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• GSL Uniform Random Number Generator

  - by Jamaia

  I want to use GSL's uniform random number generator. On their website, they include this sample code: #include <stdio.h> #include <gsl/gsl_rng.h> int main (void) { const gsl_rng_type * T; gsl_rng * r; int i, n = 10; gsl_rng_env_setup(); T = gsl_rng_default; r = gsl_rng_alloc (T); for (i = 0; i < n; i++) { double u = gsl_rng_uniform (r); printf ("%.5f\n", u); } gsl_rng_free (r); return 0; } However, this does not rely on any seed and so, the same random numbers will be produced each time. They also specify the following: The generator itself can be changed using the environment variable GSL_RNG_TYPE. Here is the output of the program using a seed value of 123 and the multiple-recursive generator mrg, $ GSL_RNG_SEED=123 GSL_RNG_TYPE=mrg ./a.out But I don't understand how to implement this. Any ideas as to what modifications I can make to the above code to incorporate the seed?

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• How to get a Toshiba L505 to boot USB or CD

  - by ShroudedCloud

  OK, have a Toshiba L505 (not sure of the extended model number) that got a virus on Windows and will no longer will boot into that, so I'm trying to revive it with Ubuntu. Problem is, when I tell it to boot into a USB image of 12.04 32- or 64-bit, 13.04 64-bit, or elementary Luna 32-bit, it gives me some screen with a copyright from 2000 for Intel, invariably spits out a "media not recognized" type of error and then says PXE-ROM exiting. Well, that's annoying. So I went in with a CD (12.04 x86_64 having tried 32-bit in the past as well). Boot menu, select, starts running. Seeing the loading screen for Ubuntu, going well... until it's not. Again, invariably, it fails. The CD drive will cease spinning at around the same time each time and then the laptop will stop doing everything altogether (at least, everything spins down and it goes quiet). As far as I can tell, it's not to do with what function is being loaded from the CD at the time (because that bit is variable). I'd love to be able to boot from USB (since it will be all but required going forward), but getting the CD to work would be wondrous too. Anyone have any ideas of where I can go from here to try to fix this? My friends and I have turned up nothing.

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• Best way to blend colors in tile lighting? (XNA)

  - by Lemoncreme

  I have made a color, decent, recursive, fast tile lighting system in my game. It does everything I need except one thing: different colors are not blended at all: Here is my color blend code: return (new Color( (byte)MathHelper.Clamp(color.R / factor, 0, 255), (byte)MathHelper.Clamp(color.G / factor, 0, 255), (byte)MathHelper.Clamp(color.B / factor, 0, 255))); As you can see it does not take the already in place color into account. color is the color of the previous light, which is weakened by the above code by factor. If I wanted to blend using the color already in place, I would use the variable blend. Here is an example of a blend that I tried that failed, using blend: return (new Color( (byte)MathHelper.Clamp(((color.R + blend.R) / 2) / factor, 0, 255), (byte)MathHelper.Clamp(((color.G + blend.G) / 2) / factor, 0, 255), (byte)MathHelper.Clamp(((color.B + blend.B) / 2) / factor, 0, 255))); This color blend produces inaccurate and strange results. I need a blend that is accurate, like the first example, that blends the two colors together. What is the best way to do this?

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• Why do I get "permission denied" errors with Python easy_install?

  - by ATMathew

  I'm an Ubuntu newbie and have been trying to install python's easy_install so that I don't have to deal with source files when install Python libraries. I"ve ran the following, and it seems to install the correct applications: sudo apt-get install python-setuptools However, when i run easy_install sqlalchemy or easy_install pysqlite3, it doesn't work. I get the following error message: install_dir /usr/local/lib/python2.6/dist-packages/ error: can't create or remove files in install directory The following error occurred while trying to add or remove files in the installation directory: [Errno 13] Permission denied: '/usr/local/lib/python2.6/dist-packages/test-easy-install-1674.pth' The installation directory you specified (via --install-dir, --prefix, or the distutils default setting) was: /usr/local/lib/python2.6/dist-packages/ Perhaps your account does not have write access to this directory? If the installation directory is a system-owned directory, you may need to sign in as the administrator or "root" account. If you do not have administrative access to this machine, you may wish to choose a different installation directory, preferably one that is listed in your PYTHONPATH environment variable. For information on other options, you may wish to consult the documentation at: http://packages.python.org/distribute/easy_install.html Please make the appropriate changes for your system and try again. Help! Abraham

