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  • Instantiating a context in LINQ to Entities

    - by Jagd
    I've seen two different manners that programmers approach when creating an entity context in their code. The first is like such, and you can find it all over the MSDN code examples: public void DoSomething() { using TaxableEducationEntities context = new TaxableEducationEntities()) { // business logic and whatever else } } The second is to create the context as a private attribute in some class that encapsulates your business logic. So you would have something like: public class Education_LINQ { private TaxableEducationEntities context = new TaxableEducationEntities(); public void DoSomething() { var result = from a in context.luAction select a; // business logic and whatever else } } Which way is more efficient? Assume that you have two methods, one called DoSomething1() and another called DoSomething2(), and both methods incorporate the using statement to open the context and do whatever with it. Were you to call one method after the other, would there be any superfluous overhead going on, since essentially both methods create the context and then clean it up when they're done? As opposed to having just one private attribute that is created when a class object is instantiated, and then in turn cleaned up when the object goes out of scope?

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  • How to return variable datatypes from a method

    - by Praesagus
    I have a method whose callers require different datatypes. I could repeat the requisite conversions a dozen times by putting them in each of the callers, but it seems much more efficient to do it once in the called method. public String myMethod(String myArg) { return DoSomething(myArg); } public Int32 myMethod(String myArg) { return Convert.ToInt32(DoSomething(myArg)); } private String DoSomething(key) { return SomeList[key]; } If I have multiple methods that pull data from SomeList and have to utilize different data types then in each I have to do a type conversion. Examples might be session variables or query or form requests or any other number of things. In VB I could say Function myMethod(myArg as String) as Variant myMethod=DoSomething(myArg) End Function Sorry if the original post was not very clear. I hope this makes more sense. Thanks

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  • Web Services: more frequent "small" calls, or less frequent "big" calls

    - by Klay
    In general, is it better to have a web application make lots of calls to a web service getting smaller chunks of data back, or to have the web app make fewer calls and get larger chunks of data? In particular, I'm building a Silverlight app that needs to get large amounts of data back from the server in response to a query created by a user. Each query could return anywhere from a few hundred records to a few thousand. Each record has around thirty fields of mostly decimal-type data. I've run into the situation before where the payload size of the response exceeded the maximum allowed by the service. I'm wondering whether it's better (more efficient for the server/client/web service) to cut this payload vertically--getting all values for a single field with each call--or horizontally--getting batches of complete records with each call. Or does it matter?

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  • How to rotate an SSE/AVX vector

    - by user1584773
    I need to perform a rotate operation with as little clock cycle as possible. In the first case let's assume __m128i as source and dest type source: || A0 || A1 || A2 || A3 || dest : || A1 || A2 || A3 || A0 || dest = (__m128i)_mm_shuffle_epi32((__m128i)source, _MM_SHUFFLE(0,3,2,1)); Now I want to do the same whit AVX intrinsics So let's assume this time __m256i as source and dest type source: || A0 || A1 || A2 || A3 || A4 || A5 || A6 || A7 || dest : || A1 || A2 || A3 || A4 || A5 || A6 || A7 || A0 || The Avx intrinsics is missing most of the corresponding SSE integer operations. Maybe there is some way go get the desider output working with the floating point version. I've tryed with: dest = (__m256i)_mm256_shuffle_ps((__m256)source, (__m256)source, _MM_SHUFFLE(0,3,2,1)); but what I get is: || A0 || A2 || A3 || A4 || A5 || A6 || A7 || A1 || Any Idea on how to solve this in an efficient way? (without mixing SSE and AVX operation and without "manually" inverting A0 and A1 Thanks in advance!

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  • store everything only once, smarter

    - by hsmit
    In the digital world a lot is stored multiple times. As a thought experiment or creative challenge I want you to think about making this more efficient and maybe reuse more. Think of the following cases: an mp3 track is downloaded multiple times, copied over various devices on website a login form is often rebuild many times, why not reuse more code? words themselves are used many times questions and answers are accidentally saved at many places in parallel images or photos often describe the same data (Eiffel tower, Golden gate, Taj Mahal) etc etc Are you aware of solutions? Or are you thinking about similar topics? Ideas? Blueprints? I'd love to hear from you!

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  • Tilecache standalone server with nginx in production environment

    - by farhan khan
    Hi, I am really new to tilecache. I would like to know how good is the tilecache http server that comes with the tilecache installation. Is it practical to deploy it behind nginx in production environment? (i.e. nohup tilecache_http_server.py -p 8000 & and then editting the nginx.conf). The VPS we are using has nginx installed already so I thought that would be the easiest for me. However, how practical/efficient is it?

