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• E.T. Phone "Home" - Hey I've discovered a leak..!

  - by Martin Deh

  Being a member of the WebCenter ATEAM, we are often asked to performance tune a WebCenter custom portal application or a WebCenter Spaces deployment.  Most of the time, the process is pretty much the same.  For example, we often use tools like httpWatch and FireBug to monitor the application, and then perform load tests using JMeter or Selenium.  In addition, there are the fine tuning of the different performance based tuning parameters that are outlined in the documentation and by blogs that have been written by my fellow ATEAMers (click on the "performance" tag in this ATEAM blog).  While performing the load test where the outcome produces a significant reduction in the systems resources (memory), one of the causes that plays a role in memory "leakage" is due to the implementation of the navigation menu UI.  OOTB in both JDeveloper and WebCenter Spaces, there are sample (page) templates that include a "default" navigation menu.  In WebCenter Spaces, this is through the SpacesNavigationModel taskflow region, and in a custom portal (i.e. pageTemplate_globe.jspx) the menu UI is contructed using standard ADF components.  These sample menu UI's basically enable the underlying navigation model to visualize itself to some extent.  However, due to certain limitations of these sample menu implementations (i.e. deeper sub-level of navigations items, look-n-feel, .etc), many customers have developed their own custom navigation menus using a combination of HTML, CSS and JQuery.  While this is supported somewhat by the framework, it is important to know what are some of the best practices in ensuring that the navigation menu does not leak.  In addition, in this blog I will point out a leak (BUG) that is in the sample templates.  OK, E.T. the suspence is killing me, what is this leak? Note: for those who don't know, info on E.T. can be found here In both of the included templates, the example given for handling the navigation back to the "Home" page, will essentially provide a nice little memory leak every time the link is clicked. Let's take a look a simple example, which uses the default template in Spaces. The outlined section below is the "link", which is used to enable a user to navigation back quickly to the Group Space Home page. When you (mouse) hover over the link, the browser displays the target URL. From looking initially at the proposed URL, this is the intended destination.  Note: "home" in this case is the navigation model reference (id), that enables the display of the "pretty URL". Next, notice the current URL, which is displayed in the browser.  Remember, that PortalSiteHome = home.  The other highlighted item adf.ctrl-state, is very important to the framework.  This item is basically a persistent query parameter, which is used by the (ADF) framework to managing the current session and page instance.  Without this parameter present, among other things, the browser back-button navigation will fail.  In this example, the value for this parameter is currently 95K25i7dd_4.  Next, through the navigation menu item, I will click on the Page2 link. Inspecting the URL again, I can see that it reports that indeed the navigation is successful and the adf.ctrl-state is also in the URL.  For those that are wondering why the URL displays Page3.jspx, instead of Page2.jspx. Basically the (file) naming convention for pages created ar runtime in Spaces start at Page1, and then increment as you create additional pages.  The name of the actual link (i.e. Page2) is the page "title" attribute.  So the moral of the story is, unlike design time created pages, run time created pages the name of the file will 99% never match the name that appears in the link. Next, is to click on the quick link for navigating back to the Home page. Quick investigation yields that the navigation was indeed successful.  In the browser's URL there is a home (pretty URL) reference, and there is also a reference to the adf.ctrl-state parameter.  So what's the issue?  Can you remember what the value was for the adf.ctrl-state?  The current value is 3D95k25i7dd_149.  However, the previous value was 95k25i7dd_4.  Here is what happened.  Remember when (mouse) hovering over the link produced the following target URL: http://localhost:8888/webcenter/spaces/NavigationTest/home This is great for the browser as this URL will navigate to the intended targer.  However, what is missing is the adf.ctrl-state parameter.  Since this parameter was not present upon navigation "within" the framework, the ADF framework produced another adf.ctrl-state (object).  The previous adf.ctrl-state basically is orphaned while continuing to be alive in memory.  Note: the auto-creation of the adf.ctrl state does happen initially when you invoke the Spaces application  for the first time.  The following is the line of code which produced the issue: <af:goLink destination="#{boilerBean.globalLogoURIInSpace} ... Here the boilerBean is responsible for returning the "string" url, which in this case is /spaces/NavigationTest/home. Unfortunately, again what is missing is adf.ctrl-state. Note: there are more than one instance of the goLinks in the sample templates. So E.T. how can I correct this? There are 2 simple fixes.  For the goLink's destination, use the navigation model to return the actually "node" value, then use the goLinkPrettyUrl method to add the current adf.ctrl-state: <af:goLink destination="#{navigationContext.defaultNavigationModel.node['home'].goLinkPrettyUrl}"} ... />  Note: the node value is the [navigation model id]  Using a goLink does solve the main issue.  However, since the link basically does a redirect, some browsers like IE will produce a somewhat significant "flash".  In a Spaces application, this may be an annoyance to the users.  Another way to solve the leakage problem, and also remove the flash between navigations is to use a af:commandLink.  For example, here is the code example for this scenario: <af:commandLink id="pt_cl2asf" actionListener="#{navigationContext.processAction}" action="pprnav">    <f:attribute name="node" value="#{navigationContext.defaultNavigationModel.node['home']}"/> </af:commandLink> Here, the navigation node to where home is located is delivered by way of the attribute to the commandLink.  The actual navigation is performed by the processAction, which is needing the "node" value. E.T. OK, you solved the OOTB sample BUG, what about my custom navigation code? I have seen many implementations of creating a navigation menu through custom code.  In addition, there are some blog sites that also give detailed examples.  The majority of these implementations are very similar.  The code usually involves using standard HTML tags (i.e. DIVS, UL, LI, .,etc) and either CSS or JavaScript (JQuery) to produce the flyout/drop-down effect.  The navigation links in these cases are standard <a href... > tags.  Although, this type of approach is not fully accepted by the ADF community, it does work.  The important thing to note here is that the <a> tag value must use the goLinkPrettyURL method of contructing the target URL.  For example: <a href="${contextRoot}${menu.goLinkPrettyUrl}"> The main reason why this type of approach is popular is that links that are created this way (also with using af:goLinks), the pages become crawlable by search engines.  CommandLinks are currently not search friendly.  However, in the case of a Spaces instance this may be acceptable.  So in this use-case, af:commandLinks, which would replace the <a>  (or goLink) tags. The example code given of the af:commandLink above is still valid. One last important item.  If you choose to use af:commandLinks, special attention must be given to the scenario in which java script has been used to produce the flyout effect in the custom menu UI.  In many cases that I have seen, the commandLink can only be invoked once, since there is a conflict between the custom java script with the ADF frameworks own scripting to control the view.  The recommendation here, would be to use a pure CSS approach to acheive the dropdown effects. One very important thing to note.  Due to another BUG, the WebCenter environement must be patched to BP3 (patch  p14076906).  Otherwise the leak is still present using the goLinkPrettyUrl method.  Thanks E.T.!  Now I can phone home and not worry about my application running out of resources due to my custom navigation! 

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• Function-Local Static Const variable Initialization semantics.

