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• Death March

  - by Nick Harrison

  It is a horrible sight to watch a project fail. There are few things as bad. Watching a project fail regardless of the reason is almost like sitting in a room with a "Dementor" from Harry Potter. It will literally suck all of the life and joy out of the room. Nearly every project that I have seen fail has failed because of political challenges or management challenges. Sometimes there are technical challenges that bring a project to its knees, but usually projects fail for less technical reasons. Here a few observations about projects failing for political reasons. Both the client and the consultants have to be committed to seeing the project succeed. Put simply, you cannot solve a problem when the primary stake holders do not truly want it solved. This could come from a consultant being more interested in extended the engagement. It could come from a client being afraid of what will happen to them once the problem is solved. It could come from disenfranchised stake holders. Sometimes a project is beset on all sides. When you find yourself working on a project that has this kind of threat, do all that you can to constrain the disruptive influences of the bad apples. If their influence cannot be constrained, you truly have no choice but to move on to a new project. Tough choices have to be made to make a project successful. These choices will affect everyone involved in the project. These choices may involve users not getting a change request through that they want. Developers may not get to use the tools that they want. Everyone may have to put in more hours that they originally planned. Steps may be skipped. Compromises will be made, but if everyone stays committed to the end goal, you can still be successful. If individuals start feeling disgruntled or resentful of the compromises reached, the project can easily be derailed. When everyone is not working towards a common goal, it is like driving with one foot on the break and one foot on the accelerator. Not only will you not get to where you are planning, you will also damage the car and possibly the passengers as well.   It is important to always keep the end result in mind. Regardless of the development methodology being followed, the end goal is not comprehensive documentation. In all cases, it is working software. Comprehensive documentation is nice but useless if the software doesn't work.   You can never get so distracted by the next goal that you fail to meet the current goal. Most projects are ultimately marathons. This means that the pace must be sustainable. Regardless of the temptations, you cannot burn the team alive. Processes will fail. Technology will get outdated. Requirements will change, but your people will adapt and learn and grow. If everyone on the team from the most senior analyst to the most junior recruit trusts and respects each other, there is no challenge that they cannot overcome. When everyone involved faces challenges with the attitude "This is my project and I will not let it fail" "You are my teammate and I will not let you fail", you will in fact not fail. When you find a team that embraces this attitude, protect it at all cost. Edward Yourdon wrote a book called Death March. In it, he included a graph for categorizing Death March project types based on the Happiness of the Team and the Chances of Success.   Chances are we have all worked on Death March projects. We will all most likely work on more Death March projects in the future. To a certain extent, they seem to be inevitable, but they should never be suicide or ugly. Ideally, they can all be "Mission Impossible" where everyone works hard, has fun, and knows that there is good chance that they will succeed. If you are ever lucky enough to work on such a project, you will know that sense of pride that comes from the eventual success. You will recognize a profound bond with the team that you worked with. Chances are it will change your life or at least your outlook on life. If you have not already read this book, get a copy and study it closely. It will help you survive and make the most out of your next Death March project.

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• Some non-generic collections

  - by Simon Cooper

  Although the collections classes introduced in .NET 2, 3.5 and 4 cover most scenarios, there are still some .NET 1 collections that don't have generic counterparts. In this post, I'll be examining what they do, why you might use them, and some things you'll need to bear in mind when doing so. BitArray System.Collections.BitArray is conceptually the same as a List<bool>, but whereas List<bool> stores each boolean in a single byte (as that's what the backing bool[] does), BitArray uses a single bit to store each value, and uses various bitmasks to access each bit individually. This means that BitArray is eight times smaller than a List<bool>. Furthermore, BitArray has some useful functions for bitmasks, like And, Xor and Not, and it's not limited to 32 or 64 bits; a BitArray can hold as many bits as you need. However, it's not all roses and kittens. There are some fundamental limitations you have to bear in mind when using BitArray: It's a non-generic collection. The enumerator returns object (a boxed boolean), rather than an unboxed bool. This means that if you do this: foreach (bool b in bitArray) { ... } Every single boolean value will be boxed, then unboxed. And if you do this: foreach (var b in bitArray) { ... } you'll have to manually unbox b on every iteration, as it'll come out of the enumerator an object. Instead, you should manually iterate over the collection using a for loop: for (int i=0; i<bitArray.Length; i++) { bool b = bitArray[i]; ... } Following on from that, if you want to use BitArray in the context of an IEnumerable<bool>, ICollection<bool> or IList<bool>, you'll need to write a wrapper class, or use the Enumerable.Cast<bool> extension method (although Cast would box and unbox every value you get out of it). There is no Add or Remove method. You specify the number of bits you need in the constructor, and that's what you get. You can change the length yourself using the Length property setter though. It doesn't implement IList. Although not really important if you're writing a generic wrapper around it, it is something to bear in mind if you're using it with pre-generic code. However, if you use BitArray carefully, it can provide significant gains over a List<bool> for functionality and efficiency of space. OrderedDictionary System.Collections.Specialized.OrderedDictionary does exactly what you would expect - it's an IDictionary that maintains items in the order they are added. It does this by storing key/value pairs in a Hashtable (to get O(1) key lookup) and an ArrayList (to maintain the order). You can access values by key or index, and insert or remove items at a particular index. The enumerator returns items in index order. However, the Keys and Values properties return ICollection, not IList, as you might expect; CopyTo doesn't maintain the same ordering, as it copies from the backing Hashtable, not ArrayList; and any operations that insert or remove items from the middle of the collection are O(n), just like a normal list. In short; don't use this class. If you need some sort of ordered dictionary, it would be better to write your own generic dictionary combining a Dictionary<TKey, TValue> and List<KeyValuePair<TKey, TValue>> or List<TKey> for your specific situation. ListDictionary and HybridDictionary To look at why you might want to use ListDictionary or HybridDictionary, we need to examine the performance of these dictionaries compared to Hashtable and Dictionary<object, object>. For this test, I added n items to each collection, then randomly accessed n/2 items: So, what's going on here? Well, ListDictionary is implemented as a linked list of key/value pairs; all operations on the dictionary require an O(n) search through the list. However, for small n, the constant factor that big-o notation doesn't measure is much lower than the hashing overhead of Hashtable or Dictionary. HybridDictionary combines a Hashtable and ListDictionary; for small n, it uses a backing ListDictionary, but switches to a Hashtable when it gets to 9 items (you can see the point it switches from a ListDictionary to Hashtable in the graph). Apart from that, it's got very similar performance to Hashtable. So why would you want to use either of these? In short, you wouldn't. Any gain in performance by using ListDictionary over Dictionary<TKey, TValue> would be offset by the generic dictionary not having to cast or box the items you store, something the graphs above don't measure. Only if the performance of the dictionary is vital, the dictionary will hold less than 30 items, and you don't need type safety, would you use ListDictionary over the generic Dictionary. And even then, there's probably more useful performance gains you can make elsewhere.

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• Design Pattern for Complex Data Modeling

  - by Aaron Hayman

  I'm developing a program that has a SQL database as a backing store. As a very broad description, the program itself allows a user to generate records in any number of user-defined tables and make connections between them. As for specs: Any record generated must be able to be connected to any other record in any other user table (excluding itself...the record, not the table). These "connections" are directional, and the list of connections a record has is user ordered. Moreover, a record must "know" of connections made from it to others as well as connections made to it from others. The connections are kind of the point of this program, so there is a strong possibility that the number of connections made is very high, especially if the user is using the software as intended. A record's field can also include aggregate information from it's connections (like obtaining average, sum, etc) that must be updated on change from another record it's connected to. To conserve memory, only relevant information must be loaded at any one time (can't load the entire database in memory at load and go from there). I cannot assume the backing store is local. Right now it is, but eventually this program will include syncing to a remote db. Neither the user tables, connections or records are known at design time as they are user generated. I've spent a lot of time trying to figure out how to design the backing store and the object model to best fit these specs. In my first design attempt on this, I had one object managing all a table's records and connections. I attempted this first because it kept the memory footprint smaller (records and connections were simple dicts), but maintaining aggregate and link information between tables became....onerous (ie...a huge spaghettified mess). Tracing dependencies using this method almost became impossible. Instead, I've settled on a distributed graph model where each record and connection is 'aware' of what's around it by managing it own data and connections to other records. Doing this increases my memory footprint but also let me create a faulting system so connections/records aren't loaded into memory until they're needed. It's also much easier to code: trace dependencies, eliminate cycling recursive updates, etc. My biggest problem is storing/loading the connections. I'm not happy with any of my current solutions/ideas so I wanted to ask and see if anybody else has any ideas of how this should be structured. Connections are fairly simple. They contain: fromRecordID, fromTableID, fromRecordOrder, toRecordID, toTableID, toRecordOrder. Here's what I've come up with so far: Store all the connections in one big table. If I do this, either I load all connections at once (one big db call) or make a call every time a user table is loaded. The big issue here: the size of the connections table has the potential to be huge, and I'm afraid it would slow things down. Store in separate tables all the outgoing connections for each user table. This is probably the worst idea I've had. Now my connections are 'spread out' over multiple tables (one for each user table), which means I have to make a separate DB called to each table (or make a huge join) just to find all the incoming connections for a particular user table. I've avoided making "one big ass table", but I'm not sure the cost is worth it. Store in separate tables all outgoing AND incoming connections for each user table (using a flag to distinguish between incoming vs outgoing). This is the idea I'm leaning towards, but it will essentially double the total DB storage for all the connections (as each connection will be stored in two tables). It also means I have to make sure connection information is kept in sync in both places. This is obviously not ideal but it does mean that when I load a user table, I only need to load one 'connection' table and have all the information I need. This also presents a separate problem, that of connection object creation. Since each user table has a list of all connections, there are two opportunities for a connection object to be made. However, connections objects (designed to facilitate communication between records) should only be created once. This means I'll have to devise a common caching/factory object to make sure only one connection object is made per connection. Does anybody have any ideas of a better way to do this? Once I've committed to a particular design pattern I'm pretty much stuck with it, so I want to make sure I've come up with the best one possible.

