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• What's wrong with my wireless?

  - by dazzle

  I am having issues with my wireless connection. My connection is constantly disconnecting, then attempting to reconnect, reconnecting momentarily, then disconnecting etc. on times scales that range from seconds to minutes. In the meantime, needless to say I'm having significant packet loss. I'm running Ubuntu 14.04 64bit, updated and upgraded to today. Here is my card and driver: delta@sager:~$ lspci -vq | grep -i wireless -B 1 -A 5 04:00.0 Network controller: Intel Corporation Wireless 7260 (rev 73) Subsystem: Intel Corporation Dual Band Wireless-AC 7260 Flags: bus master, fast devsel, latency 0, IRQ 47 Memory at f7d00000 (64-bit, non-prefetchable) [size=8K] Capabilities: Kernel driver in use: iwlwifi Here is my kernel: delta@sager:~$ uname -r 3.13.0-34-generic None of the other machines on my home network are having these issues. Windows Vista is networking without issue for goodness sake ;-) Here is a small clipping from the output of dmesg. As you can see, I am getting a cfg80211 message of some sort over and over again (FYI, I've replaced my MAC address with a series of dashes, so anytime there is a ---------------, that was where the MAC address was: [ 1881.739161] wlan1: authenticate with --------------- [ 1881.741561] wlan1: send auth to --------------- (try 1/3) [ 1881.743440] wlan1: authenticated [ 1881.746027] wlan1: associate with --------------- (try 1/3) [ 1881.749244] wlan1: RX AssocResp from --------------- (capab=0x411 status=0 aid=4) [ 1881.754727] wlan1: associated [ 1881.754827] cfg80211: Calling CRDA for country: US [ 1881.761552] cfg80211: Regulatory domain changed to country: US [ 1881.761559] cfg80211: (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp) [ 1881.761564] cfg80211: (2402000 KHz - 2472000 KHz @ 40000 KHz), (300 mBi, 2700 mBm) [ 1881.761568] cfg80211: (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 1700 mBm) [ 1881.761571] cfg80211: (5250000 KHz - 5330000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) [ 1881.761574] cfg80211: (5490000 KHz - 5600000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) [ 1881.761577] cfg80211: (5650000 KHz - 5710000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) [ 1881.761580] cfg80211: (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 3000 mBm) [ 1881.761584] cfg80211: (57240000 KHz - 63720000 KHz @ 2160000 KHz), (N/A, 4000 mBm) [ 1882.391038] cfg80211: Calling CRDA to update world regulatory domain [ 1882.396254] cfg80211: World regulatory domain updated: [ 1882.396260] cfg80211: (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp) [ 1882.396265] cfg80211: (2402000 KHz - 2472000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) [ 1882.396268] cfg80211: (2457000 KHz - 2482000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) [ 1882.396271] cfg80211: (2474000 KHz - 2494000 KHz @ 20000 KHz), (300 mBi, 2000 mBm) [ 1882.396274] cfg80211: (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) [ 1882.396277] cfg80211: (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) [ 1886.148252] wlan1: authenticate with --------------- [ 1886.150005] wlan1: send auth to --------------- (try 1/3) [ 1886.151807] wlan1: authenticated [ 1886.154847] wlan1: associate with --------------- (try 1/3) [ 1886.158147] wlan1: RX AssocResp from --------------- (capab=0x411 status=0 aid=4) [ 1886.163464] wlan1: associated [ 1886.163520] wlan1: Limiting TX power to 30 (30 - 0) dBm as advertised by --------------- [ 1886.163588] cfg80211: Calling CRDA for country: US [ 1886.170500] cfg80211: Regulatory domain changed to country: US [ 1886.170508] cfg80211: (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp) [ 1886.170513] cfg80211: (2402000 KHz - 2472000 KHz @ 40000 KHz), (300 mBi, 2700 mBm) [ 1886.170517] cfg80211: (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 1700 mBm) [ 1886.170520] cfg80211: (5250000 KHz - 5330000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) [ 1886.170523] cfg80211: (5490000 KHz - 5600000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) [ 1886.170526] cfg80211: (5650000 KHz - 5710000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) [ 1886.170529] cfg80211: (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 3000 mBm) [ 1886.170533] cfg80211: (57240000 KHz - 63720000 KHz @ 2160000 KHz), (N/A, 4000 mBm) [ 1887.200197] cfg80211: Calling CRDA to update world regulatory domain [ 1887.203655] cfg80211: World regulatory domain updated: [ 1887.203659] cfg80211: (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp) [ 1887.203662] cfg80211: (2402000 KHz - 2472000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) [ 1887.203664] cfg80211: (2457000 KHz - 2482000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) [ 1887.203666] cfg80211: (2474000 KHz - 2494000 KHz @ 20000 KHz), (300 mBi, 2000 mBm) [ 1887.203668] cfg80211: (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) [ 1887.203670] cfg80211: (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) I've poked around on AskUbuntu, and have not found any adequate solutions; have also found similar threads that were left unanswered. Any advice/experience/threads I might be able to pull on would be greatly appreciated. In your opinion, is this a kernel issue, hardware issue, etc.? Thanks in advance. EDIT: chili, here's the output of iwconfig: delta@sager:~$ iwconfig wlan1 IEEE 802.11abg ESSID:"LANbeforetime" Mode:Managed Frequency:2.412 GHz Access Point: ----------- Bit Rate=48 Mb/s Tx-Power=16 dBm Retry long limit:7 RTS thr:off Fragment thr:off Power Management:off Link Quality=44/70 Signal level=-66 dBm Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:80 Missed beacon:0 eth0 no wireless extensions. lo no wireless extensions.

