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• Flex - Increase timeout on a PHP service function call

  - by Travesty3

  I'm using Flash Builder 4 Beta 2. I have it connecting to a PHP service. The way I set this up was using the wizard, so I didn't actually write the code to connect to it. The service looks like this: package services.flash { import mx.rpc.AsyncToken; import com.adobe.fiber.core.model_internal; import mx.rpc.AbstractOperation; import valueObjects.CustomDatatype8; import valueObjects.NewUsageData; import mx.collections.ItemResponder; import mx.rpc.remoting.RemoteObject; import mx.rpc.remoting.Operation; import com.adobe.fiber.services.wrapper.RemoteObjectServiceWrapper; import com.adobe.fiber.valueobjects.AvailablePropertyIterator; import com.adobe.serializers.utility.TypeUtility; [ExcludeClass] internal class _Super_FLASH extends RemoteObjectServiceWrapper { // Constructor public function _Super_FLASH() { // initialize service control _serviceControl = new RemoteObject(); var operations:Object = new Object(); var operation:Operation; operation = new Operation(null, "sendCommand"); operation.resultType = Object; operations["sendCommand"] = operation; ... } } One of the functions that I'm calling fetches users from a MySQL database. There are about 30,000 users right now. The service seems to timeout when fetching more than around 22,000 rows, I get the "Channel Disconnected before an acknowledgement was received" error. If I call the PHP script from a browser, it fetches them all with no problems at all, however. I have tried increasing the timeout in the PHP script (which didn't work), but obviously this isn't the problem since the browser is able to pull them up with no problems. Is there a way to increase the timeout of the PHP service in Flash Builder? I'm a bit of a noob when it comes to Flash, so please be descriptive. Thanks in advance!

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• Need events to execute on timer events, metronome precision.

  - by user295734

  I setup a timer to call an event in my application. The problme is the event execution is being skewed by other windows operations. Ex. openning and window, loading a webpage. I need the event to excute exactly on time, every time. When i first set up the app, used a sound file, like a metronome to listen to the even firing, in a steady state, its firing right on, but as soon do something in the windows environment, the sound fires slower, then sort of sppeds up a bit to catch up. So i added a logging method to the event to ctahc the timer ticks. From that data, it appears that the timer is not being affected by the windows app, but my application event calls are being affected. I figured this out by checking the datetime.now in the event, and if i set it to 250 milliseconds, which is 4 clicks per second. You get data something like below. (sec):(ms) 1:000 1:250 1:500 1:750 2:000 2:250 2:500 2:750 3:000 3:250 3:500 3:750 (lets say i execute some windows event)(time will skew) 4:122 4:388 4:600 4:876 (stop doing what i was doing in windows) (going to shorten the data for simplicit, my list was 30sec long) 5:124 5:268 5:500 5:750 (you would se the time go back the same milliseconds it was at the begining) 6:000 6:250 6:500 6:750 7:000 7:250 7:500 7:750 So i'm thinking the timer continues to fire on the same millisecond every time, but its the event that is being skewed to fire off time by other windows operations. Its not a huge skew, but for what i need to accomplish, its unacceptable. Is there anyhting i can do in .NET, hoping to use XAML/WPF application, thats will correct the skewing of events? thx.

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• Why does autoboxing in Java allow me to have 3 possible values for a boolean?

  - by John

  Reference: http://java.sun.com/j2se/1.5.0/docs/guide/language/autoboxing.html If your program tries to autounbox null, it will throw a NullPointerException. javac will give you a compile-time error if you try to assign null to a boolean. makes sense. assigning null to a Boolean is a-ok though. also makes sense, i guess. but let's think about the fact that you'll get a NPE when trying to autounbox null. what this means is that you can't safely perform boolean operations on Booleans without null-checking or exception handling. same goes for doing math operations on an Integer. for a long time, i was a fan of autoboxing in java1.5+ because I thought it got java closer to be truly object-oriented. but, after running into this problem last night, i gotta say that i think this sucks. the compiler giving me an error when I'm trying to do stuff with an uninitialized primitive is a good thing. I think I may be misunderstanding the point of autoboxing, but at the same time I will never accept that a boolean should be able to have 3 values. can anyone explain this? what am i not getting?