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• Beginning with shell scripting

  - by Kevin Wyman

  I am fresh into Ubuntu and one of my goals is shell scripting for personal (and maybe public) use. I'm a novice, though I do understand some of the basics (e.g. what a variable, string, loop, etc... is) but to get the most of scripting I need to learn in-depth. I figure the best way to do that is to jump right into scripting and ask questions only pertinent to the stage I am at in my attempted script. Scenario: I have edited my sudoers file to allow my non-root user to run sudo commands without being prompted for a password. Question: In vim, what would be the best code to use for a function that checks whether this condition is [true], If not, prompt the user if they want the script to edit and save the sudoers file to make this condition [true]? Layout - If condition is true, carry-on with rest of script. If condition is not true, the script silently edits/adds the line: %sudo ALL=(ALL:ALL) NOPASSWD: ALL in the sudoers file, saves and then continues on with the next part of the script. Any help with this would be greatly appreciated and assist me in my journey to writing shell scripts.

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• What are the requirements to test a website using jquery.get() ? [migrated]

  - by Frankie

  I am working on a simple website. It has to search quite a few text files in different sub-folders. The rest of the page uses jquery, so I would like to use it for this also. The function I am looking at is .get() for downloading the files. So my main question is, can I test this on my local computer (Ubuntu Linux) or do I have to have it uploaded to a server? Also, if there's a better way to go about this, that would be nice to know. However, I'm more worried about getting it working. Thanks, Frankie PS: Heres the JS/jQuery code for downloading the files to an array. g_lists = new Array(); $(":checkbox").each(function(i){ if ($(this).attr("name") != "0") { var path = "../" + $(this).attr("name") + ".txt"; $("#bot").append("<br />" + path); // debug $.get(path, function(data){ g_lists[i] = data; $("#bot").html(data); }); } else { g_lists[i] = ""; } }); Edit: Just a note about the path variable. I think it's correct, but I'm not 100% sure. I'm new to web development. Here's some examples it produces and the directory tree of the site. Maybe it will help, can't hurt. . +-- include ¦   +-- jquery.js ¦   +-- load.js +-- index.xhtml +-- style.css +-- txt    +-- Scripting_Tools    +-- Editors.txt    +-- Other.txt Examples of path: ../txt/Scripting_Tools/Editors.txt ../txt/Scripting_Tools/Other.txt Well I'm a new user, so I can't "answer" my own question, so I'll just post it here: After asking for help on a IRC chat channel specific to jQuery, I was told I could use this on a local host. To do this I installed Apache web server, and copied my site into it's directory. More information on setting it up can be found here: http://www.howtoforge.com/ubuntu_debian_lamp_server Then to run the site I navigated my browser to "localhost" and everything works.

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• Using SQL tables for storing user created level stats. Is there a better way?

  - by Ivan

  I am developing a racing game in which players can create their own tracks and upload them to a server. Players will be able to compare their best track times to their friends and see world records. I was going to generate a table for each track submitted to store the best times of each player who plays the track. However, I can't predict how many will be uploaded and I imagine too many tables might cause problems, or is this a valid method? I considered saving each player's best times in a string in a single table field like so: level1:00.45;level2:00.43;level3:00.12 If I did this I wouldn't need a separate table for each level (each level could just have a row in a 'WorldRecords' table). However, this just causes another problem because the text would eventually reach the limit for varchar length. I also considered storing the times data in XML files. This would avoid database issues and server disk space can be increased if needed. But I imagine this would be very slow. To update one players best time on one level, I would have to check every node in the file to find their time record to update. Apologies for the wall of text. Any suggestions would be appreciated.

