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• Music Notation Editor - Refactoring view creation logic elsewhere

  - by Cyril Silverman

  Let me preface by saying that knowing some elementary music theory and music notation may be helpful in grasping the problem at hand. I'm currently building a Music Notation and Tablature Editor (in Javascript). But I've come to a point where the core parts of the program are more or less there. All functionality I plan to add at this point will really build off the foundation that I've created. As a result, I want to refactor to really solidify my code. I'm using an API called VexFlow to render notation. Basically I pass the parts of the editor's state to VexFlow to build the graphical representation of the score. Here is a rough and stripped down UML diagram showing you the outline of my program: In essence, a Part has many Measures which has many Notes which has many NoteItems (yes, this is semantically weird, as a chord is represented as a Note with multiple NoteItems, individual pitches or fret positions). All of the relationships are bi-directional. There are a few problems with my design because my Measure class contains the majority of the entire application view logic. The class holds the data about all VexFlow objects (the graphical representation of the score). It contains the graphical Staff object and the graphical notes. (Shouldn't these be placed somewhere else in the program?) While VexFlowFactory deals with actual creation (and some processing) of most of the VexFlow objects, Measure still "directs" the creation of all the objects and what order they are supposed to be created in for both the VexFlowStaff and VexFlowNotes. I'm not looking for a specific answer as you'd need a much deeper understanding of my code. Just a general direction to go in. Here's a thought I had, create an MeasureView/NoteView/PartView classes that contains the basic VexFlow objects for each class in addition to any extraneous logic for it's creation? but where would these views be contained? Do I create a ScoreView that is a parallel graphical representation of everything? So that ScoreView.render() would cascade down PartView and call render for each PartView and casade down into each MeasureView, etc. Again, I just have no idea what direction to go in. The more I think about it, the more ways to go seem to pop into my head. I tried to be as concise and simplistic as possible while still getting my problem across. Please feel free to ask me any questions if anything is unclear. It's quite a struggle trying to dumb down a complicated problem to its core parts.

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• Part 1: What are EBS Customizations?

  - by volker.eckardt(at)oracle.com

  Everything what is not shipped as Oracle standard may be called customization. And very often we differentiate between setup and customization, although setup can also be required when working with customizations.This highlights one of the first challenges, because someone needs to track setup brought over with customizations and this needs to be synchronized with the (standard) setup done manually. This is not only a tracking issue, but also a documentation issue. I will cover this in one of the following blogs in more detail.But back to the topic itself. Mainly our code pieces (java, pl/sql, sql, shell scripts), custom objects (tables, views, packages etc.) and application objects (concurrent programs, lookups, forms, reports, OAF pages etc.) are treated as customizations. In general we define two types: customization by extension and customization by modification. For sure we like to minimize standard code modifications, but sometimes it is just not possible to provide a certain functionality without doing it.Keep in mind that the EBS provides a number of alternatives for modifications, just to mention some:Files in file system    add your custom top before the standard top to the pathBI Publisher Report    add a custom layout and disable the standard layout, automatically yours will be taken.Form /OAF Change    use personalization or substitutionUsing such techniques you are on the safe site regarding standard patches, but for sure a retest is always required!Many customizations are growing over the time, initially it was just one file, but in between we have 5, 10 or 15 files in our customization pack. The more files you have, the more important is the installation order.Last but not least also personalization's are treated as customizations, although you may not use any deployment pack to transfer such personalisation's (but you can). For OAF personalization's you can use iSetup, I have also enabled iSetup to allow Forms personalizations to transport.Interfaces and conversion objects are quite often also categorized as customizations and I promote this decision. Your development standards are related to all these kinds of custom code whether we are exchanging data with users (via form or report) or with other systems (via inbound or outbound interface).To cover all these types of customizations two acronyms have been defined: RICE and CEMLI.RICE = Reports, Interfaces, Conversions, and ExtensionsCEMLI = Customization, Extension, Modification, Localization, IntegrationThe word CEMLI has been introduced by Oracle On Demand and is used within Oracle projects quite often, but also RICE is well known as acronym.It doesn't matter which acronym you are using, the main task here is to classify and categorize your customizations to allow everyone to understand when you talk about RICE- 211, CEMLI XXFI_BAST or XXOM_RPT_030.Side note: Such references are not automatically objects prefixes, but they are often used as such. I plan also to address this point in one other blog.Thank you!Volker

