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  • Sniffing out SQL Code Smells: Inconsistent use of Symbolic names and Datatypes

    - by Phil Factor
    It is an awkward feeling. You’ve just delivered a database application that seems to be working fine in production, and you just run a few checks on it. You discover that there is a potential bug that, out of sheer good chance, hasn’t kicked in to produce an error; but it lurks, like a smoking bomb. Worse, maybe you find that the bug has started its evil work of corrupting the data, but in ways that nobody has, so far detected. You investigate, and find the damage. You are somehow going to have to repair it. Yes, it still very occasionally happens to me. It is not a nice feeling, and I do anything I can to prevent it happening. That’s why I’m interested in SQL code smells. SQL Code Smells aren’t necessarily bad practices, but just show you where to focus your attention when checking an application. Sometimes with databases the bugs can be subtle. SQL is rather like HTML: the language does its best to try to carry out your wishes, rather than to be picky about your bugs. Most of the time, this is a great benefit, but not always. One particular place where this can be detrimental is where you have implicit conversion between different data types. Most of the time it is completely harmless but we’re  concerned about the occasional time it isn’t. Let’s give an example: String truncation. Let’s give another even more frightening one, rounding errors on assignment to a number of different precision. Each requires a blog-post to explain in detail and I’m not now going to try. Just remember that it is not always a good idea to assign data to variables, parameters or even columns when they aren’t the same datatype, especially if you are relying on implicit conversion to work its magic.For details of the problem and the consequences, see here:  SR0014: Data loss might occur when casting from {Type1} to {Type2} . For any experienced Database Developer, this is a more frightening read than a Vampire Story. This is why one of the SQL Code Smells that makes me edgy, in my own or other peoples’ code, is to see parameters, variables and columns that have the same names and different datatypes. Whereas quite a lot of this is perfectly normal and natural, you need to check in case one of two things have gone wrong. Either sloppy naming, or mixed datatypes. Sure it is hard to remember whether you decided that the length of a log entry was 80 or 100 characters long, or the precision of a number. That is why a little check like this I’m going to show you is excellent for tidying up your code before you check it back into source Control! 1/ Checking Parameters only If you were just going to check parameters, you might just do this. It simply groups all the parameters, either input or output, of all the routines (e.g. stored procedures or functions) by their name and checks to see, in the HAVING clause, whether their data types are all the same. If not, it lists all the examples and their origin (the routine) Even this little check can occasionally be scarily revealing. ;WITH userParameter AS  ( SELECT   c.NAME AS ParameterName,  OBJECT_SCHEMA_NAME(c.object_ID) + '.' + OBJECT_NAME(c.object_ID) AS ObjectName,  t.name + ' '     + CASE     --we may have to put in the length            WHEN t.name IN ('char', 'varchar', 'nchar', 'nvarchar')             THEN '('               + CASE WHEN c.max_length = -1 THEN 'MAX'                ELSE CONVERT(VARCHAR(4),                    CASE WHEN t.name IN ('nchar', 'nvarchar')                      THEN c.max_length / 2 ELSE c.max_length                    END)                END + ')'         WHEN t.name IN ('decimal', 'numeric')             THEN '(' + CONVERT(VARCHAR(4), c.precision)                   + ',' + CONVERT(VARCHAR(4), c.Scale) + ')'         ELSE ''      END  --we've done with putting in the length      + CASE WHEN XML_collection_ID <> 0         THEN --deal with object schema names             '(' + CASE WHEN is_XML_Document = 1                    THEN 'DOCUMENT '                    ELSE 'CONTENT '                   END              + COALESCE(               (SELECT QUOTENAME(ss.name) + '.' + QUOTENAME(sc.name)                FROM sys.xml_schema_collections sc                INNER JOIN Sys.Schemas ss ON sc.schema_ID = ss.schema_ID                WHERE sc.xml_collection_ID = c.XML_collection_ID),'NULL') + ')'          ELSE ''         END        AS [DataType]  FROM sys.parameters c  INNER JOIN sys.types t ON c.user_Type_ID = t.user_Type_ID  WHERE OBJECT_SCHEMA_NAME(c.object_ID) <> 'sys'   AND parameter_id>0)SELECT CONVERT(CHAR(80),objectName+'.'+ParameterName),DataType FROM UserParameterWHERE ParameterName IN   (SELECT ParameterName FROM UserParameter    GROUP BY ParameterName    HAVING MIN(Datatype)<>MAX(DataType))ORDER BY ParameterName   so, in a very small example here, we have a @ClosingDelimiter variable that is only CHAR(1) when, by the looks of it, it should be up to ten characters long, or even worse, a function that should be a char(1) and seems to let in a string of ten characters. Worth investigating. Then we have a @Comment variable that can't decide whether it is a VARCHAR(2000) or a VARCHAR(MAX) 2/ Columns and Parameters Actually, once we’ve cleared up the mess we’ve made of our parameter-naming in the database we’re inspecting, we’re going to be more interested in listing both columns and parameters. We can do this by modifying the routine to list columns as well as parameters. Because of the slight complexity of creating the string version of the datatypes, we will create a fake table of both columns and parameters so that they can both be processed the same way. After all, we want the datatypes to match Unfortunately, parameters do not expose all the attributes we are interested in, such as whether they are nullable (oh yes, subtle bugs happen if this isn’t consistent for a datatype). We’ll have to leave them out for this check. Voila! A slight modification of the first routine ;WITH userObject AS  ( SELECT   Name AS DataName,--the actual name of the parameter or column ('@' removed)  --and the qualified object name of the routine  OBJECT_SCHEMA_NAME(ObjectID) + '.' + OBJECT_NAME(ObjectID) AS ObjectName,  --now the harder bit: the definition of the datatype.  TypeName + ' '     + CASE     --we may have to put in the length. e.g. CHAR (10)           WHEN TypeName IN ('char', 'varchar', 'nchar', 'nvarchar')             THEN '('               + CASE WHEN MaxLength = -1 THEN 'MAX'                ELSE CONVERT(VARCHAR(4),                    CASE WHEN TypeName IN ('nchar', 'nvarchar')                      THEN MaxLength / 2 ELSE MaxLength                    END)                END + ')'         WHEN TypeName IN ('decimal', 'numeric')--a BCD number!             THEN '(' + CONVERT(VARCHAR(4), Precision)                   + ',' + CONVERT(VARCHAR(4), Scale) + ')'         ELSE ''      END  --we've done with putting in the length      + CASE WHEN XML_collection_ID <> 0 --tush tush. XML         THEN --deal with object schema names             '(' + CASE WHEN is_XML_Document = 1                    THEN 'DOCUMENT '                    ELSE 'CONTENT '                   END              + COALESCE(               (SELECT TOP 1 QUOTENAME(ss.name) + '.' + QUOTENAME(sc.Name)                FROM sys.xml_schema_collections sc                INNER JOIN Sys.Schemas ss ON sc.schema_ID = ss.schema_ID                WHERE sc.xml_collection_ID = XML_collection_ID),'NULL') + ')'          ELSE ''         END        AS [DataType],       DataObjectType  FROM   (Select t.name AS TypeName, REPLACE(c.name,'@','') AS Name,          c.max_length AS MaxLength, c.precision AS [Precision],           c.scale AS [Scale], c.[Object_id] AS ObjectID, XML_collection_ID,          is_XML_Document,'P' AS DataobjectType  FROM sys.parameters c  INNER JOIN sys.types t ON c.user_Type_ID = t.user_Type_ID  AND parameter_id>0  UNION all  Select t.name AS TypeName, c.name AS Name, c.max_length AS MaxLength,          c.precision AS [Precision], c.scale AS [Scale],          c.[Object_id] AS ObjectID, XML_collection_ID,is_XML_Document,          'C' AS DataobjectType            FROM sys.columns c  INNER JOIN sys.types t ON c.user_Type_ID = t.user_Type_ID   WHERE OBJECT_SCHEMA_NAME(c.object_ID) <> 'sys'  )f)SELECT CONVERT(CHAR(80),objectName+'.'   + CASE WHEN DataobjectType ='P' THEN '@' ELSE '' END + DataName),DataType FROM UserObjectWHERE DataName IN   (SELECT DataName FROM UserObject   GROUP BY DataName    HAVING MIN(Datatype)<>MAX(DataType))ORDER BY DataName     Hmm. I can tell you I found quite a few minor issues with the various tabases I tested this on, and found some potential bugs that really leap out at you from the results. Here is the start of the result for AdventureWorks. Yes, AccountNumber is, for some reason, a Varchar(10) in the Customer table. Hmm. odd. Why is a city fifty characters long in that view?  The idea of the description of a colour being 256 characters long seems over-ambitious. Go down the list and you'll spot other mistakes. There are no bugs, but just mess. We started out with a listing to examine parameters, then we mixed parameters and columns. Our last listing is for a slightly more in-depth look at table columns. You’ll notice that we’ve delibarately removed the indication of whether a column is persisted, or is an identity column because that gives us false positives for our code smells. If you just want to browse your metadata for other reasons (and it can quite help in some circumstances) then uncomment them! ;WITH userColumns AS  ( SELECT   c.NAME AS columnName,  OBJECT_SCHEMA_NAME(c.object_ID) + '.' + OBJECT_NAME(c.object_ID) AS ObjectName,  REPLACE(t.name + ' '   + CASE WHEN is_computed = 1 THEN ' AS ' + --do DDL for a computed column          (SELECT definition FROM sys.computed_columns cc           WHERE cc.object_id = c.object_id AND cc.column_ID = c.column_ID)     --we may have to put in the length            WHEN t.Name IN ('char', 'varchar', 'nchar', 'nvarchar')             THEN '('               + CASE WHEN c.Max_Length = -1 THEN 'MAX'                ELSE CONVERT(VARCHAR(4),                    CASE WHEN t.Name IN ('nchar', 'nvarchar')                      THEN c.Max_Length / 2 ELSE c.Max_Length                    END)                END + ')'       WHEN t.name IN ('decimal', 'numeric')       THEN '(' + CONVERT(VARCHAR(4), c.precision) + ',' + CONVERT(VARCHAR(4), c.Scale) + ')'       ELSE ''      END + CASE WHEN c.is_rowguidcol = 1          THEN ' ROWGUIDCOL'          ELSE ''         END + CASE WHEN XML_collection_ID <> 0            THEN --deal with object schema names             '(' + CASE WHEN is_XML_Document = 1                THEN 'DOCUMENT '                ELSE 'CONTENT '               END + COALESCE((SELECT                QUOTENAME(ss.name) + '.' + QUOTENAME(sc.name)                FROM                sys.xml_schema_collections sc                INNER JOIN Sys.Schemas ss ON sc.schema_ID = ss.schema_ID                WHERE                sc.xml_collection_ID = c.XML_collection_ID),                'NULL') + ')'            ELSE ''           END + CASE WHEN is_identity = 1             THEN CASE WHEN OBJECTPROPERTY(object_id,                'IsUserTable') = 1 AND COLUMNPROPERTY(object_id,                c.name,                'IsIDNotForRepl') = 0 AND OBJECTPROPERTY(object_id,                'IsMSShipped') = 0                THEN ''                ELSE ' NOT FOR REPLICATION '               END             ELSE ''            END + CASE WHEN c.is_nullable = 0               THEN ' NOT NULL'               ELSE ' NULL'              END + CASE                WHEN c.default_object_id <> 0                THEN ' DEFAULT ' + object_Definition(c.default_object_id)                ELSE ''               END + CASE                WHEN c.collation_name IS NULL                THEN ''                WHEN c.collation_name <> (SELECT                collation_name                FROM                sys.databases                WHERE                name = DB_NAME()) COLLATE Latin1_General_CI_AS                THEN COALESCE(' COLLATE ' + c.collation_name,                '')                ELSE ''                END,'  ',' ') AS [DataType]FROM sys.columns c  INNER JOIN sys.types t ON c.user_Type_ID = t.user_Type_ID  WHERE OBJECT_SCHEMA_NAME(c.object_ID) <> 'sys')SELECT CONVERT(CHAR(80),objectName+'.'+columnName),DataType FROM UserColumnsWHERE columnName IN (SELECT columnName FROM UserColumns  GROUP BY columnName  HAVING MIN(Datatype)<>MAX(DataType))ORDER BY columnName If you take a look down the results against Adventureworks, you'll see once again that there are things to investigate, mostly, in the illustration, discrepancies between null and non-null datatypes So I here you ask, what about temporary variables within routines? If ever there was a source of elusive bugs, you'll find it there. Sadly, these temporary variables are not stored in the metadata so we'll have to find a more subtle way of flushing these out, and that will, I'm afraid, have to wait!

