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  • Is Java much harder to "tweak" for performance compared with C/C++?

    - by user997112
    Does the "magic" of the JVM hinder the influence a programmer has over micro-optimisations in Java? I recently read in C++ sometimes the ordering of the data members can provide optimizations (granted, in the microsecond environment) and I presumed a programmer's hands are tied when it comes to squeezing performance from Java? I appreciate a decent algorithm provides greater speed-gains, but once you have the correct algorithm is Java harder to tweak due to the JVM control? If not, could people give examples of what tricks you can use in Java (besides simple compiler flags).

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  • Continuous Collision Detection Techniques

    - by Griffin
    I know there are quite a few continuous collision detection algorithms out there , but I can't find a list or summary of different 2D techniques; only tutorials on specific algorithms. What techniques are out there for calculating when different 2D bodies will collide and what are the advantages / disadvantages of each? I say techniques and not algorithms because I have not yet decided on how I will store different polygons which might be concave or even have holes. I plan to make a decision on this based on what the algorithm requires (for instance if an algorithm breaks down a polygon into triangles or convex shapes I will simply store the polygon data in this form).

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  • What top companies look for in an Interview?

    - by Geek
    Basically I am looking for what is it that you goof up and you are out from the remaining process ? Are elimination rounds a fair way to judge a person ? Anyone can have a bad hour :-( Should you code the best possible or should you get the Algorithm right ? I generally first code a workable solution and then work on it till a level I think it looks beautiful to me. Is this a wrong approach ? Recently I had a telephonic interview in which I was asked to write a variation of Level Order traversal in 20 minutes. I could get the Algorithm and working code in 20 minutes but couldn't get the Exception handling and the coding convention right, after which I didn't hear back from them :-( All the other questions in the interview went very well this was the only thing which was 'not upto the mark'. Needless to say I like the company and will apply again but want to get it right the next time :-) Please share your experiences and valuable suggestions.

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  • Channelling an explosion along a narrow passage

    - by finnw
    I am simulating explosions in a 2D maze game. If an explosion occurs in an open area, it covers a circular region (this is the easy bit.) However if an explosion occurs in a narrow passage (i.e narrower than the blast range) then it should be "compressed", so that it goes further and also it should go around corners. Ultimately, unless it is completely boxed-in, then it should cover a constant number of pixels, spreading in whatever direction is necessary to reach this total area. I have tried using a shortest-path algorithm to pick the nearest N pixels to the origin avoiding walls, but the effect is exaggerated - the blast travels around corners too easily, making U-turns even when there is a clear path in another direction. I don't know whether this is realistic or not but it is counter-intuitive to players who assume that they can hide around a corner and the blast will take the path of least resistance in a different direction. Is there a well-known (and fast) algorithm for this?

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  • Storing documents in DMS

    - by Shaza
    I need your opinions and suggestions about storing documents in a DMS system. I think the DMS should save its own copies of the documents, not their original path on the disk. So, the DMS should have its own space to write on. But what about the way they're stored? Do they have their own extension different from the original one? What about the algorithm that stores them? What about the algorithm that retrieves them? What do you suggest??

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  • Looking for a non-cryptographic hash function that returns a single character

    - by makerofthings7
    Suppose I have a dictionary of ASCII words stored in uppercase. I also want to save those words into separate files so that the total word count of each file is approximately the same. By simply looking at the word I need to know which file it should be in (if it's there at all). Duplicate words should go into the same file and overwrite the last one. My first attempt at solving this problem is to use .NET's object.GetHashCode() function and .Trim() to get one of the "random" characters that pop up. I asked a similar question here If I only use one character of object.GetHashCode() I would get a hash code character of A..Z or 0..9. However saving the result of GetHashCode to disk is a no-no so I need a substitute. Question: What algorithm (or subset of an algorithm) is appropriate for pigeonholing strings into a single character or range of characters (Like hex 0..F offers 16 chars)? Real world usage: I'll use this answer to modify the Partition key used in Azure Table storage as described here

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  • Tiled perlin/value noise texture with (2^n)+1 size

    - by tobi
    Actually what I have in mind is value noise I think, but what I am going to ask applies to both of them. It is known that if you want to produce tiled texture by using the perlin/value noise, the size of the texture should be specified as the power of 2 (2^n). Without any modifications to the algorithm when you use the size of (2^n)+1 the texture cannot be tiled anymore, so I am wondering whether it is possible (by modifying the algorithm somehow) to generate such tiling texture with the size of (2^n)+1. The article (from which I have my implementation) is here: http://devmag.org.za/2009/04/25/perlin-noise/ I am aware that I can produce texture with 2^n size and just copy twice the last column/row from the ends to make it (2^n)+1, but I don't want to, because such repetitions are visible too much.