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• Hype and LINQ

  - by Tony Davis

  "Tired of querying in antiquated SQL?" I blinked in astonishment when I saw this headline on the LinqPad site. Warming to its theme, the site suggests that what we need is to "kiss goodbye to SSMS", and instead use LINQ, a modern query language! Elsewhere, there is an article entitled "Why LINQ beats SQL". The designers of LINQ, along with many DBAs, would, I'm sure, cringe with embarrassment at the suggestion that LINQ and SQL are, in any sense, competitive ways of doing the same thing. In fact what LINQ really is, at last, is an efficient, declarative language for C# and VB programmers to access or manipulate data in objects, local data stores, ORMs, web services, data repositories, and, yes, even relational databases. The fact is that LINQ is essentially declarative programming in a .NET language, and so in many ways encourages developers into a "SQL-like" mindset, even though they are not directly writing SQL. In place of imperative logic and loops, it uses various expressions, operators and declarative logic to build up an "expression tree" describing only what data is required, not the operations to be performed to get it. This expression tree is then parsed by the language compiler, and the result, when used against a relational database, is a SQL string that, while perhaps not always perfect, is often correctly parameterized and certainly no less "optimal" than what is achieved when a developer applies blunt, imperative logic to the SQL language. From a developer standpoint, it is a mistake to consider LINQ simply as a substitute means of querying SQL Server. The strength of LINQ is that that can be used to access any data source, for which a LINQ provider exists. Microsoft supplies built-in providers to access not just SQL Server, but also XML documents, .NET objects, ADO.NET datasets, and Entity Framework elements. LINQ-to-Objects is particularly interesting in that it allows a declarative means to access and manipulate arrays, collections and so on. Furthermore, as Michael Sorens points out in his excellent article on LINQ, there a whole host of third-party LINQ providers, that offers a simple way to get at data in Excel, Google, Flickr and much more, without having to learn a new interface or language. Of course, the need to be generic enough to deal with a range of data sources, from something as mundane as a text file to as esoteric as a relational database, means that LINQ is a compromise and so has inherent limitations. However, it is a powerful and beautifully compact language and one that, at least in its "query syntax" guise, is accessible to developers and DBAs alike. Perhaps there is still hope that LINQ can fulfill Phil Factor's lobster-induced fantasy of a language that will allow us to "treat all data objects, whether Word files, Excel files, XML, relational databases, text files, HTML files, registry files, LDAPs, Outlook and so on, in the same logical way, as linked databases, and extract the metadata, create the entities and relationships in the same way, and use the same SQL syntax to interrogate, create, read, write and update them." Cheers, Tony.

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• What is the best practice for when to check if something needs to be done?

  - by changokun

  Let's say I have a function that does x. I pass it a variable, and if the variable is not null, it does some action. And I have an array of variables and I'm going to run this function on each one. Inside the function, it seems like a good practice is to check if the argument is null before proceeding. A null argument is not an error, it just causes an early return. I could loop through the array and pass each value to the function, and the function will work great. Is there any value to checking if the var is null and only calling the function if it is not null during the loop? This doubles up on the checking for null, but: Is there any gained value? Is there any gain on not calling a function? Any readability gain on the loop in the parent code? For the sake of my question, let's assume that checking for null will always be the case. I can see how checking for some object property might change over time, which makes the first check a bad idea. Pseudo code example: for(thing in array) { x(thing) } Versus: for(thing in array) { if(thing not null) x(thing) } If there are language-specific concerns, I'm a web developer working in PHP and JavaScript.

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• Extending Currying: Partial Functions in Javascript

  - by kerry

  Last week I posted about function currying in javascript.  This week I am taking it a step further by adding the ability to call partial functions. Suppose we have a graphing application that will pull data via Ajax and perform some calculation to update a graph.  Using a method with the signature ‘updateGraph(id,value)’. To do this, we have do something like this: 1: for(var i=0;i<objects.length;i++) { 2: Ajax.request('/some/data',{id:objects[i].id},function(json) { 3: updateGraph(json.id, json.value); 4: } 5: } This works fine.  But, using this method we need to return the id in the json response from the server.  This works fine, but is not that elegant and increase network traffic. Using partial function currying we can bind the id parameter and add the second parameter later (when returning from the asynchronous call).  To do this, we will need the updated curry method.  I have added support for sending additional parameters at runtime for curried methods. 1: Function.prototype.curry = function(scope) { 2: scope = scope || window 3: var args = []; 4: for (var i=1, len = arguments.length; i < len; ++i) { 5: args.push(arguments[i]); 6: } 7: var m = this; 8: return function() { 9: for (var i=0, len = arguments.length; i < len; ++i) { 10: args.push(arguments[i]); 11: } 12: return m.apply(scope, args); 13: }; 14: } To partially curry this method we will call the curry method with the id parameter, then the request will callback on it with just the value.  Any additional parameters are appended to the method call. 1: for(var i=0;i<objects.length;i++) { 2: var id=objects[i].id; 3: Ajax.request('/some/data',{id: id}, updateGraph.curry(id)); 4: } As you can see, partial currying gives is a very useful tool and this simple method should be a part of every developer’s toolbox.

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• Drawing multiple Textures as tilemap

  - by DocJones

  I am trying to draw a 2d game map and the objects on the map in a single pass. Here is my OpenGL initialization code // Turn off unnecessary operations glDisable(GL_DEPTH_TEST); glDisable(GL_LIGHTING); glDisable(GL_CULL_FACE); glDisable(GL_STENCIL_TEST); glDisable(GL_DITHER); glEnable(GL_BLEND); glEnable(GL_TEXTURE_2D); // activate pointer to vertex & texture array glEnableClientState(GL_VERTEX_ARRAY); glEnableClientState(GL_TEXTURE_COORD_ARRAY); My drawing code is being called by a NSTimer every 1/60 s. Here is the drawing code of my world object: - (void) draw:(NSRect)rect withTimedDelta:(double)d { GLint *t; glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, [_textureManager textureByName:@"blocks"]); glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE); for (int x=0; x<[_map getWidth] ; x++) { for (int y=0; y<[_map getHeight] ; y++) { GLint v[] = { 16*x ,16*y, 16*x+16,16*y, 16*x+16,16*y+16, 16*x ,16*y+16 }; t=[_textureManager getBlockWithNumber:[_map getBlockAtX:x andY:y]]; glVertexPointer(2, GL_INT, 0, v); glTexCoordPointer(2, GL_INT, 0, t); glDrawArrays(GL_QUADS, 0, 4); } } } (_textureManager is a Singelton only loading a texture once!) The object drawing codes is identical (except the nested loops) in terms of OpenGL calls: - (void) drawWithTimedDelta:(double)d { GLint *t; GLint v[] = { 16*xpos ,16*ypos, 16*xpos+16,16*ypos, 16*xpos+16,16*ypos+16, 16*xpos ,16*ypos+16 }; glBindTexture(GL_TEXTURE_2D, [_textureManager textureByName:_textureName]); t=[_textureManager getBlockWithNumber:12]; glVertexPointer(2, GL_INT, 0, v); glTexCoordPointer(2, GL_INT, 0, t); glDrawArrays(GL_QUADS, 0, 4); } As soon as my central drawing routine calls the two drawing methods the second call overlays the first one. i would expect the call to world.draw to draw the map and "stamp" the objects upon it. Debugging shows me, that the first call is performed correctly (world is being drawn), but the following call to all objects ONLY draws the objects, the rest of the scene is getting black. I think i need to blend the drawn textures, but i cant seem to figure out how. Any help is appreciated. Thanks PS: Here is the github link to the project. It may not be in sync of my post here, but for some more in-depth analysis it may help.

