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• Aligning music notes using String matching algorithms or Dynamic Programming

  - by Dolphin

  Hi I need to compare 2 sets of musical pieces (i.e. a playing-taken in MIDI format-note details extracted and saved in a database table, against sheet music-taken into XML format). When evaluating playing against sheet music (i.e.note details-pitch, duration, rhythm), note alignment needs to be done - to identify missed/extra/incorrect/swapped notes that from the reference (sheet music) notes. I have like 1800-2500 notes in one piece approx (can even be more-with polyphonic, right now I'm doing for monophonic). So will I have to have all these into an array? Will it be memory overloading or stack overflow? There are string matching algorithms like KMP, Boyce-Moore. But note alignment can also be done through Dynamic Programming. How can I use Dynamic Programming to approach this? What are the available algorithms? Is it about approximate string matching? Which approach is much productive? String matching algos like Boyce-Moore, or dynamic programming? How can I assess which is more effective? Greatly appreciate any insight or suggestions Thanks in advance

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• NES Programming - Nametables?

  - by Jeffrey Kern

  Hello everyone, I'm wondering about how the NES displays its graphical muscle. I've researched stuff online and read through it, but I'm wondering about one last thing: Nametables. Basically, from what I've read, each 8x8 block in a NES nametable points to a location in the pattern table, which holds graphic memory. In addition, the nametable also has an attribute table which sets a certain color palette for each 16x16 block. They're linked up together like this: (assuming 16 8x8 blocks) Nametable, with A B C D = pointers to sprite data: ABBB CDCC DDDD DDDD Attribute table, with 1 2 3 = pointers to color palette data, with < referencing value to the left, ^ above, and ' to the left and above: 1<2< ^'^' 3<3< ^'^' So, in the example above, the blocks would be colored as so 1A 1B 2B 2B 1C 1D 2C 2C 3D 3D 3D 3D 3D 3D 3D 3D Now, if I have this on a fixed screen - it works great! Because the NES resolution is 256x240 pixels. Now, how do these tables get adjusted for scrolling? Because Nametable 0 can scroll into Nametable 1, and if you keep scrolling Nametable 0 will wrap around again. That I get. But what I don't get is how to scroll the attribute table wraps around as well. From what I've read online, the 16x16 blocks it assigns attributes for will cause color distortions on the edge tiles of the screen (as seen when you scroll left to right and vice-versa in SMB3). The concern I have is that I understand how to scroll the nametables, but how do you scroll the attribute table? For intsance, if I have a green block on the left side of the screen, moving the screen to right should in theory cause the tiles to the right to be green as well until they move more into frame, to which they'll revert to their normal colors.

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• SqlCeResultSet Problem

  - by Vlad

  Hello, I have a SmartDevice project (.NetCF 2.0) configured to be tested on the USA Windows Mobile 5.0 Pocket PC R2 Emulator. My project uses SqlCe 3.0. Understanding that a SmartDevice project is "more carefull" with the device's memory I am using SqlCeResultSets. The result sets are strongly typed, autogenerated by Visual Studio 2008 using the custom tool MSResultSetGenerator. The problem I am facing is that the result set does not recognize any column names. The autogenerated code for the fields does not work. In the client code I am using InfoResultSet rs = new InfoResultSet(); rs.Open(); rs.ReadFirst(); string myFormattedDate = rs.MyDateColumn.ToString("dd/MM/yyyy"); When the execution on the emulator reaches the rs.MyDateColumn the application throws an System.IndexOutOfRangeException. Investigating the stack trace at System.Data.SqlServerCe.FieldNameLookup.GetOrdinal() at System.Data.SqlServerCe.SqlCeDataReader.GetOrdinal() I've tested the GetOrdinal method (in my autogenerated class that inherits SqlCeResultSet): this.GetOrdinal("MyDateColumn"); // throws an exception this.GetName(1); // returns "MyDateColumn" this.GetOrdinal(this.GetName(1)); //throws an exception :) [edit added] The table exists and it's filled with data. Using typed DataSets works like a charm. Regenerating the SqlCeResultSet does not solve the issue, the problem remains. The problem basically is that I am not able to access a column by it's name. The data can be accessed trough this.GetDateTime(1)using the column ordinal. The application fails executing this.GetOrdinal("MyDateColumn"). Also I have updated Visual Studio 2008 to Service Pack 1. Additionaly I am developing the project on a virtual machine with Windows XP SP 2, but in my opinion if the medium is virtual or not should have no effect on the developing. Am I doing something wrong or am I missing something? Thank you.

