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• How customers view and interact with a company

  The Harvard Business Review article written by Rayport and Jaworski is aptly titled “Best Face Forward” because it sheds light on how customers view and interact with a company. In the past most business interaction between customers was performed in a face to face meeting where one party would present an item for sale and then the other would decide whether to purchase the item. In addition, if there was a problem with a purchased item then they would bring the item back to the person who sold the item for resolution. One of my earliest examples of witnessing this was when I was around 6 or 7 years old and I was allowed to spend the summer in Tennessee with my Grandparents. My Grandfather had just written a book about the local history of his town and was selling them to his friends and local bookstores. I still remember he offered to pay me a small commission for every book I helped him sell because I was carrying the books around for him. Every sale he made was face to face with his customers which allowed him to share his excitement for the book with everyone. In today’s modern world there is less and less human interaction as the use of computers and other technologies allow us to communicate within seconds even though both parties may be across the globe or just next door. That being said, customers view a company through multiple access points called faces that represent the ability to interact without actually seeing a human face. As a software engineer this is a good and a bad thing because direct human interaction and technology based interaction have both good and bad attributes based on the customer. How organizations coordinate business and IT functions, to provide quality service varies based on each individual business and the goals and directives put in place by its management. According to Rayport and Jaworski, the type of interaction used through a particular access point may lend itself to be people-dominate, machine-dominate, or a combination of both. The method by which a company communicates information through an access point is a strategic choice that relates costs and customer outcomes. To simplify this, the choice is based on what can give the customer the best experience interacting with the company when the cost of the interaction is also a factor. I personally see examples of this every day at work. The company website is machine-dominate with people updating and maintaining information, our groups department is people dominate because most of the customer interaction is done at the customers location and is backed up by machine based data sources, and our sales/member service department is a hybrid because employees work in tandem with machines in order for them to assist customers with signing up or any other issue they may have. The positive and negative aspects of human and machine interfaces are a key aspect in deciding which interface to use when allowing customers to access a company or a combination of the two. Rayport and Jaworski also used MIT professor Erik Brynjolfsson preliminary catalog of human and machine strengths. He stated that humans outperform machines in judgment, pattern recognition, exception processing, insight, and creativity. I have found this to be true based on the example of how sales and member service reps at my company handle a multitude of questions and various situations with a lot of unknown variables. A machine interface could never effectively be able to handle these scenarios because there are too many variables to consider and would not have the built-in logic to process each customer’s claims and needs. In addition, he also stated that machines outperform humans in collecting, storing, transmitting and routine processing. An example of this would be my employer’s website. Customers can simply go online and purchase a product without even talking to a sales or member services representative. The information is then stored in a database so that the customer can always go back and review there order, and access their selected services. A human, no matter how smart they are would never be able to keep track of hundreds of thousands of customers let alone know what they purchased or how much they paid. In today’s technology driven economy every company must offer their customers multiple methods of accessibly in order to survive. The more of an opportunity a company has to create a positive experience for their customers, in my opinion, they more likely the customer will return to that company again. I have noticed this with my personal shopping habits and experiences. References Rayport, J., & Jaworski, B. (2004). Best Face Forward. Harvard Business Review, 82(12), 47-58. Retrieved from Business Source Complete database.

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• How is the gimbal locked problem solved using accumulative matrix transformations

  - by Luke San Antonio

  I am reading the online "Learning Modern 3D Graphics Programming" book by Jason L. McKesson As of now, I am up to the gimbal lock problem and how to solve it using quaternions. However right here, at the Quaternions page. Part of the problem is that we are trying to store an orientation as a series of 3 accumulated axial rotations. Orientations are orientations, not rotations. And orientations are certainly not a series of rotations. So we need to treat the orientation of the ship as an orientation, as a specific quantity. I guess this is the first spot I start to get confused, the reason is because I don't see the dramatic difference between orientations and rotations. I also don't understand why an orientation cannot be represented by a series of rotations... Also: The first thought towards this end would be to keep the orientation as a matrix. When the time comes to modify the orientation, we simply apply a transformation to this matrix, storing the result as the new current orientation. This means that every yaw, pitch, and roll applied to the current orientation will be relative to that current orientation. Which is precisely what we need. If the user applies a positive yaw, you want that yaw to rotate them relative to where they are current pointing, not relative to some fixed coordinate system. The concept, I understand, however I don't understand how if accumulating matrix transformations is a solution to this problem, how the code given in the previous page isn't just that. Here's the code: void display() { glClearColor(0.0f, 0.0f, 0.0f, 0.0f); glClearDepth(1.0f); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glutil::MatrixStack currMatrix; currMatrix.Translate(glm::vec3(0.0f, 0.0f, -200.0f)); currMatrix.RotateX(g_angles.fAngleX); DrawGimbal(currMatrix, GIMBAL_X_AXIS, glm::vec4(0.4f, 0.4f, 1.0f, 1.0f)); currMatrix.RotateY(g_angles.fAngleY); DrawGimbal(currMatrix, GIMBAL_Y_AXIS, glm::vec4(0.0f, 1.0f, 0.0f, 1.0f)); currMatrix.RotateZ(g_angles.fAngleZ); DrawGimbal(currMatrix, GIMBAL_Z_AXIS, glm::vec4(1.0f, 0.3f, 0.3f, 1.0f)); glUseProgram(theProgram); currMatrix.Scale(3.0, 3.0, 3.0); currMatrix.RotateX(-90); //Set the base color for this object. glUniform4f(baseColorUnif, 1.0, 1.0, 1.0, 1.0); glUniformMatrix4fv(modelToCameraMatrixUnif, 1, GL_FALSE, glm::value_ptr(currMatrix.Top())); g_pObject->Render("tint"); glUseProgram(0); glutSwapBuffers(); } To my understanding, isn't what he is doing (modifying a matrix on a stack) considered accumulating matrices, since the author combined all the individual rotation transformations into one matrix which is being stored on the top of the stack. My understanding of a matrix is that they are used to take a point which is relative to an origin (let's say... the model), and make it relative to another origin (the camera). I'm pretty sure this is a safe definition, however I feel like there is something missing which is blocking me from understanding this gimbal lock problem. One thing that doesn't make sense to me is: If a matrix determines the difference relative between two "spaces," how come a rotation around the Y axis for, let's say, roll, doesn't put the point in "roll space" which can then be transformed once again in relation to this roll... In other words shouldn't any further transformations to this point be in relation to this new "roll space" and therefore not have the rotation be relative to the previous "model space" which is causing the gimbal lock. That's why gimbal lock occurs right? It's because we are rotating the object around set X, Y, and Z axes rather than rotating the object around it's own, relative axes. Or am I wrong? Since apparently this code I linked in isn't an accumulation of matrix transformations can you please give an example of a solution using this method. So in summary: What is the difference between a rotation and an orientation? Why is the code linked in not an example of accumulation of matrix transformations? What is the real, specific purpose of a matrix, if I had it wrong? How could a solution to the gimbal lock problem be implemented using accumulation of matrix transformations? Also, as a bonus: Why are the transformations after the rotation still relative to "model space?" Another bonus: Am I wrong in the assumption that after a transformation, further transformations will occur relative to the current? Also, if it wasn't implied, I am using OpenGL, GLSL, C++, and GLM, so examples and explanations in terms of these are greatly appreciated, if not necessary. The more the detail the better! Thanks in advance...

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• "Imprinting" as a language feature?

  - by MKO

  Idea I had this idea for a language feature that I think would be useful, does anyone know of a language that implements something like this? The idea is that besides inheritance a class can also use something called "imprinting" (for lack of better term). A class can imprint one or several (non-abstract) classes. When a class imprints another class it gets all it's properties and all it's methods. It's like the class storing an instance of the imprinted class and redirecting it's methods/properties to it. A class that imprints another class therefore by definition also implements all it's interfaces and it's abstract class. So what's the point? Well, inheritance and polymorphism is hard to get right. Often composition gives far more flexibility. Multiple inheritance offers a slew of different problems without much benefits (IMO). I often write adapter classes (in C#) by implementing some interface and passing along the actual methods/properties to an encapsulated object. The downside to that approach is that if the interface changes the class breaks. You also you have to put in a lot of code that does nothing but pass things along to the encapsulated object. A classic example is that you have some class that implements IEnumerable or IList and contains an internal class it uses. With this technique things would be much easier Example (c#) [imprint List<Person> as peopleList] public class People : PersonBase { public void SomeMethod() { DoSomething(this.Count); //Count is from List } } //Now People can be treated as an List<Person> People people = new People(); foreach(Person person in people) { ... } peopleList is an alias/variablename (of your choice)used internally to alias the instance but can be skipped if not needed. One thing that's useful is to override an imprinted method, that could be achieved with the ordinary override syntax public override void Add(Person person) { DoSomething(); personList.Add(person); } note that the above is functional equivalent (and could be rewritten by the compiler) to: public class People : PersonBase , IList<Person> { private List<Person> personList = new List<Person>(); public override void Add(object obj) { this.personList.Add(obj) } public override int IndexOf(object obj) { return personList.IndexOf(obj) } //etc etc for each signature in the interface } only if IList changes your class will break. IList won't change but an interface that you, someone in your team, or a thirdparty has designed might just change. Also this saves you writing a whole lot of code for some interfaces/abstract classes. Caveats There's a couple of gotchas. First we, syntax must be added to call the imprinted classes's constructors from the imprinting class constructor. Also, what happends if a class imprints two classes which have the same method? In that case the compiler would detect it and force the class to define an override of that method (where you could chose if you wanted to call either imprinted class or both) So what do you think, would it be useful, any caveats? It seems it would be pretty straightforward to implement something like that in the C# language but I might be missing something :) Sidenote - Why is this different from multiple inheritance Ok, so some people have asked about this. Why is this different from multiple inheritance and why not multiple inheritance. In C# methods are either virtual or not. Say that we have ClassB who inherits from ClassA. ClassA has the methods MethodA and MethodB. ClassB overrides MethodA but not MethodB. Now say that MethodB has a call to MethodA. if MethodA is virtual it will call the implementation that ClassB has, if not it will use the base class, ClassA's MethodA and you'll end up wondering why your class doesn't work as it should. By the terminology sofar you might already confused. So what happens if ClassB inherits both from ClassA and another ClassC. I bet both programmers and compilers will be scratching their heads. The benefit of this approach IMO is that the imprinting classes are totally encapsulated and need not be designed with multiple inheritance in mind. You can basically imprint anything.