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• Incorporating libs into module pattern

  - by webnesto

  I have recently started using require.js (along with Backbone.js, jQuery, and a handful of other JavaScript libs) and I love the module pattern (here's a nice synopsis if you're unfamiliar: http://www.adequatelygood.com/2010/3/JavaScript-Module-Pattern-In-Depth). Something I'm running up against is best practices on incorporating libs that don't (out of the box) support the module pattern. For example, jQuery without modification is going to load into a global jQuery variable and that's that. Require.js recognizes this and provides an example project for download with a (slightly) modified version of jQuery to incorporate with a require.js project. This goes against everything I've ever learned about using external libs - never modify the source. I can list a ton of reasons. Regardless, this is not an approach I'm comfortable with. I have been using a mixed approach - wherein I build/load the "traditional" JS libraries in a "traditional" way (available in the global namespace) and then using the module pattern for all of my application code. This seems okay to me, but it bugs me because one of the real beauties of the module pattern (no globals) is getting perverted. Anyone else got a better solution to this problem?

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• Algorithm for detecting windows in a room

  - by user2733436

  I am dealing with the following problem and i was looking to write a Pseudo-code for developing an algorithm that can be generic for such a problem. Here is what i have come up with thus far. STEP 1 In this step i try to get the robot where it maybe placed to the top left corner. Turn Left - If no window or Wall detected keep going forward 1 unit.. if window or wall detected -Turn right -- if no window or Wall detected keep going forward.. if window or wall detected then top left corner is reached. STEP 2 (We start counting windows after we get to this stage to avoid miscounting) I would like to declare a variable called turns as it will help me keep track if robot has gone around entire room. Turns = 4; Now we are facing north and placed on top left corner. while(turns0){ If window or wall detected (if window count++) Turn Right Turn--; While(detection!=wall || detection!=window){ move 1 unit forward Turn left (if window count++) Turn right } } I believe in doing so the robot will go around the entire room and count windows and it will stop once it has gone around the entire room as the turns get decremented. I don't feel this is the best solution and would appreciate suggestions on how i can improve my Pseudo-code. I am not looking for any code just a algorithm on solving such a problem and that is why i have not posted this in stack overflow. I apologize if my Pseudo-code is poorly written please make suggestions if i can improve that as i am new to this. Thanks.

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• When mapping the surface of a sphere with tiles, how might you deal with polar distortion?

  - by clweeks

  It's easy to deal with the way locations interact on a clean Cartesian grid. It's just vanilla math. And you can kind of ignore the geometry of the sphere's surface for a bunch of it if you want to just truncate the poles or something. But I keep coming up with ideas for games where the polar space matters. Geo-coded ARGs and global roguelikes and stuff. I want square(ish?) locations -- reasonably representable by square tiles of the same size across the globe, anyway. This has to be a solved problem, right? What are the solutions? ETA: At the equator -- and assuming that your square locations are reasonably small, it's close enough to true that you can get away with having one square in the rows north and south of the most equatorial row. And you could probably get away with that by just hand-waving the difference up to like 45-degrees or so. But eventually, you need to have fewer squares in a pole-ward circumferential row. If I reduce the length of the row by one and offset the squares by 1/2 then they're just like hexes and it's relatively easy to do the coding to keep track of the connections. But as you get pole-ward, it gets more and more extreme. Projecting the surface of the world onto the surface of a cube is tempting. But I figured there must be more elegant solutions already in use. If I did the cube thing (not dissecting it further through geodesy) Are there any pros and cons related to placing the pole at the center of a face or at the vertex of three sides?

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• Why doesn't Firefox cache my images and CSS

  - by Richard A

  I am using IIS7, I have already set up the following. But when I run Firefox it seems not to cache any of my images even with "remember history" set. <?xml version="1.0" encoding="UTF-8"?> <configuration> <system.webServer> <staticContent> <clientCache cacheControlCustom="public" cacheControlMode="UseMaxAge" cacheControlMaxAge="7.00:00:00" /> </staticContent> </system.webServer> </configuration> However when I use Firebug it still points to Firefox not caching images and CSS: public,max-age=604800 Content-Type text/css Content-Encoding gzip Last-Modified Mon, 27 Jun 2011 03:53:22 GMT Accept-Ranges bytes Etag "507968c27d34cc1:0" Vary Accept-Encoding Server Microsoft-IIS/7.5 X-Powered-By ASP.NET Date Mon, 27 Jun 2011 13:06:41 GMT Content-Length 5067 Request Headersview source Host www.xx.com User-Agent Mozilla/5.0 (Windows NT 6.1; rv:2.0.1) Gecko/20100101 Firefox/4.0.1 Accept text/css,*/*;q=0.1 Accept-Language en-us,en;q=0.5 Accept-Encoding gzip, deflate Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7 Keep-Alive 115 Connection keep-alive Referer http://www.xx.com/ Cookie __utma=62996397.135679654.1309106351.1309159743.1309164158.8; __utmz=62996397.1309106351.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none); __utmc=62996397

