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  • What is the better design decision approach?

    - by palm snow
    I have two classes (MyFoo1 and MyFoo2) that share some common functionality. So far it does not seem like I need any polymorphic inheritence but at this point I am considering the following options: Have the common functionality in a utility class. Both of these classes call these methods from that utility class. Have an abstract class and implement common methods in that abstract class. Then derive MyFoo1 and MyFoo2 from that abstract class. Any suggestion on what would be a better design decision?

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  • design for interruptable operations

    - by tpaksu
    I couldn't find a better topic but here it is; 1) When user clicks a button, code starts t work, 2) When another button is clicked, it would stop doing whatever it does and start to run the second button's code, 3) Or with not user interaction, an electrical power down detected from a connected device, so our software would cancel the current event and start doing the power down procedure. How is this design mostly applied to code? I mean "stop what you are doing" part? If you would say events, event handlers etc. how do you bind a condition to the event? and how do you tell the program without using laddered if's to end it's process? method1(); if (powerdown) return; method2(); if (powerdown) return; etc.

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  • Business Layer Design in J2EE Project

    - by user63157
    Currently the project on which I am working is being developed with Spring, Hibernate and struts. The business layer consists of simple java beans with no behavior in them only properties and getter and setter methods, the services are written on them which operates on them and call DAO layer methods and all. My questions is that is it object oriented way of designing or simply the procedure way in which the data and the functions on which they operate are not together. Please provide your thoughts and inputs on how the business logic is design and implemented in j2ee application, is the domain model contains business methods or are they simply dumb objects which have only data and services written on to them.

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  • Differentiate VMware network adapter from physical network adapters

    - by Venkat
    I have to differentiate between the real addresses and the VM addresses using any Windows API. I'm using Getadaptersaddresses API to populate a list of ipaddresses for the local machine. I need to extract only the "real" addresses apart from the addresses associated with the VMware network adapter and other addresses(auto-configuration and tunnel adapter addresses) I've not been able to find any API or any flag to differentiate this. Is there any way this can be done? PS:The IfType flag in the IP_ADAPTER_ADDRESSES structure returned by Getadaptersaddresses doesn't help me differentiate between VMware addresses and the real addresses

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  • Cleanest RESTful design for purely "action" calls?

    - by Josh Handel
    Hello all, I am sticking my toe in the RESTful waters and I just can't find a "satisfactory" solution to how to handle truely "action" oriented calls on a RESTful service? My quandry can be broken down into two parts. 1) Transactional calls: I understand the idea of having an ActionTransactor that you get a resource too with a post, update the parameters and then commit with a PUT (as described all over the place and in the Orilly RESTful Web services book).. But I struggle with the idea of keeping URLs with states present for ever.. If we really honestly don't need to keep a transaction for ever can we kill the resource URI? do URIs need to be perminate or can they be transiant URIs that expire 2) Non transactional calls: these might be calls to perform some workflow that spans multiple resources but having a resource just doesn't make since.. An example might be to re-generating some calculated ans cached value like a large aggreget or re-indexing blog or some such "purely" action. Anyways, I'm curious about the communities thoughts on this... Thus far, I've read that Overloading Post is the cleanest way to handle part 2.. But there is an equal amount of argument against that approach as well. And (to me) its not self documenting which I though was one of the key design goals of RESTful APIs.

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  • Design considerations for temporarily transforming a player into an animal in a role playing game

    - by mikedev
    I am working on a role playing game for fun and to practice design patterns. I would like players to be able to transform themselves into different animals. For example, a Druid might be able to shape shift into a cheetah. Right now I'm planning on using the decorator pattern to do this but my question is - how do I make it so that when a druid is in the cheetah form, they can only access skills for the cheetah? In other words, they should not be able to access their normal Druid skills. Using the decorator pattern it appears that even in the cheetah form my druid will be able to access their normal druid skills. class Druid : Character { // many cool druid skills and spells void LightHeal(Character target) { } } abstract class CharacterDecorator : Character { Character DecoratedCharacter; } class CheetahForm : CharacterDecorator { Character DecoratedCharacter; public CheetahForm(Character decoratedCharacter) { DecoratedCharacter= decoratedCharacter; } // many cool cheetah related skills void CheetahRun() { // let player move very fast } } now using the classes Druid myDruid = new Druid(); myDruid.LightHeal(myDruid); // casting light heal here is fine myDruid = new CheetahForm(myDruid); myDruid.LightHeal(myDruid); // casting here should not be allowed Hmmmm...now that I think about it, will myDruid be unable to us the Druid class spells/skills unless the class is down-casted? But even if that's the case, is there a better way to ensure that myDruid at this point is locked out from all Druid related spells/skills until it is cast back to a Druid (since currently it's in CheetahForm)

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  • What is the best software design to use in this scenario

