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• How to avoid oscillation by async event based systems?

  - by inf3rno

  Imagine a system where there are data sources which need to be kept in sync. A simple example is model - view data binding by MVC. Now I intend to describe these kind of systems with data sources and hubs. Data sources are publishing and subscribing for events and hubs are relaying events to data sources. By handling an event a data source will change it state described in the event. By publishing an event the data source puts its current state to the event, so other data sources can use that information to change their state accordingly. The only problem with this system, that events can be reflected from the hub or from the other data sources, and that can put the system into an infinite oscillation (by async or infinite loop by sync). For example A -- data source B -- data source H -- hub A -> H -> A -- reflection from the hub A -> H -> B -> H -> A -- reflection from another data source By sync it is relatively easy to solve this issue. You can compare the current state with the event, and if they are equal, you don't change the state and raise the same event again. By async I could not find a solution yet. The state comparison does not work by async event handling because there is eventual consistency, and new events can be published in an inconsistent state causing the same oscillation. For example: A(*->x) -> H -> B(y->x) -- can go parallel with B(*->y) -> H -> A(x->y) -- so first A changes to x state while B changes to y state -- then B changes to x state while A changes to y state -- and so on for eternity... What do you think is there an algorithm to solve this problem? If there is a solution, is it possible to extend it to prevent oscillation caused by multiple hubs, multiple different events, etc... ? update: I don't think I can make this work without a lot of effort. I think this problem is just the same as we have by syncing multiple databases in a distributed system. So I think what I really need is constraints if I want to prevent this problem in an automatic way. What constraints do you suggest?

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• Checking timeouts made more readable

  - by Markus

  I have several situations where I need to control timeouts in a technical application. Either in a loop or as a simple check. Of course – handling this is really easy, but none of these is looking cute. To clarify, here is some C# (Pseudo) code: private DateTime girlWentIntoBathroom; girlWentIntoBathroom = DateTime.Now; do { // do something } while (girlWentIntoBathroom.AddSeconds(10) > DateTime.Now); or if (girlWentIntoBathroom.AddSeconds(10) > DateTime.Now) MessageBox.Show("Wait a little longer"); else MessageBox.Show("Knock louder"); Now I was inspired by something a saw in Ruby on StackOverflow: Now I’m wondering if this construct can be made more readable using extension methods. My goal is something that can be read like “If girlWentIntoBathroom is more than 10 seconds ago” 1st attempt if (girlWentIntoBathroom > (10).Seconds().Ago()) MessageBox.Show("Wait a little longer"); else MessageBox.Show("Knock louder"); So I wrote an extension for integer that converts the integer into a TimeSpan public static TimeSpan Seconds(this int amount) { return new TimeSpan(0, 0, amount); } After that, I wrote an extension for TimeSpan like this: public static DateTime Ago(this TimeSpan diff) { return DateTime.Now.Add(-diff); } This works fine so far, but has a great disadvantage. The logic is inverted! Since girlWentIntoBathroom is a timestamp in the past, the right side of the equation needs to count backwards: impossible. Just inverting the equation is no solution, because it will invert the read sentence as well. 2nd attempt So I tried something new: if (girlWentIntoBathroom.IsMoreThan(10).SecondsAgo()) MessageBox.Show("Knock louder"); else MessageBox.Show("Wait a little longer"); IsMoreThan() needs to transport the past timestamp as well as the span for the extension SecondsAgo(). It could be: public static DateWithIntegerSpan IsMoreThan(this DateTime baseTime, int span) { return new DateWithIntegerSpan() { Date = baseTime, Span = span }; } Where DateWithIntegerSpan is simply: public class DateWithIntegerSpan { public DateTime Date {get; set;} public int Span { get; set; } } And SecondsAgo() is public static bool SecondsAgo(this DateWithIntegerSpan dateAndSpan) { return dateAndSpan.Date.Add(new TimeSpan(0, 0, dateAndSpan.Span)) < DateTime.Now; } Using this approach, the English sentence matches the expected behavior. But the disadvantage is, that I need a helping class (DateWithIntegerSpan). Has anyone an idea to make checking timeouts look more cute and closer to a readable sentence? Am I a little too insane thinking about something minor like this?

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• Java Grade Calculator program for class kepp geting the error "Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException." [migrated]

  - by user2880621

  this is my first question I've posted. I've used this site to look at other questions to help with similar problems I've had. After some cursory looking I couldn't find quite the answer I was looking for so I decided to finally succumb and create an account. I am fairly new to java, only a few weeks into my first class. Anyway, my project is to create a program which takes any amount of students and their grades, and then assign them a letter grade. The catch is, however, that it is on a sort of curve and the other grades' letter are dependent on the the highest. Anything equal to or 10 points below the best grade is an a, anything 11-20 points below is a b, and so on. I am to use an array, but I get this error when ran "Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException." I will go ahead and post my code down below. Thanks for any advice you may be able to give. package grade.calculator; import java.util.Scanner; /** * * @author nichol57 */ public class GradeCalculator { /** * @param args the command line arguments */ public static void main(String[] args) { Scanner input = new Scanner(System.in); System.out.println("Enter the number of students"); int number = input.nextInt(); double[]grades = new double [number]; for (int J = number; J >=0; J--) { System.out.println("Enter the students' grades"); grades[J] = input.nextDouble(); } double best = grades[0]; for (int J = 1; J < number; J++) { if (grades[J] >= best){ best = grades[J]; } } for (int J = 0;J < number; J++){ if (grades[J] >= best - 10){ System.out.println("Student " + J + " score is " + grades[J] + " and grade is " + "A"); } else if (grades[J] >= best - 20){ System.out.println("Student " + J + " score is " + grades[J] + " and grade is " + "B"); } else if (grades[J] >= best - 30) { System.out.println("Student " + J + " score is " + grades[J] + " and grade is " + "C"); } else if (grades[J] >= best - 40) { System.out.println("Student " + J + " score is " + grades[J] + " and grade is " + "D"); } else { System.out.println("Student " + J + " score is " + grades[J] + " and grade is " + "F"); } } // end for loop for output }// end main method }

