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• Upgrading Fusion Middleware 11.1.1.x to 11.1.1.4

  - by James Taylor

  This is a follow on from my previous post where we upgraded 11.1.1.2 to 11.1.1.3. The instructions I provide here will work for Fusion Middleware 11.1.1.2 and 11.1.1.3 wanting to upgrade to 11.1.1.4. In this example I’m just upgrading SOA Suite on OEL 64bit but the steps will be the same, some of the downloads may be different based on your environment. To upgrade to 11.1.1.4 you need to have access to http://support.oracle.com as this is where the downloads reside. Oracle provides 11.1.1.4 as a standalone download so you can do a fresh install if required using OTN downloads (http://www.oracle.com/technetwork/indexes/downloads/index.html). The high level steps to upgrade are as follows: Download software Shutdown you SOA Environment Upgrade WLS to 11.1.1.4 Upgrade SOA Suite to 11.1.1.4 Upgrade OSB to 11.1.1.4 Upgrade MSD Schemas Identify the downloads you require for your install. You will need the WebLogic Server Upgrade and the additional product downloads. If you are using 64bit then use the generic version. The downloads are found from the following location - http://download.oracle.com/docs/html/E18749_01/download_readme.htm#BABDDIIC For the purpose of this post I downloaded the following patches 11060985 – WLS Server Generic 11060960 – SOA Suite 11061005 – OSB Suite You must also download the 11.1.1.4 RCU tool to upgrade the DB schemas. It is available via OTN, or, Oracle Support, I have provided the link from Oracle Support.  11060956 – RCU Make sure you have set the Java executable in your PATH e.g. export PATH=$JAVA_HOME/bin:$PATH  Make sure all your WebLogic environment has been shut down before performing the upgrade. Extract the WLS patch 11060985 to a temporary directory and start the installer java –jar wls1034_upgrade_generic.jar Please note if you are not running 64BIT then the upgrade executable will be just a bin file which you can execute directly. Chose the right Oracle home for your WebLogic Server install. In the Register for Security Updates you can enter your details or just click Next. If you do not enter details confirm that you don’t want to receive these updates Select the products you want to upgrade and select next. It is recommended that you accept the defaults. Confirm the directories that will be upgraded Upgrade of WLS ahs been completed   Extract your both SOA downloads to a temporary directory and run the installer found in Disk1 ./runInstaller -jreLoc /java/jdk1.6.0_20/jre Please note that the java location and version may be different for your environment Skip the Software Updates Ensure your system meets the prerequisites Set the Oracle home for your SOA install. You will be asked to confirm that you want to upgrade, click Yes Choose your application server. Since you are upgrading from 11.1.1.x you will be on WebLogic Start the Install Installation Upgrade of SOA Suite completed accept the default to finish.   In my environment I have OSB installed so I need to upgrade this next. If you don’t have SOA Suite you can go straight to completing the DB Schema updates at Step 24.  Extract the OSB upgrade files to a temporary directory and execute the installer found in the Disk1 folder. ./runInstaller -jreLoc /java/jdk1.6.0_20/jre Skip the software updates Select the Oracle home for your environment Accept the warning to continue the upgrade Point to the location of your WebLogic Server installation Install the OSB upgrade Upgrade has been completed accept the defaults Change directory to $MW_HOME/oracle_common/bin where the Patch Set Assistant is installed Execute the following command to update the MDS schema. Please not for my examples I have the context set to DEV. your may be different. This means that all my schemas are prefixed by DEV. ./psa -dbType Oracle -dbConnectString 'localhost:1521:xe' -dbaUserName sys -schemaUserName DEV_MDS You will be asked you passwords for sys and the schema Enter the database administrator password for "sys": Enter the schema password for schema user "DEV_MDS": Change directory to $MW_HOME/Oracle_SOA1/bin to where the Patch Set Assistant is installed for SOA Suite. Execute the following command to update the SOA and BAM schemas ./psa -dbType Oracle -dbConnectString 'localhost:1521:xe' -dbaUserName sys -schemaUserName DEV_SOAINFRA   To check that you have the installed correctly run the following SQL as sysdba. SELECT owner, version, status FROM schema_version_registry; OWNER                          VERSION                        STATUS ------------------------------ ------------------------------ ----------- DEV_MDS                        11.1.1.4.0                     VALID DEV_SOAINFRA                   11.1.1.4.0                     VALID Don’t stress if the versions are not all sitting at version 11.1.1.4 as not all schemas need to be updated. The key ones are MDS and SOAINFRA

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• Applied Security for Oracle Business Intelligence Podcast

  - by Tim Dexter

  Listen to BI Security Meister, Bryan Wise talk about his recent book Applied Oracle Security and learn about the cutting edge techniques for Oracle Business Intelligence from a leading security expert. http://www.oracle.com/podcasts/author-podcasts.html - Applied Security for Oracle Business Intelligence Well worth the listen and of course the book is available at all discerning bookstores!

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• What Is A Software Architect&rsquo;s Job Today?

  - by Tim Murphy

  Originally posted on: http://geekswithblogs.net/tmurphy/archive/2013/10/25/what-is-a-software-architectrsquos-job-today.aspx It was 2001 when a project manager first put my job title as architect on a statement of work.  A lot has changed over the last twelve years.  The concepts around what an architect is has evolved.  In the early days I would have said that they just rebranded the role of the system analyst.  Now we have a multitude of architect titles: application, solution, IT, data, enterprise.  Whatever the title the goals are the same.  An architect takes the business needs and maps them to the solutions that are needed and at the same time works to ensure the quality of the solution and its maintainability. One of the problems I see these days is that we are expecting every developer to have architect skills.  That in itself is not a problem.  This reduces the need for dedicated architects.  Not every developer though is going to be able to step up to this level.  Some are just good at solving small problems instead of thinking in the larger abstract. Another problem is the accelerating speed and breadth of new technologies and products.  For an architect to be good at his job he needs to spend large amounts of personal time studying just to stay relevant. In the end I don’t think the main objectives of an architect has changed, just the level of commitment needed to stay of value to your company.  Renew your commitment to your profession and keep delivering great solutions. Technorati Tags: software architect,enterprise architect,data architect,solution architect,IT architect,PSC,PSC Group

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• Record and Play your WebLogic Console Tasks Like a DVR

  - by james.bayer

  Automation using WebLogic Scripting Tool Today on the Oracle internal mailing list for WebLogic Server questions someone asked how to automate the configuration of the thread model for WebLogic Server and they were having trouble with the jython scripting syntax.  I’ve previously written about this feature called Work Managers and the associated constraints.  However, I did not show how to automate the process of configuring this without the console using WebLogic Scripting Tool – the jython scripting automation environment abbreviated as WLST.  I’ve written some very basic introductions to WLST before and there is also an Oracle By Example on the subject, but this is a bit more advanced.  Fear not because there is a really easy-to-use feature of the WLS console that lets you “Record” user actions just like a DVR.  Using these recordings of the web-based console, you can easily create a script even if you are unfamiliar with the WLST syntax and API.  I’m a big fan of both DVR’s and automation as can be evidenced with this old Halloween picture taken during simpler times.  Obviously the Cast Away and The Big Labowski references show some age.  I was a big Tivo fan-boy back in the day and I still think it’s the best DVR. I strongly believe that WebLogic Scripting Tool (WLST) is an absolutely essential tool for automating administration tasks in anything beyond a development environment.  Even in development environments you can make a case that it makes sense to start the automation for environments downstream.  I promise you that once you start using it for any tasks that you do even semi-regularly, you won’t go back to clicking through the console.  It’s simply so much more efficient and less error-prone to run a script. Let’s say you need to create a Work Manager and MaxThreadsConstraint – the easy way to do it is configure it in the WLS console first while capturing the commands with a recording.  See the images for the simple steps – click to enlarge. Record Console Configurations to a File Review the Recordings and Make Slight Modifications In order to make the recorded .py file directly callable as a stand-alone script I added calls to the connect() and edit() functions at the beginning and calls to disconnect() and exit() at the end – otherwise the main section of the script was provided by the console recording.  Below is the resulting file I saved as d:/temp/wm.py connect('weblogic','welcome1', 't3://localhost:7001') edit() startEdit()   cd('/SelfTuning/wl_server') cmo.createMaxThreadsConstraint('MaxThreadsConstraint-0')   cd('/SelfTuning/wl_server/MaxThreadsConstraints/MaxThreadsConstraint-0') set('Targets',jarray.array([ObjectName('com.bea:Name=examplesServer,Type=Server')], ObjectName)) cmo.setCount(5) cmo.unSet('ConnectionPoolName')   cd('/SelfTuning/wl_server') cmo.createWorkManager('WorkManager-0') cd('/SelfTuning/wl_server/WorkManagers/WorkManager-0') set('Targets',jarray.array([ObjectName('com.bea:Name=examplesServer,Type=Server')], ObjectName))   cmo.setMaxThreadsConstraint(getMBean('/SelfTuning/wl_server/MaxThreadsConstraints/MaxThreadsConstraint-0')) cmo.setIgnoreStuckThreads(false)   activate() disconnect() exit() Run the Script If you want to test it be sure to delete the Work Manager and MaxThreadConstraint that you had previously created in the console.  Do something like the following - set up the environment and tell WLST to execute the script which happens in the first 2 lines, the rest doesn’t require any user input: D:\Oracle\wls11g\wlserver_10.3\samples\domains\wl_server\bin>setDomainEnv.cmd D:\Oracle\wls11g\wlserver_10.3\samples\domains\wl_server>java weblogic.WLST d:\temp\wm.py   Initializing WebLogic Scripting Tool (WLST) ...   Welcome to WebLogic Server Administration Scripting Shell   Type help() for help on available commands   Connecting to t3://localhost:7001 with userid weblogic ... Successfully connected to Admin Server 'examplesServer' that belongs to domain 'wl_server'.   Warning: An insecure protocol was used to connect to the server. To ensure on-the-wire security, the SSL port or Admin port should be used instead.   Location changed to edit tree. This is a writable tree with DomainMBean as the root. To make changes you will need to start an edit session via startEdit().   For more help, use help(edit)   Starting an edit session ... Started edit session, please be sure to save and activate your changes once you are done. Activating all your changes, this may take a while ... The edit lock associated with this edit session is released once the activation is completed. Activation completed Disconnected from weblogic server: examplesServer     Exiting WebLogic Scripting Tool.   Now if you go back and look in the console the changes have been made and we now have a compete script.  Of course there is a full MBean reference and you can learn the nuances of jython and WLST, but why not the WLS console do most of the work for you!  Happy scripting.

