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  • Structuring an input file

    - by Ricardo
    I am in the process of structuring a small program to perform some hydraulic analysis of pipe flow. As I am envisioning this, the program will read an input file, store the input parameters in a suitable way, operate on them and finally output results. I am struggling with how to structure the input file in a sane way; that is, in a way that a human can write it easily and a machine can parse it easily. A sample input file made available to me for a similar program is just a stream of comma-separated numbers that don't make much sense on their own, so that's the scenario I am trying to avoid. Though I am giving the details of my particular problem, I am more interested in general input-file structuring strategies. Is a stream of comma-separated values my best bet? Would I be better off using some sort of key:value structure? I don't know much about this, so any help will probably put me in a better track than I am now.

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  • C# and SQL data layer code generator

    I've created a simple yet efficient tool to help generate stored procedures and a C# data access layer from a table.  Instead of using an ORM, this uses standard ADO .NET (SqlConnection, SqlDataReader, etc).  Check it out at www.asteio.com.  It's saved me a ton of time and I'm hoping it does the same for you....Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Issue with aborted MySQL connections (error code: 4)

    - by arikfr
    Some of the connections between my application server (Ubuntu, Apache, PHP) and my DB server (Ubuntu, MySQL) are failing with error code 4. According to the documentation error code 4 is: OS error code 4: Interrupted system call At first I thought that maybe the issue is that the DB server has too many connections and fails because there are too much open files. But it seems not to be the case because: Too many open files has different error code (24). I've checked and during peak time the server had 497 files open (checked using lsof command) while the maximum is 1024. The TCP settings were already checked (see prior question). Any ideas what this can be or what should I check?

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  • Updates to Silverlight Code Browser

    A couple of bits of news. I did a number of updates to the HackingSilverlightCodeBrowser here:http://www.hackingsilverlight.net/HackingSilverlightCodeBrowser.html including things like MEF and IsolatedStorage. As to the community edition of the book, I'm still trying to get some contributors to finish. I've been slammed with 60 hour weeks so chapter 2 and 4 and appendix a still need edits. maybe a weeks worth of work pending time which tends to be limited in my life. :)...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Code better with JustCode Q1 SP1

    We've just uploaded the Service Pack 1 for JustCode so feel free to log in to your Telerik accounts and download JustCode. Earlier this week Visual Studio 2010 RTM was released and we are happy to announce that this version of JustCode fully supports it. Other areas of interest in this release are the typing assistance behavior and JavaScript formatting. We also further optimized JustCodes memory usage and speed. Youll find the full release notes for the Service Pack here.  Visual Studio 2010 changes As Visual Studio is now officially out we now fully support its final version as well as the new .NET 4.0 framework features. Typing Assistance improvements As JustCodes first official release approached we started getting an increasing number of requests for a typing assistance feature. In spite of being at a fairly advanced stage of our development cycle we managed to squeeze in a basic ...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • A better way to organize your Silverlight Code Snippets.

    - by mbcrump
    I hate re-writing code. I also hate it when I find a great code snippet on the web and forget to bookmark it or it gets lost in my endless sea of bookmarks. So what do you do to get around this? This is the question that I was asking myself at the end of 2010. How can I get my Silverlight code organized? My requirements for a snippet manager were: Needs to be FREE. An easy way to view XAML/C# code behind together in one “view”. I wanted the ability to store the code snippets in cloud in case my HDD dies. Searchable Keywords to quickly find code snippets. I started looking for a snippet manager that would allow me to do just that and finally found Snippet Manager. Before going any further, I think that one of the most important things to note here is that this software supports 37 languages. It’s not just for Silverlight developers nor C# only guys. The software supports Java, SQL and even COBOL.   Below is a screenshot of the Snippet Manager that shows my Silverlight code snippet. You will notice that I have highlighted two sections. The top part is my XAML and the bottom is my C# code behind. I’ve included a sample below of my code snippets so that you can get an idea of how I organized it. Another thing that’s great about this software is that it supports plain text. I added some connection strings in the TEXT section below.  Once you have finished adding your code snippets, you can store them in the cloud. I created a FTP directory called “snippets” on my FTP Server and hit the upload button once I am finished adding my new codes snippets. This will allow me to use the code snippets on another computer with this application on my USB Key. See screenshots below: Enter your FTP credentials below: Hit the Uploads button on the Toolbar: Login in to your FTP Server and verify the following files are now on the FTP Server: Another great feature of the Snippet Manager is that you can also integrate this into VS2010 by clicking Tools –> External Tools: And setting up your External Screen to point to the Executable: You can now launch it by going to Tools –> Snippet Manager. If you want you could also a shortcut to launch the program with HotKeys. As you can see, this is a nice little program that includes everything needed to organize your code snippets very clean. I didn’t go over every feature but this is something that you might want to download and give it a shot.  Subscribe to my feed CodeProject