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• Converting a bounded knapsack problem to 0/1 knapsack problem

  - by Ants

  I ran across a problem where goal was to use dynamic programming (instead of other approaches). There is a distance to be spanned, and a set of cables of different lengths. What is the minimum number of cables needed to span the distance exactly? To me this looked like a knapsack problem, but since there could be multiples of a particular length, it was a bounded knapsack problem, rather than a 0/1 knapsack problem. (Treat the value of each item to be its weight.) Taking the naive approach (and not caring about the expansion of the search space), the method I used to convert the bounded knapsack problem into a 0/1 knapsack problem, was simply break up the multiples into singles and apply the well-known dynamic programming algorithm. Unfortunately, this leads to sub-optimal results. For example, given cables: 1 x 10ft, 1 x 7ft, 1 x 6ft, 5 x 3ft, 6 x 2ft, 7 x 1ft If the target span is 13ft, the DP algorithm picks 7+6 to span the distance. A greedy algorithm would have picked 10+3, but it's a tie for minimum number of cables. The problem arises, when trying to span 15ft. The DP algorithm ended up picking 6+3+3+3 to get 4 cables, while the greedy algorithm correctly picks 10+3+2 for only 3 cables. Anyway, doing some light scanning of converting bounded to 0/1, it seems like the well-known approach to convert multiple items to { p, 2p, 4p ... }. My question is how does this conversion work if p+2p+4p does not add up to the number of multiple items. For example: I have 5 3ft cables. I can't very well add { 3, 2x3, 4x3 } because 3+2x3+4x3 5x3. Should I add { 3, 4x3 } instead? [I'm currently trying to grok the "Oregon Trail Knapsack Problem" paper, but it currently looks like the approach used there is not dynamic programming.]

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• Oracle R Distribution 2-13.2 Update Available

  - by Sherry LaMonica

  Oracle has released an update to the Oracle R Distribution, an Oracle-supported distribution of open source R. Oracle R Distribution 2-13.2 now contains the ability to dynamically link the following libraries on both Windows and Linux: The Intel Math Kernel Library (MKL) on Intel chips The AMD Core Math Library (ACML) on AMD chips To take advantage of the performance enhancements provided by Intel MKL or AMD ACML in Oracle R Distribution, simply add the MKL or ACML shared library directory to the LD_LIBRARY_PATH system environment variable. This automatically enables MKL or ACML to make use of all available processors, vastly speeding up linear algebra computations and eliminating the need to recompile R.  Even on a single core, the optimized algorithms in the Intel MKL libraries are faster than using R's standard BLAS library. Open-source R is linked to NetLib's BLAS libraries, but they are not multi-threaded and only use one core. While R's internal BLAS are efficient for most computations, it's possible to recompile R to link to a different, multi-threaded BLAS library to improve performance on eligible calculations. Compiling and linking to R yourself can be involved, but for many, the significantly improved calculation speed justifies the effort. Oracle R Distribution notably simplifies the process of using external math libraries by enabling R to auto-load MKL or ACML. For R commands that don't link to BLAS code, taking advantage of database parallelism using embedded R execution in Oracle R Enterprise is the route to improved performance. For more information about rebuilding R with different BLAS libraries, see the linear algebra section in the R Installation and Administration manual. As always, the Oracle R Distribution is available as a free download to anyone. Questions and comments are welcome on the Oracle R Forum.

