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• OS-independent Inter-program communication between Python and C

  - by Gyppo

  I have very little idea what I'm doing here, I've never done anything like this before, but a friend and I are writing competing chess programs and they need to be able to communicate to each other. He'll be writing mainly in C, the bulk of mine will be in Python, and I can see a few options: Alternately write to a temp file, or successive temp files. As the communication won't be in any way bulky this could work, but seems like an ugly work-around to me, the programs will have to keep checking for change/new files, it just seems ugly. Find some way of manipulating pipes i.e. mine.py| ./his . This seems like a bit of a dead end. Use sockets. But I don't know what I'd be doing, so could someone give me a pointer to some reading material? I'm not sure if there are OS-independent, language independent methods. Would there have to be some kind of supervisor server program to administrate? Use some kind of HTML protocol, which seems like overkill. I don't mind the programs having to run on the same machine. What do people recommend, and where can I start reading?

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• DTOs Collections mapping Problem

  - by the_knight5000

  I'm working now on a multi-tier project which has layers as following : DAL BLL GUI Layer and Shared DTOs between BLL and GUI layers. I'm facing a problem in mapping the Objects from DAO To DTO, No problem in the simple objects. The problem is in the Objects who have child collections of another objects. ex: Author Category --Categories --Authors the execution goes in an infinite loop of mapping and it get more complex when I want model Self-join tables ex: Safe Safe --TransferSafe(Collection<Safe>) --TransferSafe(Collection<Safe>) the execution goes in an infinite loop of mapping any suggestions about a good solution or a practical mapping pattern?

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• Needs opinions based on design guidelines .

  - by Abu Hamzah

  i am in the process of desigining my domain model and i know its very hard to suggest without knowledge of domain but what i am asking is how to implement or the best way of implementing the baseclass in my domain model. here are few classes: PartialPerson.cs Facilities.cs Visit.cs EntryPoint.cs etc.... my baseclass looks like this: public abstract class BaseClass { public int InfoId { get; } public int PersonId { get; } } here is what i am confused and need help. how do i implement the above baseclass? in the PartialPerson,Facilities,Visit...

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• How can I get the "Latency" of a process that has a TCP connection open?

  - by Dave

  Hello, I am looking to get the "Latency" field of a TCP connection. I notice windows Resource Monitor has this field, and I was wondering if there was a way I can find it. Preferrably without using WMI. If you are unsure what field I am talking about, open Task Manager, goto the Performance tab and hit the Resource Monitor button. Once Resource Monitor is open, expand the TCP Connections area and you will see a Latency field. Is there anyway to access this programatically? Thanks!

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• Should I combine unrelated interfaces into a single library?

  - by mafutrct

  Situation is like this: There are independent 5 services. Each service consists of a project for interface, implementation and test. Example: LocalizationService.Interfaces LocalizationService.Implementation LocalizationService.Test There is a WCF service for each of the services: LocalizationService.WcfContract (including DataContracts) LocalizationService.WcfHost The client applications are probably mostly going to use all of the services. Should I combine all service interfaces into a common one? AllServices.AllInterfaces In my opinion, this is a bad idea. The services are independent and there is no reason to introduce a dependency. I imagine that especially testing becomes more difficult. However, one may argue that having to include 5 libraries is too much of a hassle. (I'm not sure how to tag this. Feel free to retag.)

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• Should core application configuration be stored in the database, and if so what should be done to se

  - by Rl

  I'm writing an application around a lot of hierarchical data. Currently the hierarchy is fixed, but it's likely that new items will be added to the hierarchy in the future. (please let them be leaves) My current application and database design is fairly generic and nothing dealing with specific nodes in the hierarchy is hardcoded, with the exception of validation and lookup functions written to retrieve external data from each node's particular database. This pleases me from a design point of view, but I'm nervous at the realization that the entire application rests on a handful of records in the database. I'm also frustrated that I have to enforce certain aspects of data integrity with database triggers rather than by foreign key constraints (an example is where several different nodes in the hierarchy have their own proprietary IDs and I store them in a single column which, when coupled with the node ID can be used to locate the foreign data). I'm starting to wonder whether it may have been appropriate to simply hardcoded these known nodes into the system so that it would be more "type safe" and less generic. How does one know when something should be hardcoded, and when it should be a configuration item? Is it just a cost-benefit analysis of clarity/safety now vs less work later, or am I missing some metric I should be using to determine whether or not this is appropriate. The steps I'm taking to protect these valuable configurations are to add triggers that prevent updates/deletes. The database user that this application uses will only have the ability to manipulate data through stored procedures. What else can I do?