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• android multitouch problem

  - by Max

  Im aware that there a a couple of posts on this matter, but Ive tried all of them and none of them gets rid of my problem. Im starting to get close to the end of my game so I bought a cabel to try it on a real phone, and as I expected my multitouch dosnt work. I use 2 joysticks, one to move my character and one to change his direction so he can shoot while walking backwards etc. my local variable: public void update(MotionEvent event) { if (event == null && lastEvent == null) { return; } else if (event == null && lastEvent != null) { event = lastEvent; } else { lastEvent = event; } int index = event.getActionIndex(); int pointerId = event.getPointerId(index); statement for left Joystick: if (pointerId == 0 && event.getAction() == MotionEvent.ACTION_DOWN && (int) event.getX() > steeringxMesh - 50 && (int) event.getX() < steeringxMesh + 50 && (int) event.getY() > yMesh - 50 && (int) event.getY() < yMesh + 50) { dragging = true; } else if (event.getAction() == MotionEvent.ACTION_UP) { dragging = false; } if (dragging) { //code for moving my character statement for my right joystick: if (pointerId == 1 && event.getAction() == MotionEvent.ACTION_DOWN && (int) event.getX() > shootingxMesh - 50 && (int) event.getX() < shootingxMesh + 50 && (int) event.getY() > yMesh - 50 && (int) event.getY() < yMesh + 50) { shooting = true; } else if (event.getAction() == MotionEvent.ACTION_UP) { shooting = false; } if (shooting) { // code for aiming } This class is my main-Views onTouchListener and is called in a update-method that gets called in my game-loop, so its called every frame. Im really at a loss here, I've done a couple of tutorials and Ive tried all relevant solutions to similar posts. Can post entire Class if necessary but I think this is all the relevant code. Just hope someone can make some sence out of this.

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• F# and the useful infinite Sequence (I think)

  - by MarkPearl

  So I have seen a few posts done by other F# fans on solving project Euler problems. They looked really interesting and I thought with my limited knowledge of F# I would attempt a few and the first one I had a look at was problem 5. Which said : “2520 is the smallest number that can be divided by each of the numbers from 1 to 10 without any remainder. What is the smallest number that is evenly divisible by all of the numbers from 1 to 20?” So I jumped into coding it and straight away got stuck – the C# programmer in me wants to do a loop, starting at one and dividing every number by 1 to 20 to see if they all divide and once a match is found, there is your solution. Obviously not the most elegant way but a good old brute force approach. However I am pretty sure this would not be the F# way…. So after a bit of research I found the Sequences and how useful they were. Sequences seemed like the beginning of an approach to solve my problem. In my head I thought - create a sequence, and then start at the beginning of it and move through it till you find a value that is divisible by 1 to 20. Sounds reasonable? So the question is begged - how would you create a sequence that you are sure will be large enough to hold the solution to the problem? Well… You can’t know! Some more googling and I found what I would call infinite sequences – something that looks like this… let nums = 1 |> Seq.unfold (fun i -> Some (i, i + 1))   My interpretation of this would be as follows… create a sequence, and whenever it is called add 1 to its size (I would appreciate someone helping me on wording this right functionally). Something that I don’t understand fully yet is the forward pipe operator (|>) which I think plays a key role in this code. With this in hand I was able to code a basic optimized solution to this problem. I’m going to go over it some more before I post the full code just in case!

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• Multi-threaded JOGL Problem

  - by moeabdol

  I'm writing a simple OpenGL application in Java that implements the Monte Carlo method for estimating the value of PI. The method is pretty easy. Simply, you draw a circle inside a unit square and then plot random points over the scene. Now, for each point that is inside the circle you increment the counter for in points. After determining for all the random points wither they are inside the circle or not you divide the number of in points over the total number of points you have plotted all multiplied by 4 to get an estimation of PI. It goes something like this PI = (inPoints / totalPoints) * 4. This is because mathematically the ratio of a circle's area to a square's area is PI/4, so when we multiply it by 4 we get PI. My problem doesn't lie in the algorithm itself; however, I'm having problems trying to plot the points as they are being generated instead of just plotting everything at once when the program finishes executing. I want to give the application a sense of real-time display where the user would see the points as they are being plotted. I'm a beginner at OpenGL and I'm pretty sure there is a multi-threading feature built into it. Non the less, I tried to manually create my own thread. Each worker thread plots one point at a time. Following is the psudo-code: /* this part of the code exists in display() method in MyCanvas.java which extends GLCanvas and implements GLEventListener */ // main loop for(int i = 0; i < number_of_points; i++){ RandomGenerator random = new RandomGenerator(); float x = random.nextFloat(); float y = random.nextFloat(); Thread pointThread = new Thread(new PointThread(x, y)); } gl.glFlush(); /* this part of the code exists in run() method in PointThread.java which implements Runnable */ void run(){ try{ gl.glPushMatrix(); gl.glBegin(GL2.GL_POINTS); if(pointIsIn) gl.glColor3f(1.0f, 0.0f, 0.0f); // red point else gl.glColor3f(0.0f, 0.0f, 1.0f); // blue point gl.glVertex3f(x, y, 0.0f); // coordinates gl.glEnd(); gl.glPopMatrix(); }catch(Exception e){ } } I'm not sure if my approach to solving this issue is correct. I hope you guys can help me out. Thanks.