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• SQL Server - Rebuilding Indexes

  - by Renso

  Goal: Rebuild indexes in SQL server. This can be done one at a time or with the example script below to rebuild all index for a specified table or for all tables in a given database. Why? The data in indexes gets fragmented over time. That means that as the index grows, the newly added rows to the index are physically stored in other sections of the allocated database storage space. Kind of like when you load your Christmas shopping into the trunk of your car and it is full you continue to load some on the back seat, in the same way some storage buffer is created for your index but once that runs out the data is then stored in other storage space and your data in your index is no longer stored in contiguous physical pages. To access the index the database manager has to "string together" disparate fragments to create the full-index and create one contiguous set of pages for that index. Defragmentation fixes that. What does the fragmentation affect?Depending of course on how large the table is and how fragmented the data is, can cause SQL Server to perform unnecessary data reads, slowing down SQL Server’s performance.Which index to rebuild?As a rule consider that when reorganize a table's clustered index, all other non-clustered indexes on that same table will automatically be rebuilt. A table can only have one clustered index.How to rebuild all the index for one table:The DBCC DBREINDEX command will not automatically rebuild all of the indexes on a given table in a databaseHow to rebuild all indexes for all tables in a given database:USE [myDB]    -- enter your database name hereDECLARE @tableName varchar(255)DECLARE TableCursor CURSOR FORSELECT table_name FROM information_schema.tablesWHERE table_type = 'base table'OPEN TableCursorFETCH NEXT FROM TableCursor INTO @tableNameWHILE @@FETCH_STATUS = 0BEGINDBCC DBREINDEX(@tableName,' ',90)     --a fill factor of 90%FETCH NEXT FROM TableCursor INTO @tableNameENDCLOSE TableCursorDEALLOCATE TableCursorWhat does this script do?Reindexes all indexes in all tables of the given database. Each index is filled with a fill factor of 90%. While the command DBCC DBREINDEX runs and rebuilds the indexes, that the table becomes unavailable for use by your users temporarily until the rebuild has completed, so don't do this during production  hours as it will create a shared lock on the tables, although it will allow for read-only uncommitted data reads; i.e.e SELECT.What is the fill factor?Is the percentage of space on each index page for storing data when the index is created or rebuilt. It replaces the fill factor when the index was created, becoming the new default for the index and for any other nonclustered indexes rebuilt because a clustered index is rebuilt. When fillfactor is 0, DBCC DBREINDEX uses the fill factor value last specified for the index. This value is stored in the sys.indexes catalog view. If fillfactor is specified, table_name and index_name must be specified. If fillfactor is not specified, the default fill factor, 100, is used.How do I determine the level of fragmentation?Run the DBCC SHOWCONTIG command. However this requires you to specify the ID of both the table and index being. To make it a lot easier by only requiring you to specify the table name and/or index you can run this script:DECLARE@ID int,@IndexID int,@IndexName varchar(128)--Specify the table and index namesSELECT @IndexName = ‘index_name’    --name of the indexSET @ID = OBJECT_ID(‘table_name’)  -- name of the tableSELECT @IndexID = IndIDFROM sysindexesWHERE id = @ID AND name = @IndexName--Show the level of fragmentationDBCC SHOWCONTIG (@id, @IndexID)Here is an example:DBCC SHOWCONTIG scanning 'Tickets' table...Table: 'Tickets' (1829581556); index ID: 1, database ID: 13TABLE level scan performed.- Pages Scanned................................: 915- Extents Scanned..............................: 119- Extent Switches..............................: 281- Avg. Pages per Extent........................: 7.7- Scan Density [Best Count:Actual Count].......: 40.78% [115:282]- Logical Scan Fragmentation ..................: 16.28%- Extent Scan Fragmentation ...................: 99.16%- Avg. Bytes Free per Page.....................: 2457.0- Avg. Page Density (full).....................: 69.64%DBCC execution completed. If DBCC printed error messages, contact your system administrator.What's important here?The Scan Density; Ideally it should be 100%. As time goes by it drops as fragmentation occurs. When the level drops below 75%, you should consider re-indexing.Here are the results of the same table and clustered index after running the script:DBCC SHOWCONTIG scanning 'Tickets' table...Table: 'Tickets' (1829581556); index ID: 1, database ID: 13TABLE level scan performed.- Pages Scanned................................: 692- Extents Scanned..............................: 87- Extent Switches..............................: 86- Avg. Pages per Extent........................: 8.0- Scan Density [Best Count:Actual Count].......: 100.00% [87:87]- Logical Scan Fragmentation ..................: 0.00%- Extent Scan Fragmentation ...................: 22.99%- Avg. Bytes Free per Page.....................: 639.8- Avg. Page Density (full).....................: 92.10%DBCC execution completed. If DBCC printed error messages, contact your system administrator.What's different?The Scan Density has increased from 40.78% to 100%; no fragmentation on the clustered index. Note that since we rebuilt the clustered index, all other index were also rebuilt.

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• Developing Schema Compare for Oracle (Part 6): 9i Query Performance

  - by Simon Cooper

  All throughout the EAP and beta versions of Schema Compare for Oracle, our main request was support for Oracle 9i. After releasing version 1.0 with support for 10g and 11g, our next step was then to get version 1.1 of SCfO out with support for 9i. However, there were some significant problems that we had to overcome first. This post will concentrate on query execution time. When we first tested SCfO on a 9i server, after accounting for various changes to the data dictionary, we found that database registration was taking a long time. And I mean a looooooong time. The same database that on 10g or 11g would take a couple of minutes to register would be taking upwards of 30 mins on 9i. Obviously, this is not ideal, so a poke around the query execution plans was required. As an example, let's take the table population query - the one that reads ALL_TABLES and joins it with a few other dictionary views to get us back our list of tables. On 10g, this query takes 5.6 seconds. On 9i, it takes 89.47 seconds. The difference in execution plan is even more dramatic - here's the (edited) execution plan on 10g: -------------------------------------------------------------------------------| Id | Operation | Name | Bytes | Cost |-------------------------------------------------------------------------------| 0 | SELECT STATEMENT | | 108K| 939 || 1 | SORT ORDER BY | | 108K| 939 || 2 | NESTED LOOPS OUTER | | 108K| 938 ||* 3 | HASH JOIN RIGHT OUTER | | 103K| 762 || 4 | VIEW | ALL_EXTERNAL_LOCATIONS | 2058 | 3 ||* 20 | HASH JOIN RIGHT OUTER | | 73472 | 759 || 21 | VIEW | ALL_EXTERNAL_TABLES | 2097 | 3 ||* 34 | HASH JOIN RIGHT OUTER | | 39920 | 755 || 35 | VIEW | ALL_MVIEWS | 51 | 7 || 58 | NESTED LOOPS OUTER | | 39104 | 748 || 59 | VIEW | ALL_TABLES | 6704 | 668 || 89 | VIEW PUSHED PREDICATE | ALL_TAB_COMMENTS | 2025 | 5 || 106 | VIEW | ALL_PART_TABLES | 277 | 11 |------------------------------------------------------------------------------- And the same query on 9i: -------------------------------------------------------------------------------| Id | Operation | Name | Bytes | Cost |-------------------------------------------------------------------------------| 0 | SELECT STATEMENT | | 16P| 55G|| 1 | SORT ORDER BY | | 16P| 55G|| 2 | NESTED LOOPS OUTER | | 16P| 862M|| 3 | NESTED LOOPS OUTER | | 5251G| 992K|| 4 | NESTED LOOPS OUTER | | 4243M| 2578 || 5 | NESTED LOOPS OUTER | | 2669K| 1440 ||* 6 | HASH JOIN OUTER | | 398K| 302 || 7 | VIEW | ALL_TABLES | 342K| 276 || 29 | VIEW | ALL_MVIEWS | 51 | 20 ||* 50 | VIEW PUSHED PREDICATE | ALL_TAB_COMMENTS | 2043 | ||* 66 | VIEW PUSHED PREDICATE | ALL_EXTERNAL_TABLES | 1777K| ||* 80 | VIEW PUSHED PREDICATE | ALL_EXTERNAL_LOCATIONS | 1744K| ||* 96 | VIEW | ALL_PART_TABLES | 852K| |------------------------------------------------------------------------------- Have a look at the cost column. 10g's overall query cost is 939, and 9i is 55,000,000,000 (or more precisely, 55,496,472,769). It's also having to process far more data. What on earth could be causing this huge difference in query cost? After trawling through the '10g New Features' documentation, we found item 1.9.2.21. Before 10g, Oracle advised that you do not collect statistics on data dictionary objects. From 10g, it advised that you do collect statistics on the data dictionary; for our queries, Oracle therefore knows what sort of data is in the dictionary tables, and so can generate an efficient execution plan. On 9i, no statistics are present on the system tables, so Oracle has to use the Rule Based Optimizer, which turns most LEFT JOINs into nested loops. If we force 9i to use hash joins, like 10g, we get a much better plan: -------------------------------------------------------------------------------| Id | Operation | Name | Bytes | Cost |-------------------------------------------------------------------------------| 0 | SELECT STATEMENT | | 7587K| 3704 || 1 | SORT ORDER BY | | 7587K| 3704 ||* 2 | HASH JOIN OUTER | | 7587K| 822 ||* 3 | HASH JOIN OUTER | | 5262K| 616 ||* 4 | HASH JOIN OUTER | | 2980K| 465 ||* 5 | HASH JOIN OUTER | | 710K| 432 ||* 6 | HASH JOIN OUTER | | 398K| 302 || 7 | VIEW | ALL_TABLES | 342K| 276 || 29 | VIEW | ALL_MVIEWS | 51 | 20 || 50 | VIEW | ALL_PART_TABLES | 852K| 104 || 78 | VIEW | ALL_TAB_COMMENTS | 2043 | 14 || 93 | VIEW | ALL_EXTERNAL_LOCATIONS | 1744K| 31 || 106 | VIEW | ALL_EXTERNAL_TABLES | 1777K| 28 |------------------------------------------------------------------------------- That's much more like it. This drops the execution time down to 24 seconds. Not as good as 10g, but still an improvement. There are still several problems with this, however. 10g introduced a new join method - a right outer hash join (used in the first execution plan). The 9i query optimizer doesn't have this option available, so forcing a hash join means it has to hash the ALL_TABLES table, and furthermore re-hash it for every hash join in the execution plan; this could be thousands and thousands of rows. And although forcing hash joins somewhat alleviates this problem on our test systems, there's no guarantee that this will improve the execution time on customers' systems; it may even increase the time it takes (say, if all their tables are partitioned, or they've got a lot of materialized views). Ideally, we would want a solution that provides a speedup whatever the input. To try and get some ideas, we asked some oracle performance specialists to see if they had any ideas or tips. Their recommendation was to add a hidden hook into the product that allowed users to specify their own query hints, or even rewrite the queries entirely. However, we would prefer not to take that approach; as well as a lot of new infrastructure & a rewrite of the population code, it would have meant that any users of 9i would have to spend some time optimizing it to get it working on their system before they could use the product. Another approach was needed. All our population queries have a very specific pattern - a base table provides most of the information we need (ALL_TABLES for tables, or ALL_TAB_COLS for columns) and we do a left join to extra subsidiary tables that fill in gaps (for instance, ALL_PART_TABLES for partition information). All the left joins use the same set of columns to join on (typically the object owner & name), so we could re-use the hash information for each join, rather than re-hashing the same columns for every join. To allow us to do this, along with various other performance improvements that could be done for the specific query pattern we were using, we read all the tables individually and do a hash join on the client. Fortunately, this 'pure' algorithmic problem is the kind that can be very well optimized for expected real-world situations; as well as storing row data we're not using in the hash key on disk, we use very specific memory-efficient data structures to store all the information we need. This allows us to achieve a database population time that is as fast as on 10g, and even (in some situations) slightly faster, and a memory overhead of roughly 150 bytes per row of data in the result set (for schemas with 10,000 tables in that means an extra 1.4MB memory being used during population). Next: fun with the 9i dictionary views.