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• Problem installing the latest eclipse IDE

  - by James

  I'm running ubuntu 11.04. I'm trying to install the latest "eclipse for java developers" IDE (version Indigo 3.7.1). I have downloaded and extracted it. I attempt to run it by changing to the extracted folder and executing ./eclipse This produces the following errors in the terminal: /usr/lib/gio/modules/libgiobamf.so: wrong ELF class: ELFCLASS64 Failed to load module: /usr/lib/gio/modules/libgiobamf.so /usr/lib/gio/modules/libgvfsdbus.so: wrong ELF class: ELFCLASS64 Failed to load module: /usr/lib/gio/modules/libgvfsdbus.so And then a dialog opens with this error message: JVM terminated. Exit code=13 /usr/bin/java -Dosgi.requiredJavaVersion=1.5 -XX:MaxPermSize=256m -Xms40m -Xmx384m -jar /opt/eclipse//plugins/org.eclipse.equinox.launcher_1.2.0.v20110502.jar -os linux -ws gtk -arch x86 -showsplash -launcher /opt/eclipse/eclipse -name Eclipse --launcher.library /opt/eclipse//plugins/org.eclipse.equinox.launcher.gtk.linux.x86_1.1.100.v20110505/eclipse_1407.so -startup /opt/eclipse//plugins/org.eclipse.equinox.launcher_1.2.0.v20110502.jar --launcher.overrideVmargs -exitdata 2f80031 -product org.eclipse.epp.package.java.product -clean -vm /usr/bin/java -vmargs -Dosgi.requiredJavaVersion=1.5 -XX:MaxPermSize=256m -Xms40m -Xmx384m -jar /opt/eclipse//plugins/org.eclipse.equinox.launcher_1.2.0.v20110502.jar I'd appreciate any help / insight. Update I should mention that I'm running 32 bit ubuntu and I'm trying to install 32 bit eclipse. Update #2 Oops - I just realized that I'm running 64 bit ubuntu, not 32 bit ubuntu.

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• C#: String Concatenation vs Format vs StringBuilder

  - by James Michael Hare

  I was looking through my groups’ C# coding standards the other day and there were a couple of legacy items in there that caught my eye.  They had been passed down from committee to committee so many times that no one even thought to second guess and try them for a long time.  It’s yet another example of how micro-optimizations can often get the best of us and cause us to write code that is not as maintainable as it could be for the sake of squeezing an extra ounce of performance out of our software. So the two standards in question were these, in paraphrase: Prefer StringBuilder or string.Format() to string concatenation. Prefer string.Equals() with case-insensitive option to string.ToUpper().Equals(). Now some of you may already know what my results are going to show, as these items have been compared before on many blogs, but I think it’s always worth repeating and trying these yourself.  So let’s dig in. The first test was a pretty standard one.  When concattenating strings, what is the best choice: StringBuilder, string concattenation, or string.Format()? So before we being I read in a number of iterations from the console and a length of each string to generate.  Then I generate that many random strings of the given length and an array to hold the results.  Why am I so keen to keep the results?  Because I want to be able to snapshot the memory and don’t want garbage collection to collect the strings, hence the array to keep hold of them.  I also didn’t want the random strings to be part of the allocation, so I pre-allocate them and the array up front before the snapshot.  So in the code snippets below: num – Number of iterations. strings – Array of randomly generated strings. results – Array to hold the results of the concatenation tests. timer – A System.Diagnostics.Stopwatch() instance to time code execution. start – Beginning memory size. stop – Ending memory size. after – Memory size after final GC. So first, let’s look at the concatenation loop: 1: // build num strings using concattenation. 2: for (int i = 0; i < num; i++) 3: { 4: results[i] = "This is test #" + i + " with a result of " + strings[i]; 5: } Pretty standard, right?  Next for string.Format(): 1: // build strings using string.Format() 2: for (int i = 0; i < num; i++) 3: { 4: results[i] = string.Format("This is test #{0} with a result of {1}", i, strings[i]); 5: }   Finally, StringBuilder: 1: // build strings using StringBuilder 2: for (int i = 0; i < num; i++) 3: { 4: var builder = new StringBuilder(); 5: builder.Append("This is test #"); 6: builder.Append(i); 7: builder.Append(" with a result of "); 8: builder.Append(strings[i]); 9: results[i] = builder.ToString(); 10: } So I take each of these loops, and time them by using a block like this: 1: // get the total amount of memory used, true tells it to run GC first. 2: start = System.GC.GetTotalMemory(true); 3:  4: // restart the timer 5: timer.Reset(); 6: timer.Start(); 7:  8: // *** code to time and measure goes here. *** 9:  10: // get the current amount of memory, stop the timer, then get memory after GC. 11: stop = System.GC.GetTotalMemory(false); 12: timer.Stop(); 13: other = System.GC.GetTotalMemory(true); So let’s look at what happens when I run each of these blocks through the timer and memory check at 500,000 iterations: 1: Operator + - Time: 547, Memory: 56104540/55595960 - 500000 2: string.Format() - Time: 749, Memory: 57295812/55595960 - 500000 3: StringBuilder - Time: 608, Memory: 55312888/55595960 – 500000   Egad!  string.Format brings up the rear and + triumphs, well, at least in terms of speed.  The concat burns more memory than StringBuilder but less than string.Format().  This shows two main things: StringBuilder is not always the panacea many think it is. The difference between any of the three is miniscule! The second point is extremely important!  You will often here people who will grasp at results and say, “look, operator + is 10% faster than StringBuilder so always use StringBuilder.”  Statements like this are a disservice and often misleading.  For example, if I had a good guess at what the size of the string would be, I could have preallocated my StringBuffer like so:   1: for (int i = 0; i < num; i++) 2: { 3: // pre-declare StringBuilder to have 100 char buffer. 4: var builder = new StringBuilder(100); 5: builder.Append("This is test #"); 6: builder.Append(i); 7: builder.Append(" with a result of "); 8: builder.Append(strings[i]); 9: results[i] = builder.ToString(); 10: }   Now let’s look at the times: 1: Operator + - Time: 551, Memory: 56104412/55595960 - 500000 2: string.Format() - Time: 753, Memory: 57296484/55595960 - 500000 3: StringBuilder - Time: 525, Memory: 59779156/55595960 - 500000   Whoa!  All of the sudden StringBuilder is back on top again!  But notice, it takes more memory now.  This makes perfect sense if you examine the IL behind the scenes.  Whenever you do a string concat (+) in your code, it examines the lengths of the arguments and creates a StringBuilder behind the scenes of the appropriate size for you. But even IF we know the approximate size of our StringBuilder, look how much less readable it is!  That’s why I feel you should always take into account both readability and performance.  After all, consider all these timings are over 500,000 iterations.   That’s at best  0.0004 ms difference per call which is neglidgable at best.  The key is to pick the best tool for the job.  What do I mean?  Consider these awesome words of wisdom: Concatenate (+) is best at concatenating.  StringBuilder is best when you need to building. Format is best at formatting. Totally Earth-shattering, right!  But if you consider it carefully, it actually has a lot of beauty in it’s simplicity.  Remember, there is no magic bullet.  If one of these always beat the others we’d only have one and not three choices. The fact is, the concattenation operator (+) has been optimized for speed and looks the cleanest for joining together a known set of strings in the simplest manner possible. StringBuilder, on the other hand, excels when you need to build a string of inderterminant length.  Use it in those times when you are looping till you hit a stop condition and building a result and it won’t steer you wrong. String.Format seems to be the looser from the stats, but consider which of these is more readable.  Yes, ignore the fact that you could do this with ToString() on a DateTime.  1: // build a date via concatenation 2: var date1 = (month < 10 ? string.Empty : "0") + month + '/' 3: + (day < 10 ? string.Empty : "0") + '/' + year; 4:  5: // build a date via string builder 6: var builder = new StringBuilder(10); 7: if (month < 10) builder.Append('0'); 8: builder.Append(month); 9: builder.Append('/'); 10: if (day < 10) builder.Append('0'); 11: builder.Append(day); 12: builder.Append('/'); 13: builder.Append(year); 14: var date2 = builder.ToString(); 15:  16: // build a date via string.Format 17: var date3 = string.Format("{0:00}/{1:00}/{2:0000}", month, day, year); 18:  So the strength in string.Format is that it makes constructing a formatted string easy to read.  Yes, it’s slower, but look at how much more elegant it is to do zero-padding and anything else string.Format does. So my lesson is, don’t look for the silver bullet!  Choose the best tool.  Micro-optimization almost always bites you in the end because you’re sacrificing readability for performance, which is almost exactly the wrong choice 90% of the time. I love the rules of optimization.  They’ve been stated before in many forms, but here’s how I always remember them: For Beginners: Do not optimize. For Experts: Do not optimize yet. It’s so true.  Most of the time on today’s modern hardware, a micro-second optimization at the sake of readability will net you nothing because it won’t be your bottleneck.  Code for readability, choose the best tool for the job which will usually be the most readable and maintainable as well.  Then, and only then, if you need that extra performance boost after profiling your code and exhausting all other options… then you can start to think about optimizing.

