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• career in Mobile sw/Application Development [closed]

  - by pramod

  i m planning to do a course on Wireless & mobile computing.The syllabus are given below.Please check & let me know whether its worth to do.How is the job prospects after that.I m a fresher & from electronic Engg.The modules are- *Wireless and Mobile Computing (WiMC) – Modules* C, C++ Programming and Data Structures 100 Hours C Revision C, C++ programming tools on linux(Vi editor, gdb etc.) OOP concepts Programming constructs Functions Access Specifiers Classes and Objects Overloading Inheritance Polymorphism Templates Data Structures in C++ Arrays, stacks, Queues, Linked Lists( Singly, Doubly, Circular) Trees, Threaded trees, AVL Trees Graphs, Sorting (bubble, Quick, Heap , Merge) System Development Methodology 18 Hours Software life cycle and various life cycle models Project Management Software: A Process Various Phases in s/w Development Risk Analysis and Management Software Quality Assurance Introduction to Coding Standards Software Project Management Testing Strategies and Tactics Project Management and Introduction to Risk Management Java Programming 110 Hours Data Types, Operators and Language Constructs Classes and Objects, Inner Classes and Inheritance Inheritance Interface and Package Exceptions Threads Java.lang Java.util Java.awt Java.io Java.applet Java.swing XML, XSL, DTD Java n/w programming Introduction to servlet Mobile and Wireless Technologies 30 Hours Basics of Wireless Technologies Cellular Communication: Single cell systems, multi-cell systems, frequency reuse, analog cellular systems, digital cellular systems GSM standard: Mobile Station, BTS, BSC, MSC, SMS sever, call processing and protocols CDMA standard: spread spectrum technologies, 2.5G and 3G Systems: HSCSD, GPRS, W-CDMA/UMTS,3GPP and international roaming, Multimedia services CDMA based cellular mobile communication systems Wireless Personal Area Networks: Bluetooth, IEEE 802.11a/b/g standards Mobile Handset Device Interfacing: Data Cables, IrDA, Bluetooth, Touch- Screen Interfacing Wireless Security, Telemetry Java Wireless Programming and Applications Development(J2ME) 100 Hours J2ME Architecture The CLDC and the KVM Tools and Development Process Classification of CLDC Target Devices CLDC Collections API CLDC Streams Model MIDlets MIDlet Lifecycle MIDP Programming MIDP Event Architecture High-Level Event Handling Low-Level Event Handling The CLDC Streams Model The CLDC Networking Package The MIDP Implementation Introduction to WAP, WML Script and XHTML Introduction to Multimedia Messaging Services (MMS) Symbian Programming 60 Hours Symbian OS basics Symbian OS services Symbian OS organization GUI approaches ROM building Debugging Hardware abstraction Base porting Symbian OS reference design porting File systems Overview of Symbian OS Development – DevKits, CustKits and SDKs CodeWarrior Tool Application & UI Development Client Server Framework ECOM STDLIB in Symbian iPhone Programming 80 Hours Introducing iPhone core specifications Understanding iPhone input and output Designing web pages for the iPhone Capturing iPhone events Introducing the webkit CSS transforms transitions and animations Using iUI for web apps Using Canvas for web apps Building web apps with Dashcode Writing Dashcode programs Debugging iPhone web pages SDK programming for web developers An introduction to object-oriented programming Introducing the iPhone OS Using Xcode and Interface builder Programming with the SDK Toolkit OS Concepts & Linux Programming 60 Hours Operating System Concepts What is an OS? Processes Scheduling & Synchronization Memory management Virtual Memory and Paging Linux Architecture Programming in Linux Linux Shell Programming Writing Device Drivers Configuring and Building GNU Cross-tool chain Configuring and Compiling Linux Virtual File System Porting Linux on Target Hardware WinCE.NET and Database Technology 80 Hours Execution Process in .NET Environment Language Interoperability Assemblies Need of C# Operators Namespaces & Assemblies Arrays Preprocessors Delegates and Events Boxing and Unboxing Regular Expression Collections Multithreading Programming Memory Management Exceptions Handling Win Forms Working with database ASP .NET Server Controls and client-side scripts ASP .NET Web Server Controls Validation Controls Principles of database management Need of RDBMS etc Client/Server Computing RDBMS Technologies Codd’s Rules Data Models Normalization Techniques ER Diagrams Data Flow Diagrams Database recovery & backup SQL Android Application 80 Hours Introduction of android Why develop for android Android SDK features Creating android activities Fundamental android UI design Intents, adapters, dialogs Android Technique for saving data Data base in Androids Maps, Geocoding, Location based services Toast, using alarms, Instant messaging Using blue tooth Using Telephony Introducing sensor manager Managing network and wi-fi connection Advanced androids development Linux kernel security Implement AIDL Interface. Project 120 Hours

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• Why is my RAID /dev/md1 showing up as /dev/md126? Is mdadm.conf being ignored?