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• Pump Messages During Long Operations + C#

  - by Newbie

  Hi I have a web service that is doing huge computation and is taking more than a minute. I have generated the proxy file of the web service and then from my client end I am using the dll(of course I generated the proxy dll). My client side code is TimeSeries3D t = new TimeSeries3D(); int portfolioId = 4387919; string[] str = new string[2]; str[0] = "MKT_CAP"; DateRange dr = new DateRange(); dr.mStartDate = DateTime.Today; dr.mEndDate = DateTime.Today; Service1 sc = new Service1(); t = sc.GetAttributesForPortfolio(portfolioId, true, str, dr); But since it is taking to much time for the server to compute, after 1 minute I am receiving an error message The CLR has been unable to transition from COM context 0x33caf30 to COM context 0x33cb0a0 for 60 seconds. The thread that owns the destination context/apartment is most likely either doing a non pumping wait or processing a very long running operation without pumping Windows messages. This situation generally has a negative performance impact and may even lead to the application becoming non responsive or memory usage accumulating continually over time. To avoid this problem, all single threaded apartment (STA) threads should use pumping wait primitives (such as CoWaitForMultipleHandles) and routinely pump messages during long running operations. Kindly guide me what to do? Thanks

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• Framework or design pattern for mailing all users of a webapp

  - by Todd Owen

  My app takes care of user registration (with the option to receive email announcements), and can easily handle the actual template-based rendering of email for a given user. JavaMail provides the mail transport layer. But how should I design the application layer between the business objects (e.g. User) and the mail transport? The straightforward approach would be a simple, synchronous loop: iterate through the users, queue the emails, and be done with it. "Queue" might mean sending them straight to the MTA (mail server), or to an in-memory queue to be consumed by another thread. However, I also plan to implement features like throttling the rate of emails, processing bounced emails (NDRs), and maintaining status across application restarts. My intuition is that a good design would decouple this from both the business layer and the mail transport layer as much as possible. I wondered if others had solved this problem before, but after much searching I haven't found any Java libraries which seem to fit this problem. Standalone mail apps such as James or list servers are too large in scope; packages like Spring's MailSender or Commons Email are too small in scope (being basically drop-in replacements for JavaMail). For other languages I haven't found anything appropriate either. I'm curious about how other developers have gone about adding bulk mailing to their applications.

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• Java: autofiltering list?

  - by Jason S

  I have a series of items arriving which are used in one of my data structures, and I need a way to keep track of those items that are retained. interface Item {} class Foo implements Item { ... } class Baz implements Item { ... } class StateManager { List<Foo> fooList; Map<Integer, Baz> bazMap; public List<Item> getItems(); } What I want is that if I do the following: for (int i = 0; i < SOME_LARGE_NUMBER; ++i) { /* randomly do one of the following: * 1) put a new Foo somewhere in the fooList * 2) delete one or more members from the fooList * 3) put a new Baz somewhere in the bazMap * 4) delete one or more members from the bazMap */ } then if I make a call to StateManager.getItems(), I want to return a list of those Foo and Baz items, which are found in the fooList and the bazMap, in the order they were added. Items that were deleted or displaced from fooList and bazMap should not be in the returned list. How could I implement this? SOME_LARGE_NUMBER is large enough that I don't have the memory available to retain all the Foo and Baz items, and then filter them.