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  • OpenLayers, Layers: Tiled vs. single tile

    - by Chau
    Each time we add a new layer to our OpenLayers based website (data provided primarily by a GeoServer server), we discuss whether to use a single-tile or a tiled approach. Some of the parameters we evaluate are the following: Using the tiled approach we get: Slow but continuous buildup of the viewport Lots of small images Client side caching possibilities Blocking of the loading pipeline (6 requests at a time) Jerky feeling when navigating during load Using the single-tile approach we get: Smoother feeling when navigating during load Time delay before layer is loaded One large image for each layer No caching of the single tile We have a lot of data editing in the layers, thus a tile-cache might not be that efficient. Are there any best-practices when it comes to tiling? Progressing towards infinitely fast hardware and unlimited data connections, the discussion becomes irrelevant, but what configuration do you percieve as the most user-pleasing?

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  • Must have JavaScript pro developer tools, libs, utilities and workshop configuration.

    - by WooYek
    This is a followup question to the Pro JavaScript programmer interview questions (with answers). What is considered professional and industrial standard for a professional browser side Java Script developer when it comes to his workshop configuration, and maybe from-concept-to-shipment process? What are the most popular IDE's, utilities and probably libraries, not limited to the free ones. These that can help cut development time (eg. IDE), help with achieve better quality (eg. unit testing tools), reliability and maintainability. I'm looking for a baseline to which I could compare potential candidates based on their ability to keep their tools sharp and workshop efficient (pro's should invest time&money in good tools, right?).

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  • Huge dataset point in polygon in .net (collision detection)

    - by Rickard Liljeberg
    I have a pretty big mesh with polygons, usually triangles but sometimes rectangles. Each point in my mesh has a value (value has nothing to do with coordinates). Now I am creating a second mesh in the same coordinate-space as the old mesh. I now want to interpolate out values for all points (vertices) in the new mesh using the values from the old mesh. Now I could loop each polygon in the new mesh and detect which old vertices are in each polygon by making 2d collision detection (altho even this I don't get to function properly so if anyone has simple and fast code for 2d collision detection (triangle is enough) I would gladly see it). However to my main point again. looping each old vertice for each new polygon seems less than efficient. is there a better way?

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  • Discrete and Continuous Classifier on Sparse Data

    - by Chris S
    I'm trying to classify an example, which contains discrete and continuous features. Also, the example represents sparse data, so even though the system may have been trained on 100 features, the example may only have 12. What would be the best classifier algorithm to use to accomplish this? I've been looking at Bayes, Maxent, Decision Tree, and KNN, but I'm not sure any fit the bill exactly. The biggest sticking point I've found is that most implementations don't support sparse data sets and both discrete and continuous features. Can anyone recommend an algorithm and implementation (preferably in Python) that fits these criteria? Libraries I've looked at so far include: Orange (Mostly academic. Implementations not terribly efficient or practical.) NLTK (Also academic, although has a good Maxent implementation, but doesn't handle continuous features.) Weka (Still researching this. Seems to support a broad range of algorithms, but has poor documentation, so it's unclear what each implementation supports.)

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  • effective retrieve for a voting system in PHP and MySQL

    - by Adnan
    Hello, I have a system where registered users can vote up/vote down comment for a picture. Something very similar to SO's voting system. I store the votes in a table with values as such; vote_id | vote_comment_id | vote_user_id | vote_date | vote_type Now I have few a question concerned the speed and efficiency for the following; PROB: Once a user opens the picture page with comments I need, if that user has already voted UP/DOWN a comment to show it like; "you voted up" or "you voted down" next to the comment (in SO it the vote image is highlighted) MY POSSIBLE SOL: Right now when I open a picture page for each comment I loop thru, I loop thru my table of votes as well and check if a user has voted and show the status (I compare the vote_user_id with the user's session). How efficient is this? Anyone have a better approach to tackle this kind of problem?

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  • AJAX, PHP, XML, and cascading drop-down lists

    - by Dave Jarvis
    What PHP libraries would you recommend to implement the following: Three dependent drop-down lists Three XML data sources AJAX-based Essentially, I'd like to create an XML database and wire up a form that allows the user to select three different dependent parameters: User clicks Region User clicks District (filtered by Region) User clicks Station (filtered by District) Even though I would like to use PHP and XML, the general problem is: One XHTML form Three dependent, cascading drop-down lists Three flat files (no relational database) for the list data The solution must be efficient, simple, reliable, and cross-browser. What technologies would you recommend to solve the problem? Thank you!

