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  • Obstacle Avoidance steering behavior: how can an entity avoid an obstacle while other forces are acting on the entity?

    - by Prog
    I'm trying to implement the Obstacle Avoidance steering behavior in my 2D game. Currently my approach is to apply a force on the entity, in the direction of the normal of the heading, scaled by a number that gets bigger the closer we are to the obstacle. This is supposed to push the entity to the side and avoid the obstacle that blocks it's way. However, in the same time that my entity tries to avoid an obstacle, it Seeks to a point more or less behind the obstacle (which is the reason it needs to avoid the obstacle in the first place). The Seek algorithm constantly applies a force on the entity that pushes it (more or less) in the direction of the obstacle, while the Obstacle Avoidance algorithm constantly applies a force that pushes the entity away (more accurately, to the side) of the obstacle. The result is that sometimes the entity succesfully avoids the obstacle, and sometimes it collides with it, depending on the strength of the avoidance force I'm applying. How can I make sure that a force will succeed in steering the entity in some direction, while other forces are currently acting on the entity? (And while still looking natural). I can't allow entities to collide with obstacles when realistically they should be able to easily avoid them, doesn't matter what they're currently doing. Also, the Obstacle Avoidance algorithm is made exactly for the case where another force is acting on the entity. Otherwise it wouldn't be moving and there would be no need to avoid anything. So maybe I'm missing something. Thanks

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  • nvidia-settings makes one of my dual monitors grey and useless, disables network

    - by Kerrick
    I'm running Ubuntu 12.04 64-bit, Precise Pangolin, with a PNY GTS 250 1GB video card and a monitor plugged into each of the DVI ports. I'm using the proprietary drivers (post-release updates). If I set anything to do with Separate X Screens up in nvidia-settings (and write it to xorg.conf and reboot), my second monitor has a grey background, no menu bar, no ability to have a window on it, the second monitor doesn't get picked up in a screneshot, and if I move my mouse cursor to it it's an ugly black X. Plus, my network is unable to connect to anything. If I subsequently delete /etc/X11/xorg.conf and reboot, everything goes back to working, albeit with a single monitor activated. If I set anything to do with TwinView up in nvidia-settings, my second monitor starts working, but it isn't seen as a second monitor by Ubuntu, so I can't apply color calibration to it separately. Plus, my mouse gets "caught" between the monitors every time I try to move my cursor between the two. What gives? If it helps, this is the xorg.conf that nvidia-settings generates for Separate X Screens.

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  • Resizing partition using Gparted gives "can't have overlapping partitions" error

    - by Marcus
    I just decided to install Ubuntu 12.04 alongside Windows 7 on my Dell laptop. However I didn't do this manually but instead used the "Run Ubuntu alongside Windows 7" option upon installation, and now the partition that Ubuntu runs on has very little space (It's giving me warnings). I'm trying to use Gparted 0.12.1-5 (via a live CD) to give Windows less space and give Ubuntu more. I've managed to remove 100GB from the Windows partition so I now have some unallocated space between Windows and Ubuntu. This is what it looks like inside Ubuntu (not using the live CD, since it won't let me mount a USB to save a screenshot): http://i.stack.imgur.com/0keQq.png So first I take sda4 (extended?) and resize it to the left so it takes up all the unallocated space. Then I resize sda5 (ext4) as well so it takes up all the new space. However, when I hit apply, it fails on the first action (resizing sd4), saying "can't have overlapping partitions". Any ideas as to why this happens? I also tried resizing sda4 by just a few MB so that it definitely didn't overlap anything, but I still got the same error message. To clarify, I am doing it using the CD, I just took the screenshot from Ubuntu. Any help would be greatly appreciated! And again, I can't mount any USB (I'm following the guide on the gparted website but it says "Invalid argument" or something like that) so I couldn't attach the details file from Gparted. If this is needed, I may need some hints on how to solve the USB issue as well. :) Thanks

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  • Software design of a browser-based strategic MMO game

    - by Mehran
    I wonder if there are any known tested software designs for Travian-like browser-based strategic MMO games? I mean how would they implement the server of such games or what is stored in database and what is stored in RAM? Is the state of the world stored in one piece or is it distributed among a number of storage? Does anyone know a resource to study the problems and solutions of creating such games? [UPDATE] Suggested in comments, I'm going to give an example how would I design such a project. Even though I'm not sure if I'm proposing the right one. Having stored the world state in a MongoDB, I would implement an event collection in which all the changes to the world will register. Changes that are meant to happen in the future will come with an action date set to the future and those that are to be carried out immediately will be set to now. Having this datastore as the central point of the system, players will issue their actions as events inserted in datastore. At the other end of the system, I'll have a constant-running software taking out events out of the datastore which are due to be carried out and not done yet. Executing an event means apply some update on the world's state and thus the datastore. As scalable as this design sounds, I'm not sure if it will be worth implementing. For one, it is pointless to cache the datastore as most of updates happen once without any follow ups. For instance if you have the growth of resources in your game, you'll be updating the whole world state periodically in which case, having incorporated a cache, you are keeping the whole world in RAM (which most likely is impossible). So can someone come up with a better design?