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• Objective C code to handle large amount of data processing in iPhone

  - by user167662

  I had the following code that takes in 14 mb or more of image data encoded in base4 string and converts them to jpeg before writing to a file in iphone. It crashes my program giving the following error : Program received signal: “0”. warning: check_safe_call: could not restore current frame I tweak my program and it can process a few more images before the error appear again. My coding is as follows: // parameters is an array where the fourth element contains a list of images in base64 >encoded string NSMutableArray *imageStrList = (NSMutableArray*) [parameters objectAtIndex:5]; while (imageStrList.count != 0) { NSString *imgString = [imageStrList objectAtIndex:0]; // Create a file name using my own Utility class NSString *fileName = [Utility generateFileNName]; NSData *restoredImg = [NSData decodeWebSafeBase64ForString:imgString]; UIImage *img = [UIImage imageWithData: restoredImg]; NSData *imgJPEG = UIImageJPEGRepresentation(img, 0.4f); [imgJPEG writeToFile:fileName atomically:YES]; [imageStrList removeObjectAtIndex:0]; } I tried playing around with UIImageJPEGRepresentation and found out that the lower the value, the more image it can processed but this should not be the way. I am wondering if there is anyway to free up memory of the imageStrList immediately after processing each image so that it can be used by the next one in the line.

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• Array: Recursive problem cracked me up

  - by VaioIsBorn

  An array of integers A[i] (i 1) is defined in the following way: an element A[k] ( k 1) is the smallest number greater than A[k-1] such that the sum of its digits is equal to the sum of the digits of the number 4* A[k-1] . You need to write a program that calculates the N th number in this array based on the given first element A[1] . INPUT: In one line of standard input there are two numbers seperated with a single space: A[1] (1 <= A[1] <= 100) and N (1 <= N <= 10000). OUTPUT: The standard output should only contain a single integer A[N] , the Nth number of the defined sequence. Input: 7 4 Output: 79 Explanation: Elements of the array are as follows: 7, 19, 49, 79... and the 4th element is solution. I tried solving this by coding a separate function that for a given number A[k] calculates the sum of it's digits and finds the smallest number greater than A[k-1] as it says in the problem, but with no success. The first testing failed because of a memory limit, the second testing failed because of a time limit, and now i don't have any possible idea how to solve this. One friend suggested recursion, but i don't know how to set that. Anyone who can help me in any way please write, also suggest some ideas about using recursion/DP for solving this problem. Thanks.

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• Which MySQL Fork/Version to Pick??

  - by Drew

  As most of you know, Sun acquired MySQL (and later Oracle acquired Sun), and during these acquisitions, there were a lot of FUD in MySQL community which resulted in creation of various forks. Today we have MySQL from MySQL, Percona (XtraDB) MySQL, OurDelta MySQL, MariaDB, Drizzle to name a few. Which brings us to the source of the problem. We are in the process of upgrading our databases (hardware/software) and I would like to know which one of the forks should I go with. Each has their own set of pros/cons. We are currently using MySQL 5.0.x from MySQL/Linux on an 8-core machine. Our new hardware is a monster with 32 cores and 32GB of memory connecting to a fast NetApp Storage via FC. I would like to stick with MySQL from MySQL but I have heard horror stories on how badly MySQL 5.1 performs on many cores. I have also heard that MySQL 5.4 performs better on multi-core machines but that's still not production ready. In addition, I have also heard a lot of good things about Percona builds. This is what I know so far: MySQL 5.1 from MySQL: Reliable choice, but doesn't scale well on a big machine Percona: Scales well, good backing company. I don't have much experience with it MariaDB: Don't know much about it besides that it was founded by Original MySQL developers (including Monty) OurDelta: Don't know much Drizzle: Mostly optimized for cloud computing I would like to know what's the general notion about this problem. Which build/version should I go with? How are you guys picking your builds/versions? Thanks!

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• How can I improve the performance of LinqToSql queries that use EntitySet properties?