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• Microsoft Sql Server 2008 R2 System Databases

  For a majority of software developers little time is spent understanding the inner workings of the database management systems (DBMS) they use to store data for their applications.  I personally place myself in this grouping. In my case, I have used various versions of Microsoft’s SQL Server (2000, 2005, and 2008 R2) and just recently learned how valuable they really are when I was preparing to deliver a lecture on "SQL Server 2008 R2, System Databases". Microsoft Sql Server 2008 R2 System DatabasesSo what are system databases in MS SQL Server, and why should I know them? Microsoft uses system databases to support the SQL Server DBMS, much like a developer uses config files or database tables to support an application. These system databases individually provide specific functionality that allows MS SQL Server to function. Name Database File Log File Master master.mdf mastlog.ldf Resource mssqlsystemresource.mdf mssqlsystemresource.ldf Model model.mdf modellog.ldf MSDB msdbdata.mdf msdblog.ldf Distribution distmdl.mdf distmdl.ldf TempDB tempdb.mdf templog.ldf Master DatabaseIf you have used MS SQL Server then you should recognize the Master database especially if you used the SQL Server Management Studio (SSMS) to connect to a user created database. MS SQL Server requires the Master database in order for DBMS to start due to the information that it stores. Examples of data stored in the Master database User Logins Linked Servers Configuration information Information on User Databases Resource DatabaseHonestly, until recently I never knew this database even existed until I started to research SQL Server system databases. The reason for this is due largely to the fact that the resource database is hidden to users. In fact, the database files are stored within the Binn folder instead of the standard MS SQL Server database folder path. This database contains all system objects that can be accessed by all other databases.  In short, this database contains all system views and store procedures that appear in all other user databases regarding system information. One of the many benefits to storing system views and store procedures in a single hidden database is the fact it improves upgrading a SQL Server database; not to mention that maintenance is decreased since only one code base has to be mainlined for all of the system views and procedures. Model DatabaseThe Model database as the name implies is the model for all new databases created by users. This allows for predefining default database objects for all new databases within a MS SQL Server instance. For example, if every database created by a user needs to have an “Audit” table when it is  created then defining the “Audit” table in the model will guarantees that the table will be located in every new database create after the model is altered. MSDB DatabaseThe MSDBdatabase is used by SQL Server Agent, SQL Server Database Mail, SQL Server Service Broker, along with SQL Server. The SQL Server Agent uses this database to store job configurations and SQL job schedules along with SQL Alerts, and Operators. In addition, this database also stores all SQL job parameters along with each job’s execution history.  Finally, this database is also used to store database backup and maintenance plans as well as details pertaining to SQL Log shipping if it is being used. Distribution DatabaseThe Distribution database is only used during replication and stores meta data and history information pertaining to the act of replication data. Furthermore, when transactional replication is used this database also stores information regarding each transaction. It is important to note that replication is not turned on by default in MS SQL Server and that the distribution database is hidden from SSMS. Tempdb DatabaseThe Tempdb as the name implies is used to store temporary data and data objects. Examples of this include temp tables and temp store procedures. It is important to note that when using this database all data and data objects are cleared from this database when SQL Server restarts. This database is also used by SQL Server when it is performing some internal operations. Typically, SQL Server uses this database for the purpose of large sort and index operations. Finally, this database is used to store row versions if row versioning or snapsot isolation transactions are being used by SQL Server. Additionally, I would love to hear from others about their experiences using system databases, tables, and objects in a real world environments.

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• Efficient way to render tile-based map in Java

  - by Lucius

  Some time ago I posted here because I was having some memory issues with a game I'm working on. That has been pretty much solved thanks to some suggestions here, so I decided to come back with another problem I'm having. Basically, I feel that too much of the CPU is being used when rendering the map. I have a Core i5-2500 processor and when running the game, the CPU usage is about 35% - and I can't accept that that's just how it has to be. This is how I'm going about rendering the map: I have the X and Y coordinates of the player, so I'm not drawing the whole map, just the visible portion of it; The number of visible tiles on screen varies according to the resolution chosen by the player (the CPU usage is 35% here when playing at a resolution of 1440x900); If the tile is "empty", I just skip drawing it (this didn't visibly lower the CPU usage, but reduced the drawing time in about 20ms); The map is composed of 5 layers - for more details; The tiles are 32x32 pixels; And just to be on the safe side, I'll post the code for drawing the game here, although it's as messy and unreadable as it can be T_T (I'll try to make it a little readable) private void drawGame(Graphics2D g2d){ //Width and Height of the visible portion of the map (not of the screen) int visionWidht = visibleCols * TILE_SIZE; int visionHeight = visibleRows * TILE_SIZE; //Since the map can be smaller than the screen, I center it just to be sure int xAdjust = (getWidth() - visionWidht) / 2; int yAdjust = (getHeight() - visionHeight) / 2; //This "deducedX" thing is to move the map a few pixels horizontally, since the player moves by pixels and not full tiles int playerDrawX = listOfCharacters.get(0).getX(); int deducedX = 0; if (listOfCharacters.get(0).currentCol() - visibleCols / 2 >= 0) { playerDrawX = visibleCols / 2 * TILE_SIZE; map_draw_col = listOfCharacters.get(0).currentCol() - visibleCols / 2; deducedX = listOfCharacters.get(0).getXCol(); } //"deducedY" is the same deal as "deducedX", but vertically int playerDrawY = listOfCharacters.get(0).getY(); int deducedY = 0; if (listOfCharacters.get(0).currentRow() - visibleRows / 2 >= 0) { playerDrawY = visibleRows / 2 * TILE_SIZE; map_draw_row = listOfCharacters.get(0).currentRow() - visibleRows / 2; deducedY = listOfCharacters.get(0).getYRow(); } int max_cols = visibleCols + map_draw_col; if (max_cols >= map.getCols()) { max_cols = map.getCols() - 1; deducedX = 0; map_draw_col = max_cols - visibleCols + 1; playerDrawX = listOfCharacters.get(0).getX() - map_draw_col * TILE_SIZE; } int max_rows = visibleRows + map_draw_row; if (max_rows >= map.getRows()) { max_rows = map.getRows() - 1; deducedY = 0; map_draw_row = max_rows - visibleRows + 1; playerDrawY = listOfCharacters.get(0).getY() - map_draw_row * TILE_SIZE; } //map_draw_row and map_draw_col representes the coordinate of the upper left tile on the screen //iterate through all the tiles on screen and draw them - this is what consumes most of the CPU for (int col = map_draw_col; col <= max_cols; col++) { for (int row = map_draw_row; row <= max_rows; row++) { Tile[] tiles = map.getTiles(col, row); for(int layer = 0; layer < tiles.length; layer++){ Tile currentTile = tiles[layer]; boolean shouldDraw = true; //I only draw the tile if it exists and is not empty (id=-1) if(currentTile != null && currentTile.getId() >= 0){ //The layers above 1 can be draw behing or infront of the player according to where it's standing if(layer > 1 && currentTile.getId() >= 0){ if(playerBehind(col, row, layer, listOfCharacters.get(0))){ behinds.get(0).add(new int[]{col, row}); //the tiles that are infront of the player wont be draw right now shouldDraw = false; } } if(shouldDraw){ g2d.drawImage( tiles[layer].getImage(), (col-map_draw_col)*TILE_SIZE - deducedX + xAdjust, (row-map_draw_row)*TILE_SIZE - deducedY + yAdjust, null); } } } } } } There's some more code in this method but nothing relevant to this question. Basically, the biggest problem is that I iterate over around 5000 tiles (in this specific resolution) 60 times each second. I thought about rendering the visible portion of the map once and storing it into a BufferedImage and when the player moved move the whole image the same amount but to the opposite side and then drawn the tiles that appeared on the screen, but if I do it like that, I wont be able to have animated tiles (at least I think). That being said, any suggestions?