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• Are factors such as Intellisense support and strong typing enough to justify the use of an 'Anaemic Domain Model'?

  - by David Osborne

  It's easy to accept that objects should be used in all layers except a layer nominated as a data layer. However, it's just as easy to end-up with an 'anaemic domain model' that is just an object representation of data with no real functionality ( http://martinfowler.com/bliki/AnemicDomainModel.html ). However, using objects in this fashion brings the benefit of factors such as Intellisense support, strong typing, readability, discoverability, etc. Are these factors strong arguments for an otherwise, anaemic domain model?

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• Installing Windows on HP Proliant Servers without SmartStart

  - by Fitzroy

  I have a PXE server for deploying Windows XP and Windows 7 to workstations. The process is as follows: Boot the workstation from the NIC. Workstation sends a DHCP request. DHCP server responds with an IP address and the location of the PXE server. Workstation downloads WinPE image file from PXE server via TFTP Workstation stores WinPE image file in memory and executes it. Once booted into WinPE, I connect to a network share to gain access to either the Windows XP or Windows 7 installation files. A custom script is launched to guide you through the process of formatting and partitioning the hard drive(s) (using DISKPART and FORMAT). Another custom script asks for details such as the hostname to assign to the workstation. The answers provided are used to build an unattended answer file (SIF [Setup Information File] for WinXP and XML for Win7). The Windows setup EXE is launched, passing the unattended answer file to it as a parameter. The Windows XP and Windows 7 installation sources have been customised to include the drivers for our Dell workstations. They also run a number of scripts upon first booting up to install software packages. This process works very well for our workstations and I would now like to use it for building our servers too. The vast majority of our servers are HP Proliant DL360 G6, DL380 G5 and DL380 G6. They’re running Windows Server 2003 (various editions) or 2008 (various editions). To date, we have always built the HP Proliant servers using the SmartStart CD provided. SmartStart does three useful things for us: Setup RAID with HP Array Configuration Utility (ACU). Installs and configures SNMP Installs various HP Tools for Windows (HP Array Configuration Utility, HP Array Diagnostic Utility, HP Proliant Integrated Management Log Viewer, etc) Using SmartStart I have never had to manually download and install Windows drivers for network, sound, video, etc. I'm not sure if this is because SmartStart copies drivers from the CD during setup, or whether Windows just has the drivers natively in its driver CAB. If I abandon the SmartStart CD in favour of my PXE server I would have to do the following: As I wont have access to ACU, I'll configure the RAID (before booting to the PXE server) by pressing F8 (during the boot process) to access Option ROM Configuration for Arrays (ORCA). Installation of SNMP and the HP Tools will have to be installed once the Windows installation is complete using the Proliant Support Pack. Is this method OK? Is there anything that the SmartStart CD does that I'll be unable to do by other means? Are there any disadvantages to not using the SmartStart CD? Many thanks. UPDATE 05/01/12 I’ve been reading through the SmartStart Scripting Toolkit documentation. The scripting toolkit contains command line tools which work within WinPE and can such things as configure BIOS settings, configure an array and setup ILO. I’m personally not too bothered about configuring BIOS settings as I rarely deviate from the defaults (unless the server is to be a Hyper-V host). I’m not too fussed about being able to configure the array from within WinPE, as I’m happy to just press F8 and use Option ROM Configuration for Arrays (ORCA). Although, if it’s easy enough to do, I will explore this further, as it saves time if everything can be configured from within WinPE. One of the nice features all the tools possess is that you can pass input files to them. EG. Configure one server to your requirements, capture its configuration to a file (using the appropriate tool), you can then use the tool on other servers passing the input file with the captured configuration. Array controller drivers appear to be included with the toolkit along with example of how to incorporate them within a WinPE build. I suppose WinPE won’t be able to see logical volumes (I.E 2x physical disks in a RAID 1 configuration) without the array controller drivers? I mentioned in my post that SmartStart normally installs a bunch of Windows HP tools for you. I’ve had a look today, and if you run the SmartStart CD from within Windows all the tools can be installed. Therefore I can do this after the Windows installation is complete. The SmartStart CD appears to contain a lot Windows drivers. I can customise my Windows 2008 source to incorporate these drivers. However, I understand that incorporating an array controller driver is a little different to most drivers. I believe that you have to provide the driver during the very early stages of the Windows setup. I’m working through the Scripting Toolkit documentation to try and work this out...