    - by domdefelice
    I need to generate HTML snippets using jQuery. The creation of those snippets depends on some data. The data is stored server-side, in session (where PHP is used). At the moment I achieved this - retrieving the data from the server via AJAX in form of JSON - and building the snippets via specific javascript functions that read those data The problem is that the complexity of the data is getting bigger and hence the serialization into JSON is getting even more difficult since I can't do it automatically. I can't do it automatically because some information are sensible so I generate a "stripped" version to send to the client. I know it is difficult to understand without any code to read, but I am hoping this is a common scenario and would be glad for any tip, suggestion or even design-pattern you can give me. Should I store both a complete and a stripped data on the server and then use some library to automatically generate the JSON from the stripped data? But this also means I have to get the two data synchronized. Or maybe I could move the logic server-side, this way avoiding sending the data. But this means sending javascript code (since I rely on jQuery). Maybe not a good idea. Feel free to ask me more details if this is not clear. Thank you for any help

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  • Ruby and duck typing: design by contract impossible?

    - by davetron5000
    Method signature in Java: public List<String> getFilesIn(List<File> directories) similar one in ruby def get_files_in(directories) In the case of Java, the type system gives me information about what the method expects and delivers. In Ruby's case, I have no clue what I'm supposed to pass in, or what I'll expect to receive. In Java, the object must formally implement the interface. In Ruby, the object being passed in must respond to whatever methods are called in the method defined here. This seems highly problematic: Even with 100% accurate, up-to-date documentation, the Ruby code has to essentially expose its implementation, breaking encapsulation. "OO purity" aside, this would seem to be a maintenance nightmare. The Ruby code gives me no clue what's being returned; I would have to essentially experiment, or read the code to find out what methods the returned object would respond to. Not looking to debate static typing vs duck typing, but looking to understand how you maintain a production system where you have almost no ability to design by contract. Update No one has really addressed the exposure of a method's internal implementation via documentation that this approach requires. Since there are no interfaces, if I'm not expecting a particular type, don't I have to itemize every method I might call so that the caller knows what can be passed in? Or is this just an edge case that doesn't really come up?

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  • Implementation/interface inheritance design question.

    - by Neil G
    I would like to get the stackoverflow community's opinion on the following three design patterns. The first is implementation inheritance; the second is interface inheritance; the third is a middle ground. My specific question is: Which is best? implementation inheritance: class Base { X x() const = 0; void UpdateX(A a) { y_ = g(a); } Y y_; } class Derived: Base { X x() const { return f(y_); } } interface inheritance: class Base { X x() const = 0; void UpdateX(A a) = 0; } class Derived: Base { X x() const { return x_; } void UpdateX(A a) { x_ = f(g(a)); } X x_; } middle ground: class Base { X x() const { return x_; } void UpdateX(A a) = 0; X x_; } class Derived: Base { void UpdateX(A a) { x_ = f(g(a)); } } I know that many people prefer interface inheritance to implementation inheritance. However, the advantage of the latter is that with a pointer to Base, x() can be inlined and the address of x_ can be statically calculated.

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  • Social Media Java Design Problem

    - by jboyd
    I need to put something together quickly that will take blog posts and place them on social media sites, the requirements are as follows: Blog Entries are independent records that already exist, they have a published date and a modified date, the blog entry application cannot be changed, at least not substantially A new blog entry, or update needs to be sent to social media sites I currently do not need to update or delete social media communications if the blog entry is edited, or deleted, though I may need to later My design problems here are as follows: how do I know the status of each update how can I figure out what blog entry updates and postings have already been sent out? how can I quickly poll the blog entry table for postings that haven't yet been sent out? Avoiding looking at each Entry record from the DB as an object and asking if it's been sent already. That would be too slow. I cannot hook into any Blog Entry update code, my only option would be to create a trigger that an update queues something to be processed I'm looking for general guiding principles here, the biggest problem I'm having is coming up with any reasonable way to figure out if a blog entry should be sent to our social media sites in the first place

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  • Issue with class design to model user preferences for different classes

    - by Mulone
    Hi all, I'm not sure how to design a couple of classes in my app. Basically that's a situation: each user can have many preferences each preference can be referred to an object of different classes (e.g. album, film, book etc) the preference is expressed as a set of values (e.g. score, etc). The problem is that many users can have preferences on the same objects, e.g.: John: score=5 for filmid=apocalypsenow Paul: score=3 for filmid=apocalypsenow And naturally I don't want to duplicate the object film in each user. So I could create a class called "preference" holding a score and then a target object, something like: User{ hasMany preferences } Preference{ belongsTo User double score Film target Album target //etc } and then define just one target. Then I would create an interface for the target Classes (album, film etc): Interface canBePreferred{ hasMany preferences } And implement all of those classes. This could work, but it looks pretty ugly and it would requires a lot of joins to work. Do you have some patterns I could use to model this nicely? Cheers, Mulone