  - by mmorris

  I created a RAID with: sudo mdadm --create --verbose /dev/md1 --level=mirror --raid-devices=2 /dev/sdb1 /dev/sdc1 sudo mdadm --create --verbose /dev/md2 --level=mirror --raid-devices=2 /dev/sdb2 /dev/sdc2 sudo mdadm --detail --scan returns: ARRAY /dev/md1 metadata=1.2 name=ion:1 UUID=aa1f85b0:a2391657:cfd38029:772c560e ARRAY /dev/md2 metadata=1.2 name=ion:2 UUID=528e5385:e61eaa4c:1db2dba7:44b556fb Which I appended it to /etc/mdadm/mdadm.conf, see below: # mdadm.conf # # Please refer to mdadm.conf(5) for information about this file. # # by default (built-in), scan all partitions (/proc/partitions) and all # containers for MD superblocks. alternatively, specify devices to scan, using # wildcards if desired. #DEVICE partitions containers # auto-create devices with Debian standard permissions CREATE owner=root group=disk mode=0660 auto=yes # automatically tag new arrays as belonging to the local system HOMEHOST <system> # instruct the monitoring daemon where to send mail alerts MAILADDR root # definitions of existing MD arrays # This file was auto-generated on Mon, 29 Oct 2012 16:06:12 -0500 # by mkconf $Id$ ARRAY /dev/md1 metadata=1.2 name=ion:1 UUID=aa1f85b0:a2391657:cfd38029:772c560e ARRAY /dev/md2 metadata=1.2 name=ion:2 UUID=528e5385:e61eaa4c:1db2dba7:44b556fb cat /proc/mdstat returns: Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10] md2 : active raid1 sdb2[0] sdc2[1] 208629632 blocks super 1.2 [2/2] [UU] md1 : active raid1 sdb1[0] sdc1[1] 767868736 blocks super 1.2 [2/2] [UU] unused devices: <none> ls -la /dev | grep md returns: brw-rw---- 1 root disk 9, 1 Oct 30 11:06 md1 brw-rw---- 1 root disk 9, 2 Oct 30 11:06 md2 So I think all is good and I reboot. After the reboot, /dev/md1 is now /dev/md126 and /dev/md2 is now /dev/md127????? sudo mdadm --detail --scan returns: ARRAY /dev/md/ion:1 metadata=1.2 name=ion:1 UUID=aa1f85b0:a2391657:cfd38029:772c560e ARRAY /dev/md/ion:2 metadata=1.2 name=ion:2 UUID=528e5385:e61eaa4c:1db2dba7:44b556fb cat /proc/mdstat returns: Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10] md126 : active raid1 sdc2[1] sdb2[0] 208629632 blocks super 1.2 [2/2] [UU] md127 : active (auto-read-only) raid1 sdb1[0] sdc1[1] 767868736 blocks super 1.2 [2/2] [UU] unused devices: <none> ls -la /dev | grep md returns: drwxr-xr-x 2 root root 80 Oct 30 11:18 md brw-rw---- 1 root disk 9, 126 Oct 30 11:18 md126 brw-rw---- 1 root disk 9, 127 Oct 30 11:18 md127 All is not lost, I: sudo mdadm --stop /dev/md126 sudo mdadm --stop /dev/md127 sudo mdadm --assemble --verbose /dev/md1 /dev/sdb1 /dev/sdc1 sudo mdadm --assemble --verbose /dev/md2 /dev/sdb2 /dev/sdc2 and verify everything: sudo mdadm --detail --scan returns: ARRAY /dev/md1 metadata=1.2 name=ion:1 UUID=aa1f85b0:a2391657:cfd38029:772c560e ARRAY /dev/md2 metadata=1.2 name=ion:2 UUID=528e5385:e61eaa4c:1db2dba7:44b556fb cat /proc/mdstat returns: Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10] md2 : active raid1 sdb2[0] sdc2[1] 208629632 blocks super 1.2 [2/2] [UU] md1 : active raid1 sdb1[0] sdc1[1] 767868736 blocks super 1.2 [2/2] [UU] unused devices: <none> ls -la /dev | grep md returns: brw-rw---- 1 root disk 9, 1 Oct 30 11:26 md1 brw-rw---- 1 root disk 9, 2 Oct 30 11:26 md2 So once again, I think all is good and I reboot. Again, after the reboot, /dev/md1 is /dev/md126 and /dev/md2 is /dev/md127????? sudo mdadm --detail --scan returns: ARRAY /dev/md/ion:1 metadata=1.2 name=ion:1 UUID=aa1f85b0:a2391657:cfd38029:772c560e ARRAY /dev/md/ion:2 metadata=1.2 name=ion:2 UUID=528e5385:e61eaa4c:1db2dba7:44b556fb cat /proc/mdstat returns: Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10] md126 : active raid1 sdc2[1] sdb2[0] 208629632 blocks super 1.2 [2/2] [UU] md127 : active (auto-read-only) raid1 sdb1[0] sdc1[1] 767868736 blocks super 1.2 [2/2] [UU] unused devices: <none> ls -la /dev | grep md returns: drwxr-xr-x 2 root root 80 Oct 30 11:42 md brw-rw---- 1 root disk 9, 126 Oct 30 11:42 md126 brw-rw---- 1 root disk 9, 127 Oct 30 11:42 md127 What am I missing here?

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• Anatomy of a .NET Assembly - Signature encodings

