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  • Which of these algorithms is best for my goal?

    - by JonathonG
    I have created a program that restricts the mouse to a certain region based on a black/white bitmap. The program is 100% functional as-is, but uses an inaccurate, albeit fast, algorithm for repositioning the mouse when it strays outside the area. Currently, when the mouse moves outside the area, basically what happens is this: A line is drawn between a pre-defined static point inside the region and the mouse's new position. The point where that line intersects the edge of the allowed area is found. The mouse is moved to that point. This works, but only works perfectly for a perfect circle with the pre-defined point set in the exact center. Unfortunately, this will never be the case. The application will be used with a variety of rectangles and irregular, amorphous shapes. On such shapes, the point where the line drawn intersects the edge will usually not be the closest point on the shape to the mouse. I need to create a new algorithm that finds the closest point to the mouse's new position on the edge of the allowed area. I have several ideas about this, but I am not sure of their validity, in that they may have far too much overhead. While I am not asking for code, it might help to know that I am using Objective C / Cocoa, developing for OS X, as I feel the language being used might affect the efficiency of potential methods. My ideas are: Using a bit of trigonometry to project lines would work, but that would require some kind of intense algorithm to test every point on every line until it found the edge of the region... That seems too resource intensive since there could be something like 200 lines that would have each have to have as many as 200 pixels checked for black/white.... Using something like an A* pathing algorithm to find the shortest path to a black pixel; however, A* seems resource intensive, even though I could probably restrict it to only checking roughly in one direction. It also seems like it will take more time and effort than I have available to spend on this small portion of the much larger project I am working on, correct me if I am wrong and it would not be a significant amount of code (100 lines or around there). Mapping the border of the region before the application begins running the event tap loop. I think I could accomplish this by using my current line-based algorithm to find an edge point and then initiating an algorithm that checks all 8 pixels around that pixel, finds the next border pixel in one direction, and continues to do this until it comes back to the starting pixel. I could then store that data in an array to be used for the entire duration of the program, and have the mouse re-positioning method check the array for the closest pixel on the border to the mouse target position. That last method would presumably execute it's initial border mapping fairly quickly. (It would only have to map between 2,000 and 8,000 pixels, which means 8,000 to 64,000 checked, and I could even permanently store the data to make launching faster.) However, I am uncertain as to how much overhead it would take to scan through that array for the shortest distance for every single mouse move event... I suppose there could be a shortcut to restrict the number of elements in the array that will be checked to a variable number starting with the intersecting point on the line (from my original algorithm), and raise/lower that number to experiment with the overhead/accuracy tradeoff. Please let me know if I am over thinking this and there is an easier way that will work just fine, or which of these methods would be able to execute something like 30 times per second to keep mouse movement smooth, or if you have a better/faster method. I've posted relevant parts of my code below for reference, and included an example of what the area might look like. (I check for color value against a loaded bitmap that is black/white.) // // This part of my code runs every single time the mouse moves. // CGPoint point = CGEventGetLocation(event); float tX = point.x; float tY = point.y; if( is_in_area(tX,tY, mouse_mask)){ // target is inside O.K. area, do nothing }else{ CGPoint target; //point inside restricted region: float iX = 600; // inside x float iY = 500; // inside y // delta to midpoint between iX,iY and tX,tY float dX; float dY; float accuracy = .5; //accuracy to loop until reached do { dX = (tX-iX)/2; dY = (tY-iY)/2; if(is_in_area((tX-dX),(tY-dY),mouse_mask)){ iX += dX; iY += dY; } else { tX -= dX; tY -= dY; } } while (abs(dX)>accuracy || abs(dY)>accuracy); target = CGPointMake(roundf(tX), roundf(tY)); CGDisplayMoveCursorToPoint(CGMainDisplayID(),target); } Here is "is_in_area(int x, int y)" : bool is_in_area(NSInteger x, NSInteger y, NSBitmapImageRep *mouse_mask){ NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; NSUInteger pixel[4]; [mouse_mask getPixel:pixel atX:x y:y]; if(pixel[0]!= 0){ [pool release]; return false; } [pool release]; return true; }

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  • Need help with this question [closed]

    - by Jaime
    Occasionally, multiplying the sizes of nested loops can give an overestimate for the Big-Oh running time. This result happens when an innermost loop is infrequently executed. Give the Big-O analysis of the running time. Implement the following code and run for several values of N, and compare your analysis with the actual running times. for(int i = 1; i <= n; i++) for(int j = 1; j<=i * i; j++) if(j%i == 0) for(int k = 0; k < j; k++) sum++;

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  • Tips for communication between JS browser game and node.js server?

