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  • Binary Search Tree, cannot do traversal

    - by ihm
    Please see BST codes below. It only outputs "5". what did I do wrong? #include <iostream> class bst { public: bst(const int& numb) : root(new node(numb)) {} void insert(const int& numb) { root->insert(new node(numb), root); } void inorder() { root->inorder(root); } private: class node { public: node(const int& numb) : left(NULL), right(NULL) { value = numb; } void insert(node* insertion, node* position) { if (position == NULL) position = insertion; else if (insertion->value > position->value) insert(insertion, position->right); else if (insertion->value < position->value) insert(insertion, position->left); } void inorder(node* tree) { if (tree == NULL) return; inorder(tree->left); std::cout << tree->value << std::endl; inorder(tree->right); } private: node* left; node* right; int value; }; node* root; }; int main() { bst tree(5); tree.insert(4); tree.insert(2); tree.insert(10); tree.insert(14); tree.inorder(); return 0; }

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  • Understanding of a C Code Required..

    - by RBA
    int Size(struct node* node) { if(node == NULL) { return 0; } else if(node != NULL) { return (Size(node->left) + 1 + Size(node->right)); } } Hi, Can Anybody please post the stack trace for the following piece of code. Lets say if we insert the values 2, 1, 10, 5... Then what could be the stack representation during the recursion process.. Please, its very urgent, and its very confusing too...

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  • Haskell graph data type representation

    - by John Retallack
    I want to represent a graph in Haskell in the following manner: For each node I want to store it's value and a list of adjacent nodes,the problem which i'm having difficulties with is that I want the adjacent nodes to be stored as references to other nodes. For example: I want node ny to be stored as („NY“ (l p)) where l and p are adjacent nodes,and not as („NY“ („London“ „Paris“)). I tried something like this : data Node a = Node { value :: a , neighbors :: [Node a] }deriving (Show) let n1 = Node {value=1, neighbors=[n2]} let n2 = Node {value=1, neighbors=[n1 n3]} let n3 = Node {value=1, neighbors=[n2]} But i get en error in let,What am I doing wrong ?

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  • Following the Thread in OSB

