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• How do I Put Several Select Statements into Different Columns

  - by Russ Bradberry

  I basically have 7 select statement that I need to have the results output into separate columns. Normally I would use a crosstab for this but I need a fast efficient way to go about this as there are over 7 billion rows in the table. I am using the vertica database system. Below is an example of my statements: SELECT COUNT(user_id) AS '1' FROM event_log_facts WHERE date_dim_id=20100101 SELECT COUNT(user_id) AS '2' FROM event_log_facts WHERE date_dim_id=20100102 SELECT COUNT(user_id) AS '3' FROM event_log_facts WHERE date_dim_id=20100103 SELECT COUNT(user_id) AS '4' FROM event_log_facts WHERE date_dim_id=20100104 SELECT COUNT(user_id) AS '5' FROM event_log_facts WHERE date_dim_id=20100105 SELECT COUNT(user_id) AS '6' FROM event_log_facts WHERE date_dim_id=20100106 SELECT COUNT(user_id) AS '7' FROM event_log_facts WHERE date_dim_id=20100107

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• Finding all points common to two circles

  - by Dustin I.

  In Python, how would one find all points common to two circles? For example, imagine a Venn diagram-like intersection of two (equally sized) circles, with center-points (x1,y1) and (x2,y2) and radii r1=r2. Additionally, we already know the two points of intersection of the circles are (xi1,yi1) and (xi2,yi2). How would one generate a list of all points (x,y) contained in both circles in an efficient manner? That is, it would be simple to draw a box containing the intersections and iterate through it, checking if a given point is within both circles, but is there a better way?

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• mvc contrib pager question - AsPagination

  - by csetzkorn

  Hi, I might be wrong but is the AsPagination method not very inefficient as it sucks all the data from a repository first to initialise TotalItems etc.? So paging is not used to make the data access more efficient. I have not found any examples which use a repository and 'true' paging (i.e. uses TOP etc. in the atcual SQL). How do I use the Pager if I have a repository method with this signature: IList GetData(int? page, out int TotalItems) Any feedback would be very much appreciated. Thanks. Christian

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• Conceptual question about NSAutoreleasePools

  - by ryyst

  In my Cocoa program, wouldn't a really simple way of dealing with autoreleased objects be to just create a timer object inside the app delegate that calls the following method e.g. every 10 seconds: if (pool) { // Release & drain the current pool to free the memory. [pool release]; } // Create a new pool. pool = [[NSAutoreleasePool alloc] init]; The only problems I can imagine are: 1) If the above code runs in a separate thread, an object might get autoreleased between the release call to the old pool and the creation of the new pool - that seems highly unlikely though. 2) It's obviously not that efficient, because the pool might get released if there's nothing in it. Likewise, in the 10 second gap, many many objects might be autoreleased, causing the pool to grow a lot. Still, the above solution seems pretty suitable to small and simple projects. Why doesn't anybody use it? What's the best practice of using NSAutoreleasePools?

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• non-servlet JSP

  - by h2g2java

  I realise there are EL and near EL frameworks like StringTemplate, JUEL, Velocity, etc. However, I am not asking for list of alternatives to JSTL/EL. I came across a package more than a year ago, someone who wrote a util that emulates the functionality of JSP for non-servlet env, i.e., JSP composition which does not need a "servlet container" to function. I ignored it and now I think it would be helpful to me and I need help to recall what it is. My actual motivation is similar to what StringTemplate, JUEL, Velocity would offer to help me compose SQL blocks, HTML blocks but I am thinking that JSPs are precompiled into bytecode and JSPs are more run-time efficient since run-time parsing is done no more than once. So actually, recommendation for alternatives would be acceptable as long as the templates are precompiled into bytecode. But I still prefer the JSP emulator.

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• Help me understand Rails eager loading

  - by aaronrussell

  I'm a little confused as to the mechanics of eager loading in active record. Lets say a Book model has many Pages and I fetch a book using this query: @book = Book.find book_id, :include => :pages Now this where I'm confused. My understanding is that @book.pages is already loaded and won't execute another query. But suppose I want to find a specific page, what would I do? @book.pages.find page_id # OR... @book.pages.to_ary.find{|p| p.id == page_id} Am I right in thinking that the first example will execute another query, and therefore making the eager loading pointless, or is active record clever enough to know that it doesn't need to do another query? Also, my second question, is there an argument that in some cases eager loading is more intensive on the database and sometimes multiple small queries will be more efficient that a single large query? Thanks for your thoughts.