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  • What Do You Think About This Smelly Test?

    - by panamack
    I caught a whiff of a smell eminating from one of my tests, in a scenario akin to the following: [TestFixture] public void CarPresenterTests{ [Test] public void Throws_If_Cars_Wheels_Collection_Is_Null(){ IEnumerable<Wheels> wheels = null; var car = new Car(wheels); Assert.That( ()=>new CarPresenter(car), Throws.InstanceOf<ArgumentException>() .With.Message.EqualTo("Can't create if cars wheels is null)); } } public class CarPresenter{ public CarPresenter(Car car) { if(car.Wheels == null) throw new ArgumentException("Can't create if cars wheels is null); _car = car; _car.Wheels.Rolling += WheelsRollingHandler; } } I was struggling to describe what the problem is except that it seems wrong that a CarPresenter should attempt to dictate to a Car whether or not it's Wheels are initialised correctly. I wondered what pointers people here might give me?

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  • how to serialize function depending on what instance of object calls it, if same instance call in a thread then do serialize else not

    - by LondonDreams
    I have a function which fetches and updates some record from db and I am trying to make sure each if the function is called by same instance of object(same Or different thread) then function should behave synchronized else its a call from different object instance function need not to be synchronized. I have tried it use a lock per client. That is, instead of synchronizing the method directly using explicit locking through lock objects using Map. function is like :- getAndUpdateMyHitCount(myObjId){ //go to db and get unique record by myObjId //fetch value , increment , save update } And this function may get call is same thread by different Or same object instance But as fetching and matching from Map is slow , Is there other optimized way to do this ? Found similar at this Question but dont feel that is optimized

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  • Continuing to code on large projects

    - by user3487347
    I am a hobbyist programmer, and I've started many medium - sized projects to work on just by myself. These include games, a raytracer, physics simulations etc. By the time these projects get to a certain size (around 5000 lines), I begin to slow down in adding features to the program. This is not because of a lack of ideas of what to implement in a program, but rather a struggle in how to go about it. In particular, I'm afraid of breaking what I already have working in order to implement a new feature. I've tried using version control like Git and Subversion, but these seem unnecessary when you are a one man team. I simply have a folder of "versions" of my program, one for each major change I make. How do I keep coding past this 5000 line mark? What about the 50000 line mark?

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  • Toutes les semaines un peu de code pour aller plus loin avec Windows 7, l'accélération matérielle

    En cette fin d'année, la communauté de Developpez.com s'est alliée avec Microsoft France pour relayer une série de questions / réponses sur le développement Windows 7. A partir d'aujourd'hui, nous poserons une question chaque lundi sur une fonctionnalité propre au développement d'applications Windows 7. La bonne réponse de la question de la semaine sera ensuite dévoilée la semaine suivante avec un exemple de mise en pratique. Êtes-vous prêt à relever le défi ? Pensez-vous bien connaître les possibilités que proposent les API Windows 7 ? C'est ce que nous allons voir dès aujourd'hui, nous attendons vos propositions ! La réponse de la semaine : Quelle est le nom de la nouvelle ...

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  • Podlogger Half Baked Code, but yours for free.