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• log activity. intrusion detection. user event notification ( interraction ). messaging

  - by Julian Davchev

  Have three questions that I somehow find related so I put them in same place. Currently building relatively large LAMP system - making use of messaging(activeMQ) , memcache and other goodies. I wonder if there are best practices or nice tips and tricks on howto implement those. System is user aware - meaning all actions done can be bind to particular logged user. 1. How to log all actions/activities of users? So that stats/graphics might be extracted later for analysing. At best that will include all url calls, post data etc etc. Meaning tons of inserts. I am thinking sending messages to activeMQ and later cron dumping in DB and cron analysing might be good idea here. Since using Zend Framework I guess I may use some request plugin so I don't have to make the log() call all over the code. 2.How to log stuff so may be used for intrusion detection? I know most things might be done on http level using apache mods for example but there are also specific cases like (5 failed login attempts in a row (leads to captcha) etc etc..) This also would include tons of inserts. Here I guess direct usage of memcache might be best approach as data don't seem vital to be permanantly persisted. Not sure if cannot use data from point 1. 3.System will notify users of some events. Like need approval , something broke..whatever.Some events will need feedback(action) from user, others are just informational. Wonder if there is common solutions for needs like this. Example: Based on occuring event(s) user will be notifed (user inbox for example) what happend. There will be link or something to lead him to details of thingy that happend and take action accordingly. Those seem trivial at first look but problem I see if coding it directly is becoming really fast hard to maintain.

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• In Ruby, is there are better way of selecting a constant (or avoiding the constant altogether) based

  - by Vertis

  Not sure the title fully describes the problem/question I'm trying to ask, sorry. I'm One of my fellow developers has created classes as such: class Widget attr_accessor :model_type ... end and: class ModelType MODEL1 = "model1" MODEL2 = "model2" MODEL3 = "model3" end Now he wants me to convert a retrieved string "MODEL1" to the constant. So that when he is referencing that model elsewhere he can use ModelType::MODEL1. Obviously I've got to convert from the string I'm being given with something like the following: case model_type when 'MODEL1' @model_type = ModelType::MODEL1 ... end I feel like this is clunky, so I'd like to know if there is a better DRYer way of providing this kind of functionality.

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• Good assembly tutorial for windows with eiter fasm or nasm

  - by The new guy

  I have spent the last 3 hours google and bing for a good asm tutorial(x86 variety). I have been on this site for many of these results. Non have really been sufficient. Mainly because while i like learning theory, i learn it best via practice, while for example pc-asm has about 20-30 pages of theroy before anything practical. I was wondering if there was a tutorial or online pdf (or cheap book(<£20)) that i could use that suits my style of learning. Please state if this is not possibke Thank you for your time

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• Dragging on Different Levels

  - by Fahim Akhter

  Hi, I have a flash project with three non overlapping panels (visual spaces) each of which contains different movie-clips. Each movie-clip in a particular panel is the child of that panel. Now, I want to drag one of the movie-clips from one panel to another (remove it as a child from the first panel and add it to the other) without a jitter and proper drag. What is the appropriate way to handle the drag architecturally. Should the drag be handled in all panels parent. In the panels, or the items themselves? Thanks.

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• What difference between Web Apps & Descktop app shoud one keep in mind to model the system right?

  - by simple

  Sometimes it seems like some architectural techniques are not for the Web application I am building and then I just go and code =(, Though I really want to make a habit to architect system before moving to the code, as when I just code I endup writing some useless components which then I rewrite =(, So can you just point out some differences between web apps and desktop ones ?

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• Cache bandwidth per tick for modern CPUs

  - by osgx

  Hello What is a speed of cache accessing for modern CPUs? How many bytes can be read or written from memory every processor clock tick by Intel P4, Core2, Corei7, AMD? Please, answer with both theoretical (width of ld/sd unit with its throughput in uOPs/tick) and practical numbers (even memcpy speed tests, or STREAM benchmark), if any. PS it is question, related to maximal rate of load/store instructions in assembler. There can be theoretical rate of loading (all Instructions Per Tick are widest loads), but processor can give only part of such, a practical limit of loading.

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• SQL Server concurrency and generated sequence

  - by Goyuix

  I need a sequence of numbers for an application, and I am hoping to leverage the abilities of SQL Server to do it. I have created the following table and procedure (in SQL Server 2005): CREATE TABLE sequences ( seq_name varchar(50) NOT NULL, seq_value int NOT NULL ) CREATE PROCEDURE nextval @seq_name varchar(50) AS BEGIN DECLARE @seq_value INT SET @seq_value = -1 UPDATE sequences SET @seq_value = seq_value = seq_value + 1 WHERE seq_name = @seq_name RETURN @seq_value END I am a little concerned that without locking the table/row another request could happen concurrently and end up returning the same number to another thread or client. This would be very bad obviously. Is this design safe in this regard? Is there something I can add that would add the necessary locking to make it safe? Note: I am aware of IDENTITY inserts in SQL Server - and that is not what I am looking for this in particular case. Specifically, I don't want to be inserting/deleting rows. This is basically to have a central table that manages the sequential number generator for a bunch of sequences.