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  • Abstract Design Pattern implementation

    - by Pathachiever11
    I started learning design patterns a while ago (only covered facade and abstract so far, but am enjoying it). I'm looking to apply the Abstract pattern to a problem I have. The problem is: Supporting various Database systems using one abstract class and a set of methods and properties, which then the underlying concrete classes (inheriting from abstract class) would be implementing. I have created a DatabaseWrapper abstract class and have create SqlClientData and MSAccessData concrete class that inherit from the DatabaseWrapper. However, I'm still a bit confused about how the pattern goes as far as implementing these classes on the Client. Would I do the following?: DatabaseWrapper sqlClient = new SqlClientData(connectionString); This is what I saw in an example, but that is not what I'm looking for because I want to encapsulate the concrete classes; I only want the Client to use the abstract class. This is so I can support for more database systems in the future with minimal changes to the Client, and creating a new concrete class for the implementations. I'm still learning, so there might be a lot of things wrong here. Please tell me how I can encapsulate all the concrete classes, and if there is anything wrong with my approach. Many Thanks! PS: I'm very excited to get into software architecture, but still am a beginner, so take it easy on me. :)

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  • Network Logon Issues with Group Policy and Network

    - by bobloki
    I am gravely in need of your help and assistance. We have a problem with our logon and startup to our Windows 7 Enterprise system. We have more than 3000 Windows Desktops situated in roughly 20+ buildings around campus. Almost every computer on campus has the problem that I will be describing. I have spent over one month peering over etl files from Windows Performance Analyzer (A great product) and hundreds of thousands of event logs. I come to you today humbled that I could not figure this out. The problem as simply put our logon times are extremely long. An average first time logon is roughly 2-10 minutes depending on the software installed. All computers are Windows 7, the oldest computers being 5 years old. Startup times on various computers range from good (1-2 minutes) to very bad (5-60). Our second time logons range from 30 seconds to 4 minutes. We have a gigabit connection between each computer on the network. We have 5 domain controllers which also double as our DNS servers. Initial testing led us to believe that this was a software problem. So I spent a few days testing machines only to find inconsistent results from the etl files from xperfview. Each subset of computers on campus had a different subset of software issues, none seeming to interfere with logon just startup. So I started looking at our group policy and located some very interesting event ID’s. Group Policy 1129: The processing of Group Policy failed because of lack of network connectivity to a domain controller. Group Policy 1055: The processing of Group Policy failed. Windows could not resolve the computer name. This could be caused by one of more of the following: a) Name Resolution failure on the current domain controller. b) Active Directory Replication Latency (an account created on another domain controller has not replicated to the current domain controller). NETLOGON 5719 : This computer was not able to set up a secure session with a domain controller in domain OURDOMAIN due to the following: There are currently no logon servers available to service the logon request. This may lead to authentication problems. Make sure that this computer is connected to the network. If the problem persists, please contact your domain administrator. E1kexpress 27: Intel®82567LM-3 Gigabit Network Connection – Network link is disconnected. NetBT 4300 – The driver could not be created. WMI 10 - Event filter with query "SELECT * FROM __InstanceModificationEvent WITHIN 60 WHERE TargetInstance ISA "Win32_Processor" AND TargetInstance.LoadPercentage 99" could not be reactivated in namespace "//./root/CIMV2" because of error 0x80041003. Events cannot be delivered through this filter until the problem is corrected. More or less with timestamps it becomes apparent that the network maybe the issue. 1:25:57 - Group Policy is trying to discover the domain controller information 1:25:57 - The network link has been disconnected 1:25:58 - The processing of Group Policy failed because of lack of network connectivity to a domain controller. This may be a transient condition. A success message would be generated once the machine gets connected to the domain controller and Group Policy has successfully processed. If you do not see a success message for several hours, then contact your administrator. 1:25:58 - Making LDAP calls to connect and bind to active directory. DC1.ourdomain.edu 1:25:58 - Call failed after 0 milliseconds. 1:25:58 - Forcing rediscovery of domain controller details. 1:25:58 - Group policy failed to discover the domain controller in 1030 milliseconds 1:25:58 - Periodic policy processing failed for computer OURDOMAIN\%name%$ in 1 seconds. 1:25:59 - A network link has been established at 1Gbps at full duplex 1:26:00 - The network link has been disconnected 1:26:02 - NtpClient was unable to set a domain peer to use as a time source because of discovery error. NtpClient will try again in 3473457 minutes and DOUBLE THE REATTEMPT INTERVAL thereafter. 1:26:05 - A network link has been established at 1Gbps at full duplex 1:26:08 - Name resolution for the name %Name% timed out after none of the configured DNS servers responded. 1:26:10 – The TCP/IP NetBIOS Helper service entered the running state. 1:26:11 - The time provider NtpClient is currently receiving valid time data at dc4.ourdomain.edu 1:26:14 – User Logon Notification for Customer Experience Improvement Program 1:26:15 - Group Policy received the notification Logon from Winlogon for session 1. 1:26:15 - Making LDAP calls to connect and bind to Active Directory. dc4.ourdomain.edu 1:26:18 - The LDAP call to connect and bind to Active Directory completed. dc4. ourdomain.edu. The call completed in 2309 milliseconds. 1:26:18 - Group Policy successfully discovered the Domain Controller in 2918 milliseconds. 1:26:18 - Computer details: Computer role : 2 Network name : (Blank) 1:26:18 - The LDAP call to connect and bind to Active Directory completed. dc4.ourdomain.edu. The call completed in 2309 milliseconds. 1:26:18 - Group Policy successfully discovered the Domain Controller in 2918 milliseconds. 1:26:19 - The WinHTTP Web Proxy Auto-Discovery Service service entered the running state. 1:26:46 - The Network Connections service entered the running state. 1:27:10 – Retrieved account information 1:27:10 – The system call to get account information completed. 1:27:10 - Starting policy processing due to network state change for computer OURDOMAIN\%name%$ 1:27:10 – Network state change detected 1:27:10 - Making system call to get account information. 1:27:11 - Making LDAP calls to connect and bind to Active Directory. dc4.ourdomain.edu 1:27:13 - Computer details: Computer role : 2 Network name : ourdomain.edu (Now not blank) 1:27:13 - Group Policy successfully discovered the Domain Controller in 2886 milliseconds. 1:27:13 - The LDAP call to connect and bind to Active Directory completed. dc4.ourdomain.edu The call completed in 2371 milliseconds. 1:27:15 - Estimated network bandwidth on one of the connections: 0 kbps. 1:27:15 - Estimated network bandwidth on one of the connections: 8545 kbps. 1:27:15 - A fast link was detected. The Estimated bandwidth is 8545 kbps. The slow link threshold is 500 kbps. 1:27:17 – Powershell - Engine state is changed from Available to Stopped. 1:27:20 - Completed Group Policy Local Users and Groups Extension Processing in 4539 milliseconds. 1:27:25 - Completed Group Policy Scheduled Tasks Extension Processing in 5210 milliseconds. 1:27:27 - Completed Group Policy Registry Extension Processing in 1529 milliseconds. 1:27:27 - Completed policy processing due to network state change for computer OURDOMAIN\%name%$ in 16 seconds. 1:27:27 – The Group Policy settings for the computer were processed successfully. There were no changes detected since the last successful processing of Group Policy. Any help would be appreciated. Please ask for any relevant information and it will be provided as soon as possible.