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• Microsoft Sql Server 2008 R2 System Databases

  For a majority of software developers little time is spent understanding the inner workings of the database management systems (DBMS) they use to store data for their applications.  I personally place myself in this grouping. In my case, I have used various versions of Microsoft’s SQL Server (2000, 2005, and 2008 R2) and just recently learned how valuable they really are when I was preparing to deliver a lecture on "SQL Server 2008 R2, System Databases". Microsoft Sql Server 2008 R2 System DatabasesSo what are system databases in MS SQL Server, and why should I know them? Microsoft uses system databases to support the SQL Server DBMS, much like a developer uses config files or database tables to support an application. These system databases individually provide specific functionality that allows MS SQL Server to function. Name Database File Log File Master master.mdf mastlog.ldf Resource mssqlsystemresource.mdf mssqlsystemresource.ldf Model model.mdf modellog.ldf MSDB msdbdata.mdf msdblog.ldf Distribution distmdl.mdf distmdl.ldf TempDB tempdb.mdf templog.ldf Master DatabaseIf you have used MS SQL Server then you should recognize the Master database especially if you used the SQL Server Management Studio (SSMS) to connect to a user created database. MS SQL Server requires the Master database in order for DBMS to start due to the information that it stores. Examples of data stored in the Master database User Logins Linked Servers Configuration information Information on User Databases Resource DatabaseHonestly, until recently I never knew this database even existed until I started to research SQL Server system databases. The reason for this is due largely to the fact that the resource database is hidden to users. In fact, the database files are stored within the Binn folder instead of the standard MS SQL Server database folder path. This database contains all system objects that can be accessed by all other databases.  In short, this database contains all system views and store procedures that appear in all other user databases regarding system information. One of the many benefits to storing system views and store procedures in a single hidden database is the fact it improves upgrading a SQL Server database; not to mention that maintenance is decreased since only one code base has to be mainlined for all of the system views and procedures. Model DatabaseThe Model database as the name implies is the model for all new databases created by users. This allows for predefining default database objects for all new databases within a MS SQL Server instance. For example, if every database created by a user needs to have an “Audit” table when it is  created then defining the “Audit” table in the model will guarantees that the table will be located in every new database create after the model is altered. MSDB DatabaseThe MSDBdatabase is used by SQL Server Agent, SQL Server Database Mail, SQL Server Service Broker, along with SQL Server. The SQL Server Agent uses this database to store job configurations and SQL job schedules along with SQL Alerts, and Operators. In addition, this database also stores all SQL job parameters along with each job’s execution history.  Finally, this database is also used to store database backup and maintenance plans as well as details pertaining to SQL Log shipping if it is being used. Distribution DatabaseThe Distribution database is only used during replication and stores meta data and history information pertaining to the act of replication data. Furthermore, when transactional replication is used this database also stores information regarding each transaction. It is important to note that replication is not turned on by default in MS SQL Server and that the distribution database is hidden from SSMS. Tempdb DatabaseThe Tempdb as the name implies is used to store temporary data and data objects. Examples of this include temp tables and temp store procedures. It is important to note that when using this database all data and data objects are cleared from this database when SQL Server restarts. This database is also used by SQL Server when it is performing some internal operations. Typically, SQL Server uses this database for the purpose of large sort and index operations. Finally, this database is used to store row versions if row versioning or snapsot isolation transactions are being used by SQL Server. Additionally, I would love to hear from others about their experiences using system databases, tables, and objects in a real world environments.

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• Processing Text and Binary (Blob, ArrayBuffer, ArrayBufferView) Payload in WebSocket - (TOTD #185)

  - by arungupta

  The WebSocket API defines different send(xxx) methods that can be used to send text and binary data. This Tip Of The Day (TOTD) will show how to send and receive text and binary data using WebSocket. TOTD #183 explains how to get started with a WebSocket endpoint using GlassFish 4. A simple endpoint from that blog looks like: @WebSocketEndpoint("/endpoint") public class MyEndpoint { public void receiveTextMessage(String message) { . . . } } A message with the first parameter of the type String is invoked when a text payload is received. The payload of the incoming WebSocket frame is mapped to this first parameter. An optional second parameter, Session, can be specified to map to the "other end" of this conversation. For example: public void receiveTextMessage(String message, Session session) {     . . . } The return type is void and that means no response is returned to the client that invoked this endpoint. A response may be returned to the client in two different ways. First, set the return type to the expected type, such as: public String receiveTextMessage(String message) { String response = . . . . . . return response; } In this case a text payload is returned back to the invoking endpoint. The second way to send a response back is to use the mapped session to send response using one of the sendXXX methods in Session, when and if needed. public void receiveTextMessage(String message, Session session) {     . . .     RemoteEndpoint remote = session.getRemote();     remote.sendString(...);     . . .     remote.sendString(...);    . . .    remote.sendString(...); } This shows how duplex and asynchronous communication between the two endpoints can be achieved. This can be used to define different message exchange patterns between the client and server. The WebSocket client can send the message as: websocket.send(myTextField.value); where myTextField is a text field in the web page. Binary payload in the incoming WebSocket frame can be received if ByteBuffer is used as the first parameter of the method signature. The endpoint method signature in that case would look like: public void receiveBinaryMessage(ByteBuffer message) {     . . . } From the client side, the binary data can be sent using Blob, ArrayBuffer, and ArrayBufferView. Blob is a just raw data and the actual interpretation is left to the application. ArrayBuffer and ArrayBufferView are defined in the TypedArray specification and are designed to send binary data using WebSocket. In short, ArrayBuffer is a fixed-length binary buffer with no format and no mechanism for accessing its contents. These buffers are manipulated using one of the views defined by one of the subclasses of ArrayBufferView listed below: Int8Array (signed 8-bit integer or char) Uint8Array (unsigned 8-bit integer or unsigned char) Int16Array (signed 16-bit integer or short) Uint16Array (unsigned 16-bit integer or unsigned short) Int32Array (signed 32-bit integer or int) Uint32Array (unsigned 16-bit integer or unsigned int) Float32Array (signed 32-bit float or float) Float64Array (signed 64-bit float or double) WebSocket can send binary data using ArrayBuffer with a view defined by a subclass of ArrayBufferView or a subclass of ArrayBufferView itself. The WebSocket client can send the message using Blob as: blob = new Blob([myField2.value]);websocket.send(blob); where myField2 is a text field in the web page. The WebSocket client can send the message using ArrayBuffer as: var buffer = new ArrayBuffer(10);var bytes = new Uint8Array(buffer);for (var i=0; i<bytes.length; i++) { bytes[i] = i;}websocket.send(buffer); A concrete implementation of receiving the binary message may look like: @WebSocketMessagepublic void echoBinary(ByteBuffer data, Session session) throws IOException {    System.out.println("echoBinary: " + data);    for (byte b : data.array()) {        System.out.print(b);    }    session.getRemote().sendBytes(data);} This method is just printing the binary data for verification but you may actually be storing it in a database or converting to an image or something more meaningful. Be aware of TYRUS-51 if you are trying to send binary data from server to client using method return type. Here are some references for you: JSR 356: Java API for WebSocket - Specification (Early Draft) and Implementation (already integrated in GlassFish 4 promoted builds) TOTD #183 - Getting Started with WebSocket in GlassFish TOTD #184 - Logging WebSocket Frames using Chrome Developer Tools, Net-internals and Wireshark Subsequent blogs will discuss the following topics (not necessary in that order) ... Error handling Custom payloads using encoder/decoder Interface-driven WebSocket endpoint Java client API Client and Server configuration Security Subprotocols Extensions Other topics from the API

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• BeansBinding Across Modules in a NetBeans Platform Application

