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  • Fastest way to put contents of Set<String> to a single String with words separated by a whitespace?

    - by Lars Andren
    I have a few Set<String>s and want to transform each of these into a single String where each element of the original Set is separated by a whitespace " ". A naive first approach is doing it like this Set<String> set_1; Set<String> set_2; StringBuilder builder = new StringBuilder(); for (String str : set_1) { builder.append(str).append(" "); } this.string_1 = builder.toString(); builder = new StringBuilder(); for (String str : set_2) { builder.append(str).append(" "); } this.string_2 = builder.toString(); Can anyone think of a faster, prettier or more efficient way to do this?

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  • How to use constraint programming for optimizing shopping baskets?

    - by tangens
    I have a list of items I want to buy. The items are offered by different shops and different prices. The shops have individual delivery costs. I'm looking for an optimal shopping strategy (and a java library supporting it) to purchase all of the items with a minimal total price. Example: Item1 is offered at Shop1 for $100, at Shop2 for $111. Item2 is offered at Shop1 for $90, at Shop2 for $85. Delivery cost of Shop1: $10 if total order < $150; $0 otherwise Delivery cost of Shop2: $5 if total order < $50; $0 otherwise If I buy Item1 and Item2 at Shop1 the total cost is $100 + $90 +$0 = $190. If I buy Item1 and Item2 at Shop2 the total cost is $111 + $85 +$0 = $196. If I buy Item1 at Shop1 and Item2 at Shop2 the total cost is $100 + $10 + $85 + $0 = 195. I get the minimal price if I order Item1 and Item2 at Shop1: $190 What I tried so far I asked another question before that led me to the field of constraint programming. I had a look at cream and choco, but I did not figure out how to create a model to solve my problem. | shop1 | shop2 | shop3 | ... ----------------------------------------- item1 | p11 | p12 | p13 | item2 | p21 | p22 | p23 | . | | | | . | | | | ----------------------------------------- shipping | s1 | s2 | s3 | limit | l1 | l2 | l3 | ----------------------------------------- total | t1 | t2 | t3 | ----------------------------------------- My idea was to define these constraints: each price "p xy" is defined in the domain (0, c) where c is the price of the item in this shop only one price in a line should be non zero if one or more items are bought from one shop and the sum of the prices is lower than limit, then add shipping cost to the total cost shop total cost is the sum of the prices of all items in a shop total cost is the sum of all shop totals The objective is "total cost". I want to minimize this. In cream I wasn't able to express the "if then" constraint for conditional shipping costs. In choco these constraints exist, but even for 5 items and 10 shops the program was running for 10 minutes without finding a solution. Question How should I express my constraints to make this problem solvable for a constraint programming solver?

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  • How efficient is PHP's substr?

    - by zildjohn01
    I'm writing a parser in PHP which must be able to handle large in-memory strings, so this is a somewhat important issue. (ie, please don't "premature optimize" flame me, please) How does the substr function work? Does it make a second copy of the string data in memory, or does it reference the original? Should I worry about calling, for example, $str = substr($str, 1); in a loop?

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  • Combine query results from one table with the defaults from another

    - by pulegium
    This is a dumbed down version of the real table data, so may look bit silly. Table 1 (users): id INT username TEXT favourite_food TEXT food_pref_id INT Table 2 (food_preferences): id INT food_type TEXT The logic is as follows: Let's say I have this in my food preference table: 1, 'VEGETARIAN' and this in the users table: 1, 'John', NULL, 1 2, 'Pete', 'Curry', 1 In which case John defaults to be a vegetarian, but Pete should show up as a person who enjoys curry. Question, is there any way to combine the query into one select statement, so that it would get the default from the preferences table if the favourite_food column is NULL? I can obviously do this in application logic, but would be nice just to offload this to SQL, if possible. DB is SQLite3...

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  • Why does adding Crossover to my Genetic Algorithm give me worse results?