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  • Multilangual Unicode rendering in opengl

    - by sum1stolemyname
    Hi Folks, I have to extend an OpenGL-Rendering System to support international characters (especially Hebrew, Arabic and cyrillic). Development Platform is Windows(XP|Vista|7), Alas using Embercardero Delphi 2010. I currently use wglOutLineFont(...) to build my font's display list and glCallLists(length(m_Text), UNSIGNED_SHORT, PWchar(m_Text) ) to render my strings. While this is feasable for Latin-1 Characters, building the full unicode character set in advanced is pretty time-consuming (about 8.5 minutes on my machine), so i am looking for a more efficient solution. I thought about limiting the range from u+0020 - u+077f (latin, greek, cyrillic, arbaic and hebrew) to include just the glyphs i need, but that would just be a solution for my current needs, and will become insufficent once other encoding is needed. On the upside, i do not have to worry about left-to right or right-to left direction as our application can handle this already. I would expect this to be a well-known problem, so i would like to ask if there is any reference material on this on the web, or if you could share some insight on this?

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  • Raspberry Pi cluster, neuron networks and brain simulation

    - by jokoon
    Since the RBPI (Raspberry Pi) has very low power consumption and very low production price, it means one could build a very big cluster with those. I'm not sure, but a cluster of 100000 RBPI would take little power and little room. Now I think it might not be as powerful as existing supercomputers in terms of FLOPS or others sorts of computing measurements, but could it allow better neuronal network simulation ? I'm not sure if saying "1 CPU = 1 neuron" is a reasonable statement, but it seems valid enough. So does it mean such a cluster would more efficient for neuronal network simulation, since it's far more parallel than other classical clusters ?

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  • What is better, a STL list or a STL Map for 20 entries, considering order of insertion is as importa

    - by Abhijeet
    I have the following scenario.The implementation is required for a real time application. 1)I need to store at max 20 entries in a container(STL Map, STL List etc). 2)If a new entry comes and 20 entries are already present i have to overwrite the oldest entry with the new entry. Considering point 2, i feel if the container is full (Max 20 entries) 'list' is the best bet as i can always remove the first entry in the list and add the new one at last (push_back). However, search won't be as efficient. For only 20 entries, does it really make a big difference in terms of searching efficiency if i use a list in place of a map? Also considering the cost of insertion in map i feel i should go for a list? Could you please tell what is a better bet for me ?

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  • Django, making a page activate for a fixed time

    - by Hellnar
    Greetings I am hacking Django and trying to test something such as: Like woot.com , I want to sell "an item per day", so only one item will be available for that day (say the default www.mysite.com will be redirected to that item), Assume my urls for calling these items will be such: www.mysite.com/item/<number> my model for item: class Item(models.Model): item_name = models.CharField(max_length=30) price = models.FloatField() content = models.TextField() #keeps all the html content start_time = models.DateTimeField() end_time = models.DateTimeField() And my view for rendering this: def results(request, item_id): item = get_object_or_404(Item, pk=item_id) now = datetime.now() if item.start_time > now: #render and return some "not started yet" error templete elif item.end_time < now: #render and return some "item selling ended" error templete else: # render the real templete for selling this item What would be the efficient and clever model & templete for achieving this ?

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  • Optimization of running total calculation in SQL for multiple values per join condition

    - by Kiril
    I have the following table (test_table): date value --------------- d1 10.0 d1 20.0 d2 60.0 d2 10.0 d2 -20.0 d3 40.0 I calculate the running total as follows. I use the same query twice, because first I need to calculate the values for a specifi date, and afterwards I can calculate the running total. Otherwise, joining the two tables where date is not unique, I would get too many results from the join: SELECT t1.date, SUM(t2.value) AS total FROM (SELECT date, SUM(value) AS value FROM test_table GROUP BY date) AS t1 JOIN (SELECT date, SUM(value) AS value FROM test_table GROUP BY date) AS t2 ON t1.date >= t2.date GROUP BY t1.date ORDER BY t1.date This gives me (which is fine): date total ------------- d1 30.0 d2 80.0 d3 120.0 BUT, this query isn't very efficient, because I need to change conditions in two places, if necessary. In production, the test_table is a lot bigger ( 4 Mio. rows), and the query takes too much time to complete. Question: How can I avoid using the same query twice?

