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• How to analyze the efficiency of this algorithm Part 2

  - by Leonardo Lopez

  I found an error in the way I explained this question before, so here it goes again: FUNCTION SEEK(A,X) 1. FOUND = FALSE 2. K = 1 3. WHILE (NOT FOUND) AND (K < N) a. IF (A[K] = X THEN 1. FOUND = TRUE b. ELSE 1. K = K + 1 4. RETURN Analyzing this algorithm (pseudocode), I can count the number of steps it takes to finish, and analyze its efficiency in theta notation, T(n), a linear algorithm. OK. This following code depends on the inner formulas inside the loop in order to finish, the deal is that there is no variable N in the code, therefore the efficiency of this algorithm will always be the same since we're assigning the value of 1 to both A & B variables: 1. A = 1 2. B = 1 3. UNTIL (B > 100) a. B = 2A - 2 b. A = A + 3 Now I believe this algorithm performs in constant time, always. But how can I use Algebra in order to find out how many steps it takes to finish?

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• How can I apply a PSSM efficiently?

  - by flies

  I am fitting for position specific scoring matrices (PSSM aka Position Specific Weight Matrices). The fit I'm using is like simulated annealing, where I the perturb the PSSM, compare the prediction to experiment and accept the change if it improves agreement. This means I apply the PSSM millions of times per fit; performance is critical. In my particular problem, I'm applying a PSSM for an object of length L (~8 bp) at every position of a DNA sequence of length M (~30 bp) (so there are M-L+1 valid positions). I need an efficient algorithm to apply a PSSM. Can anyone help improve performance? My best idea is to convert the DNA into some kind of a matrix so that applying the PSSM is matrix multiplication. There are efficient linear algebra libraries out there (e.g. BLAS), but I'm not sure how best to turn an M-length DNA sequence into a matrix M x 4 matrix and then apply the PSSM at each position. The solution needs to work for higher order/dinucleotide terms in the PSSM - presumably this means representing the sequence-matrix for mono-nucleotides and separately for dinucleotides. My current solution iterates over each position m, then over each letter in word from m to m+L-1, adding the corresponding term in the matrix. I'm storing the matrix as a multi-dimensional STL vector, and profiling has revealed that a lot of the computation time is just accessing the elements of the PSSM (with similar performance bottlenecks accessing the DNA sequence). If someone has an idea besides matrix multiplication, I'm all ears.

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• MKL Accelerated Math Libraries for Java...

  - by Kaopua

  I've looked at the related threads on StackOverflow and Googled with not much luck. I'm also very new to Java (I'm coming from a C# and .NET background) so please bear with me. There is so much available in the Java world it's pretty overwhelming. I'm starting on a new Java-on-Linux project that requires some heavy and highly repetitious numerical calculations (i.e. statistics, FFT, Linear Algebra, Matrices, etc.). So maximizing the performance of the mathematical operations is a requirement, as is ensuring the math is correct. So hence I have an interest in finding a Java library that perhaps leverages native acceleration such as MKL, and is proven (so commercial options are definitely a possibility here). In the .NET space there are highly optimized and MKL accelerated commercial Mathematical libraries such as Centerspace NMath and Extreme Optimization. Is there anything comparable in Java? Most of the math libraries I have found for Java either do not seem to be actively maintained (such as Colt) or do not appear to leverage MKL or other native acceleration (such as Apache Commons Math). I have considered trying to leverage MKL directly from Java myself (e.g. JNI), but me being new to Java (let alone interoperating between Java and native libraries) it seemed smarter finding a Java library that has already done this correctly, efficiently, and is proven. Again I apologize if I am mistaken or misguided (even in regarding any libraries I've mentioned) and my ignorance of the Java offerings. It's a whole new world for me coming from the heavily commercialized Microsoft stock so I could easily be mistaken on where to look and regarding the Java libraries I've mentioned. I would greatly appreciate any help or advice.

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• Have any software engineers gotten math degrees later in their careers?

  - by vin

  I have a bachelors in computer science and worked the last 12 years as a software engineer. I'm bored with doing general development work, so I want to specialize. I'm thinking about getting a master's degree in math so I can build math models and write algorithms to implement them. I'm unsure what type of work I'd do (financial, gaming, graphics, science, research, etc) but I'm open minded. I would need to refresh my undergrad math skills (which are old and faded), but I loved algebra and calculus. I've been working with couple statisticians so I've been finding myself more interested in statistics. Since I'm a parent supporting a household, I would have to continue working while studying. Have any software engineers taken this route? (Specifically, going from BS in comp sci to MS in math.) If so, what advice do you have for coursework, financing, and getting a job that combines programming with advanced math? How abundant are these kinds of jobs? I'm not sure where one starts. Also, how do you hop from a BS to an MS in a different subject?

