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  • fast algorithm to sort very small set

    - by aaa
    hello. This is the problem I ran into long time ago. I thought I may ask your for your ideas. assume I have very small set of numbers (integers), 4 or 8 elements, that need to be sorted, fast. what would be the best approach/algorithm? my approach was to use the max/min functions only. At this point it becomes somewhat hardware dependent , so let us assume Intel 64-bit processor with SSE3 . Thanks

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  • Iteration speed of int vs long

    - by jqno
    I have the following two programs: long startTime = System.currentTimeMillis(); for (int i = 0; i < N; i++); long endTime = System.currentTimeMillis(); System.out.println("Elapsed time: " + (endTime - startTime) + " msecs"); and long startTime = System.currentTimeMillis(); for (long i = 0; i < N; i++); long endTime = System.currentTimeMillis(); System.out.println("Elapsed time: " + (endTime - startTime) + " msecs"); Note: the only difference is the type of the loop variable (int and long). When I run this, the first program consistently prints between 0 and 16 msecs, regardless of the value of N. The second takes a lot longer. For N == Integer.MAX_VALUE, it runs in about 1800 msecs on my machine. The run time appears to be more or less linear in N. So why is this? I suppose the JIT-compiler optimizes the int loop to death. And for good reason, because obviously it doesn't do anything. But why doesn't it do so for the long loop as well? A colleague thought we might be measuring the JIT compiler doing its work in the long loop, but since the run time seems to be linear in N, this probably isn't the case.

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  • Grouping consecutive identical items: IEnumerable<T> to IEnumerable<IEnumerable<T>>

    - by Romain Verdier
    I've got an interresting problem: Given an IEnumerable<string>, is it possible to yield a sequence of IEnumerable<string> that groups identical adjacent strings in one pass? Let me explain. Considering the following IEnumerable<string> (pseudo representation): {"a","b","b","b","c","c","d"} How to get an IEnumerable<IEnumerable<string>> that would yield something of the form: { // IEnumerable<IEnumerable<string>> {"a"}, // IEnumerable<string> {"a","b","b"}, // IEnumerable<string> {"c","c"}, // IEnumerable<string> {"d"} // IEnumerable<string> } The method prototype would be: public IEnumerable<IEnumerable<string>> Group(IEnumerable<string> items) { // todo } Important notes : Only one iteration over the original sequence No intermediary collections allocations (we can assume millions of strings in the original sequence, and millions consecutives identicals strings in each group) Keeping enumerators and defered execution behavior Is it possible, and how would you write it?

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  • Speed Difference between native OLE DB and ADO.NET

    - by weijiajun
    I'm looking for suggestions as well as any benchmarks or observations people have. We are looking to rewrite our data access layer and are trying to decide between native C++ OLEDB or ADO.NET for connecting with databases. Currently we are specifically targeting Oracle which would mean we would use the Oracle OLE DB provider and the ODP.NET. Requirements: 1. All applications will be in managed code so using native C++ OLEDB would require C++/CLI to work (no PInvoke way to slow). 2. Application must work with multiple databases in the future, currently just targeting Oracle specifically. Question: 1. Would it be more performant to use ADO.NET to accomplish this or use native C++ OLE DB wrapped in a Managed C++ interface for managed code to access? Any ideas, or help or places to look on the web would be greatly appreciated.

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  • Suggestions for Single-Page Web Application Design?

