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• MsSql Server high Resource Waits and Head Blocker

  - by MartinHN

  Hi I have a MS SQL Server 2008 Standard installation running a database for a webshop. The current size of the database is 2.5 GB. Running on Windows 2008 Standard. Dual Intel Xeon X5355 @ 2.00 GHz. 4 GB RAM. When I open the Activity Monitor, I see that I have a Wait Time (ms/sec) of 5000 in the "Other" category. In the Processes list, all connections from the webshop, the Head Blocker value is 1. I see every day that when I try to access the website, it can take 20-30 secs before it even starts to "work". I know that it is not network latency. (I have a 301 redirect from the same server that is executed instantly). When the first request has been served, it seems as if it's not a sleep anymore and every subsequent request is served instantly with the speed of light. The problem was worse two weeks ago, until I changed every query to include WITH (NOLOCK). But I still experience the problem, and the Wait times in the Activity Monitor is about the same. The largest table (Images) has 32764 rows (448576 KB). Some tables exceed 300000 rows, thought they're much smaller in size than the Images table. I have the default clustered index for every primary key column, only. Any ideas?

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• Audio processing in C# or C++

  - by melculetz

  Hi, I would like to create an application that uses AI techniques and allows the user to record a part of a song and then tries to find that song in a database of wav files. I would have liked to use some already existing libraries for the audio processing part. So, could you recommend any libraries in C# which can read a wav file, get input from microphone, have some audio filters (low pass, high pass, FFT etc) and maybe have the ability to plot the audio signal as well. I would prefer to develop in C#, but if there aren't good libraries for audio processing, I guess I could work in C++ as well. As far as I know, Mathlab already has the above mentioned functionalities, but I can't use it in my application.

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• feature extraction from acoustic signals

  - by Dolphin

  Hi everyone, It's been a while. I found APIs in Java for extracting features from acoustic audio files and symbolic files separately. But now I have a problem in mapping from low level wav audio features to high level midi features. i.e. I need to write the extracted wav audio features on to midi format. But I cannot think of anything even close to it. Can someone pls provide me some insight as in how I can approach this. Greatly appreciate your responses. Advance thanks

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• MySQL - Sort on a calculated value based on two dates

  - by Petter Magnusson

  I have the following problem that needs to be solved in a MySQL query: Fields info - textfield date1 - a date field date2 - a date field offset1 - a text field with a number in the first two positions, example "10-High" offset2 - a text field with a number in the first two positions, example "10-High" I need to sort the records by the calculated "sortvalue" based on the current date (today): If today=date2 then sortvalue=offset1*10+offset2*5+1000 else sortvalue=offset1*10+offset2*5 I have quite good understanding of basic SQL with joins etc, but this I am not even sure if its possible...if it helps I could perhaps live with a single formula giving the same sort of effect as the IFs do....ie. before date1 = low value, after date2 = high value... Rgds PM

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• How cross-platform .Net framework really is?

  - by Ivan

  What is normally to be done to run a WinForms application on a Mac or Linux machine? a. Just copy and run (assuming they have a Framework installed). b. Rebuild. c. Cosmetic source code modifications. d. Heavy source code modifications and forms redesign. Assuming that the application is developed as 100% managed C# 3 code by means Visual C# Express or Visual Studio 2008 targeting .Net Framework 3.5, developed without using any 3-rd party components/libraries, without encapsulating nonmanaged code or any low-level hacks - only standard Microsoft-documented .Net Framework C# API used). Or the same conditions but C# 4 language, .Net Framework 4 and Visual Studio 2010.