    Some time ago I started building a demo application that would have been posted on www.asp.net. It is a Podcast Publishing application and completing basic functionality we decided that it was a bit too complex for the intended introductory material. Though not finished (Meaning NOT FINISHED, INCOMPLETE, IMPERFECT, ETC) I thought Id share it in case anyone finds it useful. Some of the stuff that is in there : Basic Post Publication with Rich Editor File Upload Comments Submission...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Best way to reuse common functions between ASPX pages ?

    - by DFord
    I have a bunch of functions that are used across multiple ASPX files. I want to condense these down to one file to be used for all the ASPX files. I have a few ideas but I want to know what the accepted method to doing this would be. I have an idea to just create a class to put them in. However, I was wondering if i could put them in a ascx page, but that does not look like the solution I'm looking for. Is there a accepted method for this type of situation?

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  • Long lines of text in source code [closed]

    - by ale
    Possible Duplicate: Is the 80 character limit still relevant in times of widescreen monitors? I used to set a vertical line set at 80 characters in my text editor and then I added carriage returns if the lines got too long. I later increased the value to 135 characters. I started using word wrap and not giving myself a limit but tried to keep lines short if I could because it took a lot of time shortening my lines. People at work use word wrap and don't give themselves a limit.. is this the correct way? What are you meant to do ? Many thanks.

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  • Organizing your Data Access Layer

    - by nighthawk457
    I am using Entity Framework as my ORM in an ASP.Net application. I have my database already created so ended up generating the entity model from it. What is a good way to organize files/classes in the data access layer. My entity framework model is in a class library and I was planning on adding additional classes per Entity(i.e per database table) and putting all the queries related to those tables in their respective classes. I am not sure if this is a right approach and if it is then where do the queries requiring data from multiple tables go? Am I completely wrong in organizing my files based on entities/tables and should I organize them based on functional areas instead.

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  • USING JSON SERIALIZATION FOR CODE BEHIND-JAVASCRIPT DATA COMMUNICATION

    Many of us went through a scenario like, can us pass a full of C# type/class to the javascript? Modify from there and again return back to C#? The difficulty is that JavaScript only knows string format comared to C# which has many data types. So how we can pass an entires class to JavaScript? Here we need to handle with JSON serialization techniques.

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  • A friend told me Python is garbage, I'm taking web design classes in the Spring and I have a textbook on C++. What should I do? [on hold]

    - by user107165
    I dont know if I should start digging into Python beforehand just to get acquanited with programming and "whet my appetite" or if I should work on the C++ book... Python definitely has more resources around town and I like the beginner friendly approach that seems to go along with every site that appeals to it. Or should I just wait for my assignments that start in 4 months? Any tips for an aspiring programmer?

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  • What is wrong with this HTML5 <address> element? [closed]

    - by binaryorganic
    <div id="header-container"> <address> <ul> <li>lorem ipsum</li> <li>(xxx) xxx-xxxx</li> </ul> </address> </div> And the CSS looks like this: #header-container address {float: right; margin-top: 25px;} When I load the page, it looks fine in Chrome & IE, but in Firefox it's ignoring the styling completely. When I view source in firefox it looks like above, but in Firebug it looks like this: <div id="header-container"> <address> </address> <ul> <li>lorem ipsum</li> <li>(xxx) xxx-xxxx</li> </ul> </div>

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  • Source code (Source repository) for Ubuntu 10.10 [on hold]

    - by user3241533
    I was trying to use the following command to install build-dep on Ubuntu 10.10: apt-get build-dep --no-install-recommends linux-image-$(uname -r) but I got the following error: E: You must put some 'source' URIs in your sources.list I have already changed archive.ubuntu.com to old-releases.ubuntu.com for all the repositories in my source list. After including the source repositories, I got a different error: E: Could not open file /var/lib/apt/lists/de.archive.ubuntu.com_ubuntu_dists_precise_main_source_Sources - open (2: No such file or directory) Any suggested solutions? Thanks!