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• algorithim for simple colision detection in Java

  - by Bob Twinkles

  I'm not very experienced with Java, just started a couple weeks ago, but I have a simple applet that has two user controlled balls, drawn through java.awt and I need a way to detect a collision with between them. I have an algorithm for detecting collision with the walls: while (true){ if (xPositon > (300 - radius)){ xSpeed = -xSpeed; } else if (xPositon < radius){ xSpeed = -xSpeed; } else if (yPositon > (300 - radius)) { ySpeed = -ySpeed; } else if (yPositon < radius){ ySpeed = -ySpeed; } xPositon += xSpeed; yPositon += ySpeed; and for the second ball if (xPositon2 > (300 - radius)){ xSpeed2 = -xSpeed2; } else if (xPositon2 < radius){ xSpeed2 = -xSpeed2; } else if (yPositon2 > (300 - radius)) { ySpeed2 = -ySpeed2; } else if (yPositon2 < radius){ ySpeed2 = -ySpeed2; } xPositon2 += xSpeed2; yPositon2 += ySpeed2; the applet is 300 pixels by 300 pixels radius stores the radius of the circles xPositon and xPositon2 store the x cordanents for the two balls yPositon and yPositon store the y cordanents for the two balls xSpeed and xSpeed2 store the x velocities for the two balls ySpeed and ySpeed2 store the y velocities for the two balls I've only taken algebra 1 so please no advanced math or physics.

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• Learning Basic Mathematics

  - by NeedsToKnow

  I'm going to just come out and say it. I'm 20 and can't do maths. Two years ago I passed the end-of-high-school mathematics exam (but not at school), and did pretty well. Since then, I haven't done a scrap of mathematics. I wondered just how bad I had gotten, so I was looking at some simple algebra problems. You know, the kind you learn halfway through highschool. 5(-3x - 2) - (x - 3) = -4(4x + 5) + 13 Couldn't do them. I've got half a year left until I start a Computer Science undergraduate degree. I love designing and creating programs, and I remember I loved mathematics back when I did it. Basically, I've had a pretty bad education, but I want to be knowledgable in these areas. I was thinking of buying some high school textbooks and reading them, but I'm not sure this is the right way to go. I need to start off at some basic level and work towards a greater understanding. My question is: What should I study, how should I study, and what books can you recommend? Thanks!

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• Matlab matrix translation and rotation multiple times

  - by pinnacler

  I have a map of individual trees from a forest stored as x,y points in a matrix. I call it fixedPositions. It's cartesian and (0,0) is the origin. I would like 0/360 degrees to be the top of the screen and 90 degrees to be to the right. Given a velocity and a heading, i.e. .5 m/s and 60 degrees (2 o'clock equivalent on a watch), how do I rotate that x,y points, so that the new origin is centered at (.5cos(60),.5sin(60)) and 60 degrees is now at the top of the screen? Then if I were to give you another heading and speed, i.e. 0 degrees and 2m/s, it should calculate it from the last point, not the original fixedPositions origin. I've wasted my day trying to figure this out. I wish I took matrix algebra but I'm at a loss. I tried doing cos(30) and even those wouldn't compute correctly, which after an hour I realize were in radians.

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• Is there really such a thing as "being good at math"?

  - by thezhaba

  Aside from gifted individuals able to perform complex calculations in their head, I'm wondering if proficiency in mathematics, namely calculus and algebra, has really got to do with one's natural inclination towards sciences, if you can put it that way. A number of students in my calculus course pick up material in seemingly no time whereas I, personally, have to spend time thinking about and understanding most concepts. Even then, if a question that requires a bit more 'imagination' comes up I don't always recognize the concepts behind it, as is the case with calculus proofs, for instance. Nevertheless, I refuse to believe that I'm simply not made for it. I do very well in programming and software engineering courses where a lot of students struggle. At first I could not grasp what they found to be so difficult, but eventually I realized that having previous programming experience is a great asset -- once I've seen and made practical use of the programming concepts learning about them in depth in an academic setting became much easier as I have then already seen their use "in the wild". I suppose I'm hoping that something similar happens with mathematics -- perhaps once the practical idea behind a concept (which authors of textbooks sure do a great job of concealing..) is evident, understanding the seemingly dry and symbolic ideas and proofs would be more obvious? I'm really not sure. All I'm sure of is I'd like to get better at calculus, but I don't yet understand why some of us pick it up easily while others have to spend considerable amounts of time on it and still not have complete understanding if an unusual problem is given.

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• Can Haskell's monads be thought of as using and returning a hidden state parameter?

