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• Pretty URL in ADF Faces of JDeveloper 11.1.2.2

  - by Frank Nimphius

  Many features planned for Oracle JDeveloper 12c find their way into current releases of Oracle JDeveloper 11g R1 and JDeveloper 11g R2. One example of such a feature is "pretty URL" - or "clean URL" as the Oracle JDeveloper 11g R2 (11.1.2.2) documentation puts it. "A.2.3.24 Clean URLs Historically, ADF Faces has used URL parameters to hold information, such as window IDs and state. However, URL parameters can prevent search engines from recognizing when URLs are actually the same, and therefore interfere with analytics. URL parameters can also interfere with bookmarking. By default, ADF Faces removes URL parameters using the HTML5 History Management API. If that API is unavailable, then session cookies are used.You can also manually configure how URL parameters are removed using the context parameter oracle.adf.view.rich.prettyURL.OPTIONS. Set the parameter to off so that no parameters are removed. Set the parameter to useHistoryApi to only use the HTML5 History Management API. If a browser does not support this API, then no parameters will be removed. Set the parameter to useCookies to use session cookies to remove parameters. If the browser does not support cookies, then no parameters will be removed." See: http://docs.oracle.com/cd/E26098_01/web.1112/e16181/ap_config.htm#ADFUI12856 So basically, what this part in the documentation says is: In JDeveloper 11g R2 (11.1.2.2), Oracle ADF Faces automatically removes its internally used dynamic parameters from the URL You can influence the setting with the prettyURL.OPTIONS context option, which however is not recommended you to do because the default behavior is able to detect if the browser client supports HTML 5 History management or not. In the latter case it the uses a session cookie and if this doesn't work, falls back to the "old" URL parameter adding. The information that is not so explicit and clearly mentioned in the documentation is that this is only for ADF Faces parameters (such as _afrLoop, Adf-Window-Id, etc.), but not the ADF controller token (_adf.ctrl-state)! Removing the ADF controller token is an enhancement request that will be implemented in Oracle JDeveloper 12c

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• Improving the performance of JDeveloper11g (part 2) and JVMs in general

  - by asantaga

  Just received an email from one of our JVM developers who read my blog entry on Performance tuning JDeveloper11g and he's confirmed that all of the above parameters are totally supported :-) He's also provided a description of the parameters so we can learn what magic is actually being applied. - -XX:+AggressiveOpts -- this enables the latest and greatest JVM optimizations. It will likely help most Java applications. It's fully supported. The downside of it is that because it has the latest and greatest optimizations, there is some small probability that it may not offer as good of an experience. As those features enabled with this command line option have "matured", they are made the default in a future JDK release. So, you can think of this command line option as the place where the newest optimizations get introduced. Some time later they are moved out from under AggressiveOpts to become default behavior. -XX:+OptimizeStringConcat -- only works with the -server JVM. It may be enabled by the default in a future JDK 7 update release. This option delays the construction of a StringBuilder/StringBuffer and attempts to avoid re-sizing the underlying char[] by attempting to detect the size of the char[] to allocate based on what's being appended to the StringBuilder/StringBuffer. -XX:+UseStringCache -- I would not suggest using this unless you knew that JDeveloper allocated the same string over and over again. And, the string that's allocated over and over again is one of the first 100,000 allocated strings. In short, I'd recommend against using it. And, in fact, in Java 7 (currently) does not include this feature. -XX:+UseCompressedOops -- applicable to 64-bit JVMs. And, if you're using a 64-bit JVM, I'd suggest you use it. It's auto enabled in JDK 7 64-bit JVMs and later JDK 6 64-bit JVMs enable it by default too. -XX:+UseGCOverheadLimit -- by default this option is already enabled. One other command line option to consider is -XX:+TieredCompilation for a JDK 6 Update 25 or later, or JDK 7. This gives you the startup of a -client JVM and the peak performance of a -server JVM. Awesome-ness!  Finally, Charlies also pointed out to me a "new" book he's just published where he goes into the details of JVM tuning, a must for all Fusion Middleware tuning exercises..  (click the book)  Thanks Charlie!

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• Cursor running wild, then crashes on an Asus G73sw

  - by Yarchmon

  The cursor sometimes goes wild, I get random clicks, the windows are resizing, the cursor disappears. In the worst case, clicks and keyboards are disabled. I've tried the solution given on doc.ubuntu-fr.org and add tu grub : i8042.nomux=1 i8042.reset=1 in GRUB_CMDLINE_LINUX_DEFAULT But it didn't work What can I do ? Graphic card : Geforce GTX460M. Ubuntu : 11.10 (64 bits). Laptop Asus G73sw Interface : Unity (since 11.10) - didn't get this problem with Gnome before. Complement: when a window is resizing, it gets drag-boxes at every corner, center of sides and center of the window. It looks like my touchpad sends random info, or like a "ghost" touchscreen. lspci result : 00:00.0 Host bridge: Intel Corporation 2nd Generation Core Processor Family DRAM Controller (rev 09) 00:01.0 PCI bridge: Intel Corporation Xeon E3-1200/2nd Generation Core Processor Family PCI Express Root Port (rev 09) 00:16.0 Communication controller: Intel Corporation 6 Series/C200 Series Chipset Family MEI Controller #1 (rev 04) 00:1a.0 USB Controller: Intel Corporation 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #2 (rev 05) 00:1b.0 Audio device: Intel Corporation 6 Series/C200 Series Chipset Family High Definition Audio Controller (rev 05) 00:1c.0 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 1 (rev b5) 00:1c.1 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 2 (rev b5) 00:1c.3 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 4 (rev b5) 00:1c.5 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 6 (rev b5) 00:1d.0 USB Controller: Intel Corporation 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #1 (rev 05) 00:1f.0 ISA bridge: Intel Corporation HM65 Express Chipset Family LPC Controller (rev 05) 00:1f.2 SATA controller: Intel Corporation 6 Series/C200 Series Chipset Family 6 port SATA AHCI Controller (rev 05) 00:1f.3 SMBus: Intel Corporation 6 Series/C200 Series Chipset Family SMBus Controller (rev 05) 01:00.0 VGA compatible controller: nVidia Corporation GF106 [GeForce GTX 460M] (rev a1) 01:00.1 Audio device: nVidia Corporation GF106 High Definition Audio Controller (rev a1) 03:00.0 Network controller: Atheros Communications Inc. AR9285 Wireless Network Adapter (PCI-Express) (rev 01) 04:00.0 USB Controller: Fresco Logic FL1000G USB 3.0 Host Controller (rev 04) 05:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 06) Edit 01-09-12: Tried on Ubuntu 2D: the behavior is different: it's like i'm randomly clicking on the workspace switcher icon. In the worst case, it can happen several times in a minute.

