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• unavailable disc after installing windows7

  - by niao

  Greetings, I know this is a site about programming but I don't know where to put this question. The problem is that after installing Windows7 one partition is unavailable. The error is: "E:\ is unavailable" Access denied. There is no information about available space etc. How can I resolve this problem because there are some very important files on that partition.

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• How do I program the Sparkfun Arduino Pro Micro with Linux?

  - by zeldarulez

  Sparkfun's Arduino Pro Micro was the ideal choice for me (in size and price), but I cannot figure out how to program it on anything other than Windows. Sparkfun doesn't provide any resources on how to program the Arduino Pro Micro on Linux, and there aren't any direct resources on the Internet for installing drivers/ programming it. Hoow do I program the Arduino Pro Micro with Linux? Thanks! Note: My OS is Ubuntu

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• Practical way to implement prevention of IP Spoofing

  - by user1369975

  I am an undergraduate Computer Science student and was hoping to gain some knowledge of ways to help prevent IP spoofing but all the resources I have tried out elaborate this concept in a theoretical way. I want to try out my hands at one of the techniques like: http://en.wikipedia.org/wiki/Port_knocking http://en.wikipedia.org/wiki/SYN_cookies How do I simulate this whole situation in my own system were I myself am the attacker and I myself have to defend it? And once I have gained an understanding of it, then how do I start translating that into programming terms?

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• Which wordpress plugin adds support for [code language="Java"]

  - by Bozho

  in wordpress.com blogs this is working, but on a newly installed wordpress blog it is not. So I assume there is a plugin for this. I tried wp-syntax and bbcode plugins - no success. So, which is this plugin, that allows programming language code to be highlighted

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• Automatic sort for excel worksheet

  - by Joseph

  I want to create a to-do list in Excel that automatically sorts the to-do entries in a list, in order of ones to do first (closest deadlines). I would also like a section that shows the tasks for today and another for high-priority tasks coming up within a week. I have not programmed in Excel before. I know Python and JavaScript, but want an Excel solution that runs inside Excel (maybe using VBA, the Excel programming language). Is this sort of thing possible in Excel?

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• What do you install on a new machine?

  - by person-b

  What programs do you install on a fresh Windows/Linux machine? It doesn't have to be any specific category - programming tools, browsers, anything! Update: If possible, can you post links? It makes it a lot easier for readers.

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• i7 4770k or i7 4930k - Which for faster compile times? [on hold]

  - by Chumm

  I've looked up comparisons and found that single core performance seems to be better on i7 4770k, but has less cores that the i7 4930k. Would VS take advantage of extra cores when compiling, or would the difference be negible. I'm looking to buy the PC primarily for programming, so which would be better for visual studio? I already have the rest of my build ready, I just need to decide on this! :) thanks

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• What vim features do you use?

  - by Frew

  I spend almost all day programming in vim and I am sure that a lot of you do too. What features do you use that make your day to day coding that much better? One that I use is gv, which will let you reselect the previously selected text. Great for reindenting!

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• what's the safest OS?

  - by Bob

  I have pretty important stuff on my PC (using Windows). All the programming files, passwords etc. And now I thought: Is that even safe to store all this information on a hard drive? What if some virus (or a pseudo-antivirus gets it) M.b. it is better to buy Mac for this purpose? I kinda don't like Linux, cause I hate making million small decisions manually (what drivers to install etc) Will like to hear some opinions.

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• Can I automatically map chrome's bookmarks bar to its jump list?

  - by Alex Nye

  I would like the contents of my bookmarks bar to be present in my Google Chrome jump list, without the manual tedium of managing both the bar's organization and contents and those of the jump list. If it's possible to automatically manage jump lists in such a way as to make this possible, I'd be delighted. I don't think I'm quite ready to attempt programming an extension thus myself. edit: it appears this is not possible. I have submitted the feature as a request to the chrome team.

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• Searching major search engines with text such as <%#

  - by Daniel Dyson

  If I type '<%# vs <%"' into any of the major search engines, everything is stripped out except the 'vs'. I understand why they do this. I would just like to know if anyone knows of a way to escape illegal characters so that they are searched properly. I know this is not strictly a programming question, but it is relevant.

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• Prefer extension methods for encapsulation and reusability?