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• ODI 12c - Aggregating Data

  - by David Allan

  This posting will look at the aggregation component that was introduced in ODI 12c. For many ETL tool users this shouldn't be a big surprise, its a little different than ODI 11g but for good reason. You can use this component for composing data with relational like operations such as sum, average and so forth. Also, Oracle SQL supports special functions called Analytic SQL functions, you can use a specially configured aggregation component or the expression component for these now in ODI 12c. In database systems an aggregate transformation is a transformation where the values of multiple rows are grouped together as input on certain criteria to form a single value of more significant meaning - that's exactly the purpose of the aggregate component. In the image below you can see the aggregate component in action within a mapping, for how this and a few other examples are built look at the ODI 12c Aggregation Viewlet here - the viewlet illustrates a simple aggregation being built and then some Oracle analytic SQL such as AVG(EMP.SAL) OVER (PARTITION BY EMP.DEPTNO) built using both the aggregate component and the expression component. In 11g you used to just write the aggregate expression directly on the target, this made life easy for some cases, but it wan't a very obvious gesture plus had other drawbacks with ordering of transformations (agg before join/lookup. after set and so forth) and supporting analytic SQL for example - there are a lot of postings from creative folks working around this in 11g - anything from customizing KMs, to bypassing aggregation analysis in the ODI code generator. The aggregate component has a few interesting aspects. 1. Firstly and foremost it defines the attributes projected from it - ODI automatically will perform the grouping all you do is define the aggregation expressions for those columns aggregated. In 12c you can control this automatic grouping behavior so that you get the code you desire, so you can indicate that an attribute should not be included in the group by, that's what I did in the analytic SQL example using the aggregate component. 2. The component has a few other properties of interest; it has a HAVING clause and a manual group by clause. The HAVING clause includes a predicate used to filter rows resulting from the GROUP BY clause. Because it acts on the results of the GROUP BY clause, aggregation functions can be used in the HAVING clause predicate, in 11g the filter was overloaded and used for both having clause and filter clause, this is no longer the case. If a filter is after an aggregate, it is after the aggregate (not sometimes after, sometimes having).  3. The manual group by clause let's you use special database grouping grammar if you need to. For example Oracle has a wealth of highly specialized grouping capabilities for data warehousing such as the CUBE function. If you want to use specialized functions like that you can manually define the code here. The example below shows the use of a manual group from an example in the Oracle database data warehousing guide where the SUM aggregate function is used along with the CUBE function in the group by clause. The SQL I am trying to generate looks like the following from the data warehousing guide; SELECT channel_desc, calendar_month_desc, countries.country_iso_code,       TO_CHAR(SUM(amount_sold), '9,999,999,999') SALES$ FROM sales, customers, times, channels, countries WHERE sales.time_id=times.time_id AND sales.cust_id=customers.cust_id AND   sales.channel_id= channels.channel_id  AND customers.country_id = countries.country_id  AND channels.channel_desc IN   ('Direct Sales', 'Internet') AND times.calendar_month_desc IN   ('2000-09', '2000-10') AND countries.country_iso_code IN ('GB', 'US') GROUP BY CUBE(channel_desc, calendar_month_desc, countries.country_iso_code); I can capture the source datastores, the filters and joins using ODI's dataset (or as a traditional flow) which enables us to incrementally design the mapping and the aggregate component for the sum and group by as follows; In the above mapping you can see the joins and filters declared in ODI's dataset, allowing you to capture the relationships of the datastores required in an entity-relationship style just like ODI 11g. The mix of ODI's declarative design and the common flow design provides for a familiar design experience. The example below illustrates flow design (basic arbitrary ordering) - a table load where only the employees who have maximum commission are loaded into a target. The maximum commission is retrieved from the bonus datastore and there is a look using employees as the driving table and only those with maximum commission projected. Hopefully this has given you a taster for some of the new capabilities provided by the aggregate component in ODI 12c. In summary, the actions should be much more consistent in behavior and more easily discoverable for users, the use of the components in a flow graph also supports arbitrary designs and the tool (rather than the interface designer) takes care of the realization using ODI's knowledge modules. Interested to know if a deep dive into each component is interesting for folks. Any thoughts? 

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• yield – Just yet another sexy c# keyword?

  - by George Mamaladze

  yield (see NSDN c# reference) operator came I guess with .NET 2.0 and I my feeling is that it’s not as wide used as it could (or should) be.   I am not going to talk here about necessarity and advantages of using iterator pattern when accessing custom sequences (just google it).   Let’s look at it from the clean code point of view. Let's see if it really helps us to keep our code understandable, reusable and testable.   Let’s say we want to iterate a tree and do something with it’s nodes, for instance calculate a sum of their values. So the most elegant way would be to build a recursive method performing a classic depth traversal returning the sum.           private int CalculateTreeSum(Node top)         {             int sumOfChildNodes = 0;             foreach (Node childNode in top.ChildNodes)             {                 sumOfChildNodes += CalculateTreeSum(childNode);             }             return top.Value + sumOfChildNodes;         }     “Do One Thing” Nevertheless it violates one of the most important rules “Do One Thing”. Our  method CalculateTreeSum does two things at the same time. It travels inside the tree and performs some computation – in this case calculates sum. Doing two things in one method is definitely a bad thing because of several reasons: ·          Understandability: Readability / refactoring ·          Reuseability: when overriding - no chance to override computation without copying iteration code and vice versa. ·          Testability: you are not able to test computation without constructing the tree and you are not able to test correctness of tree iteration.   I want to spend some more words on this last issue. How do you test the method CalculateTreeSum when it contains two in one: computation & iteration? The only chance is to construct a test tree and assert the result of the method call, in our case the sum against our expectation. And if the test fails you do not know wether was the computation algorithm wrong or was that the iteration? At the end to top it all off I tell you: according to Murphy’s Law the iteration will have a bug as well as the calculation. Both bugs in a combination will cause the sum to be accidentally exactly the same you expect and the test will PASS. J   Ok let’s use yield! That’s why it is generally a very good idea not to mix but isolate “things”. Ok let’s use yield!           private int CalculateTreeSumClean(Node top)         {             IEnumerable<Node> treeNodes = GetTreeNodes(top);             return CalculateSum(treeNodes);         }             private int CalculateSum(IEnumerable<Node> nodes)         {             int sumOfNodes = 0;             foreach (Node node in nodes)             {                 sumOfNodes += node.Value;             }             return sumOfNodes;         }           private IEnumerable<Node> GetTreeNodes(Node top)         {             yield return top;             foreach (Node childNode in top.ChildNodes)             {                 foreach (Node currentNode in GetTreeNodes(childNode))                 {                     yield return currentNode;                 }             }         }   Two methods does not know anything about each other. One contains calculation logic another jut the iteration logic. You can relpace the tree iteration algorithm from depth traversal to breath trevaersal or use stack or visitor pattern instead of recursion. This will not influence your calculation logic. And vice versa you can relace the sum with product or do whatever you want with node values, the calculateion algorithm is not aware of beeng working on some tree or graph.  How about not using yield? Now let’s ask the question – what if we do not have yield operator? The brief look at the generated code gives us an answer. The compiler generates a 150 lines long class to implement the iteration logic.       [CompilerGenerated]     private sealed class <GetTreeNodes>d__0 : IEnumerable<Node>, IEnumerable, IEnumerator<Node>, IEnumerator, IDisposable     {         ...        150 Lines of generated code        ...     }   Often we compromise code readability, cleanness, testability, etc. – to reduce number of classes, code lines, keystrokes and mouse clicks. This is the human nature - we are lazy. Knowing and using such a sexy construct like yield, allows us to be lazy, write very few lines of code and at the same time stay clean and do one thing in a method. That's why I generally welcome using staff like that.   Note: The above used recursive depth traversal algorithm is possibly the compact one but not the best one from the performance and memory utilization point of view. It was taken to emphasize on other primary aspects of this post.

