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  • How can I cluster short messages [Tweets] based on topic ? [Topic Based Clustering]

    - by Jagira
    Hello, I am planning an application which will make clusters of short messages/tweets based on topics. The number of topics will be limited like Sports [ NBA, NFL, Cricket, Soccer ], Entertainment [ movies, music ] and so on... I can think of two approaches to this Ask for users to tag questions like Stackoverflow does. Users can select tags from a predefined list of tags. Then on server side I will cluster them on based of tags. Pros:- Simple design. Less complexity in code. Cons:- Choices for users will be restricted. Clusters will not be dynamic. If a new event occurs, the predefined tags will miss it. Take the message, delete the stopwords [ predefined in a dictionary ] and apply some clustering algorithm to make a cluster and depending on its popularity, display the cluster. The cluster will be maintained according to its sustained popularity. New messages will be skimmed and assigned to corresponding clusters. Pros:- Dynamic clustering based on the popularity of the event/accident. Cons:- Increased complexity. More server resources required. I would like to know whether there are any other approaches to this problem. Or are there any ways of improving the above mentioned methods? Also suggest some good clustering algorithms.I think "K-Nearest Clustering" algorithm is apt for this situation.

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  • What makes an effective UI for displaying versioning of structured hierarchical data

    - by Fadrian Sudaman
    Traditional version control system are displaying versioning information by grouping Projects-Folders-Files with Tree view on the left and details view on the right, then you will click on each item to look at revision history for that configuration history. Assuming that I have all the historical versioning information available for a project from Object-oriented model perspective (e.g. classes - methods - parameters and etc), what do you think will be the most effective way to present such information in UI so that you can easily navigate and access the snapshot view of the project and also the historical versioning information? Put yourself in the position that you are using a tool like this everyday in your job like you are currently using SVN, SS, Perforce or any VCS system, what will contribute to the usability, productivity and effectiveness of the tool. I personally find the classical way for display folders and files like above are very restrictive and less effective for displaying deep nested logical models. Assuming that this is a greenfield project and not restricted by specific technology, how do you think I should best approach this? I am looking for idea and input here to add values to my research project. Feel free to make any suggestions that you think is valuable. Thanks again for anyone that shares their thoughts.

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  • Practical non-image based CAPTCHA approaches?

    - by Jeff Atwood
    It looks like we'll be adding CAPTCHA support to Stack Overflow. This is necessary to prevent bots, spammers, and other malicious scripted activity. We only want human beings to post or edit things here! We'll be using a JavaScript (jQuery) CAPTCHA as a first line of defense: http://docs.jquery.com/Tutorials:Safer_Contact_Forms_Without_CAPTCHAs The advantage of this approach is that, for most people, the CAPTCHA won't ever be visible! However, for people with JavaScript disabled, we still need a fallback and this is where it gets tricky. I have written a traditional CAPTCHA control for ASP.NET which we can re-use. However, I'd prefer to go with something textual to avoid the overhead of creating all these images on the server with each request. I've seen things like.. ASCII text captcha: \/\/(_)\/\/ math puzzles: what is 7 minus 3 times 2? trivia questions: what tastes better, a toad or a popsicle? Maybe I'm just tilting at windmills here, but I'd like to have a less resource intensive, non-image based <noscript> compatible CAPTCHA if possible. Ideas?

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  • IE8 removes background-color of header row of Asp:Gridview

    - by Hitesh Riziya
    I am using Asp.net 4.0 GridView control to display data from database. I have applied the inbuilt theme to GridView. <asp:GridView ID="gv" runat="server" CellPadding="4" EmptyDataText="No records found." ForeColor="#333333" OnRowCommand="gv_RowCommand" Width="99%" OnPageIndexChanging="gv_PageIndexChanged" PageSize="50" AllowPaging="True" GridLines="None" AutoGenerateColumns="true"> <AlternatingRowStyle BackColor="White" /> <EditRowStyle BackColor="#7C6F57" /> <FooterStyle BackColor="#1C5E55" Font-Bold="True" ForeColor="White" /> <HeaderStyle CssClass="GridHeader" BackColor="#1C5E55" Font-Bold="True" ForeColor="White" HorizontalAlign="Left" /> <PagerStyle BackColor="#666666" ForeColor="White" HorizontalAlign="Center" /> <RowStyle BackColor="#E3EAEB" /> <SelectedRowStyle BackColor="#C5BBAF" Font-Bold="True" ForeColor="#333333" /> <SortedAscendingCellStyle BackColor="#F8FAFA" /> <SortedAscendingHeaderStyle BackColor="#246B61" /> <SortedDescendingCellStyle BackColor="#D4DFE1" /> <SortedDescendingHeaderStyle BackColor="#15524A" /></asp:GridView> I tried setting the CSS forcefully in my Master page .GridHeader { background-color:#1C5E55 !important;} But I am still missing the background-color. I can see the backgroundcolor applied to grid (for less-than 1 sec) while the page loading the js/css content NOTE: I already tried clearing cache of IE, ctrl + F5, shift + reload etc. Here is sample page of my issue. http://vd2.weenggs.com/Items.aspx email: [email protected] pass: test Thanks

