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• apt-get upgrade stuck at the same package (openjdk-6-jre-headless)

  - by decibyte

  I'm stuck, can't upgrade my system. Running sudo apt-get upgrade gives me the following: mmm@alalunga:~$ sudo apt-get upgrade Reading package lists... Done Building dependency tree Reading state information... Done The following packages have been kept back: ginn libgrip0 linux-generic-pae linux-headers-generic-pae linux-image-generic-pae The following packages will be upgraded: apport apport-gtk bind9-host build-essential dhcp3-client dhcp3-common dnsutils eog evince evince-common firefox firefox-branding firefox-dbg firefox-globalmenu firefox-gnome-support firefox-locale-en gimp gimp-data gir1.2-totem-1.0 glib-networking glib-networking-common glib-networking-services gnupg gpgv icedtea-6-jre-cacao icedtea-6-jre-jamvm icedtea-6-plugin icedtea-netx icedtea-netx-common icedtea-plugin isc-dhcp-client isc-dhcp-common libapache2-mod-php5 libart-2.0-2 libbind9-80 libdns81 libevince3-3 libgimp2.0 libisc83 libisccc80 libisccfg82 liblwres80 libssl-dev libssl-doc libssl1.0.0 libtotem0 linux-firmware linux-libc-dev openjdk-6-jre openjdk-6-jre-headless openjdk-6-jre-lib openssl php-pear php5-cli php5-common php5-curl php5-dev php5-gd php5-mysql php5-xsl policykit-1-gnome python-apport python-django python-gst0.10 python-problem-report resolvconf thunderbird thunderbird-globalmenu thunderbird-gnome-support totem totem-common totem-mozilla totem-plugins xserver-xorg-input-synaptics 74 upgraded, 0 newly installed, 0 to remove and 5 not upgraded. Need to get 317 MB/327 MB of archives. After this operation, 1.481 kB of additional disk space will be used. Do you want to continue [Y/n]? Get:1 http://archive.ubuntu.com/ubuntu/ precise-updates/main openjdk-6-jre-headless i386 6b24-1.11.4-1ubuntu0.12.04.1 [27,3 MB] Get:2 http://archive.ubuntu.com/ubuntu/ precise-updates/main openjdk-6-jre-headless i386 6b24-1.11.4-1ubuntu0.12.04.1 [27,3 MB] Get:3 http://archive.ubuntu.com/ubuntu/ precise-updates/main openjdk-6-jre-headless i386 6b24-1.11.4-1ubuntu0.12.04.1 [27,3 MB] Get:4 http://archive.ubuntu.com/ubuntu/ precise-updates/main openjdk-6-jre-headless i386 6b24-1.11.4-1ubuntu0.12.04.1 [27,3 MB] Get:5 http://archive.ubuntu.com/ubuntu/ precise-updates/main openjdk-6-jre-headless i386 6b24-1.11.4-1ubuntu0.12.04.1 [27,3 MB] Get:6 http://archive.ubuntu.com/ubuntu/ precise-updates/main openjdk-6-jre-headless i386 6b24-1.11.4-1ubuntu0.12.04.1 [27,3 MB] Get:7 http://archive.ubuntu.com/ubuntu/ precise-updates/main openjdk-6-jre-headless i386 6b24-1.11.4-1ubuntu0.12.04.1 [27,3 MB] 9% [7 openjdk-6-jre-headless 27,3 MB/27,3 MB 100%] It keeps downloading the package openjdk-6-jre-headless, then does nothing for a while (hanging on what's the last line above), then download the package again. It's at its 13th download attempt at the moment of writing. The actual downloads seem to be done just fine, but whatever it does after downloading seems to be failing. I tried removing openjdk-6, but then it wanted to install openjdk-7 instead, with the same result, hanging at openjdk-7-jre-headless instead. I also tried changing servers from my local (Danish) to the main server. No luck. It's also keeping me from upgrading alle the other packages. What to do?

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• Wrong statistics in AUX_STATS$ might puzzle the optimizer

  - by Mike Dietrich

  We do recommend the creation of System Statistics for quite a long time. Since Oracle 9i the optimizer works with a CPU and IO cost based model. And in order to give the optimizer some knowledge about the IO subsystem's performance and throughput - once System Statistics are collected - they'll get stored in AUX_STATS$. For this purpose in the old Oracle 9i days some default values had been defined - and you'll still find those defaults in Oracle Database 11g Release 2 in AUX_STATS$. But these old values don't reflect the performance of modern IO systems. So it might be a good best practice post upgrade to create fresh System Statistics if you haven't done this before.  You can collect System Statistics with: exec DBMS_STATS.GATHER_SYSTEM_STATS('start'); and end it later by executing: exec DBMS_STATS.GATHER_SYSTEM_STATS('stop'); You could also run DBMS_STATS.GATHER_SYSTEM_STATS('interval', interval=>N) instead where N is the number of minutes when statistics gathering is stopped automatically. Please make sure you'll do this on a real workload period. It won't make sense to gather these values while the database is in an idle state. You should do this ideally for several hours. It doesn't affect performance in a negative way as the values are anyway collected in V$SYSSTAT and V$SESSTAT. And in case you'd like to delete the stats and revert to the old default values you'd simply execute:exec DBMS_STATS.DELETE_SYSTEM_STATS; The tricky thing in Oracle Database 11.2 - and that's why I'm actually writing this blog post today - is bug9842771. This leads to wrong values in AUX_STATS$ for SREADTIM and MREADTIM by factor 1000 guiding the optimizer sometimes into the totally wrong directon. The workaround is to overwrite these values manually and divide them by 1000. Use the DBMS_STATS.SET_SYSTEM_STATS procedure. See this MOS Note:9842771.8 for the above bug for some further information. This issue is fixed in Oracle Database 11.2.0.3 and above. To get some background information about the statistics collected in please read this section in the Oracle Database 11.2 Performance Tuning Guide. And gathering System Statistics might have some implication if you have mixed workloads - and interacts with DB_FILE_MULTIBLOCK_READ_COUNT. For more information please read section 13.4.1.2.

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• Correct use of VAO's in OpenGL ES2 for iOS?

  - by sak

  I'm migrating to OpenGL ES2 for one of my iOS projects, and I'm having trouble to get any geometry to render successfully. Here's where I'm setting up the VAO rendering: void bindVAO(int vertexCount, struct Vertex* vertexData, GLushort* indexData, GLuint* vaoId, GLuint* indexId){ //generate the VAO & bind glGenVertexArraysOES(1, vaoId); glBindVertexArrayOES(*vaoId); GLuint positionBufferId; //generate the VBO & bind glGenBuffers(1, &positionBufferId); glBindBuffer(GL_ARRAY_BUFFER, positionBufferId); //populate the buffer data glBufferData(GL_ARRAY_BUFFER, vertexCount, vertexData, GL_STATIC_DRAW); //size of verte position GLsizei posTypeSize = sizeof(kPositionVertexType); glVertexAttribPointer(kVertexPositionAttributeLocation, kVertexSize, kPositionVertexTypeEnum, GL_FALSE, sizeof(struct Vertex), (void*)offsetof(struct Vertex, position)); glEnableVertexAttribArray(kVertexPositionAttributeLocation); //create & bind index information glGenBuffers(1, indexId); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, *indexId); glBufferData(GL_ELEMENT_ARRAY_BUFFER, vertexCount, indexData, GL_STATIC_DRAW); //restore default state glBindVertexArrayOES(0); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0); glBindBuffer(GL_ARRAY_BUFFER, 0); } And here's the rendering step: //bind the frame buffer for drawing glBindFramebuffer(GL_FRAMEBUFFER, outputFrameBuffer); glClear(GL_COLOR_BUFFER_BIT); //use the shader program glUseProgram(program); glClearColor(0.4, 0.5, 0.6, 0.5); float aspect = fabsf(320.0 / 480.0); GLKMatrix4 projectionMatrix = GLKMatrix4MakePerspective(GLKMathDegreesToRadians(65.0f), aspect, 0.1f, 100.0f); GLKMatrix4 modelViewMatrix = GLKMatrix4MakeTranslation(0.0f, 0.0f, -1.0f); GLKMatrix4 mvpMatrix = GLKMatrix4Multiply(projectionMatrix, modelViewMatrix); //glUniformMatrix4fv(projectionMatrixUniformLocation, 1, GL_FALSE, projectionMatrix.m); glUniformMatrix4fv(modelViewMatrixUniformLocation, 1, GL_FALSE, mvpMatrix.m); glBindVertexArrayOES(vaoId); glDrawElements(GL_TRIANGLE_FAN, kVertexCount, GL_FLOAT, &indexId); //bind the color buffer glBindRenderbuffer(GL_RENDERBUFFER, colorRenderBuffer); [context presentRenderbuffer:GL_RENDERBUFFER]; The screen is rendering the color passed to glClearColor correctly, but not the shape passed into bindVAO. Is my VAO being built correctly? Thanks!