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• Developing Schema Compare for Oracle (Part 5): Query Snapshots

  - by Simon Cooper

  If you've emailed us about a bug you've encountered with the EAP or beta versions of Schema Compare for Oracle, we probably asked you to send us a query snapshot of your databases. Here, I explain what a query snapshot is, and how it helps us fix your bug. Problem 1: Debugging users' bug reports When we started the Schema Compare project, we knew we were going to get problems with users' databases - configurations we hadn't considered, features that weren't installed, unicode issues, wierd dependencies... With SQL Compare, users are generally happy to send us a database backup that we can restore using a single RESTORE DATABASE command on our test servers and immediately reproduce the problem. Oracle, on the other hand, would be a lot more tricky. As Oracle generally has a 1-to-1 mapping between instances and databases, any databases users sent would have to be restored to their own instance. Furthermore, the number of steps required to get a properly working database, and the size of most oracle databases, made it infeasible to ask every customer who came across a bug during our beta program to send us their databases. We also knew that there would be lots of issues with data security that would make it hard to get backups. So we needed an easier way to be able to debug customers issues and sort out what strange schema data Oracle was returning. Problem 2: Test execution time Another issue we knew we would have to solve was the execution time of the tests we would produce for the Schema Compare engine. Our initial prototype showed that querying the data dictionary for schema information was going to be slow (at least 15 seconds per database), and this is generally proportional to the size of the database. If you're running thousands of tests on the same databases, each one registering separate schemas, not only would the tests would take hours and hours to run, but the test servers would be hammered senseless. The solution To solve these, we needed to be able to populate the schema of a database without actually connecting to it. Well, the IDataReader interface is the primary way we read data from an Oracle server. The data dictionary queries we use return their data in terms of simple strings and numbers, which we then process and reconstruct into an object model, and the results of these queries are identical for identical schemas. So, we can record the raw results of the queries once, and then replay these results to construct the same object model as many times as required without needing to actually connect to the original database. This is what query snapshots do. They are binary files containing the raw unprocessed data we get back from the oracle server for all the queries we run on the data dictionary to get schema information. The core of the query snapshot generation takes the results of the IDataReader we get from running queries on Oracle, and passes the row data to a BinaryWriter that writes it straight to a file. The query snapshot can then be replayed to create the same object model; when the results of a specific query is needed by the population code, we can simply read the binary data stored in the file on disk and present it through an IDataReader wrapper. This is far faster than querying the server over the network, and allows us to run tests in a reasonable time. They also allow us to easily debug a customers problem; using a simple snapshot generation program, users can generate a query snapshot that could be sent along with a bug report that we can immediately replay on our machines to let us debug the issue, rather than having to obtain database backups and restore databases to test systems. There are also far fewer problems with data security; query snapshots only contain schema information, which is generally less sensitive than table data. Query snapshots implementation However, actually implementing such a feature did have a couple of 'gotchas' to it. My second blog post detailed the development of the dependencies algorithm we use to ensure we get all the dependencies in the database, and that algorithm uses data from both databases to find all the needed objects - what database you're comparing to affects what objects get populated from both databases. We get information on these additional objects using an appropriate WHERE clause on all the population queries. So, in order to accurately replay the results of querying the live database, the query snapshot needs to be a snapshot of a comparison of two databases, not just populating a single database. Furthermore, although the code population queries (eg querying all_tab_cols to get column information) can simply be passed straight from the IDataReader to the BinaryWriter, we need to hook into and run the live dependencies algorithm while we're creating the snapshot to ensure we get the same WHERE clauses, and the same query results, as if we were populating straight from a live system. We also need to store the results of the dependencies queries themselves, as the resulting dependency graph is stored within the OracleDatabase object that is produced, and is later used to help order actions in synchronization scripts. This is significantly helped by the dependencies algorithm being a deterministic algorithm - given the same input, it will always return the same output. Therefore, when we're replaying a query snapshot, and processing dependency information, we simply have to return the results of the queries in the order we got them from the live database, rather than trying to calculate the contents of all_dependencies on the fly. Query snapshots are a significant feature in Schema Compare that really helps us to debug problems with the tool, as well as making our testers happier. Although not really user-visible, they are very useful to the development team to help us fix bugs in the product much faster than we otherwise would be able to.

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• Facebook Connect: Error when clicking the Facebook Connect button

  - by Garrett

  I am getting this error when I click on the facebook connect button: API Error Code: 100 API Error Description: Invalid parameter Error Message: next is not owned by the application. I am not too sure how to do this, but I've read all the documentation for facebook connect and came up with this: <?php date_default_timezone_set("America/Toronto"); define('FACEBOOK_APP_ID', '##################'); define('FACEBOOK_SECRET', 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXX'); function get_facebook_cookie($app_id, $application_secret) { if(!isset($_COOKIE['fbs_' . $app_id])) return null; $args = array(); parse_str(trim($_COOKIE['fbs_' . $app_id], '\\"'), $args); ksort($args); $payload = ''; foreach ($args as $key => $value) { if ($key != 'sig') { $payload .= $key . '=' . $value; } } if (md5($payload . $application_secret) != $args['sig']) { return null; } return $args; } $cookie = get_facebook_cookie(FACEBOOK_APP_ID, FACEBOOK_SECRET); ?> <html xmlns="http://www.w3.org/1999/xhtml" xmlns:fb="http://www.facebook.com/2008/fbml"> <head> <!-- JQUERY INCLUDE --> <script src="js/jquery-1.4.2.min.js" type="text/javascript"></script> <!-- FACEBOOK CONNECT INCLUDE --> <script src="http://static.ak.connect.facebook.com/js/api_lib/v0.4/FeatureLoader.js.php/en_US" type="text/javascript"></script> <script type="text/javascript"> <!-- $(document).load(function() { }); FB.init("XXXXXXXXXXXXXXXXXXXXXXx ", "xd_receiver.htm"); FB.Event.subscribe('auth.login', function(response) { window.location.reload(); }); function facebook_onlogin() { FB.getLoginStatus(function(response) { if (response.session) { // logged in and connected user, someone you know fb_login.hide(); } else { // no user session available, someone you dont know } }); } // --> </script> </head> <body> <div id="fb_login"> <fb:login-button onlogin="facebook_onlogin();" v="2">Log In with Facebook</fb:login-button> </div> <?php $user = json_decode(file_get_contents( 'https://graph.facebook.com/me?access_token=' . $cookie['access_token']))->id; ?> </body> </html> how on earth can i get this to work? thanks!

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• Core Data NSPredicate for relationships.