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• 12.04 grub unable to boot on /sde, upgrade-grub and boot-repair failed, please help

  - by VGR

  My problem is I've 4 disks in a raid array listed as sda, sdb... sdd and grub 2 refuses to boot on /sde (the 5th disk, standalone and containing a clean install of 12.04 64 bits). I tried all solutions but all fail. (live CD/USB with grub-setup, also tried repair-grub, and tried also in the "grub rescue" set prefix= etc). I also tried to deactivate the RAID array in the BIOS, but I'd rather not destroy it, and I didn't find a way to make the standalone disk as '/sda1' (this would satisfy grub). In the BIOS, the would-be /sda is the only bootable hard disk; it ends up as /sde and grubs complains. I've made repair-grub issue a pastebin. I always end up in grub-rescue and I'm stuck. I need Ubuntu to boot so that I can add the device array handler for my disks. I can't switch the disks and I can't disconnect the SATA RAID controller. I need: (a) a workaround so that grub starts on /sde; or (b) a way to change the order in which Ubuntu sees the disks, at boot time. I could then provide grub with a /sda1. Thanks a lot. up please thanks a lot it's not the same problem as booting ubuntu from raid. My RAID array serves only of data repository windows had no problem with this configuration

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• Cannot create zpool, how to get rid of intel raid volume?

  - by nagylzs

  This is a FreeBSD 9.1 amd64 computer. It has 5 disks installed. The ada0 and ada1 disks are used with a hw raid to provide the root filesystem: root@gw:/home/gandalf # ls /dev | grep ada ada0 ada1 ada2 ada3 ada4 root@gw:/home/gandalf # zpool status pool: zroot state: ONLINE scan: none requested config: NAME STATE READ WRITE CKSUM zroot ONLINE 0 0 0 raid/r0s1a ONLINE 0 0 0 errors: No known data errors I want to create a raidz pool for the remaining disks: root@gw:/home/gandalf # zpool create -f data raidz1 ada2 ada3 ada4 cannot create 'data': one or more devices is currently unavailable root@gw:/home/gandalf # dmesg | grep ada2 ada2 at ata4 bus 0 scbus6 target 0 lun 0 ada2: <WDC WD20EARS-00MVWB0 51.0AB51> ATA-8 SATA 2.x device ada2: 300.000MB/s transfers (SATA 2.x, UDMA5, PIO 8192bytes) ada2: 1907729MB (3907029168 512 byte sectors: 16H 63S/T 16383C) ada2: Previously was known as ad16 root@gw:/home/gandalf # dmesg | grep ada3 ada3 at ata5 bus 0 scbus7 target 0 lun 0 ada3: <SAMSUNG HD103UJ 1AA01118> ATA-7 SATA 2.x device ada3: 300.000MB/s transfers (SATA 2.x, UDMA5, PIO 8192bytes) ada3: 953868MB (1953523055 512 byte sectors: 16H 63S/T 16383C) ada3: Previously was known as ad18 GEOM_RAID: Intel-fb8732fa: Disk ada3 state changed from NONE to ACTIVE. GEOM_RAID: Intel-fb8732fa: Subdisk Volume0:0-ada3 state changed from NONE to ACTIVE. root@gw:/home/gandalf # dmesg | grep ada4 ada4 at ata6 bus 0 scbus8 target 0 lun 0 ada4: <TOSHIBA DT01ACA100 MS2OA750> ATA-8 SATA 3.x device ada4: 300.000MB/s transfers (SATA 2.x, UDMA5, PIO 8192bytes) ada4: 953869MB (1953525168 512 byte sectors: 16H 63S/T 16383C) ada4: Previously was known as ad20 root@gw:/home/gandalf # dmesg | grep GEOM_RAID Aha, so ada3 is already part of another raid volume? Let's see: root@gw:/home/gandalf # dmesg | grep GEOM_RAID GEOM_RAID: SiI-130628113902: Array SiI-130628113902 created. GEOM_RAID: SiI-130628113902: Disk ada0 state changed from NONE to ACTIVE. GEOM_RAID: SiI-130628113902: Subdisk SiI Raid1 Set:1-ada0 state changed from NONE to STALE. GEOM_RAID: SiI-130628113902: Disk ada1 state changed from NONE to ACTIVE. GEOM_RAID: SiI-130628113902: Subdisk SiI Raid1 Set:0-ada1 state changed from NONE to STALE. GEOM_RAID: SiI-130628113902: Array started. GEOM_RAID: SiI-130628113902: Subdisk SiI Raid1 Set:0-ada1 state changed from STALE to ACTIVE. GEOM_RAID: SiI-130628113902: Subdisk SiI Raid1 Set:1-ada0 state changed from STALE to RESYNC. GEOM_RAID: SiI-130628113902: Subdisk SiI Raid1 Set:1-ada0 rebuild start at 0. GEOM_RAID: SiI-130628113902: Volume SiI Raid1 Set state changed from STARTING to SUBOPTIMAL. GEOM_RAID: SiI-130628113902: Provider raid/r0 for volume SiI Raid1 Set created. GEOM_RAID: Intel-fb8732fa: Array Intel-fb8732fa created. GEOM_RAID: Intel-fb8732fa: Force array start due to timeout. GEOM_RAID: Intel-fb8732fa: Disk ada3 state changed from NONE to ACTIVE. GEOM_RAID: Intel-fb8732fa: Subdisk Volume0:0-ada3 state changed from NONE to ACTIVE. GEOM_RAID: Intel-fb8732fa: Array started. GEOM_RAID: Intel-fb8732fa: Volume Volume0 state changed from STARTING to DEGRADED. GEOM_RAID: Intel-fb8732fa: Provider raid/r1 for volume Volume0 created. root@gw:/home/gandalf # Yes, indeed. I want to get rid of raid/r1 completely. However, the controller was already set to "IDE" mode in the BIOS. So why it is creating a raid volume??? I have also tried overwritting the first 16k data of ada3 and reboot the computer, but it did not help. How can I delete /dev/raid/r1 ? root@gw:/home/gandalf # graid status Name Status Components raid/r0 SUBOPTIMAL ada0 (ACTIVE (RESYNC 4%)) ada1 (ACTIVE (ACTIVE)) raid/r1 DEGRADED ada3 (ACTIVE (ACTIVE)) root@gw:/home/gandalf # graid delete raid/r1 graid: Array 'raid/r1' not found. root@gw:/home/gandalf # graid delete /dev/raid/r1 graid: Array '/dev/raid/r1' not found. root@gw:/home/gandalf # Thanks