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  • Evolution of an Application: how to manage and improve core engine?

    - by Phil Carter
    The web application I work on has been live for a year now, but it's time for it to evolve and one of the ways in which it is evolving is into a multi-brand application - in this case several different companies using the application, different templates/content and some slight business logic changes between them. The problem I'm facing is implementing a best practice across the site where there are differences in business logic for each brand. These will mostly be very superficial, using a an alternative mailing list provider or capturing some extra data in a form. I don't want to have if(brand === x) { ... } else { ... } all over the site especially as most of what needs to be changed can be handled with extending the existing class. I've thought of several methods that could be used to instantiate the correct class, but I'm just not sure which is going to be best especially as some seem to lead to duplication of more code than should be necessary. Here's what I've considered: 1) Use a Static Loader similar to Zend_Loader which can take the class being requested, and has knowledge of the Brand and can then return the correct object. $class = App_Loader::getObject('User', $brand); 2) Factory classes. We use these in the application already for Products but we could utilise them here also to provide a transparent interface to the class. 3) Routing the page request to a specific brand controller. This however seems like it would duplicate a lot of code/logic. Is there a pattern or something else I should be considering to solve this problem? 4) How to manage a growing project that has multiple custom instances in production? Update This is a PHP application so the decisions on which class to load are made per request. There could be upwards of 100+ different 'brands' running.

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  • Restricting joystick within a radius of center

    - by Phil
    I'm using Unity3d iOs and am using the example joysticks that came with one of the packages. It works fine but the area the joystick moves in is a rectangle which is unintuitive for my type of game. I can figure out how to see if the distance between the center and the current point is too far but I can't figure out how to constrain it to a certain distance without interrupting the finger tracking. Here's the relevant code: using UnityEngine; using System.Collections; public class Boundary { public Vector2 min = Vector2.zero; public Vector2 max = Vector2.zero; } public class Joystick : MonoBehaviour{ static private Joystick[] joysticks; // A static collection of all joysticks static private bool enumeratedJoysticks=false; static private float tapTimeDelta = 0.3f; // Time allowed between taps public bool touchPad; // Is this a TouchPad? public Rect touchZone; public Vector2 deadZone = Vector2.zero; // Control when position is output public bool normalize = false; // Normalize output after the dead-zone? public Vector2 position; // [-1, 1] in x,y public int tapCount; // Current tap count private int lastFingerId = -1; // Finger last used for this joystick private float tapTimeWindow; // How much time there is left for a tap to occur private Vector2 fingerDownPos; private float fingerDownTime; private float firstDeltaTime = 0.5f; private GUITexture gui; // Joystick graphic private Rect defaultRect; // Default position / extents of the joystick graphic private Boundary guiBoundary = new Boundary(); // Boundary for joystick graphic public Vector2 guiTouchOffset; // Offset to apply to touch input private Vector2 guiCenter; // Center of joystick private Vector3 tmpv3; private Rect tmprect; private Color tmpclr; public float allowedDistance; public enum JoystickType { movement, rotation } public JoystickType joystickType; public void Start() { // Cache this component at startup instead of looking up every frame gui = (GUITexture) GetComponent( typeof(GUITexture) ); // Store the default rect for the gui, so we can snap back to it defaultRect = gui.pixelInset; if ( touchPad ) { // If a texture has been assigned, then use the rect ferom the gui as our touchZone if ( gui.texture ) touchZone = gui.pixelInset; } else { // This is an offset for touch input to match with the top left // corner of the GUI guiTouchOffset.x = defaultRect.width * 0.5f; guiTouchOffset.y = defaultRect.height * 0.5f; // Cache the center of the GUI, since it doesn't change guiCenter.x = defaultRect.x + guiTouchOffset.x; guiCenter.y = defaultRect.y + guiTouchOffset.y; // Let's build the GUI boundary, so we can clamp joystick movement guiBoundary.min.x = defaultRect.x - guiTouchOffset.x; guiBoundary.max.x = defaultRect.x + guiTouchOffset.x; guiBoundary.min.y = defaultRect.y - guiTouchOffset.y; guiBoundary.max.y = defaultRect.y + guiTouchOffset.y; } } public void Disable() { gameObject.active = false; enumeratedJoysticks = false; } public void ResetJoystick() { if (joystickType != JoystickType.rotation) { //Don't do anything if turret mode // Release the finger control and set the joystick back to the default position gui.pixelInset = defaultRect; lastFingerId = -1; position = Vector2.zero; fingerDownPos = Vector2.zero; if ( touchPad ){ tmpclr = gui.color; tmpclr.a = 0.025f; gui.color = tmpclr; } } else { //gui.pixelInset = defaultRect; lastFingerId = -1; position = position; fingerDownPos = fingerDownPos; if ( touchPad ){ tmpclr = gui.color; tmpclr.a = 0.025f; gui.color = tmpclr; } } } public bool IsFingerDown() { return (lastFingerId != -1); } public void LatchedFinger( int fingerId ) { // If another joystick has latched this finger, then we must release it if ( lastFingerId == fingerId ) ResetJoystick(); } public void Update() { if ( !enumeratedJoysticks ) { // Collect all joysticks in the game, so we can relay finger latching messages joysticks = (Joystick[]) FindObjectsOfType( typeof(Joystick) ); enumeratedJoysticks = true; } //CHeck if distance is over the allowed amount //Get centerPosition //Get current position //Get distance //If over, don't allow int count = iPhoneInput.touchCount; // Adjust the tap time window while it still available if ( tapTimeWindow > 0 ) tapTimeWindow -= Time.deltaTime; else tapCount = 0; if ( count == 0 ) ResetJoystick(); else { for(int i = 0;i < count; i++) { iPhoneTouch touch = iPhoneInput.GetTouch(i); Vector2 guiTouchPos = touch.position - guiTouchOffset; bool shouldLatchFinger = false; if ( touchPad ) { if ( touchZone.Contains( touch.position ) ) shouldLatchFinger = true; } else if ( gui.HitTest( touch.position ) ) { shouldLatchFinger = true; } // Latch the finger if this is a new touch if ( shouldLatchFinger && ( lastFingerId == -1 || lastFingerId != touch.fingerId ) ) { if ( touchPad ) { tmpclr = gui.color; tmpclr.a = 0.15f; gui.color = tmpclr; lastFingerId = touch.fingerId; fingerDownPos = touch.position; fingerDownTime = Time.time; } lastFingerId = touch.fingerId; // Accumulate taps if it is within the time window if ( tapTimeWindow > 0 ) { tapCount++; print("tap" + tapCount.ToString()); } else { tapCount = 1; print("tap" + tapCount.ToString()); //Tell gameobject that player has tapped turret joystick if (joystickType == JoystickType.rotation) { //TODO: Call! } tapTimeWindow = tapTimeDelta; } // Tell other joysticks we've latched this finger foreach ( Joystick j in joysticks ) { if ( j != this ) j.LatchedFinger( touch.fingerId ); } } if ( lastFingerId == touch.fingerId ) { // Override the tap count with what the iPhone SDK reports if it is greater // This is a workaround, since the iPhone SDK does not currently track taps // for multiple touches if ( touch.tapCount > tapCount ) tapCount = touch.tapCount; if ( touchPad ) { // For a touchpad, let's just set the position directly based on distance from initial touchdown position.x = Mathf.Clamp( ( touch.position.x - fingerDownPos.x ) / ( touchZone.width / 2 ), -1, 1 ); position.y = Mathf.Clamp( ( touch.position.y - fingerDownPos.y ) / ( touchZone.height / 2 ), -1, 1 ); } else { // Change the location of the joystick graphic to match where the touch is tmprect = gui.pixelInset; tmprect.x = Mathf.Clamp( guiTouchPos.x, guiBoundary.min.x, guiBoundary.max.x ); tmprect.y = Mathf.Clamp( guiTouchPos.y, guiBoundary.min.y, guiBoundary.max.y ); //Check distance float distance = Vector2.Distance(new Vector2(defaultRect.x, defaultRect.y), new Vector2(tmprect.x, tmprect.y)); float angle = Vector2.Angle(new Vector2(defaultRect.x, defaultRect.y), new Vector2(tmprect.x, tmprect.y)); if (distance < allowedDistance) { //Ok gui.pixelInset = tmprect; } else { //This is where I don't know what to do... } } if ( touch.phase == iPhoneTouchPhase.Ended || touch.phase == iPhoneTouchPhase.Canceled ) ResetJoystick(); } } } if ( !touchPad ) { // Get a value between -1 and 1 based on the joystick graphic location position.x = ( gui.pixelInset.x + guiTouchOffset.x - guiCenter.x ) / guiTouchOffset.x; position.y = ( gui.pixelInset.y + guiTouchOffset.y - guiCenter.y ) / guiTouchOffset.y; } // Adjust for dead zone float absoluteX = Mathf.Abs( position.x ); float absoluteY = Mathf.Abs( position.y ); if ( absoluteX < deadZone.x ) { // Report the joystick as being at the center if it is within the dead zone position.x = 0; } else if ( normalize ) { // Rescale the output after taking the dead zone into account position.x = Mathf.Sign( position.x ) * ( absoluteX - deadZone.x ) / ( 1 - deadZone.x ); } if ( absoluteY < deadZone.y ) { // Report the joystick as being at the center if it is within the dead zone position.y = 0; } else if ( normalize ) { // Rescale the output after taking the dead zone into account position.y = Mathf.Sign( position.y ) * ( absoluteY - deadZone.y ) / ( 1 - deadZone.y ); } } } So the later portion of the code handles the updated position of the joystick thumb. This is where I'd like it to track the finger position in a direction it still is allowed to move (like if the finger is too far up and slightly to the +X I'd like to make sure the joystick is as close in X and Y as allowed within the radius) Thanks for reading!