  - by Mugunth Kumar

  My object graph is simple. I've a feedentry object that stores info about RSS feeds and a relationship called Tag that links to "TagValues" object. Both the relation (to and inverse) are to-many. i.e, a feed can have multiple tags and a tag can be associated to multiple feeds. I referred to http://stackoverflow.com/questions/844162/how-to-do-core-data-queries-through-a-relationship and created a NSFetchRequest. But when fetch data, I get an exception stating, NSInvalidArgumentException unimplemented SQL generation for predicate What should I do? I'm a newbie to core data :( I know I've done something terribly wrong... Please help... Thanks -- NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; // Edit the entity name as appropriate. NSEntityDescription *entity = [NSEntityDescription entityForName:@"FeedEntry" inManagedObjectContext:managedObjectContext]; [fetchRequest setEntity:entity]; // Edit the sort key as appropriate. NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"authorname" ascending:NO]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; [fetchRequest setSortDescriptors:sortDescriptors]; NSEntityDescription *tagEntity = [NSEntityDescription entityForName:@"TagValues" inManagedObjectContext:self.managedObjectContext]; NSPredicate *tagPredicate = [NSPredicate predicateWithFormat:@"tagName LIKE[c] 'nyt'"]; NSFetchRequest *tagRequest = [[NSFetchRequest alloc] init]; [tagRequest setEntity:tagEntity]; [tagRequest setPredicate:tagPredicate]; NSError *error = nil; NSArray* predicates = [self.managedObjectContext executeFetchRequest:tagRequest error:&error]; TagValues *tv = (TagValues*) [predicates objectAtIndex:0]; NSLog(tv.tagName); // it is nyt here... NSPredicate *predicate = [NSPredicate predicateWithFormat:@"tag IN %@", predicates]; [fetchRequest setPredicate:predicate]; // Edit the section name key path and cache name if appropriate. // nil for section name key path means "no sections". NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:nil cacheName:@"Root"]; aFetchedResultsController.delegate = self; self.fetchedResultsController = aFetchedResultsController; --

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• Keeping the DI-container usage in the composition root in Silverlight and MVVM

  - by adrian hara

  It's not quite clear to me how I can design so I keep the reference to the DI-container in the composition root for a Silverlight + MVVM application. I have the following simple usage scenario: there's a main view (perhaps a list of items) and an action to open an edit view for one single item. So the main view has to create and show the edit view when the user takes the action (e.g. clicks some button). For this I have the following code: public interface IView { IViewModel ViewModel {get; set;} } Then, for each view that I need to be able to create I have an abstract factory, like so public interface ISomeViewFactory { IView CreateView(); } This factory is then declared a dependency of the "parent" view model, like so: public class SomeParentViewModel { public SomeParentViewModel(ISomeViewFactory viewFactory) { // store it } private void OnSomeUserAction() { IView view = viewFactory.CreateView(); dialogService.ShowDialog(view); } } So all is well until here, no DI-container in sight :). Now comes the implementation of ISomeViewFactory: public class SomeViewFactory : ISomeViewFactory { public IView CreateView() { IView view = new SomeView(); view.ViewModel = ???? } } The "????" part is my problem, because the view model for the view needs to be resolved from the DI-container so it gets its dependencies injected. What I don't know is how I can do this without having a dependency to the DI-container anywhere except the composition root. One possible solution would be to have either a dependency on the view model that gets injected into the factory, like so: public class SomeViewFactory : ISomeViewFactory { public SomeViewFactory(ISomeViewModel viewModel) { // store it } public IView CreateView() { IView view = new SomeView(); view.ViewModel = viewModel; } } While this works, it has the problem that since the whole object graph is wired up "statically" (i.e. the "parent" view model will get an instance of SomeViewFactory, which will get an instance of SomeViewModel, and these will live as long as the "parent" view model lives), the injected view model implementation is stateful and if the user opens the child view twice, the second time the view model will be the same instance and have the state from before. I guess I could work around this with an "Initialize" method or something similar, but it doesn't smell quite right. Another solution might be to wrap the DI-container and have the factories depend on the wrapper, but it'd still be a DI-container "in disguise" there :) Any thoughts on this are greatly appreciated. Also, please forgive any mistakes or rule-breaking, since this is my first post on stackoverflow :) Thanks! ps: my current solution is that the factories know about the DI-container, and it's only them and the composition root that have this dependency.

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• Using ASP.NET MVC, Linq To SQL, and StructureMap causing DataContext to cache data

  - by Dragn1821

  I'll start by telling my project setup: ASP.NET MVC 1.0 StructureMap 2.6.1 VB I've created a bootstrapper class shown here: Imports StructureMap Imports DCS.Data Imports DCS.Services Public Class BootStrapper Public Shared Sub ConfigureStructureMap() ObjectFactory.Initialize(AddressOf StructureMapRegistry) End Sub Private Shared Sub StructureMapRegistry(ByVal x As IInitializationExpression) x.AddRegistry(New MainRegistry()) x.AddRegistry(New DataRegistry()) x.AddRegistry(New ServiceRegistry()) x.Scan(AddressOf StructureMapScanner) End Sub Private Shared Sub StructureMapScanner(ByVal scanner As StructureMap.Graph.IAssemblyScanner) scanner.Assembly("DCS") scanner.Assembly("DCS.Data") scanner.Assembly("DCS.Services") scanner.WithDefaultConventions() End Sub End Class I've created a controller factory shown here: Imports System.Web.Mvc Imports StructureMap Public Class StructureMapControllerFactory Inherits DefaultControllerFactory Protected Overrides Function GetControllerInstance(ByVal controllerType As System.Type) As System.Web.Mvc.IController Return ObjectFactory.GetInstance(controllerType) End Function End Class I've modified the Global.asax.vb as shown here: ... Sub Application_Start() RegisterRoutes(RouteTable.Routes) 'StructureMap BootStrapper.ConfigureStructureMap() ControllerBuilder.Current.SetControllerFactory(New StructureMapControllerFactory()) End Sub ... I've added a Structure Map registry file to each of my three projects: DCS, DCS.Data, and DCS.Services. Here is the DCS.Data registry: Imports StructureMap.Configuration.DSL Public Class DataRegistry Inherits Registry Public Sub New() 'Data Connections. [For](Of DCSDataContext)() _ .HybridHttpOrThreadLocalScoped _ .Use(New DCSDataContext()) 'Repositories. [For](Of IShiftRepository)() _ .Use(Of ShiftRepository)() [For](Of IMachineRepository)() _ .Use(Of MachineRepository)() [For](Of IShiftSummaryRepository)() _ .Use(Of ShiftSummaryRepository)() [For](Of IOperatorRepository)() _ .Use(Of OperatorRepository)() [For](Of IShiftSummaryJobRepository)() _ .Use(Of ShiftSummaryJobRepository)() End Sub End Class Everything works great as far as loading the dependecies, but I'm having problems with the DCSDataContext class that was genereated by Linq2SQL Classes. I have a form that posts to a details page (/Summary/Details), which loads in some data from SQL. I then have a button that opens a dialog box in JQuery, which populates the dialog from a request to (/Operator/Modify). On the dialog box, the form has a combo box and an OK button that lets the user change the operator's name. Upon clicking OK, the form is posted to (/Operator/Modify) and sent through the service and repository layers of my program and updates the record in the database. Then, the RedirectToAction is called to send the user back to the details page (/Summary/Details) where there is a call to pull the data from SQL again, updating the details view. Everything works great, except the details view does not show the new operator that was selected. I can step through the code and see the DCSDataContext class being accessed to update the operator (which does actually change the database record), but when the DCSDataContext is accessed to reload the details objects, it pulls in the old value. I'm guessing that StructureMap is causing not only the DCSDataContext class but also the data to be cached? I have also tried adding the following to the Global.asax, but it just ends up crashing the program telling me the DCSDataContext has been disposed... Private Sub MvcApplication_EndRequest(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.EndRequest StructureMap.ObjectFactory.ReleaseAndDisposeAllHttpScopedObjects() End Sub Can someone please help?

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• XML: Process large data

  - by Atmocreations

  Hello What XML-parser do you recommend for the following purpose: The XML-file (formatted, containing whitespaces) is around 800 MB. It mostly contains three types of tag (let's call them n, w and r). They have an attribute called id which i'd have to search for, as fast as possible. Removing attributes I don't need could save around 30%, maybe a bit more. First part for optimizing the second part: Is there any good tool (command line linux and windows if possible) to easily remove unused attributes in certain tags? I know that XSLT could be used. Or are there any easy alternatives? Also, I could split it into three files, one for each tag to gain speed for later parsing... Speed is not too important for this preparation of the data, of course it would be nice when it took rather minutes than hours. Second part: Once I have the data prepared, be it shortened or not, I should be able to search for the ID-attribute I was mentioning, this being time-critical. Estimations using wc -l tell me that there are around 3M N-tags and around 418K W-tags. The latter ones can contain up to approximately 20 subtags each. W-Tags also contain some, but they would be stripped away. "All I have to do" is navigating between tags containing certain id-attributes. Some tags have references to other id's, therefore giving me a tree, maybe even a graph. The original data is big (as mentioned), but the resultset shouldn't be too big as I only have to pick out certain elements. Now the question: What XML parsing library should I use for this kind of processing? I would use Java 6 in a first instance, with having in mind to be porting it to BlackBerry. Might it be useful to just create a flat file indexing the id's and pointing to an offset in the file? Is it even necessary to do the optimizations mentioned in the upper part? Or are there parser known to be quite as fast with the original data? Little note: To test, I took the id being on the very last line on the file and searching for the id using grep. This took around a minute on a Core 2 Duo. What happens if the file grows even bigger, let's say 5 GB? I appreciate any notice or recommendation. Thank you all very much in advance and regards