  - by Simon Cooper

  If you've just joined this series, I highly recommend you read the previous posts in this series, starting here, or at least these posts, covering the CLR metadata tables. Before we look at custom attribute encoding, we first need to have a brief look at how signatures are encoded in an assembly in general. Signature types There are several types of signatures in an assembly, all of which share a common base representation, and are all stored as binary blobs in the #Blob heap, referenced by an offset from various metadata tables. The types of signatures are: Method definition and method reference signatures. Field signatures Property signatures Method local variables. These are referenced from the StandAloneSig table, which is then referenced by method body headers. Generic type specifications. These represent a particular instantiation of a generic type. Generic method specifications. Similarly, these represent a particular instantiation of a generic method. All these signatures share the same underlying mechanism to represent a type Representing a type All metadata signatures are based around the ELEMENT_TYPE structure. This assigns a number to each 'built-in' type in the framework; for example, Uint16 is 0x07, String is 0x0e, and Object is 0x1c. Byte codes are also used to indicate SzArrays, multi-dimensional arrays, custom types, and generic type and method variables. However, these require some further information. Firstly, custom types (ie not one of the built-in types). These require you to specify the 4-byte TypeDefOrRef coded token after the CLASS (0x12) or VALUETYPE (0x11) element type. This 4-byte value is stored in a compressed format before being written out to disk (for more excruciating details, you can refer to the CLI specification). SzArrays simply have the array item type after the SZARRAY byte (0x1d). Multidimensional arrays follow the ARRAY element type with a series of compressed integers indicating the number of dimensions, and the size and lower bound of each dimension. Generic variables are simply followed by the index of the generic variable they refer to. There are other additions as well, for example, a specific byte value indicates a method parameter passed by reference (BYREF), and other values indicating custom modifiers. Some examples... To demonstrate, here's a few examples and what the resulting blobs in the #Blob heap will look like. Each name in capitals corresponds to a particular byte value in the ELEMENT_TYPE or CALLCONV structure, and coded tokens to custom types are represented by the type name in curly brackets. A simple field: int intField; FIELD I4 A field of an array of a generic type parameter (assuming T is the first generic parameter of the containing type): T[] genArrayField FIELD SZARRAY VAR 0 An instance method signature (note how the number of parameters does not include the return type): instance string MyMethod(MyType, int&, bool[][]); HASTHIS DEFAULT 3 STRING CLASS {MyType} BYREF I4 SZARRAY SZARRAY BOOLEAN A generic type instantiation: MyGenericType<MyType, MyStruct> GENERICINST CLASS {MyGenericType} 2 CLASS {MyType} VALUETYPE {MyStruct} For more complicated examples, in the following C# type declaration: GenericType<T> : GenericBaseType<object[], T, GenericType<T>> { ... } the Extends field of the TypeDef for GenericType will point to a TypeSpec with the following blob: GENERICINST CLASS {GenericBaseType} 3 SZARRAY OBJECT VAR 0 GENERICINST CLASS {GenericType} 1 VAR 0 And a static generic method signature (generic parameters on types are referenced using VAR, generic parameters on methods using MVAR): TResult[] GenericMethod<TInput, TResult>( TInput, System.Converter<TInput, TOutput>); GENERIC 2 2 SZARRAY MVAR 1 MVAR 0 GENERICINST CLASS {System.Converter} 2 MVAR 0 MVAR 1 As you can see, complicated signatures are recursively built up out of quite simple building blocks to represent all the possible variations in a .NET assembly. Now we've looked at the basics of normal method signatures, in my next post I'll look at custom attribute application signatures, and how they are different to normal signatures.

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• disks not ready in array causes mdadm to force initramfs shell

  - by RaidPinata

  Okay, this is starting to get pretty frustrating. I've read most of the other answers on this site that have anything to do with this issue but I'm still not getting anywhere. I have a RAID 6 array with 10 devices and 1 spare. The OS is on a completely separate device. At boot only three of the 10 devices in the raid are available, the others become available later in the boot process. Currently, unless I go through initramfs I can't get the system to boot - it just hangs with a blank screen. When I do boot through recovery (initramfs), I get a message asking if I want to assemble the degraded array. If I say no and then exit initramfs the system boots fine and my array is mounted exactly where I intend it to. Here are the pertinent files as near as I can tell. Ask me if you want to see anything else. # mdadm.conf # # Please refer to mdadm.conf(5) for information about this file. # # by default (built-in), scan all partitions (/proc/partitions) and all # containers for MD superblocks. alternatively, specify devices to scan, using # wildcards if desired. #DEVICE partitions containers # auto-create devices with Debian standard permissions # CREATE owner=root group=disk mode=0660 auto=yes # automatically tag new arrays as belonging to the local system HOMEHOST <system> # instruct the monitoring daemon where to send mail alerts MAILADDR root # definitions of existing MD arrays # This file was auto-generated on Tue, 13 Nov 2012 13:50:41 -0700 # by mkconf $Id$ ARRAY /dev/md0 level=raid6 num-devices=10 metadata=1.2 spares=1 name=Craggenmore:data UUID=37eea980:24df7b7a:f11a1226:afaf53ae Here is fstab # /etc/fstab: static file system information. # # Use 'blkid' to print the universally unique identifier for a # device; this may be used with UUID= as a more robust way to name devices # that works even if disks are added and removed. See fstab(5). # # <file system> <mount point> <type> <options> <dump> <pass> # / was on /dev/sdc2 during installation UUID=3fa1e73f-3d83-4afe-9415-6285d432c133 / ext4 errors=remount-ro 0 1 # swap was on /dev/sdc3 during installation UUID=c4988662-67f3-4069-a16e-db740e054727 none swap sw 0 0 # mount large raid device on /data /dev/md0 /data ext4 defaults,nofail,noatime,nobootwait 0 0 output of cat /proc/mdstat Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md0 : active raid6 sda[0] sdd[10](S) sdl[9] sdk[8] sdj[7] sdi[6] sdh[5] sdg[4] sdf[3] sde[2] sdb[1] 23441080320 blocks super 1.2 level 6, 512k chunk, algorithm 2 [10/10] [UUUUUUUUUU] unused devices: <none> Here is the output of mdadm --detail --scan --verbose ARRAY /dev/md0 level=raid6 num-devices=10 metadata=1.2 spares=1 name=Craggenmore:data UUID=37eea980:24df7b7a:f11a1226:afaf53ae devices=/dev/sda,/dev/sdb,/dev/sde,/dev/sdf,/dev/sdg,/dev/sdh,/dev/sdi,/dev/sdj,/dev/sdk,/dev/sdl,/dev/sdd Please let me know if there is anything else you think might be useful in troubleshooting this... I just can't seem to figure out how to change the boot process so that mdadm waits until the drives are ready to build the array. Everything works just fine if the drives are given enough time to come online. edit: changed title to properly reflect situation

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• Context migration in CUDA.NET