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• code throws std::bad_alloc, not enough memory or can it be a bug?

  - by Andreas

  I am parsing using a pretty large grammar (1.1 GB, it's data-oriented parsing). The parser I use (bitpar) is said to be optimized for highly ambiguous grammars. I'm getting this error: 1terminate called after throwing an instance of 'std::bad_alloc' what(): St9bad_alloc dotest.sh: line 11: 16686 Aborted bitpar -p -b 1 -s top -u unknownwordsm -w pos.dfsa /tmp/gsyntax.pcfg /tmp/gsyntax.lex arbobanko.test arbobanko.results Is there hope? Does it mean that it has ran out of memory? It uses about 15 GB before it crashes. The machine I'm using has 32 GB of RAM, plus swap as well. It crashes before outputting a single parse tree. The parser is an efficient CYK chart parser using bit vector representations; I presume it is already near the limit of memory efficiency. If it really requires too much memory I could sample from the grammar rules, but this will decrease parse accuracy of course.

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• Complicated MySQL query?

  - by Scott

  I have two tables: RatingsTable that contains a ratingname and a bit whether it is a positive or negative rating: Good 1 Bad 0 Fun 1 Boring 0 FeedbackTable that contains feedback on things...the person rating, the rating and the thing rated. The feedback can be determined if it's a positive or negative rating based on RatingsTable. Jim Chicken Good Jim Steak Bad Ted Waterskiing Fun Ted Hiking Fun Nancy Hiking Boring I am trying to write an efficient MySQL query for the following: On a page, I want to display the the top 'things' that have the highest proportional positive ratings. I want to be sure that the items from the feedback table are unique...meaning, that if Jim has rated Chicken Good 20 times...it should only be counted once. At some point I will want to require a minimum number of ratings (at least 10) to be counted for this page as well. I'll want to to do the same for highest proportional negative ratings, but I am sure I can tweak the one for positive accordingly.

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• set / line intersection solution

  - by Xavier

  I have two lists in python and I want to know if they intersect at the same index. Is there a mathematical way of solving this? For example if I have [9,8,7,6,5] and [3,4,5,6,7] I'd like a simple and efficient formula/algorithm that finds that at index 3 they intersect. I know I could do a search just wondering if there is a better way. I know there is a formula to solve two lines in y = mx + b form by subtracting them from each other but my "line" isn't truly a line because its limited to the items in the list and it may have curves. Any help is appreciated.

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• Updating Silverlight with data. JSON or WCF?

  - by Alastair Pitts

  We will be using custom Silverlight 4.0 controls on our ASP.NET MVC web page to display data from our database and was wondering what the most efficient method was? We will be having returned values of up to 100k records (of 2 properties per record). We have a test that uses the HTML Bridge from Javascript to Silverlight. First we perform a post request to a controller action in the MVC web app and return JSON. This JSON is then passed to the Silverlight where it is parsed and the UI updated. This seems to be rather slow, with the stored procedure (the select) taking about 3 seconds and the entire update in the browser about 10-15sec. Having a brief look on the net, it seems that WCF is another option, but not having used it, I wasn't sure of it's capability or suitability. Does anyone have any experiences or recommendations?

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• Help me find some good 'Reflection' reading materials??

  - by IbrarMumtaz

  If it wasn't you guys I would've never discovered Albahari.com's free threading ebook. My apologies if I come off as being extremely lazy but I need to make efficient use of my time and make sure am not just swallowing any garbage of the web. Therefore I am looking for the best and most informative and with a fair bit of detail for the Reflection chapter in .Net. Reflection is something that comes up time and time again and I want to extend my reading from what I know already from the official 70-536 book. I'm not a big fan of MSDN but at the moment that's al I'm using. Anyone got any other good published reading material off the inter web that can help revision for the entrance exam??? Would be greatly appreciated !!! Thanks in Advance, Ibrar

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• Django - Tips to avoid repeating code in views

  - by D Roddis

  I'm moving from a PHP background into Django development via python, mostly for the sake of tackling a MVC (or MVT) that I feel makes the most sense, although in this pattern I've started to notice a lot of repeated code in my views. For example, when logged in I have information regarding the user that I would like to appear on every page, although when using render_to_response and in every view this is required I have to grab the information and pass it to the render_to_response function. I'm wondering what would be the most efficient way to cut down on the duplicate code which would in essence be required in all views in a particular app. Thanks in advance.