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• directshow Renderstream fails with grayscale bitmaps

  - by Roey

  Hi all. I'm trying to create a directshow graph to playback a video composed of 8bit grayscale bitmaps. (using directshow.net.) I'm using a source filter and the vmr9 renderer. The source filter's output pin is defined using the following code : bmi.Size = Marshal.SizeOf(typeof(BitmapInfoHeader)); bmi.Width = width; bmi.Height = height;; bmi.Planes = 1; bmi.BitCount = (short)bitcount; bmi.Compression = 0; bmi.ImageSize = Math.Abs(bmi.Height) * bmi.Width * bmi.BitCount / 8; bmi.ClrUsed = bmi.BitCount <= 8 ? 256 : 0; bmi.ClrImportant = 0; //bmi.XPelsPerMeter = 0; //bmi.YPelsPerMeter = 0; bool isGrayScale = bmi.BitCount <= 8 ? true : false; int formatSize = Marshal.SizeOf(typeof(BitmapInfoHeader)); if (isGrayScale == true) { MessageWriter.Log.WriteTrace("Playback is grayscale."); /// Color table holds an array of 256 RGBQAD values /// Those are relevant only for grayscale bitmaps formatSize += Marshal.SizeOf(typeof(RGBQUAD)) * bmi.ClrUsed; } IntPtr ptr = Marshal.AllocHGlobal(formatSize); Marshal.StructureToPtr(bmi, ptr, false); if (isGrayScale == true) { /// Adjust the pointer to the beginning of the /// ColorTable address and create the grayscale color table IntPtr ptrNext = (IntPtr)((int)ptr + Marshal.SizeOf(typeof(BitmapInfoHeader))); for (int i = 0; i < bmi.ClrUsed; i++) { RGBQUAD rgbCell = new RGBQUAD(); rgbCell.rgbBlue = rgbCell.rgbGreen = rgbCell.rgbRed = (byte)i; rgbCell.rgbReserved = 0; Marshal.StructureToPtr(rgbCell, ptrNext, false); ptrNext = (IntPtr)((int)ptrNext + Marshal.SizeOf(typeof(RGBQUAD))); } } This causes Renderstream to return "No combination of intermediate filters could be found to make the connection." Please help! Thanks.

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• IronPython and Nodebox in C#

  - by proxylittle

  My plan: I'm trying to setup my C# project to communicate with Nodebox to call a certain function which populates a graph and draws it in a new window. Current situation: [fixed... see Update2] I have already included all python-modules needed, but im still getting a Library 'GL' not found it seems that the pyglet module needs a reference to GL/gl.h, but can't find it due to IronPython behaviour. Requirement: The project needs to stay as small as possible without installing new packages. Thats why i have copied all my modules into the project-folder and would like to keep it that or a similar way. My question: Is there a certain workaround for my problem or a fix for the library-folder missmatch. Have read some articles about Tao-Opengl and OpenTK but can't find a good solution. Update1: Updated my sourcecode with a small pyglet window-rendering example. Problem is in pyglet and referenced c-Objects. How do i include them in my c# project to be called? No idea so far... experimenting alittle now. Keeping you updated. SampleCode C#: ScriptRuntimeSetup setup = Python.CreateRuntimeSetup(null); ScriptRuntime runtime = new ScriptRuntime(setup); ScriptEngine engine = Python.GetEngine(runtime); ScriptSource source = engine.CreateScriptSourceFromFile("test.py"); ScriptScope scope = engine.CreateScope(); source.Execute(scope); SampleCode Python (test.py): from nodebox.graphics import * from nodebox.graphics.physics import Vector, Boid, Flock, Obstacle flock = Flock(50, x=-50, y=-50, width=700, height=400) flock.sight(80) def draw(canvas): canvas.clear() flock.update(separation=0.4, cohesion=0.6, alignment=0.1, teleport=True) for boid in flock: push() translate(boid.x, boid.y) scale(0.5 + boid.depth) rotate(boid.heading) arrow(0, 0, 15) pop() canvas.size = 600, 300 def main(canvas): canvas.run(draw) Update2: Line 139 [pyglet/lib.py] sys.platform is not win32... there was the error. Fixed it by just using the line: from pyglet.gl.lib_wgl import link_GL, link_GLU, link_WGL Now the following Error: 'module' object has no attribute '_getframe' Kind of a pain to fix it. Updating with results... Update3: Fixed by adding following line right after first line in C#-Code: setup.Options["Frames"] = true; Current Problem: No module named unicodedata, but in Python26/DLLs is only a *.pyd file`. So.. how do i implement it now?!

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• trying to build Boost MPI, but the lib files are not created. What's going on?

  - by unknownthreat

  I am trying to run a program with Boost MPI, but the thing is I don't have the .lib. So I try to create one by following the instruction at http://www.boost.org/doc/libs/1_43_0/doc/html/mpi/getting_started.html#mpi.config The instruction says "For many users using LAM/MPI, MPICH, or OpenMPI, configuration is almost automatic", I got myself OpenMPI in C:\, but I didn't do anything more with it. Do we need to do anything with it? Beside that, another statement from the instruction: "If you don't already have a file user-config.jam in your home directory, copy tools/build/v2/user-config.jam there." Well, I simply do what it says. I got myself "user-config.jam" in C:\boost_1_43_0 along with "using mpi ;" into the file. Next, this is what I've done: bjam --with-mpi C:\boost_1_43_0>bjam --with-mpi WARNING: No python installation configured and autoconfiguration failed. See http://www.boost.org/libs/python/doc/building.html for configuration instructions or pass --without-python to suppress this message and silently skip all Boost.Python targets Building the Boost C++ Libraries. warning: skipping optional Message Passing Interface (MPI) library. note: to enable MPI support, add "using mpi ;" to user-config.jam. note: to suppress this message, pass "--without-mpi" to bjam. note: otherwise, you can safely ignore this message. warning: Unable to construct ./stage-unversioned warning: Unable to construct ./stage-unversioned Component configuration: - date_time : not building - filesystem : not building - graph : not building - graph_parallel : not building - iostreams : not building - math : not building - mpi : building - program_options : not building - python : not building - random : not building - regex : not building - serialization : not building - signals : not building - system : not building - test : not building - thread : not building - wave : not building ...found 1 target... The Boost C++ Libraries were successfully built! The following directory should be added to compiler include paths: C:\boost_1_43_0 The following directory should be added to linker library paths: C:\boost_1_43_0\stage\lib C:\boost_1_43_0> I see that there are many libs in C:\boost_1_43_0\stage\lib, but I see no trace of libboost_mpi-vc100-mt-1_43.lib or libboost_mpi-vc100-mt-gd-1_43.lib at all. These are the libraries required for linking in mpi applications. What could possibly gone wrong when libraries are not being built?

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• How to optimize Core Data query for full text search

  - by dk

  Can I optimize a Core Data query when searching for matching words in a text? (This question also pertains to the wisdom of custom SQL versus Core Data on an iPhone.) I'm working on a new (iPhone) app that is a handheld reference tool for a scientific database. The main interface is a standard searchable table view and I want as-you-type response as the user types new words. Words matches must be prefixes of words in the text. The text is composed of 100,000s of words. In my prototype I coded SQL directly. I created a separate "words" table containing every word in the text fields of the main entity. I indexed words and performed searches along the lines of SELECT id, * FROM textTable JOIN (SELECT DISTINCT textTableId FROM words WHERE word BETWEEN 'foo' AND 'fooz' ) ON id=textTableId LIMIT 50 This runs very fast. Using an IN would probably work just as well, i.e. SELECT * FROM textTable WHERE id IN (SELECT textTableId FROM words WHERE word BETWEEN 'foo' AND 'fooz' ) LIMIT 50 The LIMIT is crucial and allows me to display results quickly. I notify the user that there are too many to display if the limit is reached. This is kludgy. I've spent the last several days pondering the advantages of moving to Core Data, but I worry about the lack of control in the schema, indexing, and querying for an important query. Theoretically an NSPredicate of textField MATCHES '.*\bfoo.*' would just work, but I'm sure it will be slow. This sort of text search seems so common that I wonder what is the usual attack? Would you create a words entity as I did above and use a predicate of "word BEGINSWITH 'foo'"? Will that work as fast as my prototype? Will Core Data automatically create the right indexes? I can't find any explicit means of advising the persistent store about indexes. I see some nice advantages of Core Data in my iPhone app. The faulting and other memory considerations allow for efficient database retrievals for tableview queries without setting arbitrary limits. The object graph management allows me to easily traverse entities without writing lots of SQL. Migration features will be nice in the future. On the other hand, in a limited resource environment (iPhone) I worry that an automatically generated database will be bloated with metadata, unnecessary inverse relationships, inefficient attribute datatypes, etc. Should I dive in or proceed with caution?