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• Excel Template Teaser

  - by Tim Dexter

  In lieu of some official documentation I'm in the process of putting together some posts on the new 10.1.3.4.1 Excel templates. No more HTML, maskerading as Excel; far more flexibility than Excel Analyzer and no need to write complex XSL templates to create the same output. Multi sheet outputs with macros and embeddable XSL commands are here. Their capabilities are pretty extensive and I have not worked on them for a few years since I helped put them together for EBS FSG users, so Im back on the learning curve. Let me say up front, there is no template builder, its a completely manual process to build them but, the results can be fantastic and provide yet another 'superstar' opportunity for you. The templates can take hierarchical XML data and walk the structure much like an RTF template. They use named cells/ranges and a hidden sheet to provide the rendering engine the hooks to drop the data in. As a taster heres the data and output I worked with on my first effort: <EMPLOYEES> <LIST_G_DEPT> <G_DEPT> <DEPARTMENT_ID>10</DEPARTMENT_ID> <DEPARTMENT_NAME>Administration</DEPARTMENT_NAME> <LIST_G_EMP> <G_EMP> <EMPLOYEE_ID>200</EMPLOYEE_ID> <EMP_NAME>Jennifer Whalen</EMP_NAME> <EMAIL>JWHALEN</EMAIL> <PHONE_NUMBER>515.123.4444</PHONE_NUMBER> <HIRE_DATE>1987-09-17T00:00:00.000-06:00</HIRE_DATE> <SALARY>4400</SALARY> </G_EMP> </LIST_G_EMP> <TOTAL_EMPS>1</TOTAL_EMPS> <TOTAL_SALARY>4400</TOTAL_SALARY> <AVG_SALARY>4400</AVG_SALARY> <MAX_SALARY>4400</MAX_SALARY> <MIN_SALARY>4400</MIN_SALARY> </G_DEPT> ... </LIST_G_DEPT> </EMPLOYEES> Structured XML coming from a data template, check out the data template progression post. I can then generate the following binary XLS file. There are few cool things to notice in this output. DEPARTMENT-EMPLOYEE master detail output. Not easy to do in the Excel analyzer. Date formatting - this is using an Excel function. Remember BIP generates XML dates in the canonical format. I have formatted the other data in the template using native Excel functionality Salary Total - although in the data I have calculated this in the template Conditional formatting - this is handled by Excel based on the incoming data Bursting department data across sheets and using the department name for the sheet name. This alone is worth the wait! there's more, but this is surely enough to whet your appetite. These new templates are already tucked away in EBS R12 under controlled release by the GL team and have now come to the BIEE and standalone releases in the 10.1.3.4.1+ rollup patch. For the rest of you, its going to be a bit of a waiting game for the relevant teams to uptake the latest BIP release. Look out for more soon with some explanation of how they work and how to put them together!

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• How to prepare for an interview presentation!

  - by Tim Koekkoek

  During an interview process you might be asked to prepare a presentation as one of the steps in the recruitment process. Below, we want to give you some tips to help you prepare for what might be considered a daunting aspect of a recruitment process. Main purpose of the presentation Always keep in mind the main purpose of what the presentation is meant to convey. Generally speaking, an interview presentation is for the company to check if you have the ability to represent and sell the organization (and yourself), to the internal and external stakeholders in the position you are applying for. A presentation is often also part of the recruitment process to check whether you can structure and explain your experience and thoughts in a convincing manner. If you are unsure about the purpose of the presentation, feel free to ask your recruiter for more information. Preparation As with every task you do, preparation is key, so is the case with an interview presentation. It is important to know who your audience is. You have to adapt your presentation to your audience, ensuring that you are presenting the facts which they would want to hear. Furthermore, make sure you practice your presentation beforehand; this will make you more confident in your presenting skills. Also, estimate the length of your presentation as presentations or pitches during the recruitment process are often capped to a certain time limit. Structure Every presentation should have a beginning, middle and an end. Make sure you give an overview of your presentation and tell the audience what they can expect. Your presentation should have a logical order and a clear message. Always build up to your key message with strong arguments and evidence. When speaking about the topic, make sure you convey your points with conviction. Also be sure you believe the message you bring forward, if you don’t believe it yourself, then the audience definitely won’t! Delivery When you think back on successful presentations you have seen, the presenter was most likely always standing up. So if asked to do a presentation, follow this example and make sure you stand up as well. Standing up when you are doing your presentation shows confidence and control. Another important aspect in the delivery of the presentation is to relax and speak slowly and with enough volume for the audience to hear you. Speaking slowly allows the audience the time to absorb the information you are providing to them. Visual Using PowerPoint, or an equivalent, makes it very easy to have a visually attractive presentation. Make sure however that you take into account that the visual aids you use are there to support you, not for you to read word for word what is on the slides! Questions When starting your presentation, it is a good idea to tell your audience that you will deal with any questions they might have at the end of the presentation. This way it doesn’t interrupt your train of thought and the flow of your presentation. Answering questions at the end may give you additional opportunities to further expand on your facts in the topic. Some people might play the “devil’s advocate” role and confront you with opposing opinions, if this is the case, take your time to reiterate your points and remain professional in your response. A good way to deal with this is to start interacting with other members of the audience and ask for their opinions, so it will become a group discussion. This will also shows strong leadership skills, as you are open to discuss and ask for other opinions. If you are interested in more tips and tricks for your interview process, have a look at Competency Based Interview Tips and How to prepare for a Telephone Interview. For more information about Oracle and our vacancies, please visit our Facebook community and our careers website.

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• C#/.NET Little Wonders: Of LINQ and Lambdas - A Presentation

  - by James Michael Hare

  Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. Today I’m giving a brief beginner’s guide to LINQ and Lambdas at the St. Louis .NET User’s Group so I thought I’d post the presentation here as well.  I updated the presentation a bit as well as added some notes on the query syntax.  Enjoy! The C#/.NET Fundaments: Of Lambdas and LINQ Presentation Of Lambdas and LINQ View more presentations from BlackRabbitCoder   Technorati Tags: C#, CSharp, .NET, Little Wonders, LINQ, Lambdas

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• Kernel compile error with iw_ndis.c

  - by James

  Hi, I have a hp pavilion dm3t with intel HD graphics running ubuntu 10.10 64 bit. I'm trying to compile and install a patched kernel according to this, https://launchpad.net/~kamalmostafa/+archive/linux-kamal-mjgbacklight So I downloaded the tarball from here (linked to from the page above): http://kernel.ubuntu.com/git?p=kamal/ubuntu-maverick.git;a=shortlog;h=refs/heads/mjg-backlight I untar'd it to a directory, entered the directory and did: make defconfig I'm not sure if that's what I should have done but it was successful, so I did: make which seemed to work fine until it gave these errors: ubuntu/ndiswrapper/iw_ndis.c:1966: error: unknown field ‘num_private’ specified in initializer ubuntu/ndiswrapper/iw_ndis.c:1966: warning: initialization makes pointer from integer without a cast ubuntu/ndiswrapper/iw_ndis.c:1967: error: unknown field ‘num_private_args’ specified in initializer ubuntu/ndiswrapper/iw_ndis.c:1967: warning: excess elements in struct initializer ubuntu/ndiswrapper/iw_ndis.c:1967: warning: (near initialization for ‘ndis_handler_def’) ubuntu/ndiswrapper/iw_ndis.c:1970: error: unknown field ‘private’ specified in initializer ubuntu/ndiswrapper/iw_ndis.c:1970: warning: initialization makes integer from pointer without a cast ubuntu/ndiswrapper/iw_ndis.c:1970: error: initializer element is not computable at load time ubuntu/ndiswrapper/iw_ndis.c:1970: error: (near initialization for ‘ndis_handler_def.num_standard’) ubuntu/ndiswrapper/iw_ndis.c:1971: error: unknown field ‘private_args’ specified in initializer ubuntu/ndiswrapper/iw_ndis.c:1971: warning: initialization from incompatible pointer type make[2]: *** [ubuntu/ndiswrapper/iw_ndis.o] Error 1 make[1]: *** [ubuntu/ndiswrapper] Error 2 make: *** [ubuntu] Error 2 How can I compile and install this kernel successfully? I'm new to this and would appreciate any help.

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• Chicago Code Camp Call For Speakers

  - by Tim Murphy

  The Chicago Code Camp is coming up on May 1st, 2010.  They are still looking for speaker.  If you have a rock’n code demonstration that you would like to present to the community be sure to sign up.  If you know someone else who has some ideas that you really think they should share with the world guilt them in to signing up.  http://www.chicagocodecamp.com/ del.icio.us Tags: Chicago Code Camp,call for speakers

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• C#/.NET Little Wonders: The EventHandler and EventHandler&lt;TEventArgs&gt; delegates