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  • Normalisation and 'Anima notitia copia' (Soul of the Database)

    - by Phil Factor
    (A Guest Editorial for Simple-Talk) The other day, I was staring  at the sys.syslanguages  table in SQL Server with slightly-raised eyebrows . I’d just been reading Chris Date’s  interesting book ‘SQL and Relational Theory’. He’d made the point that you’re not necessarily doing relational database operations by using a SQL Database product.  The same general point was recently made by Dino Esposito about ASP.NET MVC.  The use of ASP.NET MVC doesn’t guarantee you a good application design: It merely makes it possible to test it. The way I’d describe the sentiment in both cases is ‘you can hit someone over the head with a frying-pan but you can’t call it cooking’. SQL enables you to create relational databases. However,  even if it smells bad, it is no crime to do hideously un-relational things with a SQL Database just so long as it’s necessary and you can tell the difference; not only that but also only if you’re aware of the risks and implications. Naturally, I’ve never knowingly created a database that Codd would have frowned at, but around the edges are interfaces and data feeds I’ve written  that have caused hissy fits amongst the Normalisation fundamentalists. Part of the problem for those who agonise about such things  is the misinterpretation of Atomicity.  An atomic value is one for which, in the strange virtual universe you are creating in your database, you don’t have any interest in any of its component parts.  If you aren’t interested in the electrons, neutrinos,  muons,  or  taus, then  an atom is ..er.. atomic. In the same way, if you are passed a JSON string or XML, and required to store it in a database, then all you need to do is to ask yourself, in your role as Anima notitia copia (Soul of the database) ‘have I any interest in the contents of this item of information?’.  If the answer is ‘No!’, or ‘nequequam! Then it is an atomic value, however complex it may be.  After all, you would never have the urge to store the pixels of images individually, under the misguided idea that these are the atomic values would you?  I would, of course,  ask the ‘Anima notitia copia’ rather than the application developers, since there may be more than one application, and the applications developers may be designing the application in the absence of full domain knowledge, (‘or by the seat of the pants’ as the technical term used to be). If, on the other hand, the answer is ‘sure, and we want to index the XML column’, then we may be in for some heavy XML-shredding sessions to get to store the ‘atomic’ values and ensure future harmony as the application develops. I went back to looking at the sys.syslanguages table. It has a months column with the months in a delimited list January,February,March,April,May,June,July,August,September,October,November,December This is an ordered list. Wicked? I seem to remember that this value, like shortmonths and days, is treated as a ‘thing’. It is merely passed off to an external  C++ routine in order to format a date in a particular language, and never accessed directly within the database. As far as the database is concerned, it is an atomic value.  There is more to normalisation than meets the eye.

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  • A Slice of Raspberry Pi

    - by Phil Factor
    Guest editorial for the ITPro/SysAdmin newsletter The Raspberry Pi Foundation has done a superb design job on their new $35 network-enabled Linux computer. This tiny machine, incorporating an ARM processor on a Broadcom BCM2835 multimedia chip, aims to put the fun back into learning computing. The public response has been overwhelmingly positive.Note that aim: "…to put the fun back". Education in Information Technology is in dire straits. It always has been, but seems to have deteriorated further still, even in the face of improved provision of equipment.In many countries, the government controls the curriculum. It predicted a shortage in office-based IT skills, and so geared the ICT curriculum toward mind-numbing training in word-processing and spreadsheet skills. Instead, the shortage has turned out to be in people with an engineering-mindset, who can solve problems with whatever technologies are available and learn new techniques quickly, in a rapidly-changing field.In retrospect, the assumption that specific training was required rather than an education was an idiotic response to the arrival of mainstream information technology. As a result, ICT became a disaster area, which discouraged a generation of youngsters from a career in IT, and thereby led directly to the shortage of people with the skills that are required to exploit the potential of Information Technology..Raspberry Pi aims to reverse the trend. This is a rig that is geared to fast graphics in high resolution. It is no toy. It should be a superb games machine. However, the use of Fedora, Debian, or Arch Linux ARM shows the more serious educational intent behind the Foundation's work. It looks like it will even do some office work too!So, get hold of any power supply that provides a 5VDC source at the required 700mA; an old Blackberry charger will do or, alternatively, it will run off four AA cells. You'll need a USB hub to support the mouse and keyboard, and maybe a hard drive. You'll want a DVI monitor (with audio out) or TV (sound and video). You'll also need to be able to cope with wired Ethernet 10/100, if you want networking.With this lot assembled, stick the paraphernalia on the back of the HDTV with Blu Tack, get a nice keyboard, and you have a classy Linux-based home computer. The major cost is in the T.V and the keyboard. If you're not already writing software for this platform, then maybe, at a time when some countries are talking of orders in the millions, you should consider it.

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  • Source-control 'wet-work'?