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• How exactly is Google Webmaster Tools measuring "Site Performance"?

  - by Rémi

  I've been working for two months now on improving our response time (mainly server side) on a new forum (a brand new product on a technical point of view) we've launched in Germany a few month ago and I'm a lot surprised by the results I get. I monitor our response time using Apache logs and our own implementation of Boomerang beacon. Using my stats, I can see that our new product responds in about 680 ms where our old product was responding in about 1050 ms. On the other side, Google Webmaster Tool tells us that our pages have an average reponse time of about 1500 ms today where it was 700 three months ago with our old product. I've figured that GWT was taking client side metrics into account so I've added some measures on our Boomerang beacon and everything looks just fine. I've also ran some random pages on ySlow and Google's Page Speed and everything looks better than it was before. We event have a 82% on Google's Page Speed tool which is quite cool for a site with some ads in it :) Lately, we have signed a deal with Akamai to use two of their products : CDN for our static files (we were using another CDN before but it wasn't very effective) and RMA to improve Networks routes. We have also introduced a new agressive cache mecanism to ensure that most of the pages served to crawlers are cached by our memcache grid. After checking my metrics, it seems that this changes have improved from 650ms to about 500ms, which is good (still not great but it is definitly an improvement). But webmaster tools continues to report an increasing average response time where we see it decreasing in the same time. Have you ever had the same kind of wierd behavior on your sites while doing performance improvements ? Do you have any idea how to monitor the same thing Google does with Site Performance in Google Webmaster Tools so that we could improve our site and constantly check if it is what Google wants ? Edit 2011/07/26 : Thanks for your answers guys ! Nevertheless, I was not precise enough. The main issue we have is not with the Site Performance page but with the Crawl Stats one for now. We probably found an issue on our side with some very slow pages (around 3000 ms !!) and we are trying to fix them. I'll keep you posted as soon I'll have some infos. Thanks again !

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• Can't save data for a member in a data form

  - by RahulS

  Implied sharing is an old thing everyone knows the reasons and solutions of that, still little theory about that: With Essbase implied sharing, some members are shared even if you do not explicitly set them as shared. These members are implied shared members. When an implied share relationship is created, each implied member assumes the other member’s value. Essbase assumes (or implies) a shared member relationship in these situations: 1. A parent has only one child 2. A parent has only one child that consolidates to the parent In a Planning form that contains members with an implied sharing relationship, when a value is added for the parent, the child assumes the same value after the form is saved. Likewise, if a value is added for the child, the parent usually assumes the same value after a form is saved.For example, when a calculation script or load rule populates an implied share member, the other implied share member assumes the value of the member populated by the calculation script or load rule. The last value calculated or imported takes precedence. The result is the same whether you refer to the parent or the child as a variable in a calculation script. For more information have a look at: http://docs.oracle.com/cd/E17236_01/epm.1112/hp_admin_11122/ch14s11.html Now the issue which we are going to talk about is We loose data on save even when the parent is dynamic calc and has a single child. A dynamic calc parent to a single child:  If we design the form with following selection: In the data form we will find parent below the member and this is by design whenever you make a selection using commands to select all the member below parent, always children will appear before the parent: Lets try to enter data, Save it Now, try to change the way we selected members Here we go: Now the question again why this behavior: 1. Data from Planning data form passes to Essbase row by row, 2. Because in data form the child member appears before the parent, 3. First, data goes to Essbase for child (SingleStoreChild), 4. Then when Planning passes the data for parent there was #Missing or No data,  5. Over writes the data to #missing. PS: As we know that dynamic calc members are calculated on the fly they are not allocated with any memory in the Essbase, here the parent was dynamic calc and it was pointing to same memory as child in the background, when Planning was passing data to Essbase for second row it has updated the child with missing data.(Little confusing, let me know if you need more explanation) 6. As one of the solutions just change the order of appearance of parent and child. Cheers..!!! Rahul S. https://www.facebook.com/pages/HyperionPlanning/117320818374228

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• Now Shipping! NetAdvantage for .NET 2010 Volume 3!

  The new NetAdvantage Ultimate includes all four Line of Business user interface control sets for ASP .NET, Windows Forms, WPF and Silverlight plus two advanced Data Visualization UI control sets for WPF and Silverlight. With six NetAdvantage products in one robust package, Infragistics® gives you hundreds of controls and infinite development possibilities. Unified XAML Product Strategy-Share Code, Get More Controls In the 10.3 release, Infragistics continues to deliver code parity between the XAML platforms, WPF and Silverlight. In the line of business toolsets, Infragistics introduces the new xamSchedule™, full-featured, Outlook® 2010-style schedule controls, and the new xamDataTree™, a data bound tree view that comfortably handles tens of thousands of tree nodes. Mimicking our Silverlight Drag and Drop Framework, the WPF Drag and Drop Framework CTP empowers you to add your own rich touches to your applications. Track Users' Behaviors New to all NetAdvantage Silverlight controls is the Infragistics Analytics Framework (IGAF), which empowers you to track user behavior in RIAs running on Silverlight 4. Building on the Microsoft® Silverlight Analytics Framework, with IGAF you can analyze the user's behaviors to ensure the experience you want to deliver. NetAdvantage for Windows Forms--New Office® 2010 Ribbon and Application Menu 2010 Create new experiences with Windows Forms. Now with Office 2010 styling, NetAdvantage for Windows Forms has new features such as Microsoft® Office 2010 ribbon and enhanced Infragistics.Excel to export the contents of the high performance WinGrid™ into Microsoft Excel® 2010. The new Windows Message Support enables Infragistics standalone editor controls to process numerous Windows® OS messages, allowing them to respond just like native controls to changes in the Windows environment. Create Faster Web 2.0 Experiences with NetAdvantage for ASP .NET Infragistics continues to push the envelope to deliver the fastest ASP .NET WebForms controls available on the market. Our lightning fast ASP .NET grids are now enhanced with XPS/PDF Exporting and Summary Rows. This release also includes support for jQuery Templating (as a CTP) within our WebDataGrid™ and WebDataTree™ controls allowing you to quickly cut down overall page size. Deliver Business Intelligence with Power, Flexibility and the Office 2010 Experience NetAdvantage for WPF Data Visualization and NetAdvantage for Silverlight Data Visualization help you deliver flexible, powerful and usable end user experiences in Business Intelligence applications. Both suites include the Pivot Grid that delivers the full power of online analytical processing (OLAP) to present multi-dimensional data, sliced and diced in cross-tabulated form for end users to drill down into, interact with and easily extract meaning from the data. Mapping Made Easy 10.3 marks the official release of the WPF Data Visualization xamMap™ control to map anything and everything from geographic to geo-spacial mapping data. Map layers allow you to add successive levels of detail, navigational panes for panning in all directions, color swatch panes that facilitate value scales like Choropleth shading, and scale panes allowing users to zoom-in and out. Both toolsets introduce the first of many relationship maps! With the xamOrgChart™ CTP you can map out organizational charts of up to 50K employees, competitive brackets (think World Cup) and any other relational, organizational map your application needs. http://www.infragistics.com span.fullpost {display:none;}

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• Workflow 4.5 is Awesome, cant wait for 5.0!