    - by Petteri Hietavirta
    I am tinkering around with some simple Canvas based cave flyer game and I would like to make it multiplayer eventually. The plan is to use Node.js on the server side. The data sent over would consists of position of each player, direction, velocity and such. The player movements are simple force physics, so I should be able to extrapolate movements before next update from server. Any tips or best practices on the communications side? I guess web sockets are the way to go. Should I send information in every pass of the game loop or with specified intervals? Also, I don't mind if it doesn't work with older browsers.

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  • Fiscal Cliff

    - by Carolyn Cozart
    As December 31, 2012 quickly approaches, so does the deadline to extend the Bush Era Tax Cuts which were extended under the Budget Control Act of 2011.  PeopleSoft realizes that there may be some customer anxiety over the delayed withholding tables. PeopleSoft is unable to move forward with delivering the tax changes until we get the official ruling and withholding tables from the IRS.  Please be assured that our legislative analysts are in the loop and are monitoring this situation daily.  Any changes will be included in a special posting. We have created a Knowledge Document in My Oracle Support, Document ID 1332295.1 to keep you up to date on the pending changes.

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  • Error in my Separating Axis Theorem collision code

    - by Holly
    The only collision experience i've had was with simple rectangles, i wanted to find something that would allow me to define polygonal areas for collision and have been trying to make sense of SAT using these two links Though i'm a bit iffy with the math for the most part i feel like i understand the theory! Except my implementation somewhere down the line must be off as: (excuse the hideous font) As mentioned above i have defined a CollisionPolygon class where most of my theory is implemented and then have a helper class called Vect which was meant to be for Vectors but has also been used to contain a vertex given that both just have two float values. I've tried stepping through the function and inspecting the values to solve things but given so many axes and vectors and new math to work out as i go i'm struggling to find the erroneous calculation(s) and would really appreciate any help. Apologies if this is not suitable as a question! CollisionPolygon.java: package biz.hireholly.gameplay; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import biz.hireholly.gameplay.Types.Vect; public class CollisionPolygon { Paint paint; private Vect[] vertices; private Vect[] separationAxes; int x; int y; CollisionPolygon(Vect[] vertices){ this.vertices = vertices; //compute edges and separations axes separationAxes = new Vect[vertices.length]; for (int i = 0; i < vertices.length; i++) { // get the current vertex Vect p1 = vertices[i]; // get the next vertex Vect p2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; // subtract the two to get the edge vector Vect edge = p1.subtract(p2); // get either perpendicular vector Vect normal = edge.perp(); // the perp method is just (x, y) => (-y, x) or (y, -x) separationAxes[i] = normal; } paint = new Paint(); paint.setColor(Color.RED); } public void draw(Canvas c, int xPos, int yPos){ for (int i = 0; i < vertices.length; i++) { Vect v1 = vertices[i]; Vect v2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; c.drawLine( xPos + v1.x, yPos + v1.y, xPos + v2.x, yPos + v2.y, paint); } } public void update(int xPos, int yPos){ x = xPos; y = yPos; } /* consider changing to a static function */ public boolean intersects(CollisionPolygon p){ // loop over this polygons separation exes for (Vect axis : separationAxes) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // loop over the other polygons separation axes Vect[] sepAxesOther = p.getSeparationAxes(); for (Vect axis : sepAxesOther) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // if we get here then we know that every axis had overlap on it // so we can guarantee an intersection return true; } /* Note projections wont actually be acurate if the axes aren't normalised * but that's not necessary since we just need a boolean return from our * intersects not a Minimum Translation Vector. */ private Vect minMaxProjection(Vect axis) { float min = axis.dot(new Vect(vertices[0].x+x, vertices[0].y+y)); float max = min; for (int i = 1; i < vertices.length; i++) { float p = axis.dot(new Vect(vertices[i].x+x, vertices[i].y+y)); if (p < min) { min = p; } else if (p > max) { max = p; } } Vect minMaxProj = new Vect(min, max); return minMaxProj; } public Vect[] getSeparationAxes() { return separationAxes; } public Vect[] getVertices() { return vertices; } } Vect.java: package biz.hireholly.gameplay.Types; /* NOTE: Can also be used to hold vertices! Projections, coordinates ect */ public class Vect{ public float x; public float y; public Vect(float x, float y){ this.x = x; this.y = y; } public Vect perp() { return new Vect(-y, x); } public Vect subtract(Vect other) { return new Vect(x - other.x, y - other.y); } public boolean overlap(Vect other) { if(y > other.x && other.y > x){ return true; } return false; } /* used specifically for my SAT implementation which i'm figuring out as i go, * references for later.. * http://www.gamedev.net/page/resources/_/technical/game-programming/2d-rotated-rectangle-collision-r2604 * http://www.codezealot.org/archives/55 */ public float scalarDotProjection(Vect other) { //multiplier = dot product / length^2 float multiplier = dot(other) / (x*x + y*y); //to get the x/y of the projection vector multiply by x/y of axis float projX = multiplier * x; float projY = multiplier * y; //we want to return the dot product of the projection, it's meaningless but useful in our SAT case return dot(new Vect(projX,projY)); } public float dot(Vect other){ return (other.x*x + other.y*y); } }