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• Collision disturbing the jumping mechanic in java 2D game [on hold]

  - by user50931

  So I have been working on a 2D Java game recently and everything was going smoothly, until I reached a problem to do with the players jumping mechanic. So far I've got the player to jump a fixed rate and fall due to gravity. Hers my code for my Player class. public class Player extends GameObject { public Player(int x, int y, int width, int height, ObjectId id) { super(x, y, width, height, id); } @Override public void tick(ArrayList<GameObject> object) { if(go){ x+=vx; y+=vy; } if(vx <0){ facing =-1; }else if(vx >0) facing =1; checkCollision(object); checkStance(); } private void checkStance() { if(falling){ //gravity jumping = false; vy = speed/2; } if(jumping){ // Calculates how high jump should be vy = -speed*2; if(jumpY - y >= maxJumpHeight) falling =true; } } private void checkCollision(ArrayList<GameObject> object) { for(int i=0; i< object.size(); i++ ){ GameObject tempObject = object.get(i); if(tempObject.getId() == ObjectId.Ledge){ if(getBoundsTop().intersects(tempObject.getBoundsAll())){ //Top y = tempObject.getY() + tempObject.getBoundsAll().height; falling =true; } if(getBoundsRight().intersects(tempObject.getBoundsAll())){ // Right x = tempObject.getX() -width ; } if(getBoundsLeft().intersects(tempObject.getBoundsAll())){ //Left x = tempObject.getX() + tempObject.getWidth(); } if(getBoundsBottom().intersects(tempObject.getBoundsAll())){ //Bottom y = tempObject.getY() - height; falling =false; vy=0; }else{ falling =true; } } } } @Override public void render(Graphics g) { g.setColor(Color.BLACK); g.fillRect((int)x, (int)y, width, height); } @Override public Rectangle getBoundsAll() { return new Rectangle((int)x, (int)y,width,height); } public Rectangle getBoundsTop() { return new Rectangle((int) x , (int)y ,width,height/15); } public Rectangle getBoundsBottom() { return new Rectangle( (int)x , (int) y +height -(height /15),width,height/15); } public Rectangle getBoundsLeft() { return new Rectangle( (int) x , (int) y + height /10 ,width/8,height - (height /5)); } public Rectangle getBoundsRight() { return new Rectangle((int) x + width - (width/8) ,(int) y + height /10 ,width/8,height - height/5); } } My problem is when I add: else{ falling =true; } during the loop of the ArrayList to check collision, it stops the player from jumping and keeps him on the ground. I've tried to find a way around this but haven't had any luck. Any suggestions?

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• Brute force algorithm implemented for sudoku solver in C [closed]

  - by 0cool

  This is my code that I have written in C.. It could solve certain level of problems but not the harder one.. I could not locate the error in it, Can you please find that.. # include <stdio.h> # include "sudoku.h" extern int sudoku[size][size]; extern int Arr[size][size]; int i, j, n; int BruteForceAlgorithm (void) { int val; for (i=0; i<size; i++) { for (j=0; j<size; j++) { if (sudoku[i][j]==0) { for (n=1; n<nmax; n++) { val = check (i,j,n); if ( val == 1) { sudoku[i][j]=n; // output(); break; } else if ( val == 0 && n == nmax-1 ) get_back(); } } } } } int get_back (void) { int p,q; int flag=0; for ( p=i; p>=0; p-- ) { for (q=j; q>=0; q-- ) { flag=0; if ( Arr[p][q]==0 && !( p==i && q==j) ) { if ( sudoku[p][q]== nmax-1 ) sudoku[p][q]=0; else { n = sudoku[p][q]; sudoku[p][q]=0; i = p; j = q; flag = 1; break; } } } if ( flag == 1) break; } } Code description: Sudoku.h has definitions related to sudoku solver. 1. size = 9 nmax = 10 2. check(i,j,n) returns 1 if a number "n" can be placed at (i,j) or else "0". What does this code do ? The code starts iterating from sudoku[0][0] to the end... if it finds a empty cell ( we take cell having "0" ), it starts checking for n=1 to n=9 which can be put in that.. as soon as a number can be put in that which is checked by check() it assigns it and breaks from loop and starts finding another empty cell. In case for a particular cell if it doesn't find "n" which can be assigned to sudoku cell.. it goes back to the previous empty cell and start iterating from where it stopped and assigns the next value and continues, Here comes the function get_back(). it iterates back..

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• Threads slowing down application and not working properly

  - by Belgin

  I'm making a software renderer which does per-polygon rasterization using a floating point digital differential analyzer algorithm. My idea was to create two threads for rasterization and have them work like so: one thread draws each even scanline in a polygon and the other thread draws each odd scanline, and they both start working at the same time, but the main application waits for both of them to finish and then pauses them before continuing with other computations. As this is the first time I'm making a threaded application, I'm not sure if the following method for thread synchronization is correct: First of all, I use two global variables to control the two threads, if a global variable is set to 1, that means the thread can start working, otherwise it must not work. This is checked by the thread running an infinite loop and if it detects that the global variable has changed its value, it does its job and then sets the variable back to 0 again. The main program also uses an empty while to check when both variables become 0 after setting them to 1. Second, each thread is assigned a global structure which contains information about the triangle that is about to be rasterized. The structures are filled in by the main program before setting the global variables to 1. My dilemma is that, while this process works under some conditions, it slows down the program considerably, and also it fails to run properly when compiled for Release in Visual Studio, or when compiled with any sort of -O optimization with gcc (i.e. nothing on screen, even SEGFAULTs). The program isn't much faster by default without threads, which you can see for yourself by commenting out the #define THREADS directive, but if I apply optimizations, it becomes much faster (especially with gcc -Ofast -march=native). N.B. It might not compile with gcc because of fscanf_s calls, but you can replace those with the usual fscanf, if you wish to use gcc. Because there is a lot of code, too much for here or pastebin, I created a git repository where you can view it. My questions are: Why does adding these two threads slow down my application? Why doesn't it work when compiling for Release or with optimizations? Can I speed up the application with threads? If so, how? Thanks in advance.