    - by Phil Factor
    When a design or creative work is flawed beyond remedy, it is often best to destroy it and start again. The other day, I lost the code to a long and intricate SQL batch I was working on. I’d thought it was impossible, but it happened. With all the technology around that is designed to prevent this occurring, this sort of accident has become a rare event.  If it weren’t for a deranged laptop, and my distraction, the code wouldn’t have been lost this time.  As always, I sighed, had a soothing cup of tea, and typed it all in again.  The new code I hastily tapped in  was much better: I’d held in my head the essence of how the code should work rather than the details: I now knew for certain  the start point, the end, and how it should be achieved. Instantly the detritus of half-baked thoughts fell away and I was able to write logical code that performed better.  Because I could work so quickly, I was able to hold the details of all the columns and variables in my head, and the dynamics of the flow of data. It was, in fact, easier and quicker to start from scratch rather than tidy up and refactor the existing code with its inevitable fumbling and half-baked ideas. What a shame that technology is now so good that developers rarely experience the cleansing shock of losing one’s code and having to rewrite it from scratch.  If you’ve never accidentally lost  your code, then it is worth doing it deliberately once for the experience. Creative people have, until Technology mistakenly prevented it, torn up their drafts or sketches, threw them in the bin, and started again from scratch.  Leonardo’s obsessive reworking of the Mona Lisa was renowned because it was so unusual:  Most artists have been utterly ruthless in destroying work that didn’t quite make it. Authors are particularly keen on writing afresh, and the results are generally positive. Lawrence of Arabia actually lost the entire 250,000 word manuscript of ‘The Seven Pillars of Wisdom’ by accidentally leaving it on a train at Reading station, before rewriting a much better version.  Now, any writer or artist is seduced by technology into altering or refining their work rather than casting it dramatically in the bin or setting a light to it on a bonfire, and rewriting it from the blank page.  It is easy to pick away at a flawed work, but the real creative process is far more brutal. Once, many years ago whilst running a software house that supplied commercial software to local businesses, I’d been supervising an accounting system for a farming cooperative. No packaged system met their needs, and it was all hand-cut code.  For us, it represented a breakthrough as it was for a government organisation, and success would guarantee more contracts. As you’ve probably guessed, the code got mangled in a disk crash just a week before the deadline for delivery, and the many backups all proved to be entirely corrupted by a faulty tape drive.  There were some fragments left on individual machines, but they were all of different versions.  The developers were in despair.  Strangely, I managed to re-write the bulk of a three-month project in a manic and caffeine-soaked weekend.  Sure, that elegant universally-applicable input-form routine was‘nt quite so elegant, but it didn’t really need to be as we knew what forms it needed to support.  Yes, the code lacked architectural elegance and reusability. By dawn on Monday, the application passed its integration tests. The developers rose to the occasion after I’d collapsed, and tidied up what I’d done, though they were reproachful that some of the style and elegance had gone out of the application. By the delivery date, we were able to install it. It was a smaller, faster application than the beta they’d seen and the user-interface had a new, rather Spartan, appearance that we swore was done to conform to the latest in user-interface guidelines. (we switched to Helvetica font to look more ‘Bauhaus’ ). The client was so delighted that he forgave the new bugs that had crept in. I still have the disk that crashed, up in the attic. In IT, we have had mixed experiences from complete re-writes. Lotus 123 never really recovered from a complete rewrite from assembler into C, Borland made the mistake with Arago and Quattro Pro  and Netscape’s complete rewrite of their Navigator 4 browser was a white-knuckle ride. In all cases, the decision to rewrite was a result of extreme circumstances where no other course of action seemed possible.   The rewrite didn’t come out of the blue. I prefer to remember the rewrite of Minix by young Linus Torvalds, or the rewrite of Bitkeeper by a slightly older Linus.  The rewrite of CP/M didn’t do too badly either, did it? Come to think of it, the guy who decided to rewrite the windowing system of the Xerox Star never regretted the decision. I’ll agree that one should often resist calls for a rewrite. One of the worst habits of the more inexperienced programmer is to denigrate whatever code he or she inherits, and then call loudly for a complete rewrite. They are buoyed up by the mistaken belief that they can do better. This, however, is a different psychological phenomenon, more related to the idea of some motorcyclists that they are operating on infinite lives, or the occasional squaddies that if they charge the machine-guns determinedly enough all will be well. Grim experience brings out the humility in any experienced programmer.  I’m referring to quite different circumstances here. Where a team knows the requirements perfectly, are of one mind on methodology and coding standards, and they already have a solution, then what is wrong with considering  a complete rewrite? Rewrites are so painful in the early stages, until that point where one realises the payoff, that even I quail at the thought. One needs a natural disaster to push one over the edge. The trouble is that source-control systems, and disaster recovery systems, are just too good nowadays.   If I were to lose this draft of this very blog post, I know I’d rewrite it much better. However, if you read this, you’ll know I didn’t have the nerve to delete it and start again.  There was a time that one prayed that unreliable hardware would deliver you from an unmaintainable mess of a codebase, but now technology has made us almost entirely immune to such a merciful act of God. An old friend of mine with long experience in the software industry has long had the idea of the ‘source-control wet-work’,  where one hires a malicious hacker in some wild eastern country to hack into one’s own  source control system to destroy all trace of the source to an application. Alas, backup systems are just too good to make this any more than a pipedream. Somehow, it would be difficult to promote the idea. As an alternative, could one construct a source control system that, on doing all the code-quality metrics, would systematically destroy all trace of source code that failed the quality test? Alas, I can’t see many managers buying into the idea. In reading the full story of the near-loss of Toy Story 2, it set me thinking. It turned out that the lucky restoration of the code wasn’t the happy ending one first imagined it to be, because they eventually came to the conclusion that the plot was fundamentally flawed and it all had to be rewritten anyway.  Was this an early  case of the ‘source-control wet-job’?’ It is very hard nowadays to do a rapid U-turn in a development project because we are far too prone to cling to our existing source-code.

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  • Getting away from a customized Magento 1.4 installation - Magento 1.6, OpenCart, or others?

    - by Phil
    I'm dealing with a Magento 1.4.0.0 Community Edition installation with various undocumented changes to the core (mostly integration with an ERP system), an outdated Sweet Tooth Points & Rewards module and some custom payment providers. It also doubles as a mediocre blogging/CMS system. It has one store each for 3 different languages, with about 40 product categories for a few hundred products. [rant] With no prior experience with any PHP e-commerce systems, I find it very difficult to work with. I attempted to install Magento 1.4.0.0 on my local WAMP dev machine, it installs fine, but the main page or search do not show any products no matter what I do in the backend admin panel. I don't know what's wrong with it, and whatever information I googled is either too old or too new from Magento 1.4. Later I'm given FTP access to the testing server, which neither my manager or I have permission to install XDebug on, as apparantly it runs on the same server as the production server (yikes). Trying to learn how Magento works is torture. I spent a week trying to add some fields into the Onepage Checkout before giving up and went to work on something else. The template system, just like the rest of Magento, is a bloated mishmash of overcomplicated directory structures, weird config xml files and EAV databases. I went into 6 different models and several content blocks in the backend just to change what the front page looks like. With little-to-none helpful and clear documentation (unlike CodeIgniter) and various breaking changes between minor point revisions which makes it hard to find useful information, Magento 1.4 is a developer killer. [/rant] The client is planning to redesign the site and has decided it might as well as move on from this unsustainable, hacky, upgrade-unfriendly, developer-unfriendly mess. Magento 1.4 is starting to show its age, with Magento 1.7 coming soon, the client is considering upgrading to Magento 1.6 or 1.7 if it has improved from 1.4. The customizations done to the current Magento 1.4 installation will have to be redone, and a new license for the Sweet Tooth Points & Rewards module will have to be bought. The client is also open to other e-commerce systems. I've looked at OpenCart and it seems to be quite developer friendly with a fairly simple structure. I found some complaints regarding its performance when the shop has thousands of categories or products, but this is not an issue with the current number of products my client has. It seems to be solid ground for easy customization to bring the rewards system and ERP integration over. What should the client upgrade to in this case?

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  • TypeScript or JavaScript for noob web developer [closed]

    - by Phil Murray
    Following the recent release by Microsoft of TypeScript I was wondering if this is something that should be considered for a experienced WinForm and XAML developer looking to get into more web development. From reviewing a number of sites and videos online it appears that the type system for TypeScript makes more sense to me as a thick client developer than the dynamic type system in Javascript. I understand that Typescript compiles down to JavaScript but it appears that the learning curve is shallower due to the current tooling provided by Microsoft. What are your thoughts?

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  • Navigating Libgdx Menu with arrow keys or controller