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  • Should I be worried if I solve a lot of my problems the same way?

    - by Bryan Harrington
    I really enjoy programming games and puzzle creators/games. I find myself engineering a lot of these problems the same way and ultimately using similar technique to program them that I'm really comfortable with. To give you brief insight, I like to create graphs where nodes are represented with objects. These object hold data such as coordinates, positions and of course references to other neighboring objects. I'll place them all in a data structure and make decisions on this information in a "game loop". While this is a brief example, its not exact in all situations. It's just one way I feel really comfortable with. Is this bad?

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  • circle - rectangle collision in 2D, most efficient way

    - by john smith
    Suppose I have a circle intersecting a rectangle, what is ideally the least cpu intensive way between the two? method A calculate rectangle boundaries loop through all points of the circle and, for each of those, check if inside the rect. method B calculate rectangle boundaries check where the center of the circle is, compared to the rectangle make 9 switch/case statements for the following positions: top, bottom, left, right top left, top right, bottom left, bottom right inside rectangle check only one distance using the circle's radius depending on where the circle happens t be. I know there are other ways that are definitely better than these two, and if could point me a link to them, would be great but, exactly between those two, which one would you consider to be better, regarding both performance and quality/precision? Thanks in advance.

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  • Can't disable Alt + mouse buttons combinations

    - by Andrey
    I've already searched through the questions, and didn't find the same question as I want to ask. I'm working in blender and there are some combinations that I am used to and remapping them in blender would be the last resort, not the first. I have tried to disable Alt+LMB and Alt+RMB actions in ccsm, I've tried to do this in dconf or gconf editors as well, but nothing helped. As soon as I close the editors or get back to the main screen of ccsm, these combinations are enabled again. So, for example, instead of selecting an edge loop in blender with Alt+RMB, I get this goddamn menu offering me to move the window to another workspace, etc. I really don't need this function, so I'd rather switch it off instead of remapping the hotkeys I'm used to in blender.

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  • What does ENDOFMENU do?