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• How to chain actions/animations together and delay their execution?

  - by codinghands

  I'm trying to build a simple game with a number of screens - 'TitleScreen', 'LoadingScreen', 'PlayScreen', 'HighScoreScreen' - each of which has it's own draw & update logic methods, sprites, other useful fields, etc. This works well for me as a game dev beginner, and it runs. However, on my 'PlayScreen' I want to run some animations before the player gets control - dropping in some artwork, playing some sound effects, generally prettifying things a little. However, I'm not sure what the best way to chain animations / sound effects / other timed general events is. I could make an intermediary screen, 'PrePlayScreen', which simply has all of this hardcoded like so: Update(){ Animation anim1 = new Animation(.....); Animation anim2 = new Animation(.....); anim1.Run(); if(anim1.State == AnimationState.Complete) anim2.Run(); if(anim2.State == AnimationState.Complete) // Load 'PlayScreen' screen } But this doesn't seem so great - surely their must be a better way? I then thought, 'Hey - an AnimationManager! That'd be awesome!'. But then that creeping OOP panic set in as I thought about it some more. If I create the Animation in my Screen, then add it to the AnimationManager (which may or may not be a GameComponent hooked up to Update/Draw), how can I get 'back' to it? To signal commands like start / end / repeat? I'd still need to keep a reference to the object in my Screen so that I could still communicate with it once it's buried in the bosom of a List in my AnimationManager. This seems bad. I've also tried using events - call 'Update' on all the animations in the PlayScreen update loop, but crucially all of the animations have a bool flag ('Active') which determines whether they should begin. The first animation has this set to 'true', all others 'false'. On completion the first animation raises an event, which sets animation 2's bool flag to true (and so it then runs). Once animation 2 is complete another 'anim complete' event is raised, and the screen state changes. Considering the game I'm making is basically as simple as it gets I know I'm overthinking this... it's just the paradigm shift from web - game development is making me break out in a serious case of the stupids.

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• Are we queueing and serializing properly?

  - by insta

  We process messages through a variety of services (one message will touch probably 9 services before it's done, each doing a specific IO-related function). Right now we have a combination of the worst-case (XML data contract serialization) and best-case (in-memory MSMQ) for performance. The nature of the message means that our serialized data ends up about 12-15 kilobytes, and we process about 4 million messages per week. Persistent messages in MSMQ were too slow for us, and as the data grows we are feeling the pressure from MSMQ's memory-mapped files. The server is at 16GB of memory usage and growing, just for queueing. Performance also suffers when the memory usage is high, as the machine starts swapping. We're already doing the MSMQ self-cleanup behavior. I feel like there's a part we're doing wrong here. I tried using RavenDB to persist the messages and just queueing an identifier, but the performance there was very slow (1000 messages per minute, at best). I'm not sure if that's a result of using the development version or what, but we definitely need a higher throughput[1]. The concept worked very well in theory but performance was not up to the task. The usage pattern has one service acting as a router, which does all reads. The other services will attach information based on their 3rd party hook, and forward back to the router. Most objects are touched 9-12 times, although about 10% are forced to loop around in this system for awhile until the 3rd parties respond appropriately. The services right now account for this and have appropriate sleeping behaviors, as we utilize the priority field of the message for this reason. So, my question, is what is an ideal stack for message passing between discrete-but-LAN'ed machines in a C#/Windows environment? I would normally start with BinaryFormatter instead of XML serialization, but that's a rabbit hole if a better way is to offload serialization to a document store. Hence, my question. [1]: The nature of our business means the sooner we process messages, the more money we make. We've empirically proven that processing a message later in the week means we are less likely to make that money. While performance of "1000 per minute" sounds plenty fast, we really need that number upwards of 10k/minute. Just because I'm giving numbers in messages per week doesn't mean we have a whole week to process those messages.

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• Replication of lockoutTime attribute is not urgent on AD-LDS

  - by ixe013

  I have two LDS servers on the same subnet. They replicate well. If I change an attribute, it gets replicated after 15 seconds. LDS is configured to honor password policies. When a user makes too many wrong password attemps, his account is locked and that user's lockoutTime attribute is set accordingly. But lockoutTime is not replicated as urgent. In fact, it is not replicated unless there is another change somewhere in the directory. The lockoutTime attribute will be replicated. Here is an (edited Wireshark) trace. It shows normal replication trafic No. Time Protocol Length Info 133 16:23:02 DRSUAPI 562 DsGetNCChanges request 134 16:23:02 DRSUAPI 3042 DsGetNCChanges response 152 16:23:17 DRSUAPI 562 DsGetNCChanges request 157 16:23:17 DRSUAPI 242 DsGetNCChanges response 230 16:24:57 DRSUAPI 562 DsGetNCChanges request 231 16:24:57 DRSUAPI 2930 DsGetNCChanges response 246 16:25:12 DRSUAPI 562 DsGetNCChanges request Right after that, I lock the user (with a FOR loop and ldifde). Nothing happens, until I give up and change the description attribute on the user, then about 15 seconds later I see the replication go through. 1984 16:31:05 DRSUAPI 562 DsGetNCChanges request 1985 16:31:05 DRSUAPI 2930 DsGetNCChanges response The lockoutTime and description is replicated. As stated here, if I set lockoutTime to 0, replication occurs after 15 seconds ! I have enabled replication diagnostics, but nothing shows up in the instance's logs - strange. I have enabled change notification between sites, restarted both services, but I did not see any changes. How can I make the lockoutTime replication urgent ?