  - by Geertjan

  Here's two TopComponents, each in a different NetBeans module. Let's use BeansBinding to synchronize the JTextField in TC2TopComponent with the data published by TC1TopComponent and received in TC2TopComponent by listening to the Lookup. The key to getting to the solution is to have the following in TC2TopComponent, which implements LookupListener: private BindingGroup bindingGroup = null; private AutoBinding binding = null; @Override public void resultChanged(LookupEvent le) { if (bindingGroup != null && binding != null) { bindingGroup.getBinding("customerNameBinding").unbind(); } if (!result.allInstances().isEmpty()){ Customer c = result.allInstances().iterator().next(); // put the customer into the lookup of this topcomponent, // so that it will remain in the lookup when focus changes // to this topcomponent: ic.set(Collections.singleton(c), null); bindingGroup = new BindingGroup(); binding = Bindings.createAutoBinding( // a two-way binding, i.e., a change in // one will cause a change in the other: AutoBinding.UpdateStrategy.READ_WRITE, // source: c, BeanProperty.create("name"), // target: jTextField1, BeanProperty.create("text"), // binding name: "customerNameBinding"); bindingGroup.addBinding(binding); bindingGroup.bind(); } } I must say that this solution is preferable over what I've been doing prior to getting to this solution: I would get the customer from the resultChanged, set a class-level field to that customer, add a document listener (or action listener, which is invoked when Enter is pressed) on the text field and, when a change is detected, set the new value on the customer. All that is not needed with the above bit of code. Then, in the node, make sure to use canRename, setName, and getDisplayName, so that when the user presses F2 on a node, the display name can be changed. In other words, when the user types something different in the node display name after pressing F2, the underlying customer name is changed, which happens, in the first place, because the customer name is bound to the text field's value, so that the text field's value will also change once enter is pressed on the changed node display name. Also set a PropertyChangeListener on the node (which implies you need to add property change support to the customer object), so that when the customer object changes (which happens, in the second place, via a change in the value of the text field, as defined in the binding defined above), the node display name is updated. In other words, there's still a bit of plumbing you need to include. But less than before and the nasty class-level field for storing the customer in the TC2TopComponent is no longer needed. And a listener on the text field, with a property change listener implented on the TC2TopComponent, isn't needed either. On the other hand, it's more code than I was using before and I've had to include the BeansBinding JAR, which adds a bit of overhead to my application, without much additional functionality over what I was doing originally. I'd lean towards not doing things this way. Seems quite expensive for essentially replacing a listener on a text field and a property change listener implemented on the TC2TopComponent for being notified of changes to the customer so that the text field can be updated. On the other other hand, it's kind of nice that all this listening-related code is centralized in one place now. So, here's a nice improvement over the above. Instead of listening for a customer, listen for a node, from which the customer can be obtained. Then, bind the node display name to the text field's value, so that when the user types in the text field, the node display name is updated. That saves you from having to listen in the node for changes to the customer's name. In addition to that binding, keep the previous binding, because the previous binding connects the customer name to the text field, so that when the customer display name is changed via F2 on the node, the text field will be updated. private BindingGroup bindingGroup = null; private AutoBinding nodeUpdateBinding; private AutoBinding textFieldUpdateBinding; @Override public void resultChanged(LookupEvent le) { if (bindingGroup != null && textFieldUpdateBinding != null) { bindingGroup.getBinding("textFieldUpdateBinding").unbind(); } if (bindingGroup != null && nodeUpdateBinding != null) { bindingGroup.getBinding("nodeUpdateBinding").unbind(); } if (!result.allInstances().isEmpty()) { Node n = result.allInstances().iterator().next(); Customer c = n.getLookup().lookup(Customer.class); ic.set(Collections.singleton(n), null); bindingGroup = new BindingGroup(); nodeUpdateBinding = Bindings.createAutoBinding( AutoBinding.UpdateStrategy.READ_WRITE, n, BeanProperty.create("name"), jTextField1, BeanProperty.create("text"), "nodeUpdateBinding"); bindingGroup.addBinding(nodeUpdateBinding); textFieldUpdateBinding = Bindings.createAutoBinding( AutoBinding.UpdateStrategy.READ_WRITE, c, BeanProperty.create("name"), jTextField1, BeanProperty.create("text"), "textFieldUpdateBinding"); bindingGroup.addBinding(textFieldUpdateBinding); bindingGroup.bind(); } } Now my node has no property change listener, while the customer has no property change support. As in the first bit of code, the text field doesn't have a listener either. All that listening is taken care of by the BeansBinding code.  Thanks to Toni for help with this, though he can't be blamed for anything that is wrong with it, only thanked for anything that is right with it. 

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• SQLite file locking and DropBox

  - by Alex Jenter

  I'm developing an app in Visual C++ that uses an SQLite3 DB for storing data. Usually it sits in the tray most of the time. I also would like to enable putting my app in a DropBox folder to share it across several PCs. It worked really well up until DropBox has recently updated itself. And now it says that it "can't sync the file in use". The SQLite file is open in my app, but the lock is shared. There are some prepared statements, but all are reset immediately after using step. Is there any way to enable synchronizing of an open SQLite database file? Thanks! Here is the simple wrapper that I use just for testing (no error handling), in case this helps: class Statement { private: Statement(sqlite3* db, const std::wstring& sql) : db(db) { sqlite3_prepare16_v2(db, sql.c_str(), sql.length() * sizeof(wchar_t), &stmt, NULL); } public: ~Statement() { sqlite3_finalize(stmt); } public: void reset() { sqlite3_reset(stmt); } int step() { return sqlite3_step(stmt); } int getInt(int i) const { return sqlite3_column_int(stmt, i); } tstring getText(int i) const { const wchar_t* v = (const wchar_t*)sqlite3_column_text16(stmt, i); int sz = sqlite3_column_bytes16(stmt, i) / sizeof(wchar_t); return std::wstring(v, v + sz); } private: friend class Database; sqlite3* db; sqlite3_stmt* stmt; }; class Database { public: Database(const std::wstring& filename = L"")) : db(NULL) { sqlite3_open16(filename.c_str(), &db); } ~Database() { sqlite3_close(db); } void exec(const std::wstring& sql) { auto_ptr<Statement> st(prepare(sql)); st->step(); } auto_ptr<Statement> prepare(const tstring& sql) const { return auto_ptr<Statement>(new Statement(db, sql)); } private: sqlite3* db; };

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• Making mercurial subrepositories behave like subversion externals

  - by Emily Dickinson

  Hi guys, The FAQ, and hginit.com have been really useful for helping me make the transition from svn to hg. However, when it comes to using Hg's subrepository feature in the manner of subversion's externals, I've tried everythign and cannot replicate the nice behavior of svn externals. Here's the simplest example of what I want to do: Init "lib" repository This repository is never to be used as a standalone; it's always included by main repositories, as a sub-repository. Init one or more including repositories To keep the example simple, I'll "init" a repository called "main" Have "main" include "lib" as a subrepository Importantly -- AND HERE'S WHAT I CAN'T GET TO WORK: When I modify a file inside of "main/lib", and I push the modification, then that change gets pushed to the "lib" repository -- NOT to a copy inside of "main". Command lines speak louder than words. I've tried so many variations on this theme, but here's the gist. If someone can reply, in command lines, I'll be forever grateful! 1. Init "lib" repository $ cd /home/moi/hgrepos ## Where I'm storing my hg repositories, on my main server $ hg init lib $ echo "foo" lib/lib.txt $ hg add lib $ hg ci -A -m "Init lib" lib 2. Init "main" repository, and include "lib" as a subrepos $ cd /home/moi/hgrepos $ hg init main $ echo "foo" main/main.txt $ hg add main $ cd main $ hg clone ../lib lib $ echo "lib=lib" .hgsub $ hg ci -A -m "Init main" . This all works fine, but when I make a clone of the "main" repository, and make local modifications to files in "main/lib", and push them, the changes get pushed to "main/lib", NOT to "lib". IN COMMAND-LINE-ESE, THIS IS THE PROBLEM: $ /home/moi/hg-test $ hg clone ssh://[email protected]/hgrepos/lib lib $ hg clone ssh://[email protected]/hgrepos/main main $ cd main $ echo foo lib/lib.txt $ hg st M lib.txt $ hg com -m "Modified lib.txt, from inside the main repos" lib.txt $ hg push pushing to ssh://[email protected]/hgrepos/main/lib That last line of output from hg shows the problem. It shows that I've made a modification to a COPY of a file in lib, NOT to a file in the lib repository. If this were working as I'd like it to work, the push would be to hgrepos/lib, NOT to hgrepos/main/lib. I.e., I would see: $ hg push pushing to ssh://[email protected]/hgrepos/lib IF YOU CAN ANSWER THIS IN TERMS OF COMMAND LINES RATHER THAN IN ENGLISH, I WILL BE ETERNALLY GRATEFUL! Thank you in advance! Emily in Portland

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• Problem with sqlite database on android platform

  - by mudit

  hi all i am developing an application which uses sqlite db for storing records. I am developing this application on SDK 1.5.. when i test the application on 1.5 device it works good but when i try to run it on a 1.6 device i get a force close message with following logcat output: 03-19 09:31:35.206: ERROR/AndroidRuntime(224): Uncaught handler: thread main exiting due to uncaught exception 03-19 09:31:35.226: ERROR/AndroidRuntime(224): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.abc.android/com.abc.android.app}: android.database.sqlite.SQLiteException: unable to open database file 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2454) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2470) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at android.app.ActivityThread.access$2200(ActivityThread.java:119) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1821) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at android.os.Handler.dispatchMessage(Handler.java:99) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at android.os.Looper.loop(Looper.java:123) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at android.app.ActivityThread.main(ActivityThread.java:4310) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at java.lang.reflect.Method.invokeNative(Native Method) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at java.lang.reflect.Method.invoke(Method.java:521) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at dalvik.system.NativeStart.main(Native Method) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): Caused by: android.database.sqlite.SQLiteException: unable to open database file 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at android.database.sqlite.SQLiteDatabase.dbopen(Native Method) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at android.database.sqlite.SQLiteDatabase.(SQLiteDatabase.java:1697) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:738) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:760) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:753) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at android.app.ApplicationContext.openOrCreateDatabase(ApplicationContext.java:473) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:193) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:98) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at com.abc.android.DbAdapter.open(DbAdapter.java:101) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at com.abc.android.class1.onCreate(class1.java:105) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2417) 03-19 09:31:35.226: ERROR/AndroidRuntime(224): ... 11 more DBAdapter.java public DbAdapter open() throws SQLException { Log.d("DbAdapter", "in DbAdapter open()"); mDbHelper = new DatabaseHelper(mCtx); mDb = mDbHelper.getWritableDatabase(); // line 101 return this; } DatabaseHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); } @Override public void onCreate(SQLiteDatabase db) { db.execSQL(DATABASE_QUERY); } class1.java mDB = new DbAdapter(Class1.this); mDB.open(); // line 105 Please help..what do i do????