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  • Optimizing a lot of Scanner.findWithinHorizon(pattern, 0) calls

    - by darvids0n
    I'm building a process which extracts data from 6 csv-style files and two poorly laid out .txt reports and builds output CSVs, and I'm fully aware that there's going to be some overhead searching through all that whitespace thousands of times, but I never anticipated converting about about 50,000 records would take 12 hours. Excerpt of my manual matching code (I know it's horrible that I use lists of tokens like that, but it was the best thing I could think of): public static String lookup(List<String> tokensBefore, List<String> tokensAfter) { String result = null; while(_match(tokensBefore)) { // block until all input is read if(id.hasNext()) { result = id.next(); // capture the next token that matches if(_matchImmediate(tokensAfter)) // try to match tokensAfter to this result return result; } else return null; // end of file; no match } return null; // no matches } private static boolean _match(List<String> tokens) { return _match(tokens, true); } private static boolean _match(List<String> tokens, boolean block) { if(tokens != null && !tokens.isEmpty()) { if(id.findWithinHorizon(tokens.get(0), 0) == null) return false; for(int i = 1; i <= tokens.size(); i++) { if (i == tokens.size()) { // matches all tokens return true; } else if(id.hasNext() && !id.next().matches(tokens.get(i))) { break; // break to blocking behaviour } } } else { return true; // empty list always matches } if(block) return _match(tokens); // loop until we find something or nothing else return false; // return after just one attempted match } private static boolean _matchImmediate(List<String> tokens) { if(tokens != null) { for(int i = 0; i <= tokens.size(); i++) { if (i == tokens.size()) { // matches all tokens return true; } else if(!id.hasNext() || !id.next().matches(tokens.get(i))) { return false; // doesn't match, or end of file } } return false; // we have some serious problems if this ever gets called } else { return true; // empty list always matches } } Basically wondering how I would work in an efficient string search (Boyer-Moore or similar). My Scanner id is scanning a java.util.String, figured buffering it to memory would reduce I/O since the search here is being performed thousands of times on a relatively small file. The performance increase compared to scanning a BufferedReader(FileReader(File)) was probably less than 1%, the process still looks to be taking a LONG time. I've also traced execution and the slowness of my overall conversion process is definitely between the first and last like of the lookup method. In fact, so much so that I ran a shortcut process to count the number of occurrences of various identifiers in the .csv-style files (I use 2 lookup methods, this is just one of them) and the process completed indexing approx 4 different identifiers for 50,000 records in less than a minute. Compared to 12 hours, that's instant. Some notes (updated): I don't necessarily need the pattern-matching behaviour, I only get the first field of a line of text so I need to match line breaks or use Scanner.nextLine(). All ID numbers I need start at position 0 of a line and run through til the first block of whitespace, after which is the name of the corresponding object. I would ideally want to return a String, not an int locating the line number or start position of the result, but if it's faster then it will still work just fine. If an int is being returned, however, then I would now have to seek to that line again just to get the ID; storing the ID of every line that is searched sounds like a way around that. Anything to help me out, even if it saves 1ms per search, will help, so all input is appreciated. Thankyou! Usage scenario 1: I have a list of objects in file A, who in the old-style system have an id number which is not in file A. It is, however, POSSIBLY in another csv-style file (file B) or possibly still in a .txt report (file C) which each also contain a bunch of other information which is not useful here, and so file B needs to be searched through for the object's full name (1 token since it would reside within the second column of any given line), and then the first column should be the ID number. If that doesn't work, we then have to split the search token by whitespace into separate tokens before doing a search of file C for those tokens as well. Generalised code: String field; for (/* each record in file A */) { /* construct the rest of this object from file A info */ // now to find the ID, if we can List<String> objectName = new ArrayList<String>(1); objectName.add(Pattern.quote(thisObject.fullName)); field = lookup(objectSearchToken, objectName); // search file B if(field == null) // not found in file B { lookupReset(false); // initialise scanner to check file C objectName.clear(); // not using the full name String[] tokens = thisObject.fullName.split(id.delimiter().pattern()); for(String s : tokens) objectName.add(Pattern.quote(s)); field = lookup(objectSearchToken, objectName); // search file C lookupReset(true); // back to file B } else { /* found it, file B specific processing here */ } if(field != null) // found it in B or C thisObject.ID = field; } The objectName tokens are all uppercase words with possible hyphens or apostrophes in them, separated by spaces. Much like a person's name. As per a comment, I will pre-compile the regex for my objectSearchToken, which is just [\r\n]+. What's ending up happening in file C is, every single line is being checked, even the 95% of lines which don't contain an ID number and object name at the start. Would it be quicker to use ^[\r\n]+.*(objectname) instead of two separate regexes? It may reduce the number of _match executions. The more general case of that would be, concatenate all tokensBefore with all tokensAfter, and put a .* in the middle. It would need to be matching backwards through the file though, otherwise it would match the correct line but with a huge .* block in the middle with lots of lines. The above situation could be resolved if I could get java.util.Scanner to return the token previous to the current one after a call to findWithinHorizon. I have another usage scenario. Will put it up asap.

