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• RegEx to Reject Unescaped Character

  - by JDV72

  I want to restrict usage of unescaped ampersands in a particular input field. I'm having trouble getting a RegEx to kill usage of "&" unless followed by "amp;"...or perhaps just restrict usage of "& " (note the space). I tried to adapt the answer in this thread, but to no avail. Thanks. (FWIW, here's a RegEx I made to ensure that a filename field didn't contain restrited chars. and ended in .mp3. It works fine, but does it look efficient?)

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• How does Photoshop (Or drawing programs) blit?

  - by user146780

  I'm getting ready to make a drawing application in Windows. I'm just wondering, do drawing programs have a memory bitmap which they lock, then set each pixel, then blit? I don't understand how Photoshop can move entire layers without lag or flicker without using hardware acceleration. Also in a program like Expression Design, I could have 200 shapes and move them around all at once with no lag. I'm really wondering how this can be done without GPU help. I don't think super efficient algorithms could justify that? Thanks

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• Error with global variable in php not extending to included php file

  - by phileaton

  I have an html file that calls has a php section in the header like so: $page = basename($_SERVER['PHP_SELF']); Now further down in the html file I have a included footer like so: <?php include("footer.php"); ?> In this script I am referencing the $page variable, but it doesn't find it. I tried echoing the variable and nothing happened. When I place the basename() code in the footer.php file though, it handled it fine. I'd like to be efficient with the coding, so how can I get the footer.php file to get that $page variable? Is there a better way to do this than including the $page variable twice?

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• How to find the largest square in the number (Java)

  - by Ypsilon IV

  Hello everyone, I want to find the largest square in the number, but I am stuck at some point. I would really appreciate some suggestions. This is what I've done so far: I take the number on the input, factorize into prime numbers, and put the sequence of prime numbers to ArrayList. Numbers are sorted, in a sense, thus the numbers in the sequence are increasing. For example, 996 is 2 2 3 83 1000 is 2 2 2 5 5 5 100000 is 2 2 2 2 2 5 5 5 5 5 My idea now is to count number of occurrences of each elements in the sequence, so if the number of occurrences is divisible by two, then this is the square. In this way, I can get another sequence, where the right most element divisible by two is the largest square. What is the most efficient way to count occurrences in the ArrayList? Or is there any better way to find the largest square? Many thanks in advance!

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• How can I speed up line by line reading of an ASCII file? (C++)

  - by Jon

  Here's a bit of code that is a considerable bottleneck after doing some measuring: //----------------------------------------------------------------------------- // Construct dictionary hash set from dictionary file //----------------------------------------------------------------------------- void constructDictionary(unordered_set<string> &dict) { ifstream wordListFile; wordListFile.open("dictionary.txt"); string word; while( wordListFile >> word ) { if( !word.empty() ) { dict.insert(word); } } wordListFile.close(); } I'm reading in ~200,000 words and this takes about 240 ms on my machine. Is the use of ifstream here efficient? Can I do better? I'm reading about mmap() implementations but I'm not understanding them 100%. The input file is simply text strings with *nix line terminations.

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• Prims vs Polys: what are the pros and cons of each?

  - by Richard Inglis

  I've noticed that most 3d gaming/rendering environments represent solids as a mesh of (usually triangular) 3d polygons. However some examples, such as Second Life, or PovRay use solids built from a set of 3d primitives (cube, sphere, cone, torus etc) on which various operations can be performed to create more complex shapes. So my question is: why choose one method over the other for representing 3d data? I can see there might be benefits for complex ray-tracing operations to be able to describe a surface as a single mathematical function (like PovRay does), but SL surely isn't attempting anything so ambitious with their rendering engine. Equally, I can imagine it might be more bandwidth-efficient to serve descriptions of generalised solids instead of arbitrary meshes, but is it really worth the downside that SL suffers from (ie modelling stuff is really hard, and usually the results are ugly) - was this just a bad decision made early in SL's development that they're now stuck with? Or is it an artefact of what's easiest to implement in OpenGL?

