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• mmap() for large file I/O?

  - by Boatzart

  I'm creating a utility in C++ to be run on Linux which can convert videos to a proprietary format. The video frames are very large (up to 16 megapixels), and we need to be able to seek directly to exact frame numbers, so our file format uses libz to compress each frame individually, and append the compressed data onto a file. Once all frames are finished being written, a journal which includes meta data for each frame (including their file offsets and sizes) is written to the end of the file. I'm currently using ifstream and ofstream to do the file i/o, but I am looking to optimize as much as possible. I've heard that mmap() can increase performance in a lot of cases, and I'm wondering if mine is one of them. Our files will be in the tens to hundreds of gigabytes, and although writing will always be done sequentially, random access reads should be done in constant time. Any thoughts as to whether I should investigate this further, and if so does anyone have any tips for things to look out for? Thanks!

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• What is design principle behind Servlets being Singleton

  - by Sandeep Jindal

  A servlet container "generally" create one instance of a servlet and different threads of the same instance to serve multiple requests. (I know this can be changed using deprecated SingleThreadModel and other features, but this is the usual way). I thought, the simple reason behind this is performance gain, as creating threads is better than creating instances. But it seems this is not the reason. On the other hand, creating instances have little advantage that developers never have to worry about thread safety. I am trying to understand the reason for this decision over the trade-off of thread-safety.

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• Is it possible to partition more than one way at a time in SQL Server?

  - by meeting_overload

  I'm considering various ways to partition my data in SQL Server. One approach I'm looking at is to partition a particular huge table into 8 partitions, then within each of these partitions to partition on a different partition column. Is this even possible in SQL Server, or am I limited to definining one parition column+function+scheme per table? I'm interested in the more general answer, but this strategy is one I'm considering for Distributed Partitioned View, where I'd partition the data under the first scheme using DPV to distribute the huge amount of data over 8 machines, and then on each machine partition that portion of the full table on another parition key in order to be able to drop (for example) sub-paritions as required.

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• Replication - syncronizing most of the data some of the time

  - by uncle brad

  I have some data that isn't properly "partitioned" (for lack of a better word). All inserts, processing and reporting happen on the same table. The bulk of the processing happens not long after the insert and not long after that it becomes immutable (we're talking days). I could do all inserts and processing on a new table that I replicate to the old table. When I detect that the data has become immutable I would delete the data from the new table, but I would edit the delete replication stored procedure so that the delete did not replicate. How bad an idea is this? It seems attractive at the moment (I haven't slept on it yet) because it might mitigate a performance problem with only very small changes to the application. It also seems like it might be a good way to shoot myself in the foot.

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• Android EditText and addTextChangedListener

  - by Alex

  im currently porting a database manager to android and due to performance reasons i like to update only propertys that have been modified. Im trying to do this with the addTextChangedListener in order to add modified entrys to a List, but my Program never enters any of its methods. EditText Et = (EditText) Editors.get(Prop.Name); Et.addTextChangedListener(new TextWatcher() { @Override public void afterTextChanged(Editable s) { // TODO Auto-generated method stub } @Override public void beforeTextChanged(CharSequence s, int start, int count, int after) { // TODO Auto-generated method stub } @Override public void onTextChanged(CharSequence s, int start, int before, int count) { // TODO Auto-generated method stub if(Prop.GetType() == Property.PROPTYPE.num) { float f = Float.parseFloat(s.toString()); Prop.FromString(f); } else { Prop.FromString(s.toString()); } propertiesToUpdate.add(Prop); }); Et.setText(Prop.ToString());

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• Easy Way for Non-Nerd to Manage Simple Site?

  - by Mark Evans

  Hi I'm not sure if this is an appropriate question for StackOverflow. I have a friend show wants a simple "Brochure Ware" web site. I could make it for him but it would be better if he could manage it himself. Are there any services out there that allow a non-technical person to create and maintain a very simple site? I'm thinking just a few pages - contact, about, home with some photos and general info. He also wants to sell some stuff but I'm going to suggest he does this using EBay but the web site would be a handy reference for potential customers who want to know more about him and his services. Thanks a lot! Cheers Mark

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• Is it possible to destroy a CDI scope?