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• Python: How to read huge text file into memory

  - by asmaier

  I'm using Python 2.6 on a Mac Mini with 1GB RAM. I want to read in a huge text file $ ls -l links.csv; file links.csv; tail links.csv -rw-r--r-- 1 user user 469904280 30 Nov 22:42 links.csv links.csv: ASCII text, with CRLF line terminators 4757187,59883 4757187,99822 4757187,66546 4757187,638452 4757187,4627959 4757187,312826 4757187,6143 4757187,6141 4757187,3081726 4757187,58197 So each line in the file consists of a tuple of two comma separated integer values. I want to read in the whole file and sort it according to the second column. I know, that I could do the sorting without reading the whole file into memory. But I thought for a file of 500MB I should still be able to do it in memory since I have 1GB available. However when I try to read in the file, Python seems to allocate a lot more memory than is needed by the file on disk. So even with 1GB of RAM I'm not able to read in the 500MB file into memory. My Python code for reading the file and printing some information about the memory consumption is: #!/usr/bin/python # -*- coding: utf-8 -*- import sys infile=open("links.csv", "r") edges=[] count=0 #count the total number of lines in the file for line in infile: count=count+1 total=count print "Total number of lines: ",total infile.seek(0) count=0 for line in infile: edge=tuple(map(int,line.strip().split(","))) edges.append(edge) count=count+1 # for every million lines print memory consumption if count%1000000==0: print "Position: ", edge print "Read ",float(count)/float(total)*100,"%." mem=sys.getsizeof(edges) for edge in edges: mem=mem+sys.getsizeof(edge) for node in edge: mem=mem+sys.getsizeof(node) print "Memory (Bytes): ", mem The output I got was: Total number of lines: 30609720 Position: (9745, 2994) Read 3.26693612356 %. Memory (Bytes): 64348736 Position: (38857, 103574) Read 6.53387224712 %. Memory (Bytes): 128816320 Position: (83609, 63498) Read 9.80080837067 %. Memory (Bytes): 192553000 Position: (139692, 1078610) Read 13.0677444942 %. Memory (Bytes): 257873392 Position: (205067, 153705) Read 16.3346806178 %. Memory (Bytes): 320107588 Position: (283371, 253064) Read 19.6016167413 %. Memory (Bytes): 385448716 Position: (354601, 377328) Read 22.8685528649 %. Memory (Bytes): 448629828 Position: (441109, 3024112) Read 26.1354889885 %. Memory (Bytes): 512208580 Already after reading only 25% of the 500MB file, Python consumes 500MB. So it seem that storing the content of the file as a list of tuples of ints is not very memory efficient. Is there a better way to do it, so that I can read in my 500MB file into my 1GB of memory?

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• iPhone UIWebView: loadData does not work with certain types (Excel, MSWord, PPT, RTF)

  - by Thomas Tempelmann

  My task is to display the supported document types on an iPhone with OS 3.x, such as .pdf, .rtf, .doc, .ppt, .png, .tiff etc. Now, I have stored these files only encrypted on disk. For security reasons, I want to avoid storing them unencrypted on disk. Hence, I prefer to use loadData:MIMEType:textEncodingName:baseURL: instead of loadRequest: to display the document because loadData allows me to pass the content in a NSData object, i.e. I can decrypt the file in memory and have no need to store it on disk, as it would be required when using loadRequest. The problem is that loadData does not appear to work with all file types: Testing shows that all picture types seem to work fine, as well as PDFs, while the more complex types don't. I get a errors such as: NSURLErrorDomain Code=100 NSURLErrorDomain Code=102 WebView appears to need a truly working URL for accessing the documents as a file, despite me offering all content via the NSData object already. Here's the code I use to display the content: [webView loadData:data MIMEType:type textEncodingName:@"utf-8" baseURL:nil]; The mime-type is properly set, e.g. to "application/msword" for .doc files. Does anyone know how I could get loadData to work with all types that loadRequest supports? Or, alternatively, is there some way I can tell which types do work for sure (i.e. officially sanctioned by Apple) with loadData? Then I can work twofold, creating a temp unencrypted file only for those cases that loadData won't like. Update Looks like I'm not the first one running into this. See here: http://osdir.com/ml/iPhoneSDKDevelopment/2010-03/msg00216.html So, I guess, that's the status quo, and nothing I can do about it. Someone suggested a work-around which might work, though: http://osdir.com/ml/iPhoneSDKDevelopment/2010-03/msg00219.html Basically, the idea is to provide a tiny http server that serves the file (from memory in my case), and then use loadRequest. This is probably a bit more memory-intensive, though, as both the server and the webview will probably both hold the entire contents in memory as two copies then, as opposed to using loadData, where both would rather share the same data object. (Mind you, I'll have to hold the decrypted data in memory, that's the whole point here).

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• TVirtualStringTree - resetting non-visual nodes and memory consumption

  - by Remy Lebeau - TeamB

  I have an app that loads records from a binary log file and displays them in a virtual TListView. There are potentially millions of records in a file, and the display can be filtered by the user, so I do not load all of the records in memory at one time, and the ListView item indexes are not a 1-to-1 relation with the file record offsets (List item 1 may be file record 100, for instance). I use the ListView's OnDataHint event to load records for just the items the ListView is actually interested in. As the user scrolls around, the range specified by OnDataHint changes, allowing me to free records that are not in the new range, and allocate new records as needed. This works fine, speed is tolerable, and the memory footprint is very low. I am currently evaluating TVirtualStringTree as a replacement for the TListView, mainly because I want to add the ability to expand/collapse records that span multiple lines (I can fudge it with the TListView by incrementing/decrementing the item count dynamically, but this is not as straight forward as using a real tree). For the most part, I have been able to port the TListView logic and have everything work as I need. I notice that TVirtualStringTree's virtual paradigm is vastly different, though. It does not have the same kind of OnDataHint functionality that TListView does (I can use the OnScroll event to fake it, which allows my memory buffer logic to continue working), and I can use the OnInitializeNode event to associate nodes with records that are allocated. However, once a tree node is initialized, it sees that it remains initialized for the lifetime of the tree. That is not good for me. As the user scrolls around and I remove records from memory, I need to reset those non-visual nodes without removing them from the tree completely, or losing their expand/collapse states. When the user scrolls them back into view, I can re-allocate the records and re-initialize the nodes. Basically, I want to make TVirtualStringTree act as much like TListView as possible, as far as its virtualization is concerned. I have seen that TVirtualStringTree has a ResetNode() method, but I encounter various errors whenever I try to use it. I must be using it wrong. I also thought of just storing a data pointer inside each node to my record buffers, and I allocate and free memory, update those pointers accordingly. The end effect does not work so well, either. Worse, my largest test log file has ~5 million records in it. If I initialize the TVirtualStringTree with that many nodes at one time (when the log display is unfiltered), the tree's internal overhead for its nodes takes up a whopping 260MB of memory (without any records being allocated yet). Whereas with the TListView, loading the same log file and all the memory logic behind it, I can get away with using just a few MBs. Any ideas?

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• Authorizing a computer to access a web application

  - by HackedByChinese

  I have a web application, and am tasked with adding secure sign-on to bolster security, akin to what Google has added to Google accounts. Use Case Essentially, when a user logs in, we want to detect if the user has previously authorized this computer. If the computer has not been authorized, the user is sent a one-time password (via email, SMS, or phone call) that they must enter, where the user may choose to remember this computer. In the web application, we will track authorized devices, allowing users to see when/where they logged in from that device last, and deauthorize any devices if they so choose. We require a solution that is very light touch (meaning, requiring no client-side software installation), and works with Safari, Chrome, Firefox, and IE 7+ (unfortunately). We will offer x509 security, which provides adequate security, but we still need a solution for customers that can't or won't use x509. My intention is to store authorization information using cookies (or, potentially, using local storage, degrading to flash cookies, and then normal cookies). At First Blush Track two separate values (local data or cookies): a hash representing a secure sign-on token, as well as a device token. Both values are driven (and recorded) by the web application, and dictated to the client. The SSO token is dependent on the device as well as a sequence number. This effectively allows devices to be deauthorized (all SSO tokens become invalid) and mitigates replay (not effectively, though, which is why I'm asking this question) through the use of a sequence number, and uses a nonce. Problem With this solution, it's possible for someone to just copy the SSO and device tokens and use in another request. While the sequence number will help me detect such an abuse and thus deauthorize the device, the detection and response can only happen after the valid device and malicious request both attempt access, which is ample time for damage to be done. I feel like using HMAC would be better. Track the device, the sequence, create a nonce, timestamp, and hash with a private key, then send the hash plus those values as plain text. Server does the same (in addition to validating the device and sequence) and compares. That seems much easier, and much more reliable.... assuming we can securely negotiate, exchange, and store private keys. Question So then, how can I securely negotiate a private key for authorized device, and then securely store that key? Is it more possible, at least, if I settle for storing the private key using local storage or flash cookies and just say it's "good enough"? Or, is there something I can do to my original draft to mitigate the vulnerability I describe?