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• Determining the order of a list of numbers (possibly without sorting)

  - by Victor Liu

  I have an array of unique integers (e.g. val[i]), in arbitrary order, and I would like to populate another array (ord[i]) with the the sorted indexes of the integers. In other words, val[ord[i]] is in sorted order for increasing i. Right now, I just fill in ord with 0, ..., N, then sort it based on the value array, but I am wondering if we can be more efficient about it since ord is not populated to begin with. This is more of a question out of curiousity; I don't really care about the extra overhead from having to prepopulate a list and then sort it (it's small, I use insertion sort). This may be a silly question with an obvious answer, but I couldn't find anything online.

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• sharpziplib - can you add a file without it copying the entire zip first?

  - by schmoopy

  Im trying to add an existing file to a .zip file using sharpziplib - problem is, the zip file is 1GB in size. When i try to add 1 small file (400k) sharpziplib creates a copy/temp of the orig zip file before adding the new file - this poses a problem when the amount of free disk space is less than 2x the zip file you are trying to update. for example: 1GB zip myfile.zip 1GB zip myfile.zip.tmp.293 ZipFile zf = new ZipFile(path); zf.BeginUpdate(); zf.Add(file); // Adding a 400k file here causes a 1GB temp file to be created zf.EndUpdate(); zf.Close(); Is there a more efficient way to do this? Thanks :-)

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• Detecting similar words among n text documents

  - by javanes

  Hi; I have n documents and want to find common words that are included in these documents. For example I want to say (n-3) documents include the word "web". Certainly I can do this by basic data structures but there maybe efficient algorithm or a way to handle same words with different suffix. Is there any algorithm for such purposes? I am unfamiliar with datamining world. In general manner is there a term used for efforts of finding similarities between different documents? If there is then I will make my research easily. Thanks.

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• Can I serialize a BitArray to XML?

  - by SimonNet

  Hello I have a business class which I need to serialize to xml. It has a BitArray property. I have decorated it with [XmlAttribute] but the serialization is failing with To be XML serializable, types which inherit from ICollection must have an implementation of Add(System.Boolean) at all levels of their inheritance hierarchy. System.Collections.BitArray does not implement Add(System.Boolean). I am not sure whether its possible to serialize to xml? If not what would be an efficient means of serializing the BitArray Thanks for looking

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• Sql Server XML-type column duplicate entry detection

  - by aaaa bbbb

  In Sql Server I am using an XML type column to store a message. I do not want to store duplicate messages. I only will have a few messages per user. I am currently querying the table for these messages, converting the XML to string in my C# code. I then compare the strings with what I am about to insert. Unfortunately, Sql Server pretty-prints the data in the XML typed fields. What you store into the database is not necessarily exactly the same string as what you get back out later. It is functionally equivalent, but may have white space removed, etc. Is there an efficient way to compare an XML string that I am considering inserting with those that are already in the database? As an aside, if I detect a duplicate I need to delete the older message then insert the replacement.

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• The best way to deploy one site for two companies in ColdFusion?

  - by Ofeargall

  My client has multiple companies; different names/logos etc, but all the content on the sites are identical with the exception of said names/logos. In a ColdFusion environment, what would be the best way for me to serve up identical content and swap out the logos/company names on the fly so I can keep everything in one spot? Is this a jQuery solution? regex? Or will ColdFusion enable me to deploy this in an efficient manner based on the url and session variables?

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• How to hash and check for equality of objects with circular references

  - by mfya

  I have a cyclic graph-like structure that is represented by Node objects. A Node is either a scalar value (leaf) or a list of n=1 Nodes (inner node). Because of the possible circular references, I cannot simply use a recursive HashCode() function, that combines the HashCode() of all child nodes: It would end up in an infinite recursion. While the HashCode() part seems at least to be doable by flagging and ignoring already visited nodes, I'm having some troubles to think of a working and efficient algorithm for Equals(). To my surprise I did not find any useful information about this, but I'm sure many smart people have thought about good ways to solve these problems...right? Example (python): A = [ 1, 2, None ]; A[2] = A B = [ 1, 2, None ]; B[2] = B A is equal to B, because it represents exactly the same graph. BTW. This question is not targeted to any specific language, but implementing hashCode() and equals() for the described Node object in Java would be a good practical example.