  - by James Michael Hare

  Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. In the last two weeks, we examined the Action family of delegates (and delegates in general), and the Func family of delegates and how they can be used to support generic, reusable algorithms and classes. So this week, we are going to look at a handy pair of delegates that can be used to eliminate the need for defining custom delegates when creating events: the EventHandler and EventHandler<TEventArgs> delegates. Events and delegates Before we begin, let’s quickly consider events in .NET.  According to the MSDN: An event in C# is a way for a class to provide notifications to clients of that class when some interesting thing happens to an object. So, basically, you can create an event in a type so that users of that type can subscribe to notifications of things of interest.  How is this different than some of the delegate programming that we talked about in the last two weeks?  Well, you can think of an event as a special access modifier on a delegate.  Some differences between the two are: Events are a special access case of delegates They behave much like delegates instances inside the type they are declared in, but outside of that type they can only be (un)subscribed to. Events can specify add/remove behavior explicitly If you want to do additional work when someone subscribes or unsubscribes to an event, you can specify the add and remove actions explicitly. Events have access modifiers, but these only specify the access level of those who can (un)subscribe A public event, for example, means anyone can (un)subscribe, but it does not mean that anyone can raise (invoke) the event directly.  Events can only be raised by the type that contains them In contrast, if a delegate is visible, it can be invoked outside of the object (not even in a sub-class!). Events tend to be for notifications only, and should be treated as optional Semantically speaking, events typically don’t perform work on the the class directly, but tend to just notify subscribers when something of note occurs. My basic rule-of-thumb is that if you are just wanting to notify any listeners (who may or may not care) that something has happened, use an event.  However, if you want the caller to provide some function to perform to direct the class about how it should perform work, make it a delegate. Declaring events using custom delegates To declare an event in a type, we simply use the event keyword and specify its delegate type.  For example, let’s say you wanted to create a new TimeOfDayTimer that triggers at a given time of the day (as opposed to on an interval).  We could write something like this: 1: public delegate void TimeOfDayHandler(object source, ElapsedEventArgs e); 2:  3: // A timer that will fire at time of day each day. 4: public class TimeOfDayTimer : IDisposable 5: { 6: // Event that is triggered at time of day. 7: public event TimeOfDayHandler Elapsed; 8:  9: // ... 10: } The first thing to note is that the event is a delegate type, which tells us what types of methods may subscribe to it.  The second thing to note is the signature of the event handler delegate, according to the MSDN: The standard signature of an event handler delegate defines a method that does not return a value, whose first parameter is of type Object and refers to the instance that raises the event, and whose second parameter is derived from type EventArgs and holds the event data. If the event does not generate event data, the second parameter is simply an instance of EventArgs. Otherwise, the second parameter is a custom type derived from EventArgs and supplies any fields or properties needed to hold the event data. So, in a nutshell, the event handler delegates should return void and take two parameters: An object reference to the object that raised the event. An EventArgs (or a subclass of EventArgs) reference to event specific information. Even if your event has no additional information to provide, you are still expected to provide an EventArgs instance.  In this case, feel free to pass the EventArgs.Empty singleton instead of creating new instances of EventArgs (to avoid generating unneeded memory garbage). The EventHandler delegate Because many events have no additional information to pass, and thus do not require custom EventArgs, the signature of the delegates for subscribing to these events is typically: 1: // always takes an object and an EventArgs reference 2: public delegate void EventHandler(object sender, EventArgs e) It would be insane to recreate this delegate for every class that had a basic event with no additional event data, so there already exists a delegate for you called EventHandler that has this very definition!  Feel free to use it to define any events which supply no additional event information: 1: public class Cache 2: { 3: // event that is raised whenever the cache performs a cleanup 4: public event EventHandler OnCleanup; 5:  6: // ... 7: } This will handle any event with the standard EventArgs (no additional information).  But what of events that do need to supply additional information?  Does that mean we’re out of luck for subclasses of EventArgs?  That’s where the generic for of EventHandler comes into play… The generic EventHandler<TEventArgs> delegate Starting with the introduction of generics in .NET 2.0, we have a generic delegate called EventHandler<TEventArgs>.  Its signature is as follows: 1: public delegate void EventHandler<TEventArgs>(object sender, TEventArgs e) 2: where TEventArgs : EventArgs This is similar to EventHandler except it has been made generic to support the more general case.  Thus, it will work for any delegate where the first argument is an object (the sender) and the second argument is a class derived from EventArgs (the event data). For example, let’s say we wanted to create a message receiver, and we wanted it to have a few events such as OnConnected that will tell us when a connection is established (probably with no additional information) and OnMessageReceived that will tell us when a new message arrives (probably with a string for the new message text). So for OnMessageReceived, our MessageReceivedEventArgs might look like this: 1: public sealed class MessageReceivedEventArgs : EventArgs 2: { 3: public string Message { get; set; } 4: } And since OnConnected needs no event argument type defined, our class might look something like this: 1: public class MessageReceiver 2: { 3: // event that is called when the receiver connects with sender 4: public event EventHandler OnConnected; 5:  6: // event that is called when a new message is received. 7: public event EventHandler<MessageReceivedEventArgs> OnMessageReceived; 8:  9: // ... 10: } Notice, nowhere did we have to define a delegate to fit our event definition, the EventHandler and generic EventHandler<TEventArgs> delegates fit almost anything we’d need to do with events. Sidebar: Thread-safety and raising an event When the time comes to raise an event, we should always check to make sure there are subscribers, and then only raise the event if anyone is subscribed.  This is important because if no one is subscribed to the event, then the instance will be null and we will get a NullReferenceException if we attempt to raise the event. 1: // This protects against NullReferenceException... or does it? 2: if (OnMessageReceived != null) 3: { 4: OnMessageReceived(this, new MessageReceivedEventArgs(aMessage)); 5: } The above code seems to handle the null reference if no one is subscribed, but there’s a problem if this is being used in multi-threaded environments.  For example, assume we have thread A which is about to raise the event, and it checks and clears the null check and is about to raise the event.  However, before it can do that thread B unsubscribes to the event, which sets the delegate to null.  Now, when thread A attempts to raise the event, this causes the NullReferenceException that we were hoping to avoid! To counter this, the simplest best-practice method is to copy the event (just a multicast delegate) to a temporary local variable just before we raise it.  Since we are inside the class where this event is being raised, we can copy it to a local variable like this, and it will protect us from multi-threading since multicast delegates are immutable and assignments are atomic: 1: // always make copy of the event multi-cast delegate before checking 2: // for null to avoid race-condition between the null-check and raising it. 3: var handler = OnMessageReceived; 4: 5: if (handler != null) 6: { 7: handler(this, new MessageReceivedEventArgs(aMessage)); 8: } The very slight trade-off is that it’s possible a class may get an event after it unsubscribes in a multi-threaded environment, but this is a small risk and classes should be prepared for this possibility anyway.  For a more detailed discussion on this, check out this excellent Eric Lippert blog post on Events and Races. Summary Generic delegates give us a lot of power to make generic algorithms and classes, and the EventHandler delegate family gives us the flexibility to create events easily, without needing to redefine delegates over and over.  Use them whenever you need to define events with or without specialized EventArgs.   Tweet Technorati Tags: .NET, C#, CSharp, Little Wonders, Generics, Delegates, EventHandler

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• Book Review: Getting Started With Window 8 Apps By Ben Dewey

  - by Tim Murphy

  When O’Reilly gave me an opportunity to review this book I was excited.  It gave me a reason to finally put some time into this new platform and what developers will need to learn in order to be successful. This book by Ben Dewey is only 92 pages long, so if you were looking for an in-depth treatment of Windows 8 development you will need supplemental materials.  It is also due for an update from the perspective of recent changes made by Microsoft prior to the final release of the OS and tools.  This causes a few issues if you try to run the code samples because of namespace changes. I was encouraged by the fact that the author didn’t do the typical “hello world” app.  He uses a lot of pattern based development techniques and hits many of the main topics including: Application lifecycle Charms integration Tiles Sensors The lifecycle is critical for anyone who hasn’t done mobile development before.  Limited resources on these devices mean that the OS can suspend or kill your app altogether if it decides it needs to.  He covers tombstoning which is the key to Windows 8 and Windows Phone lifecycle management. He also dedicates a chapter to marketing and distributing the application you build.  From my experience with Windows Phone development this is crucial information.  You need to know how to test your application so that it is going to pass certification and present your app so that it is going to get noticed amongst thousands of other apps. The main things that I wish had been in the book explanations of more of the common controls and more complete explanation of patterns that were implemented. In the end this book is a good foundation getting exposure to the concepts that underlie this new version of the Windows platform and how it effects developers.  It isn’t a book that I would suggest for someone just getting into development with no understanding of pattern based development. del.icio.us Tags: Windows 8,O'Reilly,Ben Dewey,Book Review,Review

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• Shader effect similar to Metro 2033 gasmask

  - by Tim

  I was thinking about effects in games the other day and I was reminded of the Gasmask effect from Metro 2033. Once you put the gasmask on it blurred a bit in the corners and could ice up and even get cracked. I assume that something like that is done using a shader. I have been experimenting a bit with game development, so far mostly playing with existing rendering engines and adding physics support etc. I would like to learn more about this sort of effect. Can someone give me a simple example of a shader that would alter the entire scene like this. Or if not a shader then an idea on how it would be done. Thanks. Edit : Include screenshot of the metro 2033 gasmask effect.

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• Get the onended event for an AudioBuffer in HTML5/Chrome

  - by Matthew James Davis

  So I am playing audio file in Chrome and I want to detect when playing has ended so I can delete references to it. Here is my code var source = context.createBufferSource(); source.buffer = sound.buffer; source.loop = sound.loop; source.onended = function() { delete playingSounds[soundName]; } source.connect(mainNode); source.start(0, sound.start, sound.length); however, the event handler doesn't fire. Is this not yet supported as described by the W3 specification? Or am I doing something wrong?

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• Survey: Do you write custom SQL CLR procedures/functions/etc

  - by James Luetkehoelter

  I'm quite curious because despite the great capabilities of writing CLR-based stored procedures to off-load those nasty operations TSQL isn't that great at (like iteration, or complex math), I'm continuing to see a wealth of SQL 2008 databases with complex stored procedures and functions which would make great candidates. The in-house skill to create the CLR code exists as well, but there is flat out resistance to use it. In one scenario I was told "Oh, iteration isn't a problem because we've trained...(read more)

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• C#/.NET Little Wonders: A Redux

  - by James Michael Hare

  I gave my Little Wonders presentation to the Topeka Dot Net Users' Group today, so re-posting the links to all the previous posts for them. The Presentation: C#/.NET Little Wonders: A Presentation The Original Trilogy: C#/.NET Five Little Wonders (part 1) C#/.NET Five More Little Wonders (part 2) C#/.NET Five Final Little Wonders (part 3) The Subsequent Sequels: C#/.NET Little Wonders: ToDictionary() and ToList() C#/.NET Little Wonders: DateTime is Packed With Goodies C#/.NET Little Wonders: Fun With Enum Methods C#/.NET Little Wonders: Cross-Calling Constructors C#/.NET Little Wonders: Constraining Generics With Where Clause C#/.NET Little Wonders: Comparer<T>.Default C#/.NET Little Wonders: The Useful (But Overlooked) Sets The Concurrent Wonders: C#/.NET Little Wonders: The Concurrent Collections (1 of 3) - ConcurrentQueue and ConcurrentStack C#/.NET Little Wonders: The Concurrent Collections (2 of 3) - ConcurrentDictionary Tweet   Technorati Tags: .NET,C#,Little Wonders