  - by Matt Ball

  I'm working on a Java EE application, primarily JAX-RS with a JSF admin console, that uses CDI/Weld for dependency injection with @ApplicationScoped objects. Minor debugging issues aside, CDI has worked beautifully for this project. Now I need some very coarse-grained control over CDI-injected object lifecycles. I need the ability to: Remove an injected object from the application context, or Destroy/delete/clear/reset/remove the entire application context, or Define my own @ScopeType and implementing Context in which I could provide methods to perform one of the two above tasks. I'm fully aware that this is across, if not against, the grain of CDI and dependency injection in general. I just want to know Is this remotely possible? If yes, what is the easiest/simplest/quickest/foolproofiest way to get the job done?

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• Which testing method to go with? [Rails]

  - by yuval

  I am starting a new project for a client today. I have done some rails projects before but never bothered writing tests for them. I'd like to change that starting with this new project. I am aware there are several testing tools, but am a bit confused as to which I should be using. I heard of RSpec, Mocha, Webrat, and Cucamber. Please keep in mind I never really wrote any regular tests, so my knowledge of testing in general is quite limited. How would you suggest I get started? Thanks!

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• checking if records exists in DB, in single step or 2 steps?

  - by Sinan

  Suppose you want to get a record from database which returns a large data and requires multiple joins. So my question would be is it better to use a single query to check if data exists and get the result if it exists. Or do a more simple query to check if data exists then id record exists, query once again to get the result knowing that it exists. Example: 3 tables a, b and ab(junction table) select * from from a, b, ab where condition and condition and condition and condition etc... or select id from a, b ab where condition then if exists do the query above. So I don't know if there is any reason to do the second. Any ideas how this affects DB performance or does it matter at all?

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• How to deal with routing when developing a custom CMS in Codeigniter

  - by Ashley Ward

  Hi All - I’m a recent user of Codeigniter and am developing a simple backend CMS to manage pages. Based on a URL (in this example I have hidden “index.php”) : mysite.com/pagename I would like the system to detect if there is a value of “pagename” in my database, if there is, I need the system to re-route to a custom controller (eg: Pagemaker) and if there is no record called pagename, just do it’s normal thing (i.e. find a controller called pagename) Currently I have: $route['(:any)'] = "pagemaker/create/$1"; whereby all requests are forwarded to my custom function. However I want to change this structure so that if the page does NOT exist in the db, the traditional codeigniter request process is followed. Can anyone offer any advice about how to complete this? Or any advice about routing custom CMS’s in codeigniter in general?

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• Reselling Open Source Code licenced under GPL, MIT

  - by Tempe

  I want to use some open source code that is licenced under the following "GNU General Public License (GPL), MIT License". I want to include this code in a product that i will sell. Here is the code in particular What do i have to do to not get sued? :) I dont mind distributing the source code that i have modified, but i dont want the whole application open source. If i build the open source code into a library and open source the library can i link to it and not open the rest of my source?

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• Reading HttpURLConnection InputStream - manual buffer or BufferedInputStream?

  - by stormin986

  When reading the InputStream of an HttpURLConnection, is there any reason to use one of the following over the other? I've seen both used in examples. Manual Buffer: while ((length = inputStream.read(buffer)) > 0) { os.write(buf, 0, ret); } BufferedInputStream is = http.getInputStream(); bis = new BufferedInputStream(is); ByteArrayBuffer baf = new ByteArrayBuffer(50); int current = 0; while ((current = bis.read()) != -1) { baf.append(current); } EDIT I'm still new to HTTP in general but one consideration that comes to mind is that if I am using a persistent HTTP connection, I can't just read until the input stream is empty right? In that case, wouldn't I need to read the message length and just read the input stream for that length? And similarly, if NOT using a persistent connection, is the code I included 100% good to go in terms of reading the stream properly?