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• .NET threading solution for long queries

  - by Eddie

  Senerio We have an application that records incidents. An external database needs to be queried when an incident is approved by a supervisor. The queries to this external database are sometimes taking a while to run. This lag is experienced through the browser. Possible Solution I want to use threading to eliminate the simulated hang to the browser. I have used the Thread class before and heard about ThreadPool. But, I just found BackgroundWorker in this post. MSDN states: The BackgroundWorker class allows you to run an operation on a separate, dedicated thread. Time-consuming operations like downloads and database transactions can cause your user interface (UI) to seem as though it has stopped responding while they are running. When you want a responsive UI and you are faced with long delays associated with such operations, the BackgroundWorker class provides a convenient solution. Is BackgroundWorker the way to go when handling long running queries? What happens when 2 or more BackgroundWorker processes are ran simultaneously? Is it handled like a pool?

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• How to design a RESTful collection resource?

  - by Suresh Kumar

  I am trying to design a "collection of items" resource. I need to support the following operations: Create the collection Remove the collection Add a single item to the collection Add multiple items to the collection Remove a single item from the collection Remove multiple items from the collection This is as far as I have gone: Create collection: ==> POST /service Host: www.myserver.com Content-Type: application/xml <collection name="items"> <item href="item1"/> <item href="item2"/> <item href="item3"/> </collection> <== 201 Created Location: http://myserver.com/service/items Content-Type: application/xml ... Remove collection: ==> DELETE /service/items <== 200 OK Removing a single item from the collection: ==> DELETE /service/items/item1 <== 200 OK However, I am finding supporting the other operations a bit tricky i.e. what methods can I use to: Add single or multiple items to the collection. (PUT doesn't seem to be right here as per HTTP 1.1 RFC Remove multiple items from the collection in one transaction. (DELETE doesn't seem to right here either)

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• Spring - Transaction Readonly

  - by AAK

  Hello Gurus! Just wanted your expert opinions on declarative transaction management for Spring. Here is my setup - A. DAO Layer is Plain old JDBC using jdbcTemplete (No hibernate etc) B. Service Layer is POJO with declarative trasnactions as follows - save*, readonly=false, rollback for Throwable Things work fine with above setup. However when I say get*, readonly=true I see errors in my log file saying - Database connection cannot be marked as readonly. This happens for all get* methods in Service Layer. Now my questions - A. Do I have to say get* as readonly? All my get* methods are pure read DB operations. I do not wish to run them in any transaction context. How serious is the above error? B. When I remove the get* confiiguration, I do not see the errors, morever all my simple get* operations are performed without transactions. Is this the way to go? C. Why would anyone want to have transactional methods where readonly = true? Is there any practical significance of this configuration? Thank you! As always your resposes are much appreciated!

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• Performance of Java matrix math libraries?

  - by dfrankow

  We are computing something whose runtime is bound by matrix operations. (Some details below if interested.) This experience prompted the following question: Do folk have experience with the performance of Java libraries for matrix math (e.g., multiply, inverse, etc.)? For example: JAMA: http://math.nist.gov/javanumerics/jama/ COLT: http://acs.lbl.gov/~hoschek/colt/ Apache commons math: http://commons.apache.org/math/ I searched and found nothing. Details of our speed comparison: We are using Intel FORTRAN (ifort (IFORT) 10.1 20070913). We have reimplemented it in Java (1.6) using Apache commons math 1.2 matrix ops, and it agrees to all of its digits of accuracy. (We have reasons for wanting it in Java.) (Java doubles, Fortran real*8). Fortran: 6 minutes, Java 33 minutes, same machine. jvisualm profiling shows much time spent in RealMatrixImpl.{getEntry,isValidCoordinate} (which appear to be gone in unreleased Apache commons math 2.0, but 2.0 is no faster). Fortran is using Atlas BLAS routines (dpotrf, etc.). Obviously this could depend on our code in each language, but we believe most of the time is in equivalent matrix operations. In several other computations that do not involve libraries, Java has not been much slower, and sometimes much faster.

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• Perl - Read XML

  - by chinna_82

  XML <?xml version='1.0'?> <employee> <name>Smith</name> <age>43</age> <sex>M</sex> <department role='manager'>Operations</department> </employee> Perl use XML::Simple; use Data::Dumper; $xml = new XML::Simple; foreach my $data1 ($data = $xml->XMLin("test.xml")) { print Dumper($data1); } Above code managed to all the xml value like this. Output $VAR1 = { 'department' => { 'content' => 'Operations', 'role' => 'manager' }, 'name' => 'John Doe', 'sex' => 'M', 'age' => '43' }; How do I do, if I only want to get the role value. For this example I need to get Role = manager. Any advice or reference link is highly appreciated.