  - by Vyacheslav

  I'm currently using CUDA.NET library by GASS. I need to initialize cuda arrays (actually cublas vectors, but it doesn't matters) in one CPU thread and use them in other CPU thread. But CUDA context which holding all initialized arrays and loaded functions, can be attached to only one CPU thread. There is mechanism called context migration API to detach context from one thread and attach it to another. But i don't how to properly use it in CUDA.NET. I tried something like this: class Program { private static float[] vector1, vector2; private static CUDA cuda; private static CUBLAS cublas; private static CUdeviceptr ptr; static void Main(string[] args) { cuda = new CUDA(false); cublas = new CUBLAS(cuda); cuda.Init(); cuda.CreateContext(0); AllocateVectors(); cuda.DetachContext(); CUcontext context = cuda.PopCurrentContext(); GetVectorFromDeviceAsync(context); } private static void AllocateVectors() { vector1 = new float[]{1f, 2f, 3f, 4f, 5f}; ptr = cublas.Allocate(vector1.Length, sizeof (float)); cublas.SetVector(vector1, ptr); vector2 = new float[5]; } private static void GetVectorFromDevice(object objContext) { CUcontext localContext = (CUcontext) objContext; cuda.PushCurrentContext(localContext); cuda.AttachContext(localContext); //change vector somehow vector1[0] = -1; //copy changed vector to device cublas.SetVector(vector1, ptr); cublas.GetVector(ptr, vector2); CUDADriver.cuCtxPopCurrent(ref localContext); } private static void GetVectorFromDeviceAsync(CUcontext cUcontext) { Thread thread = new Thread(GetVectorFromDevice); thread.IsBackground = false; thread.Start(cUcontext); } } But execution fails on attempt to copy changed vector to device because context is not attached? Any ideas how i can get it work?

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• Async.Parallel or Array.Parallel.Map ?

  - by gurteen2

  Hello- I'm trying to implement a pattern I read from Don Syme's blog (http://blogs.msdn.com/dsyme/archive/2010/01/09/async-and-parallel-design-patterns-in-f-parallelizing-cpu-and-i-o-computations.aspx) which suggests that there are opportunities for massive performance improvements from leveraging asynchronous I/O. I am currently trying to take a piece of code that "works" one way, using Array.Parallel.Map, and see if I can somehow achieve the same result using Async.Parallel, but I really don't understand Async.Parallel, and cannot get anything to work. I have a piece of code (simplified below to illustrate the point) that successfully retrieves an array of data for one cusip. (A price series, for example) let getStockData cusip = let D = DataProvider() let arr = D.GetPriceSeries(cusip) return arr let data = Array.Parallel.map (fun x -> getStockData x) stockCusips So this approach contructs an array of arrays, by making a connection over the internet to my data vendor for each stock (which could be as many as 3000) and returns me an array of arrays (1 per stock, with a price series for each one). I admittedly don't understand what goes on underneath Array.Parallel.map, but am wondering if this is a scenario where there are resources wasted under the hood, and it actually could be faster using asynchronous I/O? So to test this out, I have attempted to make this function using asyncs, and I think that the function below follows the pattern in Don Syme's article using the URLs, but it won't compile with "let!". let getStockDataAsync cusip = async { let D = DataProvider() let! arr = D.GetData(cusip) return arr } The error I get is: This expression was expected to have type Async<'a but here has type obj It compiles fine with "let" instead of "let!", but I had thought the whole point was that you need the exclamation point in order for the command to run without blocking a thread. So the first question really is, what's wrong with my syntax above, in getStockDataAsync, and then at a higher level, can anyone offer some additional insight about asychronous I/O and whether the scenario I have presented would benefit from it, making it potentially much, much faster than Array.Parallel.map? Thanks so much.

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• Yii: Multi-language website - best practices.

  - by michal

  Hi, I find Yii great framework, and the example website created with yiic shell is a good point to start... however it doesn't cover the topic of multi-language websites, unfortunately. The docs covers the topic of translating short messages, but not keeping the multi-lingual content ... I'm about to start working on a website which needs to be in at least two languages, and I'm wondering what is the best way to keep content for that ... The problem is that the content is mixed extensively with common elements (like embedded video files). I need to avoid duplicating those commons ... so far I used to have an array of arrays containing texts (usually no more than 1-2 short paragraphs), then the view file was just rendering the text from an array. Now I'd like to avoid keeping it in arrays (which requires some attention when putting double quotations " " and is inconvenient in general...). So, what is the best way to keep those short paragraphs? Should I keep them in DB like (id | msg_id | language | content ) and then select them by msg_id & language? That still requires me to create some msg_id's and embed them into view file ... Is there any recommended paradigm for which Yii has some solutions? Thanks, m.

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• Submitting a multidimensional array via POST with php

  - by Fireflight

  I have a php form that has a known number of columns (ex. top diameter, bottom diameter, fabric, colour, quantity), but has an unknown number of rows, as users can add rows as they need. I've discovered how to take each of the fields(columns) and place them into an array of their own. <input name="topdiameter['+current+']" type="text" id="topdiameter'+current+'" size="5" /> <input name="bottomdiameter['+current+']" type="text" id="bottomdiameter'+current+'" size="5" /> So what I end up with in the HTML is: <tr> <td><input name="topdiameter[0]" type="text" id="topdiameter0" size="5" /></td> <td><input name="bottomdiameter[0]" type="text" id="bottomdiameter0" size="5" /></td> </tr> <tr> <td><input name="topdiameter[1]" type="text" id="topdiameter0" size="5" /></td> <td><input name="bottomdiameter[1]" type="text" id="bottomdiameter0" size="5" /></td> </tr> ...and so on. What I would like to do now is take all the rows and columns put them into a multidimensional array and email the contents of that to the client (preferably in a nicely formatted table). I haven't been able to really comprehend how to combine all those inputs and selects into a nice array. At this point, I'm going to have to try to use several 1D arrays, although I have the idea that using a single 2D array would be a better practice than using several 1D arrays.