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• What data structure would be the least painful DataTable replacement?

  - by MatthewMartin

  I'm storing a lot of sorted ~10 row 2 column/key value pairs in ASP.NET cache-- they're the data for dropdownlists. Right now they are all DataTables, which isn't very space efficient (the rule of thumb is 10x increase in size when data is strored in a dataset). Old Code DataTable table = dataAccess.GetDataTable(); dropDownList.DataSource = table; Hoped for new Code Unknown data = dataAccess.GetSomethingMoreSpaceEfficient(); dropDownList.DataSource = data; What pre-existing datastructures are similar enough to DataTable that would minimize code breakage and reduce the serialized size when stored in ASP.NET cache?

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• Copy an array backwards? Array.Copy?

  - by daniel

  I have a List<T> that I want to be able to copy to an array backwards, meaning start from List.Count and copy maybe 5 items starting at the end of the list and working its way backwards. I could do this with a simple reverse for loop; however there is probably a faster/more efficient way of doing this so I thought I should ask. Can I use Array.Copy somehow? Originally I was using a Queue as that pops it off in the correct order I need, but I now need to pop off multiple items at once into an array and I thought a list would be faster.

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• apache commons http client efficiency

  - by wo_shi_ni_ba_ba

  I use apache commons http client to send data via post every second, is there a way to make the following code more efficient? I know http is stateless, but is there anything I can do to improve since the base url is always the same in this case(only the parameter value change. private void sendData(String s){ try { HttpClient client = getHttpClient(); HttpPost method = new HttpPost("http://192.168.1.100:8080/myapp"); System.err.println("send to server "+s); List formparams = new ArrayList(); formparams.add(new BasicNameValuePair("packet", s)); UrlEncodedFormEntity entity = new UrlEncodedFormEntity(formparams, "UTF-8"); method.setEntity(entity); HttpResponse resp=client.execute(method); String res = EntityUtils.toString(resp.getEntity()); System.out.println(res); } catch (Exception e) { e.printStackTrace(); } } private HttpClient getHttpClient() { if(httpClient==null){ httpClient = new DefaultHttpClient(); } return httpClient; }

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• Best place to store large amounts of session data

  - by audiopleb

  I'm building an application that needs to store and re-use large amounts of data per session. So for example, the user selects a large list of list items (say 2000 or significantly more) which have a numeric value as their key then they save that selection and go off to another page, do something else and then come back to the original page and need to load their selections into that page. What is the quickest and most efficient way of storing and reusing that data? In a text file saved with the session id? In a temp db table? In the session data itself (db sessions so size isn't a limit) using a serialised string or using gzcompress or gzencode? Any advice or insight would be great! Thank you!!!!

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• When to use Hibernate?

  - by Ramo

  Hi All, I was asked in an interview this question so I answered with the following: -Better Performance: - Efficient queries. - 1st and 2nd level caching. - Good caching gives better scalability. - Good Database Portability: - Changing the DB is as easy as changing the dialect configuration. - Increased Developer Productivity: - Think only in object terms not in query language terms. But I also feel that systems fall in one of the below categories, and Hibernate may not be suited for all these cases, I'm interested in your thoughts about this, do you agree with me? please let me know when would use HB in the following case and why. Write Only Systems: Read Only Systems: Write Mostly Systems: Read Mostly Systems: Regards Ramo

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• Custom deleters for std::shared_ptrs

  - by Kristian D'Amato

  Is it possible to use a custom deleter after creating a std::shared_ptr without using new? My problem is that object creation is handled by a factory class and its constructors & destructors are protected, which gives a compile error, and I don't want to use new because of its drawbacks. To elaborate: I prefer to create shared pointers like this, which doesn't let you set a custom deleter (I think): auto sp1 = make_shared<Song>(L"The Beatles", L"Im Happy Just to Dance With You"); Or I can create them like this, which does let met set a deleter through an argument: auto sp2(new Song, MyDeleterFunc); But the second one uses new, which AFAIK isn't as efficient as the top sort of allocation. Maybe this is clearer: is it possible to get the benefits of make_shared<> as well as a custom deleter? Would that mean having to write an allocator?