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• multiple ajax requests with jquery

  - by Emil

  I got problems with the async nature of Javascript / JQuery. Lets say the following (no latency is counted for, in order to not make it so troublesome); I got three buttons (A, B, C) on a page, each of the buttons adds an item into a shopping cart with one ajax-request each. If I put an intentional delay of 5 seconds in the serverside script (PHP) and pushes the buttons with 1 second apart, I want the result to be the following: Request A, 5 seconds Request B, 6 seconds Request C, 7 seconds However, the result is like this Request A, 5 seconds Request B, 10 seconds Request C, 15 seconds This have to mean that the requests are queued and not run simultaneously, right? Isnt this opposite to what async is? I also tried to add a random get-parameter to the url in order to force some uniqueness to the request, no luck though. I did read a little about this. If you avoid using the same "request object (?)" this problem wont occure. Is it possible to force this behaviour in JQuery? This is the code that I am using $.ajax( { url : strAjaxUrl + '?random=' + Math.floor(Math.random()*9999999999), data : 'ajax=add-to-cart&product=' + product, type : 'GET', success : function(responseData) { // update ui }, error : function(responseData) { // show error } }); I also tried both GET and POST, no difference. I want the requests to be sent right when the button is clicked, not when the previous request is finnished. I want the requests to be run simultaneously, not in a queue.

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• Custom Validator and specifying type of message

  - by user102533

  I have a custom validation in the enterprise validation block. The DoValidate method is as shown below. protected override void DoValidate(Double objectToValidate, object currentTarget, string key, ValidationResults validationResults) { if (!IsSalMoreThanMinWage(objectToValidate)) { //Here I need to mark this message as a "Warning" LogValidationResult(validationResults, "Salary is too low for this state", currentTarget, key); } } I'd need to mark this validation failure as a "warning" message. In the front end, when I iterate through the ValidationResults collection and grab a ValidationResult object, I would need to identify and group different types of messages and render them differently. My question is - how do I mark a failure as a warning?

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• Analyzing Web Application Speed

  - by Amy

  I'm a bit confused because the logical/programmer brain in me says that if all things are constant, the speed of a function must be constant. I am working on a PHP web application with jqGrid as a front end for showing the data. I am testing on my personal computer, so network traffic does not apply. I make an HTTP request to a PHP function, it returns the data, and then jqGrid renders it. What has me befuddled is that sometimes, Firebug reports that this is taking 300-600 milliseconds sometimes, and sometimes, it's taking 3.68 seconds. I can run the request over and over again, with very radically different response times. The query is the same. The number of users on the system is the same. No network latency. Same code. I'm not running other applications on the computer while testing. I could understand query caching improving performance on subsequent requests, but the speed is just fluctuating wildly with no rhyme or reason. So, my question is, what else can cause such variability in the response time? How can I determine what's doing it? More importantly, is there any way to get things more consistent?

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• Can Hibernate default a Null String to Empty String

  - by sliver

  In our application we are pulling data from a DB2 mainframe database. If the database has "low values" in a field, hibernate sends a "null" value in the object. This occurs even if the column is defined as "not null". As we are doing XML parsing on this, Castor is having trouble with it. I would like to fix this in Hibernate. Also, all of the hibernate hbm files are generated, so we can't mess with them (they are regened from time to time.) Any way to intercept all Strings and replace nulls with ""?

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• Rails: Display Maintenance Page if No Database Connection Available

  - by RobB

  I'm looking for a solution that will allow my rails app to render a user-friendly maintenance page when there is no Mysql server available to connect to. Normally a Mysql::Error is thrown from the mysql connection adapter in active_record. Something like: /!\ FAILSAFE /!\ Wed May 26 11:40:14 -0700 2010 Status: 500 Internal Server Error Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' Is there a low-overhead way to catch this error and render a maintenance page instead? I'm assuming that since connections are actually made in the active_record mysql adapter the app never makes it to the controller stack before it throws the error, so you can't catch it in a controller. Any input would be greatly appreciated.

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• How do I read the cache of Chrome and Firefox programmatically on the Mac?