    - by Raymond
    I have been given an example program, I am wondering what exactly the <<ENDOFMENU and ENDOFMENU does, won't it work the same if you leave it out and just use the while loop? #!/bin/sh echo "Menu test program..."; stop=0; while test $stop -eq 0; do cat<<ENDOFMENU 1: print the date 2,3 : print the current working directory 4: exit ENDOFMENU echo; echo -e "your choice?\c" read reply echo case $reply in "1") date ;; "2"|"3") pwd ;; "4") stop=1 ;; *) echo illegal choice esac done

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  • Why ISO master (editor) does not read Windows images

    - by Jacek Blocki
    I have the followjng problem with ISO master software: I try to edit WIndows 7 ISO image $ isomaster windows7.iso The file does open, unfortunately all I get is README with message: This disc contains a "UDF" file system and requires an operating system that supports the ISO-13346 "UDF" file system specification. isomaster comes form Ubuntu repository, I am using 12.04. The system has kernel support for UDF installed, I can mount above ISO (mount -o loop) and see its content read only. Any idea how to fix it? Using other than isomaster tool is also an option. Regards, Jacek

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  • Implementing a bit shift using AND, NOT, ADD [closed]

    - by fdart17
    I'm implementing a 16-bit left bit shift by r bits, and I only have access to AND, NOT and ADD. There are 3 condition codes, negative, zero and positive, which are set when you use any of these operations. How I went about it was : (1) And the number with 1000 0000 0000 0000 to set condition codes to positive if the most significant bit is 1. (2) Add the number with itself. This shifts bits one to the left. (3) If the MSB was 1, add 1 to the result. (4) Loop threw (1)-(3) r times. I'm wondering if anyone has any hints to some more efficient methods? Thanks!

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  • In which object should I implement wait()/notify()?

    - by Christopher Francisco
    I'm working in an Android project with multithreading. Basically I have to wait to the server to respond before sending more data. The data sending task is delimited by the flag boolean hasServerResponded so the Thread will loop infinitely without doing anything until the flag becomes true. Since this boolean isn't declared as volatile (yet), and also looping without doing anything wastes resources, I thought maybe I should use AtomicBoolean and also implement wait() / notify() mechanism. Should I use the AtomicBoolean object notify() and wait() methods or should I create a lock Object?

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  • Beginners Guide to Visual Studio LightSwitch makes it easy to take a closer look

    - by Jim Duffy
    Following up on my most recent post about LightSwitch I thought I’d keep you in the loop on a valuable LightSwitch resource. The Beginners Guide to Visual Studio LightSwitch provides a jump start to get you and the department-level-typical-Access-application-developing-power-user rolling with LightSwitch in no time. The guide is broken down into 4 easy to follow parts. Beginners Guide to Visual Studio LightSwitch (Part – 1) – Working with New Data Entry Screen Beginners Guide to Visual Studio LightSwitch (Part – 2) – Working with Search Screen Beginners Guide to Visual Studio LightSwitch (Part – 3) – Working with Editable DataGrid Screen Beginners Guide to Visual Studio LightSwitch (Part – 4) – Working with List and Details Screen I mentioned it in my prior post but don’t forget to check out Beth Massi’s blog for additional information on Visual Studio LightSwitch. Have a day.

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  • Is it a waste of time to free resources before I exit a process?

    - by Martin
    Let's consider a fictional program that builds a linked list in the heap, and at the end of the program there is a loop that frees all the nodes, and then exits. For this case let's say the linked list is just 500K of memory, and no special space managing is required. Is that a wast of time, because the OS will do that anyway? Will there be a different behavior later? Is that different according to the OS version? I'm mainly interested in UNIX based systems, but any information will be appreciated. I had today my first lesson in OS course and I'm wondering about that now.

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  • How to play the sound of an object sliding on another object for a variable duration

    - by Antoine
    I would like to add sound effects to a basic 2D game. For example, a stone sphere is rolling on wood surface. Let's say I have a 2 second audio recording of this. How could I use the sample to add sound for an arbitrary duration ? So far I have two solutions in mind: a/ record the sound for an amount of time that is greater than the maximum expected duration, and play only a part of it; b/ extract a small portion of the sample and play it in a loop for the duration of the move; however I'm not sure if it makes sense with an audio wave.

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  • Implementing set of processes in a stored procedure or through the code?