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  • Why does Android allocate more memory than needed when loading images

    - by Simon
    Folks, I don't think that this is a duplicate and is NOT one of those how do I avoid OOMs questions. This is a genuine quest for knowledge so hold off on those down votes please... Imagine I have a JPEG of 500x500 pixels. I load it as ARGB_8888 which is as "bad as it gets". I would expect Android to allocate 500x500x4 bytes = a little under 1MB however, look at a heap dump and you will see that Android allocates significantly more, often factors of 5-10 times greater. You frequently see questions on here about OOMS where the stack trace shows a heap request of say 15MB and it is ALWAYS much larger than is required simply to hold the bytes of the image. The OP usually catches some downvotes then is bombarded with stock answers and comments about using less memory (thanks Romain!) and in scaling. I think there is more than meets the eye here. Anybody know why this is? If there is no apparent answer, I will put together an SSCCE if it helps. PS. I assume that JPEG vs PNG etc is irrelevant since we're talking about the memory usage of the backing bitmap which is simply x times y times BPP - or am I being slow?

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  • Significance in R

    - by Gemsie
    Ok, this is quite hard to explain, but I'm at a complete loss what to do. I'm a relative newcomer to R and although I can completely admire how powerful it is, I'm not too good at actually using it.... Basically, I have some very contrived data that I need to analyse (it wasn't me who chose this, I can assure you!). I have the right and left hand lengths of lots of people, as well as some numeric data that shows their sociability. Now I would like to know if people who have significantly different lengths of hand are more or less sociable than those who have the same (leading into the research that 'symmetrical' people are more sociable and intelligent, etc. I have got as far as loading the data into R, then I have no idea where to go from there. How on Earth do I start to separate those who are close to symmetrical to those who aren't to then start to do the analysis? Ok, using Sasha's great advice, I did the cor.test and got the following: Pearson's product-moment correlation data: measurements$l.hand - measurements$r.hand and measurements$sociable t = 0.2148, df = 150, p-value = 0.8302 alternative hypothesis: true correlation is not equal to 0 95 percent confidence interval: -0.1420623 0.1762437 sample estimates: cor 0.01753501 I have never used this test before, so am unsure how to intepret it...you wouldn't think I was on my fourth Scientific degree would you?! :(

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  • Python: Does one of these examples waste more memory?

    - by orokusaki
    In a Django view function which uses manual transaction committing, I have: context = RequestContext(request, data) transaction.commit() return render_to_response('basic.html', data, context) # Returns a Django ``HttpResponse`` object which is similar to a dictionary. I think it is a better idea to do this: context = RequestContext(request, data) response = render_to_response('basic.html', data, context) transaction.commit() return response If the page isn't rendered correctly in the second version, the transaction is rolled back. This seems like the logical way of doing it albeit there won't likely be many exceptions at that point in the function when the application is in production. But... I fear that this might cost more and this will be replete through a number of functions since the application is heavy with custom transaction handling, so now is the time to figure out. If the HttpResponse instance is in memory already (at the point of render_to_response()), then what does another reference cost? When the function ends, doesn't the reference (response variable) go away so that when Django is done converting the HttpResponse into a string for output Python can immediately garbage collect it? Is there any reason I would want to use the first version (other than "It's 1 less line of code.")?