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  • Why would 70-persistent-net.rules have no effect?

    - by Wes Felter
    I've got a saucy server with a lot of NICs and they end up with weird names like "rename19". I know interface names can be changed by modifying the /etc/udev/rules.d/70-persistent-net.rules file. The first clue that something is wrong is that that file did not exist even though it's supposed to be created automatically. So I decided to write my own based on advice from Linux From Scratch: ACTION=="add", SUBSYSTEM=="net", BUS=="pci", KERNELS=="0000:06:00.0", NAME="eth0" ACTION=="add", SUBSYSTEM=="net", BUS=="pci", KERNELS=="0000:06:00.1", NAME="eth1" ACTION=="add", SUBSYSTEM=="net", BUS=="pci", KERNELS=="0000:06:00.2", NAME="eth2" ACTION=="add", SUBSYSTEM=="net", BUS=="pci", KERNELS=="0000:06:00.3", NAME="eth3" ACTION=="add", SUBSYSTEM=="net", BUS=="pci", KERNELS=="0000:0c:00.0", NAME="mezz0" ACTION=="add", SUBSYSTEM=="net", BUS=="pci", KERNELS=="0000:0c:00.1", NAME="mezz1" ACTION=="add", SUBSYSTEM=="net", BUS=="pci", KERNELS=="0000:1b:00.0", NAME="slot1a" ACTION=="add", SUBSYSTEM=="net", BUS=="pci", KERNELS=="0000:1b:00.1", NAME="slot1b" ACTION=="add", SUBSYSTEM=="net", BUS=="pci", KERNELS=="0000:20:00.0", NAME="slot2a" ACTION=="add", SUBSYSTEM=="net", BUS=="pci", KERNELS=="0000:20:00.1", NAME="slot2b" ACTION=="add", SUBSYSTEM=="net", BUS=="pci", KERNELS=="0000:11:00.0", NAME="slot3a" ACTION=="add", SUBSYSTEM=="net", BUS=="pci", KERNELS=="0000:11:00.1", NAME="slot3b" ACTION=="add", SUBSYSTEM=="net", BUS=="pci", KERNELS=="0000:8b:00.0", NAME="slot4a" ACTION=="add", SUBSYSTEM=="net", BUS=="pci", KERNELS=="0000:8b:00.1", NAME="slot4b" ACTION=="add", SUBSYSTEM=="net", BUS=="pci", KERNELS=="0000:90:00.0", NAME="slot5a" ACTION=="add", SUBSYSTEM=="net", BUS=="pci", KERNELS=="0000:90:00.1", NAME="slot5b" ACTION=="add", SUBSYSTEM=="net", BUS=="pci", KERNELS=="0000:95:00.0", NAME="slot6a" ACTION=="add", SUBSYSTEM=="net", BUS=="pci", KERNELS=="0000:95:00.1", NAME="slot6b" (I'm matching on PCI IDs instead of MAC addresses because I have multiple identical machines that I want to apply this configuration to.) After rebooting, nothing has changed. It's like these rules aren't even being read. There's not much going on in dmesg either: $ dmesg | grep udev [ 3.196629] systemd-udevd[323]: starting version 204 [ 6.719140] systemd-udevd[550]: starting version 204 [ 38.695050] init: udev-fallback-graphics main process (1658) terminated with status 1

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  • Huge procedurally generated 'wilderness' worlds