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• How to update off screen bitmap in a surfaceview thread

  - by DKDiveDude

  I have a Surfaceview thread and an off canvas texture bitmap that is being generated (changed), first row (line), every frame and then copied one position (line) down on regular surfaceview bitmap to make a scrolling effect, and I then continue to draw other things on top of that. Well that is what I really want, however I can't get it to work even though I am creating a separate canvas for off screen bitmap. It is just not scrolling at all. I other words I have a memory bitmap, same size as Surfaceview canvas, which I need to scroll (shift) down one line every frame, and then replace top line with new random texture, and then draw that on regular Surfaceview canvas. Here is what I thought would work; My surfaceChanged where I specify bitmap and canvasses and start thread: @Override public void surfaceCreated(SurfaceHolder holder) { intSurfaceWidth = mSurfaceView.getWidth(); intSurfaceHeight = mSurfaceView.getHeight(); memBitmap = Bitmap.createBitmap(intSurfaceWidth, intSurfaceHeight, Bitmap.Config.ARGB_8888); memCanvas = new Canvas(memCanvas); myThread = new MyThread(holder, this); myThread.setRunning(true); blnPause = false; myThread.start(); } My thread, only showing essential middle running part: @Override public void run() { while (running) { c = null; try { // Lock canvas for drawing c = myHolder.lockCanvas(null); synchronized (mSurfaceHolder) { // First draw off screen bitmap to off screen canvas one line down memCanvas.drawBitmap(memBitmap, 0, 1, null); // Create random one line(row) texture bitmap memTexture = Bitmap.createBitmap(imgTexture, 0, rnd.nextInt(intTextureImageHeight), intSurfaceWidth, 1); // Now add this texture bitmap to top of off screen canvas and hopefully bitmap memCanvas.drawBitmap(textureBitmap, intSurfaceWidth, 0, null); // Draw above updated off screen bitmap to regular canvas, at least I thought it would update (save changes) shifting down and add the texture line to off screen bitmap the off screen canvas was pointing to. c.drawBitmap(memBitmap, 0, 0, null); // Other drawing to canvas comes here } finally { // do this in a finally so that if an exception is thrown // during the above, we don't leave the Surface in an // inconsistent state if (c != null) { myHolder.unlockCanvasAndPost(c); } } } } For my game Tunnel Run. Right now I have a working solution where I instead have an array of bitmaps, size of surface height, that I populate with my random texture and then shift down in a loop for each frame. I get 50 frames per second, but I think I can do better by instead scrolling bitmap.

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• The Buzz at the JavaOne Bookstore

  - by Janice J. Heiss

  I found my way to the JavaOne bookstore, a hub of activity. Who says brick and mortar bookstores are dead? I asked what was hot and got two answers: Hadoop in Practice by Alex Holmes was doing well. And Scala for the Impatient by noted Java Champion Cay Horstmann also seemed to be a fast seller. Hadoop in PracticeHadoop is a framework that organizes large clusters of computers around a problem. It is touted as especially effective for large amounts of data, and is use such companies as  Facebook, Yahoo, Apple, eBay and LinkedIn. Hadoop in Practice collects nearly 100 Hadoop examples and presents them in a problem/solution format with step by step explanations of solutions and designs. It’s very much a participatory book intended to make developers more at home with Hadoop.The author, Alex Holmes, is a senior software engineer with more than 15 years of experience developing large-scale distributed Java systems. For the last four years, he has gained expertise in Hadoop solving Big Data problems across a number of projects. He has presented at JavaOne and Jazoon and is currently a technical lead at VeriSign.At this year’s JavaOne, he is presenting a session with VeriSign colleague, Karthik Shyamsunder called “Java: A Perfect Platform for Data Science” where they will explain how the Java platform has emerged as a perfect platform for practicing data science, and also talk about such technologies as Hadoop, Hive, Pig, HBase, Cassandra, and Mahout. Scala for the ImpatientSan Jose State University computer science professor and Java Champion Cay Horstmann is the principal author of the highly regarded Core Java. Scala for the Impatient is a basic, practical introduction to Scala for experienced programmers. Horstmann has a presentation summarizing the themes of his book on at his website. On the final page he offers an enticing summary of his conclusions:* Widespread dissatisfaction with Java + XML + IDEs               --Don't make me eat Elephant again * A separate language for every problem domain is not efficient               --It takes time to master the idioms* ”JavaScript Everywhere” isn't going to scale* Trend is towards languages with more expressive power, less boilerplate* Will Scala be the “one ring to rule them”?* Maybe              --If it succeeds in industry             --If student-friendly subsets and tools are created The popularity of both books echoed comments by IBM Distinguished Engineer Jason McGee who closed his part of the Sunday JavaOne keynote by pointing out that the use of Java in complex applications is increasingly being augmented by a host of other languages with strong communities around them – JavaScript, JRuby, Scala, Python and so forth. Java developers increasingly must know the strengths and weaknesses of such languages going forward.

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• Advice for how to handle company pride

  - by user17971

  We have this "amazing" little product using the latest development methodologies, components with all the bells and whistles. I took over this product maybe 6 months ago and struggled with it from day one. Even though it is supposedly is state of the art because of all its amazing structure, using dependency injections, inversion of control from the unity framework, hibernation and is domain driven in a .net mvvm xaml application to make it streamlined and modular. I knew from the moment I saw the monolith that it was going to be an uphill struggle for me. A lot of little code-bits scattered all around in neatly organized paradigms. Debugging is difficult, tracing the code is difficult, making new code is difficult, although some modifications is surprisinly easy but it doesn't out weight the problems I have with the code by a long shot. When I took over the project I was told that the new management console was ready for delivery and all I had to do was compile it and drop it. This was the beginning of a uphill struggle, our customer didn't agree at all that this was the functionality they had asked for so I had to do modifications to the program to their specifications. Since the project pretty much has been overdue since I took over it it has always been important that we didn't add or change much to the original system. I could modify the existing bits. fast forward until today where I finally completed all their comments and issues with the program but now I think that the users has opened their eyes (even though they saw this program many times) that they will be going backwards with this new system, that it will be much worse than the tool they got today (for a long time due to the fact that I'm the only resource on the project, project manager, tester, developer, integration specialist etc) My problem is that I lost faith in this system quite early due to the nature of the program. Although I made many changes and improvements to the system I wholeheartedly sympathize with the poor users who are going to start using this system. Its not nearly doing all the things it should do. I had this conversation internally with my boss where I told him what I thought about it, that if I were the customer I wouldn't have spent money developing it. So what do I do now? The system in ready, on a staging system and nobody likes it, its too slow and boring and does maybe do 50% of what they need it to do. Despite how much energy and working around the clock I've done to this project: I won't mind scrapping the system but we've spent much money (well my salaries) developing it and my company wants us to be proud of everything we do and advocate it. How will I tackle the contractor when he asks for advice? Surely I can tell him, this is what we agreed upon based on your use case scenarios, and be done with it? How will I inform my boss about this progress? He knows what I feel about it but I always get the feeling he let my criticism pass him by as just hot air, gone tomorrow,.