  - by DanM

  I'm using LinqToSql to query a small, simple SQL Server CE database. I've noticed that any operations involving sub-properties are disappointingly slow. For example, if I have a Customer table that is referenced by an Order table, LinqToSql will automatically create an EntitySet<Order> property. This is a nice convenience, allowing me to do things like Customer.Order.Where(o => o.ProductName = "Stopwatch"), but for some reason, SQL Server CE hangs up pretty bad when I try to do stuff like this. One of my queries, which isn't really that complicated takes 3-4 seconds to complete. I can get the speed up to acceptable, even fast, if I just grab the two tables individually and convert them to List<Customer> and List<Order>, then join then manually with my own query, but this is throwing out a lot of what makes LinqToSql so appealing. So, I'm wondering if I can somehow get the whole database into RAM and just query that way, then occasionally save it. Is this possible? How? If not, is there anything else I can do to boost the performance besides resorting to doing all the joins manually? Note: My database in its initial state is about 250K and I don't expect it to grow to more than 1-2Mb. So, loading the data into RAM certainly wouldn't be a problem from a memory point of view. Update Here are the table definitions for the example I used in my question: create table Order ( Id int identity(1, 1) primary key, ProductName ntext null ) create table Customer ( Id int identity(1, 1) primary key, OrderId int null references Order (Id) )

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• Can't get screen pixel from a specific full screen game with any language?

  - by user1007059

  Okay, I know this might seem like I'm posting a duplicate question since I've asked something similar like a day ago HOWEVER, if anyone sees any problem with this, please read my question first before judging: Yesterday I tried getting a specific pixel from a fullscreen game in C#. I thought my C# code was faulty but when I tried with multiple full screen games today they all worked except for that specific game. I literally tried with 10 different full screen games, a couple being mmofps, mmorpg, mmotps, regular rpg games, regular shooters, regular action adventure games, etc. I tried with multiple programming languages, and with every game except that specific game I'm dealing with, it returns the pixel color to me like I wanted. So let me explain what I tried: first I tried returning an IntPtr with C# using GetDC(IntPtr.Zero) before invoking GetPixel(int x, int y) and then getting the color out of it. Then I tried using the Robot class in Java and using the getPixelColor(int x, int y) method. I also tried using GetDC(0) to return an HDC object in C++ and then invoking GetPixel(int x, int y) before again extracting the color. These three methods worked EXACTLY the same in every single game except that specific game I was talking about. They returned the pixel perfectly, and extracted the exact same color perfectly. I don't feel it's necessary to tell you the game name or anything, since you probably don't even know it, but what could possibly be causing this malfunction in 1 specific game? PS: The game ALWAYS returns an RGB color of: A = 255, R = 0, G = 0, B = 0. Also, I tried taking a snapshot of the game with the 3 programming languages, and then getting the pixel which actually works in all 3 languages, but since I need to get this pixel every 30 ms, it kind of makes my game lag a bit (+ I think it takes up a lot of memory)

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• Better use a tuple or numpy array for storing coordinates

  - by Ivan

  Hi, I'm porting an C++ scientific application to python, and as I'm new to python, some problems come to my mind: 1) I'm defining a class that will contain the coordinates (x,y). These values will be accessed several times, but they only will be read after the class instantiation. Is it better to use an tuple or an numpy array, both in memory and access time wise? 2) In some cases, these coordinates will be used to build a complex number, evaluated on a complex function, and the real part of this function will be used. Assuming that there is no way to separate real and complex parts of this function, and the real part will have to be used on the end, maybe is better to use directly complex numbers to store (x,y)? How bad is the overhead with the transformation from complex to real in python? The code in c++ does a lot of these transformations, and this is a big slowdown in that code. 3) Also some coordinates transformations will have to be performed, and for the coordinates the x and y values will be accessed in separate, the transformation be done, and the result returned. The coordinate transformations are defined in the complex plane, so is still faster to use the components x and y directly than relying on the complex variables? Thank you

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• Creating subtree from tree which is represented in xml - python

  - by Jay

  Hi I have an XML (in the form of tree), I require to create sub-tree out of it. For ex: <a> <b> <c>Hello</c> <d> <e>Hi</e> </a> Subtree would be <root> <a> <b> <c>Hello</c> </b> </a> <a> <d> <e>Hi</e> </d> </a> </root> What is the best XML library in python to do it? Any algorithm that already does this would also be helpful. Note: the XML doc won't be that big, it will easily fit in memory.