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  • Finding most efficient transmission size in varying network latency scenarios

    - by rwmnau
    I'm building a .NET remoting client/server that will be transmitting thousands of files, of varying sizes (everything from a few bytes to hundreds of MB), and I'm curious about a general method for finding the appropriate transmission size. As I see it, there's the following tradeoff: Serialize entire file into a transmission object and transmit at once, regardless of size. This would be the fastest, but a failure during tranmission requires that the whole file be re-transmitted. If the file size is larger than something small (like 4KB), break it into 4KB chunks and transmit those, re-assembling on the server. In addition to the complexity of this, it's slower because of continued round-trips and acknowledgements, though a failure of any one piece doesn't waste much time. The ideal transmission method (when taking into account negotiation latency vs. failure rate) is somewhere in between, and I'm wondering about how to find out the best size for that particular client. Do I have some dynamic tuning step in my transmission that looks at the current bytes/second average, and then raises the transmission size until the speed starts to drop (failures overwhelm negotiation cost)? Or is there some other method for determining ideal transmission size? The application will be multi-threaded, so number of threads also factors in to the calculation. I'm not looking for a formula (though I'll take one if you've got it), but just what to consider as I create this process.

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  • Network Logon Issues with Group Policy and Network

    - by bobloki
    I am gravely in need of your help and assistance. We have a problem with our logon and startup to our Windows 7 Enterprise system. We have more than 3000 Windows Desktops situated in roughly 20+ buildings around campus. Almost every computer on campus has the problem that I will be describing. I have spent over one month peering over etl files from Windows Performance Analyzer (A great product) and hundreds of thousands of event logs. I come to you today humbled that I could not figure this out. The problem as simply put our logon times are extremely long. An average first time logon is roughly 2-10 minutes depending on the software installed. All computers are Windows 7, the oldest computers being 5 years old. Startup times on various computers range from good (1-2 minutes) to very bad (5-60). Our second time logons range from 30 seconds to 4 minutes. We have a gigabit connection between each computer on the network. We have 5 domain controllers which also double as our DNS servers. Initial testing led us to believe that this was a software problem. So I spent a few days testing machines only to find inconsistent results from the etl files from xperfview. Each subset of computers on campus had a different subset of software issues, none seeming to interfere with logon just startup. So I started looking at our group policy and located some very interesting event ID’s. Group Policy 1129: The processing of Group Policy failed because of lack of network connectivity to a domain controller. Group Policy 1055: The processing of Group Policy failed. Windows could not resolve the computer name. This could be caused by one of more of the following: a) Name Resolution failure on the current domain controller. b) Active Directory Replication Latency (an account created on another domain controller has not replicated to the current domain controller). NETLOGON 5719 : This computer was not able to set up a secure session with a domain controller in domain OURDOMAIN due to the following: There are currently no logon servers available to service the logon request. This may lead to authentication problems. Make sure that this computer is connected to the network. If the problem persists, please contact your domain administrator. E1kexpress 27: Intel®82567LM-3 Gigabit Network Connection – Network link is disconnected. NetBT 4300 – The driver could not be created. WMI 10 - Event filter with query "SELECT * FROM __InstanceModificationEvent WITHIN 60 WHERE TargetInstance ISA "Win32_Processor" AND TargetInstance.LoadPercentage 99" could not be reactivated in namespace "//./root/CIMV2" because of error 0x80041003. Events cannot be delivered through this filter until the problem is corrected. More or less with timestamps it becomes apparent that the network maybe the issue. 