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• Why doesn't Firefox cache my images and CSS

  - by Richard A

  I am using IIS7, I have already set up the following. But when I run Firefox it seems not to cache any of my images even with "remember history" set. <?xml version="1.0" encoding="UTF-8"?> <configuration> <system.webServer> <staticContent> <clientCache cacheControlCustom="public" cacheControlMode="UseMaxAge" cacheControlMaxAge="7.00:00:00" /> </staticContent> </system.webServer> </configuration> However when I use Firebug it still points to Firefox not caching images and CSS: public,max-age=604800 Content-Type text/css Content-Encoding gzip Last-Modified Mon, 27 Jun 2011 03:53:22 GMT Accept-Ranges bytes Etag "507968c27d34cc1:0" Vary Accept-Encoding Server Microsoft-IIS/7.5 X-Powered-By ASP.NET Date Mon, 27 Jun 2011 13:06:41 GMT Content-Length 5067 Request Headersview source Host www.xx.com User-Agent Mozilla/5.0 (Windows NT 6.1; rv:2.0.1) Gecko/20100101 Firefox/4.0.1 Accept text/css,*/*;q=0.1 Accept-Language en-us,en;q=0.5 Accept-Encoding gzip, deflate Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7 Keep-Alive 115 Connection keep-alive Referer http://www.xx.com/ Cookie __utma=62996397.135679654.1309106351.1309159743.1309164158.8; __utmz=62996397.1309106351.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none); __utmc=62996397

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• Collision and Graphics integration

  - by Shlomi Atia

  I'm a little confused about the integration between collision and graphics. They both need to share the same position in the world. The most obvious choice is the center of the entity, which is good for bounding volumes and fixed sized sprites. However, for characters with variable height size sprites like this: http://gamemedia.wcgame.ru/data/2011-07-17/game-sprite-sheet.jpg This is no longer good. The character won't align to the ground if I'll draw it from the center. I can just make the sprites the same height, but it will be a waste of memory (the largest sprite is 4 times larger then the smallest one). Even then, this is not an option at all with skeletal sprites like this one: http://user-generated-content.java-gaming.org/img-vault/212a171fc1ebb27ab77608fb9b2dd9bd9205361ce6300b21a7f8d06d025fbbd8.png It seems that the graphics need to be drawn from the ground for characters, but not for other images such as scenery and obstacles. The only solution I could think of was having another position called draw-position, which is the entity center for images, and is the the bottom of the collision volume for characters. Then when I draw relative to that position, it should work properly. I haven't found any references for something like that, so I'm kinda insecure about it. Does anyone knows of a better approach for this problem? Thanks

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• Defining a function that is both a generator and recursive [on hold]

  - by user96454

  I am new to python, so this code might not necessarily be clean, it's just for learning purposes. I had the idea of writing this function that would display the tree down the specified path. Then, i added the global variable number_of_py to count how many python files were in that tree. That worked as well. Finally, i decided to turn the whole thing into a generator, but the recursion breaks. My understanding of generators is that once next() is called python just executes the body of the function and "yields" a value until we hit the end of the body. Can someone explain why this doesn't work? Thanks. import os from sys import argv script, path = argv number_of_py = 0 lines_of_code = 0 def list_files(directory, key=''): global number_of_py files = os.listdir(directory) for f in files: real_path = os.path.join(directory, f) if os.path.isdir(real_path): list_files(real_path, key=key+' ') else: if real_path.split('.')[-1] == 'py': number_of_py += 1 with open(real_path) as g: yield len(g.read()) print key+real_path for i in list_files(argv[1]): lines_of_code += i print 'total number of lines of code: %d' % lines_of_code print 'total number of py files: %d' % number_of_py

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• c++ How to use angular velocity that derived from inertia and force(torque) in 3d

  - by user1217203

  I am relatively new to game development. May my terminology and description are not appropriate. Please excuse my poor phrasing and help me by giving advice on how to question better if this question seems less fitting. I really appreciate your efforts. Hi. I am having hard time interpreting the set of values I have. I have inertia and force(torque) in terms of x y z. FYI I used x and y coordinates as my ground, flat coordinates and z as my up/down. I am assuming that since f = ma, that angular acceleration must be a = f / m. So I divide my torque by inertia. Then I add those x y z values to my angular velocity variable's x y z. However these x y z values confuse me. Don't I need angle/sec or radian/sec sort of values in order to apply rotation? The x y z values I have seemed to not say anything about radians or angular movement. Question : If I have ( 1, 2, 3 ) or any ( x, y, z ) as my angular velocity, how do I actually apply it as angular movement? FYI Here I am pasting my code : float mass = 100; float devidedMass = 1.0/12 * mass; Vec3 innertia( devidedMass* (_box._size.z*_box._size.z + _box._size.x*_box._size.x), devidedMass* (_box._size.y*_box._size.y + _box._size.x*_box._size.x), devidedMass* (_box._size.y*_box._size.y + _box._size.z*_box._size.z )); box._angAccel += forceAng/innertia; box._angVelo += box._angAccel; box._angAccel.allZero(); source of my inertia calculation http://www.health.uottawa.ca/biomech/courses/apa4311/solids.pdf