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• How to rate a connect four game situation in java

  - by MrPink

  Hey, I am trying to write a simple AI for a "Get four" game. The basic game principles are done, so I can throw in coins of different color, and they stack on each other and fill a 2D Array and so on and so forth. until now this is what the method looks like: public int insert(int x, int color) //0 = empty, 1=player1 2=player2" X is the horizontal coordinate, as the y coordinate is determined by how many stones are in the array already, I think the idea is obvious. Now the problem is I have to rate specific game situations, so find how many new pairs, triplets and possible 4 in a row I can get in a specific situation to then give each situation a specific value. With these values I can setup a "Game tree" to then decide which move would be best next (later on implementing Alpha-Beta-Pruning). My current problem is that I can't think of an efficient way to implement a rating of the current game situation in a java method. Any ideas would be greatly appreciated! greetings from Germany Mr. Pink

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• Is shortening properties names worth it?

  - by raam86

  in how to node Blog rolling with node.js and mongoDB the author mentions it's a good idea to shorten proprieties names: ....oft-reported issue with mongoDB is the size of the data on the disk... each and every record stores all the field-names .... This means that it can often be more space-efficient to have properties such as 't', or 'b' rather than 'title' or 'body', however for fear of confusion I would avoid this unless truly required! I am aware of solutions of how to do it I am more intrested in when is it truly required?

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• Fastest way to sort files

  - by Werner

  Hi, I have a huge text file with lines like: -568.563626 159 33 -1109.660591 -1231.295129 4.381508 -541.181308 159 28 -1019.279615 -1059.115975 4.632301 -535.370812 155 29 -1033.071786 -1152.907805 4.420473 -533.547101 157 28 -1046.218277 -1063.389677 4.423696 What I want is to sort the file, depending on the 5th column, so I would get -568.563626 159 33 -1109.660591 -1231.295129 4.381508 -535.370812 155 29 -1033.071786 -1152.907805 4.420473 -533.547101 157 28 -1046.218277 -1063.389677 4.423696 -541.181308 159 28 -1019.279615 -1059.115975 4.632301 For this I use: for i in file.txt ; do sort -k5n $i ; done I wonder if this is the fastest or more efficient way Thanks

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• Function chaining depending on boolean result

  - by Markive

  This is just an efficiency question really.. I'm interested to know if there is a more efficient or logical way that people use to handle this sort of scenario. In my asp.net application I am running a script to generate a new project my code at the top level looks like this: Dim ok As Boolean = True ok = createFolderStructure() If ok Then ok = createMDB() If ok Then ok = createProjectConfig() If ok Then ok = updateCompanyConfig() I create a boolean and each function returns a boolean result, the next function in this chain will only run if the previous one was successful. I do this because an asp.net application will continue to run through the page life cycle unless there is an unhandled exception and I don't want my whole application to be screwed up if something in the chain goes wrong (there is a lot of copying and deleting of files etc.. in this example). I was just wondering how other people handle this scenario? the vb.net single line if statement is quite succinct but I'm wondering if there is a better way?

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• Why it is necessary to put comments on check-ins? [closed]

  - by Mik Kardash

  In fact, I always have something to put in when I perform a check-in of my code. However, the question I have is - Is it really so necessary? Does it help so much? How? From one point of view, comments can help you to keep track of changes performed with every check-in. Thus, I will be able to analyze the changes and identify a hypothetic problem a little bit quicker. On the other hand, it takes some time to write useful information into check-in. Is it worth it? What are the pros and cons of writing comments to every check-in? Is there any way to write "efficient" check-in comments?

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• Displaying objects based on if a user is logged in or not

  - by MaxMackie

  I'm learning about PHP sessions for user authentication on my website. I know how to restrict the viewing of a complete page using sessions (simply check if the 'uid' session variable is set and if it is, show content, if not redirect to an error). However I'm trying to figure out the best way to selectively show and hide different objects (div, text, images) based on if a user is logged in or not. Is it as simple as checking for the 'uid' session variable and displaying based on if it set or not? Is there a more efficient way of doing this id there are a lot of conditional elements on a page?

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