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  • Partitioning set into subsets with respect to equality of sum among subsets

    - by Al.Net
    let say i have {3, 1, 1, 2, 2, 1,5,2,7} set of numbers, I need to split the numbers such that sum of subset1 should be equal to sum of subset2 {3,2,7} {1,1,2,1,5,2}. First we should identify whether we can split number(one way might be dividable by 2 without any remainder) and if we can, we should write our algorithm two create s1 and s2 out of s. How to proceed with this approach? I read partition problem in wiki and even in some articles but i am not able to get anything. Can someone help me to find the right algorithm and its explanation in simple English?

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  • Is using build-in sorting considered cheating in practice tests?

    - by user10326
    I am using one of the practice online judges where a practice problem is asked and one submits the answer and gets back if it is accepted or not based on test inputs. My question is the following: In one of the practice tests, I needed to sort an array as part of the solution algorithm. If it matters the problem was: find 2 numbers in an array that add up to a specific target. As part of my algorithm I sorted the array, but to do that I used Java's quicksort and not implement sorting as part of the same method. To do that I had to do: java.util.Arrays.sort(array); Since I had to use the fully qualified name I am wondering if this is a kind of "cheating". (I mean perhaps an online judge does not expect this) Is it? In a formal interview (since these tests are practice for interview as I understand) would this be acceptable?

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  • Is there a 'design pattern' type listing of common algorithms?

    - by KevinM1
    Is there a 'design pattern' styled listing of common/popular algorithms anywhere? Specifically, something that has a similar format along the lines of: Algorithm Name: e.g., Quick Sort, Bubble Sort, etc. Problem: A description of the stereotypical problem the algorithm is supposed to address Description: Description of the solution Implementation: Code examples of the solution Big O Rating: Self-explanatory Similar Algorithms: Algorithms that address the same problem in different ways, or similar problems I really like the GoF design pattern listing style, and I think it would help me learn various algorithms better/easier if I could find a resource that was similar in terms of organization.

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  • Randomly spawning bitmaps on cnvas

    - by Toystoj
    I need some ideas in order to finish algorithm. I'm randomly placing objects (bitmaps) on canvas without overlapping. Time needed to finish it is my problem. When I need to spawn for example 80% of canvas it takes to long. So i was thinking : I should make some change when the bitmaps take off 50 % of canvas. I want to tell algorithm that it should generate new locations (x,y) where it is free space. My question is : How to render new location (x,y) in place where is free space. In summary: Things I know : object location (x,y) 4 corners (x,y) of object object width, height canvas width, height Any suggestions?

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  • Tiling Problem Solutions for Various Size "Dominoes"

    - by user67081
    I've got an interesting tiling problem, I have a large square image (size 128k so 131072 squares) with dimensons 256x512... I want to fill this image with certain grain types (a 1x1 tile, a 1x2 strip, a 2x1 strip, and 2x2 square) and have no overlap, no holes, and no extension past the image boundary. Given some probability for each of these grain types, a list of the number required to be placed is generated for each. Obviously an iterative/brute force method doesn't work well here if we just randomly place the pieces, instead a certain algorithm is required. 1) all 2x2 square grains are randomly placed until exhaustion. 2) 1x2 and 2x1 grains are randomly placed alternatively until exhaustion 3) the remaining 1x1 tiles are placed to fill in all holes. It turns out this algorithm works pretty well for some cases and has no problem filling the entire image, however as you might guess, increasing the probability (and thus number) of 1x2 and 2x1 grains eventually causes the placement to stall (since there are too many holes created by the strips and not all them can be placed). My approach to this solution has been as follows: 1) Create a mini-image of size 8x8 or 16x16. 2) Fill this image randomly and following the algorithm specified above so that the desired probability of the entire image is realized in the mini-image. 3) Create N of these mini-images and then randomly successively place them in the large image. Unfortunately there are some downfalls to this simplification. 1) given the small size of the mini-images, nailing an exact probability for the entire image is not possible. Example if I want p(2x1)=P(1x2)=0.4, the mini image may only give 0.41 as the closes probability. 2) The mini-images create a pseudo boundary where no overlaps occur which isn't really descriptive of the model this is being used for. 3) There is only a fixed number of mini-images so i'm not sure how random this really is. I'm really just looking to brainstorm about possible solutions to this. My main concern is really to nail down closer probabilities, now one might suggest I just increase the mini-image size. Well I have, and it turns out that in certain cases(p(1x2)=p(2x1)=0.5) the mini-image 16x16 isn't even iteratively solvable.. So it's pretty obvious how difficult it is to randomly solve this for anything greater than 8x8 sizes.. So I'd love to hear some ideas. Thanks

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  • Does Google counts backlinks from homepage to inside pages?