    - by Antony Reynolds
    Threading in OSB The Scenario I recently led an OSB POC where we needed to get high throughput from an OSB pipeline that had the following logic: 1. Receive Request 2. Send Request to External System 3. If Response has a particular value   3.1 Modify Request   3.2 Resend Request to External System 4. Send Response back to Requestor All looks very straightforward and no nasty wrinkles along the way.  The flow was implemented in OSB as follows (see diagram for more details): Proxy Service to Receive Request and Send Response Request Pipeline   Copies Original Request for use in step 3 Route Node   Sends Request to External System exposed as a Business Service Response Pipeline   Checks Response to Check If Request Needs to Be Resubmitted Modify Request Callout to External System (same Business Service as Route Node) The Proxy and the Business Service were each assigned their own Work Manager, effectively giving each of them their own thread pool. The Surprise Imagine our surprise when, on stressing the system we saw it lock up, with large numbers of blocked threads.  The reason for the lock up is due to some subtleties in the OSB thread model which is the topic of this post.   Basic Thread Model OSB goes to great lengths to avoid holding on to threads.  Lets start by looking at how how OSB deals with a simple request/response routing to a business service in a route node. Most Business Services are implemented by OSB in two parts.  The first part uses the request thread to send the request to the target.  In the diagram this is represented by the thread T1.  After sending the request to the target (the Business Service in our diagram) the request thread is released back to whatever pool it came from.  A multiplexor (muxer) is used to wait for the response.  When the response is received the muxer hands off the response to a new thread that is used to execute the response pipeline, this is represented in the diagram by T2. OSB allows you to assign different Work Managers and hence different thread pools to each Proxy Service and Business Service.  In out example we have the “Proxy Service Work Manager” assigned to the Proxy Service and the “Business Service Work Manager” assigned to the Business Service.  Note that the Business Service Work Manager is only used to assign the thread to process the response, it is never used to process the request. This architecture means that while waiting for a response from a business service there are no threads in use, which makes for better scalability in terms of thread usage. First Wrinkle Note that if the Proxy and the Business Service both use the same Work Manager then there is potential for starvation.  For example: Request Pipeline makes a blocking callout, say to perform a database read. Business Service response tries to allocate a thread from thread pool but all threads are blocked in the database read. New requests arrive and contend with responses arriving for the available threads. Similar problems can occur if the response pipeline blocks for some reason, maybe a database update for example. Solution The solution to this is to make sure that the Proxy and Business Service use different Work Managers so that they do not contend with each other for threads. Do Nothing Route Thread Model So what happens if there is no route node?  In this case OSB just echoes the Request message as a Response message, but what happens to the threads?  OSB still uses a separate thread for the response, but in this case the Work Manager used is the Default Work Manager. So this is really a special case of the Basic Thread Model discussed above, except that the response pipeline will always execute on the Default Work Manager.   Proxy Chaining Thread Model So what happens when the route node is actually calling a Proxy Service rather than a Business Service, does the second Proxy Service use its own Thread or does it re-use the thread of the original Request Pipeline? Well as you can see from the diagram when a route node calls another proxy service then the original Work Manager is used for both request pipelines.  Similarly the response pipeline uses the Work Manager associated with the ultimate Business Service invoked via a Route Node.  This actually fits in with the earlier description I gave about Business Services and by extension Route Nodes they “… uses the request thread to send the request to the target”. Call Out Threading Model So what happens when you make a Service Callout to a Business Service from within a pipeline.  The documentation says that “The pipeline processor will block the thread until the response arrives asynchronously” when using a Service Callout.  What this means is that the target Business Service is called using the pipeline thread but the response is also handled by the pipeline thread.  This implies that the pipeline thread blocks waiting for a response.  It is the handling of this response that behaves in an unexpected way. When a Business Service is called via a Service Callout, the calling thread is suspended after sending the request, but unlike the Route Node case the thread is not released, it waits for the response.  The muxer uses the Business Service Work Manager to allocate a thread to process the response, but in this case processing the response means getting the response and notifying the blocked pipeline thread that the response is available.  The original pipeline thread can then continue to process the response. Second Wrinkle This leads to an unfortunate wrinkle.  If the Business Service is using the same Work Manager as the Pipeline then it is possible for starvation or a deadlock to occur.  The scenario is as follows: Pipeline makes a Callout and the thread is suspended but still allocated Multiple Pipeline instances using the same Work Manager are in this state (common for a system under load) Response comes back but all Work Manager threads are allocated to blocked pipelines. Response cannot be processed and so pipeline threads never unblock – deadlock! Solution The solution to this is to make sure that any Business Services used by a Callout in a pipeline use a different Work Manager to the pipeline itself. The Solution to My Problem Looking back at my original workflow we see that the same Business Service is called twice, once in a Routing Node and once in a Response Pipeline Callout.  This was what was causing my problem because the response pipeline was using the Business Service Work Manager, but the Service Callout wanted to use the same Work Manager to handle the responses and so eventually my Response Pipeline hogged all the available threads so no responses could be processed. The solution was to create a second Business Service pointing to the same location as the original Business Service, the only difference was to assign a different Work Manager to this Business Service.  This ensured that when the Service Callout completed there were always threads available to process the response because the response processing from the Service Callout had its own dedicated Work Manager. Summary Request Pipeline Executes on Proxy Work Manager (WM) Thread so limited by setting of that WM.  If no WM specified then uses WLS default WM. Route Node Request sent using Proxy WM Thread Proxy WM Thread is released before getting response Muxer is used to handle response Muxer hands off response to Business Service (BS) WM Response Pipeline Executes on Routed Business Service WM Thread so limited by setting of that WM.  If no WM specified then uses WLS default WM. No Route Node (Echo functionality) Proxy WM thread released New thread from the default WM used for response pipeline Service Callout Request sent using proxy pipeline thread Proxy thread is suspended (not released) until the response comes back Notification of response handled by BS WM thread so limited by setting of that WM.  If no WM specified then uses WLS default WM. Note this is a very short lived use of the thread After notification by callout BS WM thread that thread is released and execution continues on the original pipeline thread. Route/Callout to Proxy Service Request Pipeline of callee executes on requestor thread Response Pipeline of caller executes on response thread of requested proxy Throttling Request message may be queued if limit reached. Requesting thread is released (route node) or suspended (callout) So what this means is that you may get deadlocks caused by thread starvation if you use the same thread pool for the business service in a route node and the business service in a callout from the response pipeline because the callout will need a notification thread from the same thread pool as the response pipeline.  This was the problem we were having. You get a similar problem if you use the same work manager for the proxy request pipeline and a business service callout from that request pipeline. It also means you may want to have different work managers for the proxy and business service in the route node. Basically you need to think carefully about how threading impacts your proxy services. References Thanks to Jay Kasi, Gerald Nunn and Deb Ayers for helping to explain this to me.  Any errors are my own and not theirs.  Also thanks to my colleagues Milind Pandit and Prasad Bopardikar who travelled this road with me. OSB Thread Model Great Blog Post on Thread Usage in OSB