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• Cisco ASA and SixXS IPv6 tunnel endpoint?

  - by Martijn Heemels

  I recently installed a Cisco ASA 5505 firewall on the edge of our LAN. The setup is simple: Internet <-- ASA <-- LAN I would like provide the hosts in the LAN with IPv6 connectivity by setting up a 6in4 tunnel to SixXS. It would be nice to have the ASA as tunnel endpoint so it can firewall both IPv4 and IPv6 traffic. Unfortunately the ASA apparently can't create a tunnel itself, and can't port-forward protocol 41 traffic, so I believe I would have to do one of the following instead: Set up a host with it's own IP outside the firewall, and have that function as tunnel-endpoint. The ASA can then firewall and route the v6 subnet to the LAN. Set up a host inside the firewall that functions as endpoint, separated via vlan or whatever, and loop the traffic back into the ASA where it can be firewalled and routed. This seems contrived, but would allow me to use a VM instead of a physical machine as endpoint. Any other way? What would you suggest is the optimal way to set this up? P.S. I do have a spare public IP address available if needed, and can spin up another VM in our VMware infrastructure.

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• Disable raid member check upon mount to mount damaged nvidia raid1 member

  - by Halfgaar

  Hi, A friend of mine destroyed his Nvidia RAID1 array somehow and in trying to fix it, he ended up with a non-working array. Because of the RAID metadata, the actual disk data was stored at an offset from the beginning. I was able to identify this offset with dd and a hexeditor and then I used losetup to create a loop device with the proper offset, so that I could mount the partition. It was then that I ran into problems, namely that mount says: "mount: unknown filesystem type 'nvidia_raid_member'". I also had this when trying to mount a Linux MD component the other day, and because I can remember that doing that in the past worked, I surmised that it may be some kind of protection. I therefore booted an old Sysrescue CD and tried it there, which worked (because of the older version of mount/libc/kernel/whatever). I still need to try to get more data, and because I don't want to keep using that SysrecueCD, I'd like to be able to mount the disk on my normal system. So, my question is: can the check for a disk being a raid member be disabled? I guess I could also zero out blocks that look like the raid block, but I'd rather not... I made an image of the disk with par2 data, so it's revertable, but still...

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• Basic 301 Redirection Help

  - by Marc

  I am trying to learn redirection for a WordPress site of my own. I am testing the concept of redirecting a single WordPress post by using a dummy site. However, it doesn't seem to be working for me. I am trying to redirect www.perfectmatchmaker[dot]org/finding-the-right-matchmaker to www.perfectmatchmaker[dot]org/finding-the-perfect-matchmaker I read that using the following is how to do this: Redirect 301 /old.html http://www.you[dot]com/new.html So this is what my .htaccess file currently looks like: # Use PHP5 as default AddHandler application/x-httpd-php5 .php # BEGIN WordPress <IfModule mod_rewrite.c> RewriteEngine On RewriteBase / RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule . /index.php [L] </IfModule> # END WordPress Redirect 301 /finding-the-right-matchmaker.html http://www.perfectmatchmaker.org/finding-the-perfect-matchmaker.html I've also tried removing the ".html". The redirection of the URL is finally working, but the URL shows no posts available. If I try to redirect the other post on the site by adding the following on the next line of the .htaccess file, I get an error that there is a "redirect loop" occurring. redirect 301 /find-love-and-your-perfect-match-through-the-use-of-a-match-maker http://www.perfectmatchmaker.org/find-love-and-your-perfect-match Any help you can provide me would be much appreciated. Thanks! Marc

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• PostgreSQL lots of writes

  - by strife911

  Hi, I am using postgreSQL for a scientific application (unsupervised clustering). The python program is multi-threaded so that each thread manages its own postmaster process (one per core). Hence, their is a lot of concurrency. Each thread-process loop infinitely though two SQL queries. The first is for reading, the second is for writing. The read operation considers 500 time the amount of rows the write operation considers. Here is the output of dstat: ----total-cpu-usage---- ------memory-usage----- -dsk/total- --paging-- --io/total- usr sys idl wai hiq siq| used buff cach free| read writ| in out | read writ 4 0 32 64 0 0|3599M 63M 57G 1893M|1524k 16M| 0 0 | 98 2046 1 0 35 64 0 0|3599M 63M 57G 1892M|1204k 17M| 0 0 | 68 2062 2 0 32 66 0 0|3599M 63M 57G 1890M|1132k 17M| 0 0 | 62 2033 2 1 32 65 0 0|3599M 63M 57G 1904M|1236k 18M| 0 0 | 80 1994 2 0 31 67 0 0|3599M 63M 57G 1903M|1312k 16M| 0 0 | 70 1900 2 0 37 60 0 0|3599M 63M 57G 1899M|1116k 15M| 0 0 | 71 1594 2 1 37 60 0 0|3599M 63M 57G 1898M| 448k 17M| 0 0 | 39 2001 2 0 25 72 0 0|3599M 63M 57G 1896M|1192k 17M| 0 0 | 78 1946 1 0 40 58 0 0|3599M 63M 57G 1895M| 432k 15M| 0 0 | 38 1937 I am pretty sure I could write more often than that for I have seen it write up to 110-140M on dstat. How can I optimize this process?