  - by tzaman

  edit4: wikified, since this seems to have morphed more into a discussion than a specific question. In C++ programming, it's generally considered good practice to "prefer non-member non-friend functions" instead of instance methods. This has been recommended by Scott Meyers in this classic Dr. Dobbs article, and repeated by Herb Sutter and Andrei Alexandrescu in C++ Coding Standards (item 44); the general argument being that if a function can do its job solely by relying on the public interface exposed by the class, it actually increases encapsulation to have it be external. While this confuses the "packaging" of the class to some extent, the benefits are generally considered worth it. Now, ever since I've started programming in C#, I've had a feeling that here is the ultimate expression of the concept that they're trying to achieve with "non-member, non-friend functions that are part of a class interface". C# adds two crucial components to the mix - the first being interfaces, and the second extension methods: Interfaces allow a class to formally specify their public contract, the methods and properties that they're exposing to the world. Any other class can choose to implement the same interface and fulfill that same contract. Extension methods can be defined on an interface, providing any functionality that can be implemented via the interface to all implementers automatically. And best of all, because of the "instance syntax" sugar and IDE support, they can be called the same way as any other instance method, eliminating the cognitive overhead! So you get the encapsulation benefits of "non-member, non-friend" functions with the convenience of members. Seems like the best of both worlds to me; the .NET library itself providing a shining example in LINQ. However, everywhere I look I see people warning against extension method overuse; even the MSDN page itself states: In general, we recommend that you implement extension methods sparingly and only when you have to. (edit: Even in the current .NET library, I can see places where it would've been useful to have extensions instead of instance methods - for example, all of the utility functions of List<T> (Sort, BinarySearch, FindIndex, etc.) would be incredibly useful if they were lifted up to IList<T> - getting free bonus functionality like that adds a lot more benefit to implementing the interface.) So what's the verdict? Are extension methods the acme of encapsulation and code reuse, or am I just deluding myself? (edit2: In response to Tomas - while C# did start out with Java's (overly, imo) OO mentality, it seems to be embracing more multi-paradigm programming with every new release; the main thrust of this question is whether using extension methods to drive a style change (towards more generic / functional C#) is useful or worthwhile..) edit3: overridable extension methods The only real problem identified so far with this approach, is that you can't specialize extension methods if you need to. I've been thinking about the issue, and I think I've come up with a solution. Suppose I have an interface MyInterface, which I want to extend - I define my extension methods in a MyExtension static class, and pair it with another interface, call it MyExtensionOverrider. MyExtension methods are defined according to this pattern: public static int MyMethod(this MyInterface obj, int arg, bool attemptCast=true) { if (attemptCast && obj is MyExtensionOverrider) { return ((MyExtensionOverrider)obj).MyMethod(arg); } // regular implementation here } The override interface mirrors all of the methods defined in MyExtension, except without the this or attemptCast parameters: public interface MyExtensionOverrider { int MyMethod(int arg); string MyOtherMethod(); } Now, any class can implement the interface and get the default extension functionality: public class MyClass : MyInterface { ... } Anyone that wants to override it with specific implementations can additionally implement the override interface: public class MySpecializedClass : MyInterface, MyExtensionOverrider { public int MyMethod(int arg) { //specialized implementation for one method } public string MyOtherMethod() { // fallback to default for others MyExtension.MyOtherMethod(this, attemptCast: false); } } And there we go: extension methods provided on an interface, with the option of complete extensibility if needed. Fully general too, the interface itself doesn't need to know about the extension / override, and multiple extension / override pairs can be implemented without interfering with each other. I can see three problems with this approach - It's a little bit fragile - the extension methods and override interface have to be kept synchronized manually. It's a little bit ugly - implementing the override interface involves boilerplate for every function you don't want to specialize. It's a little bit slow - there's an extra bool comparison and cast attempt added to the mainline of every method. Still, all those notwithstanding, I think this is the best we can get until there's language support for interface functions. Thoughts?

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• Inequality joins, Asynchronous transformations and Lookups : SSIS