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• PHP file upload issue

  - by Varun

  I am working on a PHP based, ticket management system. While creating a ticket, one can upload an attachment. I want to put a limit (say 10 MB) per file upload. To implement this I plan the following- 1. In php.ini set post_max_size = 10M 2.In PHP script which receives the POST- Since the file is larger than post_max_size, $_FILES[] will be empty. But I can still check the content-length header and discard the upload, if size more than 10M. While testing this I tried uploading a file of 1 GB and analysed the http traffic and this is what I found. - the entire 1 GB data is first uploaded to a to the server temporarily and discarded once the http request completes. Though I couldn't exactly find out where the file was getting saved(as it was not there in the temporary directory in the server.), but my http traffic analyzer showed that the browser did send 1 GB data to the server. - the PHP script execution started only after completion of the http request(i.e after uploading the entire 1 GB) Now I have 2 concerns: a) People may exploit my server bandwidth by trying to upload large file, which I will have to discard anyways. b) Even worse, if someone starts uploading a huge file (say 100 GB), entire 100 GB data is first uploaded to the server temporarily, that means for that period, it will consume that much of memory on my server. What's the common solution for this. Am I missing something here?

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• If setUpBeforeClass() fails, test failures are hidden in PHPUnit's JUnit XML output

  - by Adam Monsen

  If setUpBeforeClass() throws an exception, no failures or errors are reported in the PHPUnit's JUnit XML output. Why? Example test class: <?php class Test extends PHPUnit_Framework_TestCase { public static function setUpBeforeClass() { throw new \Exception('masks all failures in xml output'); } public function testFoo() { $this->fail('failing'); } } Command line: phpunit --verbose --log-junit out.xml Test.php Console output: PHPUnit 3.6.10 by Sebastian Bergmann. E Time: 0 seconds, Memory: 3.25Mb There was 1 error: 1) Test Exception: masks all failures in xml output /tmp/pu/Test.php:6 FAILURES! Tests: 0, Assertions: 0, Errors: 1. JUnit XML output: <?xml version="1.0" encoding="UTF-8"?> <testsuites> <testsuite name="Test" file="/tmp/phpunit-broken/Test.php"/> </testsuites> More info: $ php --version PHP 5.3.10-1ubuntu3.1 with Suhosin-Patch (cli) (built: May 4 2012 02:21:57) Copyright (c) 1997-2012 The PHP Group Zend Engine v2.3.0, Copyright (c) 1998-2012 Zend Technologies with Xdebug v2.1.0, Copyright (c) 2002-2010, by Derick Rethans

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• Is C++ (one of) the best language to learn at first

  - by AlexV

  C++ is one of the most used programming language in the world since like 25+ years. My first job as programmer was in C++ and I coded in C++ everyday for nearly 4 years. Now I do mostly PHP, but I will forever cherish this C++ background. C++ has helped me understand many "under the hood" features/behaviors/restrictions of many other (and different) programming languages like PHP and Delphi. I'm a full time programmer for 6+ years now and since I have a quite varied programming background I often get questions by "newbies" as where to start to become a "good" programmer. I think C++ is one of the best language to start with because it gives you a real usefull experience that will last and will teach you how things work under the hood. It's not the easier one to learn for a newbie, but in my opinion it's one that will reward in the long term. I would like to know your opinion on this matter to add to my arguments when I guide "newbies". After this introduction, here's my question : Is C++ (one of) the best language to learn at first for you. Since it's subjective, I've marked this question as community wiki. EDIT: This question is not about why Java (or C# or any other language) is better than C++ to start with, it's about what's make C++ a good choice or not a good choice to learn as one of your firsts languages. For example, for me C++ made me understand how the memory works. Now today in many languages everything is managed by the garbadge collector and some people don't even know that. I'm glad I know how it works underneath and I think it can help you to write better code.