    - by The Communist Duck
    I'm sure you all know of games like Dwarf Fortress - massive, procedural generated wilderness and land. Something like this, taken from this very useful article. However, I was wondering how I could apply this to a much larger scale; the scale of Minecraft comes to mind (isn't that something like 8x the size of the Earth's surface?). Pseudo-infinite, I think the best term would be. The article talks about fractal perlin noise. I am no way an expert on it, but I get the general idea (it's some kind of randomly generated noise which is semi-coherent, so not just random pixel values). I could just define regions X by X in size, add some region loading type stuff, and have one bit of noise generating a region. But this would result in just huge amounts of islands. On the other extreme, I don't think I can really generate a supermassive sheet of perlin noise. And it would just be one big island, I think. I am pretty sure Perlin noise, or some noise, would be the answer in some way. I mean, the map is really nice looking. And you could replace the ascii with tiles, and get something very nice looking. Anyone have any ideas? Thanks. :D

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  • Oracle Solaris Remote Lab (OSRL) Fact Sheet

    - by user13333379
    The Oracle Solaris Remote Lab allows independent software vendors (ISVs) to test and qualify their applications in a self service Solaris cloud. ISVs who are Oracle Partner Network Gold members with a specialization in the Solaris knowledge zone can apply for free access in OPN. The lab offers the following features to it's users: Lifetime of project: 45 days (extensions granted on demand)  Up to 5 virtual machines in a private network  Virtual Machine technology: Solaris zones  Resources per VM processor support: SPARC or x86  OS version: OracleSolaris 11.0 4GB physical memory  4GB swap space  10GB local filesystem storage  10GB network filesystem (NFS) mounted on all virtual machines Networking configuration The only external network routes are to Partner's other Virtual Machines  No network routing to the Internet  The SMB (CIFS) sharing protocol is not available between Virtual Machines  Device Access  Applications that assume the existence of /devices will not run in a Virtual Machine  Applications that use eeprom to modify SPARC eeprom setting will not run in a Virtual Machine The following utilities do not work properly in Virtual Machines:  add_drv, disks, prtconf, prtdiag, rem_dev Access technology: Secure Global Desktop, file up and download root access within VM Available VM templates (both processor architectures) Oracle Database 11g Release 2 (11.2.0.3) for Solaris with Oracle Enterprise Manager 11g Weblogic 12c  SAMP: Apache http server, PHP, MySQL, phpadmin on all templates and images: Oracle Solaris Studio 12.3 for application development  More resources: Online application for Oracle Solaris remote Lab Developer Webinar about the Oracle Solaris Remote Lab Everything an Oracle Solaris Developer needs...

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  • Oracle Solaris Remote Lab (OSRL) Fact Sheet

    - by user13333379
    The Oracle Solaris Remote Lab allows independent software vendors (ISVs) to test and qualify their applications in a self service Solaris cloud. ISVs who are Oracle Partner Network Gold members with a specialization in the Solaris knowledge zone can apply for free access in OPN. The lab offers the following features to it's users: Lifetime of project: 45 days (extensions granted on demand)  Up to 5 virtual machines in a private network  Virtual Machine technology: Solaris zones  Resources per VM processor support: SPARC or x86  OS version: OracleSolaris 11.0 4GB physical memory  4GB swap space  10GB local filesystem storage  10GB network filesystem (NFS) mounted on all virtual machines Networking configuration The only external network routes are to Partner's other Virtual Machines  No network routing to the Internet  The SMB (CIFS) sharing protocol is not available between Virtual Machines  Device Access  Applications that assume the existence of /devices will not run in a Virtual Machine  Applications that use eeprom to modify SPARC eeprom setting will not run in a Virtual Machine The following utilities do not work properly in Virtual Machines:  add_drv, disks, prtconf, prtdiag, rem_dev Access technology: Secure Global Desktop, file up and download root access within VM Available VM templates (both processor architectures) Oracle Database 11g Release 2 (11.2.0.3) for Solaris with Oracle Enterprise Manager 11g Weblogic 12c  SAMP: Apache http server, PHP, MySQL, phpadmin on all templates and images: Oracle Solaris Studio 12.3 for application development  More resources: Online application for Oracle Solaris remote Lab Developer Webinar about the Oracle Solaris Remote Lab Everything an Oracle Solaris Developer needs...

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  • A Simple Solution For NetBeans RCP Apps That Need A Groovy Editor

    - by Geertjan
    Take a look at Nils Hoffmann's metabolomic analyzer, especially at the Groovy editor contained within it: Obviously, it would be cool if the Groovy editor in the app above were to have syntax coloring and other editor features helpful in coding Groovy. However, as I showed in If You Include the Groovy Editor, there are multiple dependencies that the NetBeans Groovy support has on other modules that would be completely superfluous in the above application, while they'd make the app much heavier than it is, simply because of all the Groovy dependencies. But today I thought of a simple solution. Why not take the Groovy.g file (i.e., the ANTLR definition), such as this one [though that's probably not the most up to date one, wondering how to find the most up to date one] and then apply the content of this screencast (made by me) to the Groovy.g file: Within a few minutes, you should end up with Groovy syntax coloring. OK, so that's not a full blown Groovy editor, but syntax coloring is surely a cool thing to have in the app with which this blog entry started? Sure, this means creating a new Groovy editor from scratch. But the point is that doing so can be very simple, i.e., the syntax coloring can simply be generated via the simple instructions above. I'm going to try it myself in the next few days, but would be cool if others out there would try this too!