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• adjacency list creation , out of Memory error

  - by p1

  Hello , I am trying to create an adjacency list to store a graph.The implementation works fine while storing 100,000 records. However,when I tried to store around 1million records I ran into OutofMemory Error : Exception in thread "main" java.lang.OutOfMemoryError: Java heap space at java.util.Arrays.copyOfRange(Arrays.java:3209) at java.lang.String.(String.java:215) at java.io.BufferedReader.readLine(BufferedReader.java:331) at java.io.BufferedReader.readLine(BufferedReader.java:362) at liarliar.main(liarliar.java:39) Following is my implementation HashMap<String,ArrayList<String>> adj = new HashMap<String,ArrayList<String>>(num); while ((str = in.readLine()) != null) { StringTokenizer Tok = new StringTokenizer(str); name = (String) Tok.nextElement(); cnt = Integer.valueOf(Tok.nextToken()); ArrayList<String> templist = new ArrayList<String>(cnt); while(cnt>0) { templist.add(in.readLine()); cnt--; } adj.put(name,templist); } //done creating a adjacency list I am wondering, if there is any better way to implement the adjacency list. Also, I know number of nodes right in the begining and , in the future I flatten the list as I visit nodes. Any suggestions ? Thanks

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• A Question about .net Rfc2898DeriveBytes class?

  - by IbrarMumtaz

  What is the difference in this class? as posed to just using Encoding.ASCII.GetBytes(string object); I have had relative success with either approach, the former is a more long winded approach where as the latter is simple and to the point. Both seem to allow you to do the same thing eventually but I am struggling to the see the point in using the former over the latter. The basic concept I have been able to grasp is that you can convert string passwords into byte arrays to be used for e.g a symmetric encryption class, AesManaged. Via the RFC class but you get to use SaltValues and password when creating your rfc object. I assume its more secure but still thats an uneducated guess at best ! Also that it allows you to return byte arrays of a certain size, well something like that. heres a few examples to show you where I am coming from? byte[] myPassinBytes = Encoding.ASCII.GetBytes("some password"); or string password = "P@%5w0r]>"; byte[] saltArray = Encoding.ASCII.GetBytes("this is my salt"); Rfc2898DeriveBytes rfcKey = new Rfc2898DeriveBytes(password, saltArray); The 'rfcKey' object can now be used towards setting up the the .Key or .IV properties on a Symmetric Encryption Algorithm class. ie. RijndaelManaged rj = new RijndaelManaged (); rj.Key = rfcKey.Getbytes(rj.KeySize / 8); rj.IV = rfcKey.Getbytes(rj.Blocksize / 8); 'rj' should be ready to go ! The confusing part ... so rather than using the 'rfcKey' object can I not just use my 'myPassInBytes' array to help set-up my 'rj' object???? I have tried doing this in VS2008 and the immediate answer is NO ! but have you guys got a better educated answer as to why the RFC class is used over the other alternative I have mentioned above and why????

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• How to make sure Solr/Lucene won't die with java.lang.OutOfMemoryError?

  - by taw

  I'm really puzzled why it keeps dying with java.lang.OutOfMemoryError during indexing even though it has a few GBs of memory. Is there a fundamental reason why it needs manual tweaking of config files / jvm parameters instead of it just figuring out how much memory is available and limiting itself to that? No other programs except Solr ever have this kind of problem. Yes, I can keep tweaking JVM heap size every time such crashes happen, but this is all so backwards. Here's stack trace of the latest such crash in case it is relevant: SEVERE: java.lang.OutOfMemoryError: Java heap space at java.util.Arrays.copyOfRange(Arrays.java:3209) at java.lang.String.<init>(String.java:216) at org.apache.lucene.index.TermBuffer.toTerm(TermBuffer.java:122) at org.apache.lucene.index.SegmentTermEnum.term(SegmentTermEnum.java:169) at org.apache.lucene.search.FieldCacheImpl$StringIndexCache.createValue(FieldCacheImpl.java:701) at org.apache.lucene.search.FieldCacheImpl$Cache.get(FieldCacheImpl.java:208) at org.apache.lucene.search.FieldCacheImpl.getStringIndex(FieldCacheImpl.java:676) at org.apache.lucene.search.FieldComparator$StringOrdValComparator.setNextReader(FieldComparator.java:667) at org.apache.lucene.search.TopFieldCollector$OneComparatorNonScoringCollector.setNextReader(TopFieldCollector.java:94) at org.apache.lucene.search.IndexSearcher.search(IndexSearcher.java:245) at org.apache.lucene.search.Searcher.search(Searcher.java:171) at org.apache.solr.search.SolrIndexSearcher.getDocListNC(SolrIndexSearcher.java:988) at org.apache.solr.search.SolrIndexSearcher.getDocListC(SolrIndexSearcher.java:884) at org.apache.solr.search.SolrIndexSearcher.search(SolrIndexSearcher.java:341) at org.apache.solr.handler.component.QueryComponent.process(QueryComponent.java:182) at org.apache.solr.handler.component.SearchHandler.handleRequestBody(SearchHandler.java:195) at org.apache.solr.handler.RequestHandlerBase.handleRequest(RequestHandlerBase.java:131) at org.apache.solr.core.SolrCore.execute(SolrCore.java:1316) at org.apache.solr.servlet.SolrDispatchFilter.execute(SolrDispatchFilter.java:338) at org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:241) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447) at java.lang.Thread.run(Thread.java:619)

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• Optimal Serialization of Primitive Types

  - by Greg Dean

  We are beginning to roll out more and more WAN deployments of our product (.Net fat client w/ IIS hosted Remoting backend). Because of this we are trying to reduce the size of the data on the wire. We have overridden the default serialization by implementing ISerializable (similar to this), we are seeing anywhere from 12% to 50% gains. Most of our efforts focus on optimizing arrays of primitive types. I would like to know if anyone knows of any fancy way of serializing primitive types, beyond the obvious? For example today we serialize an array of ints as follows: [4-bytes (array length)][4-bytes][4-bytes] Can anyone do significantly better? The most obvious example of a significant improvement, for boolean arrays, is putting 8 bools in each byte, which we already do. Note: Saving 7 bits per bool may seem like a waste of time, but when you are dealing with large magnitudes of data (which we are), it adds up very fast. Note: We want to avoid general compression algorithms because of the latency associated with it. Remoting only supports buffered requests/responses(no chunked encoding). I realize there is a fine line between compression and optimal serialization, but our tests indicate we can afford very specific serialization optimizations at very little cost in latency. Whereas reprocessing the entire buffered response into new compressed buffer is too expensive.