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  • What are functional-programming ways of implementing Conway's Game of Life

    - by George Mauer
    I recently implemented for fun Conway's Game of Life in Javascript (actually coffeescript but same thing). Since javascript can be used as a functional language I was trying to stay to that end of the spectrum. I was not happy with my results. I am a fairly good OO programmer and my solution smacked of same-old-same-old. So long question short: what is the (pseudocode) functional style of doing it? Here is Pseudocode for my attempt: class Node update: (board) -> get number_of_alive_neighbors from board get this_is_alive from board if this_is_alive and number_of_alive_neighbors < 2 then die if this_is_alive and number_of_alive_neighbors > 3 then die if not this_is_alive and number_of_alive_neighbors == 3 then alive class NodeLocations at: (x, y) -> return node value at x,y of: (node) -> return x,y of node class Board getNeighbors: (node) -> use node_locations to check 8 neighbors around node and return count nodes = for 1..100 new Node state = new NodeState(nodes) locations = new NodeLocations(nodes) board = new Board(locations, state) executeRound: state = clone state accumulated_changes = for n in nodes n.update(board) apply accumulated_changes to state board = new Board(locations, state)

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  • Class hierarchy problem in this social network model

    - by Gerenuk
    I'm trying to design a class system for a social network data model - basically a link/object system. Now I have roughly the following structure (simplified and only relevant methods shown) class Data: "used to handle the data with mongodb" "can link, unlink data and also return other linked data" "is basically a proxy object that only stores _id and accesses mongodb on requests" "it looks like {_id: ..., _out: [id1, id2,...], _inc: [id3, id4, ...]}" def get_node(self, id) "create a new Data object from the underlying mongodb" "each data object can potentially create a reference object to new mongo data" "this is needed when the data returns the linked objects" class Node: """ this class proxies linking calls to .data it includes additional network logic operations whereas Data only contains a basic database solution """ def __init__(self, data): "the infrastructure realization is stored as composition by an included object data" "Node bascially proxies most calls to the infrastructure object data" def get_node(self, data): "creates a new object of class Object or Link depending on data" class Object(Node): "can have multiple connections to Link" class Link(Node): "has one 'in' and one 'out' connection to an Object" This system is working, however maybe wouldn't work outside Python. Note that after reading links Now I have two questions here: 1) I want to infrastructure of the data storage to be replacable. Earlier I had Data as a superclass of Node so that it provided the neccessary calls. But (without dirty Python tricks) you cannot replace the superclass dynamically. Is using composition therefore recommended? The drawback is that I have to proxy most calls (link, unlink etc). Any thoughts? 2) The class Node contains the common method .get_node which is used to built new Object or Link instances after reading out the data. Some attribute of data decided whether the object which is only stored by id should be instantiated as an Object or Link class. The problem here is that Node needs to know about Object and Link in advance, which seems dodgy. Do you see a different solution? Both Object and Link need to instantiate one of all possible types depending on what the find in their linked data. Are there any other ideas how to implement a flexible Object/Link structure where the underlying database storage is isolated?