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• Hibernate overriding database modifications with detached object state

  - by EugeneP

  I'm gonna go with this design: create an object and keep it alive during all web-app session. And I need to synchronize its state with database state. What I want to achieve is that : IF between my db operations, that is, modifications that I persist to a db someone intentionally spoils table rows, then on next saving to a database all those changes WOULD BE OVERWRITTEN with the object state, that always contains valid data. What Hibernate methods do you recommend me to use to persist the modifications in a database? saveOrUpdate() is a possible solution, but maybe there's anything better? Again, I repeat how it looks. First I create an object without collections. Persist it (save()). Then user provides us with additional data. In a serviceLayer, again, we modify our object in memory (say, populate it with collections) and then, persist it again. So every serviceLayer operation of the next step must simply guarantee that database contains the exact persistent copy of this object that we have in memory. If data in a database differ, it MUST BE OVERRIDDEN with the object (kept in memory) state. What Session operations do you recommend?

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• How to handle authenticated user access to resources in document oriented system?

  - by Jeremy Raymond

  I'm developing a document oriented application and need to manage user access to the documents. I have a module that handles user authentication, and another module that handles document CRUD operations on the data store. Once a user is authenticated I need to enforce what operations the user can and cannot perform to documents based upon the user's permissions. The best option I could think of to integrate these two pieces together would be to create another module that duplicates the data API but that also takes the authenticated user as a parameter. The module would delegate the authorization check to the auth module and delegate the document operation to the data access module. Something like: -module(auth_data_access). % User is authenticated (logged into the system) % save_doc validates if user is allowed to save the given document and if so % saves it returning ok, else returns {error, permission_denied} save_doc(Doc, User) -> case auth:save_allowed(Doc, User) of ok -> data_access:save_doc(Doc); denied -> {error, permission_denied} end end. Is there a better way I can handle this?

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• How much effort do you have to put in to get gains from using SSE?

  - by John

  Case One Say you have a little class: class Point3D { private: float x,y,z; public: operator+=() ...etc }; Point3D &Point3D::operator+=(Point3D &other) { this->x += other.x; this->y += other.y; this->z += other.z; } A naive use of SSE would simply replace these function bodies with using a few intrinsics. But would we expect this to make much difference? MMX used to involve costly state cahnges IIRC, does SSE or are they just like other instructions? And even if there's no direct "use SSE" overhead, would moving the values into SSE registers and back out again really make it any faster? Case Two Instead, you're working with a less OO-based code base. Rather than an array/vector of Point3D objects, you simply have a big array of floats: float coordinateData[NUM_POINTS*3]; void add(int i,int j) //yes it's unsafe, no overlap check... example only { for (int x=0;x<3;++x) { coordinateData[i*3+x] += coordinateData[j*3+x]; } } What about use of SSE here? Any better? In conclusion Is trying to optimise single vector operations using SSE actually worthwhile, or is it really only valuable when doing bulk operations?

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• When to call Dispose in Entity Framework?

  - by Abdel Olakara

  Hi All, In my application I am making use of Spring.Net for IoC. The service objects are called from the ASP.Net files to perform CRUD operations using these service object. For example, I have CustomerService to do all CRUD operations on Customer table. I use entity framework and the entities are injected .. my question is where do I call the dispose method? As far as I understood from the API documentations, unless I call Dispose() there is no guaranty it will be garbage collected! So where and how do I do it? Example Service Class: public class CustomerService { public ecommEntities entities = {get; set;} public bool AddCustomer(Customer customer) { try { entities.AddToCustomer(customer); entities.SaveChanges(); return true; } catch (Exception e) { log.Error("Error occured during creation of new customer: " + e.Message + e.StackTrace); return false; } } public bool UpdateCustomer(Customer customer) { entities.SaveChanges(); return true; } public bool DeleteCustomer(Customer customer) . . . And I just create an object of CustomerService at the ASP partial class and call the necessary methods. Thanks in advance for the best practice and ideas.. Regards, Abdel Raoof

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• Is there really such a thing as a char or short in modern programming?