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  • F# - Facebook Hacker Cup - Double Squares

    - by Jacob
    I'm working on strengthening my F#-fu and decided to tackle the Facebook Hacker Cup Double Squares problem. I'm having some problems with the run-time and was wondering if anyone could help me figure out why it is so much slower than my C# equivalent. There's a good description from another post; Source: Facebook Hacker Cup Qualification Round 2011 A double-square number is an integer X which can be expressed as the sum of two perfect squares. For example, 10 is a double-square because 10 = 3^2 + 1^2. Given X, how can we determine the number of ways in which it can be written as the sum of two squares? For example, 10 can only be written as 3^2 + 1^2 (we don't count 1^2 + 3^2 as being different). On the other hand, 25 can be written as 5^2 + 0^2 or as 4^2 + 3^2. You need to solve this problem for 0 = X = 2,147,483,647. Examples: 10 = 1 25 = 2 3 = 0 0 = 1 1 = 1 My basic strategy (which I'm open to critique on) is to; Create a dictionary (for memoize) of the input numbers initialzed to 0 Get the largest number (LN) and pass it to count/memo function Get the LN square root as int Calculate squares for all numbers 0 to LN and store in dict Sum squares for non repeat combinations of numbers from 0 to LN If sum is in memo dict, add 1 to memo Finally, output the counts of the original numbers. Here is the F# code (See code changes at bottom) I've written that I believe corresponds to this strategy (Runtime: ~8:10); open System open System.Collections.Generic open System.IO /// Get a sequence of values let rec range min max = seq { for num in [min .. max] do yield num } /// Get a sequence starting from 0 and going to max let rec zeroRange max = range 0 max /// Find the maximum number in a list with a starting accumulator (acc) let rec maxNum acc = function | [] -> acc | p::tail when p > acc -> maxNum p tail | p::tail -> maxNum acc tail /// A helper for finding max that sets the accumulator to 0 let rec findMax nums = maxNum 0 nums /// Build a collection of combinations; ie [1,2,3] = (1,1), (1,2), (1,3), (2,2), (2,3), (3,3) let rec combos range = seq { let count = ref 0 for inner in range do for outer in Seq.skip !count range do yield (inner, outer) count := !count + 1 } let rec squares nums = let dict = new Dictionary<int, int>() for s in nums do dict.[s] <- (s * s) dict /// Counts the number of possible double squares for a given number and keeps track of other counts that are provided in the memo dict. let rec countDoubleSquares (num: int) (memo: Dictionary<int, int>) = // The highest relevent square is the square root because it squared plus 0 squared is the top most possibility let maxSquare = System.Math.Sqrt((float)num) // Our relevant squares are 0 to the highest possible square; note the cast to int which shouldn't hurt. let relSquares = range 0 ((int)maxSquare) // calculate the squares up front; let calcSquares = squares relSquares // Build up our square combinations; ie [1,2,3] = (1,1), (1,2), (1,3), (2,2), (2,3), (3,3) for (sq1, sq2) in combos relSquares do let v = calcSquares.[sq1] + calcSquares.[sq2] // Memoize our relevant results if memo.ContainsKey(v) then memo.[v] <- memo.[v] + 1 // return our count for the num passed in memo.