    - by SharkTheDark
    I have a site with good PR and my inside pages are getting increase of PR, but they don't have links pointing to them, only from my homepage. Does that means that Google counts ALL links on my homepage, including links to inside pages? Does it calculate inside pages PR with one coming from my domain, my homepage, too? Also, if inside pages that got high PR from homepage have link back to homepage, will that increase homepage PR additionally, since those links should count too? By Google PR algorithm formula, by calculations on Wikipedia and Stanford PR algorithm explanation ( which is originally developed by ) it counts those links, and also it counts after-increase backlink again, making few times circle ( it stops because of d ( 0.85 ) factor. ), but it counts them. Does anyone know is this correct?

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  • Effecient finding of long-range spotting targets

    - by nihohit
    I'm creating a top-down 2d strategy game, with a square grid map. So far, I've used Bresenham's line drawing algorithm in a circle to determine what's in LOS of each unit, and then targedt one of the targets in the circle. Now I find that this limits my units to shoot only at targets that they see. I want to extend my targeting algorithm to target any other unit in range of my weapon, even if they're out of sight range of this given unit, if they're "spotted" by another friendly unit. In other words, I want to enable usage of weapons with ranges longer than sight range. Is there a better way than iterating over all sighted units and computing range and LOSto each of them?

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  • Even distribution through a chain of resources

    - by ClosetGeek
    I'm working on an algorithm which routes tasks through a chain of distributed resources based on a hash (or random number). For example, say you have 10 gateways into a service which distribute tasks to 1000 handlers through 100 queues. 10,000 connected clients are expected to be connected to gateways at any given time (numbers are very general to keep it simple). Thats 10,000 clients 10 gateways (producers) 100 queues 1000 workers/handlers (consumers) The flow of each task is client-gateway-queue-worker Each client will have it's own hash/number which is used to route each task from the client to the same worker each time, with each task going through the same gateway and queue each time. Yet the algorithm handles distribution evenly, meaning each gateway, queue, and worker will have an even workload. My question is what exactly would this be called? Does such a thing already exist? This started off as a DHT, but I realized that DHTs can't do exactly what I need, so I started from scratch.

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  • Moving from an IT department to a proper technology company

    - by user2434
    I have been working with Java/web applications in an IT department of a retail company. As much as work goes, there is nothing much to say. Fixing couple of if/else loops, writing some simple business logic etc., is all what I have been doing. Having said that, I feel I have a good technical knowledge, and I am willing to move to companies like Microsoft/Google/Amazon etc., [I want to work in these places, because I feel I am a technical guy, and I am working in a place where most people freak out when the words like 'algorithm' are heard] I can of course prepare algorithms/computer science fundamentals etc.,(I hold a 4 year degree in computer science program) but beyond that, will my experience hold against me ? I doubt I'll even get a call from them seeing my work experience. What kind of questions(apart from the algorithm types) can I expect ?

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  • How to calculate shot angle and velocity to hit a moving target?

    - by Guen
    I am developing a 2D Android game and I am making an aiming algorithm for AI projectiles to hit enemies either following a path, or free moving. At the moment it just calculates where the target will be after a distance and fires a projectile to meet it at that distance. Of course this means varying the projectile speed to meet the target. Does anyone have any tips for a simple-ish algorithm (optimal-ish) to calculate when the projectile needs to fire and where it needs to aim if it can only travel at a constant velocity? Say the projectile goes twice the speed of the target? The only way I can think of involves searching and seems quite large.

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  • Consuming OData based Rest service in C# [en-US]

    - by ruimachado
    Nowadays comunication between applications is an active topic with daily usage and a large amount of pratical appliances. While developing an app in witch I had to consume an OData I found out that combining Linq with my code made this operation pretty easy.The algorithm to consume OData starts with adding a service reference to Visual Studio:After adding the service reference in wich you define the uri to the service, we start building our code.In your code the algorithm is the following:Define the Uri to your OData ServiceDefine the context of your odata, wich contains all entities exposed by the service.Query the context using LinqPrint the resultEasy and simple.Example code:01public static void Main(string[] args){02 03        Uri serviceUri= newUri("http://example.host.odataservice.net/service.svc", UriKind.Absolute);04        ODataService.ServiceEntities context = newODataService.ServiceEntities (serviceUri);05 06        context.Credentials = newSystem.Net.NetworkCredential(Username,Password);07 08         var query = from ServiceObject in context.YourEntity09                     select ServiceObject ;10 11        foreach (var myObject in query)12        {13            Console.WriteLine("\n Field1: {0} | Field2: {1}",14            myObject .Field1, myObject .Field2);15 16        }17}That’s it.Thank you,Rui Machadorpmachado.wordpress.com