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  • Oracle Recruitment and Gild Wants You to Have an Apple iPad

    - by david.talamelli
    Oracle and Gild Present the Oracle Coding Series You are invited to participate. Winners will receive national recognition and an Apple iPad. Oracle is inviting elite technologists across India to compete in the Oracle Coding Series. Your credentials have qualified you to participate in the Series. The Oracle Coding Series is a set of five coding competitions that will run from the middle of May to the end of June. Each competition covers a different technology. Competitions are fun and challenging, and take about 15 minutes to complete. The winner of each competition will receive national recognition and win an Apple iPad. Oracle has partnered with Gild.com to host the competition series and select the champions. You may also browse through Oracle's current top job openings - available exclusively on Gild.com. You can apply right on Gild.com, receive immediate feedback and get fast tracked based on your credentials. Good luck. Jan Ackerman Vice President, Recruiting - JAPAC Enter and Compete Now....Best of Luck.

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  • Prevent Looping and Inefficient Rule Executions by C2B2

    - by JuergenKress
    This recipe, taken from the recently published Oracle SOA Suite 11g Performance Cookbook gives guidance on how to avoid rule executions that will loop, potentially indefinitely! We’ll use an inbound XML fact and a local RL fact as an example. Getting ready You’ll need access to a SOA composite containing an Oracle Business Rules component in JDeveloper to apply this recipe. We’ll assume you have an XSD schema with an input type RequestInput containing input and bonus String types, and output String value called output in a type ResponseOutput. These aren’t efficient but serve as an example. We’ll step through adding a rule to a composite and creating an RL fact. How to do it... Open a SOA composite. Right click on the Project and select Business Rules (Service Components), use the search box if it is not immediately available. Give the rule a name and click the green plus icon to add the RequestInput to the input and ResponseOutput to the output types. Read the complete article here. SOA & BPM Partner Community For regular information on Oracle SOA Suite become a member in the SOA & BPM Partner Community for registration please visit www.oracle.com/goto/emea/soa (OPN account required) If you need support with your account please contact the Oracle Partner Business Center. Blog Twitter LinkedIn Facebook Wiki Technorati Tags: C2B2,looping,SOA Community,Oracle SOA,Oracle BPM,Community,OPN,Jürgen Kress

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  • How do I adjust the origin of rotation for a group of sprites?

    - by Jon
    I am currently grouping sprites together, then applying a rotation transformation on draw: private void UpdateMatrix(ref Vector2 origin, float radians) { Vector3 matrixorigin = new Vector3(origin, 0); _rotationMatrix = Matrix.CreateTranslation(-matrixorigin) * Matrix.CreateRotationZ(radians) * Matrix.CreateTranslation(matrixorigin); } Where the origin is the Centermost point of my group of sprites. I apply this transformation to each sprite in the group. My problem is that when I adjust the point of origin, my entire sprite group will re-position itself on screen. How could I differentiate the point of rotation used in the transformation, from the position of the sprite group? Is there a better way of creating this transformation matrix? EDIT Here is the relevant part of the Draw() function: Matrix allTransforms = _rotationMatrix * camera.GetTransformation(); spriteBatch.Begin(SpriteSortMode.BackToFront, null, null, null, null, null, allTransforms); for (int i = 0; i < _map.AllParts.Count; i++) { for (int j = 0; j < _map.AllParts[0].Count; j++) { spriteBatch.Draw(_map.AllParts[i][j].Texture, _map.AllParts[i][j].Position, null, Color.White, 0, _map.AllParts[i][j].Origin, 1.0f, SpriteEffects.None, 0f); } } This all works fine, again, the problem is that when a rotation is set and the point of origin is changed, the sprite group's position is offset on screen. I am trying to figure out a way to adjust the point of origin without causing a shift in position. EDIT 2 At this point, I'm looking for workarounds as this is not working. Does anyone know of a better way to rotate a group of sprites in XNA? I need a method that will allow me to modify the point of rotation (origin) without affecting the position of the sprite group on screen.