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• Proliant RAID 1 Rebuild Questions

  - by Nicholas

  I have a HP Proliant ML350 G5 server that experienced a power supply failure overnight. The power supply was replaced but unfortunately it got restarted with only 1 disk in the RAID 1 set plugged in. (The raid controller is the build in E200i). The raid BIOS then said on start-up that it had entered Interim Recovery Mode. However I would have expected it to still start up with only the 1 drive. The bios however says that it cannot find a C: drive and enters a reboot loop polling the other boot devices. First question is, is this normal behaviour not to start up on 1 disk? The second drive was then plugged in (all drives are ok) and the raid bios started an automatic rebuild on that disk. This appears to be a background process as there is no progress shown. However based on the light flashing it looks like it is working. My second question is how long will this rebuild take? (36GB 15K SAS drive). I cannot see any error messages and it looks like it is rebuilding the drive ok, but the computer still will not start-up. It still says during the boot up process that the C: drive is not found. If I wait for the rebuild to finish, is it likely to fix itself and find the C: drive? Or is there some other problem here?

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• Throttling Postfix memory

  - by teddybeard

  I have a VPS on 1and1 similar to this configuration (512MB, burst up to 2GB). I run a web service where I crawl the web and notify my users through email and sms when a certain online data feed changes. When I send the emails out, I just have PHP loop through the recipients list and send the emails out using the mail() function. Whenever I try to send a large volume of these messages out, my server starts acting funny. I can't even run an 'ls' sometimes because the shell tells me it 'cannot allocate memory'. The shell is unusable and yet my website is being served up fine. Mail.err contains: Nov 14 17:30:09 s15351477 postfix/smtp[26000]: fatal: inet_addr_local[getifaddrs]: getifaddrs: Cannot allocate memory Nov 14 17:30:09 s15351477 postfix/sendmail[25999]: fatal: username(1000): unable to execute /usr/sbin/postdrop -r: Success Nov 14 18:29:14 s15351477 postfix/smtp[9911]: fatal: inet_addr_local[getifaddrs]: getifaddrs: Cannot allocate memory Nov 14 18:29:14 s15351477 postfix/sendmail[9910]: fatal: username(1000): unable to execute /usr/sbin/postdrop -r: Success Also, if relevant, my bean counters are: Version: 2.5 uid resource held maxheld barrier limit failcnt 53907331: kmemsize 20779422 21041560 31457280 34603008 2989403 lockedpages 0 0 512 512 0 privvmpages 81488 82498 524288 576716 94640 shmpages 2831 2831 32768 32768 0 dummy 0 0 9223372036854775807 9223372036854775807 0 numproc 90 91 128 128 6603 physpages 32692 33531 2147483647 2147483647 0 vmguarpages 0 0 131072 2147483647 0 oomguarpages 32942 33781 9223372036854775807 2147483647 0 numtcpsock 22 23 720 720 0 numflock 27 28 376 413 0 numpty 1 1 32 32 0 numsiginfo 0 1 512 512 0 tcpsndbuf 425888 441064 3440640 5406720 0 tcprcvbuf 369200 376832 3440640 5406720 0 othersockbuf 268000 268464 2252160 4194304 0 dgramrcvbuf 0 8472 524288 576716 0 numothersock 180 182 720 720 0 dcachesize 952146 966231 5242880 5767168 0 numfile 3609 3683 8192 8192 0 dummy 0 0 0 0 0 dummy 0 0 0 0 0 dummy 0 0 0 0 0 numiptent 25 25 200 205 0 Is there some way I can throttle postfix to keep it from swamping the system like this? Also wondering: why does email use so many resources, these emails are just short text?

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• ./rtnet start rteth0-mac: unknown interface: No such device ioctl: No such device