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• Dynamic Data Connections

  - by Tim Dexter

  I have had a long running email thread running between Dan and David over at Valspar and myself. They have built some impressive connectivity between their in house apps and BIP using web services. The crux of their problem has been that they have multiple databases that need the same report executed against them. Not such an unusual request as I have spoken to two customers in the last month with the same situation. Of course, you could create a report against each data connection and just run or call the appropriate report. Not too bad if you have two or three data connections but more than that and it becomes a maintenance nightmare having to update queries or layouts. Ideally you want to have just a single report definition on the BIP server and to dynamically set the connection to be used at runtime based on the user or system that the user is in. A quick bit of digging and help from Shinji on the development team and I had an answer. Rather embarassingly, the solution has been around since the Oct 2010 rollup patch last year. Still, I grabbed the latest Jan 2011 patch - check out Note 797057.1 for the latest available patches. Once installed, I used the best web service testing tool I have yet to come across - SoapUI. Just point it at the WSDL and you can check out the available services and their parameters and then test them too. The XML packet has a new dynamic data source entry. You can set you own custom JDBC connection or just specify an existing data source name thats defined on the server. <pub:runReport> <pub:reportRequest> <pub:attributeFormat>xml</pub:attributeFormat> <pub:attributeTemplate>0</pub:attributeTemplate> <pub:byPassCache>true</pub:byPassCache> <pub:dynamicDataSource> <pub:JDBCDataSource> <pub:JDBCDriverClass></pub:JDBCDriverClass> <pub:JDBCDriverType></pub:JDBCDriverType> <pub:JDBCPassword></pub:JDBCPassword> <pub:JDBCURL></pub:JDBCURL> <pub:JDBCUserName></pub:JDBCUserName> <pub:dataSourceName>Conn1</pub:dataSourceName> </pub:JDBCDataSource> </pub:dynamicDataSource> <pub:reportAbsolutePath>/Test/Employee Report/Employee Report.xdo</pub:reportAbsolutePath> </pub:reportRequest> <pub:userID>Administrator</pub:userID> <pub:password>Administrator</pub:password> </pub:runReport> So I have Conn1 and Conn2 defined that are connections to different databases. I can just flip the name, make the WS call and get the appropriate dataset in my report. Just as an example, here's my web service call java code. Just a case of bringing in the BIP java libs to my java project. publicReportServiceService = new PublicReportServiceService(); PublicReportService publicReportService = publicReportServiceService.getPublicReportService_v11(); String userID = "Administrator"; String password = "Administrator"; ReportRequest rr = new ReportRequest(); rr.setAttributeFormat("xml"); rr.setAttributeTemplate("1"); rr.setByPassCache(true); rr.setReportAbsolutePath("/Test/Employee Report/Employee Report.xdo"); rr.setReportOutputPath("c:\\temp\\output.xml"); BIPDataSource bipds = new BIPDataSource(); JDBCDataSource jds = new JDBCDataSource(); jds.setDataSourceName("Conn1"); bipds.setJDBCDataSource(jds); rr.setDynamicDataSource(bipds); try { publicReportService.runReport(rr, userID, password); } catch (InvalidParametersException e) { e.printStackTrace(); } catch (AccessDeniedException e) { e.printStackTrace(); } catch (OperationFailedException e) { e.printStackTrace(); } } Note, Im no java whiz kid or whizzy old bloke, at least not unless Ive had a coffee. JDeveloper has a nice feature where you point it at the WSDL and it creates everything to support your calling code for you. Couple of things to remember: 1. When you call the service, remember to set the bypass the cache option. Forget it and much scratching of your head and taking my name in vain will ensue. 2. My demo actually hit the same database but used two users, one accessed the base tables another views with the same name. For far too long I thought the connection swapping was not working. I was getting the same results for both users until I realized I was specifying the schema name for the table/view in my query e.g. select * from EMP.EMPLOYEES. So remember to have a generic query that will depend entirely on the connection. Its a neat feature if you want to be able to switch connections and only define a single report and call it remotely. Now if you want the connection to be set dynamically based on the user and the report run via the user interface, thats going to be more tricky ... need to think about that one!

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• BIP Debugging to a file

  - by Tim Dexter

  If you use the standalone server or with OBIEE and use OC4J as the web server. Have you ever taken a looksee at the console window (doc/xterm) that you use to start it. Ever turned on debugging to see masses of info flow by that window and want to capture it all? I have been debugging today and watched all that info fly by and on Windoze gets lost before you can see it! The BIP developers use the System.out.println() and System.err.println()methods in the BIP applications to generate debugging formation. Normally the output from these method calls go to the console where the OC4J process is started. However you can specify command line options when starting OC4J to direct the stdout and stderr output directly to files. The ?out and ?err parameters tell OC4J which file to direct the output to. All you need do is modify the oc4j.cmd file used to start BIP. I didnt get fancy and just plugged in the following to the file under the start section. I just modified the line: set CMDARGS=-config "%SERVER_XML%" -userThreads to set CMDARGS=-config "%SERVER_XML%" -out D:\BI\OracleBI\oc4j_bi\j2ee\home\log\oc4j.out -err D:\BI\OracleBI\oc4j_bi\j2ee\home\log\oc4j.err -userThreads Bounced the server and I now have a ballooning pair of debug files that I can pour over to my hearts content. The .out file appears to contain BIP only log info and the .err file, OBIEE messages. If you are using another web server to host BIP, just check out the user docs to find out how to get the log files to write. Note to self, remember to turn off the debug when Im done!

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• Review: ComponentOne Studio for Entity Framework

  - by Tim Murphy

  While I have always been a fan of libraries that improve coding efficiency and reduce code redundancy I have mostly been using ones that were in the public domain.  As part of the Geeks With Blogs Influencers program a got my hands on ComponentOne’s Studio for Entity Framework.  Below are my thought after working with the product for several weeks. My coding preference has always been maintainable code that is reusable across an enterprises protfolio.  Because of this my focus in reviewing this product is less on the RAD components and more on its benefits for layered applications using code first Entity Framework. Before we get into the pros and cons here is a summary of the main feature listed for SEF. Unified Data Context Virtual Data Access More Powerful Data Binding Pros The first thing that I found to my liking is the C1DataSource. It basically manages a cache for your Entity Model context.  Under RAD conditions this is setup automatically when you drop the object on a your design surface.  If you are like me and want to abstract you data management into a library it takes a little more work, but it is still acceptable and gains the same benefits. The second feature that I found beneficial is the definition of views with improved sorting and filtering.  Again the ease of use of these features is greater on the RAD side but no capabilities are missing when manipulating object in code. Linq has become my friend over the last couple of years and it was great to see that ComponentOne had ensured that it remained a first class citizen in their design.  When you look into this product yourself I would suggest taking a dive into LiveLinq which allow the joining of different data source types. As I went through discovering the features of this framework I appreciated the number of examples that they supplied for different uses.  Besides showing how to use SEF with WinForms, WPF and Silverlight they also showed how to accomplish tasks both RAD, code only and MVVM approaches. Cons The only area that I would really like to see improvement is in there level of detail in their documentation.  Specifically I would like to have seen some of the supporting code explained, such as what some supporting object did, in the examples instead of having to go to the programmer’s reference. I did find some times where currently existing projects had some trouble determining scope that the RAD controls were allowed, but I expect this is something that is in part end user related. Summary Overall I found the Studio for Entity Framework capable and well thought out.  If you are already using the Entity Framework this product will fit into your environment with little effort in return for greater flexibility and greater robustness in your solutions. Whether the $895 list price for a standard version works for you will depend on your return on investment. Smaller companies with only a small number of projects may not be able to stomach it, you get a full featured product that is supported by a well established company.  The more projects and the more code you have the greater your return on investment will be. Personally I intend to apply this product to some production systems and will probably have some tips and tricks in the future. del.icio.us Tags: ComponentOne,Studio for Entity Framework,Geeks With Blogs,Influencers,Product Reviews

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• MDX using EXISTING, AGGREGATE, CROSSJOIN and WHERE

  - by James Rogers

  It is a well-published approach to using the EXISTING function to decode AGGREGATE members and nested sub-query filters.  Mosha wrote a good blog on it here and a more recent one here.  The use of EXISTING in these scenarios is very useful and sometimes the only option when dealing with multi-select filters.  However, there are some limitations I have run across when using the EXISTING function against an AGGREGATE member:   The AGGREGATE member must be assigned to the Dimension.Hierarchy being detected by the EXISTING function in the calculated measure. The AGGREGATE member cannot contain a crossjoin from any other dimension or hierarchy or EXISTING will not be able to detect the members in the AGGREGATE member.   Take the following query (from Adventure Works DW 2008):   With   member [Week Count] as 'count(existing([Date].[Fiscal Weeks].[Fiscal Week].members))'    member [Date].[Fiscal Weeks].[CM] as 'AGGREGATE({[Date].[Fiscal Weeks].[Fiscal Week].&[47]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[48]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[49]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[50]&[2004]})'   select   {[Week Count]} on columns from   [Adventure Works]     where   [Date].[Fiscal Weeks].[CM]   Here we are attempting to count the existing fiscal weeks in slicer.  This is useful to get a per-week average for another member. Many applications generate queries in this manner (such as Oracle OBIEE).  This query returns the correct result of (4) weeks. Now let's put a twist in it.  What if the querying application submits the query in the following manner:   With   member [Week Count] as 'count(existing([Date].[Fiscal Weeks].[Fiscal Week].members))'    member [Customer].[Customer Geography].[CM] as 'AGGREGATE({[Date].[Fiscal Weeks].[Fiscal Week].&[47]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[48]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[49]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[50]&[2004]})'   select   {[Week Count]} on columns from   [Adventure Works]     where   [Customer].[Customer Geography].[CM]   Here we are attempting to count the existing fiscal weeks in slicer.  However, the AGGREGATE member is built on a different dimension (in name) than the one EXISTING is trying to detect.  In this case the query returns (174) which is the total number of [Date].[Fiscal Weeks].[Fiscal Week].members defined in the dimension.   Now another twist, the AGGREGATE member will be named appropriately and contain the hierarchy we are trying to detect with EXISTING but it will be cross-joined with another hierarchy:   With   member [Week Count] as 'count(existing([Date].[Fiscal Weeks].[Fiscal Week].members))'    member [Date].[Fiscal Weeks].[CM] as 'AGGREGATE({[Date].[Fiscal Weeks].[Fiscal Week].&[47]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[48]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[49]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[50]&[2004]}*    {[Customer].[Customer Geography].[Country].&[Australia],[Customer].[Customer Geography].[Country].&[United States]})'  select   {[Week Count]} on columns from   [Adventure Works]    where   [Date].[Fiscal Weeks].[CM]   Once again, we are attempting to count the existing fiscal weeks in slicer.  Again, in this case the query returns (174) which is the total number of [Date].[Fiscal Weeks].[Fiscal Week].members defined in the dimension. However, in 2008 R2 this query returns the correct result of 4 and additionally , the following will return the count of existing countries as well (2):   With   member [Week Count] as 'count(existing([Date].[Fiscal Weeks].[Fiscal Week].members))'   member [Country Count] as 'count(existing([Customer].[Customer Geography].[Country].members))'  member [Date].[Fiscal Weeks].[CM] as 'AGGREGATE({[Date].[Fiscal Weeks].[Fiscal Week].&[47]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[48]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[49]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[50]&[2004]}*    {[Customer].[Customer Geography].[Country].&[Australia],[Customer].[Customer Geography].[Country].&[United States]})'  select   {[Week Count]} on columns from   [Adventure Works]    where   [Date].[Fiscal Weeks].[CM]   2008 R2 seems to work as long as the AGGREGATE member is on at least one of the hierarchies attempting to be detected (i.e. [Date].[Fiscal Weeks] or [Customer].[Customer Geography]). If not, it seems that the engine cannot find a "point of entry" into the aggregate member and ignores it for calculated members.   One way around this would be to put the sets from the AGGREGATE member explicitly in the WHERE clause (slicer).  I realize this is only supported in SSAS 2005 and 2008.  However, after talking with Chris Webb (his blog is here and I highly recommend following his efforts and musings) it is a far more efficient way to filter/slice a query:   With   member [Week Count] as 'count(existing([Date].[Fiscal Weeks].[Fiscal Week].members))'    select   {[Week Count]} on columns from   [Adventure Works]    where   ({[Date].[Fiscal Weeks].[Fiscal Week].&[47]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[48]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[49]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[50]&[2004]}   ,{[Customer].[Customer Geography].[Country].&[Australia],[Customer].[Customer Geography].[Country].&[United States]})   This query returns the correct result of (4) weeks.  Additionally, we can count the cross-join members of the two hierarchies in the slicer:   With   member [Week Count] as 'count(existing([Date].[Fiscal Weeks].[Fiscal Week].members)*existing([Customer].[Customer Geography].[Country].members))'    select   {[Week Count]} on columns from   [Adventure Works]    where   ({[Date].[Fiscal Weeks].[Fiscal Week].&[47]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[48]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[49]&[2004],[Date].[Fiscal Weeks].[Fiscal Week].&[50]&[2004]}   ,{[Customer].[Customer Geography].[Country].&[Australia],[Customer].[Customer Geography].[Country].&[United States]})   We get the correct number of (8) here.