1:25:57 - Group Policy is trying to discover the domain controller information 1:25:57 - The network link has been disconnected 1:25:58 - The processing of Group Policy failed because of lack of network connectivity to a domain controller. This may be a transient condition. A success message would be generated once the machine gets connected to the domain controller and Group Policy has successfully processed. If you do not see a success message for several hours, then contact your administrator. 1:25:58 - Making LDAP calls to connect and bind to active directory. DC1.ourdomain.edu 1:25:58 - Call failed after 0 milliseconds. 1:25:58 - Forcing rediscovery of domain controller details. 1:25:58 - Group policy failed to discover the domain controller in 1030 milliseconds 1:25:58 - Periodic policy processing failed for computer OURDOMAIN\%name%$ in 1 seconds. 1:25:59 - A network link has been established at 1Gbps at full duplex 1:26:00 - The network link has been disconnected 1:26:02 - NtpClient was unable to set a domain peer to use as a time source because of discovery error. NtpClient will try again in 3473457 minutes and DOUBLE THE REATTEMPT INTERVAL thereafter. 1:26:05 - A network link has been established at 1Gbps at full duplex 1:26:08 - Name resolution for the name %Name% timed out after none of the configured DNS servers responded. 1:26:10 – The TCP/IP NetBIOS Helper service entered the running state. 1:26:11 - The time provider NtpClient is currently receiving valid time data at dc4.ourdomain.edu 1:26:14 – User Logon Notification for Customer Experience Improvement Program 1:26:15 - Group Policy received the notification Logon from Winlogon for session 1. 1:26:15 - Making LDAP calls to connect and bind to Active Directory. dc4.ourdomain.edu 1:26:18 - The LDAP call to connect and bind to Active Directory completed. dc4. ourdomain.edu. The call completed in 2309 milliseconds. 1:26:18 - Group Policy successfully discovered the Domain Controller in 2918 milliseconds. 1:26:18 - Computer details: Computer role : 2 Network name : (Blank) 1:26:18 - The LDAP call to connect and bind to Active Directory completed. dc4.ourdomain.edu. The call completed in 2309 milliseconds. 1:26:18 - Group Policy successfully discovered the Domain Controller in 2918 milliseconds. 1:26:19 - The WinHTTP Web Proxy Auto-Discovery Service service entered the running state. 1:26:46 - The Network Connections service entered the running state. 1:27:10 – Retrieved account information 1:27:10 – The system call to get account information completed. 1:27:10 - Starting policy processing due to network state change for computer OURDOMAIN\%name%$ 1:27:10 – Network state change detected 1:27:10 - Making system call to get account information. 1:27:11 - Making LDAP calls to connect and bind to Active Directory. dc4.ourdomain.edu 1:27:13 - Computer details: Computer role : 2 Network name : ourdomain.edu (Now not blank) 1:27:13 - Group Policy successfully discovered the Domain Controller in 2886 milliseconds. 1:27:13 - The LDAP call to connect and bind to Active Directory completed. dc4.ourdomain.edu The call completed in 2371 milliseconds. 1:27:15 - Estimated network bandwidth on one of the connections: 0 kbps. 1:27:15 - Estimated network bandwidth on one of the connections: 8545 kbps. 1:27:15 - A fast link was detected. The Estimated bandwidth is 8545 kbps. The slow link threshold is 500 kbps. 1:27:17 – Powershell - Engine state is changed from Available to Stopped. 1:27:20 - Completed Group Policy Local Users and Groups Extension Processing in 4539 milliseconds. 1:27:25 - Completed Group Policy Scheduled Tasks Extension Processing in 5210 milliseconds. 1:27:27 - Completed Group Policy Registry Extension Processing in 1529 milliseconds. 1:27:27 - Completed policy processing due to network state change for computer OURDOMAIN\%name%$ in 16 seconds. 1:27:27 – The Group Policy settings for the computer were processed successfully. There were no changes detected since the last successful processing of Group Policy. Any help would be appreciated. Please ask for any relevant information and it will be provided as soon as possible.