  - by JoshReuben

  About 2 years ago I wrote a blog post describing what I would like to see in Workflow vnext: http://geekswithblogs.net/JoshReuben/archive/2010/08/25/workflow-4.0---not-there-yet.aspx At the time WF 4.0 was a little rough around the edges – the State Machine was on codeplex and people were simulating state machines with Flowcharts. Last year I built a near- realtime machine management system using WF 4.0.1 – its managing the internal operations of this device: http://landanano.com/products/commercial   Well WF 4.5 has come a long way – many of my gripes have been addressed: C# expressions - no more VB 'AndAlso' clauses state machine awesomeness - can query current state many designer improvements - Document Outline is so much more succinct than Designer! Separate WCF Service Contract interfaces and ability to generate activities from contract operations ability to rehydrate to updated flow definitions via DynamicUpdateMap and WorkflowIdentity you can read about the new features here: http://msdn.microsoft.com/en-us/library/hh305677(VS.110).aspx   2013 could be the year of Workflow evangelism for .NET, as it comes together as the DSL language. Eg on Azure it could be used to graphically orchestrate between WebRoles, WorkerRoles and AppFabric Queues and the ServiceBus – that would be grand.   Here’s a list of things I’d like to see in Workflow 5.0: Stronger Parallelism support for true multithreaded workflows . A Workflow executes on a single thread – wouldn’t it be great if we had the ability to model TPL DataFlow? Parallel is not really parallel, just allows AsyncCodeActivity.     support for recursion an ExpressionTree activity with an editor design surface a math activity pack return of application level protocol (3.51 WF services) – automatically expose a state machine as a WCF service with bookmark Receive activities generated from OperationContract automatically placed in state transition triggers. A new HTML5 ActivityDesigner control – support with different CSS3  skinnable hooks,  remote connectivity (had to roll my own) A data flow view – crucial to understanding the big picture Ability to refactor a Sequence to custom activity in a separate .xaml file – like Expression Blend does for UserControl state machine global error handling - if all states goto an error state, you quickly get visual spagetti. Now you could nest a state machine, but what if you want an application level protocol whereby each state exposes certain WCF ops. DSL RAD editing - Make the Document Outline into a DSL editor for adding activities  – For WF to really succeed as a higher level of abstraction, It needs to be more productive than raw coding - drag & drop on the designer is currently too slow compared to just typing code. Extensible Wizard API - for pluggable WF editor experience other execution models beyond Sequence, Flowchart & StateMachine: SSIS, Behavior Trees,  Wolfram Model tool – surprise us! improvements to Designer debugging API - SourceLocation is tied to XAML file line number and char position, and ModelService access seems convoluted - why not leverage WPF LogicalTreeHelper / VisualTreeHelper ? Workflow Team , keep on rocking!

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• How to resolve concurrent ramp collisions in 2d platformer?

  - by Shaun Inman

  A bit about the physics engine: Bodies are all rectangles. Bodies are sorted at the beginning of every update loop based on the body-in-motion's horizontal and vertical velocity (to avoid sticky walls/floors). Solid bodies are resolved by testing the body-in-motion's new X with the old Y and adjusting if necessary before testing the new X with the new Y, again adjusting if necessary. Works great. Ramps (rectangles with a flag set indicating bottom-left, bottom-right, etc) are resolved by calculating the ratio of penetration along the x-axis and setting a new Y accordingly (with some checks to make sure the body-in-motion isn't attacking from the tall or flat side, in which case the ramp is treated as a normal rectangle). This also works great. Side-by-side ramps, eg. \/ and /\, work fine but things get jittery and unpredictable when a top-down ramp is directly above a bottom-up ramp, eg. < or > or when a bottom-up ramp runs right up to the ceiling/top-down ramp runs right down to the floor. I've been able to lock it down somewhat by detecting whether the body-in-motion hadFloor when also colliding with a top-down ramp or hadCeiling when also colliding with a bottom-up ramp then resolving by calculating the ratio of penetration along the y-axis and setting the new X accordingly (the opposite of the normal behavior). But as soon as the body-in-motion jumps the hasFloor flag becomes false, the first ramp resolution pushes the body into collision with the second ramp and collision resolution becomes jittery again for a few frames. I'm sure I'm making this more complicated than it needs to be. Can anyone recommend a good resource that outlines the best way to address this problem? (Please don't recommend I use something like Box2d or Chipmunk. Also, "redesign your levels" isn't an answer; the body-in-motion may at times be riding another body-in-motion, eg. a platform, that pushes it into a ramp so I'd like to be able to resolve this properly.) Thanks!

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• Why would more CPU cores on virtual machine slow compile times?