  - by Hassan Syed

  The questions are in bold, for those that cannot be bothered reading a question in depth. This is a followup to this question. It is to do with the initialization semantics of static variables in functions. Static variables should be initialized once, and their internal state might be altered later - as I (currently) do in the linked question. However, the code in question does not require the feature to change the state of the variable later. Let me clarrify my position, since I don't require the string object's internal state to change. The code is for a trait class for meta programming, and as such would would benifit from a const char * const ptr -- thus Ideally a local cost static const variable is needed. My educated guess is that in this case the string in question will be optimally placed in memory by the link-loader, and that the code is more secure and maps to the intended semantics. This leads to the semantics of such a variable "The C++ Programming language Third Edition -- Stroustrup" does not have anything (that I could find) to say about this matter. All that is said is that the variable is initialized once when the flow of control of the thread first reaches the code. This leads me to ponder if the following code would be sensible, and if not what are the intended semantics ?. #include <iostream> const char * const GetString(const char * x_in) { static const char * const x = x_in; return x; } int main() { const char * const temp = GetString("yahoo"); std::cout << temp << std::endl; const char * const temp2 = GetString("yahoo2"); std::cout << temp2 << std::endl; } The following compiles on GCC and prints "yahoo" twice. Which is what I want -- However it might not be standards compliant (which is why I post this question). It might be more elegant to have two functions, "SetString" and "String" where the latter forwards to the first. If it is standards compliant does someone know of a templates implementation in boost (or elsewhere) ?

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• C++ and function pointers assessment: lack of inspiration

  - by OlivierDofus

  I've got an assessment to give to my students. It's about C++ and function pointers. Their skill is middle: it the first year of a programming school after bachelor. To give you something precise, here's a sample of a solution of one of 3 exercices they had to do in 30 minutes (the question was: "here's a version of a code that could be written with function pointers, write down the same thing but with function pointers"): typedef void (*fcPtr) (istream &); fcPtr ArrayFct [] = { Delete , Insert, Swap, Move }; void HandleCmd (const string && Cmd) { string AvalaibleCommands ("DISM"); string::size_type Pos; istringstream Flux (Cmd); char CodeOp; Flux >> CodeOp; Pos = AvalaibleCommands.find (toupper (CodeOp)); if (Pos != string::npos) { ArrayFct [Pos](Flux); } } Any idea where I could find some inspiration? Some of the students have understood the principles, even though it's very hard for them to write C++ code. I know them, I know they're clever, and I'm pretty sure they should be very good project managers. So, writing C++ code is not that important after all. Understanding is the most important part (IMHO). I'm wondering about maybe break the habits, and give half of the questions about the principle, or even better, give some sample in other language and ask them why it's better to use function pointers instead of classical programming (usually a big switch case). Any idea where I could look? Find some inspiration?

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• A Look Inside JSR 360 - CLDC 8

  - by Roger Brinkley

  If you didn't notice during JavaOne the Java Micro Edition took a major step forward in its consolidation with Java Standard Edition when JSR 360 was proposed to the JCP community. Over the last couple of years there has been a focus to move Java ME back in line with it's big brother Java SE. We see evidence of this in JCP itself which just recently merged the ME and SE/EE Executive Committees into a single Java Executive Committee. But just before that occurred JSR 360 was proposed and approved for development on October 29. So let's take a look at what changes are now being proposed. In a way JSR 360 is returning back to the original roots of Java ME when it was first introduced. It was indeed a subset of the JDK 4 language, but as Java progressed many of the language changes were not implemented in the Java ME. Back then the tradeoff was still a functionality, footprint trade off but the major market was feature phones. Today the market has changed and CLDC, while it will still target feature phones, will have it primary emphasis on embedded devices like wireless modules, smart meters, health care monitoring and other M2M devices. The major changes will come in three areas: language feature changes, library changes, and consolidating the Generic Connection Framework.  There have been three Java SE versions that have been implemented since JavaME was first developed so the language feature changes can be divided into changes that came in JDK 5 and those in JDK 7, which mostly consist of the project Coin changes. There were no language changes in JDK 6 but the changes from JDK 5 are: Assertions - Assertions enable you to test your assumptions about your program. For example, if you write a method that calculates the speed of a particle, you might assert that the calculated speed is less than the speed of light. In the example code below if the interval isn't between 0 and and 1,00 the an error of "Invalid value?" would be thrown. private void setInterval(int interval) { assert interval > 0 && interval <= 1000 : "Invalid value?" } Generics - Generics add stability to your code by making more of your bugs detectable at compile time. Code that uses generics has many benefits over non-generic code with: Stronger type checks at compile time. Elimination of casts. Enabling programming to implement generic algorithms. Enhanced for Loop - the enhanced for loop allows you to iterate through a collection without having to create an Iterator or without having to calculate beginning and end conditions for a counter variable. The enhanced for loop is the easiest of the new features to immediately incorporate in your code. In this tip you will see how the enhanced for loop replaces more traditional ways of sequentially accessing elements in a collection. void processList(Vector<string> list) { for (String item : list) { ... Autoboxing/Unboxing - This facility eliminates the drudgery of manual conversion between primitive types, such as int and wrapper types, such as Integer.  Hashtable<Integer, string=""> data = new Hashtable<>(); void add(int id, String value) { data.put(id, value); } Enumeration - Prior to JDK 5 enumerations were not typesafe, had no namespace, were brittle because they were compile time constants, and provided no informative print values. JDK 5 added support for enumerated types as a full-fledged class (dubbed an enum type). In addition to solving all the problems mentioned above, it allows you to add arbitrary methods and fields to an enum type, to implement arbitrary interfaces, and more. Enum types provide high-quality implementations of all the Object methods. They are Comparable and Serializable, and the serial form is designed to withstand arbitrary changes in the enum type. enum Season {WINTER, SPRING, SUMMER, FALL}; } private Season season; void setSeason(Season newSeason) { season = newSeason; } Varargs - Varargs eliminates the need for manually boxing up argument lists into an array when invoking methods that accept variable-length argument lists. The three periods after the final parameter's type indicate that the final argument may be passed as an array or as a sequence of arguments. Varargs can be used only in the final argument position. void warning(String format, String... parameters) { .. for(String p : parameters) { ...process(p);... } ... } Static Imports -The static import construct allows unqualified access to static members without inheriting from the type containing the static members. Instead, the program imports the members either individually or en masse. Once the static members have been imported, they may be used without qualification. The static import declaration is analogous to the normal import declaration. Where the normal import declaration imports classes from packages, allowing them to be used without package qualification, the static import declaration imports static members from classes, allowing them to be used without class qualification. import static data.Constants.RATIO; ... double r = Math.cos(RATIO * theta); Annotations - Annotations provide data about a program that is not part of the program itself. They have no direct effect on the operation of the code they annotate. There are a number of uses for annotations including information for the compiler, compiler-time and deployment-time processing, and run-time processing. They can be applied to a program's declarations of classes, fields, methods, and other program elements. @Deprecated public void clear(); The language changes from JDK 7 are little more familiar as they are mostly the changes from Project Coin: String in switch - Hey it only took us 18 years but the String class can be used in the expression of a switch statement. Fortunately for us it won't take that long for JavaME to adopt it. switch (arg) { case "-data": ... case "-out": ... Binary integral literals and underscores in numeric literals - Largely for readability, the integral types (byte, short, int, and long) can also be expressed using the binary number system. and any number of underscore characters (_) can appear anywhere between digits in a numerical literal. byte flags = 0b01001111; long mask = 0xfff0_ff08_4fff_0fffl; Multi-catch and more precise rethrow - A single catch block can handle more than one type of exception. In addition, the compiler performs more precise analysis of rethrown exceptions than earlier releases of Java SE. This enables you to specify more specific exception types in the throws clause of a method declaration. catch (IOException | InterruptedException ex) { logger.log(ex); throw ex; } Type Inference for Generic Instance Creation - Otherwise known as the diamond operator, the type arguments required to invoke the constructor of a generic class can be replaced with an empty set of type parameters (<>) as long as the compiler can infer the type arguments from the context.  map = new Hashtable<>(); Try-with-resource statement - The try-with-resources statement is a try statement that declares one or more resources. A resource is an object that must be closed after the program is finished with it. The try-with-resources statement ensures that each resource is closed at the end of the statement.  try (DataInputStream is = new DataInputStream(...)) { return is.readDouble(); } Simplified varargs method invocation - The Java compiler generates a warning at the declaration site of a varargs method or constructor with a non-reifiable varargs formal parameter. Java SE 7 introduced a compiler option -Xlint:varargs and the annotations @SafeVarargs and @SuppressWarnings({"unchecked", "varargs"}) to supress these warnings. On the library side there are new features that will be added to satisfy the language requirements above and some to improve the currently available set of APIs.  The library changes include: Collections update - New Collection, List, Set and Map, Iterable and Iteratator as well as implementations including Hashtable and Vector. Most of the work is too support generics String - New StringBuilder and CharSequence as well as a Stirng formatter. The javac compiler  now uses the the StringBuilder instead of String Buffer. Since StringBuilder is synchronized there is a performance increase which has necessitated the wahat String constructor works. Comparable interface - The comparable interface works with Collections, making it easier to reuse. Try with resources - Closeable and AutoCloseable Annotations - While support for Annotations is provided it will only be a compile time support. SuppressWarnings, Deprecated, Override NIO - There is a subset of NIO Buffer that have been in use on the of the graphics packages and needs to be pulled in and also support for NIO File IO subset. Platform extensibility via Service Providers (ServiceLoader) - ServiceLoader interface dos late bindings of interface to existing implementations. It helpe to package an interface and behavior of the implementation at a later point in time.Provider classes must have a zero-argument constructor so that they can be instantiated during loading. They are located and instantiated on demand and are identified via a provider-configuration file in the METAINF/services resource directory. This is a mechansim from Java SE. import com.XYZ.ServiceA; ServiceLoader<ServiceA> sl1= new ServiceLoader(ServiceA.class); Resources: META-INF/services/com.XYZ.ServiceA: ServiceAProvider1 ServiceAProvider2 ServiceAProvider3 META-INF/services/ServiceB: ServiceBProvider1 ServiceBProvider2 From JSR - I would rather use this list I think The Generic Connection Framework (GCF) was previously specified in a number of different JSRs including CLDC, MIDP, CDC 1.2, and JSR 197. JSR 360 represents a rare opportunity to consolidated and reintegrate parts that were duplicated in other specifications into a single specification, upgrade the APIs as well provide new functionality. The proposal is to specify a combined GCF specification that can be used with Java ME or Java SE and be backwards compatible with previous implementations. Because of size limitations as well as the complexity of the some features like InvokeDynamic and Unicode 6 will not be included. Additionally, any language or library changes in JDK 8 will be not be included. On the upside, with all the changes being made, backwards compatibility will still be maintained. JSR 360 is a major step forward for Java ME in terms of platform modernization, language alignment, and embedded support. If you're interested in following the progress of this JSR see the JSR's java.net project for details of the email lists, discussions groups.