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  • trying to use mod_proxy with httpd and tomcat

    - by techsjs2012
    I been trying to use mod_proxy with httpd and tomcat... I have on VirtualBox running Scientific Linux which has httpd and tomcat 6 on it.. I made two nodes of tomcat6. I followed this guide like 10 times and still cant get the 2nd node of tomcat working.. http://www.richardnichols.net/2010/08/5-minute-guide-clustering-apache-tomcat/ Here is the lines from my http.conf file <Proxy balancer://testcluster stickysession=JSESSIONID> BalancerMember ajp://127.0.0.1:8009 min=10 max=100 route=node1 loadfactor=1 BalancerMember ajp://127.0.0.1:8109 min=10 max=100 route=node2 loadfactor=1 </Proxy> ProxyPass /examples balancer://testcluster/examples <Location /balancer-manager> SetHandler balancer-manager AuthType Basic AuthName "Balancer Manager" AuthUserFile "/etc/httpd/conf/.htpasswd" Require valid-user </Location> Now here is my server.xml from node1 <?xml version='1.0' encoding='utf-8'?> <!-- Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to You under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. --> <!-- Note: A "Server" is not itself a "Container", so you may not define subcomponents such as "Valves" at this level. Documentation at /docs/config/server.html --> <Server port="8005" shutdown="SHUTDOWN"> <!--APR library loader. Documentation at /docs/apr.html --> <Listener className="org.apache.catalina.core.AprLifecycleListener" SSLEngine="on" /> <!--Initialize Jasper prior to webapps are loaded. Documentation at /docs/jasper-howto.html --> <Listener className="org.apache.catalina.core.JasperListener" /> <!-- Prevent memory leaks due to use of particular java/javax APIs--> <Listener className="org.apache.catalina.core.JreMemoryLeakPreventionListener" /> <!-- JMX Support for the Tomcat server. Documentation at /docs/non-existent.html --> <Listener className="org.apache.catalina.mbeans.ServerLifecycleListener" /> <Listener className="org.apache.catalina.mbeans.GlobalResourcesLifecycleListener" /> <!-- Global JNDI resources Documentation at /docs/jndi-resources-howto.html --> <GlobalNamingResources> <!-- Editable user database that can also be used by UserDatabaseRealm to authenticate users --> <Resource name="UserDatabase" auth="Container" type="org.apache.catalina.UserDatabase" description="User database that can be updated and saved" factory="org.apache.catalina.users.MemoryUserDatabaseFactory" pathname="conf/tomcat-users.xml" /> </GlobalNamingResources> <!-- A "Service" is a collection of one or more "Connectors" that share a single "Container" Note: A "Service" is not itself a "Container", so you may not define subcomponents such as "Valves" at this level. Documentation at /docs/config/service.html --> <Service name="Catalina"> <!--The connectors can use a shared executor, you can define one or more named thread pools--> <!-- <Executor name="tomcatThreadPool" namePrefix="catalina-exec-" maxThreads="150" minSpareThreads="4"/> --> <!-- A "Connector" represents an endpoint by which requests are received and responses are returned. Documentation at : Java HTTP Connector: /docs/config/http.html (blocking & non-blocking) Java AJP Connector: /docs/config/ajp.html APR (HTTP/AJP) Connector: /docs/apr.html Define a non-SSL HTTP/1.1 Connector on port 8080 <Connector port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" /> --> <!-- A "Connector" using the shared thread pool--> <!-- <Connector executor="tomcatThreadPool" port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" /> --> <!-- Define a SSL HTTP/1.1 Connector on port 8443 This connector uses the JSSE configuration, when using APR, the connector should be using the OpenSSL style configuration described in the APR documentation --> <!-- <Connector port="8443" protocol="HTTP/1.1" SSLEnabled="true" maxThreads="150" scheme="https" secure="true" clientAuth="false" sslProtocol="TLS" /> --> <!-- Define an AJP 1.3 Connector on port 8009 --> <Connector port="8009" protocol="AJP/1.3" redirectPort="8443" /> <!-- An Engine represents the entry point (within Catalina) that processes every request. The Engine implementation for Tomcat stand alone analyzes the HTTP headers included with the request, and passes them on to the appropriate Host (virtual host). Documentation at /docs/config/engine.html --> <!-- You should set jvmRoute to support load-balancing via AJP ie : <Engine name="Catalina" defaultHost="localhost" jvmRoute="jvm1"> --> <Engine name="Catalina" defaultHost="localhost" jvmRoute="node1"> <!--For clustering, please take a look at documentation at: /docs/cluster-howto.html (simple how to) /docs/config/cluster.html (reference documentation) --> <!-- <Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"/> --> <!-- The request dumper valve dumps useful debugging information about the request and response data received and sent by Tomcat. Documentation at: /docs/config/valve.html --> <!-- <Valve className="org.apache.catalina.valves.RequestDumperValve"/> --> <!-- This Realm uses the UserDatabase configured in the global JNDI resources under the key "UserDatabase". Any edits that are performed against this UserDatabase are immediately available for use by the Realm. --> <Realm className="org.apache.catalina.realm.UserDatabaseRealm" resourceName="UserDatabase"/> <!-- Define the default virtual host Note: XML Schema validation will not work with Xerces 2.2. --> <Host name="localhost" appBase="webapps" unpackWARs="true" autoDeploy="true" xmlValidation="false" xmlNamespaceAware="false"> <!