  - by Sid

  [edit#2] If anyone from VMWare can hit me up with a copy of VMWare Fusion, I'd be more than happy to do the same as a VirtualBox vs VMWare comparison. Somehow I suspect the VMWare hypervisor will be better tuned for hyperthreading (see my answer too) I'm seeing something curious. As I increase the number of cores on my Windows 7 x64 virtual machine, the overall compile time increases instead of decreasing. Compiling is usually very well suited for parallel processing as in the middle part (post dependency mapping) you can simply call a compiler instance on each of your .c/.cpp/.cs/whatever file to build partial objects for the linker to take over. So I would have imagined that compiling would actually scale very well with # of cores. But what I'm seeing is: 8 cores: 1.89 sec 4 cores: 1.33 sec 2 cores: 1.24 sec 1 core: 1.15 sec Is this simply a design artifact due to a particular vendor's hypervisor implementation (type2:virtualbox in my case) or something more pervasive across more VMs to make hypervisor implementations more simpler? With so many factors, I seem to be able to make arguments both for and against this behavior - so if someone knows more about this than me, I'd be curious to read your answer. Thanks Sid [edit:addressing comments] @MartinBeckett: Cold compiles were discarded. @MonsterTruck: Couldn't find an opensource project to compile directly. Would be great but can't screwup my dev env right now. @Mr Lister, @philosodad: Have 8 hw threads, using VirtualBox, so should be 1:1 mapping without emulation @Thorbjorn: I have 6.5GB for the VM and a smallish VS2012 project - it's quite unlikely that I'm swapping in/out trashing the page file. @All: If someone can point to an open source VS2010/VS2012 project, that might be a better community reference than my (proprietary) VS2012 project. Orchard and DNN seem to need environment tweaking to compile in VS2012. I really would like to see if someone with VMWare Fusion also sees this (for VMWare vs VirtualBox compartmentalization) Test details: Hardware: Macbook Pro Retina CPU : Core i7 @ 2.3Ghz (quad core, hyper threaded = 8 cores in windows task manager) Memory : 16 GB Disk : 256GB SSD Host OS: Mac OS X 10.8 VM type: VirtualBox 4.1.18 (type 2 hypervisor) Guest OS: Windows 7 x64 SP1 Compiler: VS2012 compiling a solution with 3 C# Azure projects Compile times measure by VS2012 plugin called 'VSCommands' All tests run 5 times, first 2 runs discarded, last 3 averaged

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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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• Is code like this a "train wreck" (in violation of Law of Demeter)?

  - by Michael Kjörling

  Browsing through some code I've written, I came across the following construct which got me thinking. At a first glance, it seems clean enough. Yes, in the actual code the getLocation() method has a slightly more specific name which better describes exactly which location it gets. service.setLocation(this.configuration.getLocation().toString()); In this case, service is an instance variable of a known type, declared within the method. this.configuration comes from being passed in to the class constructor, and is an instance of a class implementing a specific interface (which mandates a public getLocation() method). Hence, the return type of the expression this.configuration.getLocation() is known; specifically in this case, it is a java.net.URL, whereas service.setLocation() wants a String. Since the two types String and URL are not directly compatible, some sort of conversion is required to fit the square peg in the round hole. However, according to the Law of Demeter as cited in Clean Code, a method f in class C should only call methods on C, objects created by or passed as arguments to f, and objects held in instance variables of C. Anything beyond that (the final toString() in my particular case above, unless you consider a temporary object created as a result of the method invocation itself, in which case the whole Law seems to be moot) is disallowed. Is there a valid reasoning why a call like the above, given the constraints listed, should be discouraged or even disallowed? Or am I just being overly nitpicky? If I were to implement a method URLToString() which simply calls toString() on a URL object (such as that returned by getLocation()) passed to it as a parameter, and returns the result, I could wrap the getLocation() call in it to achieve exactly the same result; effectively, I would just move the conversion one step outward. Would that somehow make it acceptable? (It seems to me, intuitively, that it should not make any difference either way, since all that does is move things around a little. However, going by the letter of the Law of Demeter as cited, it would be acceptable, since I would then be operating directly on a parameter to a function.) Would it make any difference if this was about something slightly more exotic than calling toString() on a standard type? When answering, do keep in mind that altering the behavior or API of the type that the service variable is of is not practical. Also, for the sake of argument, let's say that altering the return type of getLocation() is also impractical.

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• How to Remove Extensions From, and Force the Trailing Slash at the End of URLs?

  - by Kronbernkzion

  Example of current file structure: example.com/foo.php example.com/bar.html example.com/directory/ example.com/directory/foo.php example.com/directory/bar.html example.com/cgi-bin/directory/foo.cgi I would like to remove HTML, PHP and CGI extensions from, and then force the trailing slash at the end of URLs. So, it could look like this: example.com/foo/ example.com/bar/ example.com/directory/ example.com/directory/foo/ example.com/directory/bar/ example.com/cgi-bin/directory/foo/ I am very frustrated because I've searched for 17 hours straight for solution and visited more than a few hundred pages on various blogs and forums. I'm not joking. So I think I've done my research. Here is the code that sits in my .htaccess file right now: RewriteCond %{REQUEST_FILENAME} !-d RewriteCond %{REQUEST_FILENAME}\.html -f RewriteRule ^(([^/]+/)*[^./]+)/$ $1.html RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteCond %{REQUEST_URI} !(\.[a-zA-Z0-9]|/)$ RewriteRule (.*)$ /$1/ [R=301,L] As you can see, this code only removes .html (and I'm not very happy with it because I think it could be done a lot simpler). I can remove the extension from PHP files when I rename them to .html through .htaccess, but that's not what I want. I want to remove it straight. This is the first thing I don't know how to do. The second thing is actually very annoying. My .htaccess file with code above, adds .html/ to every string entered after example.com/directory/foo/. So if I enter example.com/directory/foo/bar (obviously /bar doesn't exist since foo is a file), instead of just displaying message that page is not found, it converts it to example.com/directory/foo/bar.html/, then searches for a file for a few seconds and then displays the not found message. This, of course, is bad behavior. So, once again, I need the code in .htaccess to do the following things: Remove .html extension Remove .php extension Remove .cgi extension Force the trailing slash at the end of URLs Requests should behave correctly (no adding trailing slashes or extensions to strings if file or directory doesn't exist on server) Code should be as simple as possible I would very much appreciate any help. And to first person that gives me the solution, I'll send two $50 iTunes Store gift cards for US store. If this offends anyone, I am truly sorry and I apologize. Thanks in advance.

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• Best way to implement a simple bullet trajectory

  - by AirieFenix

  I searched and searched and although it's a fair simple question, I don't find the proper answer but general ideas (which I already have). I have a top-down game and I want to implement a gun which shoots bullets that follow a simple path (no physics nor change of trajectory, just go from A to B thing). a: vector of the position of the gun/player. b: vector of the mouse position (cross-hair). w: the vector of the bullet's trajectory. So, w=b-a. And the position of the bullet = [x=x0+speed*time*normalized w.x , y=y0+speed*time * normalized w.y]. I have the constructor: public Shot(int shipX, int shipY, int mouseX, int mouseY) { //I get mouse with Gdx.input.getX()/getY() ... this.shotTime = TimeUtils.millis(); this.posX = shipX; this.posY = shipY; //I used aVector = aVector.nor() here before but for some reason didn't work float tmp = (float) (Math.pow(mouseX-shipX, 2) + Math.pow(mouseY-shipY, 2)); tmp = (float) Math.sqrt(Math.abs(tmp)); this.vecX = (mouseX-shipX)/tmp; this.vecY = (mouseY-shipY)/tmp; } And here I update the position and draw the shot: public void drawShot(SpriteBatch batch) { this.lifeTime = TimeUtils.millis() - this.shotTime; //position = positionBefore + v*t this.posX = this.posX + this.vecX*this.lifeTime*speed*Gdx.graphics.getDeltaTime(); this.posY = this.posY + this.vecY*this.lifeTime*speed*Gdx.graphics.getDeltaTime(); ... } Now, the behavior of the bullet seems very awkward, not going exactly where my mouse is (it's like the mouse is 30px off) and with a random speed. I know I probably need to open the old algebra book from college but I'd like somebody says if I'm in the right direction (or points me to it); if it's a calculation problem, a code problem or both. Also, is it possible that Gdx.input.getX() gives me non-precise position? Because when I draw the cross-hair it also draws off the cursor position. Sorry for the long post and sorry if it's a very basic question. Thanks!