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• Map building - Tower Defense

  - by Dan K

  Before diving too deep into my question, let it be known that I am learning as far as java script goes and figured a simple Tower Defense game would be an excellent way to learn things. So I have found a simple background image with a path drawn on it and my question is how would I go about building a path so that I can animate my objects. Would I have to take the image and overlay a grid system, or can I store the path in some sort of array and have my objects move across it? Here is the background image:

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• Should main method be only consists of object creations and method calls?

  - by crucified soul

  A friend of mine told me that, the best practice is class containing main method should be named Main and only contains main method. Also main method should only parse inputs, create other objects and call other methods. The Main class and main method shouldn't do anything else. Basically what he is saying that class containing main method should be like: public class Main { public static void main(String[] args) { //parse inputs //create other objects //call methods } } Is it the best practice?

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• How to do geometric projection shadows?

  - by John Murdoch

  I have decided that since my game world is mostly flat I don't need better shadows than geometric projections - at least for now. The only problem is I don't even know how to do those properly - that is to produce a 4x4 matrix which would render shadows for my objects (that is, I guess, project them on a horizontal XZ plane). I would like a light source at infinity (e.g., the sun at some point in the sky) and thus parallel projection. My current code does something that looks almost right for small flying objects, but actually is a very rude approximation, as it doesn't project the objects onto the ground, but simply moves them there (I think). Also it always wrongly assumes the sun is always on the zenith (projecting straight down). Gdx.gl20.glEnable(GL10.GL_BLEND); Gdx.gl20.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA); //shells shellTexture.bind(); shader.begin(); for (ShellState state : shellStates.values()) { transform.set(camera.combined); transform.mul(state.transform); shader.setUniformMatrix("u_worldView", transform); shader.setUniformi("u_texture", 0); shellMesh.render(shader, GL10.GL_TRIANGLES); } shader.end(); // shadows shader.begin(); for (ShellState state : shellStates.values()) { transform.set(camera.combined); m4.set(state.transform); state.transform.getTranslation(v3); m4.translate(0, -v3.y + 0.5f, 0); // TODO HACK: + 0.5f is a hack to ensure the shadow appears above the ground; this is overall a hack as we are just moving the shell to the surface instead of projecting it on the surface! transform.mul(m4); shader.setUniformMatrix("u_worldView", transform); shader.setUniformi("u_texture", 0); // TODO: make shadow black somehow shellMesh.render(shader, GL10.GL_TRIANGLES); } shader.end(); Gdx.gl.glDisable(GL10.GL_BLEND); So my questions are: a) What is the proper way to produce a Matrix4 to pass to openGL which would render the shadows for my objects? b) I am supposed to use another fragment shader for the shadows which would paint them in semi-transparent grey, correct? c) The limitation of this simplistic approach is that whenever there is some object on the ground (it is not flat) the shadows will not be drawn, correct? d) Do I need to add something very small to the y (up) coordinate to avoid z-fighting with ground textures? Or is the fact they will be semi-transparent enough to resolve that problem?

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• Efficient Trie implementation for unicode strings

  - by U Mad

  I have been looking for an efficient String trie implementation. Mostly I have found code like this: Referential implementation in Java (per wikipedia) I dislike these implementations for mostly two reasons: They support only 256 ASCII characters. I need to cover things like cyrillic. They are extremely memory inefficient. Each node contains an array of 256 references, which is 4096 bytes on a 64 bit machine in Java. Each of these nodes can have up to 256 subnodes with 4096 bytes of references each. So a full Trie for every ASCII 2 character string would require a bit over 1MB. Three character strings? 256MB just for arrays in nodes. And so on. Of course I don't intend to have all of 16 million three character strings in my Trie, so a lot of space is just wasted. Most of these arrays are just null references as their capacity far exceeds the actual number of inserted keys. And if I add unicode, the arrays get even larger (char has 64k values instead of 256 in Java). Is there any hope of making an efficient trie for strings? I have considered a couple of improvements over these types of implementations: Instead of using array of references, I could use an array of primitive integer type, which indexes into an array of references to nodes whose size is close to the number of actual nodes. I could break strings into 4 bit parts which would allow for node arrays of size 16 at the cost of a deeper tree.