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• Creating a complex tree model in Qt

  - by Zeke

  I'm writing an IRC Client (yes another one). Long story short. I'm writing a Server dialogue that keeps a list of this: Identity Networks Channels Addresses I have 3 different list views that will be for the Networks, Channels and Addresses. When the user changes the Identity (combo box). The network listview will lookup all the networks for that specific Identity. After it loads up the Networks it will automatically select the first network and then load all the channels and addresses for that specific network. The problem is I want to have 3 views for 1 model, to minimise all the memory and the loading of data. So that it makes it much easier to manage and not do a bunch of work. If you'd look at QColumnView it's the same exact thing. But I don't need it to be on one exact page since the views are on entirely different tabs to make it easier to go through the Server dialogue. I'm wondering what will be the best way to go about handling this complexity. The information is stored in a SQLite database. I already have the classes written to extract and store it. Just the modelling is the painful part of this solution.

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• Spring + iBatis + Hessian caching

  - by ILya

  Hi. I have a Hessian service on Spring + iBatis working on Tomcat. I'm wondering how to cache results... I've made the following config in my sqlmap file: <sqlMap namespace="Account"> <cacheModel id="accountCache" type="MEMORY" readOnly="true" serialize="false"> <flushInterval hours="24"/> <flushOnExecute statement="Account.addAccount"/> <flushOnExecute statement="Account.deleteAccount"/> <property name="reference-type" value="STRONG" /> </cacheModel> <typeAlias alias="Account" type="domain.Account" /> <select id="getAccounts" resultClass="Account" cacheModel="accountCache"> fix all; select id, name, pin from accounts; </select> <select id="getAccount" parameterClass="Long" resultClass="Account" cacheModel="accountCache"> fix all; select id, name, pin from accounts where id=#id#; </select> <insert id="addAccount" parameterClass="Account"> fix all; insert into accounts (id, name, pin) values (#id#, #name#, #pin#); </insert> <delete id="deleteAccount" parameterClass="Long"> fix all; delete from accounts where id = #id#; </delete> </sqlMap> Then i've done some tests... I have a hessian client application. I'm calling getAccounts several times and after each call it's a query to DBMS. How to make my service to query DBMS only a first time (after server restart) getAccounts called and for the following calls to use a cache?

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• How to format the node_redis info function output?

  - by hh54188

  I want check the Redis info on my pc with node, so I use node_redis and run the info function: var redis = require("redis"), client = redis.createClient(); client.on("connect", function () { client.info(function (err, replay) { console.log(replay); }) }) but the response is un-format: `#Server\r\nredis_version:2.6.16\r\nredis_git_sha1:00000000\r\nredis_git_dirty:0\r\nredis_mode:standalone\r\nos:Linux 3.8.0-29-generic x86_64\r\narch_bits:64\r\nmultiplexing_api:epoll\r\ngcc_version:4.6.3\r\nprocess_id:2941\r\nrun_id:e60f261a6f4f6f081563a47961315eff6b1c005d\r\ntcp_port:6379\r\nuptime_in_seconds:1777\r\nuptime_in_days:0\r\nhz:10\r\nlru_clock:2040689\r\n\r\n# Clients\r\nconnected_clients:2\r\nclient_longest_output_list:0\r\nclient_biggest_input_buf:0\r\nblocked_clients:0\r\n\r\n# Memory\r\nused_memory:562584\r\nused_memory_human:549.40K\r\nused_memory_rss:2031616\r\nused_memory_peak:561784\r\nused_memory_peak_human:548.62K\r\nused_memory_lua:31744\r\nmem_fragmentation_ratio:3.61\r\nmem_allocator:jemalloc-3.2.0\r\n\r\n# Persistence\r\nloading:0\r\nrdb_changes_since_last_save:0\r\nrdb_bgsave_in_progress:0\r\nrdb_last_save_time:1383553917\r\nrdb_last_bgsave_status:ok\r\nrdb_last_bgsave_time_sec:-1\r\nrdb_current_bgsave_time_sec:-1\r\naof_enabled:0\r\naof_rewrite_in_progress:0\r\naof_rewrite_scheduled:0\r\naof_last_rewrite_time_sec:-1\r\naof_current_rewrite_time_sec:-1\r\naof_last_bgrewrite_status:ok\r\n\r\n# Stats\r\ntotal_connections_received:3\r\ntotal_commands_processed:5\r\ninstantaneous_ops_per_sec:0\r\nrejected_connections:0\r\nexpired_keys:0\r\nevicted_keys:0\r\nkeyspace_hits:0\r\nkeyspace_misses:0\r\npubsub_channels:0\r\npubsub_patterns:0\r\nlatest_fork_usec:0\r\n\r\n# Replication\r\nrole:master\r\nconnected_slaves:0\r\n\r\n# CPU\r\nused_cpu_sys:0.13\r\nused_cpu_user:0.19\r\nused_cpu_sys_children:0.00\r\nused_cpu_user_children:0.00\r\n\r\n# Keyspace\r\n' How can I turn it to an object? like: { redis_version:2.6.16, redis_git_sha1:00000000, redis_git_dirty:0, ...... } so that I can read each property's value, get information I need