  - by AJM

  I don't understand the exact algebra and theory behind Haskell's monads. However, when I think about functional programming in general I get the impression that state would be modelled by taking an initial state and generating a copy of it to represent the next state. This is like when one list is appended to another; neither list gets modified, but a third list is created and returned. Is it therefore valid to think of monadic operations as implicitly taking an initial state object as a parameter and implicitly returning a final state object? These state objects would be hidden so that the programmer doesn't have to worry about them and to control how they gets accessed. So, the programmer would not try to copy the object representing the IO stream as it was ten minutes ago. In other words, if we have this code: main = do putStrLn "Enter your name:" name <- getLine putStrLn ( "Hello " ++ name ) ...is it OK to think of the IO monad and the "do" syntax as representing this style of code? putStrLn :: IOState -> String -> IOState getLine :: IOState -> (IOState, String) main :: IOState -> IOState -- main returns an IOState we can call "state3" main state0 = putStrLn state2 ("Hello " ++ name) where (state2, name) = getLine state1 state1 = putStrLn state0 "Enter your name:"

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• How do I become better in math, after being a programmer for several years.

  - by loxs

  I've had quite a weird career till now. First I graduated from a medical school. Then I went into marketing (pharmaceuticals). And then umm, after some time, I decided to go for my (till then) hobby and became a "professional" programmer. I've been quite successful at this ever since. I have quite some languages "under my belt". I earn not bad and I have been involved in the opensource community quite heavily. The thing is that I suck at math :). Well, not totally of course, as I get my work done. But I don't know how much I suck. And I don't know how to find out. Math has never really been of any priority during my middle/high school years. I only picked as little as I could afford, because I was always getting ready to go for Medicine. Of course I know the basics of algebra. Things like "normal" and square equations. Also the basics of geometry. But well, there are things that I have missed. And lately I am being fascinated by things like probability theory, infinity, chaos/order etc. But every time I try to learn something about these topics, I hit a wall of terminology, special symbols, and some special kind of thinking, that is quite like mine (a programmer), but also a lot different (and appears weird to me). So, what kinds of books would you recommend me? It's very hard to find something suitable. All that I find are either too easy (and boring) or totally impenetrable.

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• Interesting Scala typing solution, doesn't work in 2.7.7?

  - by djc

  I'm trying to build some image algebra code that can work with images (basically a linear pixel buffer + dimensions) that have different types for the pixel. To get this to work, I've defined a parametrized Pixel trait with a few methods that should be able to get used with any Pixel subclass. (For now, I'm only interested in operations that work on the same Pixel type.) Here it is: trait Pixel[T <: Pixel[T]] { def mul(v: Double): T def max(v: T): T def div(v: Double): T def div(v: T): T } Now I define a single Pixel type that has storage based on three doubles (basically RGB 0.0-1.0), I've called it TripleDoublePixel: class TripleDoublePixel(v: Array[Double]) extends Pixel[TripleDoublePixel] { var data: Array[Double] = v def this() = this(Array(0.0, 0.0, 0.0)) def toString(): String = { "(" + data(0) + ", " + data(1) + ", " + data(2) + ")" } def increment(v: TripleDoublePixel) { data(0) += v.data(0) data(1) += v.data(1) data(2) += v.data(2) } def mul(v: Double): TripleDoublePixel = { new TripleDoublePixel(data.map(x => x * v)) } def div(v: Double): TripleDoublePixel = { new TripleDoublePixel(data.map(x => x / v)) } def div(v: TripleDoublePixel): TripleDoublePixel = { var tmp = new Array[Double](3) tmp(0) = data(0) / v.data(0) tmp(1) = data(1) / v.data(1) tmp(2) = data(2) / v.data(2) new TripleDoublePixel(tmp) } def max(v: TripleDoublePixel): TripleDoublePixel = { val lv = data(0) * data(0) + data(1) * data(1) + data(2) * data(2) val vv = v.data(0) * v.data(0) + v.data(1) * v.data(1) + v.data(2) * v.data(2) if (lv > vv) (this) else v } } Now I want to write code to use this, that doesn't have to know what type the pixels are. For example: def idiv[T](a: Image[T], b: Image[T]) { for (i <- 0 until a.data.size) { a.data(i) = a.data(i).div(b.data(i)) } } Unfortunately, this doesn't compile: (fragment of lindet-gen.scala):145: error: value div is not a member of T a.data(i) = a.data(i).div(b.data(i)) I was told in #scala that this worked for someone else, but that was on 2.8. I've tried to get 2.8-rc1 going, but it doesn't compile for me. Is there any way to get this to work in 2.7.7?