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• Why can't the compiler/JVM just make autoboxing "just work"?

  - by Pyrolistical

  Autoboxing is rather scary. While I fully understand the difference between == and .equals I can't but help have the follow bug the hell out of me: final List<Integer> foo = Arrays.asList(1, 1000); final List<Integer> bar = Arrays.asList(1, 1000); System.out.println(foo.get(0) == bar.get(0)); System.out.println(foo.get(1) == bar.get(1)); That prints true false Why did they do it this way? It something to do with cached Integers, but if that is the case why don't they just cache all Integers used by the program? Or why doesn't the JVM always auto unbox to primitive? Printing false false or true true would have been way better. EDIT I disagree about breakage of old code. By having foo.get(0) == bar.get(0) return true you already broke the code. Can't this be solved at the compiler level by replacing Integer with int in byte code (as long as it is never assigned null)

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• priority queue with limited space: looking for a good algorithm

  - by SigTerm

  This is not a homework. I'm using a small "priority queue" (implemented as array at the moment) for storing last N items with smallest value. This is a bit slow - O(N) item insertion time. Current implementation keeps track of largest item in array and discards any items that wouldn't fit into array, but I still would like to reduce number of operations further. looking for a priority queue algorithm that matches following requirements: queue can be implemented as array, which has fixed size and _cannot_ grow. Dynamic memory allocation during any queue operation is strictly forbidden. Anything that doesn't fit into array is discarded, but queue keeps all smallest elements ever encountered. O(log(N)) insertion time (i.e. adding element into queue should take up to O(log(N))). (optional) O(1) access for *largest* item in queue (queue stores *smallest* items, so the largest item will be discarded first and I'll need them to reduce number of operations) Easy to implement/understand. Ideally - something similar to binary search - once you understand it, you remember it forever. Elements need not to be sorted in any way. I just need to keep N smallest value ever encountered. When I'll need them, I'll access all of them at once. So technically it doesn't have to be a queue, I just need N last smallest values to be stored. I initially thought about using binary heaps (they can be easily implemented via arrays), but apparently they don't behave well when array can't grow anymore. Linked lists and arrays will require extra time for moving things around. stl priority queue grows and uses dynamic allocation (I may be wrong about it, though). So, any other ideas?

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• Replicating SQL's 'Join' in Python

  - by Daniel Mathews

  I'm in the process of trying to switch from R to Python (mainly issues around general flexibility). With Numpy, matplotlib and ipython, I've am able to cover all my use cases save for merging 'datasets'. I would like to simulate SQL's join by clause (inner, outer, full) purely in python. R handles this with the 'merge' function. I've tried the numpy.lib.recfunctions join_by, but it critical issues with duplicates along the 'key': join_by(key, r1, r2, jointype='inner', r1postfix='1', r2postfix='2', defaults=None, usemask=True, asrecarray=False) Join arrays r1 and r2 on key key. The key should be either a string or a sequence of string corresponding to the fields used to join the array. An exception is raised if the key field cannot be found in the two input arrays. Neither r1 nor r2 should have any duplicates along key: the presence of duplicates will make the output quite unreliable. Note that duplicates are not looked for by the algorithm. source: http://presbrey.mit.edu:1234/numpy.lib.recfunctions.html Any pointers or help will be most appreciated!

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• 3 index buffers

  - by bobobobo

  So, in both D3D and OpenGL there's ability to draw from an index buffer. The OBJ file format however does something weird. It specifies a bunch of vertices like: v -21.499660 6.424470 4.069845 v -25.117170 6.418100 4.068025 v -21.663851 8.282170 4.069585 v -21.651890 6.420180 4.068675 v -25.128481 8.281520 4.069585 Then it specifies a bunch of normals like.. vn 0.196004 0.558984 0.805680 vn -0.009523 0.210194 -0.977613 vn -0.147787 0.380832 -0.912757 vn 0.822108 0.567581 0.044617 vn 0.597037 0.057507 -0.800150 vn 0.809312 -0.045432 0.585619 Then it specifies a bunch of tex coords like vt 0.1225 0.5636 vt 0.6221 0.1111 vt 0.4865 0.8888 vt 0.2862 0.2586 vt 0.5865 0.2568 vt 0.1862 0.2166 THEN it specifies "faces" on the model like: f 1/2/5 2/3/7 8/2/6 f 5/9/7 6/3/8 5/2/1 So, in trying to render this with vertex buffers, In OpenGL I can use glVertexPointer, glNormalPointer and glTexCoordPointer to set pointers to each of the vertex, normal and texture coordinate arrays respectively.. but when it comes down to drawing with glDrawElements, I can only specify ONE set of indices, namely the indices it should use when visiting the vertices. Ok, then what? I still have 3 sets of indices to visit. In d3d its much the same - I can set up 3 streams: one for vertices, one for texcoords, and one for normals, but when it comes to using IDirect3DDevice9::DrawIndexedPrimitive, I can still only specify ONE index buffer, which will index into the vertices array. So, is it possible to draw from vertex buffers using different index arrays for each of the vertex, texcoord, and normal buffers (EITHER d3d or opengl!)

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• can a OOM be caused by not finding enough contiguous memory?