  - by jamiet

  It is pretty much accepted by SQL Server Integration Services (SSIS) developers that synchronous transformations are generally quicker than asynchronous transformations (for a description of synchronous and asynchronous transformations go read Asynchronous and synchronous data flow components). Notice I said “generally” and not “always”; there are circumstances where using asynchronous transformations can be beneficial and in this blog post I’ll demonstrate such a scenario, one that is pretty common when building data warehouses. Imagine I have a [Customer] dimension table that manages information about all of my customers as a slowly-changing dimension. If that is a type 2 slowly changing dimension then you will likely have multiple rows per customer in that table. Furthermore you might also have datetime fields that indicate the effective time period of each member record. Here is such a table that contains data for four dimension members {Terry, Max, Henry, Horace}: Notice that we have multiple records per customer and that the [SCDStartDate] of a record is equivalent to the [SCDEndDate] of the record that preceded it (if there was one). (Note that I am on record as saying I am not a fan of this technique of storing an [SCDEndDate] but for the purposes of clarity I have included it here.) Anyway, the idea here is that we will have some incoming data containing [CustomerName] & [EffectiveDate] and we need to use those values to lookup [Customer].[CustomerId]. The logic will be: Lookup a [CustomerId] WHERE [CustomerName]=[CustomerName] AND [SCDStartDate] <= [EffectiveDate] AND [EffectiveDate] <= [SCDEndDate] The conventional approach to this would be to use a full cached lookup but that isn’t an option here because we are using inequality conditions. The obvious next step then is to use a non-cached lookup which enables us to change the SQL statement to use inequality operators: Let’s take a look at the dataflow: Notice these are all synchronous components. This approach works just fine however it does have the limitation that it has to issue a SQL statement against your lookup set for every row thus we can expect the execution time of our dataflow to increase linearly in line with the number of rows in our dataflow; that’s not good. OK, that’s the obvious method. Let’s now look at a different way of achieving this using an asynchronous Merge Join transform coupled with a Conditional Split. I’ve shown it post-execution so that I can include the row counts which help to illustrate what is going on here: Notice that there are more rows output from our Merge Join component than on the input. That is because we are joining on [CustomerName] and, as we know, we have multiple records per [CustomerName] in our lookup set. Notice also that there are two asynchronous components in here (the Sort and the Merge Join). I have embedded a video below that compares the execution times for each of these two methods. The video is just over 8minutes long. View on Vimeo  For those that can’t be bothered watching the video I’ll tell you the results here. The dataflow that used the Lookup transform took 36 seconds whereas the dataflow that used the Merge Join took less than two seconds. An illustration in case it is needed: Pretty conclusive proof that in some scenarios it may be quicker to use an asynchronous component than a synchronous one. Your mileage may of course vary. The scenario outlined here is analogous to performance tuning procedural SQL that uses cursors. It is common to eliminate cursors by converting them to set-based operations and that is effectively what we have done here. Our non-cached lookup is performing a discrete operation for every single row of data, exactly like a cursor does. By eliminating this cursor-in-disguise we have dramatically sped up our dataflow. I hope all of that proves useful. You can download the package that I demonstrated in the video from my SkyDrive at http://cid-550f681dad532637.skydrive.live.com/self.aspx/Public/BlogShare/20100514/20100514%20Lookups%20and%20Merge%20Joins.zip Comments are welcome as always. @Jamiet Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• A temporary disagreement

  - by Tony Davis

  Last month, Phil Factor caused a furore amongst some MVPs with an article that attempted to offer simple advice to developers regarding the use of table variables, versus local and global temporary tables, in their code. Phil makes clear that the table variables do come with some fairly major limitations.no distribution statistics, no parallel query plans for queries that modify table variables.but goes on to suggest that for reasonably small-scale strategic uses, and with a bit of due care and testing, table variables are a "good thing". Not everyone shares his opinion; in fact, I imagine he was rather aghast to learn that there were those felt his article was akin to pulling the pin out of a grenade and tossing it into the database; table variables should be avoided in almost all cases, according to their advice, in favour of temp tables. In other words, a fairly major feature of SQL Server should be more-or-less 'off limits' to developers. The problem with temp tables is that, because they are scoped either in the procedure or the connection, it is easy to allow them to hang around for too long, eating up precious memory and bulking up the shared tempdb database. Unless they are explicitly dropped, global temporary tables, and local temporary tables created within a connection rather than within a stored procedure, will persist until the connection is closed or, with connection pooling, until the connection is reused. It's also quite common with ASP.NET applications to have connection leaks, as Bill Vaughn explains in his chapter in the "SQL Server Deep Dives" book, meaning that the web page exits without closing the connection object, maybe due to an error condition. This will then hang around in the heap for what might be hours before picked up by the garbage collector. Table variables are much safer in this regard, since they are batch-scoped and so are cleaned up automatically once the batch is complete, which also means that they are intuitive to use for the developer because they conform to scoping rules that are closer to those in procedural code. On the surface then, an ideal way to deal with issues related to tempdb memory hogging. So why did Phil qualify his recommendation to use Table Variables? This is another of those cases where, like scalar UDFs and table-valued multi-statement UDFs, developers can sometimes get into trouble with a relatively benign-looking feature, due to way it's been implemented in SQL Server. Once again the biggest problem is how they are handled internally, by the SQL Server query optimizer, which can make very poor choices for JOIN orders and so on, in the absence of statistics, especially when joining to tables with highly-skewed data. The resulting execution plans can be horrible, as will be the resulting performance. If the JOIN is to a large table, that will hurt. Ideally, Microsoft would simply fix this issue so that developers can't get burned in this way; they've been around since SQL Server 2000, so Microsoft has had a bit of time to get it right. As I commented in regard to UDFs, when developers discover issues like with such standard features, the database becomes an alien planet to them, where death lurks around each corner, and they continue to avoid these "killer" features years after the problems have been eventually resolved. In the meantime, what is the right approach? Is it to say "hammers can kill, don't ever use hammers", or is it to try to explain, as Phil's article and follow-up blog post have tried to do, what the feature was intended for, why care must be applied in its use, and so enable developers to make properly-informed decisions, without requiring them to delve deep into the inner workings of SQL Server? Cheers, Tony.