    - by Phil Royer
    I'm attempting to make my menu navigable with the arrow keys or via the d-pad on a controller. So Far I've had no luck. The question is: Can someone walk me through how to make my current menu or any libgdx menu keyboard accessible? I'm a bit noobish with some stuff and I come from a Javascript background. Here's an example of what I'm trying to do: http://dl.dropboxusercontent.com/u/39448/webgl/qb/qb.html For a simple menu that you can just add a few buttons to and it run out of the box use this: http://www.sadafnoor.com/blog/how-to-create-simple-menu-in-libgdx/ Or you can use my code but I use a lot of custom styles. And here's an example of my code: import aurelienribon.tweenengine.Timeline; import aurelienribon.tweenengine.Tween; import aurelienribon.tweenengine.TweenManager; import com.badlogic.gdx.Game; import com.badlogic.gdx.Gdx; import com.badlogic.gdx.Screen; import com.badlogic.gdx.graphics.GL20; import com.badlogic.gdx.graphics.Texture; import com.badlogic.gdx.graphics.g2d.Sprite; import com.badlogic.gdx.graphics.g2d.SpriteBatch; import com.badlogic.gdx.graphics.g2d.TextureAtlas; import com.badlogic.gdx.math.Vector2; import com.badlogic.gdx.scenes.scene2d.Actor; import com.badlogic.gdx.scenes.scene2d.InputEvent; import com.badlogic.gdx.scenes.scene2d.InputListener; import com.badlogic.gdx.scenes.scene2d.Stage; import com.badlogic.gdx.scenes.scene2d.ui.Skin; import com.badlogic.gdx.scenes.scene2d.ui.Table; import com.badlogic.gdx.scenes.scene2d.ui.TextButton; import com.badlogic.gdx.scenes.scene2d.utils.Align; import com.badlogic.gdx.scenes.scene2d.utils.ClickListener; import com.project.game.tween.ActorAccessor; public class MainMenu implements Screen { private SpriteBatch batch; private Sprite menuBG; private Stage stage; private TextureAtlas atlas; private Skin skin; private Table table; private TweenManager tweenManager; @Override public void render(float delta) { Gdx.gl.glClearColor(0, 0, 0, 1); Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT); batch.begin(); menuBG.draw(batch); batch.end(); //table.debug(); stage.act(delta); stage.draw(); //Table.drawDebug(stage); tweenManager.update(delta); } @Override public void resize(int width, int height) { menuBG.setSize(width, height); stage.setViewport(width, height, false); table.invalidateHierarchy(); } @Override public void resume() { } @Override public void show() { stage = new Stage(); Gdx.input.setInputProcessor(stage); batch = new SpriteBatch(); atlas = new TextureAtlas("ui/atlas.pack"); skin = new Skin(Gdx.files.internal("ui/menuSkin.json"), atlas); table = new Table(skin); table.setBounds(0, 0, Gdx.graphics.getWidth(), Gdx.graphics.getHeight()); // Set Background Texture menuBackgroundTexture = new Texture("images/mainMenuBackground.png"); menuBG = new Sprite(menuBackgroundTexture); menuBG.setSize(Gdx.graphics.getWidth(), Gdx.graphics.getHeight()); // Create Main Menu Buttons // Button Play TextButton buttonPlay = new TextButton("START", skin, "inactive"); buttonPlay.addListener(new ClickListener() { @Override public void clicked(InputEvent event, float x, float y) { ((Game) Gdx.app.getApplicationListener()).setScreen(new LevelMenu()); } }); buttonPlay.addListener(new InputListener() { public boolean keyDown (InputEvent event, int keycode) { System.out.println("down"); return true; } }); buttonPlay.padBottom(12); buttonPlay.padLeft(20); buttonPlay.getLabel().setAlignment(Align.left); // Button EXTRAS TextButton buttonExtras = new TextButton("EXTRAS", skin, "inactive"); buttonExtras.addListener(new ClickListener() { @Override public void clicked(InputEvent event, float x, float y) { ((Game) Gdx.app.getApplicationListener()).setScreen(new ExtrasMenu()); } }); buttonExtras.padBottom(12); buttonExtras.padLeft(20); buttonExtras.getLabel().setAlignment(Align.left); // Button Credits TextButton buttonCredits = new TextButton("CREDITS", skin, "inactive"); buttonCredits.addListener(new ClickListener() { @Override public void clicked(InputEvent event, float x, float y) { ((Game) Gdx.app.getApplicationListener()).setScreen(new Credits()); } }); buttonCredits.padBottom(12); buttonCredits.padLeft(20); buttonCredits.getLabel().setAlignment(Align.left); // Button Settings TextButton buttonSettings = new TextButton("SETTINGS", skin, "inactive"); buttonSettings.addListener(new ClickListener() { @Override public void clicked(InputEvent event, float x, float y) { ((Game) Gdx.app.getApplicationListener()).setScreen(new Settings()); } }); buttonSettings.padBottom(12); buttonSettings.padLeft(20); buttonSettings.getLabel().setAlignment(Align.left); // Button Exit TextButton buttonExit = new TextButton("EXIT", skin, "inactive"); buttonExit.addListener(new ClickListener() { @Override public void clicked(InputEvent event, float x, float y) { Gdx.app.exit(); } }); buttonExit.padBottom(12); buttonExit.padLeft(20); buttonExit.getLabel().setAlignment(Align.left); // Adding Heading-Buttons to the cue table.add().width(190); table.add().width((table.getWidth() / 10) * 3); table.add().width((table.getWidth() / 10) * 5).height(140).spaceBottom(50); table.add().width(190).row(); table.add().width(190); table.add(buttonPlay).spaceBottom(20).width(460).height(110); table.add().row(); table.add().width(190); table.add(buttonExtras).spaceBottom(20).width(460).height(110); table.add().row(); table.add().width(190); table.add(buttonCredits).spaceBottom(20).width(460).height(110); table.add().row(); table.add().width(190); table.add(buttonSettings).spaceBottom(20).width(460).height(110); table.add().row(); table.add().width(190); table.add(buttonExit).width(460).height(110); table.add().row(); stage.addActor(table); // Animation Settings tweenManager = new TweenManager(); Tween.registerAccessor(Actor.class, new ActorAccessor()); // Heading and Buttons Fade In Timeline.createSequence().beginSequence() .push(Tween.set(buttonPlay, ActorAccessor.ALPHA).target(0)) .push(Tween.set(buttonExtras, ActorAccessor.ALPHA).target(0)) .push(Tween.set(buttonCredits, ActorAccessor.ALPHA).target(0)) .push(Tween.set(buttonSettings, ActorAccessor.ALPHA).target(0)) .push(Tween.set(buttonExit, ActorAccessor.ALPHA).target(0)) .push(Tween.to(buttonPlay, ActorAccessor.ALPHA, .5f).target(1)) .push(Tween.to(buttonExtras, ActorAccessor.ALPHA, .5f).target(1)) .push(Tween.to(buttonCredits, ActorAccessor.ALPHA, .5f).target(1)) .push(Tween.to(buttonSettings, ActorAccessor.ALPHA, .5f).target(1)) .push(Tween.to(buttonExit, ActorAccessor.ALPHA, .5f).target(1)) .end().start(tweenManager); tweenManager.update(Gdx.graphics.getDeltaTime()); } public static Vector2 getStageLocation(Actor actor) { return actor.localToStageCoordinates(new Vector2(0, 0)); } @Override public void dispose() { stage.dispose(); atlas.dispose(); skin.dispose(); menuBG.getTexture().dispose(); } @Override public void hide() { dispose(); } @Override public void pause() { } }

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  • The Presentation Isn't Over Until It's Over

    - by Phil Factor
    The senior corporate dignitaries settled into their seats looking important in a blue-suited sort of way. The lights dimmed as I strode out in front to give my presentation.  I had ten vital minutes to make my pitch.  I was about to dazzle the top management of a large software company who were considering the purchase of my software product. I would present them with a dazzling synthesis of diagrams, graphs, followed by  a live demonstration of my software projected from my laptop.  My preparation had been meticulous: It had to be: A year’s hard work was at stake, so I’d prepared it to perfection.  I stood up and took them all in, with a gaze of sublime confidence. Then the laptop expired. There are several possible alternative plans of action when this happens     A. Stare at the smoking laptop vacuously, flapping ones mouth slowly up and down     B. Stand frozen like a statue, locked in indecision between fright and flight.     C. Run out of the room, weeping     D. Pretend that this was all planned     E. Abandon the presentation in favour of a stilted and tedious dissertation about the software     F. Shake your fist at the sky, and curse the sense of humour of your preferred deity I started for a few seconds on plan B, normally referred to as the ‘Rabbit in the headlamps of the car’ technique. Suddenly, a little voice inside my head spoke. It spoke the famous inane words of Yogi Berra; ‘The game isn't over until it's over.’ ‘Too right’, I thought. What to do? I ran through the alternatives A-F inclusive in my mind but none appealed to me. I was completely unprepared for this. Nowadays, longevity has since taught me more than I wanted to know about the wacky sense of humour of fate, and I would have taken two laptops. I hadn’t, but decided to do the presentation anyway as planned. I started out ignoring the dead laptop, but pretending, instead that it was still working. The audience looked startled. They were expecting plan B to be succeeded by plan C, I suspect. They weren’t used to denial on this scale. After my introductory talk, which didn’t require any visuals, I came to the diagram that described the application I’d written.  I’d taken ages over it and it was hot stuff. Well, it would have been had it been projected onto the screen. It wasn’t. Before I describe what happened then, I must explain that I have thespian tendencies.  My  triumph as Professor Higgins in My Fair Lady at the local operatic society is now long forgotten, but I remember at the time of my finest performance, the moment that, glancing up over the vast audience of  moist-eyed faces at the during the poignant  scene between Eliza and Higgins at the end, I  realised that I had a talent that one day could possibly  be harnessed for commercial use I just talked about the diagram as if it was there, but throwing in some extra description. The audience nodded helpfully when I’d done enough. Emboldened, I began a sort of mime, well, more of a ballet, to represent each slide as I came to it. Heaven knows I’d done my preparation and, in my mind’s eye, I could see every detail, but I had to somehow project the reality of that vision to the audience, much the same way any actor playing Macbeth should do the ghost of Banquo.  My desperation gave me a manic energy. If you’ve ever demonstrated a windows application entirely by mime, gesture and florid description, you’ll understand the scale of the challenge, but then I had nothing to lose. With a brief sentence of description here and there, and arms flailing whilst outlining the size and shape of  graphs and diagrams, I used the many tricks of mime, gesture and body-language  learned from playing Captain Hook, or the Sheriff of Nottingham in pantomime. I set out determinedly on my desperate venture. There wasn’t time to do anything but focus on the challenge of the task: the world around me narrowed down to ten faces and my presentation: ten souls who had to be hypnotized into seeing a Windows application:  one that was slick, well organized and functional I don’t remember the details. Eight minutes of my life are gone completely. I was a thespian berserker.  I know however that I followed the basic plan of building the presentation in a carefully controlled crescendo until the dazzling finale where the results were displayed on-screen.  ‘And here you see the results, neatly formatted and grouped carefully to enhance the significance of the figures, together with running trend-graphs!’ I waved a mime to signify an animated  window-opening, and looked up, in my first pause, to gaze defiantly  at the audience.  It was a sight I’ll never forget. Ten pairs of eyes were gazing in rapt attention at the imaginary window, and several pairs of eyes were glancing at the imaginary graphs and figures.  I hadn’t had an audience like that since my starring role in  Beauty and the Beast.  At that moment, I realized that my desperate ploy might work. I sat down, slightly winded, when my ten minutes were up.  For the first and last time in my life, the audience of a  ‘PowerPoint’ presentation burst into spontaneous applause. ‘Any questions?’ ‘Yes,  Have you got an agent?’ Yes, in case you’re wondering, I got the deal. They bought the software product from me there and then. However, it was a life-changing experience for me and I have never ever again trusted technology as part of a presentation.  Even if things can’t go wrong, they’ll go wrong and they’ll kill the flow of what you’re presenting.  if you can’t do something without the techno-props, then you shouldn’t do it.  The greatest lesson of all is that great presentations require preparation and  ‘stage-presence’ rather than fancy graphics. They’re a great supporting aid, but they should never dominate to the point that you’re lost without them.

