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• How to aggregate over few types with linq?

  - by Shimmy

  Can someone help me translate the following to one liner: Dim items As New List(Of Object) For Each c In ph.Contacts items.Add(New With {.Type = "Contact", .Id = c.ContactId, .Title = c.Title}) Next For Each c In ph.Persons items.Add(New With {.Type = "Person", .Id = c.PersonId, .Title = c.Title}) Next For Each c In ph.Jobs items.Add(New With {.Type = "Job", .Id = c.JobId, .Title = c.Title}) Next Is it possible to merge them all into one query or method line, I don't really care if this will be done with something other than linq, I am just looking for a more efficient way as I have a long list coming ahead, and the aggregating list will be strongly-typed using Dim list = blah blah

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• SQL Joing on a one-to-many relationship

  - by Harley

  Ok, here was my original question; Table one contains ID|Name 1 Mary 2 John Table two contains ID|Color 1 Red 2 Blue 2 Green 2 Black I want to end up with is ID|Name|Red|Blue|Green|Black 1 Mary Y Y 2 John Y Y Y It seems that because there are 11 unique values for color and 1000's upon 1000's of records in table one that there is no 'good' way to do this. So, two other questions. Is there an efficient way to get this result? I can then create a crosstab in my application to get the desired result. ID|Name|Color 1 Mary Red 1 Mary Blue 2 John Blue 2 John Green 2 John Black If I wanted to limit the number of records returned how could I do something like this? Where ((color='blue') AND (color<>'red' OR color<>'green')) So using the above example I would then get back ID|Name|Color 1 Mary Blue 2 John Blue 2 John Black I connect to Visual FoxPro tables via ADODB. Thanks!

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• WCF VS. Sockets

  - by kite

  Hello, I would like to know which of WCF or .NET Sockets is the more efficient and the more recommended in a game developpment scenario. Here are the different parts of the game : -a client/server communication to play on the internet -peer to peer on local network. I would like to know which technology you would use on these parts (wcf on both, socket on both, wcf on one and socket on the other...) and why, if possible. The game involved doesn't require a high communication frequency (3-4 per second is enough). Thanks, KiTe

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• Python regular expression implementation details

  - by Tom

  A question that I answered got me wondering: How are regular expressions implemented in Python? What sort of efficiency guarantees are there? Is the implementation "standard", or is it subject to change? I thought that regular expressions would be implemented as DFAs, and therefore were very efficient (requiring at most one scan of the input string). Laurence Gonsalves raised an interesting point that not all Python regular expressions are regular. (His example is r"(a+)b\1", which matches some number of a's, a b, and then the same number of a's as before). This clearly cannot be implemented with a DFA. So, to reiterate: what are the implementation details and guarantees of Python regular expressions? It would also be nice if someone could give some sort of explanation (in light of the implementation) as to why the regular expressions "cat|catdog" and "catdog|cat" lead to different search results in the string "catdog", as mentioned in the question that I referenced before.

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• Only show content when certain criteria is met?

  - by Elliot

  I'm wondering if theres a best practice for what I'm trying to accomplish... First we have the model categories, categories, has_many posts. Now lets say, users add posts. Now, I have a page, that I want to display only the current user's posts by category. Lets say we have the following categories: A, B, and C User 1, has posted in Categories A and B. In my view I have something like: @categories.each do |category| category.name @posts.each do |post| if post.category_id==category.id post content here end end end The problem with this, is I'm going to show the empty category, as well as the categories that do have content. Is there a more efficient way of going about this? As I don't want to show the empty categories. Best, Elliot

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• Polygon packing 2D

  - by Ilnur

  Hi! I have problem of packing 2 arbitrary polygons. I.e. we have 2 arbitrary polygons. We are to find such placement of this polygons (we could make rotations and movements), when rectangle, which circumscribes this polygons has minimal area. I know, that this is a NP-complete problem. I want to choose an efficient algorithm for solving this problem. I' looking for No-Fit-Polygon approach. But I could't find anywhere the simple and clear algorithm for finding the NFP of two arbitrary polygons.