    - by MahlerFive
    I have implemented a Genetic Algorithm to solve the Traveling Salesman Problem (TSP). When I use only mutation, I find better solutions than when I add in crossover. I know that normal crossover methods do not work for TSP, so I implemented both the Ordered Crossover and the PMX Crossover methods, and both suffer from bad results. Here are the other parameters I'm using: Mutation: Single Swap Mutation or Inverted Subsequence Mutation (as described by Tiendil here) with mutation rates tested between 1% and 25%. Selection: Roulette Wheel Selection Fitness function: 1 / distance of tour Population size: Tested 100, 200, 500, I also run the GA 5 times so that I have a variety of starting populations. Stop Condition: 2500 generations With the same dataset of 26 points, I usually get results of about 500-600 distance using purely mutation with high mutation rates. When adding crossover my results are usually in the 800 distance range. The other confusing thing is that I have also implemented a very simple Hill-Climbing algorithm to solve the problem and when I run that 1000 times (faster than running the GA 5 times) I get results around 410-450 distance, and I would expect to get better results using a GA. Any ideas as to why my GA performing worse when I add crossover? And why is it performing much worse than a simple Hill-Climb algorithm which should get stuck on local maxima as it has no way of exploring once it finds a local max?

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  • Javascript + Firebug : "cannot access optimized closure" What does it mean?

    - by interstar
    I just got the following error in a piece of javascript (in Firefox 3.5, with Firebug running) cannot access optimized closure I know, superficially, what caused the error. I had a line options.length() instead of options.length Fixing this bug, made the message go away. But I'm curious. What does this mean? What is an optimized closure? Is optimizing an enclosure something that the javascript interpretter does automatically? What does it do?

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  • Regular expression not working after debugging

    - by Jaison
    I have an ASP.NET website with a regular expression validator text box. I have changed the expression in the regular expression validation property "validator expression" and after compiling (rebuild) and running, the validation CHANGEs are not reflecting. The previous validation is working fine but the changed validation is not working. Please help me! edit: First code: ([a-zA-Z0-9_-.]+)\@((base.co.uk)|(base.com)|(group.com)) Second code: @"([a-zA-Z0-9_\-.]+)@((base\.co\.uk)|(base\.com)|(group\.com)|(arg\.co\.uk)|(arggroup\.com))"

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  • steps to fix a project that won't compile

    - by eco_bach
    Hi Pulling my hair out in trying to get a simple window based project to compile. I am running both 3.2.2 and 3.2.3 versions of Xcode. The latter is set up in a separate folder. Originally I used the latter to create and compile my project against the new 4.0 sdk. It compiled fine. Then I made the mistake of deleting some sdks I thought I no longer needed. Ever since I can no longer compile. Right now I get a dozen or so errors similar to the following "_OBJC_CLASS_$_CATransition", referenced from: objc-class-ref-to-CATransition in ViewTransitionsAppDelegate.o My active executable is the iphone simulator 4 and Base SDK is iPhone device 3.0. I tried reinstalling the xcode3.2.3 installer, no difference. I'm totally stymied, as my project WAS working and compiling fine, both to the simulator and external device. Are there any best practices or recommended steps in fixing or rebuilding a project when it won't compile? Any help welcome!

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  • Can this MySQL subquery be optimised?

    - by Dan
    I have two tables, news and news_views. Every time an article is viewed, the news id, IP address and date is recorded in news_views. I'm using a query with a subquery to fetch the most viewed titles from news, by getting the total count of views in the last 24 hours for each one. It works fine except that it takes between 5-10 seconds to run, presumably because there's hundreds of thousands of rows in news_views and it has to go through the entire table before it can finish. The query is as follows, is there any way at all it can be improved? SELECT n.title , nv.views FROM news n LEFT JOIN ( SELECT news_id , count( DISTINCT ip ) AS views FROM news_views WHERE datetime >= SUBDATE(now(), INTERVAL 24 HOUR) GROUP BY news_id ) AS nv ON nv.news_id = n.id ORDER BY views DESC LIMIT 15

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  • Find the closest vector

    - by Alexey Lebedev
    Hello! Recently I wrote the algorithm to quantize an RGB image. Every pixel is represented by an (R,G,B) vector, and quantization codebook is a couple of 3-dimensional vectors. Every pixel of the image needs to be mapped to (say, "replaced by") the codebook pixel closest in terms of euclidean distance (more exactly, squared euclidean). I did it as follows: class EuclideanMetric(DistanceMetric): def __call__(self, x, y): d = x - y return sqrt(sum(d * d, -1)) class Quantizer(object): def __init__(self, codebook, distanceMetric = EuclideanMetric()): self._codebook = codebook self._distMetric = distanceMetric def quantize(self, imageArray): quantizedRaster = zeros(imageArray.shape) X = quantizedRaster.shape[0] Y = quantizedRaster.shape[1] for i in xrange(0, X): print i for j in xrange(0, Y): dist = self._distMetric(imageArray[i,j], self._codebook) code = argmin(dist) quantizedRaster[i,j] = self._codebook[code] return quantizedRaster ...and it works awfully, almost 800 seconds on my Pentium Core Duo 2.2 GHz, 4 Gigs of memory and an image of 2600*2700 pixels:( Is there a way to somewhat optimize this? Maybe the other algorithm or some Python-specific optimizations.