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• Find/parse server-side <?abc?>-like tags in html document

  - by Iggyhopper

  I guess I need some regex help. I want to find all tags like <?abc?> so that I can replace it with whatever the results are for the code ran inside. I just need help regexing the tag/code string, not parsing the code inside :p. <b><?abc print 'test' ?></b> would result in <b>test</b> Edit: Not specifically but in general, matching (<?[chars] (code group) ?>)

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• Using SQL Server for WSS 3.0 instead of Windows Internal database

  - by val

  Hi Folks, There are actually two related questions: is it possible or advisable to use a full blown stand-alone SQL server for SharePoint Services WSS3.0 instead of the supplied windows internal database it comes with? The client I am working for is asking to utilize their existent SQL server for all WSS content databases to possibly minimize admin effort and improve performance. As well, would you advise to install WSS on one physical server and the content database on another server? Any gain in performace? Practicality? ect. The default is WSS and all of its databases are installed on the same single server. We don't really need a farm setup of MOSS, because the WSS capabilities are enough for our needs. Thanks, Val

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• logging in scala

  - by IttayD

  In Java, the standard idiom for logging is to create a static variable for a logger object and use that in the various methods. In Scala, it looks like the idiom is to create a Logging trait with a logger member and mixin the trait in concrete classes. This means that each time an object is created it calls the logging framework to get a logger and also the object is bigger due to the additional reference. Is there an alternative that allows the ease of use of "with Logging" while still using a per-class logger instance? EDIT: My question is not about how one can write a logging framework in Scala, but rather how to use an existing one (log4j) without incurring an overhead of performance (getting a reference for each instance) or code complexity. Also, yes, I want to use log4j, simply because I'll use 3rd party libraries written in Java that are likely to use log4j.

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• .Net Logger (Write your own vs log4net/enterprise logger/nlog etc.)

  - by Jack

  I work for an IT department with about 50+ developers. It used to be about 100+ developers but was cut because of the recession. When our department was bigger there was an ambitious effort made to set up a special architecture group. One thing this group decided to do was create our own internal logger. They thought it was such a simple task that we could spend recources and do it ourselves. Now we are having issues with performance and difficulty viewing the logs generated and some employees are frustrated that we are spending recources on infrastructure stuff like this instead of focusing on serving our business and using stuff that already exists like log4net or Enterprise Logger. Can you assist me in listing up reasons why you should not create your own .net logger. Also reasons for why you should are welcome to get a fair point of view :)

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• iOS - NSURLConnection - Connecting to server and get Nonce

  - by Satyam svv

  I'm writing iOS application. There's a server related to some real estate. I've to send the following request to server to get the Nonce. GET /ptest/login HTTP/1.1 Method: GET User-Agent: MRIS API Testing Tool/2.0 Rets-Version: RETS/1.7 Accept: */* Host: ptest.mris.com:6103 Connection: keep-alive I'm using ASI HTTP with following code to post: [self setRequest:[ASIHTTPRequest requestWithURL:[NSURL URLWithString:@"/ptest/login"]]]; [request addRequestHeader:@"User-Agent" value:@"CARETS-General/1.0"]; [request addRequestHeader:@"Rets-Version" value:@"1.7"]; [request addRequestHeader:@"Connection" value:@"keep-alive"]; [request addRequestHeader:@"Accept" value:@"*/*"]; [request addRequestHeader:@"Host" value:"ptest.mris.com:6103"]; [request setDelegate:self]; [request setDidFinishSelector:@selector(topSecretFetchComplete:)]; [request setDidFailSelector:@selector(topSecretFetchFailed:)]; [request startAsynchronous]; The response that I'm getting is Error: Unable to start HTTP connection Can some one point me how to establish successful connection?

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• Prefered method for looping sound flash as3

  - by Brian Heylin

  Hi there, I'm having some issues with looping a sound in flash AS3, in that when I tell the sound to loop I get a slight delay at the end/beginning of the audio. The audio is clipped correctly and will play without a gap on garage band. I know that there are issues with sound in general in flash, bugs with encodings and the inaccuracies with the SOUND_COMPLETE event (And Adobe should be embarrassed with their handling of these issues) I have tried to use the built in loop argument in the play method on the Sound class and also react on the SOUND_COMPLETE event, but both cause a delay. But has anyone come up with a technique for looping a sound without any noticeable gap?