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• Data Structure Behind Amazon S3s Keys (Filtering Data Structure)

  - by dimo414

  I'd like to implement a data structure similar to the lookup functionality of Amazon S3. For those of you who don't know what I'm taking about, Amazon S3 stores all files at the root, but allows you to look up groups of files by common prefixes in their names, therefore replicating the power of a directory tree without the complexity of it. The catch is, both lookup and filter operations are O(1) (or close enough that even on very large buckets - S3's disk equivalents - both operations might as well be O(1))). So in short, I'm looking for a data structure that functions like a hash map, with the added benefit of efficient (at the very least not O(n)) filtering. The best I can come up with is extending HashMap so that it also contains a (sorted) list of contents, and doing a binary search for the range that matches the prefix, and returning that set. This seems slow to me, but I can't think of any other way to do it. Does anyone know either how Amazon does it, or a better way to implement this data structure?

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• Alternative to Nested Loop For Comparison

  - by KGVT

  I'm currently writing a program that needs to compare each file in an ArrayList of variable size. Right now, the way I'm doing this is through a nested code loop: if(tempList.size()>1){ for(int i=0;i<=tempList.size()-1;i++) //Nested loops. I should feel dirty? for(int j=i+1;j<=tempList.size()-1;j++){ //*Gets sorted. System.out.println(checkBytes(tempList.get(i), tempList.get(j))); } } I've read a few differing opinions on the necessity of nested loops, and I was wondering if anyone had a more efficient alternative. At a glance, each comparison is going to need to be done, either way, so the performance should be fairly steady, but I'm moderately convinced there's a cleaner way to do this. Any pointers?

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• Python and Postgresql

  - by Ian

  Hi all, if you wanted to manipulate the data in a table in a postgresql database using some python (maybe running a little analysis on the result set using scipy) and then wanted to export that data back into another table in the same database, how would you go about the implementation? Is the only/best way to do this to simply run the query, have python store it in an array, manipulate the array in python and then run another sql statement to output to the database? I'm really just asking, is there a more efficient way to deal with the data? Thanks, Ian

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• How to disable Events for a while in Javascript or jQuery

  - by Tarik

  Hello, I am wondering if you guys know different approach to disable an event for a while. Let me elaborate this more : Lets say I have a div or button which has a subscriber to its onclick event. To prevent the double click when the the methods are doing some ajax things, these are the some of the ways we can do : Disable the button till the method finishes its job Unbind till the methods finishes its job and then bind it again. Use some kind of flagging system like boolean so it will prevent method from working more than once. So is there any other ways, maybe some javascript tricks or jQuery tricks which is more efficient and better practice. Thanks in advance.

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• Best Practices for working with files via c#

  - by user177883

  Application I work on generates several hundreds of files in a 15 minutes period of times. and the back end of the application takes these files and process them (updates database with those values). One problem is database locks. What are the best practices on working with several thousands of files to avoid locking and efficiently processing these files? Would it be more efficient to create a single file and process it? or process single file at a time? What are so common best practices?

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• How can let Qt Graphics View Framework support custom layers

  - by jnblue

  Qt's graphics view frameworks is very powerful, but I have not found a way to support custom layers. In Qt, there is a QGraphicsScene::ItemLayer,but QGraphicsScene renders all items are in this layer. I want manage the items with several layers, Just like Illustrator and CorelDraw. all the item only in the current layer will receive the event, be selected or get the key focus etc.. Other layers(not current layer) will not receive all scene event. The most reasons of using layers is I could catalogue a large number of items more clearly.And without needing transfer events to all the layers' items ,I think the graphics frameworks will be more efficient. The last question, does QGraphicsView support rendering server stacked graphics scenes at the same time? If support, I think the "custom layers" can be solved in this way. Thanks very much!