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• Use Expressions with LINQ to Entities

  - by EltonStoneman

  [Source: http://geekswithblogs.net/EltonStoneman] Recently I've been putting together a generic approach for paging the response from a WCF service. Paging changes the service signature, so it's not as simple as adding a behavior to an existing service in config, but the complexity of the paging is isolated in a generic base class. We're using the Entity Framework talking to SQL Server, so when we ask for a page using LINQ's .Take() method we get a nice efficient SQL query for just the rows we want, with minimal impact on SQL Server and network traffic. We use the maximum ID of the record returned as a high-water mark (rather than using .Skip() to go to the next record), so the approach caters for records being deleted between page requests. In the paged response we include a HasMorePages indicator, computed by comparing the max ID in the page of results to the max ID for the whole resultset - if the latter is bigger, then there are more pages. In some quick performance testing, the paged version of the service performed much more slowly than the unpaged version, which was unexpected. We narrowed it down to the code which gets the max ID for the full resultset - instead of building an efficient MAX() SQL query, EF was returning the whole resultset and then computing the max ID in the service layer. It's easy to reproduce - take this AdventureWorks query:             var context = new AdventureWorksEntities();             var query = from od in context.SalesOrderDetail                         where od.ModifiedDate >= modified                          && od.SalesOrderDetailID.CompareTo(id) > 0                         orderby od.SalesOrderDetailID                         select od;   We can find the maximum SalesOrderDetailID like this:             var maxIdEfficiently = query.Max(od => od.SalesOrderDetailID);   which produces our efficient MAX() SQL query. If we're doing this generically and we already have the ID function in a Func:             Func<SalesOrderDetail, int> idFunc = od => od.SalesOrderDetailID;             var maxIdInefficiently = query.Max(idFunc);   This fetches all the results from the query and then runs the Max() function in code. If you look at the difference in Reflector, the first call passes an Expression to the Max(), while the second call passes a Func. So it's an easy fix - wrap the Func in an Expression:             Expression<Func<SalesOrderDetail, int>> idExpression = od => od.SalesOrderDetailID;             var maxIdEfficientlyAgain = query.Max(idExpression);   - and we're back to running an efficient MAX() statement. Evidently the EF provider can dissect an Expression and build its equivalent in SQL, but it can't do that with Funcs.

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• Many sources of movement in an entity system

  - by Sticky

  I'm fairly new to the idea of entity systems, having read a bunch of stuff (most usefully, this great blog and this answer). Though I'm having a little trouble understanding how something as simple as being able to manipualate the position of an object by an undefined number of sources. That is, I have my entity, which has a position component. I then have some event in the game which tells this entity to move a given distance, in a given time. These events can happen at any time, and will have different values for position and time. The result is that they'd be compounded together. In a traditional OO solution, I'd have some sort of MoveBy class, that contains the distance/time, and an array of those inside my game object class. Each frame, I'd iterate through all the MoveBy, and apply it to the position. If a MoveBy has reached its finish time, remove it from the array. With the entity system, I'm a little confused as how I should replicate this sort of behavior. If there were just one of these at a time, instead of being able to compound them together, it'd be fairly straightforward (I believe) and look something like this: PositionComponent containing x, y MoveByComponent containing x, y, time Entity which has both a PositionComponent and a MoveByComponent MoveBySystem that looks for an entity with both these components, and adds the value of MoveByComponent to the PositionComponent. When the time is reached, it removes the component from that entity. I'm a bit confused as to how I'd do the same thing with many move by's. My initial thoughts are that I would have: PositionComponent, MoveByComponent the same as above MoveByCollectionComponent which contains an array of MoveByComponents MoveByCollectionSystem that looks for an entity with a PositionComponent and a MoveByCollectionComponent, iterating through the MoveByComponents inside it, applying/removing as necessary. I guess this is a more general problem, of having many of the same component, and wanting a corresponding system to act on each one. My entities contain their components inside a hash of component type - component, so strictly have only 1 component of a particular type per entity. Is this the right way to be looking at this? Should an entity only ever have one component of a given type at all times?

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• How to apply effects that occur (or change) over time to characters in a game?

  - by Joshua Harris

  So assume that I have a system that applies Effects to Characters like so: public class Character { private Collection<Effect> _effects; public void AddEffect (Effect e) { e.ApplyTo(this); _effects.Add(e); } public void RemoveEffect (Effect e) { e.RemoveFrom(this); _effects.Remove(e); } } public interface Effect { public void ApplyTo (Character character); public void RemoveFrom (Character character); } Example Effect: Armor Buff for 5 seconds. void someFunction() { // Do Stuff ... Timer armorTimer = new Timer(5 seconds); ArmorBuff armorbuff = new ArmorBuff(); character.AddEffect(armorBuff); armorTimer.Start(); // Do more stuff ... } // Some where else in code public void ArmorTimer_Complete() { character.RemoveEffect(armorBuff); } public class ArmorBuff implements Effect { public void applyTo(Character character) { character.changeArmor(20); } public void removeFrom(Character character) { character.changeArmor(-20); } } Ok, so this example would buff the Characters armor for 5 seconds. Easy to get working. But what about effects that change over the duration of the effect being applied. Two examples come to mind: Damage Over Time: 200 damage every second for 3 seconds. I could mimic this by applying an Effect that lasts for 1 second and has a counter set to 3, then when it is removed it could deal 200 damage, clone itself, decrement the counter of the clone, and apply the clone to the character. If it repeats this until the counter is 0, then you got a damage over time ability. I'm not a huge fan of this approach, but it does describe the behavior exactly. Degenerating Speed Boost: Gain a speed boost that degrades over 3 seconds until you return to your normal speed. This is a bit harder. I can basically do the same thing as above except having timers set to some portion of a second, such that they occur fast enough to give the appearance of degenerating smoothly over time (even though they are really just stepping down incrementally). I feel like you could get away with only 12 steps over a second (maybe less, I would have to test it and see), but this doesn't seem very elegant to me. The only other way to implement this effect would be to change the system so that the Character checks the _effects collection for effects that alter any of the properties any time that they are being used. I could handle this in functions like getCurrentSpeed() and getCurrentArmor(), but you can imagine how much of a hassle it would be to have that kind of overhead every time you want to do a calculation with movement speed (which would be every time you move your character). Is there a better way to deal with these kinds of effects or events?