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• Fast Data - Big Data's achilles heel

  - by thegreeneman

  At OOW 2013 in Mark Hurd and Thomas Kurian's keynote, they discussed Oracle's Fast Data software solution stack and discussed a number of customers deploying Oracle's Big Data / Fast Data solutions and in particular Oracle's NoSQL Database.  Since that time, there have been a large number of request seeking clarification on how the Fast Data software stack works together to deliver on the promise of real-time Big Data solutions.   Fast Data is a software solution stack that deals with one aspect of Big Data, high velocity.   The software in the Fast Data solution stack involves 3 key pieces and their integration:  Oracle Event Processing, Oracle Coherence, Oracle NoSQL Database.   All three of these technologies address a high throughput, low latency data management requirement.   Oracle Event Processing enables continuous query to filter the Big Data fire hose, enable intelligent chained events to real-time service invocation and augments the data stream to provide Big Data enrichment. Extended SQL syntax allows the definition of sliding windows of time to allow SQL statements to look for triggers on events like breach of weighted moving average on a real-time data stream.    Oracle Coherence is a distributed, grid caching solution which is used to provide very low latency access to cached data when the data is too big to fit into a single process, so it is spread around in a grid architecture to provide memory latency speed access.  It also has some special capabilities to deploy remote behavioral execution for "near data" processing.   The Oracle NoSQL Database is designed to ingest simple key-value data at a controlled throughput rate while providing data redundancy in a cluster to facilitate highly concurrent low latency reads.  For example, when large sensor networks are generating data that need to be captured while analysts are simultaneously extracting the data using range based queries for upstream analytics.  Another example might be storing cookies from user web sessions for ultra low latency user profile management, also leveraging that data using holistic MapReduce operations with your Hadoop cluster to do segmented site analysis.  Understand how NoSQL plays a critical role in Big Data capture and enrichment while simultaneously providing a low latency and scalable data management infrastructure thru clustered, always on, parallel processing in a shared nothing architecture. Learn how easily a NoSQL cluster can be deployed to provide essential services in industry specific Fast Data solutions. See these technologies work together in a demonstration highlighting the salient features of these Fast Data enabling technologies in a location based personalization service. The question then becomes how do these things work together to deliver an end to end Fast Data solution.  The answer is that while different applications will exhibit unique requirements that may drive the need for one or the other of these technologies, often when it comes to Big Data you may need to use them together.   You may have the need for the memory latencies of the Coherence cache, but just have too much data to cache, so you use a combination of Coherence and Oracle NoSQL to handle extreme speed cache overflow and retrieval.   Here is a great reference to how these two technologies are integrated and work together.  Coherence & Oracle NoSQL Database.   On the stream processing side, it is similar as with the Coherence case.  As your sliding windows get larger, holding all the data in the stream can become difficult and out of band data may need to be offloaded into persistent storage.  OEP needs an extreme speed database like Oracle NoSQL Database to help it continue to perform for the real time loop while dealing with persistent spill in the data stream.  Here is a great resource to learn more about how OEP and Oracle NoSQL Database are integrated and work together.  OEP & Oracle NoSQL Database.

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• What common interface would be appropriate for these game object classes?