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• Manic Monday - More OpenWorld Solaris Sessions: Developers, Cloud, Customer Insights, Hardware Optimization

  - by Larry Wake

  We're overflowing with Monday sessions; literally more than one person can take in. Learn more about what's new in Oracle Solaris Studio, hear about the latest x86 and SPARC hardware optimizations, get some insights on cloud deployment strategies, and find out from your peers what they're doing with Oracle Solaris. If you're an OpenWorld attendee, go to to Schedule Builder to guarantee your space in any session or lab. See yesterday's blog post and the "Focus on Oracle Solaris" guide for even more sessions. Monday, October 1st: 10:45 AM - Maximizing Your SPARC T4 Oracle Solaris Application Performance(CON6382,  Marriott Marquis - Golden Gate C3) Hear how customers and commercial software partners have reached peak performance on SPARC T4 servers and engineered systems with Oracle Solaris Studio and its latest tools for analyzing, reporting, and improving runtime performance: Autoparallelizing, high-performance compilers Performance Analyzer (used to find performance hotspots) Thread Analyzer (to expose data races and deadlocks) Code Analyzer (used to discover latent memory corruption issues) 10:45 Cloud Formation: Implementing IaaS in Practice with Oracle Solaris(CON8787, Moscone South 302) Decisions, decisions--at the same time, we've got a session that covers why Oracle Solaris is the ideal OS for public or private clouds, IaaS or PaaS, with built-in features for elastic infrastructure, unrivaled security, superfast installation and deployment, nonstop availability, and crystal-clear observability. This session will include a customer study on how Oracle Solaris is used in the cloud today to implement the Oracle stack. 12:15 PM - Customer Insight: Oracle Solaris on Oracle Exadata, Oracle Exalogic, and SPARC SuperCluster(CON8760, Moscone South 270) Hear from customers what benefits they have realized from using the Oracle stack on Oracle Exadata and Oracle’s SPARC SuperCluster and from using Oracle Solaris on those engineered systems, taking advantage of built-in lightweight OS virtualization (Zones), enterprise reliability and scale, and other key features. 1:45 PM - Case Study: Mobile Tornado Uses Oracle Technology for Better RAS and TCO?(CON4281, Moscone West 2005) Mobile Tornado develops and markets instant communication platforms, replacing traditional radio networks with cellular networks. Its critical concern is uptime. Find out how they've used Oracle Solaris, Netra SPARC T4, and Oracle Solaris Cluster, including Oracle Solaris ZFS and Zones, for their Oracle Database deployments to improve reliability and drive down cost. 3:15 PM - Technical Panel: Developing High Performance Applications on Oracle Solaris(CON7196, Marriott Marquis - Golden Gate C2) Engineers from the Oracle Solaris, Oracle Database, and Oracle Tuxedo development teams, and Oracle ISV Engineering discuss how they develop high-performance enterprise applications that take advantage of Oracle's SPARC and x86 servers, with Oracle Solaris Studio and new Oracle Solaris 11 features. Topics will include developer tools, parallel frameworks, best practices, and methodologies, as well as insights and case studies on parallelizing and optimizing application performance on Oracle Solaris. Bring your best questions! 3:15 PM -  x86 Power Management with Oracle Solaris: Current State, Opportunities, and Future(CON6271, Moscone West 2012) Another option for this time slot: learn about how Intel Xeon and Oracle Solaris work together to reduce server power consumption. This presentation addresses some of the recent power management improvements in Oracle Solaris, opportunities to further improve energy efficiency, and some future directions for Oracle Solaris power management.

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• Error while removing the new kernel 2.6.37

  - by Tarek

  Hi! I tried to install the new kernel but something went wrong and I'm trying to remove it now. The error massege is: mhd@Tarek-Laptop:~$ sudo apt-get install -f Reading package lists... Done Building dependency tree Reading state information... Done The following packages will be REMOVED: linux-image-2.6.37-020637-generic 0 upgraded, 0 newly installed, 1 to remove and 9 not upgraded. 1 not fully installed or removed. After this operation, 111MB disk space will be freed. Do you want to continue [Y/n]? y (Reading database ... 188780 files and directories currently installed.) Removing linux-image-2.6.37-020637-generic ... Examining /etc/kernel/postrm.d . run-parts: executing /etc/kernel/postrm.d/initramfs-tools 2.6.37-020637-generic /boot/vmlinuz-2.6.37-020637-generic run-parts: executing /etc/kernel/postrm.d/zz-update-grub 2.6.37-020637-generic /boot/vmlinuz-2.6.37-020637-generic /etc/default/grub: 33: Syntax error: EOF in backquote substitution run-parts: /etc/kernel/postrm.d/zz-update-grub exited with return code 2 Failed to process /etc/kernel/postrm.d at /var/lib/dpkg/info/linux-image-2.6.37-020637-generic.postrm line 328. dpkg: error processing linux-image-2.6.37-020637-generic (--remove): subprocess installed post-removal script returned error exit status 1 Errors were encountered while processing: linux-image-2.6.37-020637-generic E: Sub-process /usr/bin/dpkg returned an error code (1) The previous unsloved error is on this bug. This is my grub configuration file: # If you change this file, run 'update-grub' afterwards to update # /boot/grub/grub.cfg. GRUB_DEFAULT=0 #GRUB_HIDDEN_TIMEOUT=0 GRUB_HIDDEN_TIMEOUT_QUIET=true GRUB_TIMEOUT=10 GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian` RUB_CMDLINE_LINUX_DEFAULT="quiet splash nomodeset video=uvesafb:mode_option=1024x768-24,mtrr=3,scroll=ywrap" video=uvesafb:mode_option=>>1024x768-24<<,mtrr=3,scroll=ywrap" GRUB_CMDLINE_LINUX=" vga=792 splash" # Uncomment to enable BadRAM filtering, modify to suit your needs # This works with Linux (no patch required) and with any kernel that obtains # the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...) #GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef" # Uncomment to disable graphical terminal (grub-pc only) #GRUB_TERMINAL=console # The resolution used on graphical terminal # note that you can use only modes which your graphic card supports via VBE # you can see them in real GRUB with the command `vbeinfo' GRUB_GFXMODE=1024x768-24 # Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux #GRUB_DISABLE_LINUX_UUID=true # Uncomment to disable generation of recovery mode menu entries #GRUB_DISABLE_LINUX_RECOVERY="true" # Uncomment to get a beep at grub start #GRUB_INIT_TUNE="480 440 1" thank you for answering.

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• How can I make a universal construction more efficient?

  - by VF1

  A "universal construction" is a wrapper class for a sequential object that enables it to be linearized (a strong consistency condition for concurrent objects). For instance, here's an adapted wait-free construction, in Java, from [1], which presumes the existence of a wait-free queue that satisfies the interface WFQ (which only requires one-time consensus between threads) and assumes a Sequential interface: public interface WFQ<T> // "FIFO" iteration { int enqueue(T t); // returns the sequence number of t Iterable<T> iterateUntil(int max); // iterates until sequence max } public interface Sequential { // Apply an invocation (method + arguments) // and get a response (return value + state) Response apply(Invocation i); } public interface Factory<T> { T generate(); } // generate new default object public interface Universal extends Sequential {} public class SlowUniversal implements Universal { Factory<? extends Sequential> generator; WFQ<Invocation> wfq = new WFQ<Invocation>(); Universal(Factory<? extends Sequential> g) { generator = g; } public Response apply(Invocation i) { int max = wfq.enqueue(i); Sequential s = generator.generate(); for(Invocation invoc : wfq.iterateUntil(max)) s.apply(invoc); return s.apply(i); } } This implementation isn't very satisfying, however, since it presumes determinism of a Sequential and is really slow. I attempted to add memory recycling: public interface WFQD<T> extends WFQ<T> { T dequeue(int n); } // dequeues only when n is the tail, else assists other threads public interface CopyableSequential extends Sequential { CopyableSequential copy(); } public class RecyclingUniversal implements Universal { WFQD<CopyableSequential> wfqd = new WFQD<CopyableSequential>(); Universal(CopyableSequential init) { wfqd.enqueue(init); } public Response apply(Invocation i) { int max = wfqd.enqueue(i); CopyableSequential cs = null; int ctr = max; for(CopyableSequential csq : wfq.iterateUntil(max)) if(--max == 0) cs = csq.copy(); wfqd.dequeue(max); return cs.apply(i); } } Here are my specific questions regarding the extension: Does my implementation create a linearizable multi-threaded version of a CopyableSequential? Is it possible extend memory recycling without extending the interface (perhaps my new methods trivialize the problem)? My implementation only reduces memory when a thread returns, so can this be strengthened? [1] provided an implementation for WFQ<T>, not WFQD<T> - one does exist, though, correct? [1] Herlihy and Shavit, The Art of Multiprocessor Programming.