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• UPK Hands-on Labs at OHUG

  - by Karen Rihs

  Going to OHUG, June 18-22? Be sure to attend one or more UPK hands-on labs! Choose from Basic, Advanced, What's New, and Prebuilt Content!   Oracle User Productivity Kit 11.1 Workshop – Basic Stephen Armbruster, Oracle Corporation June 19, 2012, 11:00 a.m. – 12:00 p.m. June 20, 2012, 4:30 – 5:30 p.m. The User Productivity Kit (UPK) is a comprehensive, cost-effective, customizable solution that helps your organization quickly create the critical documentation, training, and support materials needed to drive project team and user productivity throughout the lifecycle of your software. The User Productivity Kit provides system process documentation, user acceptance test scripts, comprehensive instructor-led training materials, web-based training materials, role-based performance support, and complete documentation. Also provided is the UPK Developer, which serves as a single-source development and customization tool to enable rapid content creation and customization. The User Productivity Kit delivers: Business process documentation for fit-gap analysis - providing time and cost savings that jump-start your implementation or upgrade User Acceptance test scripts to help test applications prior to go-live State-of-the-art instructional design tools to rapidly build and tailor documentation, instructor-led training materials, and web-based training to fit organizational needs Live-application performance support with transactional and procedural information to maximize user efficiency. By registering for this hands-on UPK workshop, participants will use UPK to build an application job aid and simulation that can be used as performance support for the application. But hurry, space is limited! Oracle User Productivity Kit 11.1 Workshop – Advanced Stephen Armbruster, Oracle Corporation June 20, 2012, 1:30 – 2:30 p.m. This special workshop is for those already familiar with UPK and will cover advanced concepts. In this workshop, you will gain an in-depth knowledge of working with the UPK Developer. Following this workshop, you will be able to: Create publishing categories Add a logo to a publishing project Publish using the newly created category Configure your own library view Manage topic history in a multi-user environment Oracle User Productivity Kit 11.1 Workshop – What’s NEW! Stephen Armbruster, Oracle Corporation June 19, 2012, 1:30 – 2:30 p.m. June 21, 2012, 1:00 – 2:00 p.m. This special workshop is for those already familiar with UPK and will focus on the new features included in the latest version 11.1. In this workshop, you will review most of the new features included in the UPK Developer. Oracle User Productivity Kit 11.1 Workshop – Prebuilt Content Stephen Armbruster, Oracle Corporation June 19, 2012, 4:30 – 5:30 p.m. June 21, 2012, 2:15 – 3:15 p.m. This special workshop is for those already familiar with UPK and will focus on the latest version 11.1. At the end of this workshop, you will be able to demonstrate how to: Import prebuilt content Modify content frames Add a decision frame Translate a topic into Spanish Stephen Armbruster is a principal sales consultant, specializing in HCM and UPK applications for Oracle over the past twelve years. In addition to his current role, he serves as an ambassador for the Fusion User Experience (UX) team and is tasked with evangelizing the UX for end users across all Oracle brands (Fusion, PSFT, JDE, and EBS).  He is also a trusted advisor to Oracle’s Product Management teams related to Learning Management Systems (LMS). Prior to joining Oracle, he was an instructor as well as an instructional technologist working in the medical diagnostics, high tech, and information management industries. As an expert in both LMS and UPK, he regularly speaks at Oracle conferences including Oracle OpenWorld and OHUG on topics that span using Oracle solutions to accomplish employee training, certification, and user adoption. His presentations are both entertaining and engaging.