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• Discuss: PLs are characterised by which (iso)morphisms are implemented

  - by Yttrill

  I am interested to hear discussion of the proposition summarised in the title. As we know programming language constructions admit a vast number of isomorphisms. In some languages in some places in the translation process some of these isomorphisms are implemented, whilst others require code to be written to implement them. For example, in my language Felix, the isomorphism between a type T and a tuple of one element of type T is implemented, meaning the two types are indistinguishable (identical). Similarly, a tuple of N values of the same type is not merely isomorphic to an array, it is an array: the isomorphism is implemented by the compiler. Many other isomorphisms are not implemented for example there is an isomorphism expressed by the following client code: match v with | ((?x,?y),?z = x,(y,z) // Felix match v with | (x,y), - x,(y,z) (* Ocaml *) As another example, a type constructor C of int in Felix may be used directly as a function, whilst in Ocaml you must write a wrapper: let c x = C x Another isomorphism Felix implements is the elimination of unit values, including those in tuples: Felix can do this because (most) polymorphic values are monomorphised which can be done because it is a whole program analyser, Ocaml, for example, cannot do this easily because it supports separate compilation. For the same reason Felix performs type-class dispatch at compile time whilst Haskell passes around dictionaries. There are some quite surprising issues here. For example an array is just a tuple, and tuples can be indexed at run time using a match and returning a value of a corresponding sum type. Indeed, to be correct the index used is in fact a case of unit sum with N summands, rather than an integer. Yet, in a real implementation, if the tuple is an array the index is replaced by an integer with a range check, and the result type is replaced by the common argument type of all the constructors: two isomorphisms are involved here, but they're implemented partly in the compiler translation and partly at run time.

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• Music Notation Editor - Refactoring view creation logic elseware

  - by Cyril Silverman

  Let me preface by saying that knowing some elementary music theory and music notation may be helpful in grasping the problem at hand. I'm currently building a Music Notation and Tablature Editor (in Javascript). But I've come to a point where the core parts of the program are more or less there. All functionality I plan to add at this point will really build off the foundation that I've created. As a result, I want to refactor to really solidify my code. I'm using an API called VexFlow to render notation. Basically I pass the parts of the editor's state to VexFlow to build the graphical representation of the score. Here is a rough and stripped down UML diagram showing you the outline of my program: In essence, a Part has many Measures which has many Notes which has many NoteItems (yes, this is semantically weird, as a chord is represented as a Note with multiple NoteItems, individual pitches or fret positions). All of the relationships are bi-directional. There are a few problems with my design because my Measure class contains the majority of the entire application view logic. The class holds the data about all VexFlow objects (the graphical representation of the score). It contains the graphical Staff object and the graphical notes. (Shouldn't these be placed somewhere else in the program?) While VexFlowFactory deals with actual creation (and some processing) of most of the VexFlow objects, Measure still "directs" the creation of all the objects and what order they are supposed to be created in for both the VexFlowStaff and VexFlowNotes. I'm not looking for a specific answer as you'd need a much deeper understanding of my code. Just a general direction to go in. Here's a thought I had, create an MeasureView/NoteView/PartView classes that contains the basic VexFlow objects for each class in addition to any extraneous logic for it's creation? but where would these views be contained? Do I create a ScoreView that is a parallel graphical representation of everything? So that ScoreView.render() would cascade down PartView and call render for each PartView and casade down into each MeasureView, etc. Again, I just have no idea what direction to go in. The more I think about it, the more ways to go seem to pop into my head. I tried to be as concise and simplistic as possible while still getting my problem across. Please feel free to ask me any questions if anything is unclear. It's quite a struggle trying to dumb down a complicated problem to its core parts.

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• MD RAID 1 with external bitmap doesn't fully resync

  - by user64744

  I have an interesting configuration: dual boot system with a RAID 1 that needs to be visible in both Windows and Linux. The Windows install is Win 7 Enterprise, and the Linux install is Kubuntu 10.04. To get the RAID to work, I set it up using Windows's "Dynamic Disks" RAID 1, and brought it up in Linux using MD with no persistent superblock, and a write-intent bitmap on another partition. (Without this bitmap, MD had no way of knowing that the array was in sync, and would do a complete resync every time the array started.) The array is assembled like so: mdadm --build /dev/md1 -l 1 -n 2 -b /var/local/md1.bitmap /dev/sdb2 /dev/sdc2 I expected that the first time I ran this command, it would resync the array, write out a bitmap with no dirty chunks, and all would be good. This wasn't the case: after completing the resync, the bitmap was mostly clean, but about 5% dirty blocks remained, as revealed by mdadm -X /var/local/md1.bitmap I didn't mount the filesystem on /dev/md1 or touch it in any other way. I then found that stopping and restarting the array: mdadm --stop /dev/md1 mdadm --build /dev/md1 -l 1 -n 2 -b /var/local/md1.bitmap /dev/sdb2 /dev/sdc2 did indeed read in the bitmap, with an ensuing resync that went quickly because most of the blocks were marked clean. The confusing part is that this resync further reduced the number of dirty blocks, but still did not remove all of them. By repeatedly stopping and restarting I could slowly bring the dirty block count down to around 0.6%, where it seemed to level out. Any ideas what could be causing this? It smells to me of a race condition somewhere that leads to blocks either being skipped over during synchronization or not properly cleared from the bitmap, but I really have no evidence to prove this. It doesn't look like hardware issues since both drives are new and have zero read errors and reallocated sectors reported by smartctl -a.

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• Dealing with state problems in functional programming

  - by Andrew Martin

  I've learned how to program primarily from an OOP standpoint (like most of us, I'm sure), but I've spent a lot of time trying to learn how to solve problems the functional way. I have a good grasp on how to solve calculational problems with FP, but when it comes to more complicated problems I always find myself reverting to needing mutable objects. For example, if I'm writing a particle simulator, I will want particle "objects" with a mutable position to update. How are inherently "stateful" problems typically solved using functional programming techniques?