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• 2D Animation Smoothness - Delta time vs. Kinematics

  - by viperld002

  I'm animating a sprite in 2D with key frames of rotation and xy-positions. I've recently had a discussion with someone saying that when the device (happens to be an iPad using cocos2D) hits a performance bump due to whatever else the user may be doing, lag will arise and that the best way to fight it is to not use actual positions, but velocities, accelerations and torques with kinematics. His message is to evaluate the positions and rotations from these speeds at the current point in time. I've never experienced a situation where I've heard of using kinematics to stem lag in 2D animations and am not sure of how effective it could be. Also, it seems to be overkill. The application is not networked so it's all running on a local device. The desired effect is that the animation always plays as closely as it can to the target frame rate. Wouldn't the technique suffer the same problems as just using the time since the last frame or a fixed time step since the kinematics would also require some time value to perform the calculation? What techniques could you suggest to best achieve the desired effect? EDIT 1 Thank you for your responses, they are very illuminating. I want to clarify my question before choosing an answer however, to make sure that this post really serves it's purpose. I have a sprite of a ball, and a text file with 3 arrays worth of information (rotation,translations x, translations y) with each unit of information existing as a key frame to be stepped through (0 to 49 and back to 0 to replay it again). I have this playing by interpolating from the current key frame to the next, every n-units of time. The animation is visibly correct when compared to a video I was given of it, and it is smooth because of the interpolations between the key frames. This is the existing state of the project. There are no physics simulated, only a static animation of a ball moving in a way an artist specifically designed. Should I, instead of rotation in degrees and translations by positions in space, derive velocities, accelerations and torques to express this static animation as a function of time? As in, position now = foo(time now), where foo uses kinematics.

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• Why does my int, booleans, doubles does not work?

  - by SystemNetworks

  As you see, my code does not work. When armor1 is true, it would add my life. goldA is another class. public void goldenArmor(GameContainer gc, StateBasedGame sbg, Graphics g) { if(armor1==true) { goldA.life = life; goldA.intelligence = intelligence; goldA.power = power; goldA.lifeLeft = lifeLeft; goldA.head(); goldA.body(); goldA.legs(); } } My other class: package javagame; import org.newdawn.slick.GameContainer; import org.newdawn.slick.Graphics; import org.newdawn.slick.Image; import org.newdawn.slick.Input; import org.newdawn.slick.SlickException; /* Note: Copyright(C)2012 System Networks | Square NET | Julius Bryan Gambe. You cannot copy the style, story of the game and gameplay! To programmers: The int,doubles,strings,booleans are properly sorted out. Please don't mess it up. */ /* NOTE: We have loops but not for programming. The loop is: 1.show the world to user 2.Obtain input from the user 3.Shows the update, repeat step 1 */ import org.newdawn.slick.*; import org.newdawn.slick.state.*; import org.lwjgl.input.Mouse; //contents: // public class GoldenArmor{ //get it from play public int life; public double intelligence; public int lifeLeft; public double power; public GoldenArmor() { // TODO Auto-generated constructor stub } //start here public void head() { life += 10; intelligence +=0.5; } public void body() { lifeLeft += 100; } public void legs() { power += 100; } } /* SYSTEM NETWORKS(C) 2012 NET FRONT */ The life, intelligence, power, lifeLeft are nothing but to use it as just reference to prevent stack overflow. And at my main class, it becomes my real booleans, int, doubles. How do I fix this? It does not add it to my normal int.

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• How to handle this unfortunately non hypothetical situation with end-users?

  - by User Smith

  I work in a medium sized company but with a very small IT force. Last year (2011), I wrote an application that is very popular with a large group of end-users. We hit a deadline at the end of last year and some functionality (I will call funcA from now on) was not added into the application that was wanted at the very end. So, this application has been running in live/production since the end of 2011, I might add without issue. Yesterday, a whole group of end-users started complaining that funcA that was never in the application is no longer working. Our priority at this company is that if an application is broken it must be fixed first prior to prioritized projects. I have compared code and queries and there is no difference since 2011, which is proofA. I then was able to get one of the end-users to admit that it never worked proofB, but since then that end-user has went back and said that it was working previously......I believe the horde of end-users has assimilated her. I have also reviewed my notes for this project which has requirements and daily updates regarding the project which specifically states, "funcA not achieved due to time constraints", proofC. I have spoken with many of them and I can see where they could be confused as they are very far from a programming background, but I also know they are intelligent enough to act in a group in order to bypass project prioritization orders in order to get functionality that they want to make their job easier. The worst part is is that now group think is setting in and my boss and the head of IT is actually starting to believe them, even though there is no code or query changes. As far as reviewing the state of the logic it is very cut and dry to the point of if 1 = 1, funcA will not work. So, this is the end of the description of my scenario, but I am trying not to get severally dinged on my performance metrics due to this which would essentially have me moved to fixing a production problem that doesn't exist that will probably take over 1 month. I am looking for direct answers to this question. This question is not for rants, polling, or discussions as this is not the format for StackExchange. Please don't downvote me too terribly it is pretty common on this specific site of stack, I am looking for honest answers to this situation and I couldn't find a forum more appropriate.

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• JDK bug migration milestone: JIRA now the system of record

  - by darcy

  I'm pleased to announce the OpenJDK bug database migration project has reached a significant milestone: the JDK has switched from the legacy Sun "bugtraq" system to a new internal JIRA instance as the system of record for our bug tracking. This completes the initial phase of the previously described plan of getting OpenJDK onto an externally visible and writable bug tracker. The identities contained in the current system include recognized OpenJDK contributors. The bug migration effort to date has been sizable in multiple dimensions. There are around 140,000 distinct issues imported into the JDK project of the JIRA instance, nearly 165,000 if backport issues to track multiple-release information are included. Separately, the Code Tools OpenJDK project has its own JIRA project populated with several thousands existing bugs. Once the OpenJDK JIRA instance is externalized, approved OpenJDK projects will be able to request the creation of a JIRA project for issue tracking. There are many differences in the schema used to model bugs between the legacy bug system and the schema for the new JIRA projects. We've favored simplifications to the existing system where possible and, after much discussion, we've settled on five main states for the OpenJDK JIRA projects: New Open In progress Resolved Closed The Open and In-progress states can have a substate Understanding field set to track whether the issues has its "Cause Known" or "Fix understood". In the closed state, a Verification field can indicate whether a fix has been verified, unverified, or if the fix has failed. At the moment, there will be very little externally visible difference between JIRA for OpenJDK and the legacy system it replaces. One difference is that bug numbers for newly filed issues in the JIRA JDK project will be 8000000 and above. If you are working with JDK Hg repositories, update any local copies of jcheck to the latest version which recognizes this expanded bug range. (The bug numbers of existing issues have been preserved on the import into JIRA). Relatively soon, we plan for the pages published on bugs.sun.com to be generated from information in JIRA rather than in the legacy system. When this occurs, there will be some differences in the page display and the terminology used will be revised to reflect JIRA usage, such as referring to the "component/subcomponent" of an issue rather than its "category". The exact timing of this transition will be announced when it is known. We don't currently have a firm timeline for externalization of the JIRA system. Updates will be provided as they become available. However, that is unlikely to happen before JavaOne next week!