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• Recursion in assembly?

  - by Davis

  I'm trying to get a better grasp of assembly, and I am a little confused about how to recursively call functions when I have to deal with registers, popping/pushing, etc. I am embedding x86 assembly in C++. Here I am trying to make a method which given an array of integers will build a linked list containing these integers in the order they appear in the array. I am doing this by calling a recursive function: insertElem (struct elem *head, struct elem *newElem, int data) -head: head of the list -data: the number that will be inserted at the end of a list -newElem: points to the location in memory where I will store the new element (data field) My problem is that I keep overwriting the registers instead of a typical linked list. For example, if I give it an array {2,3,1,8,3,9} my linked-list will return the first element (head) and only the last element, because the elements keep overwriting each other after head is no longer null. So here my linked list looks something like: 2--9 instead of 2--3--1--8--3--9 I feel like I don't have a grasp on how to organize and handle the registers. newElem is in EBX and just keeps getting rewritten. Thanks in advance!

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• Why does multiple sessions started on the same page gets the same session id?

  - by Calmarius

  I tryed the following: <?php session_name('user'); session_start(); // sets an 'user' cookie with session id. // This session stores the user's login data. // Its an ordinary session. $USERSESSION=$_SESSION; // saving this session $userSessId=session_id(); session_write_close(); //closing this session session_name('chatroom'); session_start(); // set a 'chatroom' cookie but contains the same session id and points to the same data :( . // This session would be used to store the chat text. This session would be // shared between all users joined in this chat room by setting the same session id for all members. // by calling session_regenerate_id would make a diffent session id for every user and it won't be a chat room anymore. ?> So I want to do a chat like thing with sessions. On the client side it would be done with ajax that polls this php page in every 5-10 seconds. Sessions may be cached in the server's memory so it can be accessible fast. I can store the chat in the database but my service runs on a free webhost which is limited, only 4 mysql connections allowed at a time which is almost nothing. I try to touch my database as least times as possible.

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• function returns after an XMLHttpRequest

  - by ashays

  Alright, I know questions like this have probably been asked dozens of times, but I can't seem to find a working solution for my project. Recently, while using jQuery for a lot of AJAX calls, I've found myself in a form of callback hell. Whether or not jQuery is too powerful for this project is beyond the scope of this question. So basically here's some code that shows what's going on: function check_form(table) { var file = "/models/"+table+".json"; var errs = {}; var xhr = $.getJSON(file, function(json) { for (key in json) { var k = key; var r = json[k]; $.extend(errs, check_item("#"+k,r)); } }); return errs; } And... as you can probably guess, I get an empty object returned. My original idea was to use some sort of onReadyStateChange idea that would return whenever the readyState had finally hit 4. This causes my application to hang indefinitely, though. I need these errors to decide whether or not the form is allowed to submit or not (as well as to tell the user where the errors are in the application. Any ideas? Edit. It's not the prettiest solution, but I've managed to get it to work. Basically, check_form has the json passed to it from another function, instead of loading it. I was already loading it there, too, so it's probably best that I don't continue to load the same file over and over again anyways. I was just worried about overloading memory. These files aren't absolutely huge, though, so I guess it's probably okay.