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  • Applying Interactive Sorting to Multiple Columns in Reporting Services

    - by smisner
    A nice feature that appeared first in SQL Server 2008 is the ability to allow the user to click a column header to sort that column. It defaults to an ascending sort first, but you can click the column again to switch to a descending sort. You can learn more about interactive sorts in general at the Adding Interactive Sort to a Data Region in Books Online. Not mentioned in the article is how to apply interactive sorting to multiple columns, hence the reason for this post! Let’s say that I have a simple table like this: To enable interactive sorting, I open the Text Box properties for each of the column headers – the ones in the top row. Here’s an example of how I set up basic interactive sorting: Now when I preview the report, I see icons appear in each text box on the header row to indicate that interactive sorting is enabled. The initial sort order that displays when you preview the report depends on how you design the report. In this case, the report sorts by Sales Territory Group first, and then by Calendar Year. Interactive sorting overrides the report design. So let’s say that I want to sort first by Calendar Year, and then by Sales Territory Group. To do this, I click the arrow to the right of Calendar Year, and then, while pressing the Shift key, I click the arrow to the right of Sales Territory Group twice (once for ascending order and then a second time for descending order). Now my report looks like this: This technique only seems to work when you have a minimum of three columns configured with interactive sorting. If I remove the property from one of the columns in the above example, and try to use the interactive sorting on the remaining two columns, I can sort only the first column. The sort on the second column gets ignored. I don’t know if that’s by design or a bug, but I do know that’s what I’m experiencing when I try it out!

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  • Why the R# Method Group Refactoring is Evil

    - by Liam McLennan
    The refactoring I’m talking about is recommended by resharper when it sees a lambda that consists entirely of a method call that is passed the object that is the parameter to the lambda. Here is an example: public class IWishIWasAScriptingLanguage { public void SoIWouldntNeedAllThisJunk() { (new List<int> {1, 2, 3, 4}).Select(n => IsEven(n)); } private bool IsEven(int number) { return number%2 == 0; } } When resharper gets to n => IsEven(n) it underlines the lambda with a green squiggly telling me that the code can be replaced with a method group. If I apply the refactoring the code becomes: public class IWishIWasAScriptingLanguage { public void SoIWouldntNeedAllThisJunk() { (new List<int> {1, 2, 3, 4}).Select(IsEven); } private bool IsEven(int number) { return number%2 == 0; } } The method group syntax implies that the lambda’s parameter is the same as the IsEven method’s parameter. So a readable, explicit syntax has been replaced with an obfuscated, implicit syntax. That is why the method group refactoring is evil.

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  • Why isn't there a culture of paying for frameworks?

    - by Marty Pitt
    One of the side effects of the recent trend of "Lean" startups, and the app store era, is that consumers are more acclimatised to paying small prices for small games / products. Eg.: Online SAAS that charges ~$5 / month (the basecamp style of product) Games which are short, fun, and cheap ($0.99 from the app store This market has been defined by "doing one thing well, and charging people for it." DHH of Rails / 37 Signals fame argues that if your website isn't going to make money, don't bother making it. Why doesn't the same rule apply to frameworks? There are lots of software framework projects out there - many which are mature and feature-rich, which offer developers significant value, yet there doesn't seem to be a market or culture of paying for these. It seems that the projects which do charge money are often things like UI component toolsets, and are often marginalized in favour of free alternatives. Why is this? Surely programmers / businesses see the value in contributing back to projects such as Ruby, Rails, Hibernate, Spring, Ant, Groovy, Gradle, (the list goes on). I'm not suggesting that these frameworks should start charging for anyone who wants to use them, but that there must be a meaningful business model that would allow the developers to earn money from the time they invest developing the framework. Any thoughts as to why this model hasn't emerged / succeeded?