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• How do you cope with change in open source frameworks that you use for your projects?

  - by Amy

  It may be a personal quirk of mine, but I like keeping code in living projects up to date - including the libraries/frameworks that they use. Part of it is that I believe a web app is more secure if it is fully patched and up to date. Part of it is just a touch of obsessive compulsiveness on my part. Over the past seven months, we have done a major rewrite of our software. We dropped the Xaraya framework, which was slow and essentially dead as a product, and converted to Cake PHP. (We chose Cake because it gave us the chance to do a very rapid rewrite of our software, and enough of a performance boost over Xaraya to make it worth our while.) We implemented unit testing with SimpleTest, and followed all the file and database naming conventions, etc. Cake is now being updated to 2.0. And, there doesn't seem to be a viable migration path for an upgrade. The naming conventions for files have radically changed, and they dropped SimpleTest in favor of PHPUnit. This is pretty much going to force us to stay on the 1.3 branch because, unless there is some sort of conversion tool, it's not going to be possible to update Cake and then gradually improve our legacy code to reap the benefits of the new Cake framework. So, as usual, we are going to end up with an old framework in our Subversion repository and just patch it ourselves as needed. And this is what gets me every time. So many open source products don't make it easy enough to keep projects based on them up to date. When the devs start playing with a new shiny toy, a few critical patches will be done to older branches, but most of their focus is going to be on the new code base. How do you deal with radical changes in the open source projects that you use? And, if you are developing an open source product, do you keep upgrade paths in mind when you develop new versions?

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• Calculating collision force with AfterCollision/NormalImpulse is unreliable when IgnoreCCD = false?

  - by Michael

  I'm using Farseer Physics Engine 3.3.1 in a very simple XNA 4 test game. (Note: I'm also tagging this Box2D, because Farseer is a direct port of Box2D and I will happily accept Box2D answers that solve this problem.) In this game, I'm creating two bodies. The first body is created using BodyFactory.CreateCircle and BodyType.Dynamic. This body can be moved around using the keyboard (which sets Body.LinearVelocity). The second body is created using BodyFactory.CreateRectangle and BodyType.Static. This body is static and never moves. Then I'm using this code to calculate the force of collision when the two bodies collide: staticBody.FixtureList[0].AfterCollision += new AfterCollisionEventHandler(AfterCollision); protected void AfterCollision(Fixture fixtureA, Fixture fixtureB, Contact contact) { float maxImpulse = 0f; for (int i = 0; i < contact.Manifold.PointCount; i++) maxImpulse = Math.Max(maxImpulse, contact.Manifold.Points[i].NormalImpulse); // maxImpulse should contain the force of the collision } This code works great if both of these bodies are set to IgnoreCCD=true. I can calculate the force of collision between them 100% reliably. Perfect. But here's the problem: If I set the bodies to IgnoreCCD=false, that code becomes wildly unpredictable. AfterCollision is called reliably, but for some reason the NormalImpulse is 0 about 75% of the time, so only about one in four collisions is registered. Worse still, the NormalImpulse seems to be zero for completely random reasons. The dynamic body can collide with the static body 10 times in a row in virtually exactly the same way, and only 2 or 3 of the hits will register with a NormalImpulse greater than zero. Setting IgnoreCCD=true on both bodies instantly solves the problem, but then I lose continuous physics detection. Why is this happening and how can I fix it? Here's a link to a simple XNA 4 solution that demonstrates this problem in action: http://www.mediafire.com/?a1w242q9sna54j4

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• Using SPServices &amp; jQuery to Find My Stuff from Multi-Select Person/Group Field