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• Ogre 3d and bullet physics interaction

  - by Tim

  I have been playing around with Ogre3d and trying to integrate bullet physics. I have previously somewhat successfully got this functionality working with irrlicht and bullet and I am trying to base this on what I had done there, but modifying it to fit with Ogre. It is working but not correctly and I would like some help to understand what it is I am doing wrong. I have a state system and when I enter the "gamestate" I call some functions such as setting up a basic scene, creating the physics simulation. I am doing that as follows. void GameState::enter() { ... // Setup Physics btBroadphaseInterface *BroadPhase = new btAxisSweep3(btVector3(-1000,-1000,-1000), btVector3(1000,1000,1000)); btDefaultCollisionConfiguration *CollisionConfiguration = new btDefaultCollisionConfiguration(); btCollisionDispatcher *Dispatcher = new btCollisionDispatcher(CollisionConfiguration); btSequentialImpulseConstraintSolver *Solver = new btSequentialImpulseConstraintSolver(); World = new btDiscreteDynamicsWorld(Dispatcher, BroadPhase, Solver, CollisionConfiguration); ... createScene(); } In the createScene method I add a light and try to setup a "ground" plane to act as the ground for things to collide with.. as follows. I expect there is issues with this as I get objects colliding with the ground but half way through it and they glitch around like crazy on collision. void GameState::createScene() { m_pSceneMgr->createLight("Light")->setPosition(75,75,75); // Physics // As a test we want a floor plane for things to collide with Ogre::Entity *ent; Ogre::Plane p; p.normal = Ogre::Vector3(0,1,0); p.d = 0; Ogre::MeshManager::getSingleton().createPlane( "FloorPlane", Ogre::ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME, p, 200000, 200000, 20, 20, true, 1, 9000,9000,Ogre::Vector3::UNIT_Z); ent = m_pSceneMgr->createEntity("floor", "FloorPlane"); ent->setMaterialName("Test/Floor"); Ogre::SceneNode *node = m_pSceneMgr->getRootSceneNode()->createChildSceneNode(); node->attachObject(ent); btTransform Transform; Transform.setIdentity(); Transform.setOrigin(btVector3(0,1,0)); // Give it to the motion state btDefaultMotionState *MotionState = new btDefaultMotionState(Transform); btCollisionShape *Shape = new btStaticPlaneShape(btVector3(0,1,0),0); // Add Mass btVector3 LocalInertia; Shape->calculateLocalInertia(0, LocalInertia); // CReate the rigid body object btRigidBody *RigidBody = new btRigidBody(0, MotionState, Shape, LocalInertia); // Store a pointer to the Ogre Node so we can update it later RigidBody->setUserPointer((void *) (node)); // Add it to the physics world World->addRigidBody(RigidBody); Objects.push_back(RigidBody); m_pNumEntities++; // End Physics } I then have a method to create a cube and give it rigid body physics properties. I know there will be errors here as I get the items colliding with the ground but not with each other properly. So I would appreciate some input on what I am doing wrong. void GameState::CreateBox(const btVector3 &TPosition, const btVector3 &TScale, btScalar TMass) { Ogre::Vector3 size = Ogre::Vector3::ZERO; Ogre::Vector3 pos = Ogre::Vector3::ZERO; Ogre::Vector3 scale = Ogre::Vector3::ZERO; pos.x = TPosition.getX(); pos.y = TPosition.getY(); pos.z = TPosition.getZ(); scale.x = TScale.getX(); scale.y = TScale.getY(); scale.z = TScale.getZ(); Ogre::Entity *entity = m_pSceneMgr->createEntity( "Box" + Ogre::StringConverter::toString(m_pNumEntities), "cube.mesh"); entity->setCastShadows(true); Ogre::AxisAlignedBox boundingB = entity->getBoundingBox(); size = boundingB.getSize(); //size /= 2.0f; // Only the half needed? //size *= 0.96f; // Bullet margin is a bit bigger so we need a smaller size entity->setMaterialName("Test/Cube"); Ogre::SceneNode *node = m_pSceneMgr->getRootSceneNode()->createChildSceneNode(); node->attachObject(entity); node->setPosition(pos); //node->scale(scale); // Physics btTransform Transform; Transform.setIdentity(); Transform.setOrigin(TPosition); // Give it to the motion state btDefaultMotionState *MotionState = new btDefaultMotionState(Transform); btVector3 HalfExtents(TScale.getX()*0.5f,TScale.getY()*0.5f,TScale.getZ()*0.5f); btCollisionShape *Shape = new btBoxShape(HalfExtents); // Add Mass btVector3 LocalInertia; Shape->calculateLocalInertia(TMass, LocalInertia); // CReate the rigid body object btRigidBody *RigidBody = new btRigidBody(TMass, MotionState, Shape, LocalInertia); // Store a pointer to the Ogre Node so we can update it later RigidBody->setUserPointer((void *) (node)); // Add it to the physics world World->addRigidBody(RigidBody); Objects.push_back(RigidBody); m_pNumEntities++; } Then in the GameState::update() method which which runs every frame to handle input and render etc I call an UpdatePhysics method to update the physics simulation. void GameState::UpdatePhysics(unsigned int TDeltaTime) { World->stepSimulation(TDeltaTime * 0.001f, 60); btRigidBody *TObject; for(std::vector<btRigidBody *>::iterator it = Objects.begin(); it != Objects.end(); ++it) { // Update renderer Ogre::SceneNode *node = static_cast<Ogre::SceneNode *>((*it)->getUserPointer()); TObject = *it; // Set position btVector3 Point = TObject->getCenterOfMassPosition(); node->setPosition(Ogre::Vector3((float)Point[0], (float)Point[1], (float)Point[2])); // set rotation btVector3 EulerRotation; QuaternionToEuler(TObject->getOrientation(), EulerRotation); node->setOrientation(1,(Ogre::Real)EulerRotation[0], (Ogre::Real)EulerRotation[1], (Ogre::Real)EulerRotation[2]); //node->rotate(Ogre::Vector3(EulerRotation[0], EulerRotation[1], EulerRotation[2])); } } void GameState::QuaternionToEuler(const btQuaternion &TQuat, btVector3 &TEuler) { btScalar W = TQuat.getW(); btScalar X = TQuat.getX(); btScalar Y = TQuat.getY(); btScalar Z = TQuat.getZ(); float WSquared = W * W; float XSquared = X * X; float YSquared = Y * Y; float ZSquared = Z * Z; TEuler.setX(atan2f(2.0f * (Y * Z + X * W), -XSquared - YSquared + ZSquared + WSquared)); TEuler.setY(asinf(-2.0f * (X * Z - Y * W))); TEuler.setZ(atan2f(2.0f * (X * Y + Z * W), XSquared - YSquared - ZSquared + WSquared)); TEuler *= RADTODEG; } I seem to have issues with the cubes not colliding with each other and colliding strangely with the ground. I have tried to capture the effect with the attached image. I would appreciate any help in understanding what I have done wrong. Thanks. EDIT : Solution The following code shows the changes I made to get accurate physics. void GameState::createScene() { m_pSceneMgr->createLight("Light")->setPosition(75,75,75); // Physics // As a test we want a floor plane for things to collide with Ogre::Entity *ent; Ogre::Plane p; p.normal = Ogre::Vector3(0,1,0); p.d = 0; Ogre::MeshManager::getSingleton().createPlane( "FloorPlane", Ogre::ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME, p, 200000, 200000, 20, 20, true, 1, 9000,9000,Ogre::Vector3::UNIT_Z); ent = m_pSceneMgr->createEntity("floor", "FloorPlane"); ent->setMaterialName("Test/Floor"); Ogre::SceneNode *node = m_pSceneMgr->getRootSceneNode()->createChildSceneNode(); node->attachObject(ent); btTransform Transform; Transform.setIdentity(); // Fixed the transform vector here for y back to 0 to stop the objects sinking into the ground. Transform.setOrigin(btVector3(0,0,0)); // Give it to the motion state btDefaultMotionState *MotionState = new btDefaultMotionState(Transform); btCollisionShape *Shape = new btStaticPlaneShape(btVector3(0,1,0),0); // Add Mass btVector3 LocalInertia; Shape->calculateLocalInertia(0, LocalInertia); // CReate the rigid body object btRigidBody *RigidBody = new btRigidBody(0, MotionState, Shape, LocalInertia); // Store a pointer to the Ogre Node so we can update it later RigidBody->setUserPointer((void *) (node)); // Add it to the physics world World->addRigidBody(RigidBody); Objects.push_back(RigidBody); m_pNumEntities++; // End Physics } void GameState::CreateBox(const btVector3 &TPosition, const btVector3 &TScale, btScalar TMass) { Ogre::Vector3 size = Ogre::Vector3::ZERO; Ogre::Vector3 pos = Ogre::Vector3::ZERO; Ogre::Vector3 scale = Ogre::Vector3::ZERO; pos.x = TPosition.getX(); pos.y = TPosition.getY(); pos.z = TPosition.getZ(); scale.x = TScale.getX(); scale.y = TScale.getY(); scale.z = TScale.getZ(); Ogre::Entity *entity = m_pSceneMgr->createEntity( "Box" + Ogre::StringConverter::toString(m_pNumEntities), "cube.mesh"); entity->setCastShadows(true); Ogre::AxisAlignedBox boundingB = entity->getBoundingBox(); // The ogre bounding box is slightly bigger so I am reducing it for // use with the rigid body. size = boundingB.getSize()*0.95f; entity->setMaterialName("Test/Cube"); Ogre::SceneNode *node = m_pSceneMgr->getRootSceneNode()->createChildSceneNode(); node->attachObject(entity); node->setPosition(pos); node->showBoundingBox(true); //node->scale(scale); // Physics btTransform Transform; Transform.setIdentity(); Transform.setOrigin(TPosition); // Give it to the motion state btDefaultMotionState *MotionState = new btDefaultMotionState(Transform); // I got the size of the bounding box above but wasn't using it to set // the size for the rigid body. This now does. btVector3 HalfExtents(size.x*0.5f,size.y*0.5f,size.z*0.5f); btCollisionShape *Shape = new btBoxShape(HalfExtents); // Add Mass btVector3 LocalInertia; Shape->calculateLocalInertia(TMass, LocalInertia); // CReate the rigid body object btRigidBody *RigidBody = new btRigidBody(TMass, MotionState, Shape, LocalInertia); // Store a pointer to the Ogre Node so we can update it later RigidBody->setUserPointer((void *) (node)); // Add it to the physics world World->addRigidBody(RigidBody); Objects.push_back(RigidBody); m_pNumEntities++; } void GameState::UpdatePhysics(unsigned int TDeltaTime) { World->stepSimulation(TDeltaTime * 0.001f, 60); btRigidBody *TObject; for(std::vector<btRigidBody *>::iterator it = Objects.begin(); it != Objects.end(); ++it) { // Update renderer Ogre::SceneNode *node = static_cast<Ogre::SceneNode *>((*it)->getUserPointer()); TObject = *it; // Set position btVector3 Point = TObject->getCenterOfMassPosition(); node->setPosition(Ogre::Vector3((float)Point[0], (float)Point[1], (float)Point[2])); // Convert the bullet Quaternion to an Ogre quaternion btQuaternion btq = TObject->getOrientation(); Ogre::Quaternion quart = Ogre::Quaternion(btq.w(),btq.x(),btq.y(),btq.z()); // use the quaternion with setOrientation node->setOrientation(quart); } } The QuaternionToEuler function isn't needed so that was removed from code and header files. The objects now collide with the ground and each other appropriately.