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• Ways to divide the high/low byte from a 16bit address?

  - by Grissiom

  Hello, I'm developing a software on 8051 processor. A frequent job is to divide the high and low byte of a 16bit address. I want to see there are how many ways to achieve it. The ways I come up so far are: (say ptr is a 16bit pointer, and int is 16bit int) ADDH = (unsigned int) ptr >> 8; ADDL = (unsigned int) ptr & 0x00FF; and ADDH = ((unsigned char *)&ptr)[0]; ADDL = ((unsigned char *)&ptr)[1]; Does anyone have any other bright ideas? ;) And anyone can tell me which way is more efficient?

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• Get enum by it's inner field

  - by zeroed

  Hi! Have enum with inner fields, kind of map. Now I need to get enum by it's inner field. Wrote this: package test; /** * Test enum to test enum =) */ public enum TestEnum { ONE(1), TWO(2), THREE(3); private int number; TestEnum(int number) { this.number = number; } public TestEnum findByKey(int i) { TestEnum[] testEnums = TestEnum.values(); for (TestEnum testEnum : testEnums) { if (testEnum.number == i) { return testEnum; } } return null; } } But it's not very efficient to look up through all enums each time I need to find appropriate instance. Is there any other way to do the same?

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• Parsing dbpedia JSON in Python

  - by givp

  Hello, I'm trying to get my head around the dbpedia JSON schema and can't figure out an efficient way of extracting a specific node: This is what dbpedia gives me: http://dbpedia.org/data/Ceramic_art.json I've got the whole thing as a JSON object in Python but don't really understand how to get the english abstract from this data. I've gotten this far: u = "http://dbpedia.org/data/Ceramic_art.json" data = urlfetch.fetch(url=u) json_data = json.loads(data.content) for j in json_data["http://dbpedia.org/resource/Ceramic_art"]: if(j == "http://dbpedia.org/ontology/abstract"): print "it's here" Not sure how to proceed from here. As you can see there are multiple languages. I need to get the english abstract. Thanks for your help, g

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• taking intersection of N-many lists in python

  - by user248237

  what's the easiest way to take the intersection of N-many lists in python? if I have two lists a and b, I know I can do: a = set(a) b = set(b) intersect = a.intersection(b) but I want to do something like a & b & c & d & ... for an arbitrary set of lists (ideally without converting to a set first, but if that's the easiest / most efficient way, I can deal with that.) I.e. I want to write a function intersect(*args) that will do it for arbitrarily many sets efficiently. What's the easiest way to do that? EDIT: My own solution is reduce(set.intersection, [a,b,c]) -- is that good? thanks.

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• Save UIView's representation to file.

  - by fish potato

  What is the easiest way to save UIView's representation to file? My solution is, UIGraphicsBeginImageContext(someView.frame.size); [someView drawRect:someView.frame]; UIImage *image = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); NSString* pathToCreate = @"sample.png"; NSData *imageData = [NSData dataWithData:UIImagePNGRepresentation(image)]; [imageData writeToFile:pathToCreate atomically:YES]; but it seems tricky, and I think there must be more efficient way to do this.

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• What is the best way to convert a hexidecimal string to a byte array (.NET)?

  - by Robert Wagner

  I have a hexidecimal string that I need to convert to a byte array. The best way (ie efficient and least code) is: string hexstr = "683A2134"; byte[] bytes = new byte[hexstr.Length/2]; for(int x = 0; x < bytes.Length; x++) { bytes[x] = Convert.ToByte(hexstr.Substring(x * 2, 2), 16); } In the case where I have a 32bit value I can do the following: string hexstr = "683A2134"; byte[] bytes = BitConverter.GetBytes(Convert.ToInt32(hexstr, 16)); However what about in the general case? Is there a better built in function, or a clearer (doesn't have to be faster, but still performant) way of doing this? I would prefer a built in function as there seems to be one for everything (well common things) except this particular conversion.