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  • Source-control 'wet-work'?

    - by Phil Factor
    When a design or creative work is flawed beyond remedy, it is often best to destroy it and start again. The other day, I lost the code to a long and intricate SQL batch I was working on. I’d thought it was impossible, but it happened. With all the technology around that is designed to prevent this occurring, this sort of accident has become a rare event.  If it weren’t for a deranged laptop, and my distraction, the code wouldn’t have been lost this time.  As always, I sighed, had a soothing cup of tea, and typed it all in again.  The new code I hastily tapped in  was much better: I’d held in my head the essence of how the code should work rather than the details: I now knew for certain  the start point, the end, and how it should be achieved. Instantly the detritus of half-baked thoughts fell away and I was able to write logical code that performed better.  Because I could work so quickly, I was able to hold the details of all the columns and variables in my head, and the dynamics of the flow of data. It was, in fact, easier and quicker to start from scratch rather than tidy up and refactor the existing code with its inevitable fumbling and half-baked ideas. What a shame that technology is now so good that developers rarely experience the cleansing shock of losing one’s code and having to rewrite it from scratch.  If you’ve never accidentally lost  your code, then it is worth doing it deliberately once for the experience. Creative people have, until Technology mistakenly prevented it, torn up their drafts or sketches, threw them in the bin, and started again from scratch.  Leonardo’s obsessive reworking of the Mona Lisa was renowned because it was so unusual:  Most artists have been utterly ruthless in destroying work that didn’t quite make it. Authors are particularly keen on writing afresh, and the results are generally positive. Lawrence of Arabia actually lost the entire 250,000 word manuscript of ‘The Seven Pillars of Wisdom’ by accidentally leaving it on a train at Reading station, before rewriting a much better version.  Now, any writer or artist is seduced by technology into altering or refining their work rather than casting it dramatically in the bin or setting a light to it on a bonfire, and rewriting it from the blank page.  It is easy to pick away at a flawed work, but the real creative process is far more brutal. Once, many years ago whilst running a software house that supplied commercial software to local businesses, I’d been supervising an accounting system for a farming cooperative. No packaged system met their needs, and it was all hand-cut code.  For us, it represented a breakthrough as it was for a government organisation, and success would guarantee more contracts. As you’ve probably guessed, the code got mangled in a disk crash just a week before the deadline for delivery, and the many backups all proved to be entirely corrupted by a faulty tape drive.  There were some fragments left on individual machines, but they were all of different versions.  The developers were in despair.  Strangely, I managed to re-write the bulk of a three-month project in a manic and caffeine-soaked weekend.  Sure, that elegant universally-applicable input-form routine was‘nt quite so elegant, but it didn’t really need to be as we knew what forms it needed to support.  Yes, the code lacked architectural elegance and reusability. By dawn on Monday, the application passed its integration tests. The developers rose to the occasion after I’d collapsed, and tidied up what I’d done, though they were reproachful that some of the style and elegance had gone out of the application. By the delivery date, we were able to install it. It was a smaller, faster application than the beta they’d seen and the user-interface had a new, rather Spartan, appearance that we swore was done to conform to the latest in user-interface guidelines. (we switched to Helvetica font to look more ‘Bauhaus’ ). The client was so delighted that he forgave the new bugs that had crept in. I still have the disk that crashed, up in the attic. In IT, we have had mixed experiences from complete re-writes. Lotus 123 never really recovered from a complete rewrite from assembler into C, Borland made the mistake with Arago and Quattro Pro  and Netscape’s complete rewrite of their Navigator 4 browser was a white-knuckle ride. In all cases, the decision to rewrite was a result of extreme circumstances where no other course of action seemed possible.   The rewrite didn’t come out of the blue. I prefer to remember the rewrite of Minix by young Linus Torvalds, or the rewrite of Bitkeeper by a slightly older Linus.  The rewrite of CP/M didn’t do too badly either, did it? Come to think of it, the guy who decided to rewrite the windowing system of the Xerox Star never regretted the decision. I’ll agree that one should often resist calls for a rewrite. One of the worst habits of the more inexperienced programmer is to denigrate whatever code he or she inherits, and then call loudly for a complete rewrite. They are buoyed up by the mistaken belief that they can do better. This, however, is a different psychological phenomenon, more related to the idea of some motorcyclists that they are operating on infinite lives, or the occasional squaddies that if they charge the machine-guns determinedly enough all will be well. Grim experience brings out the humility in any experienced programmer.  I’m referring to quite different circumstances here. Where a team knows the requirements perfectly, are of one mind on methodology and coding standards, and they already have a solution, then what is wrong with considering  a complete rewrite? Rewrites are so painful in the early stages, until that point where one realises the payoff, that even I quail at the thought. One needs a natural disaster to push one over the edge. The trouble is that source-control systems, and disaster recovery systems, are just too good nowadays.   If I were to lose this draft of this very blog post, I know I’d rewrite it much better. However, if you read this, you’ll know I didn’t have the nerve to delete it and start again.  There was a time that one prayed that unreliable hardware would deliver you from an unmaintainable mess of a codebase, but now technology has made us almost entirely immune to such a merciful act of God. An old friend of mine with long experience in the software industry has long had the idea of the ‘source-control wet-work’,  where one hires a malicious hacker in some wild eastern country to hack into one’s own  source control system to destroy all trace of the source to an application. Alas, backup systems are just too good to make this any more than a pipedream. Somehow, it would be difficult to promote the idea. As an alternative, could one construct a source control system that, on doing all the code-quality metrics, would systematically destroy all trace of source code that failed the quality test? Alas, I can’t see many managers buying into the idea. In reading the full story of the near-loss of Toy Story 2, it set me thinking. It turned out that the lucky restoration of the code wasn’t the happy ending one first imagined it to be, because they eventually came to the conclusion that the plot was fundamentally flawed and it all had to be rewritten anyway.  Was this an early  case of the ‘source-control wet-job’?’ It is very hard nowadays to do a rapid U-turn in a development project because we are far too prone to cling to our existing source-code.

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  • Adding complexity to remove duplicate code

    - by Phil
    I have several classes that all inherit from a generic base class. The base class contains a collection of several objects of type T. Each child class needs to be able to calculate interpolated values from the collection of objects, but since the child classes use different types, the calculation varies a tiny bit from class to class. So far I have copy/pasted my code from class to class and made minor modifications to each. But now I am trying to remove the duplicated code and replace it with one generic interpolation method in my base class. However that is proving to be very difficult, and all the solutions I have thought of seem way too complex. I am starting to think the DRY principle does not apply as much in this kind of situation, but that sounds like blasphemy. How much complexity is too much when trying to remove code duplication? EDIT: The best solution I can come up with goes something like this: Base Class: protected T GetInterpolated(int frame) { var index = SortedFrames.BinarySearch(frame); if (index >= 0) return Data[index]; index = ~index; if (index == 0) return Data[index]; if (index >= Data.Count) return Data[Data.Count - 1]; return GetInterpolatedItem(frame, Data[index - 1], Data[index]); } protected abstract T GetInterpolatedItem(int frame, T lower, T upper); Child class A: public IGpsCoordinate GetInterpolatedCoord(int frame) { ReadData(); return GetInterpolated(frame); } protected override IGpsCoordinate GetInterpolatedItem(int frame, IGpsCoordinate lower, IGpsCoordinate upper) { double ratio = GetInterpolationRatio(frame, lower.Frame, upper.Frame); var x = GetInterpolatedValue(lower.X, upper.X, ratio); var y = GetInterpolatedValue(lower.Y, upper.Y, ratio); var z = GetInterpolatedValue(lower.Z, upper.Z, ratio); return new GpsCoordinate(frame, x, y, z); } Child class B: public double GetMph(int frame) { ReadData(); return GetInterpolated(frame).MilesPerHour; } protected override ISpeed GetInterpolatedItem(int frame, ISpeed lower, ISpeed upper) { var ratio = GetInterpolationRatio(frame, lower.Frame, upper.Frame); var mph = GetInterpolatedValue(lower.MilesPerHour, upper.MilesPerHour, ratio); return new Speed(frame, mph); }

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  • Strange javascript error when using Kongregates API

    - by Phil
    In the hopes of finding a fellow unity3d developer also aiming for the Kongregate contest.. I've implemented the Kongregate API and can see that the game receives a call with my username and presents it ingame. I'm using Application.ExternalCall("kongregate.stats.submit",type,amount); where type is a string "Best Score" and amount is an int (1000 or something). This is the error I'm getting: You are trying to call recursively into the Flash Player which is not allowed. In most cases the JavaScript setTimeout function, can be used as a workaround. callASFunction:function(a,b){if(FABrid...tion, can be used as a workaround."); I'm wondering, has anyone else had this error or am I somehow doing something stupid? Thanks!

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  • If I use my own normal values, should I turn off winding order culling?

    - by Phil
    I've discovered that I managed to program a series of boxes with indexed vertices in such a way that every other triangle (Half of each face) has a backwards winding order. As a result, XNA is culling half of them. However, my Vertex objects contain normal data that I have explicitly set, and I am going to implement my own backface culling shortly to reduce the size of the VertexBuffer. Should I turn off winding order culling and manage it myself, or should I make sure the winding order is consistent and let XNA handle it?