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  • Fastest XML parser for small, simple documents in Java

    - by Varkhan
    I have to objectify very simple and small XML documents (less than 1k, and it's almost SGML: no namespaces, plain UTF-8, you name it...), read from a stream, in Java. I am using JAXP to process the data from my stream into a Document object. I have tried Xerces, it's way too big and slow... I am using Dom4j, but I am still spending way too much time in org.dom4j.io.SAXReader. Does anybody out there have any suggestion on a faster, more efficient implementation, keeping in mind I have very tough CPU and memory constraints? [Edit 1] Keep in mind that my documents are very small, so the overhead of staring the parser can be important. For instance I am spending as much time in org.xml.sax.helpers.XMLReaderFactory.createXMLReader as in org.dom4j.io.SAXReader.read [Edit 2] The result has to be in Dom format, as I pass the document to decision tools that do arbitrary processing on it, like switching code based on the value of arbitrary XPaths, but also extracting lists of values packed as children of a predefined node. [Edit 3] In any case I eventually need to load/parse the complete document, since all the information it contains is going to be used at some point. (This question is related to, but different from, http://stackoverflow.com/questions/373833/best-xml-parser-for-java )

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  • iPodMusicPlayer playbackState inaccurate after odd conditions

    - by Shane Costello
    I have a simple music player app that runs into a really weird problem. First of all, while playing music and in the locked state, I allow the user to double click the Home button and use the locked iPod music controls. I did notice however that while in the locked state, my app doesn't receive any of its registered notifications. For the most part, this is fine anyway. But, if the user is playing music for at least 15 minutes (I'm not sure why but any less and this problem doesn't occur) while in the locked state, and using some kind of headphone or aux jack, then unplugs the headphone/aux jack while the device is still playing music, the iPodMusicPlayer will auto-pause. Which is exactly what I would want it to do, but after this happens, when the user unlocks their device and gives focus to the app again, the iPodMusicPlayer's playbackState is inaccurate. - (IBAction)playPause:(id)sender { if ([musicPlayer playbackState] == MPMusicPlaybackStatePlaying) { [musicPlayer pause]; } else { [musicPlayer play]; } } where musicPlayer = [MPMusicPlayerController iPodMusicPlayer]. Under normal circumstances, this runs perfectly fine. But after these conditions, my breakpoint will hit the condition for MPMusicPlaybackStatePlaying while the music is paused, and vice versa. The only way I've been able to fix this is to either make a new selection of music or to terminate the app and reopen. I've tried tons of a workarounds to fix this problem programmatically, but nothing turns out a 100% bug free fix. Does anyone have any clue as to why this happens in the first place?

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  • Apache console accesses network drives, service does not?

    - by danspants
    I have an apache 2.2 server running Django. We have a network drive T: which we need constant access to within our Django app. When running Apache as a service, we cannot access this drive, as far as any django code is concerned the drive does not exist. If I add... <Directory "t:/"> Options Indexes FollowSymLinks MultiViews AllowOverride None Order allow,deny allow from all </Directory> to the httpd.conf file the service no longer runs, but I can start apache as a console and it works fine, Django can find the network drive and all is well. Why is there a difference between the console and the service? Should there be a difference? I have the service using my own log on so in theory it should have the same access as I do. I'm keen to keep it running as a service as it's far less obtrusive when I'm working on the server (unless there's a way to hide the console?). Any help would be most appreciated.

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  • Deserialize xml which uses attribute name/value pairs

    - by Bodyloss
    My application receives a constant stream of xml files which are more or less a direct copy of the database record <record type="update"> <field name="id">987654321</field> <field name="user_id">4321</field> <field name="updated">2011-11-24 13:43:23</field> </record> And I need to deserialize this into a class which provides nullable property's for all columns class Record { public long? Id { get; set; } public long? UserId { get; set; } public DateTime? Updated { get; set; } } I just cant seem to work out a method of doing this without having to parse the xml file manually and switch on the field's name attribute to store the values. Is their a way this can be achieved quickly using an XmlSerializer? And if not is their a more efficient way of parsing it manually? Regards and thanks My main problem is that the attribute name needs to have its value set to a property name and its value as the contents of a <field>..</field> element

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  • Drawing and filling different polygons at the same time in MATLAB