  - by Anisha Kaul

  I have installed the RTnet over Xenomai. RTnet compiled well, and I also tested loopback on the single machine and was able to ping. However I noticed ./rtnet start showing the following output: What should I interpret when all it says is "no such device"? What more info should I provide here for you to help me in getting rid of this error? linux-y3pi:/usr/local/rtnet/sbin # ./rtnet start rteth0: unknown interface: No such device rteth0-mac: unknown interface: No such device ioctl: No such device ioctl: No such device ioctl: No such device ioctl: No such device ioctl (add): No such device vnic0: unknown interface: No such device SIOCSIFADDR: No such device vnic0: unknown interface: No such device SIOCSIFNETMASK: No such device Waiting for all slaves...ioctl: No such device ioctl: No such device linux-y3pi:/usr/local/rtnet/sbin # lsmod: linux-y3pi:/usr/local/rtnet/sbin # lsmod Module Size Used by tdma 18281 0 rtmac 9274 1 tdma rtcfg 49485 0 rtcap 7216 0 rt_loopback 1563 2 rtpacket 5517 0 rtudp 10655 0 rt_8139too 11374 0 rtipv4 22842 2 rtcfg,rtudp rtnet 42130 9 tdma,rtmac,rtcfg,rtcap,rt_loopback,rtpacket,rtudp,rt_8139too,rtipv4 ip6t_LOG 8480 6 xt_tcpudp 3540 2 xt_pkttype 1176 3 ipt_LOG 8201 6 xt_limit 2159 12 snd_pcm_oss 44878 0 snd_mixer_oss 15151 1 snd_pcm_oss snd_seq 55731 0 s nd_seq_device 6698 1 snd_seq edd 8407 0 ip6t_REJECT 4306 3 nf_conntrack_ipv6 8186 4 nf_defrag_ipv6 10128 1 nf_conntrack_ipv6 ip6table_raw 1451 1 xt_NOTRACK 1112 4 ipt_REJECT 2397 3 xt_state 1314 8 iptable_raw 1478 1 iptable_filter 1706 1 ip6table_mangle 1756 0 nf_conntrack_netbios_ns 1678 0 nf_conntrack_ipv4 8957 4 nf_conntrack 80411 5 nf_conntrack_ipv6,xt_NOTRACK,xt_state,nf_conntrack_netbios_ns,nf_conntrack_ipv4 nf_defrag_ipv4 1561 1 nf_conntrack_ipv4 ip_tables 18872 2 iptable_raw,iptable_filter ip6table_filter 1679 1 ip6_tables 19066 4 ip6t_LOG,ip6table_raw,ip6table_mangle,ip6table_filter x_tables 24094 16 ip6t_LOG,xt_tcpudp,xt_pkttype,ipt_LOG,xt_limit,ip6t_REJECT,ip6table_raw,xt_NOTRACK,ipt_REJECT,xt_state,iptable_raw,iptable_filter,ip6table_mangle,ip_tables,ip6table_filter,ip6_tables fuse 69279 3 loop 17417 0 dm_mod 71671 0 snd_hda_codec_via 57768 1 snd_hda_intel 24871 2 snd_hda_codec 95006 2 snd_hda_codec_via,snd_hda_intel snd_hwdep 6540 1 snd_hda_codec snd_pcm 90716 3 snd_pcm_oss,snd_hda_intel,snd_hda_codec snd_timer 22050 2 snd_seq,snd_pcm snd 71410 14 snd_pcm_oss,snd_mixer_oss,snd_seq,snd_seq_device,snd_hda_codec_via,snd_hda_intel,snd_hda_codec,snd_hwdep,snd_pcm,snd_timer soundcore 7854 1 snd iTCO_wdt 11716 0 iTCO_vendor_support 2942 1 iTCO_wdt snd_page_alloc 8324 2 snd_hda_intel,snd_pcm sr_mod 13186 0 cdrom 37628 1 sr_mod i2c_i801 9677 0 pcspkr 1950 0 sg 28847 0 serio_raw 4534 0 ext4 361361 2 jbd2 82943 1 ext4 crc16 1699 1 ext4 i915 500199 2 drm_kms_helper 33537 1 i915 drm 211193 3 i915,drm_kms_helper sd_mod 33977 5 i2c_algo_bit 5625 1 i915 intel_agp 11529 1 i915 intel_gtt 16397 3 i915,intel_agp ata_generic 3787 0 ata_piix 22875 4 ahci 20097 0 libahci 22089 1 ahci libata 194812 4 ata_generic,ata_piix,ahci,libahci scsi_mod 204709 4 sr_mod,sg,sd_mod,libata linux-y3pi:/usr/local/rtnet/sbin #

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• How does it hurt to use Linux (Ubuntu) as a guest OS for all my tasks?

  - by sauparna

  I have a machine running Windows, where the disk has two partitions C (50 GB) and D (250GB). I do research in Information Retrieval and need to work with a large corpus (more than 50 GB) and in Linux. So if I want to install Linux on the existing system, keeping the Windows installation intact, will it be fine to run it in a virtual box? (say, QEMU, VMWare, etc.) An alternative is using Wubi. In that case the Linux installation has to be on drive C. Then, if I keep a small Linux installation (say 5GB) on C, and my corpus on D (mounted in Linux), how will it affect the performance of my programs which would be accessing the mounted Windows drive D. Is it feasible to use Linux this way? Which of the above is better if at all they are a way out? Note : Since my post in July 2010, I have been using and have tried several ways of maintaining a disk-image that I can mount in Linux. I had a 100GB qcow2 disk and a 100GB raw disk, both formatted to an EXT3 file system. I was mounting and connecting to the qcow2 disk using qemu-nbd. The problem was that every now and then, the connection to the disk would get lost and the running programs would throw disk I/O errors. The raw disk would mount and work fine as a loop mounted device, but when writing data to it, the mount.ntfs program would hog the CPU and the process would take an enormous amount of time. I was in fact running make on a piece of software located on this raw disk, and after a point of time make was waiting while mount.ntfs would show 100% CPU usage.

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• How do I fix this Windows 7 wireless connectivity issue?

  - by Charles Randall

  I have a laptop with an Intel Wireless Centrino 6300 module. Recently, the machine has stopped properly connecting to my wireless router. It will get stuck in a loop of connecting, then disconnecting and reconnecting. While connected, it will simply say "No Internet Access." Running inSSIDer 2.0, it shows my network jumping around between two channels -- I know this isn't the case, because I've set my router to sit on one single channel. My MacBook Pro, Boxee Box, PS3, and Xbox 360 all connect fine to the wireless and have no problems at all. I know it's not the wireless module, as I bought a second one recently assuming the first had died -- but I get the same behavior with both. Sometimes, I can fix the issue temporarily by deleting the network (Using the Manage Wireless Networks page), and then re-adding it (via standard wireless methods). Then it will work for a few days. But inevitably the problem comes back, and now the laptop simply won't connect to the wireless at all, even if I take steps that usually work. Since I've ruled out the hardware, and it's unlikely some kind of interference issue (because I would expect to see it on any multitude of other devices), I would think at this point that it's a problem with Windows itself. One thing that might be a hint, even though I delete the network, when I add it again, it's always listed as "Wireless Network Connection 2" even though there isn't another in the list.

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• mod_proxy incorrect redirect behaviour

  - by Kevin Loney

  In chrome this configuration causes an infinite redirect loop and in every other browser I have tried a request for https://www.example.com/servlet/foo is resulting in a redirect to https://www.example.com/foo/ instead of https://www.example.com/servlet/foo/ however this only occurs when I do not include a trailing / at the end of the request url (i.e. http://www.flightboard.net/servlet/foo/ works just fine). <VirtualHost *:80> # ... RewriteEngine On RewriteCond %{HTTPS} off RewriteCond %{REQUEST_URI} ^/servlet(/.*)?$ RewriteRule ^(.*)$ http://%{HTTP_HOST}$1 [R=301,L] </VirtualHost> <VirtualHost *:443> # ... ProxyPass /servlet/ ajp://localhost:8009/ ProxyPassReverse /servlet/ ajp://localhost:8009/ </VirtualHost> The virtual host on port 443 has no rewrite rules that could possibly causing the problem, the tomcat contexts being referenced do not send any redirects, and if I change the ProxyPass and ProxyPassReverse directives to: ProxyPass / ajp://localhost:8009/ ProxyPassReverse / ajp://localhost:8009/ everything works fine (except for the fact everything from www.example.com is being passed to the proxy which is not the behaviour I want). I'm fairly certain this is a problem with the way I have my proxy settings configured because I did log all the rewrite output coming from apache and it was all correct.