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  • Little mysterious RowMatch

    - by kishore.kondepudi(at)oracle.com
    Incidentally this was the first piece of code i ever wrote in ADF.The requirement was we have tax rates which are read from a table.And there can be different type of tax rates called certificates or exceptions based on the rate_type column in the tax rates table.The simplest design i chose was to create an EO on the tax rates table and create two VO's called CertificateVO and ExceptionVO based on the same EO.So far so good.I wrote all the business logic in the EO and completed the model project.The CertificateVO has the query as select * from tax_rates TaxRateEO where rate_type='CERTIFICATE' and similary the ExceptionVO is also built.The UI is pretty simple and it has two tabs called Certificates and Exceptions and each table has a button to create a tax rate.The certificate tab is driven by CertificateVO and exception tab is driven by ExceptionVO.The CertificateVO has default value of rate_type set to 'CERTIFICATE' and ExceptionVO has default value of rate_type to 'EXCEPTION' to default values for new records.So far so good.But on running the UI i noticed a strange thing,When i create a new row in Certificate i see the same row in Exception too and vice-versa.i.e; what ever row i create in one VO it also appears in the second one although it shouldn't be.I couldn't understand the reason for behavior even though an explicit where clause is present.Digging through documentation i found that ADF doesnt apply the where clause to new rows instead it applies something called as RowMatch to them.RowMatch in simple terms is a where condition applied to the VO rows at runtime.Since we had both VO's based on the same EO we have the same entity cache.The filter factor for new rows to be shown in VO at runtime is actually RowMatch than the where clause defined in the VO.The default RowMatch is empty as a result any new row appears in both the VO's since its from same entity cache.The solution to this problem is to use polymorphic view objects which can do the row filter based on configuration or override the getRowMatch() method in the VOImpl and pass the custom where filter instead of default RowMatch.Eg:@Overridepublic RowMatch getRowMatch(){    return new RowMatch("rate_type='CERTIFICATE'");}similarly for ExceptionVO too.With proper RowMatch in place new rows will route themselves to appropriate VO.PS: The behavior(Same row pushed to both VO's from entity cache) is also called as ViewLink Consistency.Try it out!

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  • 12.04, nvidia-settings makes one of my dual monitors grey and useless, disables network

    - by Kerrick
    I'm running Ubuntu 12.04 64-bit, Precise Pangolin, with a PNY GTS 250 1GB video card and a monitor plugged into each of the DVI ports. I'm using the proprietary drivers (post-release updates). If I set anything to do with Separate X Screens up in nvidia-settings (and write it to xorg.conf and reboot), my second monitor has a grey background, no menu bar, no ability to have a window on it, the second monitor doesn't get picked up in a screneshot, and if I move my mouse cursor to it it's an ugly black X. Plus, my network is unable to connect to anything. If I subsequently delete /etc/X11/xorg.conf and reboot, everything goes back to working, albeit with a single monitor activated. If I set anything to do with TwinView up in nvidia-settings, my second monitor starts working, but it isn't seen as a second monitor by Ubuntu, so I can't apply color calibration to it separately. Plus, my mouse gets "caught" between the monitors every time I try to move my cursor between the two. What gives? If it helps, this is the xorg.conf that nvidia-settings generates for Separate X Screens.

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  • Interfaces and Virtuals Everywhere????

    - by David V. Corbin
    First a disclaimer; this post is about micro-optimization of C# programs and does not apply to most common scenarios - but when it does, it is important to know. Many developers are in the habit of declaring member virtual to allow for future expansion or using interface based designs1. Few of these developers think about what the runtime performance impact of this decision is. A simple test will show that this decision can have a serious impact. For our purposes, we used a simple loop to time the execution of 1 billion calls to both non-virtual and virtual implementations of a method that took no parameters and had a void return type: Direct Call:     1.5uS Virtual Call:   13.0uS The overhead of the call increased by nearly an order of magnitude! Once again, it is important to realize that if the method does anything of significance then this ratio drops quite quickly. If the method does just 1mS of work, then the differential only accounts for a 1% decrease in performance. Additionally the method in question must be called thousands of times in order to produce a meaqsurable impact at the application level. Yet let us consider a situation such as the per-pixel processing of a graphics processing application. Here we may have a method which is called millions of times and even the slightest increase in overhead can have significant ramification. In this case using either explicit virtuals or interface based constructs is likely to be a mistake. In conclusion, good design principles should always be the driving force behind descisions such as these; but remember that these decisions do not come for free.   1) When a concrete class member implements an interface it does not need to be explicitly marked as virtual (unless, of course, it is to be overriden in a derived concerete class). Nevertheless, when accessed via the interface it behaves exactly as if it had been marked as virtual.