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  • Neural Network problems

    - by Betamoo
    I am using an external library for Artificial Neural Networks in my project.. While testing the ANN, It gave me output of all NaN (not a number in C#) The ANN has 8 input , 5 hidden , 5 hidden , 2 output, and all activation layers are of Linear type , and it uses back-propagation, with learning rate 0.65 I used one testcase for training { -2.2, 1.3, 0.4, 0.5, 0.1, 5, 3, -5 } ,{ -0.3, 0.2 } for 1000 epoch And I tested it on { 0.2, -0.2, 5.3, 0.4, 0.5, 0, 35, 0.0 } which gave { NaN , NaN} Note: this is one example of many that produces same case... I am trying to discover whether it is a bug in the library, or an illogical configuration.. The reasons I could think of for illogical configuration: All layers should not be linear Can not have descending size layers, i.e 8-5-5-2 is bad.. Only one testcase ? Values must be in range [0,1] or [-1,1] Is any of the above reasons could be the cause of error, or there are some constraints/rules that I do not know in ANN designing..? Note: I am newbie in ANN

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  • Question about design (inheritance, polymorphism)

    - by Dan
    Hi, I have a question about a problem I'm struggling with. Hope you can bear with me. Imagine I have an Object class representing the base class of a hierarchy of physical objects. Later I inherit from it to create an Object1D, Object2D and Object3D classes. Each of these derived classes will have some specific methods and attributes. For example, the 3d object might have functionality to download a 3d model to be used by a renderer. So I'd have something like this: class Object {}; class Object1D : public Object { Point mPos; }; class Object2D : public Object { ... }; class Object3D : public Object { Model mModel; }; Now I'd have a separate class called Renderer, which simply takes an Object as argument and well, renders it :-) In a similar way, I'd like to support different kinds of renderers. For instance, I could have a default one that every object could rely on, and then provide other specific renderers for some kind of objects: class Renderer {}; // Default one class Renderer3D : public Renderer {}; And here comes my problem. A renderer class needs to get an Object as an argument, for example in the constructor in order to retrieve whatever data it needs to render the object. So far so good. But a Renderer3D would need to get an Object3D argument, in order to get not only the basic attributes but also the specific attributes of a 3d object. Constructors would look like this: CRenderer(Object& object); CRenderer3D(Object3D& object); Now how do I specify this in a generic way? Or better yet, is there a better way to design this? I know I could rely on RTTI or similar but I'd like to avoid this if possible as I feel there is probably a better way to deal with this. Thanks in advance!

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  • Objective-c design advice for use of different data sources, swapping between test and live

    - by user200341
    I'm in the process of designing an application that is part of a larger piece of work, depending on other people to build an API that the app can make use of to retrieve data. While I was thinking about how to setup this project and design the architecture around it, something occurred to me, and I'm sure many people have been in similar situations. Since my work is depending on other people to complete their tasks, and a test server, this slows work down at my end. So the question is: What's the best practice for creating test repositories and classes, implementing them, and not having to depend on altering several places in the code to swap between the test classes and the actual repositories / proper api calls. Contemplate the following scenario: GetDataFromApiCommand *getDataCommand = [[GetDataFromApiCommand alloc]init]; getDataCommand.delegate = self; [getDataCommand getData]; Once the data is available via the API, "GetDataFromApiCommand" could use the actual API, but until then a set of mock data could be returned upon the call of [getDataCommand getData] There might be multiple instances of this, in various places in the code, so replacing all of them wherever they are, is a slow and painful process which inevitably leads to one or two being overlooked. In strongly typed languages we could use dependency injection and just alter one place. In objective-c a factory pattern could be implemented, but is that the best route to go for this? GetDataFromApiCommand *getDataCommand = [GetDataFromApiCommandFactory buildGetDataFromApiCommand]; getDataCommand.delegate = self; [getDataCommand getData]; What is the best practices to achieve this result? Since this would be most useful, even if you have the actual API available, to run tests, or work off-line, the ApiCommands would not necessarily have to be replaced permanently, but the option to select "Do I want to use TestApiCommand or ApiCommand". It is more interesting to have the option to switch between: All commands are test and All command use the live API, rather than selecting them one by one, however that would also be useful to do for testing one or two actual API commands, mixing them with test data. EDIT The way I have chosen to go with this is to use the factory pattern. I set up the factory as follows: @implementation ApiCommandFactory + (ApiCommand *)newApiCommand { // return [[ApiCommand alloc]init]; return [[ApiCommandMock alloc]init]; } @end And anywhere I want to use the ApiCommand class: GetDataFromApiCommand *getDataCommand = [ApiCommandFactory newApiCommand]; When the actual API call is required, the comments can be removed and the mock can be commented out. Using new in the message name implies that who ever uses the factory to get an object, is responsible for releasing it (since we want to avoid autorelease on the iPhone). If additional parameters are required, the factory needs to take these into consideration i.e: [ApiCommandFactory newSecondApiCommand:@"param1"]; This will work quite well with repositories as well.