    - by Hossein
    Hi,I have the code below. It load a CSV file into memory. This file contains the coordinates for different polygons.Each row of this file has X,Y coordinates and a string which tells that to which polygon this datapoint belongs. for example a polygone named "Poly1" with 100 data points has 100 rows in this file like : Poly1,X1,Y1 Poly1,X2,Y2 ... Poly1,X100,Y100 Poly2,X1,Y1 ..... The index.csv file has the number of datapoint(number of rows) for each polygon in file Polygons.csv. These details are not important. The thing is: I can successfully extract the datapoints for each polygon using the code below. However, When I plot the lines of different polygons are connected to each other and the plot looks crappy. I need the polygons to be separated(they are connected and overlapping the some areas though). I thought by using "fill" I can actually see them better. But "fill" just filles every polygon that it can find and that is not desirable. I only want to fill inside the polygons. Can someone help me? I can also send you my datapoint if necessary, they are less than 200Kb. Thanks [coordinates,routeNames,polygonData] = xlsread('Polygons.csv'); index = dlmread('Index.csv'); firstPointer = 0 lastPointer = index(1) for Counter=2:size(index) firstPointer = firstPointer + index(Counter) + 1 hold on plot(coordinates(firstPointer:lastPointer,2),coordinates(firstPointer:lastPointer,1),'r-') lastPointer = lastPointer + index(Counter) end

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  • How to reliably identify users across Internet?

    - by amn
    I know this is a big one. In fact, it may be used for some SO community wiki. Anyways, I am running a website that DOES NOT use explicit authentication of users. It's public as in open to everybody. However, due to the nature of the service, some users need to be locked out due to misbehavior. I am currently blocking IP addresses, but I am aware of the supposed fact that many people purposefully reset their DHCP client cache to have their ISP assign them new addresses. Is that a fact? I think it certainly is a lucrative possibility for some people who want to circumvent being denied access. So IPs turn out to be a suboptimal way of dealing with this. But there is nothing else, is it? MAC addresses don't survive on WAN (change from hop to hop?), and even if they did - these can also be spoofed, although I think less easily than IP renewal. Cookies and even Flash cookies are out of the question, because there are tons of "tutorials" how to wipe these, and those intent on wreaking havoc on Internet are well aware and well equipped against such rudimentary measures I would employ. Is there anything else to lean on? I was thinking heuristical profiling - collecting available data from client-side and forming some key with it, but have not gone as far as to implementing it - is it an option?

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  • How can I intelligently group rows of integers for a faceted search?

    - by Alastair
    I'm not even quite sure what terms I should be using for what I want, so any advice on what I'm even asking for would be very welcome. Basically, my web site lists user-generated accommodations. Each has a rent price, which users will be able to query in our new faceted search box. Users search by city, and within each city I'd like to present a different rent grouping. That is to say that in City #1, if we have listings ranging from $200 - $1000, I'd like to present checkboxes for: less than $300 $301 - $500 $501 - $700 more than $700 However, if City #2 has values that range from $500 - $1500, I want the ranges above to change accordingly. So, if I say that I want 5 or 6 range options in each city, I think I have two options: Take the min and max values and just split the difference. I don't like this idea because one listing with a rent of $10,000 will throw the whole scale off. Intelligently calculate the ranges using means, medians etc. Number 2 is what I need help with. I'm a web developer that gets logic, but was never strong on math and statistics at school. Can anyone point me towards a guide that'll help me figure this out?

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  • minimum L sum in a mxn matrix - 2

    - by hilal
    Here is my first question about maximum L sum and here is different and hard version of it. Problem : Given a mxn *positive* integer matrix find the minimum L sum from 0th row to the m'th row . L(4 item) likes chess horse move Example : M = 3x3 0 1 2 1 3 2 4 2 1 Possible L moves are : (0 1 2 2), (0 1 3 2) (0 1 4 2) We should go from 0th row to the 3th row with minimum sum I solved this with dynamic-programming and here is my algorithm : 1. Take a mxn another Minimum L Moves Sum array and copy the first row of main matrix. I call it (MLMS) 2. start from first cell and look the up L moves and calculate it 3. insert it in MLMS if it is less than exists value 4. Do step 2. until m'th row 5. Choose the minimum sum in the m'th row Let me explain on my example step by step: M[ 0 ][ 0 ] sum(L1 = (0, 1, 2, 2)) = 5 ; sum(L2 = (0,1,3,2)) = 6; so MLMS[ 0 ][ 1 ] = 6 sum(L3 = (0, 1, 3, 2)) = 6 ; sum(L4 = (0,1,4,2)) = 7; so MLMS[ 2 ][ 1 ] = 6 M[ 0 ][ 1 ] sum(L5 = (1, 0, 1, 4)) = 6; sum(L6 = (1,3,2,4)) = 10; so MLMS[ 2 ][ 2 ] = 6 ... the last MSLS is : 0 1 2 4 3 6 6 6 6 Which means 6 is the minimum L sum that can be reach from 0 to the m. I think it is O(8*(m-1)*n) = O(m*n). Is there any optimal solution or dynamic-programming algorithms fit this problem? Thanks, sorry for long question