  - by John Gallagher

  Background I want to access the cache of Chrome and Firefox in my Cocoa application. I need to get the HTML for pages accessed recently. Safari is a piece of cake - all this information is available in SQLite data stores, but not so in Chrome and Firefox. The Problem For Firefox, the cache is in /Library/Caches/Firefox/Profiles/xxx.default/Cache with filenames _CACHE_001_ _CACHE_002_ _CACHE_003_ and _CACHE_MAP_ For Chrome, the cache is in /Library/Caches/Google/Chrome/Default/Cache with filenames data_0 data_1 data_2 and data_3 What I've tried The only article I can find that sheds any light on what format these caches are in is here. It recommends a Cache Viewer tool, but doesn't explain how one might do this programmatically. Questions Is there any way of reconstructing this data using command line tools or the Cocoa framework? Or is it much too low level? Is there another way of getting at the HTML of recent web pages that I don't know about?

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• Learning C++ from scratch in Visual Studio?

  - by flesh

  I need to get up to speed with C++ quite quickly (I've never used it previously) - is learning through Visual Studio (i.e. Managed C++) going to be any use? Or will I end up learning the extensions and idiosyncracies of C++ in VS, rather then the language itself? If learning in VS is not recommended, what platform / IDE do you guys suggest? Edit: Can anyone elaborate on what VS will hide or manage for me when coding unmanaged C++? I really need to be learning things like pointers, garbage collection and all the nuts and bolts of the low level language.. does VS abstract or hide any of this kind of stuff from you? Thanks for all the suggestions..

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• dvi generation: no bounding box

  - by Akshey

  Hi, I wrote a research paper in latex and generated pdf using kile. It worked perfectly well. Now conference people are asking for dvi file also. But Kile's quick build process does not give a dvi file, but its 'Latex' compile process does. So I tried to compile the document, and it gave errors for includegraphics saying figure not found. When I append the correct extensions to the image names, that errors stopped coming but new errors came "bounding box is missing". I added bounding box values and now DVI file is being generated. My questions are: I have tried giving very high and low bounding box values but there is no deformation in the PDF. Why? Can I generate a DVI without giving bounding box values? Thanks and regards, Akshey

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• How to achieve high availability?

  - by tanyehzheng

  My boss wants to have a system that takes into concern of continent wide catastrophic event. He wants to have two servers in US and two servers in Asia (1 login server and 1 worker server in each continent). In the event that earthquake breaks the connection between the two continents, both should work alone. When the connection is revived, they should sync each other back to normal. External cloud system not allowed as he has no confidence. The system should take into account of scalability which means addition of new servers should be easy to configure. The servers should be load balanced. The connection between the servers should be very secure(encrypted and send through SSL although SSL takes care of encryption). The system should let one and only one user log in with one account. (beware of latency between continent and two users sharing account may reach both login server at the same time) Please help. I'm already at the end of my wit. Thank you in advance.

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• Utilising cssText to set styles with JavaScript

  - by Rajat

  I was going through Nicholas Zakas presentation on JavaScript here : http://www.slideshare.net/nzakas/writing-efficient-javascript (slide number: 89/139) He recommends using cssText property whenever you are setting a bunch of styles through JavaScript. The best solution is obviously adding those styles to a class and then using JS to add the classname to an element.However, in many situations, We resort to just setting the properties directly within JS when the number of properties are low. It seems from his presentation that using cssText property would be more efficient in such scenarios.I tried to look up more on the property but couldn't find much information. Has anyone used the 'cssText' property ? It would be great to have some more technical info on how the property helps.

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• Generalized plugable caching pattern?

  - by BCS

  Given that it's one of the hard things in computer science, does anyone know of a way to set up a plugable caching strategy? What I'm thinking of would allow me to write a program with minimal thought as to what needs to be cached (e.i. use some sort of boiler-plate, low/no cost pattern that compiles away to nothing anywhere I might want caching) and then when things are further along and I know where I need caching I can add it in without making invasive code changes. As an idea to the kind of solution I'm looking for; I'm working with the D programing language (but halfway sane C++ would be fine) and I like template.