[num] // Read our numbers from file. //let lines = File.ReadAllLines("test2.txt") //let nums = [ for line in Seq.skip 1 lines -> Int32.Parse(line) ] // Optionally, read them from straight array let nums = [1740798996; 1257431873; 2147483643; 602519112; 858320077; 1048039120; 415485223; 874566596; 1022907856; 65; 421330820; 1041493518; 5; 1328649093; 1941554117; 4225; 2082925; 0; 1; 3] // Initialize our memoize dictionary let memo = new Dictionary<int, int>() for num in nums do memo.[num] <- 0 // Get the largest number in our set, all other numbers will be memoized along the way let maxN = findMax nums // Do the memoize let maxCount = countDoubleSquares maxN memo // Output our results. for num in nums do printfn "%i" memo.[num] // Have a little pause for when we debug let line = Console.Read() And here is my version in C# (Runtime: ~1:40: using System; using System.Collections.Generic; using System.Diagnostics; using System.IO; using System.Linq; using System.Text; namespace FBHack_DoubleSquares { public class TestInput { public int NumCases { get; set; } public List<int> Nums { get; set; } public TestInput() { Nums = new List<int>(); } public int MaxNum() { return Nums.Max(); } } class Program { static void Main(string[] args) { // Read input from file. //TestInput input = ReadTestInput("live.txt"); // As example, load straight. TestInput input = new TestInput { NumCases = 20, Nums = new List<int> { 1740798996, 1257431873, 2147483643, 602519112, 858320077, 1048039120, 415485223, 874566596, 1022907856, 65, 421330820, 1041493518, 5, 1328649093, 1941554117, 4225, 2082925, 0, 1, 3, } }; var maxNum = input.MaxNum(); Dictionary<int, int> memo = new Dictionary<int, int>(); foreach (var num in input.Nums) { if (!memo.ContainsKey(num)) memo.Add(num, 0); } DoMemoize(maxNum, memo); StringBuilder sb = new StringBuilder(); foreach (var num in input.Nums) { //Console.WriteLine(memo[num]); sb.AppendLine(memo[num].ToString()); } Console.Write(sb.ToString()); var blah = Console.Read(); //File.WriteAllText("out.txt", sb.ToString()); } private static int DoMemoize(int num, Dictionary<int, int> memo) { var highSquare = (int)Math.Floor(Math.Sqrt(num)); var squares = CreateSquareLookup(highSquare); var relSquares = squares.Keys.ToList(); Debug.WriteLine("Starting - " + num.ToString()); Debug.WriteLine("RelSquares.Count = {0}", relSquares.Count); int sum = 0; var index = 0; foreach (var square in relSquares) { foreach (var inner in relSquares.Skip(index)) { sum = squares[square] + squares[inner]; if (memo.ContainsKey(sum)) memo[sum]++; } index++; } if (memo.ContainsKey(num)) return memo[num]; return 0; } private static TestInput ReadTestInput(string fileName) { var lines = File.ReadAllLines(fileName); var input = new TestInput(); input.NumCases = int.Parse(lines[0]); foreach (var lin in lines.Skip(1)) { input.Nums.Add(int.Parse(lin)); } return input; } public static Dictionary<int, int> CreateSquareLookup(int maxNum) { var dict = new Dictionary<int, int>(); int square; foreach (var num in Enumerable.Range(0, maxNum)) { square = num * num; dict[num] = square; } return dict; } } } Thanks for taking a look. UPDATE Changing the combos function slightly will result in a pretty big performance boost (from 8 min to 3:45): /// Old and Busted... let rec combosOld range = seq { let rangeCache = Seq.cache range let count = ref 0 for inner in rangeCache do for outer in Seq.skip !count rangeCache do yield (inner, outer) count := !count + 1 } /// The New Hotness... let rec combos maxNum = seq { for i in 0..maxNum do for j in i..maxNum do yield i,j }

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  • Shouldn't prepared statements be much more fsater?