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  • How to simplify this code or a better design?

    - by Tattat
    I am developing a game, the game have different mode. Easy, Normal, and Difficult. So, I'm thinking about how to store the game mode. My first idea is using number to represent the difficulty. Easy = 0 Normal = 1 Difficult = 2 So, my code will have something like this: switch(gameMode){ case 0: //easy break; case 1: //normal break; case 3: //difficult break; } But I think it have some problems, if I add a new mode, for example, "Extreme", I need to add case 4... ... it seems not a gd design. So, I am thinking making a gameMode object, and different gameMode is sub class of the super class gameMode. The gameMode object is something like this: class GameMode{ int maxEnemyNumber; int maxWeaponNumber; public static GameMode init(){ GameMode gm = GameMode(); gm.maxEnemyNumber = 0; gm.maxWeaponNumber = 0; return gm; } } class EasyMode extends GameMode{ public static GameMode init(){ GameMode gm = super.init(); gm.maxEnemyNumber = 10; gm.maxWeaponNumber = 100; return gm; } } class NormalMode extends GameMode{ public static GameMode init(){ GameMode gm = super.init(); gm.maxEnemyNumber = 20; gm.maxWeaponNumber = 80; return gm; } } But I think it seems too "bulky" to create an object to store gameMode, my "gameMode" only store different variables for game settings.... Is that any simple way to store data only instead of making an Object? thz u.

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  • lexical analysis gives only one output?

    - by Caffè
    I tested this example(lexe.java), but it gave me only one output. I gave this text as a reader: public class LexeTest{ private int a = 14; } And the nextToken() function is : public Category nextToken () { if (inp.findWithinHorizon (tokenPat, 0) == null) return Category.EOF; else { lastLexeme = inp.match ().group (0); if (inp.match ().start (1) != -1) return nextToken (); else if (inp.match ().start (2) != -1) return Category.IDENT; else if (inp.match ().start (3) != -1) return Category.NUMERAL; Category result = tokenMap.get (lastLexeme); if (result == null) return Category.ERROR; else return result; } } Isdie the main method: System.out.println(lexeObject.nextToken()); output is : IDENT Why? but the textfile contains multiple keywords? Anyone know what's the problem?

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  • What is everything involved from typing in code to executing a program?

    - by Befall
    I realized, when just asking a question, I don't understand all the components that are part of the coding process. This seems a silly question, but I can't find a definitive answer on Google, Wiki, nothing. What exactly are all the parts called, and how do they work and intertwine? I'm talking whatever you type code into, whatever checks that for errors, compiles it, and runs it. I'd appreciate any links, repeats, etc. I apologize for such a bland, stupid question.

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  • How can I track the last location of a shipment effeciently using latest date of reporting?

    - by hash
    I need to find the latest location of each cargo item in a consignment. We mostly do this by looking at the route selected for a consignment and then finding the latest (max) time entered against nodes of this route. For example if a route has 5 nodes and we have entered timings against first 3 nodes, then the latest timing (max time) will tell us its location among the 3 nodes. I am really stuck on this query regarding performance issues. Even on few hundred rows, it takes more than 2 minutes. Please suggest how can I improve this query or any alternative approach I should acquire? Note: ATA= Actual Time of Arrival and ATD = Actual Time of Departure SELECT DISTINCT(c.id) as cid,c.ref as cons_ref , c.Name, c.CustRef FROM consignments c INNER JOIN routes r ON c.Route = r.ID INNER JOIN routes_nodes rn ON rn.Route = r.ID INNER JOIN cargo_timing ct ON c.ID=ct.ConsignmentID INNER JOIN (SELECT t.ConsignmentID, Max(t.firstata) as MaxDate FROM cargo_timing t GROUP BY t.ConsignmentID ) as TMax ON TMax.MaxDate=ct.firstata AND TMax.ConsignmentID=c.ID INNER JOIN nodes an ON ct.routenodeid = an.ID INNER JOIN contract cor ON cor.ID = c.Contract WHERE c.Type = 'Road' AND ( c.ATD = 0 AND c.ATA != 0 ) AND (cor.contract_reference in ('Generic','BP001','020-543-912')) ORDER BY c.ref ASC

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  • Question about Cost in Oracle Explain Plan

    - by Will
    When Oracle is estimating the 'Cost' for certain queries, does it actually look at the amount of data (rows) in a table? For example: If I'm doing a full table scan of employees for name='Bob', does it estimate the cost by counting the amount of existing rows, or is it always a set cost?