  - by Mark Rackley

  Okay… quick blog post for all you SPServices fans out there. I needed to quickly write a script that would return all the tasks currently assigned to me.  I also wanted it to return any task that was assigned to a group I belong to. This can actually be done with a CAML query, so no big deal, right?  The rub is that the “assigned to” field is a multi-select person or group field. As far as I know (and I actually know so little) you cannot just write a CAML query to return this information. If you can, please leave a comment below and disregard the rest of this blog post… So… what’s a hacker to do? As always, I break things down to their most simple components (I really love the KISS principle and would get it tattooed on my back if people wouldn’t think it meant “Knights In Satan’s Service”. You really gotta be an old far to get that reference).  Here’s what we’re going to do: Get currently logged in user’s name as it is stored in a person field Find all the SharePoint groups the current user belongs to Retrieve a set of assigned tasks from the task list and then find those that are assigned to current  user or group current user belongs to Nothing too hairy… So let’s get started Some Caveats before I continue There are some obvious performance implications with this solution as I make a total of four SPServices calls and there’s a lot of looping going on. Also, the CAML query in this blog has NOT been optimized. If you move forward with this code, tweak it so that it returns a further subset of data or you will see horrible performance if you have a few hundred entries in your task list. Add a date range to the CAML or something. Find some way to limit the results as much as possible. Lastly, if you DO have a better solution, I would like you to share. Iron sharpens iron and all…   Alright, let’s really get started. Get currently logged in user’s name as it is stored in a person field First thing we need to do is understand how a person group looks when you look at the XML returned from a SharePoint Web Service call. It turns out it’s stored like any other multi select item in SharePoint which is <id>;#<value> and when you assign a person to that field the <value> equals the person’s name “Mark Rackley” in my case. This is for Windows Authentication, I would expect this to be different in FBA, but I’m not using FBA. If you want to know what it looks like with FBA you can use the code in this blog and strategically place an alert to see the value.  Anyway… I need to find the name of the user who is currently logged in as it is stored in the person field. This turns out to be one SPServices call: var userName = $().SPServices.SPGetCurrentUser({                     fieldName: "Title",                     debug: false                     }); As you can see, the “Title” field has the information we need. I suspect (although again, I haven’t tried) that the Title field also contains the user’s name as we need it if I was using FBA. Okay… last thing we need to do is store our users name in an array for processing later: myGroups = new Array(); myGroups.push(userName); Find all the SharePoint groups the current user belongs to Now for the groups. How are groups returned in that XML stream?  Same as the person <ID>;#<Group Name>, and if it’s a mutli select it’s all returned in one big long string “<ID>;#<Group Name>;#<ID>;#<Group Name>;#<ID>;#<Group Name>;#<ID>;#<Group Name>;#<ID>;#<Group Name>”.  So, how do we find all the groups the current user belongs to? This is also a simple SPServices call. Using the “GetGroupCollectionFromUser” operation we can find all the groups a user belongs to. So, let’s execute this method and store all our groups. $().SPServices({       operation: "GetGroupCollectionFromUser",       userLoginName: $().SPServices.SPGetCurrentUser(),       async: false,       completefunc: function(xData, Status) {          $(xData.responseXML).find("[nodeName=Group]").each(function() {                 myGroups.push($(this).attr("Name"));          });         }     }); So, all we did in the above code was execute the “GetGroupCollectionFromUser” operation and look for the each “Group” node (row) and store the name for each group in our array that we put the user’s name in previously (myGroups). Now we have an array that contains the current user’s name as it will appear in the person field XML and  all the groups the current user belongs to. The Rest Now comes the easy part for all of you familiar with SPServices. We are going to retrieve our tasks from the Task list using “GetListItems” and look at each entry to see if it belongs to this person. If it does belong to this person we are going to store it for later processing. That code looks something like this: // get list of assigned tasks that aren't closed... *modify the CAML to perform better!*             $().SPServices({                   operation: "GetListItems",                   async: false,                   listName: "Tasks",                   CAMLViewFields: "<ViewFields>" +                             "<FieldRef Name='AssignedTo' />" +                             "<FieldRef Name='Title' />" +                             "<FieldRef Name='StartDate' />" +                             "<FieldRef Name='EndDate' />" +                             "<FieldRef Name='Status' />" +                             "</ViewFields>",                   CAMLQuery: "<Query><Where><And><IsNotNull><FieldRef Name='AssignedTo'/></IsNotNull><Neq><FieldRef Name='Status'/><Value Type='Text'>Completed</Value></Neq></And></Where></Query>",                     completefunc: function (xData, Status) {                         var aDataSet = new Array();                        //loop through each returned Task                         $(xData.responseXML).find("[nodeName=z:row]").each(function() {                             //store the multi-select string of who task is assigned to                             var assignedToString = $(this).attr("ows_AssignedTo");                             found = false;                            //loop through the persons name and all the groups they belong to                             for(var i=0; i<myGroups.length; i++) {                                 //if the person's name or group exists in the assigned To string                                 //then the task is assigned to them                                 if (assignedToString.indexOf(myGroups[i]) >= 0){                                     found = true;                                     break;                                 }                             }                             //if the Task belongs to this person then store or display it                             //(I'm storing it in an array)                             if (found){                                 var thisName = $(this).attr("ows_Title");                                 var thisStartDate = $(this).attr("ows_StartDate");                                 var thisEndDate = $(this).attr("ows_EndDate");                                 var thisStatus = $(this).attr("ows_Status");                                                                  var aDataRow=new Array(                                     thisName,                                     thisStartDate,                                     thisEndDate,                                     thisStatus);                                 aDataSet.push(aDataRow);                             }                          });                          SomeFunctionToDisplayData(aDataSet);                     }                 }); Some notes on why I did certain things and additional caveats. You will notice in my code that I’m doing an AssignedToString.indexOf(GroupName) to see if the task belongs to the person. This could possibly return bad results if you have SharePoint Group names that are named in such a way that the “IndexOf” returns a false positive.  For example if you have a Group called “My Users” and a group called “My Users – SuperUsers” then if a user belonged to “My Users” it would return a false positive on executing “My Users – SuperUsers”.IndexOf(“My Users”). Make sense? Just be aware of this when naming groups, we don’t have this problem. This is where also some fine-tuning can probably be done by those smarter than me. This is a pretty inefficient method to determine if a task belongs to a user, I mean what if a user belongs to 20 groups? That’s a LOT of looping.  See all the opportunities I give you guys to do something fun?? Also, why am I storing my values in an array instead of just writing them out to a Div? Well.. I want to pass my data to a jQuery library to format it all nice and pretty and an Array is a great way to do that. When all is said and done and we put all the code together it looks like:   $(document).ready(function() {         var userName = $().SPServices.SPGetCurrentUser({                     fieldName: "Title",                     debug: false                     });         myGroups = new Array();     myGroups.push(userName );       $().SPServices({       operation: "GetGroupCollectionFromUser",       userLoginName: $().SPServices.SPGetCurrentUser(),       async: false,       completefunc: function(xData, Status) {          $(xData.responseXML).find("[nodeName=Group]").each(function() {                 myGroups.push($(this).attr("Name"));          });                      // get list of assigned tasks that aren't closed... *modify this CAML to perform better!*             $().SPServices({                   operation: "GetListItems",                   async: false,                   listName: "Tasks",                   CAMLViewFields: "<ViewFields>" +                             "<FieldRef Name='AssignedTo' />" +                             "<FieldRef Name='Title' />" +                             "<FieldRef Name='StartDate' />" +                             "<FieldRef Name='EndDate' />" +                             "<FieldRef Name='Status' />" +                             "</ViewFields>",                   CAMLQuery: "<Query><Where><And><IsNotNull><FieldRef Name='AssignedTo'/></IsNotNull><Neq><FieldRef Name='Status'/><Value Type='Text'>Completed</Value></Neq></And></Where></Query>",                     completefunc: function (xData, Status) {                         var aDataSet = new Array();                         //loop through each returned Task                         $(xData.responseXML).find("[nodeName=z:row]").each(function() {                             //store the multi-select string of who task is assigned to                             var assignedToString = $(this).attr("ows_AssignedTo");                             found = false;                            //loop through the persons name and all the groups they belong to                             for(var i=0; i<myGroups.length; i++) {                                 //if the person's name or group exists in the assigned To string                                 //then the task is assigned to them                                 if (assignedToString.indexOf(myGroups[i]) >= 0){                                     found = true;                                     break;                                 }                             }                            //if the Task belongs to this person then store or display it                             //(I'm storing it in an array)                             if (found){                                 var thisName = $(this).attr("ows_Title");                                 var thisStartDate = $(this).attr("ows_StartDate");                                 var thisEndDate = $(this).attr("ows_EndDate");                                 var thisStatus = $(this).attr("ows_Status");                                                                  var aDataRow=new Array(                                     thisName,                                     thisStartDate,                                     thisEndDate,                                     thisStatus);                                 aDataSet.push(aDataRow);                             }                          });                          SomeFunctionToDisplayData(aDataSet);                     }                 });       }    });  }); Final Thoughts So, there you have it. Take it and run with it. Make it something cool (and tell me how you did it). Another possible way to improve performance in this scenario is to use a DVWP to display the tasks and use jQuery and the “myGroups” array from this blog post to hide all those rows that don’t belong to the current user. I haven’t tried it, but it does move some of the processing off to the server (generating the view) so it may perform better.  As always, thanks for stopping by… hope you have a Merry Christmas…