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• Socket server stops accepting connections after a period of time

  - by Rob

  We have an async socket server written in C#. (running on Windows Web Server 2008) It works flawlessly up until it stop accepting new connections for an unknown reason. We have about 200 concurrent connections on average, however we keep a count of both connections created and connections dropped. These figures can reach as high as 10,000 or as low as only 1000 before it just stops! It can run for up to around 8 hours sometimes before it stops or it can run for about half hour, at the moment it's running for about an hour before we have another application bring it back up automatically when that can't connect (not exactly ideal). It doesn't appear like we're running out of sockets as we're closing them properly, we're also logging all errors and nothing is happening immediately before it stops. We can figure this out. Does anyone have any ideas what might be going on? I can paste code, but it generally just the same old async beginaccept/send code you see everywhere.

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• Memory Allocation - Arduino

  - by Joey Arnold Andres

  I'm new to this low level stuff. I'm currently learning arduino. I'm currently using an Arduino Mega 2560 and in our course we are practicing memory management. I'm a pro at memory management in pc but somehow I'm having crazy problems here in arduino. For instance: The arduino have 8192B, I'm trying to overflow it with uint_16 so I made an array of 8192/16 which is 512. so I did uint16_t A[512+1]; Well I expected that to cause an overflow. What is wrong with my concept?

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• Understanding run time code interpretation and execution

  - by Bob

  I'm creating a game in XNA and was thinking of creating my own scripting language (extremely simple mind you). I know there's better ways to go about this (and that I'm reinventing the wheel), but I want the learning experience more than to be productive and fast. When confronted with code at run time, from what I understand, the usual approach is to parse into a machine code or byte code or something else that is actually executable and then execute that, right? But, for instance, when Chrome first came out they said their JavaScript engine was fast because it compiles the JavaScript into machine code. This implies other engines weren't compiling into machine code. I'd prefer not compiling to a lower language, so are there any known modern techniques for parsing and executing code without compiling to low level? Perhaps something like parsing the code into some sort of tree, branching through the tree, and comparing each symbol and calling some function that handles that symbol? (Wild guessing and stabbing in the dark)

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• What is a good DBMS for archiving?

  - by Thomas.Winsnes

  I've been stuck in a MsSql/MySql world now for a few years, and I've decided to spread my wings a little further. At the moment I'm researching which DBMS is good at things needed when archiving data. Eg. lots of writes and low reads. I've seen the NoSQL crusade, but I have a very RDBMS mindset, so I'm a bit skeptical. Anyone have any suggestions? Or even any pointers to where there are some benchmarks etc for this kind of stuff. Thank you :) Thomas

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• How to scale a PHP application (servers, mysql, memcache)

  - by Stéphane Goetz

  Hi, I'm currently creating a website for a social project in switzerland. And before there is an overflow of user, I want to prepare the application to scale. I answered by myself many questions but some are left. I explain what I want to do. First at the beginnning, the Application will have only one server (short time) with DNS, PHP, Mysql, Data, and memcache. Second Then I will split them in two DNS, Mysql, memcache Data, PHP Third Here is the problem, I don't know how to do it exactly here to keep the application running well. I could do : Front : Load Balancer, memcache, DNS Web 1 : PHP, DATA Web 2 : PHP, DATA Mysql This would be the scheme, all PHP sessions are kept in the DB. BUT, how do I sync the data? do I run a Rsync to keep them up to date. do I put them on a separate disk (network disk) to be sure ? but in this case, how can I do in case of user uploads ? and if the website gets more success and we have to go on greater structures, would'nt it create some latency on updates ? or would it be a good thing to go directly to amazon's web services ? some infos I use codeigniter as Framework. I use linux as webserver (distribution not chosen now, but should be Debian) Thanks in advance for your answers.

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• Trying to Unit Test A Class That Makes DB Queries Using Hibernate And Can't Get Session Created...