    - by just_name
    I want to know what's the suitable method to implement the following case (best practice). If i make a set of processes like this : 1- select data from set of DB tables. 2- loop on the selected result . 3- Make some checks on each iteration . 4- Insert the result in another table . Implementing the previous steps in a stored procedure or in a transaction through my code (asp.net) . ? Concerning the performance , security and reliability issues .

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  • How do I stop stretching during window re-size in XNA?

    - by Bradley Uffner
    In my windowed mode XNA game when the user resizes the window the game stops updating the window and the last frame drawn is stretched and distorted until the user releases the mouse and the resize completes. Is there any way to have the game continue to run "normally", updating frames and redrawing the screen, during the resize event? I realize that keeping the render loop going while resizing may not be possible or recommended due do hardware managed resources getting continually created and destroyed, but is there any way to stop the ugly stretching? Ideally by leaving the existing frame unscaled in the top left, or with a black screen if that isn't possible.

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  • Exclude category from Wordpress home page unless it belongs to another category

    - by sirlancelot
    I have multiple users adding content to restricted categories (using RoleScoper) in my Wordpress setup that don't show up on the homepage (custom template with query_posts()). I'm looking for a way to "promote" the submitted content to the homepage by adding it to another category. My loop code looks like this: <?php query_posts($query_string . '&cat=-37'); if (have_posts()): while (have_posts()): the_post(); ?> This will exclude all posts in category 37. However, even if I add the post to a different category it still gets excluded. Is there a way to exclude a post if it belongs to just that one category?

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  • Frame timing for GLFW versus GLUT

    - by linello
    I need a library which ensures me that the timing between frames are more constant as possible during an experiment of visual psychophics. This is usually done synchronizing the refresh rate of the screen with the main loop. For example if my monitor runs at 60Hz I would like to specify that frequency to my framework. For example if my gameloop is the following void gameloop() { // do some computation printDeltaT(); Flip buffers } I would like to have printed a constant time interval. Is it possible with GLFW?

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  • Finding the groups of a user in WLS with OPSS

    - by user12587121
    How to find the group memberships for a user from a web application running in Weblogic server ?  This is useful for building up the profile of the user for security purposes for example. WLS as a container offers an identity store service which applications can access to query and manage identities known to the container.  This article for example shows how to recover the groups of the current user, but how can we find the same information for an arbitrary user ? It is the Oracle Platform for Securtiy Services (OPSS) that looks after the identity store in WLS and so it is in the OPSS APIs that we can find the way to recover this information. This is explained in the following documents.  Starting from the FMW 11.1.1.5 book list, with the Security Overview document we can see how WLS uses OPSS: Proceeding to the more detailed Application Security document, we find this list of useful references for security in FMW. We can follow on into the User/Role API javadoc. The Application Security document explains how to ensure that the identity store is configured appropriately to allow the OPSS APIs to work.  We must verify that the jps-config.xml file where the application  is deployed has it's identity store configured--look for the following elements in that file: <serviceProvider type="IDENTITY_STORE" name="idstore.ldap.provider" class="oracle.security.jps.internal.idstore.ldap.LdapIdentityStoreProvider">             <description>LDAP-based IdentityStore Provider</description>  </serviceProvider> <serviceInstance name="idstore.ldap" provider="idstore.ldap.provider">             <property name="idstore.config.provider" value="oracle.security.jps.wls.internal.idstore.WlsLdapIdStoreConfigProvider"/>             <property name="CONNECTION_POOL_CLASS" value="oracle.security.idm.providers.stdldap.JNDIPool"/></serviceInstance> <serviceInstanceRef ref="idstore.ldap"/> The document contains a code sample for using the identity store here. Once we have the identity store reference we can recover the user's group memberships using the RoleManager interface:             RoleManager roleManager = idStore.getRoleManager();            SearchResponse grantedRoles = null;            try{                System.out.println("Retrieving granted WLS roles for user " + userPrincipal.getName());                grantedRoles = roleManager.getGrantedRoles(userPrincipal, false);                while( grantedRoles.hasNext()){                      Identity id = grantedRoles.next();                      System.out.println("  disp name=" + id.getDisplayName() +                                  " Name=" + id.getName() +                                  " Principal=" + id.getPrincipal() +                                  "Unique Name=" + id.getUniqueName());                     // Here, we must use WLSGroupImpl() to build the Principal otherwise                     // OES does not recognize it.                      retSubject.getPrincipals().add(new WLSGroupImpl(id.getPrincipal().getName()));                 }            }catch(Exception ex) {                System.out.println("Error getting roles for user " + ex.getMessage());                ex.printStackTrace();            }        }catch(Exception ex) {            System.out.println("OESGateway: Got exception instantiating idstore reference");        } This small JDeveloper project has a simple servlet that executes a request for the user weblogic's roles on executing a get on the default URL.  The full code to recover a user's goups is in the getSubjectWithRoles() method in the project.