  - by Jefffrey

  Question A component based system's goal is to solve the problems that derives from inheritance: for example the fact that some parts of the code (that are called components) are reused by very different classes that, hypothetically, would lie in a very different branch of the inheritance tree. That's a very nice concept, but I've found out that CBS is often hard to accomplish without using ugly hacks. Implementations of this system are often far from clean. But I don't want to discuss this any further. My question is: how can I solve the same problems a CBS try to solve with a very clean interface? (possibly with examples, there are a lot of abstract talks about the "perfect" design already). Context Here's an example I was going for before realizing I was just reinventing inheritance again: class Human { public: Position position; Movement movement; Sprite sprite; // other human specific components }; class Zombie { Position position; Movement movement; Sprite sprite; // other zombie specific components }; After writing that I realized I needed an interface, otherwise I would have needed N containers for N different types of objects (or to use boost::variant to gather them all together). So I've thought of polymorphism (move what systems do in a CBS design into class specific functions): class Entity { public: virtual void on_event(Event) {} // not pure virtual on purpose virtual void on_update(World) {} virtual void on_draw(Window) {} }; class Human : public Entity { private: Position position; Movement movement; Sprite sprite; public: virtual void on_event(Event) { ... } virtual void on_update(World) { ... } virtual void on_draw(Window) { ... } }; class Zombie : public Entity { private: Position position; Movement movement; Sprite sprite; public: virtual void on_event(Event) { ... } virtual void on_update(World) { ... } virtual void on_draw(Window) { ... } }; Which was nice, except for the fact that now the outside world would not even be able to know where a Human is positioned (it does not have access to its position member). That would be useful to track the player position for collision detection or if on_update the Zombie would want to track down its nearest human to move towards him. So I added const Position& get_position() const; to both the Zombie and Human classes. And then I realized that both functionality were shared, so it should have gone to the common base class: Entity. Do you notice anything? Yes, with that methodology I would have a god Entity class full of common functionality (which is the thing I was trying to avoid in the first place). Meaning of "hacks" in the implementation I'm referring to I'm talking about the implementations that defines Entities as simple IDs to which components are dynamically attached. Their implementation can vary from C-stylish: int last_id; Position* positions[MAX_ENTITIES]; Movement* movements[MAX_ENTITIES]; Where positions[i], movements[i], component[i], ... make up the entity. Or to more C++-style: int last_id; std::map<int, Position> positions; std::map<int, Movement> movements; From which systems can detect if an entity/id can have attached components.

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• glm matrix conversion for DirectX

  - by niktehpui

  For on of the coursework specification I need to work with DirectX, so I tried to implement a DirectX Renderer in my small cross-platform framework (to have it optionally available for Windows). Since I want to stick to my dependencies I want use glm for vector/matrix/quaternions math. The vectors seem to be fully compatible with DirectX, but the glm::mat4 is not working properly in DirectX Effects Framework. I assumed the reason is that DirectX uses row majors layouts and OpenGL column majors (although if I remember right internally in HLSL DX uses column major as well), so I transposed the matrix, but I still get no proper results compared to using XNA-Math. XNA-Version of the code (works): XMMATRIX world = XMMatrixIdentity(); XMMATRIX view = XMMatrixLookAtLH(XMVectorSet(5.0, 5.0, 5.0, 1.0f), XMVectorZero(), XMVectorSet(0.0f, 1.0f, 0.0f, 0.0f)); XMMATRIX proj = XMMatrixPerspectiveFovLH(0.25f*3.14f, 1.25f, 1.0f, 1000.0f); XMMATRIX worldViewProj = world*view*proj; m_fxWorldViewProj->SetMatrix(reinterpret_cast<float*>(&worldViewProj)); This works flawlessly and displays the expected colored cube. GLM-Version (does not work): glm::mat4 world(1.0f); glm::mat4 view = glm::lookAt(glm::vec3(5.0f, 5.0f, 5.0f), glm::vec3(0.0f, 0.0f, 0.0f), glm::vec3(0.0f, 1.0f, 0.0f)); glm::mat4 proj = glm::perspective(0.25f*3.14f, 1.25f, 1.0f, 1000.0f); glm::mat4 worldViewProj = glm::transpose(world*view*proj); m_fxWorldViewProj->SetMatrix(glm::value_ptr(worldViewProj)); Displays nothing, screen stays black. I really would like to stick to glm on all platforms.

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• Robot Simulation in Java

  - by Eddy Freeman

  Hi Guys, I am doing a project concerning robot simulation and i need help. I have to simulate the activities of a robot in a warehouse. I am using mindstorm robots and lego's for the warehouse. The point here is i have to simulate all the activities of the robot on a Java GUI. That is whenever the robot is moving, users have to see it on the GUI a moving object which represents the robot. When the roads/rails/crossings of the warehouse changes it must also be changed on the screen. The whole project is i have to simulate whatever the robot is doing in the warehouse in real-time. Everything must happen in real-time I am asking which libraries in Java i can use to do this simulations in real-time and if someone can also point me to any site for good information. Am asking for libraries in Java that i can use to visualize the simulation in real-time. All suggestions are welcome. Thanks for your help.