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  • C# MultiThread Safe Class Design

    - by Robert
    I'm trying to designing a class and I'm having issues with accessing some of the nested fields and I have some concerns with how multithread safe the whole design is. I would like to know if anyone has a better idea of how this should be designed or if any changes that should be made? using System; using System.Collections; namespace SystemClass { public class Program { static void Main(string[] args) { System system = new System(); //Seems like an awkward way to access all the members dynamic deviceInstance = (((DeviceType)((DeviceGroup)system.deviceGroups[0]).deviceTypes[0]).deviceInstances[0]); Boolean checkLocked = deviceInstance.locked; //Seems like this method for accessing fields might have problems with multithreading foreach (DeviceGroup dg in system.deviceGroups) { foreach (DeviceType dt in dg.deviceTypes) { foreach (dynamic di in dt.deviceInstances) { checkLocked = di.locked; } } } } } public class System { public ArrayList deviceGroups = new ArrayList(); public System() { //API called to get names of all the DeviceGroups deviceGroups.Add(new DeviceGroup("Motherboard")); } } public class DeviceGroup { public ArrayList deviceTypes = new ArrayList(); public DeviceGroup() {} public DeviceGroup(string deviceGroupName) { //API called to get names of all the Devicetypes deviceTypes.Add(new DeviceType("Keyboard")); deviceTypes.Add(new DeviceType("Mouse")); } } public class DeviceType { public ArrayList deviceInstances = new ArrayList(); public bool deviceConnected; public DeviceType() {} public DeviceType(string DeviceType) { //API called to get hardwareIDs of all the device instances deviceInstances.Add(new Mouse("0001")); deviceInstances.Add(new Keyboard("0003")); deviceInstances.Add(new Keyboard("0004")); //Start thread CheckConnection that updates deviceConnected periodically } public void CheckConnection() { //API call to check connection and returns true this.deviceConnected = true; } } public class Keyboard { public string hardwareAddress; public bool keypress; public bool deviceConnected; public Keyboard() {} public Keyboard(string hardwareAddress) { this.hardwareAddress = hardwareAddress; //Start thread to update deviceConnected periodically } public void CheckKeyPress() { //if API returns true this.keypress = true; } } public class Mouse { public string hardwareAddress; public bool click; public Mouse() {} public Mouse(string hardwareAddress) { this.hardwareAddress = hardwareAddress; } public void CheckClick() { //if API returns true this.click = true; } } }

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  • Using design-patterns to transform web-service model classes into local model classes and vise versa

    - by Daniil Petrov
    There is a web-application built with play framework 1.2.7. It contains less than 10 model classes. The main purpose of the application is a lightweight access to a complex remote application (more than 50 model classes). The remote application has its own SOAP API and we use it for synchronization of data. There is a scheduled job in the web-app which makes requests to the remote app. It gets bunches of objects from the remote model and populates corresponding objects of the local model. Currently, there are two groups of classes - the local model and the remote model (generated from wsdl schema). It is not allowed to make any modifications to the remote model. Transformations are being made in the scheduled job class. When it gets objects from the remote app it creates local objects. Recently, it was decided to add a possibility to modify the remote objects. It requires more transformations on our side. We need to transform from remote to local model when reading objects and from local to remote when changing objects. I wonder if this would be possible to use some design-patterns to reduce a number of transformations?

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  • Object oriented design importance

    - by user5507
    I started studying Object Oriented Design and Modelling using the this book by James Rumbaugh. It uses a tool called Object Modeling Technique (OMT). I have certain newbie questions. I searched the net, but couldn't get answers The book is pretty old. Don't know why the school told me to learn this. I know OMT is a predecessor of the Unified Modeling Language (UML). So its a waste? Whether the concepts change very much when we move from OMT to UML? I know OMT has Object, Dynamic and Functional Model. Wikipedia says UML is compatible with OMT and UML is a model too. As per wikipedia the UML models are Static and Dynamic and they are represented by different diagrams like class, object, activity, sequence..... I couldn't find the equivalence of this in OMT. I read that there are many object oriented development methods like OMT, Booch,.... Which one is used by Industry ? Where could I get a comparison of different Object oriented development methods?