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  • Checking for a variable in the executable

    - by rboorgapally
    Is there a way to know whether a variable is defined, by looking at the executable. Lets say I declare int i; in the main function. By compiling and linking I get an executable my_program.exe. Now, by looking inside my_program.exe, can I say if it has an int eger variable i ?

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  • C# - Cannot implicitly convert type List<Product> to List<IProduct>

    - by Keith Barrows
    I have a project with all my Interface definitions: RivWorks.Interfaces I have a project where I define concrete implmentations: RivWorks.DTO I've done this hundreds of times before but for some reason I am getting this error now: Cannot implicitly convert type 'System.Collections.Generic.List<RivWorks.DTO.Product>' to 'System.Collections.Generic.List<RivWorks.Interfaces.DataContracts.IProduct>' Interface definition (shortened): namespace RivWorks.Interfaces.DataContracts { public interface IProduct { [XmlElement] [DataMember(Name = "ID", Order = 0)] Guid ProductID { get; set; } [XmlElement] [DataMember(Name = "altID", Order = 1)] long alternateProductID { get; set; } [XmlElement] [DataMember(Name = "CompanyId", Order = 2)] Guid CompanyId { get; set; } ... } } Concrete class definition (shortened): namespace RivWorks.DTO { [DataContract(Name = "Product", Namespace = "http://rivworks.com/DataContracts/2009/01/15")] public class Product : IProduct { #region Constructors public Product() { } public Product(Guid ProductID) { Initialize(ProductID); } public Product(string SKU, Guid CompanyID) { using (RivEntities _dbRiv = new RivWorksStore(stores.RivConnString).NegotiationEntities()) { model.Product rivProduct = _dbRiv.Product.Where(a => a.SKU == SKU && a.Company.CompanyId == CompanyID).FirstOrDefault(); if (rivProduct != null) Initialize(rivProduct.ProductId); } } #endregion #region Private Methods private void Initialize(Guid ProductID) { using (RivEntities _dbRiv = new RivWorksStore(stores.RivConnString).NegotiationEntities()) { var localProduct = _dbRiv.Product.Include("Company").Where(a => a.ProductId == ProductID).FirstOrDefault(); if (localProduct != null) { var companyDetails = _dbRiv.vwCompanyDetails.Where(a => a.CompanyId == localProduct.Company.CompanyId).FirstOrDefault(); if (companyDetails != null) { if (localProduct.alternateProductID != null && localProduct.alternateProductID > 0) { using (FeedsEntities _dbFeed = new FeedStoreReadOnly(stores.FeedConnString).ReadOnlyEntities()) { var feedProduct = _dbFeed.AutoWithImage.Where(a => a.ClientID == companyDetails.ClientID && a.AutoID == localProduct.alternateProductID).FirstOrDefault(); if (companyDetails.useZeroGspPath.Value || feedProduct.GuaranteedSalePrice > 0) // kab: 2010.04.07 - new rules... PopulateProduct(feedProduct, localProduct, companyDetails); } } else { if (companyDetails.useZeroGspPath.Value || localProduct.LowestPrice > 0) // kab: 2010.04.07 - new rules... PopulateProduct(localProduct, companyDetails); } } } } } private void PopulateProduct(RivWorks.Model.Entities.Product product, RivWorks.Model.Entities.vwCompanyDetails RivCompany) { this.ProductID = product.ProductId; if (product.alternateProductID != null) this.alternateProductID = product.alternateProductID.Value; this.BackgroundColor = product.BackgroundColor; ... } private void PopulateProduct(RivWorks.Model.Entities.AutoWithImage feedProduct, RivWorks.Model.Entities.Product rivProduct, RivWorks.Model.Entities.vwCompanyDetails RivCompany) { this.alternateProductID = feedProduct.AutoID; this.BackgroundColor = Helpers.Product.GetCorrectValue(RivCompany.defaultBackgroundColor, rivProduct.BackgroundColor); ... } #endregion #region IProduct Members public Guid ProductID { get; set; } public long alternateProductID { get; set; } public Guid CompanyId { get; set; } ... #endregion } } In another class I have: using dto = RivWorks.DTO; using contracts = RivWorks.Interfaces.DataContracts; ... public static List<contracts.IProduct> Get(Guid companyID) { List<contracts.IProduct> myList = new List<dto.Product>(); ... Any ideas why this might be happening? (And I am sure it is something trivially simple!)