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  • Simpler alternative to AngelScript

    - by Vee
    I want to give players the ability to create and share bullet patterns for a shoot'em up. The pattern scripts should have all the common programming stuff like loops, if/else, variables, and so on. But in the end, I just want them to call a "spawn bullet at X, Y with Z angle and A speed" in the C++ game. To spawn a circle of bullets, the user should only have to write a script with a for loop that goes from 0 to 360 and calls the spawn bullet function on every iteration. I tried integrating AngelScript, but I am getting nowhere - it looks way to complex for a simple task like this one. Is there an easy to integrate library that can solve my problem? Thanks.

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  • Tips and Tools for creating Spritesheet animations

    - by Spooks
    I am looking for a tool that I can use to create sprite sheet easily. Right now I am using Illustrator, but I can never get the center of the character in the exact position, so it looks like it is moving around(even though its always in one place), while being loop through the sprite sheet. Is there any better tools that I can be using? Also what kind of tips would you give for working with a sprite sheet? Should I create each part of the character in individual layers (left arm, right arm, body, etc.) or everything at once? any other tips would also be helpful! thank you

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  • Any significant performance cost to using BlendState.Premultiplied?

    - by Donutz
    Normally I guess you'd use BlendState.AlphaBlend because normally when you load your textures through the pipeline they're already premultiplied. However, if you're loading textures at runtime from PNGs or some such, you have to loop through the pixels and premultiply them, which can take a long time if you've got a lot of textures to load. So it looks (haven't tried it) like using BlendState.Premultiplied instead of BlendState.AlphaBlend should handle non-premultiplied textures and produce the same visual result, without all the startup costs. I have to wonder if there's a non-obvious cost to doing this, like a huge drop in performance or something. Anyone know?

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  • parallel_for_each from amp.h – part 1