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• R Random Data Sets within loops

  - by jugossery

  Here is what I want to do: I have a time series data frame with let us say 100 time-series of length 600 - each in one column of the data frame. I want to pick up 4 of the time-series randomly and then assign them random weights that sum up to one (ie 0.1, 0.5, 0.3, 0.1). Using those I want to compute the mean of the sum of the 4 weighted time series variables (e.g. convex combination). I want to do this let us say 100k times and store each result in the form ts1.name, ts2.name, ts3.name, ts4.name, weight1, weight2, weight3, weight4, mean so that I get a 9*100k df. I tried some things already but R is very bad with loops and I know vector oriented solutions are better because of R design. Thanks Here is what I did and I know it is horrible The df is in the form v1,v2,v2.....v100 1,5,6,.......9 2,4,6,.......10 3,5,8,.......6 2,2,8,.......2 etc e=NULL for (x in 1:100000) { s=sample(1:100,4)#pick 4 variables randomly a=sample(seq(0,1,0.01),1) b=sample(seq(0,1-a,0.01),1) c=sample(seq(0,(1-a-b),0.01),1) d=1-a-b-c e=c(a,b,c,d)#4 random weights average=mean(timeseries.df[,s]%*%t(e)) e=rbind(e,s,average)#in the end i get the 9*100k df } The procedure runs way to slow. EDIT: Thanks for the help i had,i am not used to think R and i am not very used to translate every problem into a matrix algebra equation which is what you need in R. Then the problem becomes a little bit complex if i want to calculate the standard deviation. i need the covariance matrix and i am not sure i can if/how i can pick random elements for each sample from the original timeseries.df covariance matrix then compute the sample variance (t(sampleweights)%*%sample_cov.mat%*%sampleweights) to get in the end the ts.weighted_standard_dev matrix Last question what is the best way to proceed if i want to bootstrap the original df x times and then apply the same computations to test the robustness of my datas thanks

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• Rails won't install on Ubuntu because of builder

  - by Jason Swett

  Can someone explain why gem thinks I don't have builder = 2.1.2 even though I clearly have 3.0.0? jason@ve:~$ gem install rails --pre ERROR: Error installing rails: activemodel requires builder (~> 2.1.2, runtime) jason@ve:~$ gem list *** LOCAL GEMS *** abstract (1.0.0) activesupport (3.0.3, 3.0.0.rc2) builder (3.0.0) erubis (2.6.6) i18n (0.5.0) mail (2.2.13) memcache-client (1.8.5) mime-types (1.16) polyglot (0.3.1) rack (1.2.1) rack-mount (0.6.13) rack-test (0.5.6) text-format (1.0.0) text-hyphen (1.0.0) treetop (1.4.9) tzinfo (0.3.23) jason@ve:~$

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• What is Openflow?

  - by jmreicha

  Okay, I've been thinking about this a lot recently but I think I may be more confused now than I was originally when I started. I can't find anything about Openflow that helps me understand what it is. None of the websites I have found have given a solid definition of what Openflow really is and what it does, at least if they do I can't comprehend it. Is there an easy way to explain this standard so my small brain can understand it? I understand that Openflow is a way to abstract networking away from switches and can be managed from software, etc etc. I feel like it might be a little easier to grasp if I had exmaples of application. But so far searching has failed me. What is Openflow? How can it help me? What does it offer?

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• Which OS/distributions have 64-bit kernel and 32-bit userspace? [closed]

  - by osgx

  Which OS (or distributions) comes with 64-bit kernels (x86_64, SPARC64, PPC64, ..smth else?..) and 32-bit userland? I want all small userspace programs (like ls, cat, etc) to be 32-bit, because they really no needs to be 64-bit. But OS kernel must be 64bit for using =3 Gb of RAM. Also database programs (when using a lot of memory) can be 64bit. 64bit mode can hurt some programs, makes them bigger, eating (wasting) memory on pointers (especially in big abstract datatypes like list, tree, etc). 64 bit programss WASTES twice memory on EACH Pointer. I don't want it. And the Question is not "Are the 32-bit programs needed when 64-bit porcessor is available". Question is "What OS comes with 32 bit userspace and kernels in 32/64 bit mode". Examples of such OS includes: Solaris/SPARC64, MACOSX/X86_64 (10.5)/....

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• Distributed Database Services?

  - by Cameron

  I'm working on a database-driven web service with clients in the US and Australia. We're currently hosted in the US, however our Australian clients are experiencing lag. The lag is primarily due to the fact that the pages launch AJAX queries which require some db work to be done on our database in the US and these take a while to perform a round trip. Ideally, we're looking for some kind of distributed database system which replicates our main US database in Australia (and possibly other locations if we choose to expand later on). Does anyone have any suggestions for services which offer something like this? Something like a CDN (CacheFly etc), which is web-based, simple to set up etc but for databases instead of static files. Ideally it would be completely transparent to the application and abstract away all the distributed database management, syncs etc.