    - by DaveDev
    My view is that unless you need to change the basic structure of the user interface, you should not have to reload the page at all for any user interactions. I'd like to approach my next ASP.NET MVC project with this in mind. Can anyone suggest any principles, patterns or practices* I should consider? Excellent book, btw. Still trying to wrap my head around some of the concepts though. I thought a question like this would help link the theory to a practical design. Thanks

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  • Doing a large number of upserts as fast as possible

    - by Jason Swett
    My app (which uses MySQL) is doing a large number of subsequent upserts. Right now my SQL looks like this: INSERT IGNORE INTO customer (name,customer_number,social_security_number,phone) VALUES ('VICTOR H KINDELL','123','123','123') INSERT IGNORE INTO customer (name,customer_number,social_security_number,phone) VALUES ('VICTOR H KINDELL','123','123','123') INSERT IGNORE INTO customer (name,customer_number,social_security_number,phone) VALUES ('VICTOR H KINDELL OR','123','123','123') INSERT IGNORE INTO customer (name,customer_number,social_security_number,phone) VALUES ('TRACY L WALTER PERSONAL REP FOR','123','123','123') INSERT IGNORE INTO customer (name,customer_number,social_security_number,phone) VALUES ('TRACY L WALTER PERSONAL REP FOR','123','123','123') So far I've found INSERT IGNORE to be the fastest way to achieve upserts. Selecting a record to see if it exists and then either updating it or inserting a new one is too slow. Even this is not as fast as I'd like because I need to do a separate statement for each record. Sometimes I'll have around 50,000 of these statements in a row. Is there a way to take care of all of these in just one statement, without deleting any existing records?

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  • Best way to retrieve certain field of all documents returned by a lucen search

    - by Philipp
    Hi, I was wondering what the best way is to retrieve a certain field of all documents returned by a Searcher of Lucene. Background: each document has a date field (written on) and I would like to show a timeline of all found documents, so I need to extract the date (day) field of all the documents I find with the search. I currently retrieve every document using Searcher.doc(int, FieldSelector) having the selector only retrieve the certain field. I have indexed 250k documents, the search itself takes no time and returns about 10k document ids. Retrieving those however, takes 20+ seconds. What can I do to speed things up, but still get all the values I need. Thx in advance Philipp

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  • Task Manager: CPU usage history

    - by Nezdet
    I bougth recently a server with 2 x X5550, they are quad (4 cores each) total 8 cores If I check the task manager it shows in the CPU usage history 16 diagrams, Should't it be 8 cause I have 2 processors with quad? or the diagrams maybee shows the Threads of the CPU?

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  • Why is thread local storage so slow?

    - by dsimcha
    I'm working on a custom mark-release style memory allocator for the D programming language that works by allocating from thread-local regions. It seems that the thread local storage bottleneck is causing a huge (~50%) slowdown in allocating memory from these regions compared to an otherwise identical single threaded version of the code, even after designing my code to have only one TLS lookup per allocation/deallocation. This is based on allocating/freeing memory a large number of times in a loop, and I'm trying to figure out if it's an artifact of my benchmarking method. My understanding is that thread local storage should basically just involve accessing something through an extra layer of indirection, similar to accessing a variable via a pointer. Is this incorrect? How much overhead does thread-local storage typically have? Note: Although I mention D, I'm also interested in general answers that aren't specific to D, since D's implementation of thread-local storage will likely improve if it is slower than the best implementations.

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  • JSP Page HttpServletRequest getAttribute Typecasting

    - by MontyBongo
    Hi There, Any ideas on the correct method of typecasting an Object out of a getAttribute request from a JSP page HttpServletRequest? I have googled but it seems that the common solution is just sticking suppresswarnings in your code... Something I would very much like to avoid. I currently have: HashMap<String, ArrayList<HashMap<String, String>>> accounts = (HashMap<String, ArrayList<HashMap<String, String>>>)request.getAttribute("accounts"); And the complier is giving me this warning: Unchecked cast from Object to HashMap Thanks in Advance!! MB.

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  • Changing POST data used by Apache Bench per iteration

    - by Alabaster Codify
    I'm using ab to do some load testing, and it's important that the supplied querystring (or POST) parameters change between requests. I.e. I need to make requests to URLs like: http://127.0.0.1:9080/meth?param=0 http://127.0.0.1:9080/meth?param=1 http://127.0.0.1:9080/meth?param=2 ... to properly exercise the application. ab seems to only read the supplied POST data file once, at startup, so changing its content during the test run is not an option. Any suggestions?