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• DevExpress Reporting Session Issue

  - by LeeHull

  This is pretty complicated so I will explain what is going on. I have created an ASP.NET website for displaying images, the way we use our images is, we have a database table that contains the URL where the images are located, however we recently started moving them from the filesystem, and storing them directly into the database as binary, but since we don't want to break older applications, we currently store them both places till they are all updated. Alright, the website I'm working on, is just a reporting website to display images by a date range, I have created an HTTPHandler to display the image, depending if they exist in the database as binary, if the row is DBNull, I just grab the URL from the other table instead, I just read the image, convert it into a byte[] and write it to the response, so it is interpreted as an image. I have created a page to display the report using DevExpress Reporting, I just query the report, save the dataset into a session, and the report reads the session to bind the report, i also have a picturebox in the report bound to "Handler.ashx?id=ImageID", this is because I am not binding a URL to the image, since it is a byte[] Also since there could be a report with 10000+ images, I am reading the dataset from the session inside the handler and just pulling out the image from the passed in ImageID, I am doing this to prevent connecting to the database each and every row. Now the strange thing is, Report loads fine.. data is loading, I have paging on the devexpress report viewer, it is loading the images fine, however here is the issue. When I print or export, I am not getting any images, I am debugged and found out the Session.Count is 0 when it tries to print or export, which is strange since there is more than just the dataset in the session. I have also added IRequiresSessionState to allow sessions in the handler, but the session count is still 0, I have changing the Handler to an aspx page, same issue. Any ideas or suggestions on logic changes, I'm all ears.. this is a very difficult situation since I have to display the images from database as a string AND byte[] since one can be URL and other be the image bytes, but I also can't slam the database on connection calls each row either. I have also reported the issue to DevExpress and they are clueless as well, since they don't dispose the session in the exporting process.

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• C# or C++ game: many 16 color images loaded into RAM. Efficient solution?

  - by user560639

  I am in the planning stages of creating a fighting game and am unsure how to handle one issue relating to memory. Background info: - Still debating whether to use C# (XNA) or C++. We do not want to commit to either until we have explored how to solve this problem in both languages. - Using a max of 256MB RAM would be great if possible. - Two characters will be present at a time, and these characters can only change between battles. There is time to load/free memory between battles, but the game needs to run at a constant 60 drawn frames per second during combat. Each frame is 16.67ms - The total number of images per character is in the low hundreds. Each image is roughly 200x400 pixels. Only one image from each character will be displayed at any given moment. Uncompressed, each image takes roughly 300kb from my calculations; upwards of 100MB for a whole character. This is pushing too close to the 256MB limit given that memory will be needed for some other resources as well. Since each image can be made with a total of 16 colors. Theoretically I should be able to use 1/8th the space if I can take advantage of this. I've looked around but haven't found any word of native support for paletted images. (Storing each pixel using fewer bits that each map to a 32-bit RGBa color) I was considering making my own file format with 4 bits per pixel (and some extra palette info), loading all the images of this new format into RAM before battle, and then when drawing any specific image, decompress only that image into a raw image so it can be rendered properly. I don't know if it's realistic to perform so many assignment operations (appx 200x400 for each character = 160k) each frame. It sounds very hacky to me. Does anyone have advice on whether my solution sounds reasonable, and if there is perhaps a better one available? Thanks so much! (I also attempted to use an image with only 1 channel, then use a shader to perform a series of if statements to translate various values into other colors. Unfortunately, there were too many lines of code for the shader. It is also rather hacky and does not scale well.)

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• user generated / user specific functions

  - by pedalpete

  I'm looking for the most elegant and secure method to do the following. I have a calendar, and groups of users. Users can add events to specific days on the calendar, and specify how long each event lasts for. I've had a few requests from users to add the ability for them to define that events of a specific length include a break, of a certain amount of time, or require that a specific amount of time be left between events. For example, if event is 2 hours, include a 20min break. for each event, require 30 minutes before start of next event. The same group that has asked for an event of 2 hours to include a 20 min break, could also require that an event 3 hours include a 30 minute break. In the end, what the users are trying to get is an elapsed time excluding breaks calculated for them. Currently I provide them a total elapsed time, but they are looking for a running time. However, each of these requests is different for each group. Where one group may want a 30 minute break during a 2 hour event, and another may want only 10 minutes for each 3 hour event. I was kinda thinking I could write the functions into a php file per group, and then include that file and do the calculations via php and then return a calculated total to the user, but something about that doesn't sit right with me. Another option is to output the groups functions to javascript, and have it run client-side, as I'm already returning the duration of the event, but where the user is part of more than one group with different rules, this seems like it could get rather messy. I currently store the start and end time in the database, but no 'durations', and I don't think I should be storing the calculated totals in the db, because if a group decides to change their calculations, I'd need to change it throughout the db. Is there a better way of doing this? I would just store the variables in mysql, but I don't see how I can then say to mysql to calculate based on those variables. I'm REALLY lost here. Any suggestions? I'm hoping somebody has done something similar and can provide some insight into the best direction. If it helps, my table contains eventid, user, group, startDate, startTime, endDate, endTime, type The json for the event which I return to the user is {"eventid":"'.$eventId.'", "user":"'.$userId.'","group":"'.$groupId.'","type":"'.$type.'","startDate":".$startDate.'","startTime":"'.$startTime.'","endDate":"'.$endDate.'","endTime":"'.$endTime.'","durationLength":"'.$duration.'", "durationHrs":"'.$durationHrs.'"} where for example, duration length is 2.5 and duration hours is 2:30.

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• Safely remove window subclassing?

  - by Vegard Larsen

  I am trying to subclass the currently focused window on a Windows system using a global CBT hook. This is related to what happens in this question, but the bug is different. What happens when this subclassing is in effect, is that Opera's (version 10.50) main window is prevented from displaying. Opera has a "splash screen" where you are required to click "Start" for the main window to show that appears after Opera has not shut down properly. Whenever this window pops up, Opera's main window won't show. If Opera was shut down properly, and this splash screen does not show, the main window displays as it should. HHOOK hHook; HWND hWndSubclass = 0; void SubclassWindow(HWND hWnd) { Unsubclass(); FARPROC lpfnOldWndProc = (FARPROC)SetWindowLongPtr(hWnd, GWLP_WNDPROC, (LPARAM)SubClassFunc); SetProp(hWnd, L"PROP_OLDWNDPROC", lpfnOldWndProc); hWndSubclass = hWnd; } void Unsubclass() { if (hWndSubclass != 0 && IsWindow(hWndSubclass)) { FARPROC lpfnOldWndProc = (FARPROC)GetProp(hWndSubclass, L"PROP_OLDWNDPROC"); RemoveProp(hWndSubclass, L"PROP_OLDWNDPROC"); SetWindowLongPtr(hWndSubclass, GWLP_WNDPROC, (LPARAM)lpfnOldWndProc); hWndSubclass = 0; } } static LRESULT CALLBACK SubClassFunc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) { if (message == WM_MOVING) { // do something irrelevant } else if (message == WM_DESTROY) { Unsubclass(); } FARPROC lpfnOldWndProc = (FARPROC)GetProp(hWndSubclass, L"PROP_OLDWNDPROC"); return CallWindowProc((WNDPROC)lpfnOldWndProc, hWndSubclass, message, wParam, lParam); } static LRESULT CALLBACK CBTProc(int nCode, WPARAM wParam, LPARAM lParam) { if (nCode == HCBT_SETFOCUS && hWndServer != NULL) { SubclassWindow((HWND)wParam); } if (nCode < 0) { return CallNextHookEx(hHook, nCode, wParam, lParam); } return 0; } BOOL APIENTRY DllMain( HINSTANCE hInstance, DWORD Reason, LPVOID Reserved ) { switch(Reason) { case DLL_PROCESS_ATTACH: hInst = hInstance; return TRUE; case DLL_PROCESS_DETACH: Unsubclass(); return TRUE; } return TRUE; } My suspicion is that Opera's main window is somehow already subclassed. I imagine the following is happening: The window is created with it's own basic WndProc, and is given focus My application subclasses the window, storing the original WndProc Opera subclasses its own window When the window loses focus, I restore the original WndProc, thus ignoring the second WndProc Can this really be the case? Are there any other explanations?

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• how to store xml structure in a persistence layer?

  - by fayer

  i wonder how i could store a xml structure in a persistence layer. cause the relational data looks like: <entity id="1000070"> <name>apple</name> <entities> <entity id="7002870"> <name>mac</name> <entities> <entity id="7002907"> <name>leopard</name> <entities> <entity id="7024080"> <name>safari</name> </entity> <entity id="7024701"> <name>finder</name> </entity> </entities> </entity> </entities> </entity> <entity id="7024080"> <name>iphone</name> <entities> <entity id="7024080"> <name>3g</name> </entity> <entity id="7024701"> <name>3gs</name> </entity> </entities> </entity> <entity id="7024080"> <name>ipad</name> </entity> </entities> </entity> as you can see, it has no static structure but a dynamical one. mac got 2 descendant levels while iphone got 1 and ipad got 0. i wonder how i could store this data the best way? what are my options. cause it seems impossible to store it in a mysql database due to this dynamical structure. is the only way to store it as a xml file then? is the speed of getting information (xpath/xquery/simplexml) from a xml file worse or greater than from mysql? what are the pros and cons? do i have other options? is storing information in xml files, suited for a lot of users accessing it at the same time? would be great with feedbacks!! thanks!