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  • Is it better to use a relational database or document-based database for an app like Wufoo?

    - by mboyle
    I'm working on an application that's similar to Wufoo in that it allows our users to create their own databases and collect/present records with auto generated forms and views. Since every user is creating a different schema (one user might have a database of their baseball card collection, another might have a database of their recipes) our current approach is using MySQL to create separate databases for every user with its own tables. So in other words, the databases our MySQL server contains look like: main-web-app-db (our web app containing tables for users account info, billing, etc) user_1_db (baseball_cards_table) user_2_db (recipes_table) .... And so on. If a user wants to set up a new database to keep track of their DVD collection, we'd do a "create database ..." with "create table ...". If they enter some data in and then decide they want to change a column we'd do an "alter table ....". Now, the further along I get with building this out the more it seems like MySQL is poorly suited to handling this. 1) My first concern is that switching databases every request, first to our main app's database for authentication etc, and then to the user's personal database, is going to be inefficient. 2) The second concern I have is that there's going to be a limit to the number of databases a single MySQL server can host. Pretending for a moment this application had 500,000 user databases, is MySQL designed to operate this way? What if it were a million, or more? 3) Lastly, is this method going to be a nightmare to support and scale? I've never heard of MySQL being used in this way so I do worry about how this affects things like replication and other methods of scaling. To me, it seems like MySQL wasn't built to be used in this way but what do I know. I've been looking at document-based databases like MongoDB, CouchDB, and Redis as alternatives because it seems like a schema-less approach to this particular problem makes a lot of sense. Can anyone offer some advice on this?

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  • Element Content Versus Attribute for Simple XML Value

    - by MB
    I know the elements versus attributes debate has come up many times here and elsewhere (e.g. here, here, here, here, and here) but I haven't seen much discussion of elements versus attributes for simple property values. So which of the following approaches do you think is better for storing a simple value? A: Value in Element Content: <TotalCount>553</TotalCount> <CelsiusTemperature>23.5</CelsiusTemperature> <SingleDayPeriod>2010-05-29</SingleDayPeriod> <ZipCodeLocation>12203</ZipCodeLocation> or B: Value in Attribute: <TotalCount value="553"/> <CelsiusTemperature value="23.5"/> <SingleDayPeriod day="2010-05-29"/> <ZipCodeLocation code="12203"/> I suspect that putting the value in the element content (A) might look a little more familiar to most folks (though I'm not sure about that). Putting the value in an attribute (B) might use less characters, but that depends on the length of the element and attribute names. Putting the value in an attribute (B) might be more extensible, because you could potentially include all sorts of extra information as nested elements. Whereas, by putting the value inside the element content (A), you're restricting extensibility to adding more attributes. But then extensibility often isn't a concern for really simple properties - sometimes you know that you'll never need to add additional data. Bottom line might be that it simply doesn't matter, but it would still be great to hear some thoughts and see some votes for the two options.

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  • What is the fastest way to find duplicates in multiple BIG txt files?

    - by user2950750
    I am really in deep water here and I need a lifeline. I have 10 txt files. Each file has up to 100.000.000 lines of data. Each line is simply a number representing something else. Numbers go up to 9 digits. I need to (somehow) scan these 10 files and find the numbers that appear in all 10 files. And here comes the tricky part. I have to do it in less than 2 seconds. I am not a developer, so I need an explanation for dummies. I have done enough research to learn that hash tables and map reduce might be something that I can make use of. But can it really be used to make it this fast, or do I need more advanced solutions? I have also been thinking about cutting up the files into smaller files. To that 1 file with 100.000.000 lines is transformed into 100 files with 1.000.000 lines. But I do not know what is best: 10 files with 100 million lines or 1000 files with 1 million lines? When I try to open the 100 million line file, it takes forever. So I think, maybe, it is just too big to be used. But I don't know if you can write code that will scan it without opening. Speed is the most important factor in this, and I need to know if it can be done as fast as I need it, or if I have to store my data in another way, for example, in a database like mysql or something. Thank you in advance to anybody that can give some good feedback.