-- SingleSignOn valve, share authentication between web applications Documentation at: /docs/config/valve.html --> <!-- <Valve className="org.apache.catalina.authenticator.SingleSignOn" /> --> <!-- Access log processes all example. Documentation at: /docs/config/valve.html --> <!-- <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs" prefix="localhost_access_log." suffix=".txt" pattern="common" resolveHosts="false"/> --> </Host> </Engine> </Service> </Server> now here is the server.xml file from node2 <?xml version='1.0' encoding='utf-8'?> <!-- Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to You under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. --> <!-- Note: A "Server" is not itself a "Container", so you may not define subcomponents such as "Valves" at this level. Documentation at /docs/config/server.html --> <Server port="8105" shutdown="SHUTDOWN"> <!--APR library loader. Documentation at /docs/apr.html --> <Listener className="org.apache.catalina.core.AprLifecycleListener" SSLEngine="on" /> <!--Initialize Jasper prior to webapps are loaded. Documentation at /docs/jasper-howto.html --> <Listener className="org.apache.catalina.core.JasperListener" /> <!-- Prevent memory leaks due to use of particular java/javax APIs--> <Listener className="org.apache.catalina.core.JreMemoryLeakPreventionListener" /> <!-- JMX Support for the Tomcat server. Documentation at /docs/non-existent.html --> <Listener className="org.apache.catalina.mbeans.ServerLifecycleListener" /> <Listener className="org.apache.catalina.mbeans.GlobalResourcesLifecycleListener" /> <!-- Global JNDI resources Documentation at /docs/jndi-resources-howto.html --> <GlobalNamingResources> <!-- Editable user database that can also be used by UserDatabaseRealm to authenticate users --> <Resource name="UserDatabase" auth="Container" type="org.apache.catalina.UserDatabase" description="User database that can be updated and saved" factory="org.apache.catalina.users.MemoryUserDatabaseFactory" pathname="conf/tomcat-users.xml" /> </GlobalNamingResources> <!-- A "Service" is a collection of one or more "Connectors" that share a single "Container" Note: A "Service" is not itself a "Container", so you may not define subcomponents such as "Valves" at this level. Documentation at /docs/config/service.html --> <Service name="Catalina"> <!--The connectors can use a shared executor, you can define one or more named thread pools--> <!-- <Executor name="tomcatThreadPool" namePrefix="catalina-exec-" maxThreads="150" minSpareThreads="4"/> --> <!-- A "Connector" represents an endpoint by which requests are received and responses are returned. Documentation at : Java HTTP Connector: /docs/config/http.html (blocking & non-blocking) Java AJP Connector: /docs/config/ajp.html APR (HTTP/AJP) Connector: /docs/apr.html Define a non-SSL HTTP/1.1 Connector on port 8080 <Connector port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" /> --> <!-- A "Connector" using the shared thread pool--> <!-- <Connector executor="tomcatThreadPool" port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" /> --> <!-- Define a SSL HTTP/1.1 Connector on port 8443 This connector uses the JSSE configuration, when using APR, the connector should be using the OpenSSL style configuration described in the APR documentation --> <!-- <Connector port="8443" protocol="HTTP/1.1" SSLEnabled="true" maxThreads="150" scheme="https" secure="true" clientAuth="false" sslProtocol="TLS" /> --> <!-- Define an AJP 1.3 Connector on port 8009 --> <Connector port="8109" protocol="AJP/1.3" redirectPort="8443" /> <!-- An Engine represents the entry point (within Catalina) that processes every request. The Engine implementation for Tomcat stand alone analyzes the HTTP headers included with the request, and passes them on to the appropriate Host (virtual host). Documentation at /docs/config/engine.html --> <!-- You should set jvmRoute to support load-balancing via AJP ie : <Engine name="Catalina" defaultHost="localhost" jvmRoute="jvm1"> --> <Engine name="Catalina" defaultHost="localhost" jvmRoute="node2"> <!--For clustering, please take a look at documentation at: /docs/cluster-howto.html (simple how to) /docs/config/cluster.html (reference documentation) --> <!-- <Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"/> --> <!-- The request dumper valve dumps useful debugging information about the request and response data received and sent by Tomcat. Documentation at: /docs/config/valve.html --> <!-- <Valve className="org.apache.catalina.valves.RequestDumperValve"/> --> <!-- This Realm uses the UserDatabase configured in the global JNDI resources under the key "UserDatabase". Any edits that are performed against this UserDatabase are immediately available for use by the Realm. --> <Realm className="org.apache.catalina.realm.UserDatabaseRealm" resourceName="UserDatabase"/> <!-- Define the default virtual host Note: XML Schema validation will not work with Xerces 2.2. --> <Host name="localhost" appBase="webapps" unpackWARs="true" autoDeploy="true" xmlValidation="false" xmlNamespaceAware="false"> <!-- SingleSignOn valve, share authentication between web applications Documentation at: /docs/config/valve.html --> <!-- <Valve className="org.apache.catalina.authenticator.SingleSignOn" /> --> <!-- Access log processes all example. Documentation at: /docs/config/valve.html --> <!-- <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs" prefix="localhost_access_log." suffix=".txt" pattern="common" resolveHosts="false"/> --> </Host> </Engine> </Service> </Server> I dont know what it is. but I been trying for days