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• Some Original Expressions

  - by Phil Factor

  Guest Editorial for Simple-Talk newsletterIn a guest editorial for the Simple-Talk Newsletter, Phil Factor wonders if we are still likely to find some more novel and unexpected ways of using the newer features of Transact SQL: or maybe in some features that have always been there! There can be a great deal of fun to be had in trying out recent features of SQL Expressions to see if  they provide new functionality.  It is surprisingly rare to find things that couldn’t be done before, but in a different   and more cumbersome way; but it is great to experiment or to read of someone else making that discovery.  One such recent feature is the ‘table value constructor’, or ‘VALUES constructor’, that managed to get into SQL Server 2008 from Standard SQL.  This allows you to create derived tables of up to 1000 rows neatly within select statements that consist of  lists of row values.  E.g. SELECT Old_Welsh, number FROM (VALUES ('Un',1),('Dou',2),('Tri',3),('Petuar',4),('Pimp',5),('Chwech',6),('Seith',7),('Wyth',8),('Nau',9),('Dec',10)) AS WelshWordsToTen (Old_Welsh, number) These values can be expressions that return single values, including, surprisingly, subqueries. You can use this device to create views, or in the USING clause of a MERGE statement. Joe Celko covered  this here and here.  It can become extraordinarily handy to use once one gets into the way of thinking in these terms, and I’ve rewritten a lot of routines to use the constructor, but the old way of using UNION can be used the same way, but is a little slower and more long-winded. The use of scalar SQL subqueries as an expression in a VALUES constructor, and then applied to a MERGE, has got me thinking. It looks very clever, but what use could one put it to? I haven’t seen anything yet that couldn’t be done almost as  simply in SQL Server 2000, but I’m hopeful that someone will come up with a way of solving a tricky problem, just in the same way that a freak of the XML syntax forever made the in-line  production of delimited lists from an expression easy, or that a weird XML pirouette could do an elegant  pivot-table rotation. It is in this sort of experimentation where the community of users can make a real contribution. The dissemination of techniques such as the Number, or Tally table, or the unconventional ways that the UPDATE statement can be used, has been rapid due to articles and blogs. However, there is plenty to be done to explore some of the less obvious features of Transact SQL. Even some of the features introduced into SQL Server 2000 are hardly well-known. Certain operations on data are still awkward to perform in Transact SQL, but we mustn’t, I think, be too ready to state that certain things can only be done in the application layer, or using a CLR routine. With the vast array of features in the product, and with the tools that surround it, I feel that there is generally a way of getting tricky things done. Or should we just stick to our lasts and push anything difficult out into procedural code? I’d love to know your views.

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• Oracle Tutor: XPDL conversion (and why you should care)

  - by mary.keane

  You may have noticed that the Oracle Business Process Converter feature in Tutor 14 supports "XPDL" conversion to Oracle Business Process Analysis Suite (BPA), Oracle Business Process Management Suite (BPM), and Oracle Tutor, and you may have briefly wondered "what is XPDL?" before you moved on to the Visio import feature (a very popular feature in Tutor 14). This posting is for those who do not yet understand (or care) about XPDL and process modeling. Many of us (and I'm including myself) have spent years working in the process definition arena: we've written procedures, designed systems and software to help others write procedures, and have been responsible for embedding policies and procedures into training material for employees. We've worked with tools such as Oracle Tutor, Microsoft Visio, Microsoft Word, and UPK. Most of us have never worked with "modeling tools" before, and we certainly never had to understand BPMN. It's a brave new world in this arena, and companies desperately need people with policy and procedural system expertise to be able to work with system analysts so there is a seamless transfer of knowledge from IT to employees. When working with applications, a picture is worth a thousand words, so eventually you're going to need to understand and be able to work with business process models. XPDL is an acronym for XML Process Definition Language, and it is an interchange format for business process models. It allows you to take a BPMN model that was developed in one workflow application such as BizAgi and import it into another workflow application or a true BPMN management system such as Oracle BPM. Specifically, the XPDL format contains the graphical information of a model as well as any executable information. By using a common format, models can be moved from a basic modeling application used by business owners to applications used by system architects. Over 80 applications support the XPDL format, including MetaStorm ProVision, BEA ALBPM, BizAgi, and Tibco. I mention these applications because we have provided XSLT mapping files specifically for these vendors. Oracle Business Process Converter was designed with user extensibility in mind, and thus users can add their own XML files so that additional XPDL models from other vendors can be converted to BPM, BPA, and Oracle Tutor. Instructions on how to add your own files can be found in Appendix 4 of the Oracle Business Converter manual. Let's take a visual look at how this works. Here is an example of a model devloped in BizAgi: This model can be created by the average business user without a large learning curve, and it's a good start for the system analyst who will be adding web services as well as for the business manager who manages the process described in the model. By exporting this model as XPDL, the information can be converted into Oracle BPA and Oracle BPM as well as converted to Oracle Tutor to become the framework for a procedure. Through this conversion feature, one graphic illustration of a business process can be used by a system analyst, business analyst, business manager, and employee, as seen below. Model Converted to Tutor Procedure Below is the task section of the procedure after conversion from an XPDL file. Model converted to BPA Model converted to BPM End users still want step by step instructions on how to perform their jobs, so procedures (Oracle Tutor) and application simulations (UPK) are still a critical piece of the solution. But IT professionals need graphic descriptions of how the applications work, regardless of whether there are any tasks involving humans. Now there is a way to convert procedures (Oracle Tutor docx files) and basic models (XPDL files) so that business managers and system analysts can share process information. References Wikipedia XPDL. Workflow Management Coalition, XPDL Support and Resources Oracle Business Process Converter manual, Oracle Tutor 14 Oracle Business Process Management 11g If you have any XPDL conversion stories to share, we'd love to hear from you. Best wishes for the coming new year, Mary Keane, Senior Development Manager, Oracle Tutor and BPM