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• library for octree or kdtree

  - by Will

  Are there any robust performant libraries for indexing objects? It would need frustum culling and visiting objects hit by a ray as well as neighbourhood searches. I can find lots of articles showing the math for the component parts, often as algebra rather than simple C, but nothing that puts it all together (apart from perhaps Ogre, which has rather more involved and isn't so stand-alone). Surely hobby game makers don't all have to make their own octrees? (Python or C/C++ w/bindings preferred)

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• Linux - real-world hardware RAID controller tuning (scsi and cciss)

  - by ewwhite

  Most of the Linux systems I manage feature hardware RAID controllers (mostly HP Smart Array). They're all running RHEL or CentOS. I'm looking for real-world tunables to help optimize performance for setups that incorporate hardware RAID controllers with SAS disks (Smart Array, Perc, LSI, etc.) and battery-backed or flash-backed cache. Assume RAID 1+0 and multiple spindles (4+ disks). I spend a considerable amount of time tuning Linux network settings for low-latency and financial trading applications. But many of those options are well-documented (changing send/receive buffers, modifying TCP window settings, etc.). What are engineers doing on the storage side? Historically, I've made changes to the I/O scheduling elevator, recently opting for the deadline and noop schedulers to improve performance within my applications. As RHEL versions have progressed, I've also noticed that the compiled-in defaults for SCSI and CCISS block devices have changed as well. This has had an impact on the recommended storage subsystem settings over time. However, it's been awhile since I've seen any clear recommendations. And I know that the OS defaults aren't optimal. For example, it seems that the default read-ahead buffer of 128kb is extremely small for a deployment on server-class hardware. The following articles explore the performance impact of changing read-ahead cache and nr_requests values on the block queues. http://zackreed.me/articles/54-hp-smart-array-p410-controller-tuning http://www.overclock.net/t/515068/tuning-a-hp-smart-array-p400-with-linux-why-tuning-really-matters http://yoshinorimatsunobu.blogspot.com/2009/04/linux-io-scheduler-queue-size-and.html For example, these are suggested changes for an HP Smart Array RAID controller: echo "noop" > /sys/block/cciss\!c0d0/queue/scheduler blockdev --setra 65536 /dev/cciss/c0d0 echo 512 > /sys/block/cciss\!c0d0/queue/nr_requests echo 2048 > /sys/block/cciss\!c0d0/queue/read_ahead_kb What else can be reliably tuned to improve storage performance? I'm specifically looking for sysctl and sysfs options in production scenarios.

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• Data Auditor by Example

  - by Jinjin.Wang

  OWB has a node Data Auditors under Oracle Module in Projects Navigator. What is data auditor and how to use it? I will give an introduction to data auditor and show its usage by examples. Data auditor is an important tool in ensuring that data quality levels meet business requirements. Data auditor validates data against a set of data rules to determine which records comply and which do not. It gathers statistical metrics on how well the data in a system complies with a rule by auditing and marking how many errors are occurring against the audited table. Data auditors are typically scheduled for regular execution as part of a process flow, to monitor the quality of the data in an operational environment such as a data warehouse or ERP system, either immediately after updates like data loads, or at regular intervals. How to use data auditor to monitor data quality? Only objects with data rules can be monitored, so the first step is to define data rules according to business requirements and apply them to the objects you want to monitor. The objects can be tables, views, materialized views, and external tables. Secondly create a data auditor containing the objects. You can configure the data auditor and set physical deployment parameters for it as optional, which will be used while running the data auditor. Then deploy and run the data auditor either manually or as part of the process flow. After execution, the data auditor sets several output values, and records that are identified as not complying with the defined data rules contained in the data auditor are written to error tables. Here is an example. We have two tables DEPARTMENTS and EMPLOYEES (see pic-1 and pic-2. Click here for DDL and data) imported into OWB. We want to gather statistical metrics on how well data in these two tables satisfies the following requirements: a. Values of the EMPLOYEES.EMPLOYEE_ID attribute are three-digit numbers. b. Valid values for EMPLOYEES.JOB_ID are IT_PROG, SA_REP, SH_CLERK, PU_CLERK, and ST_CLERK. c. EMPLOYEES.EMPLOYEE_ID is related to DEPARTMENTS.MANAGER_ID. Pic-1 EMPLOYEES Pic-2 DEPARTMENTS 1. To determine legal data within EMPLOYEES or legal relationships between data in different columns of the two tables, firstly we define data rules based on the three requirements and apply them to tables. a. The first requirement is about patterns that an attribute is allowed to conform to. We create a Domain Pattern List data rule EMPLOYEE_PATTERN_RULE here. The pattern is defined in the Oracle Database regular expression syntax as ^([0-9]{3})$ Apply data rule EMPLOYEE_PATTERN_RULE to table EMPLOYEES.