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• What's the best way to create a static utility class in python? Is using metaclasses code smell?

  - by rsimp

  Ok so I need to create a bunch of utility classes in python. Normally I would just use a simple module for this but I need to be able to inherit in order to share common code between them. The common code needs to reference the state of the module using it so simple imports wouldn't work well. I don't like singletons, and classes that use the classmethod decorator do not have proper support for python properties. One pattern I see used a lot is creating an internal python class prefixed with an underscore and creating a single instance which is then explicitly imported or set as the module itself. This is also used by fabric to create a common environment object (fabric.api.env). I've realized another way to accomplish this would be with metaclasses. For example: #util.py class MetaFooBase(type): @property def file_path(cls): raise NotImplementedError def inherited_method(cls): print cls.file_path #foo.py from util import * import env class MetaFoo(MetaFooBase): @property def file_path(cls): return env.base_path + "relative/path" def another_class_method(cls): pass class Foo(object): __metaclass__ = MetaFoo #client.py from foo import Foo file_path = Foo.file_path I like this approach better than the first pattern for a few reasons: First, instantiating Foo would be meaningless as it has no attributes or methods, which insures this class acts like a true single interface utility, unlike the first pattern which relies on the underscore convention to dissuade client code from creating more instances of the internal class. Second, sub-classing MetaFoo in a different module wouldn't be as awkward because I wouldn't be importing a class with an underscore which is inherently going against its private naming convention. Third, this seems to be the closest approximation to a static class that exists in python, as all the meta code applies only to the class and not to its instances. This is shown by the common convention of using cls instead of self in the class methods. As well, the base class inherits from type instead of object which would prevent users from trying to use it as a base for other non-static classes. It's implementation as a static class is also apparent when using it by the naming convention Foo, as opposed to foo, which denotes a static class method is being used. As much as I think this is a good fit, I feel that others might feel its not pythonic because its not a sanctioned use for metaclasses which should be avoided 99% of the time. I also find most python devs tend to shy away from metaclasses which might affect code reuse/maintainability. Is this code considered code smell in the python community? I ask because I'm creating a pypi package, and would like to do everything I can to increase adoption.

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• Why does switching users completely hang my system every time?

  - by Stéphane

  I have a fresh install of 11.04 64bit, with 2 administrator accounts and 4 normal accounts. The 4 normal accounts (the kids' accounts) don't have passwords, they can login simply by clicking on their names. When any of the users -- either admin or normal -- tries to switch to another account by clicking in the top-right corner of the screen and selecting another user, the screen goes black and the entire system locks up. Even CTRL+ALT+F1 through F7 does nothing. This is reproducible 100% of the time on this system. I can ssh into the box when the console locks up, and by running top, I see that Xorg is consuming about 100% of the CPU. Looking at the output of "ps axfu" in bash while the system is in this "locked up" state, here is the lightdm and X process tree: USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 1153 0.0 0.1 183508 4292 ? Ssl Dec26 0:00 lightdm root 2187 0.4 4.6 265976 164168 tty7 Ss+ 00:43 0:21 \_ /usr/bin/X :0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch stephane 2612 0.0 0.3 266400 10736 ? Ssl 01:52 0:00 \_ /usr/bin/gnome-session --session=ubuntu stephane 2650 0.0 0.0 12264 276 ? Ss 01:52 0:00 | \_ /usr/bin/ssh-agent /usr/bin/dbus-launch --exit-with-session /usr/bin/gnome-session --session=ubuntu stephane 2703 0.8 3.0 562068 106548 ? Sl 01:52 0:08 | \_ compiz stephane 2801 0.0 0.0 4264 584 ? Ss 01:52 0:00 | | \_ /bin/sh -c /usr/bin/compiz-decorator stephane 2802 0.0 0.3 265744 13772 ? Sl 01:52 0:00 | | \_ /usr/bin/unity-window-decorator ...cut... root 3024 80.6 0.3 107928 13088 tty8 Rs+ 01:53 12:34 \_ /usr/bin/X :1 -auth /var/run/lightdm/root/:1 -nolisten tcp vt8 -novtswitch That last process, pid #3024 in this case, is what has the CPU pegged. In case it matters (I suspect it might) here is what I think may be the relevant information for my video card, taken from /var/log/Xorg.0.log: [ 3392.653] (II) Loading /usr/lib/x86_64-linux-gnu/xorg/extra-modules/extra-modules.dpkg-tmp/modules/extensions/libglx.so [ 3392.653] (II) Module glx: vendor="FireGL - AMD Technologies Inc." [ 3392.653] compiled for 6.9.0, module version = 1.0.0 ... [ 3392.655] (II) LoadModule: "fglrx" [ 3392.655] (II) Loading /usr/lib/x86_64-linux-gnu/xorg/extra-modules/extra-modules.dpkg-tmp/modules/drivers/fglrx_drv.so [ 3392.672] (II) Module fglrx: vendor="FireGL - ATI Technologies Inc." [ 3392.672] compiled for 1.4.99.906, module version = 8.88.7 [ 3392.672] Module class: X.Org Video Driver ... [ 3392.759] (==) fglrx(0): ATI 2D Acceleration Architecture enabled [ 3392.759] (--) fglrx(0): Chipset: "AMD Radeon HD 6410D" (Chipset = 0x9644) Lastly: I did see this posting: Change user on 11.10 hangs system ...but I checked, and the libpam-smbpass package isn't installed on this system.

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• Real-Time Multi-User Gaming Platform

  - by Victor Engel

  I asked this question at Stack Overflow but was told it's more appropriate here, so I'm posting it again here. I'm considering developing a real-time multi-user game, and I want to gather some information about possibilities before I do some real development. I've thought about how best to ask the question, and for simplicity, the best way that occurred to me was to make an analogy to the field (or playground) game darebase. In the field game of darebase, there are two or more bases. To start, there is one team on each base. The game is a fancy game of tag. When two people meet out in the field, the person who left his base most recently timewise captures the other person. They then return to that person's base. Play continues until everyone is part of the same team. So, analogizing this to an online computer game, let's suppose there are an indefinite number of bases. When a person starts up the game, he has a team that is located at, for example, his current GPS coordinates. It could be a virtual world, but for sake of argument, let's suppose the virtual world corresponds to the player's actual GPS coordinates. The game software then consults the database to see where the closest other base is that is online, and the two teams play their game of virtual tag. Note that the user of the other base could have a different base than the one run by the current user as the closest base to him, in which case, he would be in two simultaneous battles, one with each base. When they go offline, the state of their players is saved on a server somewhere. Game logic calls for the players to have some automaton-logic of some sort, so they can fend for themselves in a limited way using basic rules, until their user goes online again. The user doesn't control the players' movements directly, but issues general directives that influence the players' movement logic. I think this analogy is good enough to frame my question. What sort of platforms are available to develop this sort of game? I've been looking at smartfoxserver, but I'm not convinced yet that it is the best option or even that it will work at all. One possibility, of course, would be to roll out my own web server, but I'd rather not do that if there is an existing service out there already that I could tap into. I will be developing for iOS devices at first. So any suggestions would be greatly appreciated. I think I need to establish the architecture first before proceeding with this project. Note that darbase is not the game I intend to implement, but, upon reflection, that might not be a bad idea either.

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• Is there an API for determining congressional districts?