    - by Daniel Moth
    This posts assumes that you've read my other C++ AMP posts on index<N> and extent<N>, as well as about the restrict modifier. It also assumes you are familiar with C++ lambdas (if not, follow my links to C++ documentation). Basic structure and parameters Now we are ready for part 1 of the description of the new overload for the concurrency::parallel_for_each function. The basic new parallel_for_each method signature returns void and accepts two parameters: a grid<N> (think of it as an alias to extent) a restrict(direct3d) lambda, whose signature is such that it returns void and accepts an index of the same rank as the grid So it looks something like this (with generous returns for more palatable formatting) assuming we are dealing with a 2-dimensional space: // some_code_A parallel_for_each( g, // g is of type grid<2> [ ](index<2> idx) restrict(direct3d) { // kernel code } ); // some_code_B The parallel_for_each will execute the body of the lambda (which must have the restrict modifier), on the GPU. We also call the lambda body the "kernel". The kernel will be executed multiple times, once per scheduled GPU thread. The only difference in each execution is the value of the index object (aka as the GPU thread ID in this context) that gets passed to your kernel code. The number of GPU threads (and the values of each index) is determined by the grid object you pass, as described next. You know that grid is simply a wrapper on extent. In this context, one way to think about it is that the extent generates a number of index objects. So for the example above, if your grid was setup by some_code_A as follows: extent<2> e(2,3); grid<2> g(e); ...then given that: e.size()==6, e[0]==2, and e[1]=3 ...the six index<2> objects it generates (and hence the values that your lambda would receive) are:    (0,0) (1,0) (0,1) (1,1) (0,2) (1,2) So what the above means is that the lambda body with the algorithm that you wrote will get executed 6 times and the index<2> object you receive each time will have one of the values just listed above (of course, each one will only appear once, the order is indeterminate, and they are likely to call your code at the same exact time). Obviously, in real GPU programming, you'd typically be scheduling thousands if not millions of threads, not just 6. If you've been following along you should be thinking: "that is all fine and makes sense, but what can I do in the kernel since I passed nothing else meaningful to it, and it is not returning any values out to me?" Passing data in and out It is a good question, and in data parallel algorithms indeed you typically want to pass some data in, perform some operation, and then typically return some results out. The way you pass data into the kernel, is by capturing variables in the lambda (again, if you are not familiar with them, follow the links about C++ lambdas), and the way you use data after the kernel is done executing is simply by using those same variables. In the example above, the lambda was written in a fairly useless way with an empty capture list: [ ](index<2> idx) restrict(direct3d), where the empty square brackets means that no variables were captured. If instead I write it like this [&](index<2> idx) restrict(direct3d), then all variables in the some_code_A region are made available to the lambda by reference, but as soon as I try to use any of those variables in the lambda, I will receive a compiler error. This has to do with one of the direct3d restrictions, where only one type can be capture by reference: objects of the new concurrency::array class that I'll introduce in the next post (suffice for now to think of it as a container of data). If I write the lambda line like this [=](index<2> idx) restrict(direct3d), all variables in the some_code_A region are made available to the lambda by value. This works for some types (e.g. an integer), but not for all, as per the restrictions for direct3d. In particular, no useful data classes work except for one new type we introduce with C++ AMP: objects of the new concurrency::array_view class, that I'll introduce in the post after next. Also note that if you capture some variable by value, you could use it as input to your algorithm, but you wouldn’t be able to observe changes to it after the parallel_for_each call (e.g. in some_code_B region since it was passed by value) – the exception to this rule is the array_view since (as we'll see in a future post) it is a wrapper for data, not a container. Finally, for completeness, you can write your lambda, e.g. like this [av, &ar](index<2> idx) restrict(direct3d) where av is a variable of type array_view and ar is a variable of type array - the point being you can be very specific about what variables you capture and how. So it looks like from a large data perspective you can only capture array and array_view objects in the lambda (that is how you pass data to your kernel) and then use the many threads that call your code (each with a unique index) to perform some operation. You can also capture some limited types by value, as input only. When the last thread completes execution of your lambda, the data in the array_view or array are ready to be used in the some_code_B region. We'll talk more about all this in future posts… (a)synchronous Please note that the parallel_for_each executes as if synchronous to the calling code, but in reality, it is asynchronous. I.e. once the parallel_for_each call is made and the kernel has been passed to the runtime, the some_code_B region continues to execute immediately by the CPU thread, while in parallel the kernel is executed by the GPU threads. However, if you try to access the (array or array_view) data that you captured in the lambda in the some_code_B region, your code will block until the results become available. Hence the correct statement: the parallel_for_each is as-if synchronous in terms of visible side-effects, but asynchronous in reality.   That's all for now, we'll revisit the parallel_for_each description, once we introduce properly array and array_view – coming next. Comments about this post by Daniel Moth welcome at the original blog.

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  • How do I simulate the mouse and keyboard using C# or C++?

    - by Art
    I want to start develop for Kinect, but hardest theme for it - how to send keyboard and mouse input to any application. In previous question I got an advice to develop my own driver for this devices, but this will take a while. I imagine application like a gate, that can translate SendMessage's into system wide input or driver application with API to send this inputs. So I wonder, is there are drivers or simulators that can interact with C# or C++? Small edition: SendMessage, PostMessage, keybd_event will work only on Windows application with common messages loop. So I need driver application that will work on low, kernel, level.

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