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  • Weird rotation problem

    - by Phil
    I'm creating a simple tank game. No matter what I do, the turret keeps facing the target with it's side. I just can't figure out how to turn it 90 degrees in Y once so it faces it correctly. I've checked the pivot in Maya and it doesn't matter how I change it. This is the code I use to calculate how to face the target: void LookAt() { var forwardA = transform.forward; var forwardB = (toLookAt.transform.position - transform.position); var angleA = Mathf.Atan2(forwardA.x, forwardA.z) * Mathf.Rad2Deg; var angleB = Mathf.Atan2(forwardB.x, forwardB.z) * Mathf.Rad2Deg; var angleDiff = Mathf.DeltaAngle(angleA, angleB); //print(angleDiff.ToString()); if (angleDiff > 20) { //Rotate to transform.Rotate(new Vector3(0, (-turretSpeed * Time.deltaTime),0)); //transform.rotation = new Quaternion(transform.rotation.x, transform.rotation.y + adjustment, transform.rotation.z, transform.rotation.w); } else if (angleDiff < 20) { transform.Rotate(new Vector3(0, (turretSpeed * Time.deltaTime),0)); //transform.rotation = new Quaternion(transform.rotation.x, transform.rotation.y + adjustment, transform.rotation.z, transform.rotation.w); } else { } } I'm using Unity3d and would appreciate any help I can get! Thanks!

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  • Learn Many Languages

    - by Phil Factor
    Around twenty-five years ago, I was trying to solve the problem of recruiting suitable developers for a large business. I visited the local University (it was a Technical College then). My mission was to remind them that we were a large, local employer of technical people and to suggest that, as they were in the business of educating young people for a career in IT, we should work together. I anticipated a harmonious chat where we could suggest to them the idea of mentioning our name to some of their graduates. It didn’t go well. The academic staff displayed a degree of revulsion towards the whole topic of IT in the world of commerce that surprised me; tweed met charcoal-grey, trainers met black shoes. However, their antipathy to commerce was something we could have worked around, since few of their graduates were destined for a career as university lecturers. They asked me what sort of language skills we needed. I tried ducking the invidious task of naming computer languages, since I wanted recruits who were quick to adapt and learn, with a broad understanding of IT, including development methodologies, technologies, and data. However, they pressed the point and I ended up saying that we needed good working knowledge of C and BASIC, though FORTRAN and COBOL were, at the time, still useful. There was a ghastly silence. It was as if I’d recommended the beliefs and practices of the Bogomils of Bulgaria to a gathering of Cardinals. They stared at me severely, like owls, until the head of department broke the silence, informing me in clipped tones that they taught only Modula 2. Now, I wouldn’t blame you if at this point you hurriedly had to look up ‘Modula 2′ on Wikipedia. Based largely on Pascal, it was a specialist language for embedded systems, but I’ve never ever come across it in a commercial business application. Nevertheless, it was an excellent teaching language since it taught modules, scope control, multiprogramming and the advantages of encapsulating a set of related subprograms and data structures. As long as the course also taught how to transfer these skills to other, more useful languages, it was not necessarily a problem. I said as much, but they gleefully retorted that the biggest local employer, a defense contractor specializing in Radar and military technology, used nothing but Modula 2. “Why teach any other programming language when they will be using Modula 2 for all their working lives?” said a complacent lecturer. On hearing this, I made my excuses and left. There could be no meeting of minds. They were providing training in a specific computer language, not an education in IT. Twenty years later, I once more worked nearby and regularly passed the long-deserted ‘brownfield’ site of the erstwhile largest local employer; the end of the cold war had led to lean times for defense contractors. A digger was about to clear the rubble of the long demolished factory along with the accompanying growth of buddleia and thistles, in order to lay the infrastructure for ‘affordable housing’. Modula 2 was a distant memory. Either those employees had short working lives or they’d retrained in other languages. The University, by contrast, was thriving, but I wondered if their erstwhile graduates had ever cursed the narrow specialization of their training in IT, as they struggled with the unexpected variety of their subsequent careers.

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  • I want to host clients' websites, but not their email. What's the easiest way to handle this?

    - by Phil
    My company lets non-technical users build their own niche industry websites on our server, which we host. they can currently point their nameservers at their registrar to us, which ends up with them no longer having access to their email if they've already set it up through said registrar. We don't want to interfere with their existing email, nor do we want to get into the business of setting up email for them through our service. Thus, having them point A records/cname to us would work, but is this too complex for a non-technie user? We thought of having them point nameservers to us but pointing the MX records back to them, but this is also beyond their scope. Is there an easy way to 'point records' at their initial state? Any other ideas/feedback?

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  • Sitting Pretty

    - by Phil Factor
    Guest Editorial for Simple-Talk IT Pro newsletter'DBAs and SysAdmins generally prefer an expression of calmness under adversity. It is a subtle trick, and requires practice in front of a mirror to get it just right. Too much adversity and they think you're not coping; too much calmness and they think you're under-employed' I dislike the term 'avatar', when used to describe a portrait photograph. An avatar, in the sense of a picture, is merely the depiction of one's role-play alter-ego, often a ridiculous bronze-age deity. However, professional image is important. The choice and creation of online photos has an effect on the way your message is received and it is important to get that right. It is fine to use that photo of you after ten lagers on holiday in an Ibiza nightclub, but what works on Facebook looks hilarious on LinkedIn. My splendid photograph that I use online was done by a professional photographer at great expense and I've never had the slightest twinge of regret when I remember how much I paid for it. It is me, but a more pensive and dignified edition, oozing trust and wisdom. One gasps at the magical skill that a professional photographer can conjure up, without digital manipulation, to make the best of a derisory noggin (ed: slang for a head). Even if he had offered to depict me as a semi-naked, muscle-bound, sword-wielding hero, I'd have demurred. No, any professional person needs a carefully cultivated image that looks right. I'd never thought of using that profile shot, though I couldn't help noticing the photographer flinch slightly when he first caught sight of my face. There is a problem with using an avatar. The use of a single image doesn't express the appropriate emotion. At the moment, it is weird to see someone with a laughing portrait writing something solemn. A neutral cast to the face, somewhat like a passport photo, is probably the best compromise. Actually, the same is true of a working life in IT. One of the first skills I learned was not to laugh at managers, but, instead, to develop a facial expression that promoted a sense of keenness, energy and respect. Every profession has its own preferred facial cast. A neighbour of mine has the natural gift of a face that displays barely repressed grief. Though he is characteristically cheerful, he earns a remarkable income as a pallbearer. DBAs and SysAdmins generally prefer an expression of calmness under adversity. It is a subtle trick, and requires practice in front of a mirror to get it just right. Too much adversity and they think you're not coping; too much calmness and they think you're under-employed. With an appropriate avatar, you could do away with a lot of the need for 'smilies' to give clues as to the meaning of what you've written on forums and blogs. If you had a set of avatars, showing the full gamut of human emotions expressible in writing: Rage, fear, reproach, joy, ebullience, apprehension, exasperation, dissembly, irony, pathos, euphoria, remorse and so on. It would be quite a drop-down list on forums, but given the vast prairies of space on the average hard drive, who cares? It would cut down on the number of spats in Forums just as long as one picks the right avatar. As an unreconstructed geek, I find it hard to admit to the value of image in the workplace, but it is true. Just as we use professionals to tidy up and order our CVs and job applications, we should employ experts to enhance our professional image. After all you don't perform surgery or dentistry on yourself do you?

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  • No boot record when installing 13.04 from USB on WinXP

    - by Phil Leslie
    I'm replacing WinXP with 13.04 on an older PC using wubi.exe on a USB stick. I had no problem changing the BIOS on another system that was a bit newer but when I change the settings on the older PC to boot from USB, I get a DOS message saying "Searching for boot record...Not found" & asked to try again. I don't have the ability to boot from a live CD so is there a reason why I can boot from a USB on a newer computer but can't from an older one? Both have options to choose to boot from USB, but the older one can find no boot record. The system was built on 12/13/01 by American Megatrends. Since I don't have enough "reputation points" to post the screen shot image, you can see it at http://img.photobucket.com/albums/v633/boonevillephil/1029131748-00.jpg.

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  • best way to cleanly display 15-20 youtube videos in a webpage?

    - by Phil
    I am currently building a website for a client who has about 20 or so videos that he wants put on a video gallery page and I was wondering if you guys could help me out and give me some advice on how to go about this. I have found yoxview, possibly lightbox... but I don't know if that popup window is really good for video browsing. Also, should/could this be asked in the webmasters instead of stackoverflow?