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• C#/.NET Little Wonders: The Timeout static class

  - by James Michael Hare

  Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. When I started the “Little Wonders” series, I really wanted to pay homage to parts of the .NET Framework that are often small but can help in big ways.  The item I have to discuss today really is a very small item in the .NET BCL, but once again I feel it can help make the intention of code much clearer and thus is worthy of note. The Problem - Magic numbers aren’t very readable or maintainable In my first Little Wonders Post (Five Little Wonders That Make Code Better) I mention the TimeSpan factory methods which, I feel, really help the readability of constructed TimeSpan instances. Just to quickly recap that discussion, ask yourself what the TimeSpan specified in each case below is 1: // Five minutes? Five Seconds? 2: var fiveWhat1 = new TimeSpan(0, 0, 5); 3: var fiveWhat2 = new TimeSpan(0, 0, 5, 0); 4: var fiveWhat3 = new TimeSpan(0, 0, 5, 0, 0); You’d think they’d all be the same unit of time, right?  After all, most overloads tend to tack additional arguments on the end.  But this is not the case with TimeSpan, where the constructor forms are:     TimeSpan(int hours, int minutes, int seconds);     TimeSpan(int days, int hours, int minutes, int seconds);     TimeSpan(int days, int hours, int minutes, int seconds, int milliseconds); Notice how in the 4 and 5 parameter version we suddenly have the parameter days slipping in front of hours?  This can make reading constructors like those above much harder.  Fortunately, there are TimeSpan factory methods to help make your intention crystal clear: 1: // Ah! Much clearer! 2: var fiveSeconds = TimeSpan.FromSeconds(5); These are great because they remove all ambiguity from the reader!  So in short, magic numbers in constructors and methods can be ambiguous, and anything we can do to clean up the intention of the developer will make the code much easier to read and maintain. Timeout – Readable identifiers for infinite timeout values In a similar way to TimeSpan, let’s consider specifying timeouts for some of .NET’s (or our own) many methods that allow you to specify timeout periods. For example, in the TPL Task class, there is a family of Wait() methods that can take TimeSpan or int for timeouts.  Typically, if you want to specify an infinite timeout, you’d just call the version that doesn’t take a timeout parameter at all: 1: myTask.Wait(); // infinite wait But there are versions that take the int or TimeSpan for timeout as well: 1: // Wait for 100 ms 2: myTask.Wait(100); 3:  4: // Wait for 5 seconds 5: myTask.Wait(TimeSpan.FromSeconds(5); Now, if we want to specify an infinite timeout to wait on the Task, we could pass –1 (or a TimeSpan set to –1 ms), which what the .NET BCL methods with timeouts use to represent an infinite timeout: 1: // Also infinite timeouts, but harder to read/maintain 2: myTask.Wait(-1); 3: myTask.Wait(TimeSpan.FromMilliseconds(-1)); However, these are not as readable or maintainable.  If you were writing this code, you might make the mistake of thinking 0 or int.MaxValue was an infinite timeout, and you’d be incorrect.  Also, reading the code above it isn’t as clear that –1 is infinite unless you happen to know that is the specified behavior. To make the code like this easier to read and maintain, there is a static class called Timeout in the System.Threading namespace which contains definition for infinite timeouts specified as both int and TimeSpan forms: Timeout.Infinite An integer constant with a value of –1 Timeout.InfiniteTimeSpan A static readonly TimeSpan which represents –1 ms (only available in .NET 4.5+) This makes our calls to Task.Wait() (or any other calls with timeouts) much more clear: 1: // intention to wait indefinitely is quite clear now 2: myTask.Wait(Timeout.Infinite); 3: myTask.Wait(Timeout.InfiniteTimeSpan); But wait, you may say, why would we care at all?  Why not use the version of Wait() that takes no arguments?  Good question!  When you’re directly calling the method with an infinite timeout that’s what you’d most likely do, but what if you are just passing along a timeout specified by a caller from higher up?  Or perhaps storing a timeout value from a configuration file, and want to default it to infinite? For example, perhaps you are designing a communications module and want to be able to shutdown gracefully, but if you can’t gracefully finish in a specified amount of time you want to force the connection closed.  You could create a Shutdown() method in your class, and take a TimeSpan or an int for the amount of time to wait for a clean shutdown – perhaps waiting for client to acknowledge – before terminating the connection.  So, assume we had a pub/sub system with a class to broadcast messages: 1: // Some class to broadcast messages to connected clients 2: public class Broadcaster 3: { 4: // ... 5:  6: // Shutdown connection to clients, wait for ack back from clients 7: // until all acks received or timeout, whichever happens first 8: public void Shutdown(int timeout) 9: { 10: // Kick off a task here to send shutdown request to clients and wait 11: // for the task to finish below for the specified time... 12:  13: if (!shutdownTask.Wait(timeout)) 14: { 15: // If Wait() returns false, we timed out and task 16: // did not join in time. 17: } 18: } 19: } We could even add an overload to allow us to use TimeSpan instead of int, to give our callers the flexibility to specify timeouts either way: 1: // overload to allow them to specify Timeout in TimeSpan, would 2: // just call the int version passing in the TotalMilliseconds... 3: public void Shutdown(TimeSpan timeout) 4: { 5: Shutdown(timeout.TotalMilliseconds); 6: } Notice in case of this class, we don’t assume the caller wants infinite timeouts, we choose to rely on them to tell us how long to wait.  So now, if they choose an infinite timeout, they could use the –1, which is more cryptic, or use Timeout class to make the intention clear: 1: // shutdown the broadcaster, waiting until all clients ack back 2: // without timing out. 3: myBroadcaster.Shutdown(Timeout.Infinite); We could even add a default argument using the int parameter version so that specifying no arguments to Shutdown() assumes an infinite timeout: 1: // Modified original Shutdown() method to add a default of 2: // Timeout.Infinite, works because Timeout.Infinite is a compile 3: // time constant. 4: public void Shutdown(int timeout = Timeout.Infinite) 5: { 6: // same code as before 7: } Note that you can’t default the ShutDown(TimeSpan) overload with Timeout.InfiniteTimeSpan since it is not a compile-time constant.  The only acceptable default for a TimeSpan parameter would be default(TimeSpan) which is zero milliseconds, which specified no wait, not infinite wait. Summary While Timeout.Infinite and Timeout.InfiniteTimeSpan are not earth-shattering classes in terms of functionality, they do give you very handy and readable constant values that you can use in your programs to help increase readability and maintainability when specifying infinite timeouts for various timeouts in the BCL and your own applications. Technorati Tags: C#,CSharp,.NET,Little Wonders,Timeout,Task

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• C++ Little Wonders: The C++11 auto keyword redux