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• SQL Server 2008 R2 100% availability

  - by Mark Henderson

  Is there any way to provide 100% uptime on SQL Server 2008 R2? From my experience, the downtimes for the different replication methods are: Log Shipping: Lots (for DR only) Mirroring w. NLB: ~ 45 seconds Clustering: ~ 5-15 seconds And all of these solutions involve all of the connections being dropped from the source, so if the downtime is too long or the app's gateway doesn't support reconnection in the middle of task, then you're out of luck. The only way I can think to get around this is to abstract the clustering a level (by virtualising and then enabling VMWare FT. Yuck. Good luck getting this to work on a quad-socket, 32-core system anyway.). Is there any other way of providing 100% uptime of SQL Server?

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• Emulating CP/M under Linux

  - by gh403

  I need to be able to run a very old piece of software -- the HI-TECH z80 C Compiler for CP/M. It has been released as freeware by HI-TECH. Alas, it only runs on CP/M. After a lot of Googling, I found a page of utilities for UZIX. One of those utilities is a script to abstract away the emulation of a CP/M machine, thus allowing you to use the compiler as you would any other UNIX program. The problem with this script is that it depends on their own CP/M emulator, which unfortunately will not compile on a modern (x64) system. My question: is there a usable CP/M emulator for Linux that could be used in a similar fashion? Specifically, I need to be able to somehow have it access files from the host system, a la DOSBox. I'm willing to rewrite a script (I don't have to re-use the UZIX one); I just need an emulator. Thanks for any help!

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• What is the world wide web? [closed]

  - by think123

  I don't know where to post this question, so please move it if necessary. Ok, so I've heard of how the professional hosting companies can create 'links' to the world wide web to register an unregistered domain. So that's where my question comes from. Is the world wide web a server to which servers link? Is it created by abstract linkage? I'm not sure. Also, what does it mean for the DNS to be updated throughout the whole world?

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• Is ceph usable with only 100Mbps bandwidth between nodes?

  - by vaab

  I haven't great hardware, but my requirements are low, I would like to start using ceph so as to abstract filesystem location and allow potential easy scaling to bigger hardware in an hypothetical future. My actual hardware meets ceph hardware requirements except the ethernet bandwidth part between the hosts. Mine is 100 Mbit/s which is much lower than the 1Gbps expected in ceph, even from the minimal requirement. Will I be able to use ceph in a very small smili-prod environnement (with limited number of clients) ? FYI: My hardware is 2 or maybe 3 hosts having each 4 core Intel, 24Go RAM, 2x2To disks but 100Mpbs between them.

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• Is Inheritance in Struts2 Model-Driven Action possible?

  - by mryan

  Hello, I have a Model-Driven Struts2 action that provides correct JSON response. When I re-structure the action I get an empty JSON response back. Has anyone got inheritance working with Struts2 Model-Driven actions? Ive tried explicitly setting include properties in struts config: <result name="json" type="json"> <param name="includeProperties"> jsonResponse </param> </result> Code for all actions below - not actual code in use - I have edited and stripped down for clarity. Thanks in advance. Action providing correct response: public class Bike extends ActionSupport implements ModelDriven, Preparable { @Autowired private Service bikeService; private JsonResponse jsonResponse; private com.ets.model.Vehicle bike; private int id; public Bike() { jsonResponse = new JsonResponse("Bike"); } @Override public void prepare() throws Exception { if (id == 0) { bike = new com.ets.model.Bike(); } else { bike = bikeService.find(id); } } @Override public Object getModel() { return bike; } public void setId(int id) { this.id = id; } public void setBikeService(@Qualifier("bikeService") Service bikeService) { this.bikeService = bikeService; } public JsonResponse getJsonResponse() { return jsonResponse; } public String delete() { try { bike.setDeleted(new Date(System.currentTimeMillis())); bikeService.updateOrSave(bike); jsonResponse.addActionedId(id); jsonResponse.setAction("delete"); jsonResponse.setValid(true); } catch (Exception exception) { jsonResponse.setMessage(exception.toString()); } return "json"; } } Re-structured Actions providing incorrect response: public abstract class Vehicle extends ActionSupport implements ModelDriven { @Autowired protected Service bikeService; @Autowired protected Service carService; protected JsonResponse jsonResponse; protected com.ets.model.Vehicle vehicle; protected int id; protected abstract Service service(); @Override public Object getModel() { return bike; } public void setId(int id) { this.id = id; } public void setBikeService(@Qualifier("bikeService") Service bikeService) { this.bikeService = bikeService; } public void setCarService(@Qualifier("carService") Service carService) { this.carService = carService; } public JsonResponse getJsonResponse() { return jsonResponse; } public String delete() { try { vehicle.setDeleted(new Date(System.currentTimeMillis())); service().updateOrSave(vehicle); jsonResponse.addActionedId(id); jsonResponse.setAction("delete"); jsonResponse.setValid(true); } catch (Exception exception) { jsonResponse.setMessage(exception.toString()); } return "json"; } } public class Bike extends Vehicle implements Preparable { public Bike() { jsonResponse = new JsonResponse("Bike"); } @Override public void prepare() throws Exception { if (id == 0) { vehicle = new com.ets.model.Bike(); } else { vehicle = bikeService.find(id); } } @Override protected Service service() { return bikeService; } } public class Car extends Vehicle implements Preparable { public Car() { jsonResponse = new JsonResponse("Car"); } @Override public void prepare() throws Exception { if (id == 0) { vehicle = new com.ets.model.Car(); } else { vehicle = carService.find(id); } } @Override protected Service service() { return carService; } }