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  • Graph data structures and journal format for mini-IDE

    - by matec
    Background: I am writing a small/partial IDE. Code is internally converted/parsed into a graph data structure (for fast navigation, syntax-check etc). Functionality to undo/redo (also between sessions) and restoring from crash is implemented by writing to and reading from journal. The journal records modifications to the graph (not to the source). Question: I am hoping for advice on a decision on data-structures and journal format. For the graph I see two possible versions: g-a Graph edges are implemented in the way that one node stores references to other nodes via memory address g-b Every node has an ID. There is an ID-to-memory-address map. Graph uses IDs (instead of addresses) to connect nodes. Moving along an edge from one node to another each time requires lookup in ID-to-address map. And also for the journal: j-a There is a current node (like current working directory in a shell + file-system setting). The journal contains entries like "create new node and connect to current", "connect first child of current node" (relative IDs) j-b Journal uses absolute IDs, e.g. "delete edge 7 - 5", "delete node 5" I could e.g. combine g-a with j-a or combine g-b with j-b. In principle also g-b and j-a should be possible. [My first/original attempt was g-a and a version of j-b that uses addresses, but that turned out to cause severe restrictions: nodes cannot change their addresses (or journal would have to keep track of it), and using journal between two sessions is a mess (or even impossible)] I wonder if variant a or variant b or a combination would be a good idea, what advantages and disadvantages they would have and especially if some variant might be causing troubles later.

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  • Algorithmic problem - quickly finding all #'s where value %x is some given value

    - by Steve B.
    Problem I'm trying to solve, apologies in advance for the length: Given a large number of stored records, each with a unique (String) field S. I'd like to be able to find through an indexed query all records where Hash(S) % N == K for any arbitrary N, K (e.g. given a million strings, find all strings where HashCode(s) % 17 = 5. Is there some way of memoizing this so that we can quickly answer any question of this form without doing the % on every value? The motivation for this is a system of N distributed nodes, where each record has to be assigned to at least one node. The nodes are numbered 0 - (K-1) , and each node has to load up all of the records that match it's number: If we have 3 nodes Node 0 loads all records where Hash % 3 ==0 Node 1 loads all records where Hash % 3 ==1 Node 2 loads all records where Hash % 3 ==2 adding a 4th node, obviously all the assignments have to be recomputed - Node 0 loads all records where Hash % 4 ==0 ... etc I'd like to easily find these records through an indexed query without having to compute the mod individually. The best I've been able to come up with so far: If we take the prime factors of N (p1 * p2 * ... ) if N % M == I then p % M == I % p for all of N's prime factors e.g. 10 nodes : N % 10 == 6 then N % 2 = 0 == 6 %2 N % 5 = 1 == 6 %5 so storing an array of the "%" of N for the first "reasonable" number of primes for my data set should be helpful. For example in the above example we store the hash and the primes HASH PRIMES (array of %2, %3, %5, %7, ... ]) 16 [0 1 1 2 .. ] so looking for N%10 == 6 is equivalent to looking for all values where array[1]==1 and array[2] == 1. However, this breaks at the first prime larger than the highest number I'm storing in the factor table. Is there a better way?

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  • How to change careers

    - by Jack Black
    For the past 4 years I have worked in c# doing web development. I have really enjoyed it, learnt a lot and have a worked hard to get to a position where I am earning good money and enjoy the work. However lately - I have wanted a change. What with the "native renaissance" I would like to change my career from being high level application and web development to more down to the metal native development. I haven't done any c or c++ since Uni over 4 years ago and so I have begun reading text books and websites to brush up. However - one major issue I have is that I have no practical experience with C++ and although I am brushing up on it, there will be a lot I don't know. Most of the jobs I have seen in native code around me all require native experience. The only positions I can find that don't explicitly ask for native experience are junior level positions. In my current role I am a mid level developer and although there would be a lot to learn in a c++ position, I wouldn't class myself as a junior. I guess my question is, how do people solve this issue when changing programming languages for their profession and / or how would you approach this hurdle? Like I said, I would really like to try out native development professionally but I wouldn't want to move back to a junior role. Would employers consider years of managed development and native hobby projects enough experience?