  - by James Michael Hare

  I’ve decided to create a sub-series of my Little Wonders posts to focus on C++.  Just like their C# counterparts, these posts will focus on those features of the C++ language that can help improve code by making it easier to write and maintain.  The index of the C# Little Wonders can be found here. This has been a busy week with a rollout of some new website features here at my work, so I don’t have a big post for this week.  But I wanted to write something up, and since lately I’ve been renewing my C++ skills in a separate project, it seemed like a good opportunity to start a C++ Little Wonders series.  Most of my development work still tends to focus on C#, but it was great to get back into the saddle and renew my C++ knowledge.  Today I’m going to focus on a new feature in C++11 (formerly known as C++0x, which is a major move forward in the C++ language standard).  While this small keyword can seem so trivial, I feel it is a big step forward in improving readability in C++ programs. The auto keyword If you’ve worked on C++ for a long time, you probably have some passing familiarity with the old auto keyword as one of those rarely used C++ keywords that was almost never used because it was the default. That is, in the code below (before C++11): 1: int foo() 2: { 3: // automatic variables (allocated and deallocated on stack) 4: int x; 5: auto int y; 6:  7: // static variables (retain their value across calls) 8: static int z; 9:  10: return 0; 11: } The variable x is assumed to be auto because that is the default, thus it is unnecessary to specify it explicitly as in the declaration of y below that.  Basically, an auto variable is one that is allocated and de-allocated on the stack automatically.  Contrast this to static variables, that are allocated statically and exist across the lifetime of the program. Because auto was so rarely (if ever) used since it is the norm, they decided to remove it for this purpose and give it new meaning in C++11.  The new meaning of auto: implicit typing Now, if your compiler supports C++ 11 (or at least a good subset of C++11 or 0x) you can take advantage of type inference in C++.  For those of you from the C# world, this means that the auto keyword in C++ now behaves a lot like the var keyword in C#! For example, many of us have had to declare those massive type declarations for an iterator before.  Let’s say we have a std::map of std::string to int which will map names to ages: 1: std::map<std::string, int> myMap; And then let’s say we want to find the age of a given person: 1: // Egad that's a long type... 2: std::map<std::string, int>::const_iterator pos = myMap.find(targetName); Notice that big ugly type definition to declare variable pos?  Sure, we could shorten this by creating a typedef of our specific map type if we wanted, but now with the auto keyword there’s no need: 1: // much shorter! 2: auto pos = myMap.find(targetName); The auto now tells the compiler to determine what type pos should be based on what it’s being assigned to.  This is not dynamic typing, it still determines the type as if it were explicitly declared and once declared that type cannot be changed.  That is, this is invalid: 1: // x is type int 2: auto x = 42; 3:  4: // can't assign string to int 5: x = "Hello"; Once the compiler determines x is type int it is exactly as if we typed int x = 42; instead, so don’t' confuse it with dynamic typing, it’s still very type-safe. An interesting feature of the auto keyword is that you can modify the inferred type: 1: // declare method that returns int* 2: int* GetPointer(); 3:  4: // p1 is int*, auto inferred type is int 5: auto *p1 = GetPointer(); 6:  7: // ps is int*, auto inferred type is int* 8: auto p2 = GetPointer(); Notice in both of these cases, p1 and p2 are determined to be int* but in each case the inferred type was different.  because we declared p1 as auto *p1 and GetPointer() returns int*, it inferred the type int was needed to complete the declaration.  In the second case, however, we declared p2 as auto p2 which means the inferred type was int*.  Ultimately, this make p1 and p2 the same type, but which type is inferred makes a difference, if you are chaining multiple inferred declarations together.  In these cases, the inferred type of each must match the first: 1: // Type inferred is int 2: // p1 is int* 3: // p2 is int 4: // p3 is int& 5: auto *p1 = GetPointer(), p2 = 42, &p3 = p2; Note that this works because the inferred type was int, if the inferred type was int* instead: 1: // syntax error, p1 was inferred to be int* so p2 and p3 don't make sense 2: auto p1 = GetPointer(), p2 = 42, &p3 = p2; You could also use const or static to modify the inferred type: 1: // inferred type is an int, theAnswer is a const int 2: const auto theAnswer = 42; 3:  4: // inferred type is double, Pi is a static double 5: static auto Pi = 3.1415927; Thus in the examples above it inferred the types int and double respectively, which were then modified to const and static. Summary The auto keyword has gotten new life in C++11 to allow you to infer the type of a variable from it’s initialization.  This simple little keyword can be used to cut down large declarations for complex types into a much more readable form, where appropriate.   Technorati Tags: C++, C++11, Little Wonders, auto

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• C#: Optional Parameters - Pros and Pitfalls

  - by James Michael Hare

  When Microsoft rolled out Visual Studio 2010 with C# 4, I was very excited to learn how I could apply all the new features and enhancements to help make me and my team more productive developers. Default parameters have been around forever in C++, and were intentionally omitted in Java in favor of using overloading to satisfy that need as it was though that having too many default parameters could introduce code safety issues.  To some extent I can understand that move, as I’ve been bitten by default parameter pitfalls before, but at the same time I feel like Java threw out the baby with the bathwater in that move and I’m glad to see C# now has them. This post briefly discusses the pros and pitfalls of using default parameters.  I’m avoiding saying cons, because I really don’t believe using default parameters is a negative thing, I just think there are things you must watch for and guard against to avoid abuses that can cause code safety issues. Pro: Default Parameters Can Simplify Code Let’s start out with positives.  Consider how much cleaner it is to reduce all the overloads in methods or constructors that simply exist to give the semblance of optional parameters.  For example, we could have a Message class defined which allows for all possible initializations of a Message: 1: public class Message 2: { 3: // can either cascade these like this or duplicate the defaults (which can introduce risk) 4: public Message() 5: : this(string.Empty) 6: { 7: } 8:  9: public Message(string text) 10: : this(text, null) 11: { 12: } 13:  14: public Message(string text, IDictionary<string, string> properties) 15: : this(text, properties, -1) 16: { 17: } 18:  19: public Message(string text, IDictionary<string, string> properties, long timeToLive) 20: { 21: // ... 22: } 23: }   Now consider the same code with default parameters: 1: public class Message 2: { 3: // can either cascade these like this or duplicate the defaults (which can introduce risk) 4: public Message(string text = "", IDictionary<string, string> properties = null, long timeToLive = -1) 5: { 6: // ... 7: } 8: }   Much more clean and concise and no repetitive coding!  In addition, in the past if you wanted to be able to cleanly supply timeToLive and accept the default on text and properties above, you would need to either create another overload, or pass in the defaults explicitly.  With named parameters, though, we can do this easily: 1: var msg = new Message(timeToLive: 100);   Pro: Named Parameters can Improve Readability I must say one of my favorite things with the default parameters addition in C# is the named parameters.  It lets code be a lot easier to understand visually with no comments.  Think how many times you’ve run across a TimeSpan declaration with 4 arguments and wondered if they were passing in days/hours/minutes/seconds or hours/minutes/seconds/milliseconds.  A novice running through your code may wonder what it is.  Named arguments can help resolve the visual ambiguity: 1: // is this days/hours/minutes/seconds (no) or hours/minutes/seconds/milliseconds (yes) 2: var ts = new TimeSpan(1, 2, 3, 4); 3:  4: // this however is visually very explicit 5: var ts = new TimeSpan(days: 1, hours: 2, minutes: 3, seconds: 4);   Or think of the times you’ve run across something passing a Boolean literal and wondered what it was: 1: // what is false here? 2: var sub = CreateSubscriber(hostname, port, false); 3:  4: // aha! Much more visibly clear 5: var sub = CreateSubscriber(hostname, port, isBuffered: false);   Pitfall: Don't Insert new Default Parameters In Between Existing Defaults Now let’s consider a two potential pitfalls.  The first is really an abuse.  It’s not really a fault of the default parameters themselves, but a fault in the use of them.  Let’s consider that Message constructor again with defaults.  Let’s say you want to add a messagePriority to the message and you think this is more important than a timeToLive value, so you decide to put messagePriority before it in the default, this gives you: 1: public class Message 2: { 3: public Message(string text = "", IDictionary<string, string> properties = null, int priority = 5, long timeToLive = -1) 4: { 5: // ... 6: } 7: }   Oh boy have we set ourselves up for failure!  Why?  Think of all the code out there that could already be using the library that already specified the timeToLive, such as this possible call: 1: var msg = new Message(“An error occurred”, myProperties, 1000);   Before this specified a message with a TTL of 1000, now it specifies a message with a priority of 1000 and a time to live of -1 (infinite).  All of this with NO compiler errors or warnings. So the rule to take away is if you are adding new default parameters to a method that’s currently in use, make sure you add them to the end of the list or create a brand new method or overload. Pitfall: Beware of Default Parameters in Inheritance and Interface Implementation Now, the second potential pitfalls has to do with inheritance and interface implementation.  I’ll illustrate with a puzzle: 1: public interface ITag 2: { 3: void WriteTag(string tagName = "ITag"); 4: } 5:  6: public class BaseTag : ITag 7: { 8: public virtual void WriteTag(string tagName = "BaseTag") { Console.WriteLine(tagName); } 9: } 10:  11: public class SubTag : BaseTag 12: { 13: public override void WriteTag(string tagName = "SubTag") { Console.WriteLine(tagName); } 14: } 15:  16: public static class Program 17: { 18: public static void Main() 19: { 20: SubTag subTag = new SubTag(); 21: BaseTag subByBaseTag = subTag; 22: ITag subByInterfaceTag = subTag; 23:  24: // what happens here? 25: subTag.WriteTag(); 26: subByBaseTag.WriteTag(); 27: subByInterfaceTag.WriteTag(); 28: } 29: }   What happens?  Well, even though the object in each case is SubTag whose tag is “SubTag”, you will get: 1: SubTag 2: BaseTag 3: ITag   Why?  Because default parameter are resolved at compile time, not runtime!  This means that the default does not belong to the object being called, but by the reference type it’s being called through.  Since the SubTag instance is being called through an ITag reference, it will use the default specified in ITag. So the moral of the story here is to be very careful how you specify defaults in interfaces or inheritance hierarchies.  I would suggest avoiding repeating them, and instead concentrating on the layer of classes or interfaces you must likely expect your caller to be calling from. For example, if you have a messaging factory that returns an IMessage which can be either an MsmqMessage or JmsMessage, it only makes since to put the defaults at the IMessage level since chances are your user will be using the interface only. So let’s sum up.  In general, I really love default and named parameters in C# 4.0.  I think they’re a great tool to help make your code easier to read and maintain when used correctly. On the plus side, default parameters: Reduce redundant overloading for the sake of providing optional calling structures. Improve readability by being able to name an ambiguous argument. But remember to make sure you: Do not insert new default parameters in the middle of an existing set of default parameters, this may cause unpredictable behavior that may not necessarily throw a syntax error – add to end of list or create new method. Be extremely careful how you use default parameters in inheritance hierarchies and interfaces – choose the most appropriate level to add the defaults based on expected usage. Technorati Tags: C#,.NET,Software,Default Parameters

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