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  • Musings on the launch of SQL Monitor

    - by Phil Factor
    For several years, I was responsible for the smooth running of a large number of enterprise database servers. We ran a network monitoring tool that was primitive by today’s standards but which performed the useful function of polling every system, including all the Servers in my charge. It ran a configurable script for each service that you needed to monitor that was merely required to return one of a number of integer values. These integer values represented the pain level of the service, from 10 (“hurtin’ real bad”) to 1 (“Things is great”). Not only could you program the visual appearance of each server on the network diagram according to the value of the integer, but you could even opt to run a sound file. Very soon, we had a large TFT Screen, high on the wall of the server room, with every server represented by an icon, and a speaker next to it that would give out a series of grunts, groans, snores, shrieks and funeral marches, depending on the problem. One glance at the display, and you could dive in with iSQL/QA/SSMS and check what was going on with your favourite diagnostic tools. If you saw a server icon burst into flames on the screen or droop like a jelly, you dropped your mug of coffee to do it.  It was real fun, but I remember it more for the huge difference it made to have that real-time visibility into how your servers are performing. The management soon stopped making jokes about the real reason we wanted the TFT screen. (It rendered DVDs beautifully they said; particularly flesh-tints). If you are instantly alerted when things start to go wrong, then there was a good chance you could fix it before being alerted to the problem by the users of the system.  There is a world of difference between this sort of tool, one that gives whoever is ‘on watch’ in the server room the first warning of a potential problem on one of any number of servers, and the breed of tool that attempts to provide some sort of prosthetic DBA Brain. I like to get the early warning, to get the right information to help to diagnose a problem: No auto-fix, but just the information. I prefer to leave the task of ascertaining the exact cause of a problem to my own routines, custom code, intuition and forensic instincts. A simulated aircraft cockpit doesn’t do anything for me, especially before I know where I should be flying.  Time has moved on, and that TFT screen is now, with SQL Monitor, an iPad or any other mobile or static device that can support a browser. Rather than trying to reproduce the conceptual topology of the servers, it lists them in their groups so as to give a display that scales with the increasing number of databases you monitor.  It gives the history of the major events and trends for the servers. It gives the icons and colours that you can spot out of the corner of your eye, but goes on to give you just enough information in drill-down to give you a much clearer idea of where to look with your DBA tools and routines. It doesn't swamp you with information.  Whereas a few server and database-level problems are pretty easily fixed, others depend on judgement and experience to sort out.  Although the idea of an application that automates the bulk of a DBA’s skills is attractive to many, I can’t see it happening soon. SQL Server’s complexity increases faster than the panaceas can be created. In the meantime, I believe that the best way of helping  DBAs  is to make the monitoring process as simple and effective as possible,  and provide the right sort of detail and ‘evidence’ to allow them to decide on the fix. In the end, it is still down to the skill of the DBA.

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  • Hadoop, NOSQL, and the Relational Model

    - by Phil Factor
    (Guest Editorial for the IT Pro/SysAdmin Newsletter)Whereas Relational Databases fit the world of commerce like a glove, it is useless to pretend that they are a perfect fit for all human endeavours. Although, with SQL Server, we’ve made great strides with indexing text, in processing spatial data and processing markup, there is still a problem in dealing efficiently with large volumes of ephemeral semi-structured data. Key-value stores such as Cassandra, Project Voldemort, and Riak are of great value for ephemeral data, and seem of equal value as a data-feed that provides aggregations to an RDBMS. However, the Document databases such as MongoDB and CouchDB are ideal for semi-structured data for which no fixed schema exists; analytics and logging are obvious examples. NoSQL products, such as MongoDB, tackle the semi-structured data problem with panache. MongoDB is designed with a simple document-oriented data model that scales horizontally across multiple servers. It doesn’t impose a schema, and relies on the application to enforce the data structure. This is another take on the old ‘EAV’ problem (where you don’t know in advance all the attributes of a particular entity) It uses a clever replica set design that allows automatic failover, and uses journaling for data durability. It allows indexing and ad-hoc querying. However, for SQL Server users, the obvious choice for handling semi-structured data is Apache Hadoop. There will soon be an ODBC Driver for Apache Hive .and an Add-in for Excel. Additionally, there are now two Hadoop-based connectors for SQL Server; the Apache Hadoop connector for SQL Server 2008 R2, and the SQL Server Parallel Data Warehouse (PDW) connector. We can connect to Hadoop process the semi-structured data and then store it in SQL Server. For one steeped in the culture of Relational SQL Databases, I might be expected to throw up my hands in the air in a gesture of contempt for a technology that was, judging by the overblown journalism on the subject, about to make my own profession as archaic as the Saggar makers bottom knocker (a potter’s assistant who helped the saggar maker to make the bottom of the saggar by placing clay in a metal hoop and bashing it). However, on the contrary, I find that I'm delighted with the advances made by the NoSQL databases in the past few years. Having the flow of ideas from the NoSQL providers will knock any trace of complacency out of the providers of Relational Databases and inspire them into back-fitting some features, such as horizontal scaling, with sharding and automatic failover into SQL-based RDBMSs. It will do the breed a power of good to benefit from all this lateral thinking.

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  • What would most games benefit from having?

    - by Phil
    I think I've seen "questions" like this on stackoverflow but sorry if I'm overstepping any bounds. Inspired by my recent question and all the nice answers (Checklist for finished game?) I think every gamedev out there has something he/she thinks that almost every game should have. That knowledge is welcome here! So this is probably going to be an inspirational subjective list of some sorts and the point is that anyone reading this question will see a point or two that they've overlooked in their own development and might benefit from adding. I think a good example might be: "some sort of manual or help section. Of course it should be proportional to how advanced the game is. Some users won't need it and won't go looking for it but the other ones that do will become very frustrated if they can't remember how to do something specific that should be in the manual". A bad example might be "good gameplay". Of course every game benefits from this but the answer is not very helpful.

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  • Alternatives for saving data with jquery

    - by Phil Vallone
    I am not sure if this question is considered too broad, but I would like to reach out to my fellow programmers to see what alternatives are out there for saving data using jquery. I have a content management system that generates an set of HTML pages called an IETM (Interactive Electronic Technical Manual). The HTML pages are written in HTML and uses jquery. The ITEM is meant to be light weight, portable and run on most modern browsers. I am looking for a way to save data. I have considered cookies and sqlite. Are there any other alternatives for saving data using jquery?

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  • A Knights Tale

    - by Phil Factor
    There are so many lessons to be learned from the story of Knight Capital losing nearly half a billion dollars as a result of a deployment gone wrong. The Knight Capital Group (KCG N) was an American global financial services firm engaging in market making, electronic execution, and institutional sales and trading. According to the recent order (File No.3.15570) against Knight Capital by U.S. Securities and Exchange Commission?, Knight had, for many years used some software which broke up incoming “parent” orders into smaller “child” orders that were then transmitted to various exchanges or trading venues for execution. A tracking ‘cumulative quantity’ function counted the number of ‘child’ orders and stopped the process once the total of child orders matched the ‘parent’ and so the parent order had been completed. Back in the mists of time, some code had been added to it  which was excuted if a particular flag was set. It was called ‘power peg’ and seems to have had a similar design and purpose, but, one guesses, would have shared the same tracking function. This code had been abandoned in 2003, but never deleted. In 2005, The tracking function was moved to an earlier point in the main process. It would seem from the account that, from that point, had that flag ever been set, the old ‘Power Peg’ would have been executed like Godzilla bursting from the ice, making child orders without limit without any tracking function. It wasn’t, presumably because the software that set the flag was removed. In 2012, nearly a decade after ‘Power Peg’ was abandoned, Knight prepared a new module to their software to cope with the imminent Retail Liquidity Program (RLP) for the New York Stock Exchange. By this time, the flag had remained unused and someone made the fateful decision to reuse it, and replace the old ‘power peg’ code with this new RLP code. Had the two actions been done together in a single automated deployment, and the new deployment tested, all would have been well. It wasn’t. To quote… “Beginning on July 27, 2012, Knight deployed the new RLP code in SMARS in stages by placing it on a limited number of servers in SMARS on successive days. During the deployment of the new code, however, one of Knight’s technicians did not copy the new code to one of the eight SMARS computer servers. Knight did not have a second technician review this deployment and no one at Knight realized that the Power Peg code had not been removed from the eighth server, nor the new RLP code added. Knight had no written procedures that required such a review.” (para 15) “On August 1, Knight received orders from broker-dealers whose customers were eligible to participate in the RLP. The seven servers that received the new code processed these orders correctly. However, orders sent with the repurposed flag to the eighth server triggered the defective Power Peg code still present on that server. As a result, this server began sending child orders to certain trading centers for execution. Because the cumulative quantity function had been moved, this server continuously sent child orders, in rapid sequence, for each incoming parent order without regard to the number of share executions Knight had already received from trading centers. Although one part of Knight’s order handling system recognized that the parent orders had been filled, this information was not communicated to SMARS.” (para 16) SMARS routed millions of orders into the market over a 45-minute period, and obtained over 4 million executions in 154 stocks for more than 397 million shares. By the time that Knight stopped sending the orders, Knight had assumed a net long position in 80 stocks of approximately $3.5 billion and a net short position in 74 stocks of approximately $3.15 billion. Knight’s shares dropped more than 20% after traders saw extreme volume spikes in a number of stocks, including preferred shares of Wells Fargo (JWF) and semiconductor company Spansion (CODE). Both stocks, which see roughly 100,000 trade per day, had changed hands more than 4 million times by late morning. Ultimately, Knight lost over $460 million from this wild 45 minutes of trading. Obviously, I’m interested in all this because, at one time, I used to write trading systems for the City of London. Obviously, the US SEC is in a far better position than any of us to work out the failings of Knight’s IT department, and the report makes for painful reading. I can’t help observing, though, that even with the breathtaking mistakes all along the way, that a robust automated deployment process that was ‘all-or-nothing’, and tested from soup to nuts would have prevented the disaster. The report reads like a Greek Tragedy. All the way along one wants to shout ‘No! not that way!’ and ‘Aargh! Don’t do it!’. As the tragedy unfolds, the audience weeps for the players, trapped by a cruel fate. All application development and deployment requires defense in depth. All IT goes wrong occasionally, but if there is a culture of defensive programming throughout, the consequences are usually containable. For financial systems, these defenses are required by statute, and ignored only by the foolish. Knight’s mistakes weren’t made by just one hapless sysadmin, but were progressive errors by an  IT culture spanning at least ten years.  One can spell these out, but I think they’re obvious. One can only hope that the industry studies what happened in detail, learns from the mistakes, and draws the right conclusions.

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