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• Clever memory usage through the years

  - by Ben Emmett

  A friend and I were recently talking about the really clever tricks people have used to get the most out of memory. I thought I’d share my favorites, and would love to hear yours too! Interleaving on drum memory Back in the ye olde days before I’d been born (we’re talking the 50s / 60s here), working memory commonly took the form of rotating magnetic drums. These would spin at a constant speed, and a fixed head would read from memory when the correct part of the drum passed it by, a bit like a primitive platter disk. Because each revolution took a few milliseconds, programmers took to manually arranging information non-sequentially on the drum, timing when an instruction or memory address would need to be accessed, then spacing information accordingly around the edge of the drum, thus reducing the access delay. Similar techniques were still used on hard disks and floppy disks into the 90s, but have become irrelevant with modern disk technologies. The Hashlife algorithm Conway’s Game of Life has attracted numerous implementations over the years, but Bill Gosper’s Hashlife algorithm is particularly impressive. Taking advantage of the repetitive nature of many cellular automata, it uses a quadtree structure to store the hashes of pieces of the overall grid. Over time there are fewer and fewer new structures which need to be evaluated, so it starts to run faster with larger grids, drastically outperforming other algorithms both in terms of speed and the size of grid which can be simulated. The actual amount of memory used is huge, but it’s used in a clever way, so makes the list . Elite’s procedural generation Ok, so this isn’t exactly a memory optimization – more a storage optimization – but it gets an honorable mention anyway. When writing Elite, David Braben and Ian Bell wanted to build a rich world which gamers could explore, but their 22K memory was something of a limitation (for comparison that’s about the size of my avatar picture at the top of this page). They procedurally generated all the characteristics of the 2048 planets in their virtual universe, including the names, which were stitched together using a lookup table of parts of names. In fact the original plans were for 2^52 planets, but it was decided that that was probably too many. Oh, and they did that all in assembly language. Other games of the time used similar techniques too – The Sentinel’s landscape generation algorithm being another example. Modern Garbage Collectors Garbage collection in managed languages like Java and .NET ensures that most of the time, developers stop needing to care about how they use and clean up memory as the garbage collector handles it automatically. Achieving this without killing performance is a near-miraculous feet of software engineering. Much like when learning chemistry, you find that every time you think you understand how the garbage collector works, it turns out to be a mere simplification; that there are yet more complexities and heuristics to help it run efficiently. Of course introducing memory problems is still possible (and there are tools like our memory profiler to help if that happens to you) but they’re much, much rarer. A cautionary note In the examples above, there were good and well understood reasons for the optimizations, but cunningly optimized code has usually had to trade away readability and maintainability to achieve its gains. Trying to optimize memory usage without being pretty confident that there’s actually a problem is doing it wrong. So what have I missed? Tell me about the ingenious (or stupid) tricks you’ve seen people use. Ben

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• RPi and Java Embedded GPIO: Big Data and Java Technology

  - by hinkmond

  Java Embedded and Big Data go hand-in-hand, especially as demonstrated by prototyping on a Raspberry Pi to show how well the Java Embedded platform can perform on a small embedded device which then becomes the proof-of-concept for industrial controllers, medical equipment, networking gear or any type of sensor-connected device generating large amounts of data. The key is a fast and reliable way to access that data using Java technology. In the previous blog posts you've seen the integration of a static electricity sensor and the Raspberry Pi through the GPIO port, then accessing that data through Java Embedded code. It's important to point out how this works and why it works well with Java code. First, the version of Linux (Debian Wheezy/Raspian) that is found on the RPi has a very convenient way to access the GPIO ports through the use of Linux OS managed file handles. This is key in avoiding terrible and complex coding using register manipulation in C code, or having to program in a less elegant and clumsy procedural scripting language such as python. Instead, using Java Embedded, allows a fast way to access those GPIO ports through those same Linux file handles. Java already has a very easy to program way to access file handles with a high degree of performance that matches direct access of those file handles with the Linux OS. Using the Java API java.io.FileWriter lets us open the same file handles that the Linux OS has for accessing the GPIO ports. Then, by first resetting the ports using the unexport and export file handles, we can initialize them for easy use in a Java app. // Open file handles to GPIO port unexport and export controls FileWriter unexportFile = new FileWriter("/sys/class/gpio/unexport"); FileWriter exportFile = new FileWriter("/sys/class/gpio/export"); ... // Reset the port unexportFile.write(gpioChannel); unexportFile.flush(); // Set the port for use exportFile.write(gpioChannel); exportFile.flush(); Then, another set of file handles can be used by the Java app to control the direction of the GPIO port by writing either "in" or "out" to the direction file handle. // Open file handle to input/output direction control of port FileWriter directionFile = new FileWriter("/sys/class/gpio/gpio" + gpioChannel + "/direction"); // Set port for input directionFile.write("in"); // Or, use "out" for output directionFile.flush(); And, finally, a RandomAccessFile handle can be used with a high degree of performance on par with native C code (only milliseconds to read in data and write out data) with low overhead (unlike python) to manipulate the data going in and out on the GPIO port, while the object-oriented nature of Java programming allows for an easy way to construct complex analytic software around that data access functionality to the external world. RandomAccessFile[] raf = new RandomAccessFile[GpioChannels.length]; ... // Reset file seek pointer to read latest value of GPIO port raf[channum].seek(0); raf[channum].read(inBytes); inLine = new String(inBytes); It's Big Data from sensors and industrial/medical/networking equipment meeting complex analytical software on a small constraint device (like a Linux/ARM RPi) where Java Embedded allows you to shine as an Embedded Device Software Designer. Hinkmond