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• multiple definition of inline function

  - by K71993

  Hi, I have gone through some posts related to this topic but was not able to sort out my doubt completly. This might be a very navie question. Code Description I have a header file "inline.h" and two translation unit "main.cpp" and "tran.cpp". Details of code are as below inline.h file details #ifndef __HEADER__ #include <stdio.h> extern inline int func1(void) { return 5; } static inline int func2(void) { return 6; } inline int func3(void) { return 7; } #endif main.c file details are below #define <stdio.h> #include <inline.h> int main(int argc, char *argv[]) { printf("%d\n",func1()); printf("%d\n",func2()); printf("%d\n",func3()); return 0; } tran.cpp file details (Not that the functions are not inline here) #include <stdio.h> int func1(void) { return 500; } int func2(void) { return 600; } int func3(void) { return 700; } Question The above code does not compile in gcc compiler whereas compiles in g++ (Assuming you make changes related to gcc in code like changing the code to .c not using any C++ header files... etc). The error displayed is "duplicate definition of inline function - func3". Can you clarify why this difference is present across compile? When you run the program (g++ compiled) by creating two seperate compilation unit (main.o and tran.o and create an executable a.out), the output obtained is 500 6 700 Why does the compiler pick up the definition of the function which is not inline. Actually since #include is used to "add" the inline definiton I had expected 5,6,7 as the output. My understanding was during compilation since the inline definition is found, the function call would be "replaced" by inline function definition. Can you please tell me in detailed steps the process of compilation and linking which would lead us to 500,6,700 output. I can only understand the output 6. Thanks in advance for valuable input.

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• Java - Error Message Help

  - by Brian

  In the Code, mem is a of Class Memory and getMDR and getMAR ruturn ints. When I try to compile the code I get the following errors.....how can I fix this? Computer.java:25: write(int,int) in Memory cannot be applied to (int) Input.getInt(mem.write(cpu.getMDR())); ^ Computer.java:28: write(int,int) in Memory cannot be applied to (int) mem.write(cpu.getMAR()); Here is the code for Computer: class Computer{ private Cpu cpu; private Input in; private OutPut out; private Memory mem; public Computer() { Memory mem = new Memory(100); Input in = new Input(); OutPut out = new OutPut(); Cpu cpu = new Cpu(); System.out.println(in.getInt()); } public void run() { cpu.reset(); cpu.setMDR(mem.read(cpu.getMAR())); cpu.fetch2(); while (!cpu.stop()) { cpu.decode(); if (cpu.OutFlag()) OutPut.display(mem.read(cpu.getMAR())); if (cpu.InFlag()) Input.getInt(mem.write(cpu.getMDR())); if (cpu.StoreFlag()) { mem.write(cpu.getMAR()); cpu.getMDR(); } else { cpu.setMDR(mem.read(cpu.getMAR())); cpu.execute(); cpu.fetch(); cpu.setMDR(mem.read(cpu.getMAR())); cpu.fetch2(); } } } Here is the code for Memory: class Memory{ private MemEl[] memArray; private int size; public Memory(int s) {size = s; memArray = new MemEl[s]; for(int i = 0; i < s; i++) memArray[i] = new MemEl(); } public void write (int loc, int val) {if (loc >=0 && loc < size) memArray[loc].write(val); else System.out.println("Index Not in Domain"); } public int read (int loc) {return memArray[loc].read(); } public void dump() { for(int i = 0; i < size; i++) if(i%1 == 0) System.out.println(memArray[i].read()); else System.out.print(memArray[i].read()); } } Here is the code for getMAR and getMDR: public int getMAR() { return ir.getOpcode(); } public int getMDR() { return mdr.read(); }

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• How to get initial API right using TDD?

  - by Vytautas Mackonis

  This might be a rather silly question as I am at my first attempts at TDD. I loved the sense of confidence it brings and generally better structure of my code but when I started to apply it on something bigger than one-class toy examples, I ran into difficulties. Suppose, you are writing a library of sorts. You know what it has to do, you know a general way of how it is supposed to be implemented (architecture wise), but you keep "discovering" that you need to make changes to your public API as you code. Perhaps you need to transform this private method into strategy pattern (and now need to pass a mocked strategy in your tests), perhaps you misplaced a responsibility here and there and split an existing class. When you are improving upon existing code, TDD seems a really good fit, but when you are writing everything from scratch, the API you write tests for is a bit "blurry" unless you do a big design up front. What do you do when you already have 30 tests on the method that had its signature (and for that part, behavior) changed? That is a lot of tests to change once they add up.

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• New partnership allows auto-transposition of client/server application to Windows Azure

  - by Webgui

  The economics of IT is changing rapidly, and organizations are searching to widen and secure availability of their systems and at the same time lower costs which is exactly what the cloud meant to do. Running your systems on Microsoft’s Windows Azure cloud for example would improve and secure the availability, accessibility and scalability (both up and down) of your systems and support the new IT economics. However, in order to take advantage of the cloud's promise of lower cost of ownership, the applications must be built or adjusted to work on that platform and in most cases this is not a simple task.  Even existing web applications cannot always be transferred to Azure without some changes, and for client/server applications, the task is way more challenging even to the point where it seems impossible. The reason is the gaps between the client/server desktop technology and the cloud's. For that reason, most of the known methodologies to migrate existing client/server applications actually involve rewrite of the desktop systems for the cloud. A unique approach is introduced by Visual WebGui which creates a virtualization layer atop ASP.Net web server, it moves the transformed or generated .Net code to that layer, and then using a patent pending protocol it renders a user interface within a plain browser. The end result is pure .NET code that is a base code for a pure rich web application and now due to a collaboration with Microsoft Windows Azure Visual WebGui provides the shortest path from client/server to the Azure cloud by being able to handle close to 95% of the transformation to the cloud platform in an automatic way. Application Migration to Azure without migraines More information about the Instant CloudMove Azure solution here.

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• How to hire support people?

  - by Martin

  I manage a tech support team at a mid-sized software company. We are the last line of support, so issues that we can't fix need to be escalated to the development team. When I joined the company, our team wasn't capable of much beyond using a specific set of troubleshooting steps to solve known issues and escalating anything else to the developers. It's always been a goal of mine for our team to shoulder as much of the support burden as possible without ever bothering a developer. Over the past few years, I, along with several new hires I've made, have made pretty good progress in that direction. We've coded our own troubleshooting tools which now ship with several of our products. When users have never-before-seen issues, we analyze stack traces and troubleshoot down to the code level, and if we need to submit a bug, half the time we've already identified in the code where in the code the bug is and offered a patch to fix it. Here's the problem I've always had: finding support people capable of the work I've described above is really difficult. I've hired 3 people in the past 3 years, and I've probably looked at several thousand resumes and conducted several hundred phone screens to do so. I know it's pretty well accepted that hiring good people is tough in the tech industry, but it seems that support is especially difficult -- there are clearly thousands of people walking around calling themselves support analysts, but 99%+ of them seemingly aren't capable of anything beyond reading a script. I'm curious if anyone has experience recruiting the sort of folks I'm talking about, and if you have any suggestions to share. We've tried all sorts of things -- different job titles/descriptions, using headhunters, etc. And while we've managed to hire a few good folks, it's basically taken us a year to find an appropriate candidate for each opening we've had, and I can't help but wonder if there's something we could be doing differently.