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• Speaker Notes...

  - by wulfers

  At a .Net User Group meeting this week, I experienced two poorly prepared speakers floundering through presentations….  As a Lead Technologist at the company I work for, I have experience training technical staff and also giving presentations at code camps.  Here are a few guidelines for aspiring speakers you might find helpful…   1.       Do not stand in front of your audience and read your slides.  This is  offensive to your audience and not what they came for...  Your slides are there to reinforce the information you are presenting and to give the audience a little clarification on some terms you may use and as a visual aid for some complicated issues. 2.       Have someone review your presentation (slides, notes, …) who speaks the language you will be presenting in fluently.  Also record at least ten minutes of your presentation and have that same person review that.  One of the speakers this week used the word “Basically” fifty times in less than thirty minutes…  I started to flinch every time he used the term. 3.       Be Prepared  -  before the presentation begins.  Don’t make any last minute changes to your presentation or demo code the night before.  Don’t patch your laptop or demo servers the night before.  If possible create a virtual image that you only use for presentations and use that (refreshed before every presentation). 4.       Know the level of expertise of your audience.  Speaking above or below their abilities will make or break your presentation. 5.       Deliver what you promise. The presentation this week was supposed to be on BDD (Behavior Driven Develpment).  The presenter completely ran off track and 90% of the discussion was how his team mistakenly used TDD (Test Driven Development), and was unhappy with the results.  Based on his loss of focus we only heard a rushed 10 minute presentation on DBB which was a disservice to the audience. 6.       Practice your presentation with your own small team before you try this on a room full of people you don’t know.  A side benefit of doing this with your own team is that you can get candid feedback from your team and also get kudos for training your own team.  I find I can also turn my presentations into technical white papers and get a third benefit from the work I’ve put into a presentation. 7.       Sharpen your own saw.  Pick a topic that is fairly current.  Something you would like to learn about and would benefit your current career path. 8.       Have fun doing it.

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• Creating classed in JavaScript

  - by Renso

  Goal:Creating class instances in JavaScript is not available since you define "classes" in js with object literals. In order to create classical classes like you would in c#, ruby, java, etc, with inheritance and instances.Rather than typical class definitions using object literals, js has a constructor function and the NEW operator that will allow you to new-up a class and optionally provide initial properties to initialize the new object with.The new operator changes the function's context and behavior of the return statement.var Person = function(name) {   this.name = name;};   //Init the personvar dude= new Person("renso");//Validate the instanceassert(dude instanceof Person);When a constructor function is called with the new keyword, the context changes from global window to a new and empty context specific to the instance; "this" will refer in this case to the "dude" context.Here is class pattern that you will need to define your own CLASS emulation library:var Class = function() {   var _class = function() {      this.init.apply(this, arguments);   };   _class.prototype.init = function(){};   return _class;}var Person a new Class();Person.prototype.init = function() {};var person = new Person;In order for the class emulator to support adding functions and properties to static classes as well as object instances of People, change the emulator:var Class = function() {   var _class = function() {      this.init.apply(this, arguments);   };   _class.prototype.init = function(){};   _class.fn = _class.prototype;   _class.fn.parent = _class;   //adding class properties   _class.extend = function(obj) {      var extended = obj.extended;      for(var i in obj) {         _class[i] = obj[i];      };      if(extended) extended(_class);   };   //adding new instances   _class.include = function(obj) {      var included = obj.included;      for(var i in obj) {         _class.fn[i] = obj[i];      };      if(included) included(_class);   };   return _class;}Now you can use it to create and extend your own object instances://adding static functions to the class Personvar Person = new Class();Person.extend({   find: function(name) {/*....*/},      delete: function(id) {/*....*/},});//calling static function findvar person = Person.find('renso');   //adding properties and functions to the class' prototype so that they are available on instances of the class Personvar Person = new Class;Person.extend({   save: function(name) {/*....*/},   delete: function(id) {/*....*/}});var dude = new Person;//calling instance functiondude.save('renso');

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• No description for any page on the website is available in Google despite robots.txt allowing crawling

  - by Abhijit

  I seem to have the weirdest issue with Search Engine Optimization, and I asked the IT folks at my university, I asked people on Joomla forums and I am trying to sort this issue out using Google Webmaster Tools for more than 2 months to little avail. I want to know if I have some blatantly wrong configuration somewhere that is causing search engines to be unable to index this site. I noticed a similar issue with another website I searched for online (ECEGSA - The University of British Columbia at gsa.ece.ubc.ca), making me believe this might be a concern that people might be looking an answer for. Here are the details: The website in question is: http://gsa.ece.umd.edu/. It runs using Joomla 2.5.x (latest). The site was up since around mid December of 2013, and I noticed right from the get go that the site was not being indexed correctly on Google. Specifically I see the following message when I search for the website on Google: A description for this result is not available because of this site's robots.txt – learn more. The thing is in December till around March I used the default Joomla robots.txt file which is: User-agent: * Disallow: /administrator/ Disallow: /cache/ Disallow: /cli/ Disallow: /components/ Disallow: /images/ Disallow: /includes/ Disallow: /installation/ Disallow: /language/ Disallow: /libraries/ Disallow: /logs/ Disallow: /media/ Disallow: /modules/ Disallow: /plugins/ Disallow: /templates/ Disallow: /tmp/ Nothing there should stop Google from searching my website. And even more confusingly, when I go to Google Webmaster tools, under "Blocked URLs" tab, when I try many of the links on the site, they are all shown up as "Allowed". I then tried adding a sitemap, putting it in the robots.txt file. That did not help. Same exact search result, same behavior in the "Blocked URLs" tab on the webmaster tools. Now additionally, the "sitemaps" tab says for several links an error saying "URL is robotted out". I tried those exact links in the "Blocked URLs" and they are allowed! I then tried deleting the robots.txt file. No use. Same exact problem. Here is an example screenshot from Google's Webmaster Tools: At this point I cannot give a rational explanation to why this is happening and neither can anyone in the IT department here. No one on Joomla forums can seem to understand what is going on. Based on what I explained, does it seem that I have somehow set a setting in the robots.txt or in .htaccess or somewhere else, incorrectly?