  - by Dean P

  Howdy all, I've been learning to program for a Mac over the past few months (I have experience in other languages). Obviously that has meant learning the Objective C language and thus the plainer C it is predicated on. So I have stumbles on this quote, which refers to the C/C++ language in general, not just the Mac platform. With C and C++ prefer use of int over char and short. The main reason behind this is that C and C++ perform arithmetic operations and parameter passing at integer level, If you have an integer value that can fit in a byte, you should still consider using an int to hold the number. If you use a char, the compiler will first convert the values into integer, perform the operations and then convert back the result to char. So my question, is this the case in the Mac Desktop and IPhone OS environments? I understand when talking about theses environments we're actually talking about 3-4 different architectures (PPC, i386, Arm and the A4 Arm variant) so there may not be a single answer. Nevertheless does the general principle hold that in modern 32 bit / 64 bit systems using 1-2 byte variables that don't align with the machine's natural 4 byte words doesn't provide much of the efficiency we may expect. For instance, a plain old C-Array of 100,000 chars is smaller than the same 100,000 ints by a factor of four, but if during an enumeration, reading out each index involves a cast/boxing/unboxing of sorts, will we see overall lower 'performance' despite the saved memory overhead?

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• What are the fastest-performing options for a read-only, unordered collection of unique strings?

  - by Dan Tao

  Disclaimer: I realize the totally obvious answer to this question is HashSet<string>. It is absurdly fast, it is unordered, and its values are unique. But I'm just wondering, because HashSet<T> is a mutable class, so it has Add, Remove, etc.; and so I am not sure if the underlying data structure that makes these operations possible makes certain performance sacrifices when it comes to read operations -- in particular, I'm concerned with Contains. Basically, I'm wondering what are the absolute fastest-performing data structures in existence that can supply a Contains method for objects of type string. Within or outside of the .NET framework itself. I'm interested in all kinds of answers, regardless of their limitations. For example I can imagine that some structure might be restricted to strings of a certain length, or may be optimized depending on the problem domain (e.g., range of possible input values), etc. If it exists, I want to hear about it. One last thing: I'm not restricting this to read-only data structures. Obviously any read-write data structure could be embedded inside a read-only wrapper. The only reason I even mentioned the word "read-only" is that I don't have any requirement for a data structure to allow adding, removing, etc. If it has those functions, though, I won't complain.

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• Parsing multiple files at a time in Perl

  - by sfactor

  I have a large data set (around 90GB) to work with. There are data files (tab delimited) for each hour of each day and I need to perform operations in the entire data set. For example, get the share of OSes which are given in one of the columns. I tried merging all the files into one huge file and performing the simple count operation but it was simply too huge for the server memory. So, I guess I need to perform the operation each file at a time and then add up in the end. I am new to perl and am especially naive about the performance issues. How do I do such operations in a case like this. As an example two columns of the file are. ID OS 1 Windows 2 Linux 3 Windows 4 Windows Lets do something simple, counting the share of the OSes in the data set. So, each .txt file has millions of these lines and there are many such files. What would be the most efficient way to operate on the entire files.

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• ASP.NET Response Filter to Reformat the rendered output of ASPX pages?

  - by PropellerHead

  I've created a simple HttpModule and response stream to reformat the rendered output of web pages (see code snippets below). In the HttpModule I set the Response.Filter to my PageStream: m_Application.Context.Response.Filter = new PageStream(m_Application.Context); In the PageStream I overwrite the Write method in order to do my reformatting of the rendered output: public override void Write(byte[] buffer, int offset, int count) { string html = System.Text.Encoding.UTF8.GetString(buffer); //Do some string resplace operations here... byte[] input = System.Text.Encoding.UTF8.GetBytes(html); m_DefaultStream.Write(input, 0, input.Length); } And this work fine when using it on simple HTML pages (.html), but when I use this method on ASPX pages (.aspx), the Write method is called several times, splitting up the reformatting into different steps, and potentially destroying the string replacement operations. How do I solve this? Is there a way to let the ASPX page NOT call Write several times, e.g. by changing its buffer size, or have I chosen the wrong approach entirely, by using this Response.Filter method to manipulate the rendered output?

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• Endianness and C API's: Specifically OpenSSL.

  - by Hassan Syed

  I have an algorithm that uses the following OpenSSL calls: HMAC_update() / HMAC_final() // ripe160 EVP_CipherUpdate() / EVP_CipherFinal() // cbc_blowfish These algorithm take a unsigned char * into the "plain text". My input data is comes from a C++ std::string::c_str() which originate from a protocol buffer object as a encoded UTF-8 string. UTF-8 strings are meant to be endian neutrial. However I'm a bit paranoid about how OpenSSL may perform operations on the data. My understanding is that encryption algorithms work on 8-bit blocks of data, and if a unsigned char * is used for pointer arithmetic when the operations are performed the algorithms should be endian neutral and I do not need to worry about anything. My uncertainty is compounded by the fact that I am working on a little-endian machine and have never done any real cross-architecture programming. My beliefs/reasoning are/is based on the following two properties std::string (not wstring) internally uses a 8-bit ptr and a the resulting c_str() ptr will itterate the same way regardless of the CPU architecture. Encryption algorithms are either by design, or by implementation, endian neutral. I know the best way to get a definitive answer is to use QEMU and do some cross-platform unit tests (which I plan to do). My question is a request for comments on my reasoning, and perhaps will assist other programmers when faced with similar problems.