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  • Multiple outliers for two variable linear regression

    - by Dave Jarvis
    Problem Building on my previous question, the "extreme" outliers in the following graph are somewhat obvious: Question Given: T - Set of all temperatures Y - Set of all years ST - Sum of temperatures. SY - Sum of years. N - Number of elements T(n) - Temperature of the nth element in the temperature set How would you implement an efficient MySQL stored procedure or user-defined function (UDF) to determine if T(n) is an outlier? (If such an implementation already exists, that would be good to know as well.) Related Sites I am slowly working through these sites to get a better understanding of the problem: Multiple Outliers Detection Procedures in Linear Regression M-estimator Measure of Surprise for Outlier Detection Ordinary Least Squares Linear Regression Many thanks!

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  • jQuery parent of a parent

    - by Bloudermilk
    Hello, I am currently trying to find the parent of a parent of an element. I have a link being clicked that is in a <td>, and I'd like to get the <tr> object. Why wont "$(this).parent().parent()" work? What will? Thanks, Brendan Edit: It appears an error in my syntax was throwing the whole thing off. "$(this).parent().parent()" does in fact work, but I wound up going with $(this).closest('tr')" because it seems like the most efficient solution.

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  • Auto refresh web page

    - by Epitaph
    I have a web page which allows the user to carry out various operations that in turn modify the database. Also, this web application needs to keep track of various fields in database that keep changing with time. Is refreshing the page every few seconds the best possible way to implement this? For example, if there is a long list on the page requiring scrolling, it is hard to view the list since the page keeps resetting due to the refresh. I know, there are ways to retain the position of the scroll. But, could I use something more efficient?

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  • Paging enormous tables on DB2

    - by grenade
    We have a view that, without constraints, will return 90 million rows and a reporting application that needs to display paged datasets of that view. We're using nhibernate and recently noticed that its paging mechanism looks like this: select * from (select rownumber() over() as rownum, this_.COL1 as COL1_20_0_, this_.COL2 as COL2_20_0_ FROM SomeSchema.SomeView this_ WHERE this_.COL1 = 'SomeValue') as tempresult where rownum between 10 and 20 The query brings the db server to its knees. I think what's happening is that the nested query is assigning a row number to every row satisfied by the where clause before selecting the subset (rows 10 - 20). Since the nested query will return a lot of rows, the mechanism is not very efficient. I've seen lots of tips and tricks for doing this efficiently on other SQL platforms but I'm struggling to find a DB2 solution. In fact an article on IBM's own site recommends the approach that nhibernate has taken. Is there a better way?

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  • QProcess, QEventLoop - of any use for parallel-processing

    - by dlib
    I wonder whether I could use QEventLoop (QProcess?) to parallelize multiple calls to same function with Qt. What is precisely the difference with QtConcurrent or QThread? What is a process and an event loop more precisely? I read that QCoreApplication must exec() as early as possible in main() method, so that I wonder why it is different from main Thread. could you point as some efficient reference to processes and thread with Qt? I came through the official doc and those things remain unclear. Thanks and regards.

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  • What Does OSGi Solve?

    - by Pablo Fernandez
    I've read on wikipedia and other sites about OSGi, but I don't really see the big picture. It says that it's a component based platform, and that you can reload modules at runtime. Also the "practical example" given everywhere is the Eclipse Plugin Framework. My questions are: 1) What is the CLEAR and SIMPLE definition of OSGi? 2) What COMMON PROBLEMS does it solve? By "common problems" I mean problems we face everyday, like "what can OSGi do for making our jobs more efficient/fun/simple" Thanks.

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  • effective retrieve for a voting system in PHP

    - by Adnan
    Hello, I have a system where registered users can vote up/vote down comment for a picture. Something very similar to SO's voting system. I store the votes in a table with values as such; vote_id | vote_comment_id | vote_user_id | vote_date Now I have few a question concerned the speed and efficiency for the following; PROB: Once a user opens the picture page with comments I need, if that user has already voted UP/DOWN a comment to show it like; "you voted up" or "you voted down" next to the comment (in SO it the vote image is highlighted) MY POSSIBLE SOL: Right now when I open a picture page for each comment I loop thru, I loop thru my table of votes as well and check if a user has voted and show the status (I compare the vote_user_id with the user's session). How efficient is this? Anyone have a better approach to tackle this kind of problem?

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  • SQL model optimization question

    - by supermogx
    I need to keep track of number of "hits" on a particular item in a DB. The thing is that the "hits" should stay unique with a user ID, so if a user hits the item 3 times, it should still count for a hit of 1. Also, I need to display the total number of hits for a particular item. Is there a better way than to store each hits for each items by each users in a separate table? Would keeping the user ID in a string separated by commas a better and efficient way?

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