  - by raticulin

  I start some java code with -Xmx1024m, and at some point I get an hprof due to OOM. The hprof shows just 320mb, and give me a stack trace: at java.util.Arrays.copyOfRange([CII)[C (Arrays.java:3209) at java.lang.String.<init>([CII)V (String.java:215) at java.lang.StringBuilder.toString()Ljava/lang/String; (StringBuilder.java:430) ... This comes from a large string I am copying. I remember reading somewhere (cannot find where) what happened is these cases is: process still has not consumed 1gb of memory, is way below even if heap still below 1gb, it needs some amount of memory, and for copyOfRange() it has to be continuous memory, so even if it is not over the limit yet, it cannot find a large enough piece of memory on the host, it fails with an OOM. I have tried to look for doc on this (copyOfRange() needs a block of continuous memory), but could not find any. The other possible culprit would be not enough permgen memory. Can someone confirm or refute the continuous memory hypothesis? Any pointer to some doc would help too.

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• Comparable and Comparator contract with regards to null

  - by polygenelubricants

  Comparable contract specifies that e.compareTo(null) must throw NullPointerException. From the API: Note that null is not an instance of any class, and e.compareTo(null) should throw a NullPointerException even though e.equals(null) returns false. On the other hand, Comparator API mentions nothing about what needs to happen when comparing null. Consider the following attempt of a generic method that takes a Comparable, and return a Comparator for it that puts null as the minimum element. static <T extends Comparable<? super T>> Comparator<T> nullComparableComparator() { return new Comparator<T>() { @Override public int compare(T el1, T el2) { return el1 == null ? -1 : el2 == null ? +1 : el1.compareTo(el2); } }; } This allows us to do the following: List<Integer> numbers = new ArrayList<Integer>( Arrays.asList(3, 2, 1, null, null, 0) ); Comparator<Integer> numbersComp = nullComparableComparator(); Collections.sort(numbers, numbersComp); System.out.println(numbers); // "[null, null, 0, 1, 2, 3]" List<String> names = new ArrayList<String>( Arrays.asList("Bob", null, "Alice", "Carol") ); Comparator<String> namesComp = nullComparableComparator(); Collections.sort(names, namesComp); System.out.println(names); // "[null, Alice, Bob, Carol]" So the questions are: Is this an acceptable use of a Comparator, or is it violating an unwritten rule regarding comparing null and throwing NullPointerException? Is it ever a good idea to even have to sort a List containing null elements, or is that a sure sign of a design error?

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• How to integrate a Ipython console in a PyQT application

  - by user1800689

  I am developing PyQt software for my lab. In this software, I am loading different kind of RAW and analyzed data from a mySQL database (usually in arrays). I would like to integrate an Iython console in a Widget, so that I could interact easily with these data. I had some difficulties with Ipython 0.13 to do this. Here is what I already have (The whole code is very long, so I just show the part containing the widget, the Ipython console and the corresponding import line, if you need more, just tell me): ##I load everything useful to my application, including the following line from IPython.frontend.qt.console.qtconsoleapp import IPythonQtConsoleApp ##then is my whole software ##here is a class containing the Graphical User Interface elements. A button call the following function. self.Shell_Widget is the widget containing the Ipython console, self.MainWindow is the application mainwindow def EmbeddedIpython(self): """ This function should launch an Ipython console """ self.Shell_Widget = QtGui.QDockWidget(self.MainWindow) #Widget creation self.MainWindow.addDockWidget(4,self.Shell_Widget) self.Shell_Widget.setMinimumSize(400,420) console = IPythonQtConsoleApp() #Console Creation console.initialize() console.start() self.Shell_Widget.show() So, as wanted, an Ipython console is launched, and seems to work, but I can not access the whole application variables ,arrays etc... I think the Ipython console is launched independently from my software, but here is my limit in programming... Does someone know how to launch Ipython within my application? Maybe a missing parameter, or a different way to integrate Ipython. for information, this doesn't work: Embedding IPython Qt console in a PyQt application Thank you for your help!!

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• Should I use a collection here?

  - by Eva

  So I have code set up like this: public interface IInterface { public void setField(Object field); } public abstract class AbstractClass extends JPanel implements IInterface { private Object field_; public void setField(Object field) { field_ = field; } } public class ClassA extends AbstractClass { public ClassA() { // unique ClassA constructor stuff } public Dimension getPreferredSize() { return new Dimension(1, 1); } } public class ClassB extends AbstractClass { public ClassB() { // unique ClassB constructor stuff } public Dimension getPreferredSize() { return new Dimension(42, 42); } } public class ConsumerA { public ConsumerA(Collection<AbstractClass> collection) { for (AbstractClass abstractClass : collection) { abstractClass.setField(this); abstractClass.repaint(); } } } All hunky-dory so far, until public class ConsumerB { // Option 1 public ConsumerB(ClassA a, ClassB b) { methodThatOnlyTakesA(a); methodThatOnlyTakesB(b); } // Option 2 public ConsumerB(Collection<AbstractClass> collection) { for (IInterface i : collection) { if (i instanceof ClassA) { methodThatOnlyTakesA((ClassA) i); else if (i instanceof ClassB) { methodThatOnlyTakesB((ClassB) i); } } } } public class UsingOption1 { public static void main(String[] args) { ClassA a = new ClassA(); ClassB b = new ClassB(); Collection<AbstractClass> collection = Arrays.asList(a, b); ConsumerA consumerA = new ConsumerA(collection); ConsumerB consumerB = new ConsumerB(a, b); } } public class UsingOption2 { public static void main(String[] args) { Collection<AbstractClass> collection = Arrays.asList(new ClassA(), new ClassB()); ConsumerA = new ConsumerA(collection); ConsumerB = new ConsumerB(collection); } } With a lot more classes extending AbstractClass, both options get unwieldly. Option1 would make the constructor of ConsumerB really long. Also UsingOption1 would get long too. Option2 would have way more if statements than I feel comfortable with. Is there a viable Option3? If it helps, ClassA and ClassB have all the same methods, they're just implemented differently. Thanks for slogging through my code!

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• How to send complex types from PHP SoapClient to ASP.NET SOAP server?