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  • A Guide to Fusion SCM at Oracle OpenWorld 2012

    - by Pam Petropoulos
    Are you attending next week’s Oracle OpenWorld 2012 conference? Then you won’t want to miss the Fusion SCM activities and customer presenters from leading companies like Boeing and Fideltronik. Below you’ll find a day by day guide of the various Fusion SCM sessions, demos and activities during OpenWorld 2012, September 30 – October 4 in San Francisco, CA. Tuesday, October 2 All of the Fusion SCM sessions during OpenWorld will take place in various rooms at Moscone West, a convenience you are sure to appreciate, as will your feet.   The first session at 10:15 – 11:15 am (Moscone West, Room 2006), entitled “Oracle Fusion Supply Chain Management: Overview, Strategy, Customer Experiences, and Roadmap”, provides an overview of Fusion Supply Chain Management applications and will discuss Fusion SCM strategy, future roadmap, and highlights of customer examples. The next session at 11:45 am – 12:45 pm (Moscone West, Room 2022), entitled “Enabling Trusted Enterprise Product Data with Oracle Fusion Product Hub”, may be the session for you if you’re struggling with achieving consistent, high-quality product data that provides significant business value. This session will discuss how Oracle Fusion Product Hub and Oracle Enterprise Data Quality can help you to achieve this vision. A customer presenter from Fideltronik will share their experiences with Oracle Fusion Product Hub. At the end of the day unwind at the Supply Chain Management customer reception from 6:00 – 8:00 pm at the Roe Lounge, located at 651 Howard Street. Registration is required. Click here for details. Wednesday, October 3 Wednesday is a busy day with three Fusion SCM sessions on the agenda. Start your day at 10:15 am at the “Oracle Fusion Supply Chain Management: Customer Adoption and Experiences” session (Moscone West, Room 2003).  This must see session will showcase customer speakers from The Boeing Company and Fideltronik, each of whom will share their company’s experiences in selecting and implementing Fusion SCM applications. If you’re wondering how Fusion SCM applications can co-exist with your existing Oracle applications, then you’ll want to sit in on the 3:30 pm session entitled “Oracle Fusion Supply Chain Management: Coexistence with Other Oracle Applications” (Moscone West, Room 2003). Stick around until 5:00 pm for the final Fusion SCM session of the day entitled “Responsive Fulfillment with Oracle Fusion Supply Chain Management” (Moscone West, Room 2001).  This session will showcase Oracle Fusion Distributed Order Orchestration and Oracle Fusion Global Order Promising and how they are changing the way companies manage order fulfillment in environments. In addition to discussing the current business challenges, product capabilities, value propositions, industry applicability, and future roadmap this session will also feature a customer presenter from The Boeing Company. Thursday, October 4 If you are a retail customer we highly recommend that you attend the final Fusion SCM session of the week at 12:45 pm, entitled “Multichannel Fulfillment Excellence in the Direct-to-Consumer Market” (Moscone West, Room 2024).  Retailers will learn how they can transform their supply chains to meet the ever-increasing demands of buy anywhere/get anywhere cross-channel requirements with Fusion Distributed Order Orchestration and Oracle Fusion Product Hub. Throughout the week, you’ll also want to visit the Fusion SCM demo pods at the Demogrounds in Moscone West so you can see demos of these Fusion applications. Visit pod W-005 for Fusion Distributed Order Orchestration, W-008 for Fusion Inventory and Cost Management, and W-006 for Fusion Product Hub. Click here for the Demogrounds map. A reminder that you can also pre-register for these sessions to secure your spot. Visit the Schedule Builder to pre-enroll for these sessions. Finally, you'll also want to check out the Fusion SCM FocusOn document which includes additional keynote and general sessions that you may want to attend throughout the week.   We look forward to seeing you in San Francisco next week.