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• Exchange 2010 Deployment Notes - ISA 2004 Server Issue

  - by BWCA

  An interesting ISA 2004 tidbit … While we were setting up our Exchange 2010 ActiveSync environment, we encountered a problem where we could not successfully telnet over port 443 from one of our ISA 2004 Servers to our Exchange 2010 Client Access Server Array. When we tried to telnet over port 443 from the ISA Server to the Client Access Server Array name, we would get a “Could not open connection to the host on port 443: Connect failed” error message. Also, when we used portqry over port 443 from the ISA Server to the Client Access Server Array name, we would get a “Error opening socket: 10065” and “No route to host” error messages. It was odd because we did not have any problems with using ping or tracert from the ISA Server to the Client Access Server Array and our firewall firewall policy was allowing 443 traffic to pass through. After some troubleshooting, we were able to telnet and use portqry over port 443 successfully if we stopped the Microsoft Firewall service on the ISA 2004 Server.  So, it was strictly a problem with ISA.  Eventually, we were able to isolate the problem to a ISA 2004 Server System Policy setting as shown below (to modify the System Policy, right-click Firewall Policy and click Edit System Policy). Under the Diagnostics Services – HTTP Connectivity verifiers Configuration Group, you need to enable the configuration group under the General tab to resolve the problem.  After we enabled the setting, we no longer had a problem.

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• RPi and Java Embedded GPIO: Java code to blink more LEDs

  - by hinkmond

  Now, it's time to blink the other GPIO ports with the other LEDs connected to them. This is easy using Java Embedded, since the Java programming language is powerful and flexible. Embedded developers are not used to this, since the C programming language is more popular but less easy to develop in. We just need to use a dynamic Java String array to map to the pinouts of the GPIO port names from the previous diagram posted. This way we can address each "channel" with an index into that String array. static String[] GpioChannels = { "0", "1", "4", "17", "21", "22", "10", "9" }; With this new dynamic array, we can streamline the main() of this Java program to activate all the ports. /** * @param args the command line arguments */ public static void main(String[] args) { FileWriter[] commandChannels; try { /*** Init GPIO port for output ***/ // Open file handles to GPIO port unexport and export controls FileWriter unexportFile = new FileWriter("/sys/class/gpio/unexport"); FileWriter exportFile = new FileWriter("/sys/class/gpio/export"); for (String gpioChannel : GpioChannels) { System.out.println(gpioChannel); // Reset the port unexportFile.write(gpioChannel); unexportFile.flush(); // Set the port for use exportFile.write(gpioChannel); exportFile.flush(); // Open file handle to port input/output control FileWriter directionFile = new FileWriter("/sys/class/gpio/gpio" + gpioChannel + "/direction"); // Set port for output directionFile.write(GPIO_OUT); directionFile.flush(); } And, then simply add array code to where we blink the LED to make it blink all the LEDS on and off at once. /*** Send commands to GPIO port ***/ commandChannels = new FileWriter[GpioChannels.length]; for (int channum=0; channum It's easier than falling off a log... or at least easier than C programming. Hinkmond

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• A strong component keeps everything together

  - by Justin Paul-Oracle

  Most of the times you implement a WebCenter Content based system, you require some sort of customization. Sometimes these customizations need a Java class or two, or libraries (for example, the JavaMail API), or Database Objects (like new tables, views, indexes, etc). I have seen that libraries and Database Objects are usually put in place using manual steps. This means that the library jar files are copied to one of the common classes directory (set in the Content CLASSPATH variable) and/or the database scripts are executed manually. I have also seen people place the custom Java classes in the common classes directory. While this may seem like an easy solution, think about a scenario where you need to disable or uninstall the component or if you have to upgrade or migrate the system. You have to keep these manual steps documented and execute them every time you encounter the above scenarios. It is very common that some of these manual steps are missed when you have multiple teams and people working on the system. Here are a few points to ponder upon: Place all your custom Java classes within your component. Create a new directory, say ${COMPONENT_DIR}/classes, and place your code there. You can choose to bundle all your classes into a jar or you can place the entire class directory structure. Add a path entry to the Build Settings so that it is bundled with the component when you build it. You also need to update the Custom Class Path and the Custom Class Path Load Order under the Advanced Build Settings. This will ensure that the system CLASSPATH is updated to add this new directory. Create a new component for any new library that you want to add. Add the appropriate path entries to the Build Settings so that it is bundled with the component when you build it. You also need to update the Custom Class Path, Custom Class Path Load Order and/or the Custom Library Path under the Advanced Build Settings. Enter a comma separated list of features that this component will provide. When you create other components that will use the features exposed by this component, make sure that you specify a dependency to this library component by specifying the comma separated list of features in the Advanced Build Settings. The component wizard allows you to create custom install/uninstall Java code. The wizard will create a install filter class when you check the “Has Install” checkbox on the “Install/Uninstall Settings” tab. Consider using this filter class to create database objects when you install the component and drop the objects when you uninstall the component. If you do a lot of custom component development, consider creating a install/uninstall Java class, which can execute queries defined within the component. To sum up, whenever you write a new custom component, make sure that you bundle everything within the component.

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• Designing a flexible tile-based engine

  - by Vee

  I'm trying to create a flexible tile-based game engine to make all sorts of non-realtime puzzle games, just as Bejeweled, Civilization, Sokoban, and so on. The first approach I had was to have a 2D array of Tile objects, and then have classes inheriting from Tile that represented the game objects. Unfortunately that way I couldn't stack more game elements on the same Tile without having a 3D array. Then I did something different: I still had the 2D array of Tile objects, but every Tile object contained a List where I put and different entities. This worked fine until 20 minutes ago, when I realized that it's too expensive to do many things, look at this example: I have a Wall entity. Every update I have to check the 8 adjacent Tiles, then check all of the entities in the Tile's List, check if any of those entities is a Wall, then finally draw the correct sprite. (This is done to draw walls that are next to each other seamlessly) The only solution I see now is having a 3D array, with many layers, that could suit every situation. But that way I can't stack two entities that share the same layer on the same tile. Whenever I want to do that I have to create a new layer. Is there a better solution? What would you do?

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