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• Which templating languages output HTML *as a tree of nodes*?

  - by alamar

  HTML is a tree of nodes, before all. It's not just a text. However, most templating engines handle their input and output as it was just a text; they don't care what happens around their tags, their {$foo}'s and <% bar() %>'s; also they don't care about what are they outputting. Sometimes they happen to produce a correct html, but that's just a coincidence; they didn't aim for that, all they wanted is to replace some funny marks in the text stream with their evaluation. There are a few templating engines which do treat their output as a set of nodes; XSLT and Haml come to mind. For some tasks, this has advantages: for example, you can automatically reformat (like, delete all empty text nodes; auto-indent; word-wrap). The result is guaranteed to be a correct xml/sgml unless you use a strict subset of operations that can break that. Also, such templating engine would automatically quote strings, differently in text nodes and in attributes, because it strictly knows whether you're writing an attribute or a text node. Moreover, it can conditionally remove a node from output because it knows where it does begin and end, which is useful, and do other non-trivial node operations. You might not like XSLT for its verbosiness or functionalness, but it's damn helps that your template is xmllint-able XML, and your output is a good sgml/xml. So the question is: Which template engines do you know that treat their output as a set of correct nodes, not just an unstructured text? I know XSLT, Haml and some obscure python-based one. Moar!

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• Conditional insert as a single database transaction in HSQLDB 1.8?

  - by Kevin Pauli

  I'm using a particular database table like a "Set" data structure, i.e., you can attempt to insert the same row several times, but it will only contain one instance. The primary key is a natural key. For example, I want the following series of operations to work fine, and result in only one row for Oklahoma: insert into states_visited (state_name) values ('Oklahoma'); insert into states_visited (state_name) values ('Texas'); insert into states_visited (state_name) values ('Oklahoma'); I am of course getting an error due to the duplicate primary key on subsequent inserts of the same value. Is there a way to make the insert conditional, so that these errors are not thrown? I.e. only do the the insert if the natural key does not already exist? I know I could do a where clause and a subquery to test for the row's existence first, but it seems that would be expensive. That's 2 physical operations for one logical "conditional insert" operation. Anything like this in SQL? FYI I am using HSQLDB 1.8

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• how to merge ecommerce transaction data between two databases

  - by yamspog

  We currently run an ecommerce solution for a leisure and travel company. Everytime we have a release, we must bring the ecommerce site down as we update database schema and the data access code. We are using a custom built ORM where each data entity is responsible for their own CRUD operations. This is accomplished by dynamically generating the SQL based on attributes in the data entity. For example, the data entity for an address would be... [tableName="address"] public class address : dataEntity { [column="address1"] public string address1; [column="city"] public string city; } So, if we add a new column to the database, we must update the schema of the database and also update the data entity. As you can expect, the business people are not too happy about this outage as it puts a crimp in their cash-flow. The operations people are not happy as they have to deal with a high-pressure time when database and applications are upgraded. The programmers are upset as they are constantly getting in trouble for the legacy system that they inherited. Do any of you smart people out there have some suggestions?

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• How to display a busy message over a wpf screen

  - by dave

  Hey, I have a WPF application based on Prism4. When performing slow operations, I want to show a busy screen. I will have a large number of screens, so I'm trying to build a single solution into the framework rather than adding the busy indicator to each screen. These long running operations run in a background thread. This allows the UI to be updated (good) but does not stop the user from using the UI (bad). What I'd like to do is overlay a control with a spinning dial sort of thing and have that control cover the entire screen (the old HTML trick with DIVs). When the app is busy, the control would display thus block any further interaction as well as showing the spinny thing. To set this up, I thought I could just have my app screen in a canvas along with the spinny thing (with a greater ZIndex) then just make the spinny thing visible as required. This, however, is getting hard. Canvases do not seem well set up for this and I think I might be barking up the wrong tree. I would appreciate any help. Thanks.