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  • Big Data – Interacting with Hadoop – What is Sqoop? – What is Zookeeper? – Day 17 of 21

    - by Pinal Dave
    In yesterday’s blog post we learned the importance of the Pig and Pig Latin in Big Data Story. In this article we will understand what is Sqoop and Zookeeper in Big Data Story. There are two most important components one should learn when learning about interacting with Hadoop – Sqoop and Zookper. What is Sqoop? Most of the business stores their data in RDBMS as well as other data warehouse solutions. They need a way to move data to the Hadoop system to do various processing and return it back to RDBMS from Hadoop system. The data movement can happen in real time or at various intervals in bulk. We need a tool which can help us move this data from SQL to Hadoop and from Hadoop to SQL. Sqoop (SQL to Hadoop) is such a tool which extract data from non-Hadoop data sources and transform them into the format which Hadoop can use it and later it loads them into HDFS. Essentially it is ETL tool where it Extracts, Transform and Load from SQL to Hadoop. The best part is that it also does extract data from Hadoop and loads them to Non-SQL (or RDBMS) data stores. Essentially, Sqoop is a command line tool which does SQL to Hadoop and Hadoop to SQL. It is a command line interpreter. It creates MapReduce job behinds the scene to import data from an external database to HDFS. It is very effective and easy to learn tool for nonprogrammers. What is Zookeeper? ZooKeeper is a centralized service for maintaining configuration information, naming, providing distributed synchronization, and providing group services. In other words Zookeeper is a replicated synchronization service with eventual consistency. In simpler words – in Hadoop cluster there are many different nodes and one node is master. Let us assume that master node fails due to any reason. In this case, the role of the master node has to be transferred to a different node. The main role of the master node is managing the writers as that task requires persistence in order of writing. In this kind of scenario Zookeeper will assign new master node and make sure that Hadoop cluster performs without any glitch. Zookeeper is the Hadoop’s method of coordinating all the elements of these distributed systems. Here are few of the tasks which Zookeepr is responsible for. Zookeeper manages the entire workflow of starting and stopping various nodes in the Hadoop’s cluster. In Hadoop cluster when any processes need certain configuration to complete the task. Zookeeper makes sure that certain node gets necessary configuration consistently. In case of the master node fails, Zookeepr can assign new master node and make sure cluster works as expected. There many other tasks Zookeeper performance when it is about Hadoop cluster and communication. Basically without the help of Zookeeper it is not possible to design any new fault tolerant distributed application. Tomorrow In tomorrow’s blog post we will discuss about very important components of the Big Data Ecosystem – Big Data Analytics. 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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  • What do you need to know to be a world-class master software developer? [closed]