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• Using XSLT for messaging instead of marshalling/unmarshalling Java message objects

  - by Joost van Stuijvenberg

  So far I have been using either handmade or generated (e.g. JAXB) Java objects as 'carriers' for messages in message processing software such as protocol converters. This often leads to tedious programming, such as copying/converting data from one system's message object to an instance of another's system message object. And it sure brings in lots of Java code with getters and setters for each message attribute, validation code, etc. I was wondering whether it would be a good idea to convert one system's XML message into another system's format - or even convert requests into responses from the same system - using XSLT. This would mean I would no longer have to unmarshall XML streams to Java objects, copy/convert data using Java and marshall the resulting message object to another XML stream. Since each message may actually have a purpose I would 'link' the message (and the payload it contains in its properties or XML elements/attributes) to EXSLT functions. This would change my design approach from an imperative to a declarative style. Has anyone done this before and, if so, what are your experiences? Does the reduced amount of Java 'boiler plate' code weigh up to the increased complexity of (E)XSLT?

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• Simple issue tracker for 1-2 developers

  - by devoured elysium

  (I'm not sure whether this pertains to the realm of programmers@se or so@se) I'm currently working mostly alone on a project (in Java). I'm mostly alone as I have an advisor that gives me high level instructions on what to do, and will seldom make any code contribution. She will code in a couple of acceptance tests from time to time, though. I've never used an Issue Tracker before, and was thinking about starting to use one now, as I'd like to have a place where I can log possible bugs I find and keep track of them in a centralized manner. Would it be possible to integrate the issue tracker with Eclipse, better yet. So here are the constraints: It's NOT a open-source project. Our code is not to be shared with anyone! we are and will be using Subversion; we have our own Subversion server and we will keep using this same Subversion server; it must be free; it must allow at least 2 users. What is your advice on what to pick? I'm looking for the simplest solution available!

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• Trying to use OpenGL in Java on Netbeans but getting an error. Please help [migrated]

  - by Steven Rogers

  I am on a Mac running Netbeans 6.9. I downloaded and installed LWJGL using this tutorial down to the letter: http://lwjgl.org/wiki/index.php?title=Setting_Up_LWJGL_with_NetBeans I finished the installation and copied sample code to see if my system is working. I got a bug, and was not sure if it was because of faulty code or i was doing something wrong. So i shortened down the code to this little simple bit: package javaopengl; import org.lwjgl.Sys; import org.lwjgl.opengl.Display; //Testing public class Main { public static void main(String[] args) { boolean fullscreen = (args.length == 1 && args[0].equals("-fullscreen")); try { Display.create(); Display.destroy(); } catch (Exception e) { e.printStackTrace(System.err); } System.exit(0); } } But i still get the same error, this is the error that i get: run: Exception in thread "main" java.lang.NoClassDefFoundError: = Caused by: java.lang.ClassNotFoundException: = at java.net.URLClassLoader$1.run(URLClassLoader.java:202) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) Java Result: 1 BUILD SUCCESSFUL (total time: 0 seconds) I am not sure what exactly is going on, Would you please tell me what is going on and how to fix it? It would be greatly appreciated, and thank you. Note: When i am looking at the text in the development environment, it does not show those red lines indicating there are any errors.

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• OOP for unit testing : The good, the bad and the ugly

  - by Jeff

  I have recently read Miško Hevery's pdf guide to writing testable code in which its stated that you should limit your classes instanciations in your constructors. I understand that its what you should do because it allow you to easily mock you objects that are send as parameters to your class. But when it comes to writing actual code, i often end up with things like that (exemple is in PHP using Zend Framework but I think it's self explanatory) : class Some_class { private $_data; private $_options; private $_locale; public function __construct($data, $options = null) { $this->_data = $data; if ($options != null) { $this->_options = $options; } $this->_init(); } private function _init() { if(isset($this->_options['locale'])) { $locale = $this->_options['locale']; if ($locale instanceof Zend_Locale) { $this->_locale = $locale; } elseif (Zend_Locale::isLocale($locale)) { $this->_locale = new Zend_Locale($locale); } else { $this->_locale = new Zend_Locale(); } } } } Acording to my understanding of Miško Hevery's guide, i shouldn't instanciate the Zend_Local in my class but push it through the constructor (Which can be done through the options array in my example). I am wondering what would be the best practice to get the most flexibility for unittesing this code and aswell, if I want to move away from Zend Framework. Thanks in advance

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• Have you used nDepend?

  - by Nick Harrison

  Have you Used NDepend? I have often wanted to use it, but never spent the money on it.   I have developed many tools that try to do pieces of what NDepend does, but never with as much success as they reach. Put simply, it is a tool that will allow you to udnerstand and monitor the architecture of your software, and it does it in some pretty amazing ways. One of the most impressive features is something that they call Code Query Language.   It allows you to write queries very similar to SQL to track the performance of various software metrics and use this to identify areas that are out of compliance with your standards and architecture. For instance, once you have analyzed your project, you can write queries such as : SELECT METHODS WHERE IsPublic AND CouldBePrivate  You can also set up such queries to provide warnings if there are records returned.    You can incorporae this into your daily build and compare build against build. There are over 82 metrics included to allow you to view your code in a variety of angles. I have often advocated for a "Code Inventory" database to track the state of software and the ROI on software investments.    This tool alone will take you about 90% of the way there. If you are not using it yet,  I strongly recommend that you do!

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• C++ Unlocking a std::mutex before calling std::unique_lock wait

  - by Sant Kadog

  I have a multithreaded application (using std::thread) with a manager (class Tree) that executes some piece of code on different subtrees (embedded struct SubTree) in parallel. The basic idea is that each instance of SubTree has a deque that store objects. If the deque is empty, the thread waits until a new element is inserted in the deque or the termination criteria is reached. One subtree can generate objects and push them in the deque of another subtree. For convenience, all my std::mutex, std::locks and std::variable_condition are stored in a struct called "locks". The class Tree creates some threads that run the following method (first attempt) : void Tree::launch(SubTree & st, Locks & locks ) { /* some code */ std::lock_guard<std::mutex> deque_lock(locks.deque_mutex_[st.id_]) ; // lock the access to the deque of subtree st if (st.deque_.empty()) // check that the deque is still empty { // some threads are still running, wait for them to terminate std::unique_lock<std::mutex> wait_lock(locks.restart_mutex_[st.id_]) ; locks.restart_condition_[st.id_].wait(wait_lock) ; } /* some code */ } The problem is that "deque_lock" is still locked while the thread is waiting. Hence no object can be added in the deque of the current thread by a concurrent one. So I turned the lock_guard into a unique_lock and managed the lock/unlock manually : void launch(SubTree & st, Locks & locks ) { /* some code */ std::unique_lock<std::mutex> deque_lock(locks.deque_mutex_[st.id_]) ; // lock the access to the deque of subtree st if (st.deque_.empty()) // check that the deque is still empty { deque_lock.unlock() ; // unlock the access to the deque to enable the other threads to add objects // DATA RACE : nothing must happen to the unprotected deque here !!!!!! // some threads are still running, wait for them to terminate std::unique_lock<std::mutex> wait_lock(locks.restart_mutex_[st.id_]) ; locks.restart_condition_[st.id_].wait(wait_lock) ; } /* some code */ } The problem now, is that there is a data race, and I would like to make sure that the "wait" instruction is performed directly after the "deque_lock.unlock()" one. Would anyone know a way to create such a critical instruction sequence with the standard library ? Thanks in advance.