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• RAILS : authlogic authenication / session error , "session contains objects whose class definition i

  - by Surya

  Session contains objects whose class definition isn\'t available. Remember to require the classes for all objects kept in the session I am trying to integrate http://github.com/binarylogic/authlogic for authentication into my rails application . I follwed all the steps into mentioned in the documentation . Now i seem to be getting this error when i hit a controller . Looks like i am missing something obvious . stacktrace /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:77:in `stale_session_check!' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:61:in `load!' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:28:in `[]' /Library/Ruby/Gems/1.8/gems/authlogic-2.1.3/lib/authlogic/session/session.rb:48:in `session_credentials' /Library/Ruby/Gems/1.8/gems/authlogic-2.1.3/lib/authlogic/session/session.rb:33:in `persist_by_session' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/callbacks.rb:178:in `send' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/callbacks.rb:178:in `evaluate_method' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/callbacks.rb:166:in `call' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/callbacks.rb:93:in `run' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/callbacks.rb:92:in `each' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/callbacks.rb:92:in `send' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/callbacks.rb:92:in `run' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/callbacks.rb:276:in `run_callbacks' /Library/Ruby/Gems/1.8/gems/authlogic-2.1.3/lib/authlogic/session/callbacks.rb:79:in `persist' /Library/Ruby/Gems/1.8/gems/authlogic-2.1.3/lib/authlogic/session/persistence.rb:55:in `persisting?' /Library/Ruby/Gems/1.8/gems/authlogic-2.1.3/lib/authlogic/session/persistence.rb:39:in `find' /Users/suryagaddipati/myprojects/groceryplanner/app/controllers/application_controller.rb:12:in `current_user_session' /Users/suryagaddipati/myprojects/groceryplanner/app/controllers/application_controller.rb:17:in `current_user' /Users/suryagaddipati/myprojects/groceryplanner/app/controllers/application_controller.rb:30:in `require_no_user' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/callbacks.rb:178:in `send' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/callbacks.rb:178:in `evaluate_method' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/callbacks.rb:166:in `call' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/filters.rb:225:in `call' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/filters.rb:629:in `run_before_filters' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/filters.rb:615:in `call_filters' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/filters.rb:610:in `perform_action_without_benchmark' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/benchmarking.rb:68:in `perform_action_without_rescue' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/benchmark.rb:17:in `ms' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/benchmark.rb:10:in `realtime' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/benchmark.rb:17:in `ms' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/benchmarking.rb:68:in `perform_action_without_rescue' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/rescue.rb:160:in `perform_action_without_flash' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/flash.rb:146:in `perform_action' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:532:in `send' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:532:in `process_without_filters' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/filters.rb:606:in `process' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:391:in `process' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:386:in `call' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/routing/route_set.rb:437:in `call' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:87:in `dispatch' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:121:in `_call' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:130:in `build_middleware_stack' /Library/Ruby/Gems/1.8/gems/activerecord-2.3.5/lib/active_record/query_cache.rb:29:in `call' /Library/Ruby/Gems/1.8/gems/activerecord-2.3.5/lib/active_record/query_cache.rb:29:in `call' /Library/Ruby/Gems/1.8/gems/activerecord-2.3.5/lib/active_record/connection_adapters/abstract/query_cache.rb:34:in `cache' /Library/Ruby/Gems/1.8/gems/activerecord-2.3.5/lib/active_record/query_cache.rb:9:in `cache' /Library/Ruby/Gems/1.8/gems/activerecord-2.3.5/lib/active_record/query_cache.rb:28:in `call' /Library/Ruby/Gems/1.8/gems/activerecord-2.3.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:361:in `call' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/string_coercion.rb:25:in `call' /Users/suryagaddipati/.gem/ruby/1.8/gems/rack-1.0.1/lib/rack/head.rb:9:in `call'

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• RAILS :"session contains objects whose class definition isn\'t available."