  - by ardavis

  I'm looking to determine the congressional district based on an address my user is providing. This will avoid having the user to look it up themselves. Does an API of this sort exist? Note Through my attempts to find one, I've only come across these: http://www.govtrack.us/developers/api (not sure how to submit an an address or zip code however) The following resources are available in the API ...Bills and resolutions in the U.S. Congress since 1973 (the 93rd Congress). ...A (bill, person) pair indicating cosponsorship, with join and withdrawn dates. ...Members of Congress and U.S. Presidents since the founding of the nation. ...Terms held in office by Members of Congress and U.S. Presidents. Each term corresponds with an election, meaning each term in the House covers two years (one 'Congress'), as President four years, and in the Senate six years (three 'Congresses'). ...Roll call votes in the U.S. Congress since 1789. How people voted is accessed through the Vote_voter API. ...How people voted on roll call votes in the U.S. Congress since 1789. See the Vote API. Filter on the vote field to get the results of a particular vote... http://www.opencongress.org/api (seems to be a way to find congress information, but not districts) This API provides programmers with structured access to all the data on OpenCongress, everything from official bill info to news and blog coverage to user-generated votes on bills and much more... This API defaults to returning XML. All queries can also return JSON... https://groups.google.com/forum/?fromgroups=#!topic/opendems-discuss/CeKyi_aANaE (similar question, no resolution) I've been looking over Open Dems, and seeing what's exposed at this point and what isn't. I work with Democrats Abroad, and am interested in using stuff from the lab for their sites. I quickly looked over the Precinct API, which does both more and less than what I'd need. An ideal resource would be any way of translating addresses into CD at the very least (getting state district data would be good as well), since that would make it easier for DA's membership to make a difference in races like last month's NY26 race... Update I'm looking at the source for the govtrack.us website and the 'doGeoCode' function may be useful. view-source:http://www.govtrack.us/congress/members If no one has any suggestions, I will try to go off of what they are doing.

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• 5 ways to stop code thrashing&hellip;

  - by MarkPearl

  A few days ago I was programming on a personal project and hit a roadblock. I was applying the MVVM pattern and for some reason my view model was not updating the view when the state changed??? I had applied this pattern many times before and had never had this problem. It just didn’t make sense. So what did I do… I did what anyone would have done in my situation and looked to pass the blame to someone or something else. I tried to blame one of the inherited base classes, but it looked fine, then to Visual Studio, but it seemed to be fine and eventually to any random segment of code I came across. My elementary problem had now mushroomed into one that had lost any logical basis and I was in thrashing mode! So what to do when you begin to thrash? 1) Do a general code cleanup – Now there is a difference between cleaning code and changing code . When you thrash you change code and you want to avoid this. What you really want to do is things like rename variables to have better meaning and go over your comments. 2) Do a proof of concept – if cleaning code doesn’t help. The  you want to isolate the problem and identify the key concepts. When you isolate code you ideally want it to be in a totally separate project with as little complexity as possible. Make the building blocks and try and replicate the functionality that you are getting in your current application. 3) Phone a friend – I have found speaking to someone else about the problem generally helps me solve any thrashing issues I am having. Usually they don’t even have to say anything to solve the problem, just you talking them through the problem helps you get clarity of mind. 4) Let the dust settle – Sometimes time is the best solution. I have had a few problems that no matter who I discussed them with and no matter how much code cleaning I had done I just couldn’t seem to fix it. My brain just seemed to be going in circles. A good nights rest has always helped and often just the break away from the problem has helped me find a solution. 5) Stack overflow it – So similar to phone a friend. I am really surprised to see what a melting pot stack overflow has been and what a help it has been in solving technology specific problems. Just be considerate to those using the site and explain clearly exactly what problem you are having and the technologies you are using or else you will probably not get any useful help…

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• 2D game - Missile shooting problem on Android

  - by Niksa

  Hello, I have to make a tank that sits still but moves his turret and shoots missiles. As this is my first Android application ever and I haven't done any game development either, I've come across a few problems... Now, I did the tank and the moving turret once I read the Android tutorial for the LunarLander sample code. So this code is based on the LunarLander code. But I'm having trouble doing the missile firing then SPACE button is being pressed. private void doDraw(Canvas canvas) { canvas.drawBitmap(backgroundImage, 0, 0, null); // draws the tank canvas.drawBitmap(tank, x_tank, y_tank, new Paint()); // draws and rotates the tank turret canvas.rotate((float) mHeading, (float) x_turret + mTurretWidth, y_turret); canvas.drawBitmap(turret, x_turret, y_turret, new Paint()); // draws the grenade that is a regular circle from ShapeDrawable class bullet.setBounds(x_bullet, y_bullet, x_bullet + width, y_bullet + height); bullet.draw(canvas); } UPDATE GAME method private void updateGame() throws InterruptedException { long now = System.currentTimeMillis(); if (mLastTime > now) return; double elapsed = (now - mLastTime) / 1000.0; mLastTime = now; // dUP and dDown, rotates the turret from 0 to 75 degrees. if (dUp) mHeading += 1 * (PHYS_SLEW_SEC * elapsed); if (mHeading >= 75) mHeading = 75; if (dDown) mHeading += (-1) * (PHYS_SLEW_SEC * elapsed); if (mHeading < 0) mHeading = 0; if (dSpace){ // missile Logic, a straight trajectorie for now x_bullet -= 1; y_bullet -= 1; //doesn't work, has to be updated every pixel or what? } boolean doKeyDown(int keyCode, KeyEvent msg) { boolean handled = false; synchronized (mSurfaceHolder) { if (keyCode == KeyEvent.KEYCODE_SPACE){ dSpace = true; handled = true; } if (keyCode == KeyEvent.KEYCODE_DPAD_UP){ dUp = true; handled = true; } if (keyCode == KeyEvent.KEYCODE_DPAD_DOWN){ dDown = true; handled = true; } return handled; } } } a method run that runs the game... public void run() { while (mRun) { Canvas c = null; try { c = mSurfaceHolder.lockCanvas(null); synchronized (mSurfaceHolder) { if (mMode == STATE_RUNNING) updateGame(); doDraw(c); } } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } finally { // do this in a finally so that if an exception is thrown // during the above, we don't leave the Surface in an // inconsistent state if (c != null) { mSurfaceHolder.unlockCanvasAndPost(c); } } } } So the question would be, how do I make that the bullet is fired on a single SPACE key press from the turret to the end of the screen? Could you help me out here, I seem to be in the dark here... Thanks, Niksa

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• ZFS for Database Log Files