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• Application Scope v's Static - Not Quite the same

  - by Duncan Mills

  An interesting question came up today which, innocent as it sounded, needed a second or two to consider. What's the difference between storing say a Map of reference information as a Static as opposed to storing the same map as an application scoped variable in JSF?  From the perspective of the web application itself there seems to be no functional difference, in both cases, the information is confined to the current JVM and potentially visible to your app code (note that Application Scope is not magically propagated across a cluster, you would need a separate instance on each VM). To my mind the primary consideration here is a matter of leakage. A static will be (potentially) visible to everything running within the same VM (OK this depends on which class-loader was used but let's keep this simple), and this includes your model code and indeed other web applications running in the same container. An Application Scoped object, in JSF terms, is much more ring-fenced and is only visible to the Web app itself, not other web apps running on the same server and not directly to the business model layer if that is running in the same VM. So given that I'm a big fan of coding applications to say what I mean, then using Application Scope appeals because it explicitly states how I expect the data to be used and a provides a more explicit statement about visibility and indeed dependency as I'd generally explicitly inject it where it is needed.  Alternative viewpoints / thoughts are, as ever, welcomed...

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• Algorithmic problem - quickly finding all #'s where value %x is some given value

  - by Steve B.

  Problem I'm trying to solve, apologies in advance for the length: Given a large number of stored records, each with a unique (String) field S. I'd like to be able to find through an indexed query all records where Hash(S) % N == K for any arbitrary N, K (e.g. given a million strings, find all strings where HashCode(s) % 17 = 5. Is there some way of memoizing this so that we can quickly answer any question of this form without doing the % on every value? The motivation for this is a system of N distributed nodes, where each record has to be assigned to at least one node. The nodes are numbered 0 - (K-1) , and each node has to load up all of the records that match it's number: If we have 3 nodes Node 0 loads all records where Hash % 3 ==0 Node 1 loads all records where Hash % 3 ==1 Node 2 loads all records where Hash % 3 ==2 adding a 4th node, obviously all the assignments have to be recomputed - Node 0 loads all records where Hash % 4 ==0 ... etc I'd like to easily find these records through an indexed query without having to compute the mod individually. The best I've been able to come up with so far: If we take the prime factors of N (p1 * p2 * ... ) if N % M == I then p % M == I % p for all of N's prime factors e.g. 10 nodes : N % 10 == 6 then N % 2 = 0 == 6 %2 N % 5 = 1 == 6 %5 so storing an array of the "%" of N for the first "reasonable" number of primes for my data set should be helpful. For example in the above example we store the hash and the primes HASH PRIMES (array of %2, %3, %5, %7, ... ]) 16 [0 1 1 2 .. ] so looking for N%10 == 6 is equivalent to looking for all values where array[1]==1 and array[2] == 1. However, this breaks at the first prime larger than the highest number I'm storing in the factor table. Is there a better way?

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• Interpolation between two 3D points?

  - by meds

  I'm working with some splines which define a path a character follows (you can see a gameplay video here to get a better understanding of what's going on: http://www.youtube.com/watch?v=BndobjOiZ6g). Basically the characters 'forward' look direction is set to the 'forward' direction of the spline and when players tilt their phone left and right the character is strafed along its 'right' coordinate. The issue with this is (rather obviously) in performance, interpolating over a spline to find the nearest position and tangent relative to the player is an incredibly costly operation. To get by this I cache a finite number of positions in what I call 'SplineDetails', the class is as follows: public class SplineDetails { public SplineDetails() { Forward = Vector3.forward; Position = Vector3.one * float.MaxValue; Alpha = -1; } public float Alpha; // [0,1] measured along length of spline where 0 is the initial point and 1 is the end point of the spline public Vector3 Position; // the point of the spline at this alpha public Vector3 Forward; // the forward tangent of the spline at this alpha } I populate this with say 30 coordinates and I can give a rough estimate of a coordinate and 'forward' based on a position past in. It's not as accurate but it's much faster. But now I'd like to make the system work better by estimating positions and 'forward' directions by interpolating between two of the cached points though I'm stuck trying to figure out some logic. My first problem is, how can I determine between which two points the object is? Given each point can be placed at different intervals along the spline it could mean that two points in front or behind the object can be closer to the object. The other problem is to figure out the proportion between the two paths it's between, i.e. if there is a point a at coordinate (0,0,0) and point b at coordinate (1,0,0) if the object is at position (0.5,0,0) then the result it should give is '0.5' (as it is equal distance away from point a and point b). That's a simple example, but what if the object is at coordinate (0.5,3,0) for example?