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• Oracle GoldenGate Active-Active Part 1

  - by Nick_W

  My name is Nick Wagner, and I'm a recent addition to the Oracle Maximum Availability Architecture (MAA) product management team.  I've spent the last 15+ years working on database replication products, and I've spent the last 10 years working on the Oracle GoldenGate product.  So most of my posting will probably be focused on OGG.  One question that comes up all the time is around active-active replication with Oracle GoldenGate.  How do I know if my application is a good fit for active-active replication with GoldenGate?   To answer that, it really comes down to how you plan on handling conflict resolution.  I will delve into topology and deployment in a later blog, but here is a simple architecture: The two most common resolution routines are host based resolution and timestamp based resolution. Host based resolution is used less often, but works with the fewest application changes.  Think of it like this: any transactions from SystemA always take precedence over any transactions from SystemB.  If there is a conflict on SystemB, then the record from SystemA will overwrite it.  If there is a conflict on SystemA, then it will be ignored.  It is quite a bit less restrictive, and in most cases, as long as all the tables have primary keys, host based resolution will work just fine.  Timestamp based resolution, on the other hand, is a little trickier. In this case, you can decide which record is overwritten based on timestamps. For example, does the older record get overwritten with the newer record?  Or vice-versa?  This method not only requires primary keys on every table, but it also requires every table to have a timestamp/date column that is updated each time a record is inserted or updated on the table.  Most homegrown applications can always be customized to include these requirements, but it's a little more difficult with 3rd party applications, and might even be impossible for large ERP type applications.  If your database has these features - whether it’s primary keys for host based resolution, or primary keys and timestamp columns for timestamp based resolution - then your application could be a great candidate for active-active replication.  But table structure is not the only requirement.  The other consideration applies when there is a conflict; i.e., do I need to perform any notification or track down the user that had their data overwritten?  In most cases, I don't think it's necessary, but if it is required, OGG can always create an exceptions table that contains all of the overwritten transactions so that people can be notified. It's a bit of extra work to implement this type of option, but if the business requires it, then it can be done. Unless someone is constantly monitoring this exception table or has an automated process in dealing with exceptions, there will be a delay in getting a response back to the end user. Ideally, when setting up active-active resolution we can include some simple procedural steps or configuration options that can reduce, or in some cases eliminate the potential for conflicts.  This makes the whole implementation that much easier and foolproof.  And I'll cover these in my next blog. 

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• Any way to pass parameters programmatically to an onclick function?

  - by RenderIn

  I have an onclick function which performs several tasks. In another javascript function I do not have access to the context variables needed to perform these tasks. To get around this I have been simply calling the onclick function directly. The problem I have now is that I'd like to perform a task after an Ajax action in the onclick completes. Is there any way for me to pass a function to the onclick method of a link? What would the onclick attribute look like? e.g. something like this: <a id="link3" href="javascript:void(0);" onclick="function(callback) { X(a); Y(b); Z(c, callback); };">click me</a> Clicking on this would pass "undefined" as the callback, while I could also call it explicitly like this: document.getElementById("link3").onclick(function() { alert("Completed all tasks"); } ); Is something like this possible? Basically I want to be able to pass an optional parameter to the onclick method, but if it's absent I want it to behave as if there were just procedural code in the onclick.

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• Can you review my Perl rewrite of Cucumber?