  - by user12620111

  I've been troubled by drop outs in CPU usage in my application server, characterized by the CPUs suddenly going from close to 90% CPU busy to almost completely CPU idle for a few seconds. Here is an example of a drop out as shown by a snippet of vmstat data taken while the application server is under a heavy workload. # vmstat 1  kthr      memory            page            disk          faults      cpu  r b w   swap  free  re  mf pi po fr de sr s3 s4 s5 s6   in   sy   cs us sy id  1 0 0 130160176 116381952 0 16 0 0 0 0  0  0  0  0  0 207377 117715 203884 70 21 9  12 0 0 130160160 116381936 0 25 0 0 0 0 0  0  0  0  0 200413 117162 197250 70 20 9  11 0 0 130160176 116381920 0 16 0 0 0 0 0  0  1  0  0 203150 119365 200249 72 21 7  8 0 0 130160176 116377808 0 19 0 0 0 0  0  0  0  0  0 169826 96144 165194 56 17 27  0 0 0 130160176 116377800 0 16 0 0 0 0  0  0  0  0  1 10245 9376 9164 2  1 97  0 0 0 130160176 116377792 0 16 0 0 0 0  0  0  0  0  2 15742 12401 14784 4 1 95  0 0 0 130160176 116377776 2 16 0 0 0 0  0  0  1  0  0 19972 17703 19612 6 2 92  14 0 0 130160176 116377696 0 16 0 0 0 0 0  0  0  0  0 202794 116793 199807 71 21 8  9 0 0 130160160 116373584 0 30 0 0 0 0  0  0 18  0  0 203123 117857 198825 69 20 11 This behavior occurred consistently while the application server was processing synthetic transactions: HTTP requests from JMeter running on an external machine. I explored many theories trying to explain the drop outs, including: Unexpected JMeter behavior Network contention Java Garbage Collection Application Server thread pool problems Connection pool problems Database transaction processing Database I/O contention Graphing the CPU %idle led to a breakthrough: Several of the drop outs were 30 seconds apart. With that insight, I went digging through the data again and looking for other outliers that were 30 seconds apart. In the database server statistics, I found spikes in the iostat "asvc_t" (average response time of disk transactions, in milliseconds) for the disk drive that was being used for the database log files. Here is an example:                     extended device statistics     r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device     0.0 2053.6    0.0 8234.3  0.0  0.2    0.0    0.1   0  24 c3t60080E5...F4F6d0s0     0.0 2162.2    0.0 8652.8  0.0  0.3    0.0    0.1   0  28 c3t60080E5...F4F6d0s0     0.0 1102.5    0.0 10012.8  0.0  4.5    0.0    4.1   0  69 c3t60080E5...F4F6d0s0     0.0   74.0    0.0 7920.6  0.0 10.0    0.0  135.1   0 100 c3t60080E5...F4F6d0s0     0.0  568.7    0.0 6674.0  0.0  6.4    0.0   11.2   0  90 c3t60080E5...F4F6d0s0     0.0 1358.0    0.0 5456.0  0.0  0.6    0.0    0.4   0  55 c3t60080E5...F4F6d0s0     0.0 1314.3    0.0 5285.2  0.0  0.7    0.0    0.5   0  70 c3t60080E5...F4F6d0s0 Here is a little more information about my database configuration: The database and application server were running on two different SPARC servers. Storage for the database was on a storage array connected via 8 gigabit Fibre Channel Data storage and log file were on different physical disk drives Reliable low latency I/O is provided by battery backed NVRAM Highly available: Two Fibre Channel links accessed via MPxIO Two Mirrored cache controllers The log file physical disks were mirrored in the storage device Database log files on a ZFS Filesystem with cutting-edge technologies, such as copy-on-write and end-to-end checksumming Why would I be getting service time spikes in my high-end storage? First, I wanted to verify that the database log disk service time spikes aligned with the application server CPU drop outs, and they did: At first, I guessed that the disk service time spikes might be related to flushing the write through cache on the storage device, but I was unable to validate that theory. After searching the WWW for a while, I decided to try using a separate log device: # zpool add ZFS-db-41 log c3t60080E500017D55C000015C150A9F8A7d0 The ZFS log device is configured in a similar manner as described above: two physical disks mirrored in the storage array. This change to the database storage configuration eliminated the application server CPU drop outs: Here is the zpool configuration: # zpool status ZFS-db-41   pool: ZFS-db-41  state: ONLINE  scan: none requested config:         NAME                                     STATE         ZFS-db-41                                ONLINE           c3t60080E5...F4F6d0  ONLINE         logs           c3t60080E5...F8A7d0  ONLINE Now, the I/O spikes look like this:                     extended device statistics                  r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device     0.0 1053.5    0.0 4234.1  0.0  0.8    0.0    0.7   0  75 c3t60080E5...F8A7d0s0                     extended device statistics                  r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device     0.0 1131.8    0.0 4555.3  0.0  0.8    0.0    0.7   0  76 c3t60080E5...F8A7d0s0                     extended device statistics                  r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device     0.0 1167.6    0.0 4682.2  0.0  0.7    0.0    0.6   0  74 c3t60080E5...F8A7d0s0     0.0  162.2    0.0 19153.9  0.0  0.7    0.0    4.2   0  12 c3t60080E5...F4F6d0s0                     extended device statistics                  r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device     0.0 1247.2    0.0 4992.6  0.0  0.7    0.0    0.6   0  71 c3t60080E5...F8A7d0s0     0.0   41.0    0.0   70.0  0.0  0.1    0.0    1.6   0   2 c3t60080E5...F4F6d0s0                     extended device statistics                  r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device     0.0 1241.3    0.0 4989.3  0.0  0.8    0.0    0.6   0  75 c3t60080E5...F8A7d0s0                     extended device statistics                  r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device     0.0 1193.2    0.0 4772.9  0.0  0.7    0.0    0.6   0  71 c3t60080E5...F8A7d0s0 We can see the steady flow of 4k writes to the ZIL device from O_SYNC database log file writes. The spikes are from flushing the transaction group. Like almost all problems that I run into, once I thoroughly understand the problem, I find that other people have documented similar experiences. Thanks to all of you who have documented alternative approaches. Saved for another day: now that the problem is obvious, I should try "zfs:zfs_immediate_write_sz" as recommended in the ZFS Evil Tuning Guide. References: The ZFS Intent Log Solaris ZFS, Synchronous Writes and the ZIL Explained ZFS Evil Tuning Guide: Cache Flushes ZFS Evil Tuning Guide: Tuning ZFS for Database Performance

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• Big-name School for Undergrad Students

  - by itaiferber

  As a soon-to-be graduating high school senior in the U.S., I'm going to be facing a tough decision in a few months: which college should I go to? Will it be worth it to go to Cornell or Stanford or Carnegie Mellon (assuming I get in, of course) to get a big-name computer science degree, internships, and connections with professors, while taking on massive debt; or am I better off going to SUNY Binghamton (probably the best state school in New York) and still get a pretty decent education while saving myself from over a hundred-thousand dollars worth of debt? Yes, I know questions like this has been asked before (namely here and here), but please bear with me because I haven't found an answer that fits my particular situation. I've read the two linked questions above in depth, but they haven't answered what I want to know: Yes, I understand that going to a big-name college can potentially get me connected with some wonderful professors and leaders in the field, but on average, how does that translate financially? I mean, will good connections pay off so well that I'd be easily getting rid of over a hundred-thousand dollars of debt? And how does the fact that I can get a fifth-years master's degree at Carnegie Mellon play into the equation? Will the higher degree right off the bat help me get a better-paying job just out of college, or will the extra year only put me further into debt? Not having to go to graduate school to get a comparable degree will, of course, be a great financial relief, but will getting it so early give it any greater worth? And if I go to SUNY Binghamton, which is far lesser-known than what I've considered (although if there are any alumni out there who want to share their experience, I would greatly appreciate it), would I be closing off doors that would potentially offset my short-term economic gain with long-term benefits? Essentially, is the short-term benefit overweighed by a potential long-term loss? The answers to these questions all tie in to my final college decision (again, permitting I make it to these schools), so I hope that asking the skilled and knowledgeable people of the field will help me make the right choice (if there is such a thing). Also, please note: I'm in a rather peculiar situation where I can't pay for college without taking out a bunch of loans, but will be getting little to no financial aid (likely federal or otherwise). I don't want to elaborate on this too much (so take it at face value), but this is mainly the reason I'm asking the question. Thanks a lot! It means a lot to me.

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• No wireless connection using a conceptronic c54i (RT2561/RT61 rev B)