  - by xaguilars

  Hello I'm having problems sending arrays, structs and arrays of structs from PHP to an ASP.NET SOAP server... Anyone have a sollution for this? I've googled for days and any sollution worked for me. Perphaps I'm forgetting something... There are examples of my code: $client = new SoapClient($options); $pCriteria = new stdClass(); $pCriteria->type=1; $pCriteria->capacity=4; //Test 1 (fail): $resp = $client->GetRooms(array("pCriteria"=>$pCriteria)); //Test 2 (fail): $resp = $client->GetRooms(array("pCriteria"=>new SoapVar($pCriteria, SOAP_ENC_OBJECT, "TCriteria", "http://www.w3.org/2001/XMLSchema"))); print_r($resp); I don't know how to code functions that require an array of TCriteria (TCriteria[], TCriteria_Array type) either... i've tried sending the raw array, a SoapVar with SOAP_ENC_ARRAY encoding and TCriteria_Array type, ... but it does not work (the SOAP server becomes unavaiable and needs to be restarted). I've tried creating classes for the complex types too, instead of stdClass, but not working. I don't know where's the problem. The server admins cannot help me and I haven't found any sollution over internet. I'm a bit desperate hehe. Can you help me please? Can you provide samples of code with the three cases (array of simple data, array of struct and struct) ? Thanks!

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• wopen calls when porting to Linux

  - by laura

  I have an application which was developed under Windows, but for gcc. The code is mostly OS-independent, with very few classes which are Windows specific because a Linux port was always regarded as necessary. The API, especially that which gets called as a direct result of user interaction, is using wide char arrays instead of char arrays (as a side note, I cannot change the API itself - at this point, std::wstring cannot be used). These are considered as encoded in UTF-16. In some places, the code opens files, mostly using the windows-specific _wopen function call. The problem with this is there is no wopen-like substitute for Linux because Linux "only deals with bytes". The question is: how do I port this code ? What if I wanted to open a file with the name "something™.log", how would I go about doing so in Linux ? Is a cast to char* sufficient, would the wide chars be picked up automatically based on the locale (probably not) ? Do I need to convert manually ? I'm a bit confused regarding this, perhaps someone could point me to some documentation regarding the matter.

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• C# Compress Triple Byte Array

  - by Mark

  Hi. I currently got this script, which compresses byte arrays. But I need it rewritten, so it can compress triple byte arrays [,,] Thanks! public static byte[] Compress(byte[] buffer) { MemoryStream ms = new MemoryStream(); GZipStream zip = new GZipStream(ms, CompressionMode.Compress, true); zip.Write(buffer, 0, buffer.Length); zip.Close(); ms.Position = 0; MemoryStream outStream = new MemoryStream(); byte[] compressed = new byte[ms.Length]; ms.Read(compressed, 0, compressed.Length); byte[] gzBuffer = new byte[compressed.Length + 4]; Buffer.BlockCopy(compressed, 0, gzBuffer, 4, compressed.Length); Buffer.BlockCopy(BitConverter.GetBytes(buffer.Length), 0, gzBuffer, 0, 4); return gzBuffer; } public static byte[] Decompress(byte[] gzBuffer) { MemoryStream ms = new MemoryStream(); int msgLength = BitConverter.ToInt32(gzBuffer, 0); ms.Write(gzBuffer, 4, gzBuffer.Length - 4); byte[] buffer = new byte[msgLength]; ms.Position = 0; GZipStream zip = new GZipStream(ms, CompressionMode.Decompress); zip.Read(buffer, 0, buffer.Length); return buffer; }

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• CakePHP - hasMany not fetching?

  - by Paolo Bergantino

  Maybe I am just having a slow day, but for the life of me I can't figure out why this is happening. I haven't done CakePHP in a while and I am trying to use the 1.3 version, but this doesn't seem to be working... I have two models: area.php <?php class Area extends AppModel { var $name = 'Area'; var $useTable = 'OR_AREA'; var $primaryKey = 'A_ID'; var $belongsTo = array( 'Building' => array( 'className' => 'Building', 'foreignKey' => 'FK_B_ID', ), 'Facility' => array( 'className' => 'Facility', 'foreignKey' => 'FK_F_ID', ), 'System' => array( 'className' => 'System', 'foreignKey' => 'FK_S_ID', ) ); } ?> building.php <?php class Building extends AppModel { var $name = 'Building'; var $useTable = 'OR_BLDG'; var $primaryKey = 'B_ID'; var $hasMany = array( 'Area' => array( 'className' => 'Area', 'foreignKey' => 'FK_B_ID', ) ); } ?> OR_AREA has a column titled FK_B_ID that refers to the B_ID. If I run something like: $this->Building->find('all', array('recursive' => 2)); I get empty [Area] arrays for all the Buildings even though there are plenty of Areas in the OR_AREA table that are associated to buildings. Not only that, the Query Table doesn't even show CakePHP attempted to find anything but all the records in OR_BLDG. All the more puzzling, if I do: $this->Area->find('all'); I get all the Areas and the [Building] arrays are populated when appropriate. What am I missing?

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• custom cells uitableview - cannot display all the rows

  - by Matt Facer

  Hi guys, I'm creating a uitableview with custom cells which I created in Interface Builder. There are currently three cells (UITableViewCell). I have a UITableView which is on the view. The code I have is fairly standard, but I cannot work out how to actually SHOW the three custom cells. I am using the cellForRowAtIndexPath method. My aim is to get a grouped uitableview which shows like the following Item - Name Settings - alert - time So the above indented view should be my grouped uitableview. The problem is, I cannot get it to show using code. The uitableview will ALWAYS be this. I am trying to replicate the settings style screen... so I do not have any arrays to display the uitableview cells. How do I actually display my three cells? I have the following code - (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { return 2; } - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { if (section == 0) return 1; else return 2; } - (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section { if(section == 0) return @"Item"; else return @"Settings"; } So all I need to know is how to actually display my custom cells inside the tableview! Thanks for any information. I've searched for AGES in google .. all the tutorials use arrays to display data!

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