  - by Evgeny

  There is a team working on acceptance testing X11 GUI application in our company, and they created a monstrous acceptance testing framework that drives the GUI as well as running scenarios. The framework is written using Perl 5, and scenario files look more like very complex Perl programs (thousands of lines long with procedural-programming style) than acceptance tests. I recently learned Ruby's Cucumber, and generally have been using Ruby for quite a lot of time. But unfortunately I can't just shove Ruby to replace Perl because the people who are writing all of this don't know Ruby and it's quite certain that they wont want "this" kind of interruption. So to bring Ruby's Cucumber a bit closer to their work, I rewrote it using Perl 5. Unfortunately I am really not a Perl programmer, and would love to get a code review and to hear suggestions from people who both know Perl and Cucumber. Hi Perl/Cucumber StackOverflow users - please help me create this "open source" attempt to re-create Cucumber for Perl! I would love to hear your comments and will accept any acceptable help. The minimal source code is here: http://github.com/kesor/p5-cucumber Thank you for your attention. For those not familiar with cucumber - please take just one small moment to take a look at this one small little page: http://wiki.github.com/aslakhellesoy/cucumber

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• Efficient Context-Free Grammar parser, preferably Python-friendly

  - by Max Shawabkeh

  I am in need of parsing a small subset of English for one of my project, described as a context-free grammar with (1-level) feature structures (example) and I need to do it efficiently . Right now I'm using NLTK's parser which produces the right output but is very slow. For my grammar of ~450 fairly ambiguous non-lexicon rules and half a million lexical entries, parsing simple sentences can take anywhere from 2 to 30 seconds, depending it seems on the number of resulting trees. Lexical entries have little to no effect on performance. Another problem is that loading the (25MB) grammar+lexicon at the beginning can take up to a minute. From what I can find in literature, the running time of the algorithm used to parse such a grammar (Earley or CKY) should be linear to the size of the grammar and cubic to the size of the input token list. My experience with NLTK indicates that ambiguity is what hurts the performance most, not the absolute size of the grammar. So now I'm looking for a CFG parser to replace NLTK. I've been considering PLY but I can't tell whether it supports feature structures in CFGs, which are required in my case, and the examples I've seen seem to be doing a lot of procedural parsing rather than just specifying a grammar. Can anybody show me an example of PLY both supporting feature structs and using a declarative grammar? I'm also fine with any other parser that can do what I need efficiently. A Python interface is preferable but not absolutely necessary.

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• Experience migrating legacy Cobol/PL1 to Java

  - by MadMurf

  ORIGINAL Q: I'm wondering if anyone has had experience of migrating a large Cobol/PL1 codebase to Java? How automated was the process and how maintainable was the output? How did the move from transactional to OO work out? Any lessons learned along the way or resources/white papers that may be of benefit would be appreciated. EDIT 7/7: Certainly the NACA approach is interesting, the ability to continue making your BAU changes to the COBOL code right up to the point of releasing the JAVA version has merit for any organization. The argument for procedural Java in the same layout as the COBOL to give the coders a sense of comfort while familiarizing with the Java language is a valid argument for a large organisation with a large code base. As @Didier points out the $3mil annual saving gives scope for generous padding on any BAU changes going forward to refactor the code on an ongoing basis. As he puts it if you care about your people you find a way to keep them happy while gradually challenging them. The problem as I see it with the suggestion from @duffymo to Best to try and really understand the problem at its roots and re-express it as an object-oriented system is that if you have any BAU changes ongoing then during the LONG project lifetime of coding your new OO system you end up coding & testing changes on the double. That is a major benefit of the NACA approach. I've had some experience of migrating Client-Server applications to a web implementation and this was one of the major issues we encountered, constantly shifting requirements due to BAU changes. It made PM & scheduling a real challenge. Thanks to @hhafez who's experience is nicely put as "similar but slightly different" and has had a reasonably satisfactory experience of an automatic code migration from Ada to Java. Thanks @Didier for contributing, I'm still studying your approach and if I have any Q's I'll drop you a line.

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• How Does MVC Handle Missing Data Requirements

  - by Don Bakke

  I'm teaching myself MVC concepts in hopes of applying them to a non-OO/procedural development environment. I am pretty sure I understand simple View - Request - Controller - Request - Model - Response - Controller - Response - View flow. What I am struggling with is understanding more complex scenarios. For instance, let's say I have a shopping cart form with a button for 'Calculate Shipping'. Normally a click on this button will follow the above flow. But what if there is missing data, like the zip code? Should the View verify this first and alert the user before making a 'Calculate Shipping' request? Or should the request be made and the Model returns a notification that critical data is missing? If the latter, does the Controller instruct the View to alert the user? What if I wanted to prompt the user for the missing zip code (perhaps in a popup input display) and then automatically request the 'Calculate Shipping' method again? I suppose this gets into the question of how smart a View ought to be. It seems that MVC has evolved due to richer UI and automation (such as with data-binding) and this muddies the water from a purist MVC perspective. Any thoughts are greatly appreciated.

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