    - by silversky
    $s = explode (" ", microtime()); $s = $s[0]+$s[1]; $con = mysqli_connect ('localhost', 'test', 'pass', 'db') or die('Err'); for ($i=0; $i<1000; $i++) { $stmt = $con -> prepare( " SELECT MAX(id) AS max_id , MIN(id) AS min_id FROM tb "); $stmt -> execute(); $stmt->bind_result($M,$m); $stmt->free_result(); $rand = mt_rand( $m , $M ).'<br/>'; $res = $con -> prepare( " SELECT * FROM tb WHERE id >= ? LIMIT 0,1 "); $res -> bind_param("s", $rand); $res -> execute(); $res->free_result(); } $e = explode (" ", microtime()); $e = $e[0]+$e[1]; echo number_format($e-$s, 4, '.', ''); // and: $link = mysql_connect ("localhost", "test", "pass") or die (); mysql_select_db ("db") or die ("Unable to select database".mysql_error()); for ($i=0; $i<1000; $i++) { $range_result = mysql_query( " SELECT MAX(`id`) AS max_id , MIN(`id`) AS min_id FROM tb "); $range_row = mysql_fetch_object( $range_result ); $random = mt_rand( $range_row->min_id , $range_row->max_id ); $result = mysql_query( " SELECT * FROM tb WHERE id >= $random LIMIT 0,1 "); } defenitly prepared statements are much more safer but also every where it says that they are much faster BUT in my test on the above code I have: - 2.45 sec for prepared statements - 5.05 sec for the secon example What do you think I'm doing wrong? Should I use the second solution or I should try to optimize the prep stmt?

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  • ILOG CPLEX: how to populate IloLPMatrix while using addGe to set up the model?

    - by downer
    I have a queatoin about IloLPMatrix and addGe. I was trying to follow the example of AdMIPex5.java to generate user defined cutting planes based on the solution to the LP relaxation. The difference is that eh initial MIP model is not read in from a mps file, but set up in the code using methods like addGe, addLe etc. I think this is why I ran into problems while copying the exampe to do the following. IloLPMatrix lp = (IloLPMatrix)cplex.LPMatrixIterator().next(); lp from the above line turns to be NULL. I am wondering 1. What is the relationship between IloLPMatrix and the addLe, addGe commands? I tried to addLPMatrix() to the model, and then used model.addGe methods. but the LPMatrix seems to be empty still. How do I populate the IloLPMatrix of the moel according to the value that I had set up using addGe and addLe. Is the a method to this easily, or do I have to set them up row by row myself? I was doing this to get the number of variables and their values by doing lp.getNumVars(). Is there other methods that I can use to get the number of variables and their values wihout doing these, since my system is set up by addLe, addGe etc? Thanks a lot for your help on this.

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  • Fastest way to remove non-numeric characters from a VARCHAR in SQL Server

    - by Dan Herbert
    I'm writing an import utility that is using phone numbers as a unique key within the import. I need to check that the phone number does not already exist in my DB. The problem is that phone numbers in the DB could have things like dashes and parenthesis and possibly other things. I wrote a function to remove these things, the problem is that it is slow and with thousands of records in my DB and thousands of records to import at once, this process can be unacceptably slow. I've already made the phone number column an index. I tried using the script from this post: http://stackoverflow.com/questions/52315/t-sql-trim-nbsp-and-other-non-alphanumeric-characters But that didn't speed it up any. Is there a faster way to remove non-numeric characters? Something that can perform well when 10,000 to 100,000 records have to be compared. Whatever is done needs to perform fast. Update Given what people responded with, I think I'm going to have to clean the fields before I run the import utility. To answer the question of what I'm writing the import utility in, it is a C# app. I'm comparing BIGINT to BIGINT now, with no need to alter DB data and I'm still taking a performance hit with a very small set of data (about 2000 records). Could comparing BIGINT to BIGINT be slowing things down? I've optimized the code side of my app as much as I can (removed regexes, removed unneccessary DB calls). Although I can't isolate SQL as the source of the problem anymore, I still feel like it is.

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