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• Ray-Box Intersection during Scene traversal with matrix transforms

  - by Myx

  Hello: There are a few ways that I'm testing my ray-box intersections: Using the ComputeIntersectionBox(...) method, that takes a ray and a box as arguments and computes the closest intersection of the ray and the box. This method works by forming a plane with each of the faces of the box and finding an intersection with each of the planes. Once an intersection is found, a check is made whether or not the point is on the surface of the box by checking that the intersection point is between the corner points. When I look at rays after running this algorithm on two different boxes, I obtain the correct intersections. Using ComputeIntersectionScene(...) method without using the matrix transformations on a scene that has two spheres, a dodecahedron (a triangular mesh), and two boxes. ComputeIntersectionScene(...) recursively traverses all of the nodes of the scene graph and computes the closest intersection with the given ray. This test in particular does not apply any transformations that parent nodes may have that also need to be applied to their children. With this test, I also obtain the correct intersections. Using ComputeIntersectionScene(...) method WITH the matrix transformations. This test works like the one above except that before finding an intersection between the ray and a node in the scene, the ray is transformed into the node's coordinate frame using the inverse of the node's transformation matrix and after the intersection has been computed, this intersection is transformed back into the world coordinates by applying the transformation matrix to the intersection point. When testing with the third method on the same scene file as described in 2, testing with 4 rays (thus one ray intersects the one sphere, one ray the the other sphere, one ray one box, and one ray the other box), only the two spheres get intersected and the two boxes do not get intersections. When I debug looking into my ComputeIntersectionBox(...) method, it actually tells me that the ray intersects every plane on the box but each intersection point does not lie on the box. This seems to be strange behavior, since when using test 2 without transformations, I obtain the correct box intersections (thus, I believe my ray-box intersection to be correct) and when using test 3 WITH transformations, I obtain the correct sphere intersections (thus, I believe my transformed ray should be OK). Any suggestions where I could be going wrong? Thank you in advance.

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• Creating thousands of records in Rails

  - by willCosgrove

  Let me set the stage: My application deals with gift cards. When we create cards they have to have a unique string that the user can use to redeem it with. So when someone orders our gift cards, like a retailer, we need to make a lot of new card objects and store them in the DB. With that in mind, I'm trying to see how quickly I can have my application generate 100,000 Cards. Database expert, I am not, so I need someone to explain this little phenomena: When I create 1000 Cards, it takes 5 seconds. When I create 100,000 cards it should take 500 seconds right? Now I know what you're wanting to see, the card creation method I'm using, because the first assumption would be that it's getting slower because it's checking the uniqueness of a bunch of cards, more as it goes along. But I can show you my rake task desc "Creates cards for a retailer" task :order_cards, [:number_of_cards, :value, :retailer_name] => :environment do |t, args| t = Time.now puts "Searching for retailer" @retailer = Retailer.find_by_name(args[:retailer_name]) puts "Retailer found" puts "Generating codes" value = args[:value].to_i number_of_cards = args[:number_of_cards].to_i codes = [] top_off_codes(codes, number_of_cards) while codes != codes.uniq codes.uniq! top_off_codes(codes, number_of_cards) end stored_codes = Card.all.collect do |c| c.code end while codes != (codes - stored_codes) codes -= stored_codes top_off_codes(codes, number_of_cards) end puts "Codes are unique and generated" puts "Creating bundle" @bundle = @retailer.bundles.create!(:value => value) puts "Bundle created" puts "Creating cards" @bundle.transaction do codes.each do |code| @bundle.cards.create!(:code => code) end end puts "Cards generated in #{Time.now - t}s" end def top_off_codes(codes, intended_number) (intended_number - codes.size).times do codes << ReadableRandom.get(CODE_LENGTH) end end I'm using a gem called readable_random for the unique code. So if you read through all of that code, you'll see that it does all of it's uniqueness testing before it ever starts creating cards. It also writes status updates to the screen while it's running, and it always sits for a while at creating. Meanwhile it flies through the uniqueness tests. So my question to the stackoverflow community is: Why is my database slowing down as I add more cards? Why is this not a linear function in regards to time per card? I'm sure the answer is simple and I'm just a moron who knows nothing about data storage. And if anyone has any suggestions, how would you optimize this method, and how fast do you think you could get it to create 100,000 cards? (When I plotted out my times on a graph and did a quick curve fit to get my line formula, I calculated how long it would take to create 100,000 cards with my current code and it says 5.5 hours. That maybe completely wrong, I'm not sure. But if it stays on the line I curve fitted, it would be right around there.)

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• Determining what frequencies correspond to the x axis in aurioTouch sample application

  - by eagle

  I'm looking at the aurioTouch sample application for the iPhone SDK. It has a basic spectrum analyzer implemented when you choose the "FFT" option. One of the things the app is lacking is X axis labels (i.e. the frequency labels). In the aurioTouchAppDelegate.mm file, in the function - (void)drawOscilloscope at line 652, it has the following code: if (displayMode == aurioTouchDisplayModeOscilloscopeFFT) { if (fftBufferManager->HasNewAudioData()) { if (fftBufferManager->ComputeFFT(l_fftData)) [self setFFTData:l_fftData length:fftBufferManager->GetNumberFrames() / 2]; else hasNewFFTData = NO; } if (hasNewFFTData) { int y, maxY; maxY = drawBufferLen; for (y=0; y<maxY; y++) { CGFloat yFract = (CGFloat)y / (CGFloat)(maxY - 1); CGFloat fftIdx = yFract * ((CGFloat)fftLength); double fftIdx_i, fftIdx_f; fftIdx_f = modf(fftIdx, &fftIdx_i); SInt8 fft_l, fft_r; CGFloat fft_l_fl, fft_r_fl; CGFloat interpVal; fft_l = (fftData[(int)fftIdx_i] & 0xFF000000) >> 24; fft_r = (fftData[(int)fftIdx_i + 1] & 0xFF000000) >> 24; fft_l_fl = (CGFloat)(fft_l + 80) / 64.; fft_r_fl = (CGFloat)(fft_r + 80) / 64.; interpVal = fft_l_fl * (1. - fftIdx_f) + fft_r_fl * fftIdx_f; interpVal = CLAMP(0., interpVal, 1.); drawBuffers[0][y] = (interpVal * 120); } cycleOscilloscopeLines(); } } From my understanding, this part of the code is what is used to decide which magnitude to draw for each frequency in the UI. My question is how can I determine what frequency each iteration (or y value) represents inside the for loop. For example, if I want to know what the magnitude is for 6kHz, I'm thinking of adding a line similar to the following: if (yValueRepresentskHz(y, 6)) NSLog(@"The magnitude for 6kHz is %f", (interpVal * 120)); Please note that although they chose to use the variable name y, from what I understand, it actually represents the x-axis in the visual graph of the spectrum analyzer, and the value of the drawBuffers[0][y] represents the y-axis.

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• Rush Hour - Solving the game

  - by Rubys

  Rush Hour if you're not familiar with it, the game consists of a collection of cars of varying sizes, set either horizontally or vertically, on a NxM grid that has a single exit. Each car can move forward/backward in the directions it's set in, as long as another car is not blocking it. You can never change the direction of a car. There is one special car, usually it's the red one. It's set in the same row that the exit is in, and the objective of the game is to find a series of moves (a move - moving a car N steps back or forward) that will allow the red car to drive out of the maze. I've been trying to think how to solve this problem computationally, and I can really not think of any good solution. I came up with a few: Backtracking. This is pretty simple - Recursion and some more recursion until you find the answer. However, each car can be moved a few different ways, and in each game state a few cars can be moved, and the resulting game tree will be HUGE. Some sort of constraint algorithm that will take into account what needs to be moved, and work recursively somehow. This is a very rough idea, but it is an idea. Graphs? Model the game states as a graph and apply some sort of variation on a coloring algorithm, to resolve dependencies? Again, this is a very rough idea. A friend suggested genetic algorithms. This is sort of possible but not easily. I can't think of a good way to make an evaluation function, and without that we've got nothing. So the question is - How to create a program that takes a grid and the vehicle layout, and outputs a series of steps needed to get the red car out? Sub-issues: Finding some solution. Finding an optimal solution (minimal number of moves) Evaluating how good a current state is Example: How can you move the cars in this setting, so that the red car can "exit" the maze through the exit on the right?