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  • Using Loops for prompts with If/Else/Esif

    - by Dante
    I started with: puts "Hello there, and what's your favorite number?" favnum = gets.to_i puts "Your favorite number is #{favnum}?" " A better favorite number is #{favnum + 1}!" puts "Now, what's your favorite number greater than 10?" favnumOverTen = gets.to_i if favnumOverTen < 10 puts "Hey! I said GREATER than 10! Try again buddy." else puts "Your favorite number great than 10 is #{favnumOverTen}?" puts "A bigger and better number over 10 is #{favnumOverTen * 10}!" puts "It's literally 10 times better!" end That worked fine, but if the user entered a number less than 10 the program ended. I want the user to be prompted to try again until they enter a number greater than 10. Am I supposed to do that with a loop? Here's what I took a swing at, but clearly it's wrong: puts "Hello there, and what's your favorite number?" favnum = gets.to_i puts "Your favorite number is #{favnum}?" " A better favorite number is #{favnum + 1}!" puts "Now, what's your favorite number greater than 10?" favnumOverTen = gets.to_i if favnumOverTen < 10 loop.do puts "Hey! I said GREATER than 10! Try again buddy." favnumOverTen = gets.to_i until favnumOverTen > 10 else puts "Your favorite number great than 10 is #{favnumOverTen}?" puts "A bigger and better number over 10 is #{favnumOverTen * 10}!" puts "It's literally 10 times better!" end

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  • What is it in the CSS/DOM that prevents an input box with display: block from expanding to the size of its container

    - by Steven Xu
    Sample HTML/CSS: <div class="container"> <input type="text" /> <div class="filler"></div> </div> div.container { padding: 5px; border: 1px solid black; background-color: gray; } div.filler { background-color: red; height: 5px; } input { display: block; } http://jsfiddle.net/bPEkb/3/ Question Why doesn't the input box expand to have the same outer width as, say div.filler? That is to say, why doesn't the input box expand to fit its container like other block elements with width: auto; do? I tried checking the "User Agent CSS" in Firebug to see if I could come up with something there. No luck. I couldn't find any specific differences in CSS that I could specifically link to the input box behaving differently from the regular div.filler. Besides curiousity, I'd like to know why this is to get to the bottom of it to figure out a way to set width once and forget it. My current practice of explicitly setting the width of both input and its containing block element seems redundant and less than modular. While I'm familiar with the technique of wrapping the input element in a div then assigning to the input element negative margins, this seems quite undesirable.

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  • Creating C++ client app for some abstract windows server - how to manage TCP connection to server speed?

    - by Kabumbus
    So we have some server with some address port and ip. we are developing that server so we can implement on it what ever we need for help. What are standard/best practices for data transfer speed management between C++ windows client app and server (C++)? My main point is in how to get how much data can be uploaded/downloaded from/to client via his low speed network to my relatively super fast server. (I need it for set up of his live stream Audio/Video bit rate) My try on explaining number 3. We do not care how fast is our server. It is always faster than needed. We care about client tyring to stream out to our server his media. he streams encoded (via ffmpeg) live video data to our server. But he has say ADSL with 500kb/s of outgoing traffic. Also he uses some ICQ or what so ever so he has less than 500 kb/s per second. And he wants to stream live video! So we need to set up our ffmpeg to encode video with respect to the bit rate user can provide. We develop server side and client side. We need a way of finding out how much user can upload per second currently (so value can change dynamically over time)

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  • Java 8 Stream, getting head and tail