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• Just started a job with Scrum. Something seems to be missing. I am new to Scrum

  - by punkouter

  The code is a complete mess of a combination of classic ASP/ASP.NET. The scrum consist of us patching up the big mess or making additions to it. We are all too busy doing that to start a rewrite so I am wondering.. Where is the part in Scrum where the developers can have the power to say that enough is enough and demand that they are given time to start the big rewrite ? We seem in an endless loop of just patching old code with 'Stories'. So things are being run by the non-technical people who seem to have no desire to push for a rewrite because they don't understand how bad the code base has gotten.. So who is in charge of making this big rewrite change happen ? The devs? The scrum master? The current strategy is just find time and do it ourselves without the higher ups involved.. since they are mostly to blame for the current mess we are in.. <-insert rant about non-tech people telling tech people what to do here-

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• How can I install oracle-java7 from webupd8 ppa?

  - by Ahmed Zain El Dein

  I installed ppa:webupd8team/java and I get the following error Output from: sudo apt-get install oracle-java7-installer Reading package lists... Done Building dependency tree Reading state information... Done Suggested packages: binfmt-support visualvm ttf-baekmuk ttf-unfonts ttf-unfonts-core ttf-kochi-gothic ttf-sazanami-gothic ttf-kochi-mincho ttf-sazanami-mincho ttf-arphic-uming The following packages will be upgraded: oracle-java7-installer 1 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. 1 not fully installed or removed. Need to get 0 B/16.0 kB of archives. After this operation, 64.5 kB of additional disk space will be used. Could not exec dpkg! E: Sub-process /usr/bin/dpkg returned an error code (100) i did afterwords those line of code trying to resolve the issue becuase it is not existed actually in the /usr/bin/dpkg there is no dpkg mkdir /tmp/dpkg cd /tmp/dpkg wget http://archive.ubuntu.com/ubuntu/pool/main/d/dpkg/dpkg_1.15.5.6ubuntu4_i386.deb ar x dpkg*.deb data.tar.gz tar xfvz data.tar.gz ./usr/bin/dpkg sudo cp ./usr/bin/dpkg /usr/bin/ sudo apt-get update sudo apt-get install --reinstall dpkg then i get this $ sudo apt-get install --reinstall dpkg Reading package lists... Done Building dependency tree Reading state information... Done 0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 6 not upgraded. 1 not fully installed or removed. Need to get 0 B/1,814 kB of archives. After this operation, 0 B of additional disk space will be used. dpkg: warning: 'dpkg-deb' not found on PATH. dpkg: 1 expected program(s) not found on PATH. NB: root's PATH should usually contain /usr/local/sbin, /usr/sbin and /sbin. E: Sub-process /usr/bin/dpkg returned an error code (2) How can I fix this?

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• PHP: How to implement a __get-like method for local function variables

  - by Tom Frost

  I'm no stranger to __get(), and have used it to make some very convenient libraries in the past. However, I'm faced with a new challenge (PHP 5.3, abbreviated and simplified my code for this question): <?php namespace test; class View { function __construct($filename, $varArray) { $this->filename = $filename; $this->varArray = $varArray; } function display() { include($this->filename); } function __get($varName) { if (isset($this->varArray[$varName])) return $this->varArray[$varName]; return "?? $varname ??"; } } ?> Above is a very, very simplified system for loading a View. This code would call the view and display it: <?php require_once("View.php"); use test\View; $view = new View("views/myview.php", array("user" => "Tom")); $view->display(); ?> My goal for this code is to allow the view "myview.php" to contain code like this: <p> Hello <?php echo $user; ?>! Your E-mail is <?php echo $email; ?> </p> And, used with the above code, this would output "Hello Tom! Your E-mail is ?? email ??" However, this won't work. The view is being included within a class method, so when it refers to $user and $email, it's looking for local function variables -- not variables belonging to the View class. For this reason, __get never gets triggered. I could change all my view's variables to things like $this-user and $this-email, but that would be a messy and unintuitive solution. I'd love to find a way where I can reference variables directly WITHOUT having PHP throw an error when an undefined variable is used. Thoughts? Is there a clean way to do this, or am I forced to resort to hacky solutions?

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• Recording custom variables to identify individual users with Google Analytics

  - by mrtsherman

  I have been asked by our marketing department to add Google Analytics custom variable tracking to my company's website. As the website uses server side includes, modifications to the tracking tag roll out globally - maintenance is therefore a headache! So, if I add the following code (keeping in mind SSI so every page has the same code): // visitor level tracking, id = 12345 // Record a unique id for each visitor. When they return also track this id _gaq.push(['_setCustomVar', 1, 'id', '12345', 1]); // page level tracking // If the user signs up for our newsletter we set newsletter to true // Each page they subsequently visit should also mark this as true _gaq.push(['_setCustomVar', 1, 'newsletter', 'true', 1]); I don't use GA and the marketing people don't use custom variables, so we don't actually know how or if this will work. Therefore my questions are:- Do I want Page, Session or Visitor level tracking? What happens when the same code is used on every page? Can GA 'overwrite' a setting. For example, if I set newsletter to true on page X and then user navigates to page Y, will the variable also be marked there?

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• Programming graphics and sound on PC - Total newbie questions, and lots of them!

  - by Russel

  Hello, This isn't exactly specifically a programming question (or is it?) but I was wondering: How are graphics and sound processed from code and output by the PC? My guess for graphics: There is some reserved memory space somewhere that holds exactly enough room for a frame of graphics output for your monitor. IE: 800 x 600, 24 bit color mode == 800x600x3 = ~1.4MB memory space Between each refresh, the program writes video data to this space. This action is completed before the monitor refresh. Assume a simple 2D game: the graphics data is stored in machine code as many bytes representing color values. Depending on what the program(s) being run instruct the PC, the processor reads the appropriate data and writes it to the memory space. When it is time for the monitor to refresh, it reads from each memory space byte-for-byte and activates hardware depending on those values for each color element of each pixel. All of this of course happens crazy-fast, and repeats x times a second, x being the monitor's refresh rate. I've simplified my own likely-incorrect explanation by avoiding talk of double buffering, etc Here are my questions: a) How close is the above guess (the three steps)? b) How could one incorporate graphics in pure C++ code? I assume the practical thing that everyone does is use a graphics library (SDL, OpenGL, etc), but, for example, how do these libraries accomplish what they do? Would manual inclusion of graphics in pure C++ code (say, a 2D spite) involve creating a two-dimensional array of bit values (or three dimensional to include multiple RGB values per pixel)? Is this how it would be done waaay back in the day? c) Also, continuing from above, do libraries such as SDL etc that use bitmaps actual just build the bitmap/etc files into machine code of the executable and use them as though they were build in the same matter mentioned in question b above? d) In my hypothetical step 3 above, is there any registers involved? Like, could you write some byte value to some register to output a single color of one byte on the screen? Or is it purely dedicated memory space (=RAM) + hardware interaction? e) Finally, how is all of this done for sound? (I have no idea :) )

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• Does it make sense to write a build scripts in C++?