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• JPopupMenu returning a null?

  - by Zenzen

  Ok so I'm working on an Eclipse plugin based on the JGraph example. The problem is I can't really get the "save" method to work, here's how the program works in short: - I have a DiagramEditor class with an init() method, where I create a GraphEditor object and call the createFrame() methord of that object. - GraphEditor extends the BasicGraphEditor (which extends JPanel), the createFrame() method returns a JFrame and has a line "frame.setJMenuBar(menuBar)" - the "menuBar" is an object variable, which is initialized in the BasicGraphEditor. Till here everything is cool, the problem is with the action listener which is supposed to save a file. To get the graph I need to get the GraphEditor component, so I do a Component component = (Component) e.getSource() whitch is the ActionEvent passed to that action listener and at that stage is the JMenuItem "save", then I get the parent which is the JPopupMenu, then I want to get that JPopupMenu's parent which should be the GraphEdiotor, but instead I get a null. Any idea why? Here's some source code: DiagramEditor.java: @Override public void init(IEditorSite site, IEditorInput input) throws PartInitException { setSite(site); setInput(input); this.diagram = ((DiagramEditorInput)input).getDiagram(); setPartName(this.diagram.getName()); gEditor = new GraphEditor(); gEditor.createFrame().setVisible(true); } BasicGraphEditor.java: public JFrame createFrame() { JFrame frame = new JFrame(); frame.getContentPane().add(this); frame.setJMenuBar(menuBar); //frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setSize(870, 640); return frame; } In the constructor: menuBar = new JMenuBar(); menu = new JMenu("File"); menu.setMnemonic(KeyEvent.VK_F); menuBar.add(menu); JMenuItem openMenuItem = new JMenuItem("Open", KeyEvent.VK_O); // ADD FILE OPENING //openMenuItem.addActionListener(menuListener); menu.add(openMenuItem); JMenuItem saveMenuItem = new JMenuItem("Save", new ImageIcon("/images/save.gif")); saveMenuItem.setMnemonic(KeyEvent.VK_S); saveMenuItem.addActionListener( new SaveAction(false) ); menu.add(saveMenuItem); // menu.add(new SaveAction(false)); JMenuItem saveMenuItemAs = new JMenuItem("SaveAs", new ImageIcon("/images/saveas.gif")); //saveMenuItemAs.setMnemonic(KeyEvent.VK_S); saveMenuItemAs.addActionListener( new SaveAction(true) ); menu.add(saveMenuItemAs); //menu.add(new SaveAction(true)); JMenuItem closeMenuItem = new JMenuItem("Close", KeyEvent.VK_C); closeMenuItem.addActionListener( new ActionListener() { public void actionPerformed(ActionEvent e) { System.exit(0); } } ); menu.add(closeMenuItem);

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• Import csv data (SDK iphone)

  - by Ni

  I am new to cocoa. I have been working on these stuff for a few days. For the following code, i can read all the data in the string, and successfully get the data for plot. NSMutableArray *contentArray = [NSMutableArray array]; NSString *filePath = @"995,995,995,995,995,995,995,995,1000,997,995,994,992,993,992,989,988,987,990,993,989"; NSArray *myText = [filePath componentsSeparatedByString:@","]; NSInteger idx; for (idx = 0; idx < myText.count; idx++) { NSString *data =[myText objectAtIndex:idx]; NSLog(@"%@", data); id x = [NSNumber numberWithFloat:0+idx*0.002777778]; id y = [NSDecimalNumber decimalNumberWithString:data]; [contentArray addObject: [NSMutableDictionary dictionaryWithObjectsAndKeys:x, @"x", y, @"y", nil]]; } self.dataForPlot = contentArray; then, i try to load the data from csv file. the data in Data.csv file has the same value and the same format as 995,995,995,995,995,995,995,995,1000,997,995,994,992,993,992,989,988,987,990,993,989. I run the code, it is supposed to give the same graph output. however, it seems that the data is not loaded from csv file successfully. i can not figure out what's wrong with my code. NSMutableArray *contentArray = [NSMutableArray array]; NSString *filePath = [[NSBundle mainBundle] pathForResource:@"Data" ofType:@"csv"]; NSString *Data = [NSString stringWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error:nil ]; if (Data) { NSArray *myText = [Data componentsSeparatedByString:@","]; NSInteger idx; for (idx = 0; idx < myText.count; idx++) { NSString *data =[myText objectAtIndex:idx]; NSLog(@"%@", data); id x = [NSNumber numberWithFloat:0+idx*0.002777778]; id y = [NSDecimalNumber decimalNumberWithString:data]; [contentArray addObject: [NSMutableDictionary dictionaryWithObjectsAndKeys:x, @"x", y, @"y",nil]]; } self.dataForPlot = contentArray; } The only difference is NSString *filePath = [[NSBundle mainBundle] pathForResource:@"Data" ofType:@"csv"]; NSString *Data = [NSString stringWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error:nil ]; if (data){ } did i do anything wrong here?? Thanks for your help!!!!

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• JPopupMenu getParent() returning a null?

  - by Zenzen

  Ok so I'm working on an Eclipse plugin based on the JGraph example. The problem is I can't really get the "save" method to work, here's how the program works in short: - I have a DiagramEditor class with an init() method, where I create a GraphEditor object and call the createFrame() methord of that object. - GraphEditor extends the BasicGraphEditor (which extends JPanel), the createFrame() method returns a JFrame and has a line "frame.setJMenuBar(menuBar)" - the "menuBar" is an object variable, which is initialized in the BasicGraphEditor. Till here everything is cool, the problem is with the action listener which is supposed to save a file. To get the graph I need to get the GraphEditor component, so I do a Component component = (Component) e.getSource() whitch is the ActionEvent passed to that action listener and at that stage is the JMenuItem "save", then I get the parent which is the JPopupMenu, then I want to get that JPopupMenu's parent which should be the GraphEdiotor, but instead I get a null. Any idea why? Here's some source code: DiagramEditor.java: @Override public void init(IEditorSite site, IEditorInput input) throws PartInitException { setSite(site); setInput(input); this.diagram = ((DiagramEditorInput)input).getDiagram(); setPartName(this.diagram.getName()); gEditor = new GraphEditor(); gEditor.createFrame().setVisible(true); } BasicGraphEditor.java: public JFrame createFrame() { JFrame frame = new JFrame(); frame.getContentPane().add(this); frame.setJMenuBar(menuBar); //frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setSize(870, 640); return frame; } In the constructor: menuBar = new JMenuBar(); menu = new JMenu("File"); menu.setMnemonic(KeyEvent.VK_F); menuBar.add(menu); JMenuItem openMenuItem = new JMenuItem("Open", KeyEvent.VK_O); // ADD FILE OPENING //openMenuItem.addActionListener(menuListener); menu.add(openMenuItem); JMenuItem saveMenuItem = new JMenuItem("Save", new ImageIcon("/images/save.gif")); saveMenuItem.setMnemonic(KeyEvent.VK_S); saveMenuItem.addActionListener( new SaveAction(false) ); menu.add(saveMenuItem); // menu.add(new SaveAction(false)); JMenuItem saveMenuItemAs = new JMenuItem("SaveAs", new ImageIcon("/images/saveas.gif")); //saveMenuItemAs.setMnemonic(KeyEvent.VK_S); saveMenuItemAs.addActionListener( new SaveAction(true) ); menu.add(saveMenuItemAs); //menu.add(new SaveAction(true)); JMenuItem closeMenuItem = new JMenuItem("Close", KeyEvent.VK_C); closeMenuItem.addActionListener( new ActionListener() { public void actionPerformed(ActionEvent e) { System.exit(0); } } ); menu.add(closeMenuItem);

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• Constructor Injection and when to use a Service Locator