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• Weak hashmap with weak references to the values?

  - by Razor Storm

  I am building an android app where each entity has a bitmap that represents its sprite. However, each entity can be be duplicated (there might be 3 copies of entity asdf for example). One approach is to load all the sprites upfront, and then put the correct sprite in the constructors of the entities. However, I want to decode the bitmaps lazily, so that the constructors of the entities will decode the bitmaps. The only problem with this is that duplicated entities will load the same bitmap twice, using 2x the memory (Or n times if the entity is created n times). To fix this, I built a SingularBitmapFactory that will store a decoded Bitmap into a hash, and if the same bitmap is asked for again, will simply return the previously hashed one instead of building a new one. Problem with this, though, is that the factory holds a copy of all bitmaps, and so won't ever get garbage collected. What's the best way to switch the hashmap to one with weakly referenced values? In otherwords, I want a structure where the values won't be GC'd if any other object holds a reference to it, but as long as no other objects refers it, then it can be GC'd.

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• What's the best way to transfer a large dataset over a .NET web service?

  - by Malvineous

  I've inherited a C# .NET application which talks to a web service, and the web service talks to an Oracle database. I need to add an export function to the UI, to produce an Excel spreadsheet of some of the data. I have created a web service function to run a database query, load the data into a DataTable and then return it, which works fine for a small number of rows. However there is enough data in the full run that the client application locks up for a few minutes and then returns a timeout error. Obviously this isn't the best way to retrieve such a large dataset. Before I go ahead and come up with some dodgy way of splitting the call, I'm wondering if there is already something in place that can handle this. At the moment I'm thinking of a startExport function then repeatedly calling a next50Rows function until there is no data left, but because web services are stateless this means I'm going to have to keep some sort of ID number around and deal with the associated permissions. It would mean that I don't have to load the entire data set into the web server's memory though, which is one good thing. So if anyone knows a better way to retrieve a large amount of data (in a table format) over a .NET web service, please let me know!

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• Does The Clear Method On A Collection Release The Event Subscriptions?

  - by DaveB

  I have a collection private ObservableCollection<Contact> _contacts; In the constructor of my class I create it _contacts = new ObservableCollection<Contact>(); I have methods to add and remove items from my collection. I want to track changes to the entities in my collection which implement the IPropertyChanged interface so I subscribe to their PropertyChanged event. public void AddContact(Contact contact) { ((INotifyPropertyChanged)contact).PropertyChanged += new PropertyChangedEventHandler(Contact_PropertyChanged); _contacts.Add(contact); } public void AddContact(int index, Contact contact) { ((INotifyPropertyChanged)contact).PropertyChanged += new PropertyChangedEventHandler(Contact_PropertyChanged); _contacts.Insert(index, contact); } When I remove an entity from the collection, I unsubscribe from the PropertyChanged event. I am told this is to allow the entity to be garbage collected and not create memory issues. public void RemoveContact(Contact contact) { ((INotifyPropertyChanged)contact).PropertyChanged -= Contact_PropertyChanged; _contacts.Remove(contact); } So, I hope this is all good. Now, I need to clear the collection in one of my methods. My first thought would be to call _contacts.Clear(). Then I got to wondering if this releases those event subscriptions? Would I need to create my own clear method? Something like this: public void ClearContacts() { foreach(Contact contact in _contacts) { this.RemoveContact(contact); } } I am hoping one of the .NET C# experts here could clear this up for me or tell me what I am doing wrong.

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