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  • Design pattern for window management in a Java Swing app

    - by Lord Torgamus
    I've just started creating my very first little Java Swing app. When the program opens, it brings up a single, simple window with a label and a couple buttons. Clicking one of those buttons is supposed to wipe out the welcome screen and replace it with a totally different panel. I'm not sure what the best way to create that functionality is. One method would be to pass my JFrame as an argument into... just about every other component, but that feels hacky to me. Or, there's making each panel double as an action listener, but that doesn't seem right, either. Is there a design pattern I should be applying here? "Replace the contents of the main — and only — window" must be a reasonably common operation. A name for the pattern would be enough; I can use Google on my own from there. (I wouldn't say no to a longer explanation, though.)

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  • Can't get bonding and bridging to work for KVM

    - by user9546
    Hi everyone. I can't for the life of me get bonding and bridging to work for the KVM setup I'm building. I'm using a fresh install (not an upgrade) of Ubuntu Server 10.10. I have 4 NICs on the same subnet (two intended for each of my two VMs). I'm trying to achieve the setup that Uthark describes here. But following his guidelines didn't work for me. My eth0 and eth1 did not come up, and "brctl show" showed that br0 didn't have any interfaces (the bond). I assumed it didn't work because he's using 10.4, and this article says there's a recent change in bonding: [I can't post more than one hyperlink per post because I'm a newbie.] I had to use this article to get my interfaces to work at all on the same subnet, which is why I have the post-up lines on some of my interfaces: [I can't post more than one hyperlink per post because I'm a newbie.] I installed ifenslave and ethtool. I also created /etc/modprobe.d/aliases.conf with the following content: alias bond0 bonding options bonding mode=6 miimon=100 downdelay=200 updelay=200 And I included "bonding" in /etc/modules So, after several approaches, here is my latest interfaces file: auto lo iface lo inet loopback auto eth5 iface eth5 inet manual auto br5 iface br5 inet static post-up /sbin/ip rule add from [network].79 lookup 10 post-up /sbin/ip route add table 10 default via [network].1 src [network].79 dev br5 address [network].79 netmask 255.255.255.0 network [network].0 broadcast [network].255 gateway [network].1 bridge_ports eth5 bridge_stp off bridge_fd 0 bridge_maxwait 0 auto eth2 iface eth2 inet manual auto br2 iface br2 inet static post-up /sbin/ip rule add from [network].78 lookup 11 post-up /sbin/ip route add table 11 default via [network].1 src [network].78 dev br2 address [network].78 netmask 255.255.255.0 network [network].0 broadcast [network].255 gateway [network].1 bridge_ports eth2 bridge_stp off bridge_fd 0 bridge_maxwait 0 iface eth0 inet manual iface eth1 inet manual auto bond0 iface bond0 inet static bond_miimon 100 bond_mode balance-alb up /sbin/ifenslave bond0 eth0 eth1 down /sbin/ifenslave -d bond0 eth0 eth1 auto br0 iface br0 inet static address [network].60 netmask 255.255.255.0 network [network].0 broadcast [network].255 gateway [network].1 bridge_ports bond0 eth2, eth5, br2, and br5 all seem to be working fine. The only other thing I could find that looked suspicious is an error regarding bonding in /var/log/messages: kernel: [ 3.828684] bonding: Warning: either miimon or arp_interval and arp_ip_target module parameters must be specified, otherwise bonding will not detect link failures! see bonding.txt for details. even though there is a bond-miimon line in /etc/network/interfaces (if that's what they're talking about). Also, the bond seems to go in and out of promiscuous mode several times on boot: Jan 20 14:19:02 kvmhost kernel: [ 3.902378] device bond0 entered promiscuous mode Jan 20 14:19:02 kvmhost kernel: [ 3.902390] device bond0 left promiscuous mode Jan 20 14:19:02 kvmhost kernel: [ 3.902393] device bond0 entered promiscuous mode Jan 20 14:19:02 kvmhost kernel: [ 3.902397] device bond0 left promiscuous mode Jan 20 14:19:03 kvmhost kernel: [ 4.998990] device bond0 entered promiscuous mode Jan 20 14:19:03 kvmhost kernel: [ 4.999005] device bond0 left promiscuous mode Jan 20 14:19:03 kvmhost kernel: [ 4.999008] device bond0 entered promiscuous mode Jan 20 14:19:03 kvmhost kernel: [ 4.999012] device bond0 left promiscuous mode Any advice would be greatly appreciated. It seems that this must be possible, based on other posts, but I can't see what I'm doing wrong. Thanks.

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