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  • A* PathFinding Not Consistent

    - by RedShft
    I just started trying to implement a basic A* algorithm in my 2D tile based game. All of the nodes are tiles on the map, represented by a struct. I believe I understand A* on paper, as I've gone through some pseudo code, but I'm running into problems with the actual implementation. I've double and tripled checked my node graph, and it is correct, so I believe the issue to be with my algorithm. This issue is, that with the enemy still, and the player moving around, the path finding function will write "No Path" an astounding amount of times and only every so often write "Path Found". Which seems like its inconsistent. This is the node struct for reference: struct Node { bool walkable; //Whether this node is blocked or open vect2 position; //The tile's position on the map in pixels int xIndex, yIndex; //The index values of the tile in the array Node*[4] connections; //An array of pointers to nodes this current node connects to Node* parent; int gScore; int hScore; int fScore; } Here is the rest: http://pastebin.com/cCHfqKTY This is my first attempt at A* so any help would be greatly appreciated.

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  • NetBeans Development 7 - Windows 7 64-bit … JNI native calls ... a how to guide

    - by CirrusFlyer
    I provide this for you to hopefully save you some time and pain. As part of my expereince in getting to know NB Development v7 on my Windows 64-bit workstation I found another frustrating adventure in trying to get the JNI (Java Native Interface) abilities up and working in my project. As such, I am including a brief summary of steps required (as all the documentation I found was completely incorrect for these versions of Windows and NetBeans on how to do JNI). It took a couple of days of experimentation and reviewing every webpage I could find that included these technologies as keyword searches. Yuk!! Not fun. To begin, as NetBeans Development is "all about modules" if you are reading this you probably have a need for one, or more, of your modules to perform JNI calls. Most of what is available on this site or the Internet in general (not to mention the help file in NB7) is either completely wrong for these versions, or so sparse as to be essentially unuseful to anyone other than a JNI expert. Here is what you are looking for ... the "cut to the chase" - "how to guide" to get a JNI call up and working on your NB7 / Windows 64-bit box. 1) From within your NetBeans Module (not the host appliation) declair your native method(s) and make sure you can compile the Java source without errors. Example: package org.mycompanyname.nativelogic; public class NativeInterfaceTest { static { try { if (System.getProperty( "os.arch" ).toLowerCase().equals( "amd64" ) ) System.loadLibrary( <64-bit_folder_name_on_file_system>/<file_name.dll> ); else System.loadLibrary( <32-bit_folder_name_on_file_system>/<file_name.dll> ); } catch (SecurityException se) {} catch (UnsatisfieldLinkError ule) {} catch (NullPointerException npe) {} } public NativeInterfaceTest() {} native String echoString(String s); } Take notice to the fact that we only load the Assembly once (as it's in a static block), because othersise you will throw exceptions if attempting to load it again. Also take note of our single (in this example) native method titled "echoString". This is the method that our C / C++ application is going to implement, then via the majic of JNI we'll call from our Java code. 2) If using a 64-bit version of Windows (which we are here) we need to open a 64-bit Visual Studio Command Prompt (versus the standard 32-bit version), and execute the "vcvarsall" BAT file, along with an "amd64" command line argument, to set the environment up for 64-bit tools. Example: <path_to_Microsoft_Visual_Studio_10.0>/VC/vcvarsall.bat amd64 Take note that you can use any version of the C / C++ compiler from Microsoft you wish. I happen to have Visual Studio 2005, 2008, and 2010 installed on my box so I chose to use "v10.0" but any that support 64-bit development will work fine. The other important aspect here is the "amd64" param. 