  - by Surya

  Session contains objects whose class definition isn\'t available. Remember to require the classes for all objects kept in the session I am trying to integrate http://github.com/binarylogic/authlogic for authentication into my rails application . I follwed all the steps into mentioned in the documentation . Now i seem to be getting this error when i hit a controller . Looks like i am missing something obvious . stacktrace /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:77:in `stale_session_check!' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:61:in `load!' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:28:in `[]' /Library/Ruby/Gems/1.8/gems/authlogic-2.1.3/lib/authlogic/session/session.rb:48:in `session_credentials' /Library/Ruby/Gems/1.8/gems/authlogic-2.1.3/lib/authlogic/session/session.rb:33:in `persist_by_session' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/callbacks.rb:178:in `send' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/callbacks.rb:178:in `evaluate_method' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/callbacks.rb:166:in `call' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/callbacks.rb:93:in `run' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/callbacks.rb:92:in `each' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/callbacks.rb:92:in `send' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/callbacks.rb:92:in `run' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/callbacks.rb:276:in `run_callbacks' /Library/Ruby/Gems/1.8/gems/authlogic-2.1.3/lib/authlogic/session/callbacks.rb:79:in `persist' /Library/Ruby/Gems/1.8/gems/authlogic-2.1.3/lib/authlogic/session/persistence.rb:55:in `persisting?' /Library/Ruby/Gems/1.8/gems/authlogic-2.1.3/lib/authlogic/session/persistence.rb:39:in `find' /Users/suryagaddipati/myprojects/groceryplanner/app/controllers/application_controller.rb:12:in `current_user_session' /Users/suryagaddipati/myprojects/groceryplanner/app/controllers/application_controller.rb:17:in `current_user' /Users/suryagaddipati/myprojects/groceryplanner/app/controllers/application_controller.rb:30:in `require_no_user' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/callbacks.rb:178:in `send' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/callbacks.rb:178:in `evaluate_method' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/callbacks.rb:166:in `call' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/filters.rb:225:in `call' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/filters.rb:629:in `run_before_filters' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/filters.rb:615:in `call_filters' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/filters.rb:610:in `perform_action_without_benchmark' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/benchmarking.rb:68:in `perform_action_without_rescue' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/benchmark.rb:17:in `ms' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/benchmark.rb:10:in `realtime' /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/benchmark.rb:17:in `ms' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/benchmarking.rb:68:in `perform_action_without_rescue' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/rescue.rb:160:in `perform_action_without_flash' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/flash.rb:146:in `perform_action' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:532:in `send' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:532:in `process_without_filters' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/filters.rb:606:in `process' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:391:in `process' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:386:in `call' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/routing/route_set.rb:437:in `call' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:87:in `dispatch' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:121:in `_call' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:130:in `build_middleware_stack' /Library/Ruby/Gems/1.8/gems/activerecord-2.3.5/lib/active_record/query_cache.rb:29:in `call' /Library/Ruby/Gems/1.8/gems/activerecord-2.3.5/lib/active_record/query_cache.rb:29:in `call' /Library/Ruby/Gems/1.8/gems/activerecord-2.3.5/lib/active_record/connection_adapters/abstract/query_cache.rb:34:in `cache' /Library/Ruby/Gems/1.8/gems/activerecord-2.3.5/lib/active_record/query_cache.rb:9:in `cache' /Library/Ruby/Gems/1.8/gems/activerecord-2.3.5/lib/active_record/query_cache.rb:28:in `call' /Library/Ruby/Gems/1.8/gems/activerecord-2.3.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:361:in `call' /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/string_coercion.rb:25:in `call' /Users/suryagaddipati/.gem/ruby/1.8/gems/rack-1.0.1/lib/rack/head.rb:9:in `call'

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• C++ invalid reference problem

