the basics. I've already remapped a few keys until I fix my muscle memory: (global-set-key (kbd "<f9>") 'recompile) That's fine. But how can I tell a key to 'simulate pressing several keys'? For instance, I don't know, make <f1> do the same as C-u 2 C-x } (widen buffer by two chars). One way is to look up that C-x } calls shrink-window-horizontally, and do some sort of lambda thing. This is of course the neat and elegant way (how do you do this?). But surely there's a way to define <f1> to send the keystrokes C-u 2 C-x }?

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  • How to decide if a parameter is the click event

    - by sameold
    I have a function which can be called by either a click event or directly. When I call it directly, I need pass it a data parameter, so I've defined the function to accept a parameter to account for the direct call with the parameter. function myFunc(param){ } Within the function, I need to differentiate whether the function was called directly or from the click event, so what I thought I could simply check if param is set. If it's set, then the function is called directly. If it's not set, then it's called from the click event. The problem is that a click event by default passes an event object. So even when the function is called by the click event, param won't be null. So is there a way to check whether the param passed is the click event?

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  • Call methods on native Javascript types without wrapping with ()

    - by Anurag
    In Javascript, we can call methods on string literals directly without enclosing it within round brackets. But not for other types such as numbers, or functions. It is a syntax error, but is there a reason as to why the Javascript lexer needs these other types to be enclosed in round brackets? For example, if we extend Number, String, and Function with an alert method and try calling this method on the literals, it's a SyntaxError for Number and Function, while it works for a String. function alertValue() { alert(this); } Number.prototype.alert = alertValue; String.prototype.alert = alertValue; Function.prototype.alert = alertValue; We can call alert directly on a string object: "someStringLiteral".alert() // alerts someStringLiteral but it's a SyntaxError on numbers, and functions. 7.alert(); function() {}.alert(); To work with these types, we have to enclose it within brackets: (7).alert(); // alerts "7" (function() {}).alert(); // alerts "function() {}"

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  • In R, how to get powers of ten in bold font in a plot label?

    - by wfoolhill
    I want to have "10^4 points" in bold as my x-axis label. I know how to make a simple label in bold: plot(1:10, xlab="") mtext(text="10 points", side=1, font=2, line=3) Thanks to this answer, I know how to make a label with a power of ten but nothing is in bold: mtext(text=expression(paste(10^4, " points")), side=1, font=2, line=3) Thanks to this answer, I also know how to make a label with a Greek letter in bold: mtext(text=expression(bold(paste(beta, "=", 10^1, " points"))), side=1, line=3) But still the power of ten is not in bold! It doesn't work either with bquote: mtext(text=bquote(bold(10^1~points)), side=1, line=3) Any idea? Here are some details about my system. Let me know if you need anything else. > sessionInfo() R version 2.15.0 (2012-03-30) Platform: x86_64-redhat-linux-gnu (64-bit) locale: [1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C [3] LC_TIME=en_US.UTF-8 LC_COLLATE=en_US.UTF-8 [5] LC_MONETARY=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8 [7] LC_PAPER=C LC_NAME=C [9] LC_ADDRESS=C LC_TELEPHONE=C [11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C attached base packages: [1] stats graphics grDevices utils datasets methods base

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