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• Newbie python error in regards to import

  - by TylerW

  Hello. I'm a python newbie and starting out with using the Bottle web framework on Google App Engine. I've been messing with the super small, super easy Hello World sample and have already ran into problems. Heh. I finally got the code to work with this... import bottle from bottle import route from google.appengine.ext.webapp import util @route('/hello') def hello(): return "Hello World!" util.run_wsgi_app(bottle.default_app()) My question is, I thought I could just go 'import bottle' without the second line. But if I take the second line out, I get a NameError. Or if I do 'from bottle import *', I still get the error. bottle is just a single file called 'bottle.py' in my site's root directory. So neither of these work.... import bottle from google.appengine.ext.webapp import util @route('/hello') def hello(): return "Hello World!" util.run_wsgi_app(bottle.default_app()) Or from bottle import * from google.appengine.ext.webapp import util @route('/hello') def hello(): return "Hello World!" util.run_wsgi_app(bottle.default_app()) The error message I get is... Traceback (most recent call last): File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 3180, in _HandleRequest self._Dispatch(dispatcher, self.rfile, outfile, env_dict) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 3123, in _Dispatch base_env_dict=env_dict) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 515, in Dispatch base_env_dict=base_env_dict) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 2382, in Dispatch self._module_dict) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 2292, in ExecuteCGI reset_modules = exec_script(handler_path, cgi_path, hook) File "/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/google/appengine/tools/dev_appserver.py", line 2188, in ExecuteOrImportScript exec module_code in script_module.dict File "/Users/tyler/Dropbox/sites/dietgrid/code2.py", line 4, in @route('/hello') NameError: name 'route' is not defined So am I wrong in thinking it should be able to work the other ways or no?

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• Is there an easy way to get the Scala REPL to reload a class or package?

  - by Rex Kerr

  I almost always have a Scala REPL session or two open, which makes it very easy to give Java or Scala classes a quick test. But if I change a class and recompile it, the REPL continues with the old one loaded. Is there a way to get it to reload the class, rather than having to restart the REPL? Just to give a concrete example, suppose we have the file Test.scala: object Test { def hello = "Hello World" } We compile it and start the REPL: ~/pkg/scala-2.8.0.Beta1-prerelease$ bin/scala Welcome to Scala version 2.8.0.Beta1-prerelease (Java HotSpot(TM) Server VM, Java 1.6.0_16). Type in expressions to have them evaluated. Type :help for more information. scala> Test.hello res0: java.lang.String = Hello World Then we change the source file to object Test { def hello = "Hello World" def goodbye = "Goodbye, Cruel World" } but we can't use it: scala> Test.goodbye <console>:5: error: value goodbye is not a member of object Test Test.goodbye ^ scala> import Test; <console>:1: error: '.' expected but ';' found. import Test;

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• Practical Scheme Programming

  - by Ixmatus

  It's been a few months since I've touched Scheme and decided to implement a command line income partitioner using Scheme. My initial implementation used plain recursion over the continuation, but I figured a continuation would be more appropriate to this type of program. I would appreciate it if anyone (more skilled with Scheme than I) could take a look at this and suggest improvements. I'm that the multiple (display... lines is an ideal opportunity to use a macro as well (I just haven't gotten to macros yet). (define (ab-income) (call/cc (lambda (cc) (let ((out (display "Income: ")) (income (string->number (read-line)))) (cond ((<= income 600) (display (format "Please enter an amount greater than $600.00~n~n")) (cc (ab-income))) (else (let ((bills (* (/ 30 100) income)) (taxes (* (/ 20 100) income)) (savings (* (/ 10 100) income)) (checking (* (/ 40 100) income))) (display (format "~nDeduct for bills:---------------------- $~a~n" (real->decimal-string bills 2))) (display (format "Deduct for taxes:---------------------- $~a~n" (real->decimal-string taxes 2))) (display (format "Deduct for savings:-------------------- $~a~n" (real->decimal-string savings 2))) (display (format "Remainder for checking:---------------- $~a~n" (real->decimal-string checking 2)))))))))) Invoking (ab-income) asks for input and if anything below 600 is provided it (from my understanding) returns (ab-income) at the current-continuation. My first implementation (as I said earlier) used plain-jane recursion. It wasn't bad at all either but I figured every return call to (ab-income) if the value was below 600 kept expanding the function. (please correct me if that apprehension is incorrect!)

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• How to determine which inheriting class is using an abstract class' methods.

  - by Kin

  In my console application have an abstract Factory class "Listener" which contains code for listening and accepting connections, and spawning client classes. This class is inherited by two more classes (WorldListener, and MasterListener) that contain more protocol specific overrides and functions. I also have a helper class (ConsoleWrapper) which encapsulates and extends System.Console, containing methods for writing to console info on what is happening to instances of the WorldListener and MasterListener. I need a way to determine in the abstract ListenerClass which Inheriting class is calling its methods. Any help with this problem would be greatly appreciated! I am stumped :X Simplified example of what I am trying to do. abstract class Listener { public void DoSomething() { if(inheriting class == WorldListener) ConsoleWrapper.WorldWrite("Did something!"); if(inheriting class == MasterListener) ConsoleWrapper.MasterWrite("Did something!"); } } public static ConsoleWrapper { public void WorldWrite(string input) { System.Console.WriteLine("[World] {0}", input); } } public class WorldListener : Listener { public void DoSomethingSpecific() { ConsoleWrapper.WorldWrite("I did something specific!"); } } public void Main() { new WorldListener(); new MasterListener(); } Expected output [World] Did something! [World] I did something specific! [Master] Did something! [World] I did something specific!