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• Interfacing HTTPBuilder and HTMLUnit... some code

  - by Misha Koshelev

  Ok, this isn't even a question: import com.gargoylesoftware.htmlunit.HttpMethod import com.gargoylesoftware.htmlunit.WebClient import com.gargoylesoftware.htmlunit.WebResponseData import com.gargoylesoftware.htmlunit.WebResponseImpl import com.gargoylesoftware.htmlunit.util.Cookie import com.gargoylesoftware.htmlunit.util.NameValuePair import static groovyx.net.http.ContentType.TEXT import java.io.File import java.util.logging.Logger import org.apache.http.impl.cookie.BasicClientCookie /** * HTTPBuilder class * * Allows Javascript processing using HTMLUnit * * @author Misha Koshelev */ class HTTPBuilder { /** * HTTP Builder - implement this way to avoid underlying logging output */ def httpBuilder /** * Logger */ def logger /** * Directory for storing HTML files, if any */ def saveDirectory=null /** * Index of current HTML file in directory */ def saveIdx=1 /** * Current page text */ def text=null /** * Response for processJavascript (Complex Version) */ def resp=null /** * URI for processJavascript (Complex Version) */ def uri=null /** * HttpMethod for processJavascript (Complex Version) */ def method=null /** * Default constructor */ public HTTPBuilder() { // New HTTPBuilder httpBuilder=new groovyx.net.http.HTTPBuilder() // Logging logger=Logger.getLogger(this.class.name) } /** * Constructor that allows saving output files for testing */ public HTTPBuilder(saveDirectory,saveIdx) { this() this.saveDirectory=saveDirectory this.saveIdx=saveIdx } /** * Save text and return corresponding XmlSlurper object */ public saveText() { if (saveDirectory) { def file=new File(saveDirectory.toString()+File.separator+saveIdx+".html") logger.finest "HTTPBuilder.saveText: file=\""+file.toString()+"\"" file<<text saveIdx++ } new XmlSlurper(new org.cyberneko.html.parsers.SAXParser()).parseText(text) } /** * Wrapper around supertype get method */ public Object get(Map<String,?> args) { logger.finer "HTTPBuilder.get: args=\""+args+"\"" args.contentType=TEXT httpBuilder.get(args) { resp,reader-> text=reader.text this.resp=resp this.uri=args.uri this.method=HttpMethod.GET saveText() } } /** * Wrapper around supertype post method */ public Object post(Map<String,?> args) { logger.finer "HTTPBuilder.post: args=\""+args+"\"" args.contentType=TEXT httpBuilder.post(args) { resp,reader-> text=reader.text this.resp=resp this.uri=args.uri this.method=HttpMethod.POST saveText() } } /** * Load cookies from specified file */ def loadCookies(file) { logger.finer "HTTPBuilder.loadCookies: file=\""+file.toString()+"\"" file.withObjectInputStream { ois-> ois.readObject().each { cookieMap-> def cookie=new BasicClientCookie(cookieMap.name,cookieMap.value) cookieMap.remove("name") cookieMap.remove("value") cookieMap.entrySet().each { entry-> cookie."${entry.key}"=entry.value } httpBuilder.client.cookieStore.addCookie(cookie) } } } /** * Save cookies to specified file */ def saveCookies(file) { logger.finer "HTTPBuilder.saveCookies: file=\""+file.toString()+"\"" def cookieMaps=new ArrayList(new LinkedHashMap()) httpBuilder.client.cookieStore.getCookies().each { cookie-> def cookieMap=[:] cookieMap.version=cookie.version cookieMap.name=cookie.name cookieMap.value=cookie.value cookieMap.domain=cookie.domain cookieMap.path=cookie.path cookieMap.expiryDate=cookie.expiryDate cookieMaps.add(cookieMap) } file.withObjectOutputStream { oos-> oos.writeObject(cookieMaps) } } /** * Process Javascript using HTMLUnit (Simple Version) */ def processJavascript() { logger.finer "HTTPBuilder.processJavascript (Simple)" def webClient=new WebClient() def tempFile=File.createTempFile("HTMLUnit","") tempFile<<text def page=webClient.getPage("file://"+tempFile.toString()) webClient.waitForBackgroundJavaScript(10000) text=page.asXml() webClient.closeAllWindows() tempFile.delete() saveText() } /** * Process Javascript using HTMLUnit (Complex Version) * Closure, if specified, used to determine presence of necessary elements */ def processJavascript(closure) { logger.finer "HTTPBuilder.processJavascript (Complex)" // Convert response headers def headers=new ArrayList() resp.allHeaders.each() { header-> headers.add(new NameValuePair(header.name,header.value)) } def responseData=new WebResponseData(text.bytes,resp.statusLine.statusCode,resp.statusLine.toString(),headers) def response=new WebResponseImpl(responseData,uri.toURL(),method,0) // Transfer cookies def webClient=new WebClient() httpBuilder.client.cookieStore.getCookies().each { cookie-> webClient.cookieManager.addCookie(new Cookie(cookie.domain,cookie.name,cookie.value,cookie.path,cookie.expiryDate,cookie.isSecure())) } def page=webClient.loadWebResponseInto(response,webClient.getCurrentWindow()) // Wait for condition if (closure) { for (i in 1..20) { if (closure(page)) { break; } synchronized(page) { page.wait(500); } } } // Return text text=page.asXml() webClient.closeAllWindows() saveText() } } Allows one to interface HTTPBuilder with HTMLUnit! Enjoy Misha

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• TVirtualStringTree - resetting non-visual nodes and memory comsumption

  - by Remy Lebeau - TeamB

  I have an app that loads records from a binary log file and displays them in a virtual TListView. There are potentially millions of records in a file, and the display can be filtered by the user, so I do not load all of the records in memory at one time, and the ListView item indexes are not a 1-to-1 relation with the file record offsets (List item 1 may be file record 100, for instance). I use the ListView's OnDataHint event to load records for just the items the ListView is actually interested in. As the user scrolls around, the range specified by OnDataHint changes, allowing me to free records that are not in the new range, and allocate new records as needed. This works fine, speed is tolerable, and the memory footprint is very low. I am currently evaluating TVirtualStringTree as a replacement for the TListView, mainly because I want to add the ability to expand/collapse records that span multiple lines (I can fudge it with the TListView by incrementing/decrementing the item count dynamically, but this is not as straight forward as using a real tree). For the most part, I have been able to port the TListView logic and have everything work as I need. I notice that TVirtualStringTree's virtual paridigm is vastly different, though. It does not have the same kind of OnDataHint functionality that TListView does (I can use the OnScroll event to fake it, which allows my memory buffer logic to continue working), and I can use the OnInitializeNode event to associate nodes with records that are allocated. However, once a tree node is initialized, it sees that it remains initialized for the lifetime of the tree. That is not good for me. As the user scrolls around and I remove records from memory, I need to reset those non-visual nodes without removing them from the tree completely, or losing their expand/collapse states. When the user scrolls them back into view, I can re-allocate the records and re-initialize the nodes. Basically, I want to make TVirtualStringTree act as much like TListView as possible, as far as its virtualization is concerned. I have seen that TVirtualStringTree has a ResetNode() method, but I encounter various errors whenever I try to use it. I must be using it wrong. I also thought of just storing a data pointer inside each node to my record buffers, and I allocate and free memory, update those pointers accordingly. The end effect does not work so well, either. Worse, my largest test log file has ~5 million records in it. If I initialize the TVirtualStringTree with that many nodes at one time (when the log display is unfiltered), the tree's internal overhead for its nodes takes up a whopping 260MB of memory (without any records being allocated yet). Whereas with the TListView, loading the same log file and all the memory logic behind it, I can get away with using just a few MBs. Any ideas?

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• find words in a hashset or treeset?

  - by icelated

  I am piping in a file and storing it into a treeset. I am trying to count unique words.. I am placing words that i dont want into a hashset. "a","the", "and" I want to check to see if the file contains those words, before i place them into the TreeSet.. i know i need some sort of if(word == find) ? i just dont know how to do it.. Sorry about formatting. its hard to get it correct after you paste. this is what i have.. import java.util.Scanner; import java.util.ArrayList; import java.util.TreeSet; import java.util.Iterator; import java.util.HashSet; public class Project1 { public static void main(String[] args) { Scanner sc = new Scanner(System.in); String word; String grab; int count = 0; int count2 =0; int count3 =0; int count4 =0; int number; TreeSet<String> a = new TreeSet<String>(); HashSet<String> find = new HashSet<String>(); System.out.println("Project 1\n"); find.add("a"); find.add("and"); find.add("the"); while (sc.hasNext()) { word = sc.next(); word = word.toLowerCase(); for(int i = 0; i < word.length(); i++ ) { if(Character.isDigit(word.charAt(i))) { count3++; } } //if( a.contains("a") ) //|| word.matches("and") || word.matches("the")|| word.contains("$")) //{ // count2++; // } a.add(word); if (word.equals("---")) { break; } } System.out.println("a size"); System.out.println(a.size()); // count = count2 - count; System.out.println("unique words"); System.out.println(a.size() - count2 - count3); System.out.println("\nbye..."); } }

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