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• Cheese won't start

  - by Anthony Hohenheim

  I can't start Cheese Webcam Booth. It starts loading and there is a brief moment when the window shows up but then it disappears, like it shuts itself down and it's not in system monitor. My webcam works perfectly in Skype video call. I installed and run Camorama and it gave me an error: Could not connect to video device (/dev/video0) Please check connection When I run the lsusb I get this line for my webcam: Bus 002 Device 002: ID 04f2:b210 Chicony Electronics Co., Ltd And for my graphic card, running lspci: VGA compatible controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 07) It's not a pressing matter, but it bugs my nerves, if it works on Skype, why does Cheese and other programs refuse to run. As I said, it's not a big deal but any help would be appreciated. Running Cheese in terminal: (cheese:11454): Gtk-WARNING **: Attempting to add a widget with type GtkImage to a GtkToggleButton, but as a GtkBin subclass a GtkToggleButton can only contain one widget at a time; it already contains a widget of type GtkLabel (cheese:11454): Gtk-WARNING **: Attempting to add a widget with type GtkImage to a GtkToggleButton, but as a GtkBin subclass a GtkToggleButton can only contain one widget at a time; it already contains a widget of type GtkLabel (cheese:11454): Gtk-WARNING **: Attempting to add a widget with type GtkImage to a GtkToggleButton, but as a GtkBin subclass a GtkToggleButton can only contain one widget at a time; it already contains a widget of type GtkLabel (cheese:11454): Gtk-WARNING **: Attempting to add a widget with type GtkHBox to a GtkButton, but as a GtkBin subclass a GtkButton can only contain one widget at a time; it already contains a widget of type GtkLabel (cheese:11454): Gtk-WARNING **: Attempting to add a widget with type GtkImage to a GtkButton, but as a GtkBin subclass a GtkButton can only contain one widget at a time; it already contains a widget of type GtkLabel (cheese:11454): Gtk-WARNING **: Attempting to add a widget with type GtkHBox to a GtkToggleButton, but as a GtkBin subclass a GtkToggleButton can only contain one widget at a time; it already contains a widget of type GtkLabel (cheese:11454): Gtk-WARNING **: Attempting to add a widget with type GtkImage to a GtkButton, but as a GtkBin subclass a GtkButton can only contain one widget at a time; it already contains a widget of type GtkLabel (cheese:11454): Gdk-WARNING **: The program 'cheese' received an X Window System error. This probably reflects a bug in the program. The error was 'BadDrawable (invalid Pixmap or Window parameter)'. (Details: serial 932 error_code 9 request_code 137 minor_code 9) (Note to programmers: normally, X errors are reported asynchronously; that is, you will receive the error a while after causing it. To debug your program, run it with the --sync command line option to change this behavior. You can then get a meaningful backtrace from your debugger if you break on the gdk_x_error() function.)

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• Ubuntu 13.XX unable to mount USB HDD. Tried everything. I/O error boot sector/file system

  - by XaviGG

  I know that there are many posts related but none of them helped me. I will jump to the last test because it is the one that should work, but it does not. An external HDD with single partition slow NTFS formatted in Windows, empty and clean. Checked for errors, it tells that not errors where found. Moving to Ubutnu 13.04... Gparted throws the first error when trying to read the disk: Input/output error It appears as unknown the content of the disk. Unable to create partition table or format it, getting the same error when trying. If I try to mount it in the terminal it tells me the same, specifying that also there is an I/O error reading the boot sector. I have this problem since I upgraded (always with fresh install) to 13.04. I thought it will be solved by the 13.10 but it has the same behavior. I tried with two different HDD (HD and SSHD) that work perfectly in Windows 7. In 13.04 at least I got a trying of mounting where the icon of the drive started showing and disappearing until finally it disappeared. But now it doesn't even try. Possible causes: -The HDD was my old main HDD, so it had WIN,RECOVERY,SYSTEM,UBU,SWAP partitions. Maybe the way or place where the partition table is defined is not the best for an external HDD but I don't know a lot in that topic. I would appreciate a lot if someone can give me a guideline to convert one of these HDD in a working external HDD. No files to recover, nothing to care about. Just format completely the disk and be able to use it for storing backups without having to move the files first to the windows partition, load windows and then copy them to the external HDD. Because I want to use a file comparator for the backups. Thanks a lot Edit 1: I found an option in Windows to convert it to a dynamic HDD that warns me that I wont be able to run O.S. after changing. I suppose that is what I need because in the current mode I cannot safely extract it. But it tells me an error that it couldn't change the mode.

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• High CPU load for 1:30 minutes when mounting ext4-raid partition

  - by sirion

  I have a raid 5 (software) with 5x2TB drives. I encrypted the raid with cryptsetup and put an ext4-partition on top. In the beginning opening and mounting the raid took less than 10 seconds, now (for a few weeks) mounting alone takes 1:30 minutes and the cpu stays around 93% the whole time: The output of "time sudo mount /dev/mapper/8000 /media/8000" is: real 1m31.952s user 0m0.008s sys 1m25.229s At the same time only one line is added to /var/log/syslog: kernel: [ 2240.921381] EXT4-fs (dm-1): mounted filesystem with ordered data mode. Opts: (null) My Ubuntu-version is "12.04.1 LTS" and no updates are pending. I checked the partition with fsck, but it says that all is ok. The "cryptsetup luksOpen" command only takes a few seconds. I also tried changing the raid-bitmap (as it was suggested in some forum) but it did not change the behaviour. sudo mdadm --grow /dev/md0 -b internal and sudo mdadm --grow /dev/md0 -b none I had the idea that it might be the hardware being slow, but a read test with "sudo hdparm -t /dev/md0" spit out values between 62 and 159 MB/sec: Timing buffered disk reads: 382 MB in 3.00 seconds = 127.14 MB/sec Timing buffered disk reads: 482 MB in 3.02 seconds = 159.62 MB/sec Timing buffered disk reads: 190 MB in 3.03 seconds = 62.65 MB/sec Timing buffered disk reads: 474 MB in 3.02 seconds = 157.12 MB/sec Although I think it is strange that the read rate jumps by more than 100% - could that mean something? The speed test when reading from the mapped (decrypted) device shows similar behavior, although it is of course much slower. "sudo hdparm -t /dev/mapper/8000": Timing buffered disk reads: 56 MB in 3.02 seconds = 18.54 MB/sec Timing buffered disk reads: 122 MB in 3.09 seconds = 39.43 MB/sec Timing buffered disk reads: 134 MB in 3.02 seconds = 44.35 MB/sec The output of a verbose mount "mount -vvv /dev/mapper/8000 /media/8000" does not help much: mount: fstab path: "/etc/fstab" mount: mtab path: "/etc/mtab" mount: lock path: "/etc/mtab~" mount: temp path: "/etc/mtab.tmp" mount: UID: 0 mount: eUID: 0 mount: spec: "/dev/mapper/8000" mount: node: "/media/8000" mount: types: "(null)" mount: opts: "(null)" mount: you didn't specify a filesystem type for /dev/mapper/8000 I will try type ext4 mount: mount(2) syscall: source: "/dev/mapper/8000", target: "/media/8000", filesystemtype: "ext4", mountflags: -1058209792, data: (null) Any idea where I could find additional information on why mounting takes so long, or what additional tests I could run?