  - by Jared Michaels

  I am trying to implement JUnit tests for a class that performs DB queries using Hibernate. When I create the class under test, I get access to the session through the factory by doing the following: InitialContext context = new InitialContext(); sessionFactory = (SessionFactory) context.lookup(hibernateContext); This works fine when I deploy this to JBoss 5.1. I am trying to figure out how to get this to work with my JUnit test. I keep getting an exception stating that I "Need to specify class name in environment or system property, or as an applet parameter, or in an application resource file: java.naming.factory.initial". I've searched high and low but haven't been able to find any information about what specifically I need to do to get this to work. I am not using Spring or any frameworks, just plain old Java and JUnit.

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• Is this a "valid" css image replacement technique?

  - by user278457

  I just came up with this, it seems to work in all modern browsers, I just tested it then on (IE8/compatibility, Chrome, Safari, Moz) HTML <img id="my_image" alt="my text" src="images/small_transparent.gif" /> CSS #my_image{ background-image:url('images/my_image.png'); width:100px; height:100px;} Pro's: image alt text is best-practice for accessibility/seo no extra HTML markup, and the css is pretty minimal too gets around the css on/images off issue where "text-indent" techniques hide text from low bandwidth users The biggest disadvantage that I can think of is the css off/images on situation, because you'll only send a transparent gif. I'd like to know, who uses images without stylesheets? some kind of mobile phone or something? I'm making some sites for clients in regional Australia (hundreds of km from the nearest city), where many users will be suffering from dial-up connections, and often outdated browsers too, so the "images off" issue is an important consideration. are there any other side effects with this technique that I haven't considered?

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• Running out of memory but not seeing excessive object allocation in Instruments

  - by Scotty Allen

  I have an iPad app that's crashing due to low memory. However, Instruments doesn't show any significant amount of memory allocated using ObjectAlloc - it stays under 1MB for the lifetime of the application. Leaks shows less than 1kB leaked over the course of the run. Memory monitor shows the free memory on the devices drop significantly with use, eventually dropping to the point that it's out of memory. Here's a screenshot from Instruments: I'm totally stumped. As far as I can tell, this basically says that as far as my app is concerned, I'm never using more than about 750kB, but that the device is still running out of physical memory, which is causing my app to crash/force exit. I'm new to debugging memory issues with XCode. Am I measuring this wrong? Is there another way to see where this memory is going?

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• How to approach parallel processing of messages?

  - by Dan

  I am redesigning the messaging system for my app to use intel threading building blocks and am stumped trying to decide between two possible approaches. Basically, I have a sequence of message objects and for each message type, a sequence of handlers. For each message object, I apply each handler registered for that message objects type. The sequential version would be something like this (pseudocode): for each message in message_sequence <- SEQUENTIAL for each handler in (handler_table for message.type) apply handler to message <- SEQUENTIAL The first approach which I am considering processes the message objects in turn (sequentially) and applies the handlers concurrently. Pros: predictable ordering of messages (ie, we are guaranteed a FIFO processing order) (potentially) lower latency of processing each message Cons: more processing resources available than handlers for a single message type (bad parallelization) bad use of processor cache since message objects need to be copied for each handler to use large overhead for small handlers The pseudocode of this approach would be as follows: for each message in message_sequence <- SEQUENTIAL parallel_for each handler in (handler_table for message.type) apply handler to message <- PARALLEL The second approach is to process the messages in parallel and apply the handlers to each message sequentially. Pros: better use of processor cache (keeps the message object local to all handlers which will use it) small handlers don't impose as much overhead (as long as there are other handlers also to be run) more messages are expected than there are handlers, so the potential for parallelism is greater Cons: Unpredictable ordering - if message A is sent before message B, they may both be processed at the same time, or B may finish processing before all of A's handlers are finished (order is non-deterministic) The pseudocode is as follows: parallel_for each message in message_sequence <- PARALLEL for each handler in (handler_table for message.type) apply handler to message <- SEQUENTIAL The second approach has more advantages than the first, but non-deterministic ordering is a big disadvantage.. Which approach would you choose and why? Are there any other approaches I should consider (besides the obvious third approach: parallel messages and parallel handlers, which has the disadvantages of both and no real redeeming factors as far as I can tell)? Thanks!

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