    - by lyomi
    Java 8 introduced a Stream class that resembles Scala's Stream, a powerful lazy construct using which it is possible to do something like this very concisely: def from(n: Int): Stream[Int] = n #:: from(n+1) def sieve(s: Stream[Int]): Stream[Int] = { s.head #:: sieve(s.tail filter (_ % s.head != 0)) } val primes = sieve(from(2)) primes takeWhile(_ < 1000) print // prints all primes less than 1000 I wondered if it is possible to do this in Java 8, so I wrote something like this: IntStream from(int n) { return IntStream.iterate(n, m -> m + 1); } IntStream sieve(IntStream s) { int head = s.findFirst().getAsInt(); return IntStream.concat(IntStream.of(head), sieve(s.skip(1).filter(n -> n % head != 0))); } IntStream primes = sieve(from(2)); PrimitiveIterator.OfInt it = primes.iterator(); for (int prime = it.nextInt(); prime < 1000; prime = it.nextInt()) { System.out.println(prime); } Fairly simple, but it produces java.lang.IllegalStateException: stream has already been operated upon or closed because both findFirst() and skip() is a terminal operation on Stream which can be done only once. I don't really have to use up the stream twice since all I need is the first number in the stream and the rest as another stream, i.e. equivalent of Scala's Stream.head and Stream.tail. Is there a method in Java 8 Stream that I can achieve this? Thanks.

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  • question about counting sort

    - by davit-datuashvili
    hi i have write following code which prints elements in sorted order only one big problem is that it use two additional array here is my code public class occurance{ public static final int n=5; public static void main(String[]args){ // n is maximum possible value what it should be in array suppose n=5 then array may be int a[]=new int[]{3,4,4,2,1,3,5};// as u see all elements are less or equal to n //create array a.length*n int b[]=new int[a.length*n]; int c[]=new int[b.length]; for (int i=0;i<b.length;i++){ b[i]=0; c[i]=0; } for (int i=0;i<a.length;i++){ if (b[a[i]]==1){ c[a[i]]=1; } else{ b[a[i]]=1; } } for (int i=0;i<b.length;i++){ if (b[i]==1) { System.out.println(i); } if (c[i]==1){ System.out.println(i); } } } } // 1 2 3 3 4 4 5 1.i have two question what is complexity of this algorithm?i mean running time 2. how put this elements into other array with sorted order? thanks

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  • Entity Framework + MySQL - Why is the performance so terrible?

    - by Cyril Gupta
    When I decided to use an OR/M (Entity Framework for MySQL this time) for my new project I was hoping it would save me time, but I seem to have failed it (for the second time now). Take this simple SQL Query SELECT * FROM POST ORDER BY addedOn DESC LIMIT 0, 50 It executes and gives me results in less than a second as it should (the table has about 60,000 rows). Here's the equivalent LINQ To Entities query that I wrote for this var q = (from p in db.post orderby p.addedOn descending select p).Take(50); var q1 = q.ToList(); //This is where the query is fetched and timed out But this query never even executes it times out ALWAYS (without orderby it takes 5 seconds to run)! My timeout is set to 12 seconds so you can imagine it is taking much more than that. Why is this happening? Is there a way I can see what is the actual SQL Query that Entity Framework is sending to the db? Should I give up on EF+MySQL and move to standard SQL before I lose all eternity trying to make it work? I've recalibrated my indexes, tried eager loading (which actually makes it fail even without the orderby clause) Please help, I am about to give up OR/M for MySQL as a lost cause.

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  • Javascript to fire event when a key pressed on the Ajax Toolkit Combo box.

    - by Paul Chapman
    I have the following drop down list which is using the Ajax Toolkit to provide a combo box <cc1:ComboBox ID="txtDrug" runat="server" style="font-size:8pt; width:267px;" Font-Size="8pt" DropDownStyle="DropDownList" AutoCompleteMode="SuggestAppend" AutoPostBack="True" ontextchanged="txtDrug_TextChanged" /> Now I need to load this up with approx 7,000 records which takes a considerable time, and effects the response times when the page is posted back and forth. The code which loads these records is as follows; dtDrugs = wsHelper.spGetAllDrugs(); txtDrug.DataValueField = "pkDrugsID"; txtDrug.DataTextField = "drugName"; txtDrug.DataSource = dtDrugs; txtDrug.DataBind(); However if I could get an event to fire when a letter is typed instead of having to load 7000 records it is reduced to less than 50 in most instances. I think this can be done in Javascript. So the question is how can I get an event to fire such that when the form starts there is nothing in the drop down, but as soon as a key is pressed it searches for those records starting with that letter. The .Net side of things I'm sure about - it is the Javascript I'm not. Thanks in advance

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