3) In the Command Prompt change drives \ directories on your computer so that you are at the root of the fully qualified Class location on the file system that contains your native method declairation. Example: The fully qualified class name for my natively declair method is "org.mycompanyname.nativelogic.NativeInterfaceTest". As we successfully compiled our Java in Step 1 above, we should find it contained in our NetBeans Module something similar to the following: "/build/classes/org/mycompanyname/nativelogic/NativeInterfaceTest.class" We need to make sure our Command Prompt sets, as the current directly, "/build/classes" because of our next step. 4) In this step we'll create our C / C++ Header file that contains the JNI required statments. Type the following in the Command Prompt: javah -jni org.mycompanyname.nativelogic.NativeInterfaceTest and hit enter. If you receive any kind of error that states this is an unrecognized command that simply means your Windows computer does not know the PATH to that command (it's in your /bin folder). Either run the command from there, or include the fully qualified path name when invoking this application, or set your computer's PATH environmental variable to include that path in its search. This should produce a file called "org_mycompanyname_nativelogic_NativeInterfaceTest.h" ... a C Header file. I'd make a copy of this in case you need a backup later. 5) Edit the NativeInterfaceTest.h header file and include an implementation for the echoString() method. Example: JNIEXPORT jstring JNICALL Java_org_mycompanyname_nativelogic_NativeInterfaceTest_echoString (JNIEnv *env, jobject jobj, jstring js) { return((*env)->NewStringUTF(env, "My JNI is up and working after lots of research")); } Notice how you can't simply return a normal Java String (because you're in C at the moment). You have to tell the passed in JVM variable to create a Java String for you that will be returned back. Check out the following Oracle web page for other data types and how to create them for JNI purposes. 6) Close and Save your changes to the Header file. Now that you've added an implementation to the Header change the file extention from ".h" to ".c" as it's now a C source code file that properly implements the JNI required interface. Example: NativeInterfaceTest.c 7) We need to compile the newly created source code file and Link it too. From within the Command Prompt type the following: cl /I"path_to_my_jdks_include_folder" /I"path_to_my_jdks_include_win32_folder" /D:AMD64=1 /LD NativeInterfaceTest.c /FeNativeInterfaceTest.dll /link /machine:x64 Example: cl /I"D:/Program Files/Java/jdk1.6.0_21/include" /I"D:/Program Files/java/jdk1.6.0_21/include/win32" /D:AMD64=1 /LD NativeInterfaceTest.c /FeNativeInterfaceTest.dll /link /machine:x64 Notice the quotes around the paths to the 'include" and 'include/win32' folders is required because I have spaces in my folder names ... 'Program Files'. You can include them if you have no spaces without problems, but they are mandatory if you have spaces when using a command prompt. This will generate serveral files, but it's the DLL we're interested in. This is what the System.loadLirbary() java method is looking for. 8) Congratuations! You're at the last step. Simply take the DLL Assembly and paste it at the following location: <path_of_NetBeansProjects_folder>/<project_name>/<module_name>/build/cluster/modules/lib/x64 Note that you'll probably have to create the "lib" and "x64" folders. Example: C:\Users\<user_name>\Documents\NetBeansProjects\<application_name>\<module_name>\build\cluster\modules\lib\x64\NativeInterfaceTest.dll Java code ... notice how we don't inlude the ".dll" file extension in the loadLibrary() call? System.loadLibrary( "/x64/NativeInterfaceTest" ); Now, in your Java code you can create a NativeInterfaceTest object and call the echoString() method and it will return the String value you typed in the NativeInterfaceTest.c source code file. Hopefully this will save you the brain damage I endured trying to figure all this out on my own. Good luck and happy coding!

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  • Big Data – Buzz Words: What is Hadoop – Day 6 of 21