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• Problem inserting android.text.format.Time.toMillis value into SQLite DB on droid

  - by schusselig

  I'm writing an app for Android OS, and I need to store some time values in the SQLite DB. I have been using android.text.format.Time to store the time values in the app, and then inserting the values as millis into the DB as REAL values. On the SDK emulator, everything works perfectly. On the sole phone I've had the opportunity to test my app (so far), my duration code doesn't work as expected. Some relevant code: private static final String DATABASE_CREATE = "create table " + DATABASE_TABLE + " (" + KEY_ROWID + " integer primary key autoincrement, " + KEY_START + " REAL, " + KEY_STOP + " REAL, " + KEY_DUR + " REAL );"; ... private SQLiteDatabase mDb; ContentValues timerValues = new ContentValues(); ... timerValues.put(KEY_START, stime.toMillis(false)); timerValues.put(KEY_STOP, etime.toMillis(false)); timerValues.put(KEY_DURATION, stime.toMillis(false)-etime.toMillis(false)); int result = mDb.insert(DATABASE_TABLE, null, timerValues); I pull this data from two separate functions with slightly different bits of code, both using Time.set(long millis), both giving incorrect results: The start and stop values come back correct, but the duration comes out 17 hours too large. Am I missing something about calculating durations or does this just seem like there's something "special" about this particular droid? I'll have another droid to test on Monday, but any ideas are appreciated.

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• Defining Light Coordinates

  - by Zachary

  I took a Computer Graphics exam a couple of days ago which had extra credit question like the following: A light can be defined in one of two ways. It can be defined in world coordinates, e.g. a street light, or in the viewer (eye coordinates), e.g., a head-lamp worn by a miner. In either case the viewpoint can freely change. Describe how the light should be transformed different in these two cases. Since I won't get to see the results of this until after spring break, I thought I would ask here. It seems like the analogies being used are misleading - could you not define a light source that is located at the viewers eye in world coordinates just as well as you could in eye coordinates? I've been doing some research on how OpenGL handles light, and it seems as though it always uses eye coordinates - the ModelView matrix would be applied to any light in world coordinates. In that case the answer may just be that you would have to transform light defined in world coordinates into eye coordinates using something like the ModelView matrix, while light defined in eye coordinates would only need to be transformed by the projection matrix. Then again I could be totally under thinking (or over thinking this). Another thought I had is that it determines which way you render shadows, but that has more to do with the location of the light and its type (point, directional, emission, etc) than what coordinates it is represented in. Any ideas?

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• Small-o(n^2) implementation of Polynomial Multiplication

  - by AlanTuring

  I'm having a little trouble with this problem that is listed at the back of my book, i'm currently in the middle of test prep but i can't seem to locate anything regarding this in the book. Anyone got an idea? A real polynomial of degree n is a function of the form f(x)=a(n)x^n+?+a1x+a0, where an,…,a1,a0 are real numbers. In computational situations, such a polynomial is represented by a sequence of its coefficients (a0,a1,…,an). Assuming that any two real numbers can be added/multiplied in O(1) time, design an o(n^2)-time algorithm to compute, given two real polynomials f(x) and g(x) both of degree n, the product h(x)=f(x)g(x). Your algorithm should **not** be based on the Fast Fourier Transform (FFT) technique. Please note it needs to be small-o(n^2), which means it complexity must be sub-quadratic. The obvious solution that i have been finding is indeed the FFT, but of course i can't use that. There is another method that i have found called convolution, where if you take polynomial A to be a signal and polynomial B to be a filter. A passed through B yields a shifted signal that has been "smoothed" by A and the resultant is A*B. This is supposed to work in O(n log n) time. Of course i am completely unsure of implementation. If anyone has any ideas of how to achieve a small-o(n^2) implementation please do share, thanks.

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• Simple in-place discrete fourier transform ( DFT )

  - by Adam

  I'm writing a very simple in-place DFT. I am using the formula shown here: http://en.wikipedia.org/wiki/Discrete_Fourier_transform#Definition along with Euler's formula to avoid having to use a complex number class just for this. So far I have this: private void fft(double[] data) { double[] real = new double[256]; double[] imag = new double[256]; double pi_div_128 = -1 * Math.PI / 128; for (int k = 0; k < 256; k++) { for (int n = 0; n < 256; n++) { real[k] += data[k] * Math.Cos(pi_div_128 * k * n); imag[k] += data[k] * Math.Sin(pi_div_128 * k * n); } data[k] = Math.Sqrt(real[k] * real[k] + imag[k] * imag[k]); } } But the Math.Cos and Math.Sin terms eventually go both positive and negative, so as I'm adding those terms multiplied with data[k], they cancel out and I just get some obscenely small value. I see how it is happening, but I can't make sense of how my code is perhaps mis-representing the mathematics. Any help is appreciated. FYI, I do have to write my own, I realize I can get off-the shelf FFT's.