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• SYN receives RST,ACK very frequently

  - by user1289508

  Hi Socket Programming experts, I am writing a proxy server on Linux for SQL Database server running on Windows. The proxy is coded using bsd sockets and in C, and it is working just fine. When I use a database client (written in JAVA, and running on a Linux box) to fire queries (with a concurrency of 100 or more) directly to the Database server, not experiencing connection resets. But through my proxy I am experiencing many connection resets. Digging deeper I came to know that connection from 'DB client' to 'Proxy' always succeeds but when the 'Proxy' tries to connect to the DB server the connection fails, due to the SYN packet getting RST,ACK. That was to give some background. The question is : Why does sometimes SYN receives RST,ACK? 'DB client(linux)' to 'Server(windows)' ---- Works fine 'DB client(linux) to 'Proxy(Linux)' to 'Server(windows)' ----- problematic I am aware that this can happen in "connection refused" case but this definitely is not that one. SYN flooding might be another scenario, but that does not explain fine behavior while firing to Server directly. I am suspecting some socket option setting may be required, that the client does before connecting and my proxy does not. Please put some light on this. Any help (links or pointers) is most appreciated. Additional info: Wrote a C client that does concurrent connections, which takes concurrency as an argument. Here are my observations: - At 5000 concurrency and above, some connects failed with 'connection refused'. - Below 2000, it works fine. But the actual problem is observed even at a concurrency of 100 or more. Note: The problem is time dependent sometimes it never comes at all and sometimes it is very frequent and DB client (directly to server) works fine at all times .

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• Need a good website URL to test against

  - by Zombies

  I need a URL to just test basic http connectivity. It needs to be consistent and: Always be up Never change drastically due to IP or user agent. (IE: 301 Location redirect/ huge difference in content... minor would be tolerable) The URL itself has a consistent content-length. (IE: it doesn't vary from by 2kb at most, ever) A few examples, yet none match all 3 criteria: One example of always up: www.google.com (yet it 301 redirects based on IP location). Another good one is http://www.google.com/webhp?hl=en. but the problem there is that based on a given holiday, the content-length can really vary.

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• RBF neural networks

  - by Infinity

  Hello guys! I would like to apply RBF neural networks to teach my system. I have a system with an input: | 1 2 3 4 5 6 ... 32 | 33 | | 1000 0001 0010 0100 1000 1000 ... 0100 | 0 0 1 | You have to read this without the "|" character. I just wanted you to see that the last three elements in the input are staying together. The result have to be a number between 1-32, which has the value "1000" in the input. In my training set I will always have a result for an array of this kind. What kind of functions can I use for the teaching algorithm? Can you point me please to the right way? If you can't understand my description please don't hesitate to ask about it. Thank you guys for your help!

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• Design pattern for loading multiple message types

  - by lukem00

  As I was looking through SO I came across a question about handling multiple message types. My concern is - how do I load such a message in a neat way? I decided to have a separate class with a method which loads one message each time it's invoked. This method should create a new instance of a concrete message type (say AlphaMessage, BetaMessage, GammaMessage, etc.) and return it as a Message. class MessageLoader { public Message Load() { // ... } } The code inside the method is something which looks really awful to me and I would very much like to refactor it/get rid of it: Message msg = Message.Load(...); // load yourself from whatever source if (msg.Type == MessageType.Alpha) return new AlphaMessage(msg); if (msg.Type == MessageType.Beta) return new BetaMessage(msg); // ... In fact, if the whole design looks just too messy and you guys have a better solution, I'm ready to restructure the whole thing. If my description is too chaotic, please let me know what it's missing and I shall edit the question. Thank you all.

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• JAVA: How do I accept input during a certain period of time only

  - by sebrock

  Im trying to do a simple game where I continually need input from players. This needs to happen during a certain time period only. Everything that is sent after that will be discarded. After the time period a new game starts. So: Start game Wait for input from all players during 10 seconds 10 secs no more input Calculate the winner and do some stuff Goto 1. I was thinking using a timer and timertask to keep track of time and maybe use a boolean variable that changes from "open" to "closed" after 10 seconds? Please give me some advise on this.

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• How to scale php application servers horizontally?

  - by Kirzilla

  Hello, I'm using lighttpd as webserver for php application server. The avg. load on this server is about 2-3. MySQL database is separated to another server (it's load ~0.4). How could I scale php application server? Thank you.