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• Thematic map contd.

  - by jsharma

  The previous post (creating a thematic map) described the use of an advanced style (color ranged-bucket style). The bucket style definition object has an attribute ('classification') which specifies the data classification scheme to use. It's values can be one of {'equal', 'quantile', 'logarithmic', 'custom'}. We use logarithmic in the previous example. Here we'll describe how to use a custom algorithm for classification. Specifically the Jenks Natural Breaks algorithm. We'll use the Javascript implementation in geostats.js The sample code above needs a few changes which are listed below. Include the geostats.js file after or before including oraclemapsv2.js <script src="geostats.js"></script> Modify the bucket style definition to use custom classification Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}    bucketStyleDef = {       numClasses : colorSeries[colorName].classes,       classification: 'custom', //'logarithmic',  // use a logarithmic scale       algorithm: jenksFromGeostats,       styles: theStyles,       gradient:  useGradient? 'linear' : 'off'     }; The function, which implements the custom classification scheme, is specified as the algorithm attribute value. It must accept two input parameters, an array of OM.feature and the name of the feature attribute (e.g. TOTPOP) to use in the classification, and must return an array of buckets (i.e. an array of or OM.style.Bucket  or OM.style.RangedBucket in this case). However the algorithm also needs to know the number of classes (i.e. the number of buckets to create). So we use a global to pass that info in. (Note: This bug/oversight will be fixed and the custom algorithm will be passed 3 parameters: the features array, attribute name, and number of classes). So createBucketColorStyle() has the following changes Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} var numClasses ; function createBucketColorStyle( colorName, colorSeries, rangeName, useGradient) {    var theBucketStyle;    var bucketStyleDef;    var theStyles = [];    //var numClasses ; numClasses = colorSeries[colorName].classes; ... and the function jenksFromGeostats is defined as Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} function jenksFromGeostats(featureArray, columnName) {    var items = [] ; // array of attribute values to be classified    $.each(featureArray, function(i, feature) {         items.push(parseFloat(feature.getAttributeValue(columnName)));    });    // create the geostats object    var theSeries = new geostats(items);    // call getJenks which returns an array of bounds    var theClasses = theSeries.getJenks(numClasses);    if(theClasses)    {     theClasses[theClasses.length-1]=parseFloat(theClasses[theClasses.length-1])+1;    }    else    {     alert(' empty result from getJenks');    }    var theBuckets = [], aBucket=null ;    for(var k=0; k<numClasses; k++)    {             aBucket = new OM.style.RangedBucket(             {low:parseFloat(theClasses[k]),               high:parseFloat(theClasses[k+1])             });             theBuckets.push(aBucket);     }     return theBuckets; } A screenshot of the resulting map with 5 classes is shown below. It is also possible to simply create the buckets and supply them when defining the Bucket style instead of specifying the function (algorithm). In that case the bucket style definition object would be    bucketStyleDef = {      numClasses : colorSeries[colorName].classes,      classification: 'custom',        buckets: theBuckets, //since we are supplying all the buckets      styles: theStyles,      gradient:  useGradient? 'linear' : 'off'    };

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• Frame Independent Movement