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  • SQL Query slow in .NET application but instantaneous in SQL Server Management Studio

    - by user203882
    Here is the SQL SELECT tal.TrustAccountValue FROM TrustAccountLog AS tal INNER JOIN TrustAccount ta ON ta.TrustAccountID = tal.TrustAccountID INNER JOIN Users usr ON usr.UserID = ta.UserID WHERE usr.UserID = 70402 AND ta.TrustAccountID = 117249 AND tal.trustaccountlogid = ( SELECT MAX (tal.trustaccountlogid) FROM TrustAccountLog AS tal INNER JOIN TrustAccount ta ON ta.TrustAccountID = tal.TrustAccountID INNER JOIN Users usr ON usr.UserID = ta.UserID WHERE usr.UserID = 70402 AND ta.TrustAccountID = 117249 AND tal.TrustAccountLogDate < '3/1/2010 12:00:00 AM' ) Basicaly there is a Users table a TrustAccount table and a TrustAccountLog table. Users: Contains users and their details TrustAccount: A User can have multiple TrustAccounts. TrustAccountLog: Contains an audit of all TrustAccount "movements". A TrustAccount is associated with multiple TrustAccountLog entries. Now this query executes in milliseconds inside SQL Server Management Studio, but for some strange reason it takes forever in my C# app and even timesout (120s) sometimes. Here is the code in a nutshell. It gets called multiple times in a loop and the statement gets prepared. cmd.CommandTimeout = Configuration.DBTimeout; cmd.CommandText = "SELECT tal.TrustAccountValue FROM TrustAccountLog AS tal INNER JOIN TrustAccount ta ON ta.TrustAccountID = tal.TrustAccountID INNER JOIN Users usr ON usr.UserID = ta.UserID WHERE usr.UserID = @UserID1 AND ta.TrustAccountID = @TrustAccountID1 AND tal.trustaccountlogid = (SELECT MAX (tal.trustaccountlogid) FROM TrustAccountLog AS tal INNER JOIN TrustAccount ta ON ta.TrustAccountID = tal.TrustAccountID INNER JOIN Users usr ON usr.UserID = ta.UserID WHERE usr.UserID = @UserID2 AND ta.TrustAccountID = @TrustAccountID2 AND tal.TrustAccountLogDate < @TrustAccountLogDate2 ))"; cmd.Parameters.Add("@TrustAccountID1", SqlDbType.Int).Value = trustAccountId; cmd.Parameters.Add("@UserID1", SqlDbType.Int).Value = userId; cmd.Parameters.Add("@TrustAccountID2", SqlDbType.Int).Value = trustAccountId; cmd.Parameters.Add("@UserID2", SqlDbType.Int).Value = userId; cmd.Parameters.Add("@TrustAccountLogDate2", SqlDbType.DateTime).Value =TrustAccountLogDate; // And then... reader = cmd.ExecuteReader(); if (reader.Read()) { double value = (double)reader.GetValue(0); if (System.Double.IsNaN(value)) return 0; else return value; } else return 0;

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  • How to load Facebook iFrame-App into Application Tab on Profile Page

    - by m99
    Hi everybody, how can i load a working iframe app (tested via http://apps.facebook.com/my-app-name) into an application tab on the profile page of my own fanpage. I got the tab, but didn't see anything in the tab. first time i called the tab i got a couple of errors. But now I just see nothing. In sourcecode some css definitions are included. I read, that profile tabs can only use FBML. Is this right? If true, how can i load an iframe application with FBML into the profile tab? Thanks in advance. Marco

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  • So how I can control the page contents loading sequence in dojo