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• Properly handling NSURLConnection errors

  - by Cal S

  Hi, I have a simple form interface set up that send username and password information to a server: (working) NSString *postData = [NSString stringWithFormat:@"user=%@&pass=%@",[self urlEncodeValue:sysUsername],[self urlEncodeValue:password]]; NSLog(@"Post data -> %@", postData); /// NSData* postVariables = [postData dataUsingEncoding:NSASCIIStringEncoding allowLossyConversion:YES]; NSMutableURLRequest* request = [[[NSMutableURLRequest alloc] init] autorelease]; NSString* postLength = [NSString stringWithFormat:@"%d", [postVariables length]]; NSURL* postUrl = [NSURL URLWithString:@"http://localhost/~csmith/cocoa/test.php"]; [request setURL:postUrl]; [request setHTTPMethod:@"POST"]; [request setValue:postLength forHTTPHeaderField:@"Content-Length"]; [request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"]; [request setHTTPBody: postVariables]; NSData *returnData = [NSURLConnection sendSynchronousRequest:request returningResponse:NULL error:NULL]; NSLog(@"Post data SENT & returned -> %@", returnData); How do I handle connection errors such as no internet connection, firewall, etc. Also, does this method use the system-wide proxy settings? Many of my users are behind a proxy. Thanks a lot!

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• In Ruby, is there a better way of selecting a constant (or avoiding the constant altogether) based o

  - by Vertis

  Not sure the title fully describes the problem/question I'm trying to ask, sorry. One of my fellow developers has created classes as such: class Widget attr_accessor :model_type ... end and: class ModelType MODEL1 = "model1" MODEL2 = "model2" MODEL3 = "model3" end Now he wants me to convert a retrieved string "MODEL1" to the constant. So that when he is referencing that model elsewhere he can use ModelType::MODEL1. Obviously I've got to convert from the string I'm being given with something like the following: case model_type when 'MODEL1' @model_type = ModelType::MODEL1 ... end I feel like this is clunky, so I'd like to know if there is a better DRYer way of providing this kind of functionality.

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• Information Modeling

  - by Betamoo

  The sensor module in my project consists of a rotating camera, that collects noisy information about moving objects in the surrounding environment. The information consists of distance, angle and relative change of the moving objects.. The limiting view range of the camera makes it essential to rotate the camera periodically to update environment information... I was looking for algorithms / ways to model these information, in order to be able to guess / predict / learn motion properties of these object.. My current proposed idea is to store last n snapshots of each object in a queue. I take weighted average of positions and velocities of moving object, but I think it is a poor method... Can you state some titles that suit this case? Thanks

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• Please suggest other ways of communicating between server & client.

  - by Geo

  I'm writing a TCP chat server ( programming language does not mather ). It's a school project for my nephew, so it won't be released, and all questions I'm asking are just for my knowledge :). . Some of the things it will support: chatting between users ( doh ), it will be multithreaded sending each other files I know I could easily get away with all the stuff above if I go with serialization, and just send objects from client to server and back. But, if I do that, it will be limited to a specific programming language ( meaning clients written in other programming languages may not be able to deserialize the objects ). What would be the way to go so that other clients written in other languages could be supported? One way to go, off the top of my head, would be to go in this direction: the server & the client communicate by sending messages & chunks ( in lieu of other names ). Here's what I mean by this: every time the client/server wants to send something ( text message or file ) it will first send a simple text message ( newline terminated ) with the number of the chunks it will send. Example: command 4,20,30,40,50 Where command would be something like instant-message or file,4 would be the number of chunks to be sent, 20 would be the size in bytes of the first chunk, 30 of the 2nd, and so forth. after the message was sent, the client/server will start sending chunks ( of sizes mentioned in the sent message ). What do you think about implementing the client/server communication this way? What better options are there?

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• iPhone app -- are plists the way to handle default values and other languages?

  - by d_CFO

  I wrote my first program almost fifty years ago (yes, coding is still a blast, managing big projects with many programmers was not), but my Von Neumann thinking gets in the way. I want to (a) load default values and (b) account for multiple languages more elegantly (?) than 60-plus iterations of NSLocalizedString. Can I park all of this data into what amounts to a record with fields like this: (key value stuff), (tweak-able user prompt / screen name / whatever), (tasteful default), (user-supplied value)? NSUserDefault has worked well so far; Core Data looks like overkill (?), and sql lite, well, where's Oracle when you need it?

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• How should I access to SQL Server DB?

  - by worlds-apart89

  I have been reading that direct access to a SQL Server database over the Internet is insecure, so I am wondering what intermediary I can and should use between the client and the server. What are the best practices in terms of security and performance?

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