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• Developing ASP.NET MVC UI Extensions - best approach

  - by user252160

  What are the best practices in developing rich UI extensions for ASP.NET MVC (I mean asynchronous / partial loading, slick effects, skinning etc) ? I saw that Telerik has an MVC suite of extensions, but haven't tried them yet, so I cannot comment on them. My biggest concern as of the moment is how to structure the code of my extensions so that C#, ASP markup, and JQuery remain separate from each other, yet encapsulated in a way that the extension must be easy to distribute and reuse. I know that the user control approach had many flaws, yet it sort of allowed application developers to just reference a control, set some parameters and get it going in a few minutes. I'd like to achieve the same kind of portability/reusability as I still keep the code easy to extend and build upon. Now, some ideas that come to mind as topics for discussion are: template helpers vs. extension method helpers or a possible integration efficient use of jQuery - naming conventions - - asynchronous action loading - etc you can add whatever comes to your mind

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• Heuristic algorithm for load balancing among threads.

  - by Il-Bhima

  I'm working on a multithreaded program where I have a number of worker threads performing tasks of unequal length. I want to load-balance the tasks to ensure that they do roughly the same amount of work. For task T_i I have a number c_i which provides a good approximation to the amount of work that is required for that task. I'm looking for an efficient (O(N) N = num tasks or better) algorithm which will give me "roughly" a good load balance given the values of c_i. It doesn't have to be optimal, but I would like to be able to have some theoretical bounds on how bad the resulting allocations are. Any ideas?

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• Should I Make These Vectors Classes or Structs in C#

  - by dewald

  I am creating a geometry library in C# and I will need the following immutable types: Vector2f (2 floats - 8 bytes) Vector2d (2 doubles - 16 bytes) Vector3f (3 floats - 12 bytes) Vector3d (3 doubles - 24 bytes) Vector4f (4 floats - 16 bytes) Vector4d (4 doubles - 32 bytes) I am trying to determine whether to make them structs or classes. MSDN suggests only using a struct if the size if going to be no greater than 16 bytes. That reference seems to be from 2005. Is 16 bytes still the max suggested size? I am sure that using structs for the float vectors would be more efficient than using a class, but what should I do about the double vectors? Should I make them structs also to be consistent, or should I make them classes?

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• C or C++ to write a compiler?

  - by H.Josef

  I want to write a compiler for a custom markup language, I want to get optimum performance and I also want to have a good scalable design. Multi-paradigm programming language (C++) is more suitable to implement modern design patterns, but I think that will degrade performance a little bit (think of RTTI for example) which more or less might make C a better choice. I wonder what is the best language (C, C++ or even objective C) if someone wants to create a modern compiler (in the sense of complying to modern software engineering principles as a software) that is fast, efficient, and well designed.

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• Virtual Earth / Bing maps javascript file size

  - by Aquinas

  I am working with a site that uses virtual earth for its mapping. Unfortunately the file size of the referenced javascript file, ecn.dev.virtualearth.net/mapcontrol/mapcontrol.ashx?v=6.2, is 200 something kb before being expanded (to 970kb). As our site runs under https this file is not cached on the client, and can cause a few seconds delay to users, made more substantial in times of high load. My question is, is there anyway to get virtual earth to run smaller, or have more efficient lazy loading? At the moment it looks like our hands are tied.

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• Java .split() Method To Split XML Parameters

  - by Buzz Lightyear

  I have this line from an XML document: <?xml version="1.0" encoding="UTF-8"?> <svg xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg" contentScriptType="text/ecmascript" width="1024" zoomAndPan="magnify" contentStyleType="text/css" viewBox="0 0 1024 768" height="768" preserveAspectRatio="xMidYMid meet" version="1.0"> I want to be able to split it up, using the split method. For example i want to save each parameter into a String array. So i'd like: contentScriptType="text/ecmascript" width="1024" zoomAndPan="magnify" contentStyleType="text/css" viewBox="0 0 1024 768" height="768" etc etc to be saved into a string array, is there anyway to do this using the split method, or can anybody suggest an easier, more efficient way to do this?

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• Optimizing website - minification, sprites, etc...

  - by nivlam

  I'm looking at the product Aptimize Website Accelerator, which is an ISAPI filter that will concatenate files, minify css/javascript, and more. Does anyone have experience with this product, or any other "all-in-one" solutions? I'm interesting in knowing whether something like this would be good long-term, or would manually setting up all the components (integrate YUICompress into the build process, setting up gzip compression, tweaking expiration headers, etc...) be more beneficial? An all-in-one solution like this looks very tempting, as it could save a lot of time if our website is "less than optimal". But how efficient are these products? Would setting up the components manually generate better results? Or would the gap between the all-in-one solution and manually setting up the component be so small, that it's negligible?