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  • Sharing swap space between Windows and Ubuntu

    - by Leftium
    This Linux Swap Space Mini-HOWTO describes how to share swap space between Windows and Linux. Do these instructions still apply to Ubuntu in 2011? How should I modify the steps for Ubuntu? Is there a better approach to sharing swap space? Based on the HOWTO, it seems best to create a dedicated NTFS swap partition: Dedicated so the swap file will be contiguous and remain unfragmented. NTFS so both Windows and Ubuntu can read/write to it. (Or is FAT32 better for this purpose?) Then, configure Ubuntu to prepare the swap space for use by Linux on start up; by Windows on shut down. I want to dual boot Ubuntu and Windows 7 on my X301 laptop. However, my laptop only has a 64 GB SDD, so I would like to conserve as much disk space as possible. update: There is an alternate method using a special driver for Windows that let you use a Linux swap partition for temporary storage like a RAM-disk, but it doesn't seem to be as good...

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  • Common request: export #Tabular model and data to #PowerPivot

    - by Marco Russo (SQLBI)
    I received this request in many courses, messages and also forum discussions: having an Analysis Services Tabular model, it would be nice being able to extract a correspondent PowerPivot data model. In order of priority, here are the specific feature people (including me) would like to see: Create an empty PowerPivot workbook with the same data model of a Tabular model Change the connections of the tables in the PowerPivot workbook extracting data from the Tabular data model Every table should have an EVALUATE ‘TableName’ query in DAX Apply a filter to data extracted from every table For example, you might want to extract all data for a single country or year or customer group Using the same technique of applying filter used for role based security would be nice Expose an API to automate the process of creating a PowerPivot workbook Use case: prepare one workbook for every employee containing only its data, that he can use offline Common request for salespeople who want a mini-BI tool to use in front of the customer/lead/supplier, regardless of a connection available This feature would increase the adoption of PowerPivot and Tabular (and, therefore, Business Intelligence licenses instead of Standard), and would probably raise the sales of Office 2013 / Office 365 driven by ISV, who are the companies who requests this feature more. If Microsoft would do this, it would be acceptable it only works on Office 2013. But if a third-party will do that, it will make sense (for their revenues) to cover both Excel 2010 and Excel 2013. Another important reason for this feature is that the “Offline cube” feature that you have in Excel is not available when your PivotTable is connected to a Tabular model, but it can only be used when you connect to Analysis Services Multidimensional. If you think this is an important features, you can vote this Connect item.

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  • Refactoring and Open / Closed principle

    - by Giorgio
    I have recently being reading a web site about clean code development (I do not put a link here because it is not in English). One of the principles advertised by this site is the Open Closed Principle: each software component should be open for extension and closed for modification. E.g., when we have implemented and tested a class, we should only modify it to fix bugs or to add new functionality (e.g. new methods that do not influence the existing ones). The existing functionality and implementation should not be changed. I normally apply this principle by defining an interface I and a corresponding implementation class A. When class A has become stable (implemented and tested), I normally do not modify it too much (possibly, not at all), i.e. If new requirements arrive (e.g. performance, or a totally new implementation of the interface) that require big changes to the code, I write a new implementation B, and keep using A as long as B is not mature. When B is mature, all that is needed is to change how I is instantiated. If the new requirements suggest a change to the interface as well, I define a new interface I' and a new implementation A'. So I, A are frozen and remain the implementation for the production system as long as I' and A' are not stable enough to replace them. So, in view of these observation, I was a bit surprised that the web page then suggested the use of complex refactorings, "... because it is not possible to write code directly in its final form." Isn't there a contradiction / conflict between enforcing the Open / Closed Principle and suggesting the use of complex refactorings as a best practice? Or the idea here is that one can use complex refactorings during the development of a class A, but when that class has been tested successfully it should be frozen?

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  • Book: DevOps for Developers

    - by Tori Wieldt
    We all know development and operations often act like silos, with "Just throw it over the wall!" being the battle cry. Many organizations unwittingly contribute to gaps between teams, with management by (competing) objectives; a clash of Agile practices vs. more conservative approaches; and teams using different sets of tools, such as Nginx, OpenEJB, and Windows on developers' machines and Apache, Glassfish, and Linux on production machines. At best, you've got sub-optimal collaboration, at worst, you've got the Hatfields and the McCoys.  The book DevOps for Developers helps bridge the gap between development and operations by aligning incentives and sharing approaches for processes and tools. It introduces DevOps as a modern way of bringing development and operations together. It also means to broaden the usage of Agile practices to operations to foster collaboration and streamline the entire software delivery process in a holistic way. Some single aspects of DevOps may not be new, for example, you may have used the tool Puppet for years already, but with a new mindset ("my job is not just to code, it's to serve the customer in the best way possible") and a complete set of recipes, you'll be well on your way to success. DevOps for Developers also by provides real-world use cases (e.g., how to use Kanban or how to release software). It provides a way to be successful in the real development/operations world. DevOps for Developers is written my Michael Hutterman, Java Champion, and founder of the Cologne Java User Group. "With DevOps for Developers, developers can learn to apply patterns to improve collaboration between development and operations as well as recipes for processes and tools to streamline the delivery process," Hutterman explains.