    - by David Zhao
    Hi there, I'm using dojo for our UI's, and would like to load certain part of page contents in sequence. For example, for a certain stock, I'd like to load stock general information, such as ticker, company name, key stats, etc. and a grid with the last 30 days open/close prices. Different contents will be fetched from the server separately. Now, I'd like first load the grid so the user can have something to look at, then, say, start loading of key stats which is a large data set takes longer time to load. How do I do this. I tried: dojo.addOnLoad(function() { startGrid(); //mock grid startup function which works fine getKeyStats(); //mock key stat getter function also works fine }); But dojo is loading getKeyStats(), then startGrid() here for some reason, and sequence doesn't seem be matter here. So how I can control the loading sequence at will? Thanks in advance! David

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  • SQL Server high CPU and I/O activity database tuning

    - by zapping
    Our application tends to be running very slow recently. On debugging and tracing found out that the process is showing high cpu cycles and SQL Server shows high I/O activity. Can you please guide as to how it can be optimised? The application is now about an year old and the database file sizes are not very big or anything. The database is set to auto shrink. Its running on win2003, SQL Server 2005 and the application is a web application coded in c# i.e vs2005

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  • Execute PHP without leaving page

    - by Dylan Taylor
    Okay. I have a form - textarea (named "su") and submit button. When the form is submitted, I need to run a PHP script without refreshing/leaving page "echo" or somehow print a return on the screen I'm pretty sure this works via some kind of ajax request thing. but I have no idea what I'm talking about. I'm not big on ajax or javascript, but this is a function i use very frequently and I'd like to learn how it works so I can implement it when i need to now and in the future. Like i said I'm uneducated with ajax or java. a quick example would be wonderful. thanks for taking the time to read!

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  • Rails prettyPhoto does not show photo with jquery (instead redirect to photo page)

    - by dare
    i do all instruction for use prettyPhoto in https://github.com/hiq5/prettyphoto-rails. and i do this to show a single photo( not gallery ) =link_to image_tag(photo.photo_url(:thumb).to_s, :alt => photo.name ,:class => "img-polaroid"), photo.photo_url, :rel => 'prettyPhoto' but still redirect to photo url and show photo, and doesn't use jQuery to show it on the current page. i check it with chrome development tools, there isn't any error. i use haml to generate views (instead erb), and carrierwave to upload photos. by the way I use twitter bootstrap. any help is appreciated.

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  • Benchmarking a particular method in Objective-C

    - by Jasconius
    I have a critical method in an Objective-C application that I need to optimize as much as possible. I first need to take some easy benchmarks on this one single method so I can compare my progress as I optimize. What is the easiest way to track the execution time of a given method in, say, milliseconds, and print that to console.

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  • C# TabPage.Controls.Add too long

    - by Toto
    Hi, At run time, I add one control to a tabpage and I notice that it takes 0.5 sec to do it. It's rather long and I would like to reduce this time. I tried Suspend/ResumeLayout but for only one action it's no relevant and do not improved anythng. Any ideas ? Thx

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  • Which is faster in Python: x**.5 or math.sqrt(x)?

    - by Casey
    I've been wondering this for some time. As the title say, which is faster, the actual function or simply raising to the half power? UPDATE This is not a matter of premature optimization. This is simply a question of how the underlying code actually works. What is the theory of how Python code works? I sent Guido van Rossum an email cause I really wanted to know the differences in these methods. My email: There are at least 3 ways to do a square root in Python: math.sqrt, the '**' operator and pow(x,.5). I'm just curious as to the differences in the implementation of each of these. When it comes to efficiency which is better? His response: pow and ** are equivalent; math.sqrt doesn't work for complex numbers, and links to the C sqrt() function. As to which one is faster, I have no idea...

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  • Load httpmodule to .aspx page

    - by Kumara
    I have created 3 textbox and 2 buttons programatically from HTTPModule. These buttons and textboxes are contained in an html table. It works correctly. I want know how load these table to existing .aspx page <div>***********</div> <div> Some controls contained here <div> I want load HTTPModule table in this place. </div> </div> Please help me. Give a good tutorial for creating a pluggable http module. Thanks.

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