  - by Klaim

  I'm using CMake to generate my projects IDE/makefiles, but I still need to call custom "scripts" to manipulate my compiled files or even generate code. In previous projects I've been using Python and it was OK, but now I'm having serious trouble managing a lot of dependencies in two very big projects I'm working on so I want to minimize the dependencies everywhere. Someone suggested to me to use C++ to write my build scripts instead of adding a language dependency just for that. The projects themeselves already use C++ so there are several advantages that I can see: to build the whole project, only a C++ compiler and CMake would be necessary, nothing else (all the other dependencies are C or C++); C++ type safety (when using modern C++) makes everything easier to get "correct"; it's also the language I know the better so I'm more at ease with it even if I'm able to write some good Python code; potential gain in execution speed (but i don't think it will really be perceptible); However, I think there might be some drawbacks and I'm not sure of the real impact as I didn't try yet: might be longer to write the code (that said I'm not sure because I'm efficient enough in C++ to write something that work quickly, so maybe for this system it wouldn't be so long to write) (compilation time shouldn't be a problem for this case); I must assume that all the text files I'll read as input are in UTF-8, I'm not sure it can be easilly checked at runtime in C++ and the language will not check it for you; libraries in C++ are harder to manage than in scripting languages; I lack experience and forsight so maybe I'm missing advantages and drawbacks. So the question is: does it make sense to use C++ for this? do you have experiences to report and do you see advantages and disadvantages that might be important?

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• Matrix Multiplication with C++ AMP

  - by Daniel Moth

  As part of our API tour of C++ AMP, we looked recently at parallel_for_each. I ended that post by saying we would revisit parallel_for_each after introducing array and array_view. Now is the time, so this is part 2 of parallel_for_each, and also a post that brings together everything we've seen until now. The code for serial and accelerated Consider a naïve (or brute force) serial implementation of matrix multiplication  0: void MatrixMultiplySerial(std::vector<float>& vC, const std::vector<float>& vA, const std::vector<float>& vB, int M, int N, int W) 1: { 2: for (int row = 0; row < M; row++) 3: { 4: for (int col = 0; col < N; col++) 5: { 6: float sum = 0.0f; 7: for(int i = 0; i < W; i++) 8: sum += vA[row * W + i] * vB[i * N + col]; 9: vC[row * N + col] = sum; 10: } 11: } 12: } We notice that each loop iteration is independent from each other and so can be parallelized. If in addition we have really large amounts of data, then this is a good candidate to offload to an accelerator. First, I'll just show you an example of what that code may look like with C++ AMP, and then we'll analyze it. It is assumed that you included at the top of your file #include <amp.h> 13: void MatrixMultiplySimple(std::vector<float>& vC, const std::vector<float>& vA, const std::vector<float>& vB, int M, int N, int W) 14: { 15: concurrency::array_view<const float,2> a(M, W, vA); 16: concurrency::array_view<const float,2> b(W, N, vB); 17: concurrency::array_view<concurrency::writeonly<float>,2> c(M, N, vC); 18: concurrency::parallel_for_each(c.grid, 19: [=](concurrency::index<2> idx) restrict(direct3d) { 20: int row = idx[0]; int col = idx[1]; 21: float sum = 0.0f; 22: for(int i = 0; i < W; i++) 23: sum += a(row, i) * b(i, col); 24: c[idx] = sum; 25: }); 26: } First a visual comparison, just for fun: The beginning and end is the same, i.e. lines 0,1,12 are identical to lines 13,14,26. The double nested loop (lines 2,3,4,5 and 10,11) has been transformed into a parallel_for_each call (18,19,20 and 25). The core algorithm (lines 6,7,8,9) is essentially the same (lines 21,22,23,24). We have extra lines in the C++ AMP version (15,16,17). Now let's dig in deeper. Using array_view and extent When we decided to convert this function to run on an accelerator, we knew we couldn't use the std::vector objects in the restrict(direct3d) function. So we had a choice of copying the data to the the concurrency::array<T,N> object, or wrapping the vector container (and hence its data) with a concurrency::array_view<T,N> object from amp.h – here we used the latter (lines 15,16,17). Now we can access the same data through the array_view objects (a and b) instead of the vector objects (vA and vB), and the added benefit is that we can capture the array_view objects in the lambda (lines 19-25) that we pass to the parallel_for_each call (line 18) and the data will get copied on demand for us to the accelerator. Note that line 15 (and ditto for 16 and 17) could have been written as two lines instead of one: extent<2> e(M, W); array_view<const float, 2> a(e, vA); In other words, we could have explicitly created the extent object instead of letting the array_view create it for us under the covers through the constructor overload we chose. The benefit of the extent object in this instance is that we can express that the data is indeed two dimensional, i.e a matrix. When we were using a vector object we could not do that, and instead we had to track via additional unrelated variables the dimensions of the matrix (i.e. with the integers M and W) – aren't you loving C++ AMP already? Note that the const before the float when creating a and b, will result in the underling data only being copied to the accelerator and not be copied back – a nice optimization. A similar thing is happening on line 17 when creating array_view c, where we have indicated that we do not need to copy the data to the accelerator, only copy it back. The kernel dispatch On line 18 we make the call to the C++ AMP entry point (parallel_for_each) to invoke our parallel loop or, as some may say, dispatch our kernel. The first argument we need to pass describes how many threads we want for this computation. For this algorithm we decided that we want exactly the same number of threads as the number of elements in the output matrix, i.e. in array_view c which will eventually update the vector vC. So each thread will compute exactly one result. Since the elements in c are organized in a 2-dimensional manner we can organize our threads in a two-dimensional manner too. We don't have to think too much about how to create the first argument (a grid) since the array_view object helpfully exposes that as a property. Note that instead of c.grid we could have written grid<2>(c.extent) or grid<2>(extent<2>(M, N)) – the result is the same in that we have specified M*N threads to execute our lambda. The second argument is a restrict(direct3d) lambda that accepts an index object. Since we elected to use a two-dimensional extent as the first argument of parallel_for_each, the index will also be two-dimensional and as covered in the previous posts it represents the thread ID, which in our case maps perfectly to the index of each element in the resulting array_view. The kernel itself The lambda body (lines 20-24), or as some may say, the kernel, is the code that will actually execute on the accelerator. It will be called by M*N threads and we can use those threads to index into the two input array_views (a,b) and write results into the output array_view ( c ). The four lines (21-24) are essentially identical to the four lines of the serial algorithm (6-9). The only difference is how we index into a,b,c versus how we index into vA,vB,vC. The code we wrote with C++ AMP is much nicer in its indexing, because the dimensionality is a first class concept, so you don't have to do funny arithmetic calculating the index of where the next row starts, which you have to do when working with vectors directly (since they store all the data in a flat manner). I skipped over describing line 20. Note that we didn't really need to read the two components of the index into temporary local variables. This mostly reflects my personal choice, in some algorithms to break down the index into local variables with names that make sense for the algorithm, i.e. in this case row and col. In other cases it may i,j,k or x,y,z, or M,N or whatever. Also note that we could have written line 24 as: c(idx[0], idx[1])=sum  or  c(row, col)=sum instead of the simpler c[idx]=sum Targeting a specific accelerator Imagine that we had more than one hardware accelerator on a system and we wanted to pick a specific one to execute this parallel loop on. So there would be some code like this anywhere before line 18: vector<accelerator> accs = MyFunctionThatChoosesSuitableAccelerators(); accelerator acc = accs[0]; …and then we would modify line 18 so we would be calling another overload of parallel_for_each that accepts an accelerator_view as the first argument, so it would become: concurrency::parallel_for_each(acc.default_view, c.grid, ...and the rest of your code remains the same… how simple is that? Comments about this post by Daniel Moth welcome at the original blog.

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