  - by jrosell

  Detected but not working. New install on ubuntu 11.10 using coneptronic C54Ri. As documentation says it uses Ralink drivers.... Any ideas why my wireless does not work? $ lspci -nn | grep -i 'ralink' 01:05.0 Network controller: Ralink corp. RT2561/RT61 rev B 802.11g ifconfig eth0 Link encap:Ethernet HWaddr 00:1e:90:e5:af:13 inet addr:192.168.0.197 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::21e:90ff:fee5:af13/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:28361 errors:0 dropped:0 overruns:0 frame:0 TX packets:16858 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:39812172 (39.8 MB) TX bytes:1633405 (1.6 MB) Interrupt:43 Base address:0xc000 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:80 errors:0 dropped:0 overruns:0 frame:0 TX packets:80 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:6608 (6.6 KB) TX bytes:6608 (6.6 KB) iwconfig wlan0 wlan0 IEEE 802.11abg ESSIDff/any Mode:Managed Access Point: Not-Associated Tx-Power=0 dBm Retry long limit:7 RTS thrff Fragment thrff Power Managementff lsmod | grep rt rt61pci 27493 0 crc_itu_t 12627 1 rt61pci rt2x00pci 14202 1 rt61pci rt2x00lib 48114 2 rt61pci,rt2x00pci mac80211 272785 2 rt2x00pci,rt2x00lib cfg80211 172392 2 rt2x00lib,mac80211 eeprom_93cx6 12653 1 rt61pci parport_pc 32114 1 parport 40930 3 ppdev,parport_pc,lp lsmod | grep rt [ 2497.816989] phy0 -> rt2x00pci_regbusy_read: Error - Indirect register access failed: offset=0x0000308c, value=0xffffffff [ 2497.827112] phy0 -> rt2x00pci_regbusy_read: Error - Indirect register access failed: offset=0x0000308c, value=0xffffffff [ 2497.837430] phy0 -> rt2x00pci_regbusy_read: Error - Indirect register access failed: offset=0x0000308c, value=0xffffffff [ 2497.847528] phy0 -> rt2x00pci_regbusy_read: Error - Indirect register access failed: offset=0x0000308c, value=0xffffffff [ 2497.847632] phy0 -> rt61pci_wait_bbp_ready: Error - BBP register access faile d, aborting. [ 2497.847637] phy0 -> rt61pci_set_device_state: Error - Device failed to enter state 4 (-5). sudo lshw -C network *-network DISABLED description: Wireless interface product: RT2561/RT61 rev B 802.11g vendor: Ralink corp. physical id: 5 bus info: pci@0000:01:05.0 logical name: wlan0 version: 00 serial: fa:b8:14:58:62:35 width: 32 bits clock: 33MHz capabilities: pm cap_list ethernet physical wireless configuration: broadcast=yes driver=rt61pci driverversion=3.0.0-12-generic firmware=0.8 latency=0 link=no multicast=yes wireless=IEEE 802.11abg resources: irq:16 memory:fdef8000-fdefffff iwlist scan lo Interface doesn't support scanning. eth0 Interface doesn't support scanning. wlan0 Failed to read scan data : Network is down uname -mr 3.0.0-12-generic i686 Edit 1 $ rfkill list all 0: phy0: Wireless LAN Soft blocked: no Hard blocked: no On reboot, sudo lshw -C network returns network is ok. Hovever, WPA keeps on asking the wireless key

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• Suggestions for Summer Intern Application Assignments

  - by orangepips

  As part of our application process we want prospective college interns to complete an assignment on their own - either programming or analytical - to give us something tangible to evaluate such as code or a flowchart. I have two ideas for these assignments, one programming and one analytical, I am interested in gathering feedback about these. Programming Assignment Generate an a month's calendar for a given date. The first row should indicate the days of the week (e.g. Sunday - Saturday). Each subsequent row should contain a week's days. The date supplied should be highlighted (e.g. bolded). I am thinking we'll probably proscribe the output format even more strictly - probably down to what the HTML source should look like including CSS classes. Thinking is this forces answerers to actually do some work if they merely copy a solution from the internet. Analytical Assignment Diagram or describe in prose a system for managing a set of traffic lights for traffic at a four way intersection. Each direction (i.e. North, South, East and West) has two lanes (i.e. right and left). The left lane is turn only and has green arrow light to indicate right of way. The system is able to detect if lanes have cars in them and change the lights accordingly. I would expect a flow chart or some prose describing a finite state machine that deals with each contingency. This would hopefully provide some indication of the applicant's ability to reason through a logic problem of sorts and articulate an approach for solving. Areas Seeking Feedback Is it unreasonable to ask this of applicants? If not, is it better to request before or after a phone screen? Are these questions too hard or easy for a collegiate audience? Any suggestions for alternate questions? Do these seem like good tools for analyzing people who would part of a software development life cycle? Programming language suggestions - I'm thinking Java, Python and/or C# (we're actually a ColdFusion shop).

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• Using elapsed time for SlowMo in XNA

  - by Dave Voyles

  I'm trying to create a slow-mo effect in my pong game so that when a player is a button the paddles and ball will suddenly move at a far slower speed. I believe my understanding of the concepts of adjusting the timing in XNA are done, but I'm not sure of how to incorporate it into my design exactly. The updates for my bats (paddles) are done in my Bat.cs class: /// Controls the bat moving up the screen /// </summary> public void MoveUp() { SetPosition(Position + new Vector2(0, -moveSpeed)); } /// <summary> /// Controls the bat moving down the screen /// </summary> public void MoveDown() { SetPosition(Position + new Vector2(0, moveSpeed)); } /// <summary> /// Updates the position of the AI bat, in order to track the ball /// </summary> /// <param name="ball"></param> public virtual void UpdatePosition(Ball ball) { size.X = (int)Position.X; size.Y = (int)Position.Y; } While the rest of my game updates are done in my GameplayScreen.cs class (I'm using the XNA game state management sample) Class GameplayScreen { ........... bool slow; .......... public override void Update(GameTime gameTime, bool otherScreenHasFocus, bool coveredByOtherScreen) base.Update(gameTime, otherScreenHasFocus, false); if (IsActive) { // SlowMo Stuff Elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds; if (Slowmo) Elapsed *= .8f; MoveTimer += Elapsed; double elapsedTime = gameTime.ElapsedGameTime.TotalMilliseconds; if (Keyboard.GetState().IsKeyDown(Keys.Up)) slow = true; else if (Keyboard.GetState().IsKeyDown(Keys.Down)) slow = false; if (slow == true) elapsedTime *= .1f; // Updating bat position leftBat.UpdatePosition(ball); rightBat.UpdatePosition(ball); // Updating the ball position ball.UpdatePosition(); and finally my fixed time step is declared in the constructor of my Game1.cs Class: /// <summary> /// The main game constructor. /// </summary> public Game1() { IsFixedTimeStep = slow = false; } So my question is: Where do I place the MoveTimer or elapsedTime, so that my bat will slow down accordingly?

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• How do I maintain a really poorly written code base?

  - by onlineapplab.com

  Recently I got hired to work on existing web application because of NDA I'm not at liberty to disclose any details but this application is working online in sort of a beta testing stage before official launch. We have a few hundred users right now but this number is supposed to significantly increase after official launch. The application is written in PHP (but it is irrelevant to my question) and is running on a dual xeon processor standalone server with severe performance problems. I have seen a lot of bad PHP code but this really sets new standards, especially knowing how much time and money was invested in developing it. it is as badly coded as possible there is PHP, HTML, SQL mixed together and code is repeated whenever it is necessary (especially SQL queries). there are not any functions used, not mentioning any OOP there are four versions of the app (desktop, iPhone, Android + other mobile) each version has pretty much the same functionality but was created by copying the whole code base, so now there are some differences between each version and it is really hard to maintain the database is really badly designed, which is causing severe performance problems also for fixing some errors in PHP code there is a lot of database triggers used which are updating data on SELECT and on INSERT so any testing is a nightmare Basically, any sin of a bad programming you can imagine is there for example it is not only possible to use SQL injections in literally every place but you can log into app if you use a login which doesn't exist and an empty password. The team which created this app is not working on it any more and there is an outsourced team which suggested that there are some problems but was never willing to deal with the elephant in the room partially because they've got a very comfortable contract and partially due to lack of skills (just my opinion). My job was supposed to be fixing some performance problems and extending existing functionality but first thing I was asked to do was a review of the existing code base. I've made my review and it was quite a shock for the management but my conclusions were after some time finally confirmed by other programmers. Management made it clear that it is not possible to start rewriting this app from scratch (which in my opinion should be done). We have to maintain its operable state and at the same time fix performance errors and extend the functionality. My question is, as I don't want just to patch the existing code, how to transform this into properly written app while keeping the existing code working at the same time? My plan is: Unify four existing versions into common code base (fixing only most obvious errors). Redesign db and use triggers to populate it with data (so data will be maintained in two formats at the same time) All new functionality will be written as separate project. Step by step transfer existing functionality into the new project After some time everything will be in the new project Some explanation about #2, right now it is practically impossible to make any updates in existing db any change requires reviewing whole code and making changes in many places. Is such plan feasible at all? Another solution is to walk away and leave the headache to someone else.

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