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• mysql filtering result using left outer join

  - by user288178

  my query: SELECT content.*, activity_log.content_id FROM content LEFT JOIN activity_log ON content.id = activity_log.content_id AND sess_id = '$sess_id' WHERE activity_log.content_id IS NULL AND visibility = $visibility AND content.reported < ".REPORTED_LIMIT." AND content.file_ready = 1 LIMIT 1 The purpose of that query is to get 1 row from the content table that has not been viewed by the user (identified by session_id), but it still returns contents that have been viewed. What is wrong? ( I have checked the table making sure that the content_ids are there) Note: I think this is more efficient than using subqueries, thoughts?

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• Get notified/receive explicit intents when an activity starts

  - by qtips

  Hi, I am developing an application than gets notified when an activity chosen by a user is started. For this to work, the best approach would be to register a broadcastreceiver for ACTION_MAIN explicit intents, which as far as I know doesn't work (because these intents have specific targets). Another, probably less efficient approach, is to use the system ActivityManager and poll on the getRunningTask() which returns a list of all running tasks at the moment. The polling can be done by a background service. By monitoring the changes in this list, I can see whether an activity is running or not, so that my application can get notified. The downside is ofcourse the polling. I have not tried this yet, but I think that this last approach will probably work. Does anyone know of a better approach(es) or suggestions which are less intensive?

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• Using PHP, can I put variables inside of variables?

  - by Rob

  For example, take this code: $ch = curl_init($resultSet['url']."?get0=get0&get1=".$get1."&get2=".$get2."&get3=".$get3); This of course, looks very ugly, and kind of a pain in the ass to read. So my question is, would I be able to use something like this: $allgets ="?act=phptools&host=".$host."&time=".$duration."&port=".$port; $ch = curl_init($resultSet['url'] . $allgets); Very simple question I suppose, but my server is undergoing maintenance, so I can't upload it and test it myself. I suppose a yes or no answer will suffice, but if you have a more efficient way of doing this, that would be even better. :)

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• Resetting Objects vs. Constructing New Objects

  - by byronh

  Is it considered better practice and/or more efficient to create a 'reset' function for a particular object that clears/defaults all the necessary member variables to allow for further operations, or to simply construct a new object from outside? I've seen both methods employed a lot, but I can't decide which one is better. Of course, for classes that represent database connections, you'd have to use a reset method rather than constructing a new one resulting in needless connecting/disconnecting, but I'm talking more in terms of abstraction classes. Can anyone give me some real-world examples of when to use each method? In my particular case I'm thinking mostly in terms of ORM or the Model in MVC. For example, if I would want to retrieve a bunch of database objects for display and modify them in one operation.

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• All Permutations of a string when corresponding characters are not in the same place

  - by r20rock

  I need all possible permutations of a given string such that no character should remain at the same place as in the input string. Eg. : for input "ask" Output: all possible permutaions like "ksa", "kas"... such that 'a' is not in the 1st position , 's' is not in the 2nd positions and so on... in any permutation. I only need the count of such possible permutations I can do this by generating all permutations and filtering them but I need a very efficient way of doing this. All characters in the string are "UNIQUE" Preferred language C++.

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• Java 2D clip area to shape

  - by user2923880

  I'm quite new to graphics in java and I'm trying to create a shape that clips to the bottom of another shape. Here is an example of what I'm trying to achieve: Where the white line at the base of the shape is the sort of clipped within the round edges. The current way I am doing this is like so: g2.setColor(gray); Shape shape = getShape(); //round rectangle g2.fill(shape); Rectangle rect = new Rectangle(shape.getBounds().x, shape.getBounds().y, width, height - 3); Area area = new Area(shape); area.subtract(new Area(rect)); g2.setColor(white); g2.fill(area); I'm still experimenting with the clip methods but I can't seem to get it right. Is this current method ok (performance wise, since the component repaints quite often) or is there a more efficient way? Thanks in advance.

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• Replacing multiple patterns in a block of data

  - by VikrantY

  Hi All, I need to find the most efficient way of matching multiple regular expressions on a single block of text. To give an example of what I need, consider a block of text: "Hello World what a beautiful day" I want to replace Hello with "Bye" and "World" with Universe. I can always do this in a loop ofcourse, using something like String.replace functions availiable in various languages. However, I could have a huge block of text with multiple string patterns, that I need to match and replace. I was wondering if I can use Regular Expressions to do this efficiently or do I have to use a Parser like LALR. I need to do this in JavaScript, so if anyone knows tools that can get it done, it would be appreciated.

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