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• Performance of DrawingVisual vs Canvas.OnRender for lots of constantly changing shapes

  - by romkyns

  I'm working on a game-like app which has up to a thousand shapes (ellipses and lines) that constantly change at 60fps. Having read an excellent article on rendering many moving shapes, I implemented this using a custom Canvas descendant that overrides OnRender to do the drawing via a DrawingContext. The performance is quite reasonable, although the CPU usage stays high. However, the article suggests that the most efficient approach for constantly moving shapes is to use lots of DrawingVisual instances instead of OnRender. Unfortunately though it doesn't explain why that should be faster for this scenario. Changing the implementation in this way is not a small effort, so I'd like to understand the reasons and whether they are applicable to me before deciding to make the switch. Why could the DrawingVisual approach result in lower CPU usage than the OnRender approach in this scenario?

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• Architecture of an image hosting site

  - by kamziro

  I'm sure many here are aware of image hosting sites, like imgur, min.us, photobucket etc. Not that I want to develop one, but besides just uploading the file, organising it in some directory somewhere, what architectural considerations are involved in these sites? Especially when there's millions of page views a day (like imgur, I'd imagine) I'm curious about this because it seems that a lot of sites (say, dating websites etc) would be pretty image intensive. Even if it's not for millions of page views, what are some basic architectural requirements of efficient image deliveries online?

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• MERGE -v- UPSERT

  - by Kevin Ross

  Hi, I have an application I’m writing in access with a SQL server backend. One of the most heavily used parts is where the users selects an answer to a question, a stored procedure is then fired which sees if an answer has already been given, if it has an UPDATE is executed, if not an INSERT is executed. This works just fine but now we have upgraded to SQL server 2008 express I was wondering if it would be better/quicker/more efficient to rewrite this SP to use the new MERGE command. Does anyone have any idea if this is faster than doing a SELECT followed by either an INSERT or UPDATE?

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• Opencv python and webcam

  - by Neil Benn

  Hello, I'm working with OpenCV on a beagleboard with ubuntu and OpenCV 1.1 interfaced via Python. I'm trying to set something up to capture a feed from a UVC compatible webcam (logitech C250). I have tested the webcam with luvcview and it works but only if I set the input format to YUV. If I run it in 'normal' mode I am getting back jpeg frames and something - somewhere is not happy! I'm trying to connect with the webcam in OpenCV as I want to get the image back from the webcam and run some analysis on it. As I have a limited device this seems to be the most efficient way of doing it - however I need to instruct the capturing system to capture in YUV and not jpeg. Is there a way of doing this (for example luvcview allow me to enter luvcview -f YUVY)? Cheers, Neil

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• Is a switch statement the fastest way to implement operator interpretation in Java

  - by Mordan

  Is a switch statement the fastest way to implement operator interpretation in Java public boolean accept(final int op, int x, int val) { switch (op) { case OP_EQUAL: return x == val; case OP_BIGGER: return x > val; case OP_SMALLER: return x < val; default: return true; } } In this simple example, obviously yes. Now imagine you have 1000 operators. would it still be faster than a class hierarchy? Is there a threshold when a class hierarchy becomes more efficient in speed than a switch statement? (in memory obviously not) abstract class Op { abstract public boolean accept(int x, int val); } And then one class per operator.

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• Core Data multi-threading

  - by JK

  My app starts by presenting a tableview whose datasource is a Core Data SQLite store. When the app starts, a secondary thread with its own store controller and context is created to obtain updates from the web for data in the store. However, any resulting changes to the store are not notified to the fetchedresults controller (I presume because it has its own coordinator) and consequently the table is not updated with store changes. What would be the most efficient way to refresh the context on the main thread? I am considering tracking the objectIDs of any objects changed on the secondary thread, sending those to the main thread when the secondary thread completes and invoking "[context refreshObject:....] Any help would be greatly appreciated.

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