  - by Karol

  Hi all, I'm writing some callback implementation in C++. I have an abstract callback class, let's say: /** Abstract callback class. */ class callback { public: /** Executes the callback. */ void call() { do_call(); }; protected: /** Callback call implementation specific to derived callback. */ virtual void do_call() = 0; }; Each callback I create (accepting single-argument functions, double-argument functions...) is created as a mixin using one of the following: /** Makes the callback a single-argument callback. */ template <typename T> class singleArgumentCallback { protected: /** Callback argument. */ T arg; public: /** Constructor. */ singleArgumentCallback(T arg): arg(arg) { } }; /** Makes the callback a double-argument callback. */ template <typename T, typename V> class doubleArgumentCallback { protected: /** Callback argument 1. */ T arg1; /** Callback argument 2. */ V arg2; public: /** Constructor. */ doubleArgumentCallback(T arg1, V arg2): arg1(arg1), arg2(arg2) { } }; For example, a single-arg function callback would look like this: /** Single-arg callbacks. */ template <typename T> class singleArgFunctionCallback: public callback, protected singleArgumentCallback<T> { /** Callback. */ void (*callbackMethod)(T arg); public: /** Constructor. */ singleArgFunctionCallback(void (*callback)(T), T argument): singleArgumentCallback<T>(argument), callbackMethod(callback) { } protected: void do_call() { this->callbackMethod(this->arg); } }; For user convenience, I'd like to have a method that creates a callback without having the user think about details, so that one can call (this interface is not subject to change, unfortunately): void test3(float x) { std::cout << x << std::endl; } void test5(const std::string& s) { std::cout << s << std::endl; } make_callback(&test3, 12.0f)->call(); make_callback(&test5, "oh hai!")->call(); My current implementation of make_callback(...) is as follows: /** Creates a callback object. */ template <typename T, typename U> callback* make_callback( void (*callbackMethod)(T), U argument) { return new singleArgFunctionCallback<T>(callbackMethod, argument); } Unfortunately, when I call make_callback(&test5, "oh hai!")->call(); I get an empty string on the standard output. I believe the problem is that the reference gets out of scope after callback initialization. I tried using pointers and references, but it's impossible to have a pointer/reference to reference, so I failed. The only solution I had was to forbid substituting reference type as T (for example, T cannot be std::string&) but that's a sad solution since I have to create another singleArgCallbackAcceptingReference class accepting a function pointer with following signature: void (*callbackMethod)(T& arg); thus, my code gets duplicated 2^n times, where n is the number of arguments of a callback function. Does anybody know any workaround or has any idea how to fix it? Thanks in advance!

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• WCF endpoint exception

  - by Lijo

  Hi Team, I am just trying with various WCF(in .Net 3.0) scenarios. I am using self hosting. I am getting an exception as "Service 'MyServiceLibrary.NameDecorator' has zero application (non-infrastructure) endpoints. This might be because no configuration file was found for your application, or because no service element matching the service name could be found in the configuration file, or because no endpoints were defined in the service element." I have a config file as follows (which has an endpoint) <?xml version="1.0" encoding="utf-8" ?> <configuration> <system.serviceModel> <services> <service name="Lijo.Samples.NameDecorator" behaviorConfiguration="WeatherServiceBehavior"> <host> <baseAddresses> <add baseAddress="http://localhost:8010/ServiceModelSamples/FreeServiceWorld"/> </baseAddresses> </host> <endpoint address="" binding="wsHttpBinding" contract="Lijo.Samples.IElementaryService" /> <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" /> </service> </services> <behaviors> <serviceBehaviors> <behavior name="WeatherServiceBehavior"> <serviceMetadata httpGetEnabled="true"/> <serviceDebug includeExceptionDetailInFaults="False"/> </behavior> </serviceBehaviors> </behaviors> </system.serviceModel> </configuration> And a Host as using System.ServiceModel; using System.ServiceModel.Dispatcher; using System.ServiceModel.Channels; using System.ServiceModel.Description; using System.Runtime.Serialization; namespace MySelfHostConsoleApp { class Program { static void Main(string[] args) { System.ServiceModel.ServiceHost myHost = new ServiceHost(typeof(MyServiceLibrary.NameDecorator)); myHost.Open(); Console.ReadLine(); } } } My Service is as follows using System.ServiceModel; using System.Runtime.Serialization; namespace MyServiceLibrary { [ServiceContract(Namespace = "http://Lijo.Samples")] public interface IElementaryService { [OperationContract] CompanyLogo GetLogo(); } public class NameDecorator : IElementaryService { public CompanyLogo GetLogo() { CircleType cirlce = new CircleType(); CompanyLogo logo = new CompanyLogo(cirlce); return logo; } } [DataContract] public abstract class IShape { public abstract string SelfExplain(); } [DataContract(Name = "Circle")] public class CircleType : IShape { public override string SelfExplain() { return "I am a Circle"; } } [DataContract(Name = "Triangle")] public class TriangleType : IShape { public override string SelfExplain() { return "I am a Triangle"; } } [DataContract] [KnownType(typeof(CircleType))] [KnownType(typeof(TriangleType))] public class CompanyLogo { private IShape m_shapeOfLogo; [DataMember] public IShape ShapeOfLogo { get { return m_shapeOfLogo; } set { m_shapeOfLogo = value; } } public CompanyLogo(IShape shape) { m_shapeOfLogo = shape; } } } Could you please help me to understand what I am missing here? Thanks Lijo

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