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  • Most Efficient Alternative Method of Storing Settings for iPhone Apps

    - by JPK
    I am not using the Settings bundle to store the settings for my app, as I prefer to allow the user to access the settings within the app (they may be changed fairly often). I do realize that there is the option to do both, but for now, I am trying to find the most optimal place to store the settings within the app. I have a good number of settings (from what I have read, probably too many for NSUserDefaults), and the two main options I am considering are: 1) storing the settings in a dictionary in the plist, loading the settings into a NSDictionary property in the app delegate and accessing them via the sharedDelegate 2) storing the settings in a Core Data entity (1 row on Settings entity), loading the settings into a Settings object in the app delegate and accessing them via the sharedDelegate Of these two, which would be the optimal method, performance wise?

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  • sequential mandelbrot image creation

    - by visanio_learner
    can anyone tell me what is wrong in this code? i am getting an error in the main function, when i am calling the 'file_write' method function inside the main function, it says 'y' is not declared in this scope, but actually it was an argument that i have passed it in the method function earlier. is it a serious error? #include <stdio.h> #include <stdlib.h> #include <time.h> unsigned int width = 1500; unsigned int height = 1500; unsigned int max_iterations = 30000; unsigned int **color = NULL; double threshold = 4; double min_re = -2.0; double max_re = 1.0; double min_im = -1.2; double max_im = min_im+(max_re-min_re)*height/width; double x_factor = (max_re-min_re)/(width-1); double y_factor = (max_im-min_im)/(height-1); int file_write(int x, int y, double min_re, double max_im, double x_factor, double y_factor) { FILE *fractal = fopen("mandelbrot_imageSequential.ppm","w+"); if(fractal != NULL) { fprintf(fractal,"P6\n"); fprintf(fractal,"# %s\n", "Mandelbrot_imageSequential.ppm"); fprintf(fractal,"%d %d\n", height, width); fprintf(fractal,"255\n"); unsigned int R = 0, G = 0, B = 0; for(unsigned y = 0; y < height; ++y) { double c_im = max_im - y*y_factor; for(unsigned x = 0; x < width; ++x) { double c_re = min_re + x*x_factor; double Z_re = c_re, Z_im = c_im; bool image_inside = true; R = 0, G = 0, B = 0; for(unsigned n=0; n<max_iterations; ++n) { double Z_re2 = Z_re*Z_re, Z_im2 = Z_im*Z_im; if(Z_re2 + Z_im2 > threshold) { image_inside = false; G = n; if(G == 10) { G = 25, R = 10, B = 5; } break; } Z_im = 2 * Z_re * Z_im + c_im; Z_re = Z_re2 - Z_im2 + c_re; } if(image_inside) { putc(R, fractal); putc(G, fractal); putc(B, fractal); } else { putc(R, fractal); putc(G, fractal); putc(B, fractal); } } } fclose(fractal); return 0; } } int main(int argc, char *argv[]) { if(argc != 9) { printf("There is an error in the input given.\n"); return 0; } else { height = atoi(argv[1]); width = atoi(argv[2]); max_iterations = atoi(argv[3]); min_re = atof(argv[4]); max_re = atof(argv[5]); min_im = atof(argv[6]); max_im = atof(argv[7]); threshold = atoi(argv[8]); } color = (unsigned int**)malloc(height*sizeof(unsigned int*)); printf("height = %d\twidth = %d\tmaximum_iterations = %d\tminimum_x-value = %.2f\tmaximum_x-value = %.2f\tminimum_y-value = %.2f\tmaximum_y-value = %.2f\tthreshold_value = %.2f\t\n",height,width,max_iterations,min_re,max_re,min_im,max_im,threshold); int x; for(x = 0; x < height; x++) { color[x] = (unsigned int*)malloc(width*sizeof(unsigned int)); } time_t ts,te; time(&ts); file_write(x,y,min_re,max_im,x_factor,y_factor); time(&te); double diff = difftime(te,ts); printf("Total Time elapsed: %f\n",diff); for(x = 0; x < height; x++) { free(color[x]); } free(color); return 0; }

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