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• Nullability (Regular Expressions)

  - by danportin

  In Brzozowski's "Derivatives of Regular Expressions" and elsewhere, the function d(R) returning ? if a R is nullable, and Ø otherwise, includes clauses such as the following: d(R1 + R2) = d(R1) + d(R2) d(R1 · R2) = d(R1) ? d(R2) Clearly, if both R1 and R2 are nullable then (R1 · R2) is nullable, and if either R1 or R2 is nullable then (R1 + R2) is nullable. It is unclear to me what the above clauses are supposed to mean, however. My first thought, mapping (+), (·), or the Boolean operations to regular sets is nonsensical, since in the base case, d(a) = Ø (for all a ? S) d(?) = ? d(Ø) = Ø and ? is not a set (nor is the return type of d, which is a regular expression). Furthermore, this mapping isn't indicated, and there is a separate notation for it. I understand nullability, but I'm lost on the definition of the sum, product, and Boolean operations in the definition of d: how are ? or Ø returned from d(R1) ? d(R2), for instance, in the definition off d(R1 · R2)?

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• Clarification of atomic memory access for different OSs

  - by murrekatt

  I'm currently porting a Windows C++ library to MacOS as a hobby project as a learning experience. I stumbled across some code using the Win Interlocked* functions and thus I've been trying to read up on the subject in general. Reading related questions here in SO, I understand there are different ways to do these operations depending on the OS. Interlocked* in Windows, OSAtomic* in MacOS and I also found that compilers have builtin (intrinsic) operations for this. After reading gcc builtin atomic memory access, I'm left wondering what is the difference between intrinsic and the OSAtomic* or Interlocked* ones? I mean, can I not choose between OSAtomic* or gcc builtin if I'm on MacOS when I use gcc? The same if I'd be on Windows using gcc. I also read that on Windows Interlocked* come as both inline and intrinsic versions. What to consider when choosing between intrinsic or inline? In general, are there multiple options on OSs what to use? Or is this again "it depends"? If so, what does it depend on? Thanks!

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• java: libraries for immutable functional-style data structures

  - by Jason S

  This is very similar to another question (Functional Data Structures in Java) but the answers there are not particularly useful. I need to use immutable versions of the standard Java collections (e.g. HashMap / TreeMap / ArrayList / LinkedList / HashSet / TreeSet). By "immutable" I mean immutable in the functional sense (e.g. purely functional data structures), where updating operations on the data structure do not change the original data, but instead return a new instance of the same kind of data structure. Also typically new and old instances of the data structure will share immutable data to be efficient in time and space. From what I can tell my options include: Functional Java Scala Clojure but I'm not sure whether any of these are particularly appealing to me. I have a few requirements/desirements: the collections in question should be usable directly in Java (with the appropriate libraries in the classpath). FJ would work for me; I'm not sure if I can use Scala's or Clojure's data structures in Java w/o having to use the compilers/interpreters from those languages and w/o having to write Scala or Clojure code. Core operations on lists/maps/sets should be possible w/o having to create function objects with confusing syntaxes (FJ looks slightly iffy) They should be efficient in time and space. I'm looking for a library which ideally has done some performance testing. FJ's TreeMap is based on a red-black tree, not sure how that rates. Documentation / tutorials should be good enough so someone can get started quickly using the data structures. FJ fails on that front. Any suggestions?

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• Creating collaborative whiteboard drawing application

  - by Steven Sproat

  I have my own drawing program in place, with a variety of "drawing tools" such as Pen, Eraser, Rectangle, Circle, Select, Text etc. It's made with Python and wxPython. Each tool mentioned above is a class, which all have polymorphic methods, such as left_down(), mouse_motion(), hit_test() etc. The program manages a list of all drawn shapes -- when a user has drawn a shape, it's added to the list. This is used to manage undo/redo operations too. So, I have a decent codebase that I can hook collaborative drawing into. Each shape could be changed to know its owner -- the user who drew it, and to only allow delete/move/rescale operations to be performed on shapes owned by one person. I'm just wondering the best way to develop this. One person in the "session" will have to act as the server, I have no money to offer free central servers. Somehow users will need a way to connect to servers, meaning some kind of "discover servers" browser...or something. How do I broadcast changes made to the application? Drawing in realtime and broadcasting a message on each mouse motion event would be costly in terms of performance and things get worse the more users there are at a given time. Any ideas are welcome, I'm not too sure where to begin with developing this (or even how to test it)

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