  - by ShrimpCrackers

  I've read two other threads here on movement: Time based movement Vs Frame rate based movement?, and Fixed time step vs Variable time step but I think I'm lacking a basic understanding of frame independent movement because I don't understand what either of those threads are talking about. I'm following along with lazyfoo's SDL tutorials and came upon the frame independent lesson. http://lazyfoo.net/SDL_tutorials/lesson32/index.php I'm not sure what the movement part of the code is trying to say but I think it's this (please correct me if I'm wrong): In order to have frame independent movement, we need to find out how far an object (ex. sprite) moves within a certain time frame, for example 1 second. If the dot moves at 200 pixels per second, then I need to calculate how much it moves within that second by multiplying 200 pps by 1/1000 of a second. Is that right? The lesson says: "velocity in pixels per second * time since last frame in seconds. So if the program runs at 200 frames per second: 200 pps * 1/200 seconds = 1 pixel" But...I thought we were multiplying 200 pps by 1/1000th of a second. What is this business with frames per second? I'd appreciate if someone could give me a little bit more detailed explanation as to how frame independent movement works. Thank you.

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• How do references work in R?

  - by djechlin

  I'm finding R confusing because it has such a different notion of reference than I am used to in languages like C, Java, Javascript... Ruby, Python, C++, well, pretty much any language I have ever programmed in ever. So one thing I've noticed is variable names are not irrelevant when passing them to something else. The reference can be part of the data. e.g. per this tutorial a <- factor(c("A","A","B","A","B","B","C","A","C")) results <- table(a) Leads to $a showing up as an attribute as $dimnames$a. We've also witnessed that calling a function like a <- foo(alpha=1, beta=2) can create attributes in a of names alpha and beta, or it can assign or otherwise compute on 1 and 2 to properties already existing. (Not that there's a computer science distinction here - it just doesn't really happen in something like Javascript, unless you want to emulate it by passing in the object and use key=value there.) Functions like names(...) return lvalues that will affect the input of them. And the one that most got me is this. x <- c(3, 5, 1, 10, 12, 6) y = x[x <= 5] x[y] <- 0 is different from x <- c(3, 5, 1, 10, 12, 6) x[x <= 5] <- 0 Color me confused. Is there a consistent theory for what's going on here?

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• Is it considered poor programming to do this with xna components?

  - by Rob

  I created my own Menu System that is event driven. In order to have a loading screen and multithreaded loading to work, I devised this sort of implementation: //Let's check if the game is done loading. if (_game != null) { _gameLoaded = _game.DoneLoading; } //This means the game is loading still, //therefore the loading screen should be active. if (!_gameLoaded && _gameActive) { _gameScreenList[2].UpdateMenu(); } //The loading screen was selected. if (_gameScreenList[2].CurrentState == GameScreen.State.Shown && !_gameActive) { Components.Add(_game = new ParadoxGame(this)); _game.Initialize(); //Initializes the Game so that the loading can begin. _gameActive = true; } In the XNA Game Component that contains the actual game, in the LoadContent method I simply created a new Thread that calls another method ThreadLoad that has all the actual loading. I also have a boolean variable called DoneLoading in the XNA Game Component that is set to true at the end of the ThreadLoad. I am wondering if this is a poor implementation.

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• How can I get cross-browser consistent behavior for TR heights within a table with a set height? [migrated]

  - by Dan

  I have an arbitrary number of tables with an arbitrary number of rows in each, and all tables are the same height. My initial approach was to just set the overall height of the table and hope the rows were smart enough to distribute themselves appropriately. That's not the case. I have 4 different behaviors going on with 4 browsers, but I need them to all render at the very least in a similar way. Safari & Chrome (WebKit): All rows are equal height, creating scroll bars as needed and fitting within table height. Firefox: All rows are the height necessary to fit their content, with the remaining rows overflowing out of the table. Additionally, If the content of the rows does not take up all of the height, only the part of the table with content in it takes the background (though it seems, through use of Firebug, that the actual table [and TR] extend to the bottom of the proper table height). IE: All rows are the height necessary to fit their content, with the remaining rows overflowing out of the table. Obviously this only includes one version of each browser and additional variation would likely appear with more being tested. Ideally, a solution where the browser renders TRs with less content smaller than those with larger content, while still using scrolling within the variable height TRs when the overall height of the table is not enough would be optimum. I could potentially see a solution to achieve that with JS, but can it be done with CSS? Or, if not, can the behavior that WebKit displays be made to work across the browsers? Thanks! PS: Example can be found here.

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