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  • Simple Architecture Verification

    - by Jean Carlos Suárez Marranzini
    I just made an architecture for an application with the function of scoring, saving and loading tennis games. The architecture has 2 kinds of elements: components & layers. Components: Standalone elements that can be consumed by other components or by layers. They might also consume functionality from the model/bottom layer. Layers: Software components whose functionality rests on previous layers (except for the model layer). -Layers: -Models: Data and it's behavior. -Controllers: A layer that allows interaction between the views and the models. -Views: The presentation layer for interacting with the user. -Components: -Persistence: Makes sure the game data can be stored away for later retrieval. -Time Machine: Records changes in the game through time so it's possible to navigate the game back and forth. -Settings: Contains the settings that determine how some of the game logic will apply. -Game Engine: Contains all the game logic, which it applies to the game data to determine the path the game should take. This is an image of the architecture (I don't have enough rep to post images): http://i49.tinypic.com/35lt5a9.png The requierements which this architecture should satisfy are the following: Save & load games. Move through game history and see how the scoreboard changes as the game evolves. Tie-breaks must be properly managed. Games must be classified by hit-type. Every point can be modified. Match name and player names must be stored. Game logic must be configurable by the user. I would really appreciate any kind of advice or comments on this architecture. To see if it is well built and makes sense as a whole. I took the idea from this link. http://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller

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  • We'll be at QCon San Francisco!

    - by Carlos Chang
    Oracle Technology Network is a Platinum sponsor at QCon San Francisco. Don’t miss these great developer focused sessions: Shay Shmeltzer - How we simplified Web, Mobile and Cloud development for our own developers? - the Oracle Story Over the past several years, Oracle has beendeveloping a new set of enterprise applications in what is probably one of the largest Java based development project in the world. How do you take 3000 developers and make them productive? How do you insure the delivery of cutting edge UIs for both Mobile and Web channels? How do you enable Cloud based development and deployment? Come and learn how we did it at Oracle, and see how the same technologies and methodologies can apply to your development efforts. Dan Smith - Project Lambda in Java 8 Java SE 8 will include major enhancements to the Java Programming Language and its core libraries.  This suite of new features, known as Project Lambda in the OpenJDK community, includes lambda expressions, default methods, and parallel collections (and much more!).  The result will be a next-generation Java programming experience with more flexibility and better abstractions.   This talk will introduce the new Java features and offer a behind-the-scenes view of how they evolved and why they work the way that they do. Arun Gupta - JSR 356: Building HTML5 WebSocket Applications in Java The family of HTML5 technologies has pushed the pendulum away from rich client technologies and toward ever-more-capable Web clients running on today’s browsers. In particular, WebSocket brings new opportunities for efficient peer-to-peer communication, providing the basis for a new generation of interactive and “live” Web applications. This session examines the efforts under way to support WebSocket in the Java programming model, from its base-level integration in the Java Servlet and Java EE containers to a new, easy-to-use API and toolset that are destined to become part of the standard Java platform. The complete conference schedule is here: http://qconsf.com/sf2012/schedule/wednesday.jsp But wait, there’s more! At the Oracle booth, we’ll also be covering: Oracle ADF Mobile Oracle Developer Cloud Service Oracle ADF Essentials NetBeans Project Easel Hope to see you there! 

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  • Best practices for using namespaces in C++.

    - by Dima
    I have read Uncle Bob's Clean Code a few months ago, and it has had a profound impact on the way I write code. Even if it seemed like he was repeating things that every programmer should know, putting them all together and putting them into practice does result in much cleaner code. In particular, I found breaking up large functions into many tiny functions, and breaking up large classes into many tiny classes to be incredibly useful. Now for the question. The book's examples are all in Java, while I have been working in C++ for the past several years. How would the ideas in Clean Code extend to the use of namespaces, which do not exist in Java? (Yes, I know about the Java packages, but it is not really the same.) Does it make sense to apply the idea of creating many tiny entities, each with a clearly define responsibility, to namespaces? Should a small group of related classes always be wrapped in a namespace? Is this the way to manage the complexity of having lots of tiny classes, or would the cost of managing lots of namespaces be prohibitive?

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