    - by Pinal Dave
    In yesterday’s blog post we learned what is NoSQL. In this article we will take a quick look at one of the four most important buzz words which goes around Big Data – Hadoop. What is Hadoop? Apache Hadoop is an open-source, free and Java based software framework offers a powerful distributed platform to store and manage Big Data. It is licensed under an Apache V2 license. It runs applications on large clusters of commodity hardware and it processes thousands of terabytes of data on thousands of the nodes. Hadoop is inspired from Google’s MapReduce and Google File System (GFS) papers. The major advantage of Hadoop framework is that it provides reliability and high availability. What are the core components of Hadoop? There are two major components of the Hadoop framework and both fo them does two of the important task for it. Hadoop MapReduce is the method to split a larger data problem into smaller chunk and distribute it to many different commodity servers. Each server have their own set of resources and they have processed them locally. Once the commodity server has processed the data they send it back collectively to main server. This is effectively a process where we process large data effectively and efficiently. (We will understand this in tomorrow’s blog post). Hadoop Distributed File System (HDFS) is a virtual file system. There is a big difference between any other file system and Hadoop. When we move a file on HDFS, it is automatically split into many small pieces. These small chunks of the file are replicated and stored on other servers (usually 3) for the fault tolerance or high availability. (We will understand this in the day after tomorrow’s blog post). Besides above two core components Hadoop project also contains following modules as well. Hadoop Common: Common utilities for the other Hadoop modules Hadoop Yarn: A framework for job scheduling and cluster resource management There are a few other projects (like Pig, Hive) related to above Hadoop as well which we will gradually explore in later blog posts. A Multi-node Hadoop Cluster Architecture Now let us quickly see the architecture of the a multi-node Hadoop cluster. A small Hadoop cluster includes a single master node and multiple worker or slave node. As discussed earlier, the entire cluster contains two layers. One of the layer of MapReduce Layer and another is of HDFC Layer. Each of these layer have its own relevant component. The master node consists of a JobTracker, TaskTracker, NameNode and DataNode. A slave or worker node consists of a DataNode and TaskTracker. It is also possible that slave node or worker node is only data or compute node. The matter of the fact that is the key feature of the Hadoop. In this introductory blog post we will stop here while describing the architecture of Hadoop. In a future blog post of this 31 day series we will explore various components of Hadoop Architecture in Detail. Why Use Hadoop? There are many advantages of using Hadoop. Let me quickly list them over here: Robust and Scalable – We can add new nodes as needed as well modify them. Affordable and Cost Effective – We do not need any special hardware for running Hadoop. We can just use commodity server. Adaptive and Flexible – Hadoop is built keeping in mind that it will handle structured and unstructured data. Highly Available and Fault Tolerant – When a node fails, the Hadoop framework automatically fails over to another node. Why Hadoop is named as Hadoop? In year 2005 Hadoop was created by Doug Cutting and Mike Cafarella while working at Yahoo. Doug Cutting named Hadoop after his son’s toy elephant. Tomorrow In tomorrow’s blog post we will discuss Buzz Word – MapReduce. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • 11gR2 ??????????