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• Linear regression confidence intervals in SQL

  - by Matt Howells

  I'm using some fairly straight-forward SQL code to calculate the coefficients of regression (intercept and slope) of some (x,y) data points, using least-squares. This gives me a nice best-fit line through the data. However we would like to be able to see the 95% and 5% confidence intervals for the line of best-fit (the curves below). What these mean is that the true line has 95% probability of being below the upper curve and 95% probability of being above the lower curve. How can I calculate these curves? I have already read wikipedia etc. and done some googling but I haven't found understandable mathematical equations to be able to calculate this. Edit: here is the essence of what I have right now. --sample data create table #lr (x real not null, y real not null) insert into #lr values (0,1) insert into #lr values (4,9) insert into #lr values (2,5) insert into #lr values (3,7) declare @slope real declare @intercept real --calculate slope and intercept select @slope = ((count(*) * sum(x*y)) - (sum(x)*sum(y)))/ ((count(*) * sum(Power(x,2)))-Power(Sum(x),2)), @intercept = avg(y) - ((count(*) * sum(x*y)) - (sum(x)*sum(y)))/ ((count(*) * sum(Power(x,2)))-Power(Sum(x),2)) * avg(x) from #lr Thank you in advance.

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• Access denied when trying to access my database.

  - by Sergio Tapia

  Here's my code: <html> <head> </head> <body> <?php $user = mysql_real_escape_string($_GET["u"]); $pass = mysql_real_escape_string($_GET["p"]); $query = "SELECT * FROM usario WHERE username = '$user' AND password = '$pass'"; mysql_connect(localhost, "root", ""); @mysql_select_db("multas") or die( "Unable to select database"); $result=mysql_query($query); if(mysql_numrows($result) > 0){ echo 'si'; } ?> </body> </html> And here's the error I get when I try to run it Warning: mysql_real_escape_string() [function.mysql-real-escape-string]: Access denied for user 'ODBC'@'localhost' (using password: NO) in C:\xampp\htdocs\useraccess.php on line 7 Warning: mysql_real_escape_string() [function.mysql-real-escape-string]: A link to the server could not be established in C:\xampp\htdocs\useraccess.php on line 7 Warning: mysql_real_escape_string() [function.mysql-real-escape-string]: Access denied for user 'ODBC'@'localhost' (using password: NO) in C:\xampp\htdocs\useraccess.php on line 8 Warning: mysql_real_escape_string() [function.mysql-real-escape-string]: A link to the server could not be established in C:\xampp\htdocs\useraccess.php on line 8 Warning: mysql_numrows() expects parameter 1 to be resource, boolean given in C:\xampp\htdocs\useraccess.php on line 16

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• C# using the "this" keyword in this situation?

  - by Alex

  Hi, I've completed a OOP course assignment where I design and code a Complex Number class. For extra credit, I can do the following: Add two complex numbers. The function will take one complex number object as a parameter and return a complex number object. When adding two complex numbers, the real part of the calling object is added to the real part of the complex number object passed as a parameter, and the imaginary part of the calling object is added to the imaginary part of the complex number object passed as a parameter. Subtract two complex numbers. The function will take one complex number object as a parameter and return a complex number object. When subtracting two complex numbers, the real part of the complex number object passed as a parameter is subtracted from the real part of the calling object, and the imaginary part of the complex number object passed as a parameter is subtracted from the imaginary part of the calling object. I have coded this up, and I used the this keyword to denote the current instance of the class, the code for my add method is below, and my subtract method looks similar: public ComplexNumber Add(ComplexNumber c) { double realPartAdder = c.GetRealPart(); double complexPartAdder = c.GetComplexPart(); double realPartCaller = this.GetRealPart(); double complexPartCaller = this.GetComplexPart(); double finalRealPart = realPartCaller + realPartAdder; double finalComplexPart = complexPartCaller + complexPartAdder; ComplexNumber summedComplex = new ComplexNumber(finalRealPart, finalComplexPart); return summedComplex; } My question is: Did I do this correctly and with good style? (using the this keyword)?

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• Cannot run Python script on Windows with output redirected??

  - by Wai Yip Tung

  This is running on Windows 7 (64 bit), Python 2.6 with Win32 Extensions for Python. I have a simple script that just print "hello world". I can launch it with python hello.py. In this case I can redirect the output to a file. But if I run it by just typing hello.py on the command line and redirect the output, I get an exception. C:> python hello.py hello world C:> python hello.py >output C:> type output hello world C:> hello.py hello world C:> hello.py >output close failed in file object destructor: Error in sys.excepthook: Original exception was: I think I first get this error after upgrading to Windows 7. I remember it should work in XP. I have seen people talking about this bug python-Bugs-1012692 | Can't pipe input to a python program. But that was long time ago. And it does not mention any solution. Have anyone experienced this? Anyone can help?