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• Broken UAC, cant edit File/folders or change settings in user account

  - by Antoros

  It appears that UAC is broken cant move/delete some file/folders, when asked to use administrative right (and say yes) it shows the loading bar and then nothings gets moved/deleted, no error whatsoever opened control panel, user account and when i click on any option with the Shield (administrative rights) the mouse changes to loading and thengo back to normal, not opening any menu or showing any error Already done a sfc /scannow , no errors found Already used Microsoft's Fix it, reclycle bin broken and repaired, still the same error Used microsoftaccounts tool , this are the errors i got: Problem with microsoft account policy... <- this is the problem (didint fix) Trust this PC <- loop of redirections, cant get to trust this pc (only one with w8) Problems witht sytem registration : i think it is because of the soft system reset Some setting have sync turned off : i never configured anything to sync Rootcauses found and created logs : would like to know where the logs are saved... had to use a ".reg" file to change uac setting to never notify, thinking it would fix this, no, it stoped asking though, i can still open a cmd with Administrative rights, but cant access to UAC settings Accesed Administrator account (net user administrator /active:yes)and even with that account could change any settings so there it is, dont know what else to do in the moment (this pc broke with 8.1 update and was restored to factory configuration, it broke several drivers and kept most of the registry entries, i cant find the cause of this problem. other info: i tried to delete a file in a program folder and couldnt, downloaded unlocker to check first if it was permissions but no, it showed me a msg telling me that there wasnt any error, and if i would like to delete it, clicked on yes, and it did delete it, what amuses me is that i cant without this tool, not even using the feature that takes over ownership Edit: wow, in a not crappy pc chkdsk is fast, completed with no errors found : /

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• Cisco ASA and static IPv6 tunnel endpoint?

  - by Martijn Heemels

  I recently installed a Cisco ASA 5505 firewall on the edge of our LAN. The setup is simple: Internet <-- ASA <-- LAN I would like provide the hosts in the LAN with IPv6 connectivity by setting up a 6in4 tunnel to SixXS. It would be nice to have the ASA as tunnel endpoint so it can firewall both IPv4 and IPv6 traffic. Unfortunately the ASA apparently can't create a tunnel itself, and can't port-forward protocol 41 traffic, so I believe I would have to do one of the following instead: Set up a host with it's own IP outside the firewall, and have that function as tunnel-endpoint. The ASA can then firewall and route the v6 subnet to the LAN. Set up a host inside the firewall that functions as endpoint, separated via vlan or whatever, and loop the traffic back into the ASA where it can be firewalled and routed. This seems contrived, but would allow me to use a VM instead of a physical machine as endpoint. Any other way? What would you suggest is the optimal way to set this up? P.S. I do have a spare public IP address available if needed, and can spin up another VM in our VMware infrastructure.

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• MySQL replication - rapidly growing relay bin logs

  - by Rob Forrest

  Morning all, I've got a really strange situation here this morning much like a reportedly fixed MySQL bug. http://bugs.mysql.com/bug.php?id=28421 My relay bin logs are rapidly filling with an infinite loop of junk made of this sort of thing. #121018 5:40:04 server id 101 end_log_pos 15598207 #Append_block: file_id: 2244 block_len: 8192 # at 15598352 #121018 5:40:04 server id 101 end_log_pos 15606422 #Append_block: file_id: 2244 block_len: 8192 # at 15606567 ... # at 7163731 #121018 5:38:39 server id 101 end_log_pos 7171801 #Append_block: file_id: 2243 block_len: 8192 WARNING: Ignoring Append_block as there is no Create_file event for file_id: 2243 # at 7171946 #121018 5:38:39 server id 101 end_log_pos 7180016 #Append_block: file_id: 2243 block_len: 8192 WARNING: Ignoring Append_block as there is no Create_file event for file_id: 2243 These log files grow to 1Gb within about a minute before rotating and starting again. These big files are interspersed with 1 or 2 smaller files with just this in /*!40019 SET @@session.max_insert_delayed_threads=0*/; /*!50003 SET @OLD_COMPLETION_TYPE=@@COMPLETION_TYPE,COMPLETION_TYPE=0*/; DELIMITER /*!*/; # at 4 #121023 9:43:05 server id 100 end_log_pos 106 Start: binlog v 4, server v 5.1.61-log created 121023 9:43:05 BINLOG ' mViGUA9kAAAAZgAAAGoAAAAAAAQANS4xLjYxLWxvZwAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAEzgNAAgAEgAEBAQEEgAAUwAEGggAAAAICAgC '/*!*/; # at 106 #121023 9:43:05 server id 100 end_log_pos 156 Rotate to mysqld-relay-bin.000003 pos: 4 DELIMITER ; # End of log file ROLLBACK /* added by mysqlbinlog */; /*!50003 SET COMPLETION_TYPE=@OLD_COMPLETION_TYPE*/; We're running a master-master replication setup with the problematic server running mysql 5.1.61. The other server which is, for the moment, stable is running 5.1.58. Has anyone got any ideas what the solution is to this and moreover, what might have caused this?

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