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• Alternative databases to use when putting IIS Logs into a database using LogParser

  - by Robin Day

  We have run some scripts that use LogParser to dump our IIS logs into a SQL Server database. We can then query this to get simple stats on hits, usage etc. It's also good when linking it to error log databases and performance counter database to compare usage with errors, etc. Having implemented this for just one system and for the last 2-3 weeks we already have a 5GB database with around 10 million records. This is making any queries to this database quite slow and will no doubt cause storage issues if we continue to log as we are. Can anyone suggest any alternative databases that we could use for this data that would be more efficient for such logs? I'd be particularly interested in any experience of Google's BigTable or Amazon's SimbleDB. Are either of these suitable for reporting queries? COUNTs, GROUP BYs, PIVOTs?

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• Recommend an algorithms exercise book?

  - by Parappa

  I have a little book called Problems on Algorithms by Ian Parberry which is chock full of exercises related to the study of algorithms. Can anybody recommend similar books? What I am not looking for are recommendations of good books related to algorithms or the theory of computation. Introduction to Algorithms is a good one, and of course there's the Knuth stuff. Ideally I want to know of any books that are light on instructional material and heavy on sample problems. In a nutshell, exercise books. Preferably dedicated to algorithms rather than general logic or other math problems. By the way, the Parberry book does not seem to be in print, but it is available as a PDF dowload.

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• mysql 2 primary key onone table

  - by Bharanikumar

  CREATE TABLE Orders -> ( -> ID SMALLINT UNSIGNED NOT NULL, -> ModelID SMALLINT UNSIGNED NOT NULL, -> Descrip VARCHAR(40), -> PRIMARY KEY (ID, ModelID) -> ); Basically May i know ... Shall we create the two primary key on one table... Is it correct... Bcoz as per sql law,,, We can create N number of unque key in one table, and only one primary key only is the LAW know... Then how can my system allowing to create multiple primary key ? Please advise .... what is the general rule

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• How to mark empty in a single element in a float array

  - by Vineeth Mohan

  I have a large float (primitive) array and not every element in the array is filled. How can i mark a particular element as EMPTY. I understand this can be achieved by some special symbols but still i would like to know the standard way. Even if i am using some special symbol , how will i handle a situation where the actual data item is the value of special symbol. In short my question is how to implement the NULL feature in a primitive type array in java. PS - The reason why i am not using Float object is to achieve a high memory and speed performance. Thanks Vineeth

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• Database EAV model, record listing as per search

  - by Shyam Sunder Verma

  I am building a dynamic application. I have three tables : ( EAV model style) 1: Items ( ItemId, ItemName) 2: Fields (FieldId, FieldName) 3: Field Values ( ItemID, FieldId, Value) Can you tell me how to write SINGLE query to get starting 20 records from ALL items where FieldId=4 is equal to TRUE. Expected Result : Columns = ItemID | Name | Field1 | Field2 | Field3 Each Row= ItemId | ItemName| Value1 | Value2 | Value3 Important concerns : 1: Number of fields per item are not known 2: I need one to write ONE query. 3: Query will be running on 100K records, so performance is concern. 4: I am using MySQL 5.0, so need solution for MYSQL Should I denormalize the tables if above query is not possible at all ? Any advice ?

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• How to call c# server side method through javascript

  - by Nimesh

  Hi, I need to call a c# server method through the javascript. I have a gridview in which i have a column with dropdown list. When i change the dropdown's value i need to call a server side method through javascript and change the value of another text box in the gridview. I am able to do this on the selected index change. but i am slightly worried about the performance. i am using asp.net c#. Please let me know how to do this.

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• Load Balancing and Failover for Read-Only PostgreSQL Database

  - by Eric J.

  Scenario Multiple application servers host web services written in Java, running in SpringSource dm Server. To implement a new requirement, they will need to query a read-only PostgreSQL database. Issue To support redundancy, at least two PostgreSQL instances will be running. Access to PostgreSQL must be load balanced and must auto-fail over to currently running instances if an instance should go down. Auto-discovery of newly running instances is desirable but not required. Research I have reviewed the official PostgreSQL documentation on this issue. However, that focuses on the more general case of read/write access to the database. Top google results tend to lead to older newsgroup messages or dead projects such as Sequoia or DB Balancer, as well as one active project PG Pool II Question What are your real-world experiences with PG Pool II? What other simple and reliable alternatives are available?

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