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• Apply PHP regex replace on a multi-line repeted pattern

  - by Hussain

  Let's say I have this input: I can haz a listz0rs! # 42 # 126 I can haz another list plox? # Hello, world! # Welcome! I want to split it so that each set of hash-started lines becomes a list: I can haz a listz0rs! <ul> <li>42</li> <li>126</li> </ul> I can haz another list plox? <ul> <li>Hello, world!</li> <li>Welcome!</li> </ul> If I run the input against the regex "/(?:(?:(?<=^# )(.*)$)+)/m", I get the following result: Array ( [0] => Array ( [0] => 42 ) Array ( [0] => 126 ) Array ( [0] => Hello, world! ) Array ( [0] => Welcome! ) ) This is fine and dandy, but it doesn't distinguish between the two different lists. I need a way to either make the quantifier return a concatenated string of all the occurrences, or, ideally, an array of all the occurrences. Idealy, this should be my output: Array ( [0] = Array ( [0] = 42 [1] = 126 ) Array ( [0] = Hello, world! [1] = Welcome! ) ) Is there any way of achieving this, and if not, is there a close alternative? Thanks in advance!

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• How to Inject code in c# method calls from a separate app

  - by Fusspawn

  I was curious if anyone knew of a way of monitoring a .Net application's runtime info (what method is being called and such) and injecting extra code to be run on certain methods from a separate running process. say i have two applications: app1.exe that for simplicity's sake could be class Program { static void Main(string[] args) { while(true){ Somefunc(); } } static void Somefunc() { Console.WriteLine("Hello World"); } } and I have a second application that I wish to be able to detect when Somefunc() from application 1 is running and inject its own code, class Program { static void Main(string[] args) { while(true){ if(App1.SomeFuncIsCalled) InjectCode(); } } static void InjectCode() { App1.Console.WriteLine("Hello World Injected"); } } So The result would be Application one would show Hello World Hello World Injected I understand its not going to be this simple ( By a long shot ) but I have no idea if it's even possible and if it is where to even start. Any suggestions ? I've seen similar done in java, But never in c#. EDIT: To clarify, the usage of this would be to add a plugin system to a .Net based game that I do not have access to the source code of.

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• How to specialize template for type derived from particular type

  - by relaxxx

  I have class World which manages creation of object... After creation it calls afterCreation method and I the created object is user-defined type derived from Entity (eg. MyEntity), I want to call addEntity. I the object was something else, I want to do nothing. addEntity must be called with appropriate T, because it generates unique IDs for every derived class etc. Here is my solution: template <int v> struct ToType { enum { value = v }; }; template <typename T> void World::afterCreation(T * t) { afterCreation(t, ToType<std::is_base_of<Entity, T>::value>()); } template <typename T> void World::afterCreation(T * t, ToType<true>) { addEntity(t); //here I cant pass Entity *, I need the real type, eg. MyEntity } template <typename T> void World::afterCreation(T * t, ToType<false>) { } My question is - Can in be done better way? How can I simulate following code without ToType or similar? template <typename T> void afterCreation(){/*generic impl*/} template <typename T where T is derived from Entity> void afterCreation(){/*some specific stuff*/} "specialize" in the title is only to describe my intention, no need to solve problem with template specialization

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• Apply PHP regex replace on a multi-line repeated pattern

  - by Hussain

  Let's say I have this input: I can haz a listz0rs! # 42 # 126 I can haz another list plox? # Hello, world! # Welcome! I want to split it so that each set of hash-started lines becomes a list: I can haz a listz0rs! <ul> <li>42</li> <li>126</li> </ul> I can haz another list plox? <ul> <li>Hello, world!</li> <li>Welcome!</li> </ul> If I run the input against the regex "/(?:(?:(?<=^# )(.*)$)+)/m", I get the following result: Array ( [0] => Array ( [0] => 42 ) [1] => Array ( [0] => 126 ) [2] => Array ( [0] => Hello, world! ) [3] => Array ( [0] => Welcome! ) ) This is fine and dandy, but it doesn't distinguish between the two different lists. I need a way to either make the quantifier return a concatenated string of all the occurrences, or, ideally, an array of all the occurrences. Ideally, this should be my output: Array ( [0] => Array ( [0] => 42 [1] => 126 ) [1] => Array ( [0] => Hello, world! [1] => Welcome! ) ) Is there any way of achieving this, and if not, is there a close alternative? Thanks in advance!