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• Are closures with side-effects considered "functional style"?

  - by Giorgio

  Many modern programming languages support some concept of closure, i.e. of a piece of code (a block or a function) that Can be treated as a value, and therefore stored in a variable, passed around to different parts of the code, be defined in one part of a program and invoked in a totally different part of the same program. Can capture variables from the context in which it is defined, and access them when it is later invoked (possibly in a totally different context). Here is an example of a closure written in Scala: def filterList(xs: List[Int], lowerBound: Int): List[Int] = xs.filter(x => x >= lowerBound) The function literal x => x >= lowerBound contains the free variable lowerBound, which is closed (bound) by the argument of the function filterList that has the same name. The closure is passed to the library method filter, which can invoke it repeatedly as a normal function. I have been reading a lot of questions and answers on this site and, as far as I understand, the term closure is often automatically associated with functional programming and functional programming style. The definition of function programming on wikipedia reads: In computer science, functional programming is a programming paradigm that treats computation as the evaluation of mathematical functions and avoids state and mutable data. It emphasizes the application of functions, in contrast to the imperative programming style, which emphasizes changes in state. and further on [...] in functional code, the output value of a function depends only on the arguments that are input to the function [...]. Eliminating side effects can make it much easier to understand and predict the behavior of a program, which is one of the key motivations for the development of functional programming. On the other hand, many closure constructs provided by programming languages allow a closure to capture non-local variables and change them when the closure is invoked, thus producing a side effect on the environment in which they were defined. In this case, closures implement the first idea of functional programming (functions are first-class entities that can be moved around like other values) but neglect the second idea (avoiding side-effects). Is this use of closures with side effects considered functional style or are closures considered a more general construct that can be used both for a functional and a non-functional programming style? Is there any literature on this topic? IMPORTANT NOTE I am not questioning the usefulness of side-effects or of having closures with side effects. Also, I am not interested in a discussion about the advantages / disadvantages of closures with or without side effects. I am only interested to know if using such closures is still considered functional style by the proponent of functional programming or if, on the contrary, their use is discouraged when using a functional style.

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• How to specialize a c++ variadic template?

  - by Serge

  I'm trying to understand c++ variadic templates. I'm not much aware of the correct language to use to explain what I'd like to achieve, so it might be simpler if I provide a bit of code which illustrate what I'd like to achieve. #include <iostream> #include <string> using namespace std; template<int ...A> class TestTemplate1 { public: string getString() { return "Normal"; } }; template<int T, int ...A> string TestTemplate1<2, A...>::getString() { return "Specialized"; } template<typename ...A> class TestTemplate2 { }; int main() { TestTemplate1<1, 2, 3, 4> t1_1; TestTemplate1<1, 2> t1_2; TestTemplate1<> t1_3; TestTemplate1<2> t1_4; TestTemplate2<> t2_1; TestTemplate2<int, double> t2_2; cout << t1_1.getString() << endl; cout << t1_2.getString() << endl; cout << t1_3.getString() << endl; cout << t1_4.getString() << endl; } This throws several errors. error C2333: 'TestTemplate1<::getString' : error in function declaration; skipping function body error C2333: 'TestTemplate1<1,2,3,4::getString' : error in function declaration; skipping function body error C2333: 'TestTemplate1<1,2::getString' : error in function declaration; skipping function body error C2333: 'TestTemplate1<2::getString' : error in function declaration; skipping function body error C2977: 'TestTemplate1' : too many template arguments error C2995: 'std::string TestTemplate1::getString(void)' : function template has already been defined error C3860: template argument list following class template name must list parameters in the order used in template parameter list How can I have a specialized behavior for every TestTemplate1<2, ...> instances like t1_4?

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• Java @Contented annotation to help reduce false sharing

  - by Dave

  See this posting by Aleksey Shipilev for details -- @Contended is something we've wanted for a long time. The JVM provides automatic layout and placement of fields. Usually it'll (a) sort fields by descending size to improve footprint, and (b) pack reference fields so the garbage collector can process a contiguous run of reference fields when tracing. @Contended gives the program a way to provide more explicit guidance with respect to concurrency and false sharing. Using this facility we can sequester hot frequently written shared fields away from other mostly read-only or cold fields. The simple rule is that read-sharing is cheap, and write-sharing is very expensive. We can also pack fields together that tend to be written together by the same thread at about the same time. More generally, we're trying to influence relative field placement to minimize coherency misses. Fields that are accessed closely together in time should be placed proximally in space to promote cache locality. That is, temporal locality should condition spatial locality. Fields accessed together in time should be nearby in space. That having been said, we have to be careful to avoid false sharing and excessive invalidation from coherence traffic. As such, we try to cluster or otherwise sequester fields that tend to written at approximately the same time by the same thread onto the same cache line. Note that there's a tension at play: if we try too hard to minimize single-threaded capacity misses then we can end up with excessive coherency misses running in a parallel environment. Theres no single optimal layout for both single-thread and multithreaded environments. And the ideal layout problem itself is NP-hard. Ideally, a JVM would employ hardware monitoring facilities to detect sharing behavior and change the layout on the fly. That's a bit difficult as we don't yet have the right plumbing to provide efficient and expedient information to the JVM. Hint: we need to disintermediate the OS and hypervisor. Another challenge is that raw field offsets are used in the unsafe facility, so we'd need to address that issue, possibly with an extra level of indirection. Finally, I'd like to be able to pack final fields together as well, as those are known to be read-only.

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