    - by glitch
    I wanted to bring up this question to you folks and see what you think, hopefully advise me on the matter: let's say you had 30 years of learning and practicing software development in front of you, how would you dedicate your time so that you'd get the biggest bang for your buck. What would you both learn and work on to be a world-class software developer that would make a large impact on the industry and leave behind a legacy? I think that most great developers end up being both broad generalists and specialists in one-two areas of interest. I'm thinking Bill Joy, John Carmack, Linus Torvalds, K&R and so on. I'm thinking that perhaps one approach would be to break things down by categories and establish a base minimum of "software development" greatness. I'm thinking: Operating Systems: completely internalize the core concepts of OS, perhaps gain a lot of familiarity with an OSS one such as Linux. Anything from memory management to device drivers has to be complete second nature. Programming Languages: this is one of those topics that imho has to be fully grokked even if it might take many years. I don't think there's quite anything like going through the process of developing your own compiler, understanding language design trade-offs and so on. Programming Language Pragmatics is one of my favorite books actually, I think you want to have that internalized back to back, and that's just the start. You could go significantly deeper, but I think it's time well spent, because it's such a crucial building block. As a subset of that, you want to really understand the different programming paradigms out there. Imperative, declarative, logic, functional and so on. Anything from assembly to LISP should be at the very least comfortable to write in. Contexts: I believe one should have experience working in different contexts to truly be able to appreciate the trade-offs that are being made every day. Embedded, web development, mobile development, UX development, distributed, cloud computing and so on. Hardware: I'm somewhat conflicted about this one. I think you want some understanding of computer architecture at a low level, but I feel like the concepts that will truly matter will be slightly higher level, such as CPU caching / memory hierarchy, ILP, and so on. Networking: we live in a completely network-dependent era. Having a good understanding of the OSI model, knowing how the Web works, how HTTP works and so on is pretty much a pre-requisite these days. Distributed systems: once again, everything's distributed these days, it's getting progressively harder to ignore this reality. Slightly related, perhaps add solid understanding of how browsers work to that, since the world seems to be moving so much to interfacing with everything through a browser. Tools: Have a really broad toolset that you're familiar with, one that continuously expands throughout the years. Communication: I think being a great writer, effective communicator and a phenomenal team player is pretty much a prerequisite for a lot of a software developer's greatness. It can't be overstated. Software engineering: understanding the process of building software, team dynamics, the requirements of the business-side, all the pitfalls. You want to deeply understand where what you're writing fits from the market perspective. The better you understand all of this, the more of your work will actually see the daylight. This is really just a starting list, I'm confident that there's a ton of other material that you need to master. As I mentioned, you most likely end up specializing in a bunch of these areas as you go along, but I was trying to come up with a baseline. Any thoughts, suggestions and words of wisdom from the grizzled veterans out there who would like to share their thoughts and experiences with this? I'd really love to know what you think!

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  • mysqld causes high CPU load

    - by Radu
    My mysqld goes to use 99.9% of CPU for variable time (between 2 - 20 minutes), and then goes back to normal 0.1% - 5%. Checked processlist: all is normal, 1 to 20 inserts or updates that last 2 to 5 sec, and about 20 process that are in Sleep Mode (maybe because the scripts don't close the mysql connection, but are they are closed in about 5 - 10 secs, I didn't make the scripts :P but the server was running fine the last 2 years, since is was made): | 15375 | root | localhost | stoc | Query | 0 | NULL | show processlist | | 79480 | pppoe | localhost | pppoe | Sleep | 4 | NULL | NULL | | 79481 | pppoe | localhost | pppoe | Sleep | 4 | NULL | NULL | | 79482 | pppoe | localhost | pppoe | Sleep | 4 | NULL | NULL | | 79483 | pppoe | localhost | pppoe | Query | 0 | init | UPDATE acc SET InputOctets="0", OutputOctets="0", InputPackets="unknown", OutputPackets="User | | 79484 | pppoe | localhost | pppoe | Sleep | 5 | NULL | NULL | | 79485 | pppoe | localhost | pppoe | Sleep | 5 | NULL | NULL | | 79486 | pppoe | localhost | pppoe | Sleep | 5 | NULL | NULL Checked raid, seemns OK: [root@db2]# cat /proc/mdstat Personalities : [raid5] [raid4] [raid1] md0 : active raid1 sdd1[3] sdc1[2] sdb1[0] sda1[1] 136448 blocks [4/4] [UUUU] md1 : active raid5 sdd2[3] sdc2[2] sdb2[0] sda2[1] 12023808 blocks level 5, 256k chunk, algorithm 2 [4/4] [UUUU] md3 : active raid5 sda4[1] sdd4[3] sdc4[2] sdb4[0] 203647488 blocks level 5, 256k chunk, algorithm 2 [4/4] [UUUU] md2 : active raid5 sda3[1] sdd3[3] sdc3[2] sdb3[0] 24024576 blocks level 5, 256k chunk, algorithm 2 [4/4] [UUUU] unused devices: <none> [root@db2]# top sees my mysqld cpu load, but nothing else seems to be wrong: [root@db2]# top top - 17:56:05 up 7 days, 3:55, 3 users, load average: 32.93, 24.72, 22.70 Tasks: 75 total, 4 running, 71 sleeping, 0 stopped, 0 zombie Cpu(s): 63.4% us, 36.6% sy, 0.0% ni, 0.0% id, 0.0% wa, 0.0% hi, 0.0% si, 0.0% st Mem: 1988824k total, 1304776k used, 684048k free, 99588k buffers Swap: 12023800k total, 0k used, 12023800k free, 951028k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 5754 mysql 19 0 236m 57m 5108 R 99.9 2.9 21:58.76 mysqld 1 root 16 0 7216 700 580 S 0.0 0.0 0:00.39 init 2 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/0 Repaired all mysql databases, reindexed raid ... I'm running out of ideeas ... Anyone has an ideea what can go wrong with this server ? Thank you

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