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• Better use a tuple or numpy array for storing coordinates

  - by Ivan

  Hi, I'm porting an C++ scientific application to python, and as I'm new to python, some problems come to my mind: 1) I'm defining a class that will contain the coordinates (x,y). These values will be accessed several times, but they only will be read after the class instantiation. Is it better to use an tuple or an numpy array, both in memory and access time wise? 2) In some cases, these coordinates will be used to build a complex number, evaluated on a complex function, and the real part of this function will be used. Assuming that there is no way to separate real and complex parts of this function, and the real part will have to be used on the end, maybe is better to use directly complex numbers to store (x,y)? How bad is the overhead with the transformation from complex to real in python? The code in c++ does a lot of these transformations, and this is a big slowdown in that code. 3) Also some coordinates transformations will have to be performed, and for the coordinates the x and y values will be accessed in separate, the transformation be done, and the result returned. The coordinate transformations are defined in the complex plane, so is still faster to use the components x and y directly than relying on the complex variables? Thank you

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• How to determine which inheriting class is using an abstract class's methods.

  - by Kin

  In my console application have an abstract Factory class "Listener" which contains code for listening and accepting connections, and spawning client classes. This class is inherited by two more classes (WorldListener, and MasterListener) that contain more protocol specific overrides and functions. I also have a helper class (ConsoleWrapper) which encapsulates and extends System.Console, containing methods for writing to console info on what is happening to instances of the WorldListener and MasterListener. I need a way to determine in the abstract ListenerClass which Inheriting class is calling its methods. Any help with this problem would be greatly appreciated! I am stumped :X Simplified example of what I am trying to do. abstract class Listener { public void DoSomething() { if(inheriting class == WorldListener) ConsoleWrapper.WorldWrite("Did something!"); if(inheriting class == MasterListener) ConsoleWrapper.MasterWrite("Did something!"); } } public static ConsoleWrapper { public void WorldWrite(string input) { System.Console.WriteLine("[World] {0}", input); } } public class WorldListener : Listener { public void DoSomethingSpecific() { ConsoleWrapper.WorldWrite("I did something specific!"); } } public void Main() { new WorldListener(); new MasterListener(); } Expected output [World] Did something! [World] I did something specific! [Master] Did something! [World] I did something specific!

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• Ajax and JSF 1.1 using hidden iframe with "proxy forms", what do you think about this development st

  - by Steel Plume

  Hi, currently I am using yet 1.1 specs, so I am trying to make simple what is too complex for me :p, managing backing beans with conflicting navigation rules, external params breaking rules and so on... for example when I need a backing bean used by other "views" simply I call it using FacesContext inside other backing beans, but often it's too wired up to JSF navigation/initialization rules to be really usable, and of course more simple is more useful become the FacesContext. So with only a bit of cross browser Javascript (simply a form copy and a read-write on a "proxy" form), I create a sort of proxy form inside the main user page (totally disassociated from JSF navigation rules, but using JSF taglibs). Ajax gives me flexibility on the user interaction, but data is always managed by JSF. Pratically I demand all "fictious" user actions to an hidden "iframe" which build up all needed forms according JSF rules, then a javascript simply clone its form output and put it into the user view level (CSS for showing/hiding real command buttons and making pretty), the user plays around and when he click submit, a script copies all "proxied" form values into the real JSF form inside the "iframe" that invokes the real submit of the form, what it returns is obviously dependent by your choice. Now JSF is really a pleasure :-p My real interest is to know what are your alternative strategy for using pure Ajax and JSF 1.1 without adopting middle layer like ajax4jsf and others, all good choices but too much "plugins" than specs.

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• Am I doing AS3 reference cleanup correctly?

  - by Ólafur Waage

  In one frame of my fla file (let's call it frame 2), I load a few xml files, then send that data into a class that is initialized in that frame, this class creates a few timers and listeners. Then when this class is done doing it's work. I call a dispatchEvent and move to frame 3. This frame does some things as well, it's initialized and creates a few event listeners and timers. When it's done, I move to frame 2 again. This is supposed to repeat as often as I need so I need to clean up the references correctly and I'm wondering if I'm doing it correctly. For sprites I do this. world.removeChild(Background); // world is the parent stage Background = null; For instances of other classes I do this. Players[i].cleanUp(world); // do any cleanup within the instanced class world.removeChild(PlayersSelect[i]); For event listeners I do this. if(Background != null) { Background.removeEventListener(MouseEvent.CLICK, deSelectPlayer); } For timers I do this. if(Timeout != null) { Timeout.stop(); Timeout.removeEventListener(TimerEvent.TIMER, queueHandler); Timeout.removeEventListener(TimerEvent.TIMER_COMPLETE, queueCompleted); Timeout = null; } And for library images I do this if(_libImage!= null) { s.removeChild(Images._libImage); // s is the stage _libImage= null; } And for the class itself in the main timeline, I do this Frame2.removeEventListener("Done", IAmDone); Frame2.cleanUp(); // the cleanup() does all the stuff above Frame2= null; Even if I do all this, when I get to frame 2 for the 2nd time, it runs for 1-2 seconds and then I get a lot of null reference errors because the cleanup function is called prematurely. Am I doing the cleanup correctly? What can cause events to fire prematurely?

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