    - by Allen Gao
    ???????11gR2 GI????????????????????,?10g????,???????GI?????????????1.Ocssd.bin:????????10g??????????,???????(Node Monitoring)????(Group Management)?????????????“??????????”????????2.Cssdagent.bin/Cssdmonitor.bin:?2????11gR2??????????????ocssd.bin??????(Local HeartBeat),??????1??????????????????ocssd.bin???????????,????????ocssd.bin????????,??????,???????????10g??oclsomon/oclsvmon(?????????????)?oprocd????,????11gR2???????—rebootless restart,?????????11.2.0.2????????????,????????????(????????)??????ocssd.bin?????,??????????????,??????????GI stack?????,??GI stack??????????(short disk I/O timeout)??graceful shutdown,????????,??,????????????????????????11gR2 ??????????????1.Ocssd.log2.Cssdagent ? cssdmonitor logs<GI_home>/log/<node_name>/agent/ohasd/oracssdagent_root/oracssdagent_root.log<GI_home>/log/<node_name>/agent/ohasd/oracssdmonitor_root_root/oracssdmonitor_root.log3.Cluster alert log<GI_home>/log/<node_name>/alert<node_name>.log4.OS log5.OSW ?? CHM ????,??????????????????1.???????????????????????????????,??????10g???????????????????????????GI alert log ??,?????node2?2012-08-15 16:30:06.554 [cssd(11011) ]CRS-1612:Network communication with node node1 (1) missing for 50% of timeout interval.  Removal of this node from cluster in 14.510 seconds2012-08-15 16:30:13.586 [cssd(11011) ]CRS-1611:Network communication with node node1 (1) missing for 75% of timeout interval.  Removal of this node from cluster in 7.470 seconds2012-08-15 16:30:18.606 [cssd(11011) ]CRS-1610:Network communication with node node1 (1) missing for 90% of timeout interval.  Removal of this node from cluster in 2.450 seconds2012-08-15 16:30:21.073 [cssd(11011) ]CRS-1632:Node node1 is being removed from the cluster in cluster incarnation 2363798322012-08-15 16:30:21.086 [cssd(11011) ]CRS-1601:CSSD Reconfiguration complete. Active nodes are node2 .?????????????node1?????????????????,???????, node2?? node1 ?????????node1 ???,???node1 ???????????????(????os log ??OSW ????),??node1 ???????node2??node1?????????,????node1??????????,???reconfiguration,????????????,????????????,?11.2.0.2??,??rebootless restart???,node eviction ????????GI stack??,????????????,???node2?node1?????????,node1?ocssd.bin??????(????ocssd.log??)??node1???????????????,??node1??????GI node eviction????2.???????????????,?????10g???????,???????????3.??ocssd.bin ????Cssdagent/Cssdmonitor.bin????????????,??????,????,????oracssdagent_root.log ?oracssdmonitor_root.log ????????2012-07-23 14:09:58.506: [ USRTHRD][1095805248] (:CLSN00111: )clsnproc_needreboot: Impending reboot at 75% of limit 28030; disk timeout 28030, network timeout 26380, last heartbeat from CSSD at epoch seconds 1343023777.410, 21091 milliseconds ago based on invariant clock 269251595; now polling at 100 ms……2012-07-23 14:10:02.704: [ USRTHRD][1095805248] (:CLSN00111: )clsnproc_needreboot: Impending reboot at 90% of limit 28030; disk timeout 28030, network timeout 26380, last heartbeat from CSSD at epoch seconds 1343023777.410, 25291 milliseconds ago based on invariant clock 269251595; now polling at 100 ms……???????????????timeout???28 ???(misscount – reboot time)?4.?????????????????? ??????????????????????,????ocssd.bin??????,?????????????,?????????????ocssd.bin??,????????os???????????OSW??,???? ??????? cpu ???Linux OSWbb v5.0 node1SNAP_INTERVAL 30CPU_COUNT 8OSWBB_ARCHIVE_DEST /osw/archiveprocs -----------memory---------- ---swap-- -----io---- -system-- -----cpu------r  b   swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa……zzz ***Mon Aug 30 17:55:21 CST 2012158  6 4200956 923940   7664 19088464    0    0  1296  3574 11153 231579  0 100  0  0  0zzz ***Mon Aug 30 17:55:53 CST 2012135  4 4200956 923760   7812 19089344    0    0     4    45  570 14563  0 100  0  0  0zzz ***Mon Aug 30 17:56:53 CST 2012126  2 4200956 923784   8396 19083620    0    0   196  1121  651 15941  2 98  0  0  0?????????????,????10g??????11gR2????????????????,??????,????????Note 1050693.1 : Troubleshooting 11.2 Clusterware Node Evictions (Reboots)

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  • How to "check for overwide node(s)." in graphviz dot file

    - by Tomas Forsman
    I'm trying to generate a large graph using graphviz. I have a generated text file with nodes defined in the dot format. When I try to generate a PNG file from the file using dot -Tpng:cairo graph.txt graph.png I get the error message: Error: Edge length 136228 larger than maximum 65535 allowed. Check for overwide node(s). How do I actually "check for overwide node(s)" ?

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  • How to read expected child nodes of a given node from schema in PHP?

    - by MartyIX
    I was wondering if there's an implementation of a XML schema reader that for an arbitrary node in XML schema provides list of nodes which are supposed to be present as child nodes of given node, restrictions on nodes and so on. I'm planning to program it for my purposes but I would like to know if it isn't solved somewhere. I really need only a small subset what I described above. Thanks for tips!

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  • How to embed a node on homepage in Drupal 6?

    - by Sushi
    How can I embed a node on the front page in Drupal 6. The node basically has the image upload field along with title and description. I want it to some how appear on the homepage alongwith a "views" which shows the uploaded images at the bottom. It's basically just an attempt at creating something like imageshack as an experiment. I am pretty n00b when it comes to drupal so please be more descriptive.

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