  - by Simon

  I'm struggling to understand parts of StructureMap's usage. In particular, in the documentation a statement is made regarding a common anti-pattern, the use of StructureMap as a Service Locator only instead of constructor injection (code samples straight from Structuremap documentation): public ShippingScreenPresenter() { _service = ObjectFactory.GetInstance<IShippingService>(); _repository = ObjectFactory.GetInstance<IRepository>(); } instead of: public ShippingScreenPresenter(IShippingService service, IRepository repository) { _service = service; _repository = repository; } This is fine for a very short object graph, but when dealing with objects many levels deep, does this imply that you should pass down all the dependencies required by the deeper objects right from the top? Surely this breaks encapsulation and exposes too much information about the implementation of deeper objects. Let's say I'm using the Active Record pattern, so my record needs access to a data repository to be able to save and load itself. If this record is loaded inside an object, does that object call ObjectFactory.CreateInstance() and pass it into the active record's constructor? What if that object is inside another object. Does it take the IRepository in as its own parameter from further up? That would expose to the parent object the fact that we're access the data repository at this point, something the outer object probably shouldn't know. public class OuterClass { public OuterClass(IRepository repository) { // Why should I know that ThingThatNeedsRecord needs a repository? // that smells like exposed implementation to me, especially since // ThingThatNeedsRecord doesn't use the repo itself, but passes it // to the record. // Also where do I create repository? Have to instantiate it somewhere // up the chain of objects ThingThatNeedsRecord thing = new ThingThatNeedsRecord(repository); thing.GetAnswer("question"); } } public class ThingThatNeedsRecord { public ThingThatNeedsRecord(IRepository repository) { this.repository = repository; } public string GetAnswer(string someParam) { // create activeRecord(s) and process, returning some result // part of which contains: ActiveRecord record = new ActiveRecord(repository, key); } private IRepository repository; } public class ActiveRecord { public ActiveRecord(IRepository repository) { this.repository = repository; } public ActiveRecord(IRepository repository, int primaryKey); { this.repositry = repository; Load(primaryKey); } public void Save(); private void Load(int primaryKey) { this.primaryKey = primaryKey; // access the database via the repository and set someData } private IRepository repository; private int primaryKey; private string someData; } Any thoughts would be appreciated. Simon

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• Using MySQL to generate daily sales reports with filled gaps, grouped by currency

  - by Shane O'Grady

  I'm trying to create what I think is a relatively basic report for an online store, using MySQL 5.1.45 The store can receive payment in multiple currencies. I have created some sample tables with data and am trying to generate a straightforward tabular result set grouped by date and currency so that I can graph these figures. I want to see each currency that is available per date, with a 0 in the result if there were no sales in that currency for that day. If I can get that to work I want to do the same but also grouped by product id. In the sample data I have provided there are only 3 currencies and 2 product ids, but in practice there can be any number of each. I can correctly group by date, but then when I add a grouping by currency my query does not return what I want. I based my work off this article. My reporting query, grouped only by date: SELECT calendar.datefield AS date, IFNULL(SUM(orders.order_value),0) AS total_value FROM orders RIGHT JOIN calendar ON (DATE(orders.order_date) = calendar.datefield) WHERE (calendar.datefield BETWEEN (SELECT MIN(DATE(order_date)) FROM orders) AND (SELECT MAX(DATE(order_date)) FROM orders)) GROUP BY date Now grouped by date and currency: SELECT calendar.datefield AS date, orders.currency_id, IFNULL(SUM(orders.order_value),0) AS total_value FROM orders RIGHT JOIN calendar ON (DATE(orders.order_date) = calendar.datefield) WHERE (calendar.datefield BETWEEN (SELECT MIN(DATE(order_date)) FROM orders) AND (SELECT MAX(DATE(order_date)) FROM orders)) GROUP BY date, orders.currency_id The results I am getting (grouped by date and currency): +------------+-------------+-------------+ | date | currency_id | total_value | +------------+-------------+-------------+ | 2009-08-15 | 3 | 81.94 | | 2009-08-15 | 45 | 25.00 | | 2009-08-15 | 49 | 122.60 | | 2009-08-16 | NULL | 0.00 | | 2009-08-17 | 45 | 25.00 | | 2009-08-17 | 49 | 122.60 | | 2009-08-18 | 3 | 81.94 | | 2009-08-18 | 49 | 245.20 | +------------+-------------+-------------+ The results I want: +------------+-------------+-------------+ | date | currency_id | total_value | +------------+-------------+-------------+ | 2009-08-15 | 3 | 81.94 | | 2009-08-15 | 45 | 25.00 | | 2009-08-15 | 49 | 122.60 | | 2009-08-16 | 3 | 0.00 | | 2009-08-16 | 45 | 0.00 | | 2009-08-16 | 49 | 0.00 | | 2009-08-17 | 3 | 0.00 | | 2009-08-17 | 45 | 25.00 | | 2009-08-17 | 49 | 122.60 | | 2009-08-18 | 3 | 81.94 | | 2009-08-18 | 45 | 0.00 | | 2009-08-18 | 49 | 245.20 | +------------+-------------+-------------+ The schema and data I am using in my tests: CREATE TABLE orders ( id INT PRIMARY KEY AUTO_INCREMENT, order_date DATETIME, order_id INT, product_id INT, currency_id INT, order_value DECIMAL(9,2), customer_id INT ); INSERT INTO orders (order_date, order_id, product_id, currency_id, order_value, customer_id) VALUES ('2009-08-15 10:20:20', '123', '1', '45', '12.50', '322'), ('2009-08-15 12:30:20', '124', '1', '49', '122.60', '400'), ('2009-08-15 13:41:20', '125', '1', '3', '40.97', '324'), ('2009-08-15 10:20:20', '126', '2', '45', '12.50', '345'), ('2009-08-15 13:41:20', '131', '2', '3', '40.97', '756'), ('2009-08-17 10:20:20', '3234', '1', '45', '12.50', '1322'), ('2009-08-17 10:20:20', '4642', '2', '45', '12.50', '1345'), ('2009-08-17 12:30:20', '23', '2', '49', '122.60', '3142'), ('2009-08-18 12:30:20', '2131', '1', '49', '122.60', '4700'), ('2009-08-18 13:41:20', '4568', '1', '3', '40.97', '3274'), ('2009-08-18 12:30:20', '956', '2', '49', '122.60', '3542'), ('2009-08-18 13:41:20', '443', '2', '3', '40.97', '7556'); CREATE TABLE currency ( id INT PRIMARY KEY, name VARCHAR(255) ); INSERT INTO currency (id, name) VALUES (3, 'Euro'), (45, 'US Dollar'), (49, 'CA Dollar'); CREATE TABLE calendar (datefield DATE); DELIMITER | CREATE PROCEDURE fill_calendar(start_date DATE, end_date DATE) BEGIN DECLARE crt_date DATE; SET crt_date=start_date; WHILE crt_date < end_date DO INSERT INTO calendar VALUES(crt_date); SET crt_date = ADDDATE(crt_date, INTERVAL 1 DAY); END WHILE; END | DELIMITER ; CALL fill_calendar('2008-01-01', '2011-12-31');

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• How to perform duplicate key validation using entlib (or DataAnnotations), MVC, and Repository pattern

  - by olivehour

  I have a set of ASP.NET 4 projects that culminate in an MVC (3 RC2) app. The solution uses Unity and EntLib Validation for cross-cutting dependency injection and validation. Both are working great for injecting repository and service layer implementations. However, I can't figure out how to do duplicate key validation. For example, when a user registers, we want to make sure they don't pick a UserID that someone else is already using. For this type of validation, the validating object must have a repository reference... or some other way to get an IQueryable / IEnumerable reference to check against other rows already in the DB. What I have is a UserMetadata class that has all of the property setters and getters for a user, along with all of the appropriate DataAnnotations and EntLib Validation attributes. There is also a UserEntity class implemented using EF4 POCO Entity Generator templates. The UserEntity depends on UserMetadata, because it has a MetadataTypeAttribute. I also have a UserViewModel class that has the same exact MetadataType attribute. This way, I can apply the same validation rules, via attributes, to both the entity and viewmodel. There are no concrete references to the Repository classes whatsoever. All repositories are injected using Unity. There is also a service layer that gets dependency injection. In the MVC project, service layer implementation classes are injected into the Controller classes (the controller classes only contain service layer interface references). Unity then injects the Repository implementations into the service layer classes (service classes also only contain interface references). I've experimented with the DataAnnotations CustomValidationAttribute in the metadata class. The problem with this is the validation method must be static, and the method cannot instantiate a repository implementation directly. My repository interface is IRepository, and I have only one single repository implementation class defined as EntityRepository for all domain objects. To instantiate a repository explicitly I would need to say new EntityRepository(), which would result in a circular dependency graph: UserMetadata [depends on] DuplicateUserIDValidator [depends on] UserEntity [depends on] UserMetadata. I've also tried creating a custom EntLib Validator along with a custom validation attribute. Here I don't have the same problem with a static method. I think I could get this to work if I could just figure out how to make Unity inject my EntityRepository into the validator class... which I can't. Right now, all of the validation code is in my Metadata class library, since that's where the custom validation attribute would go. Any ideas on how to perform validations that need to check against the current repository state? Can Unity be used to inject a dependency into a lower-layer class library?

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