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• Efficient synchronization of querying an array of resources

  - by Erel Segal Halevi

  There is a list of N resources, each of them can be queried by at most a single thread at a time. There are serveral threads that need to do the same thing at approximately the same time: query each of the resources (each thread has a different query), in arbitrary order, and collect the responses. If each thread loops over the resources in the same order, from 0 to N-1, then they will probably have to wait for each other, which is not efficient. I thought of letting the threads loop over the resources in a random permutation, but this seems too complex and also not so efficient, for example, for 2 resources and 2 threads, in half the cases they will choose the same order and wait for each other. Is there a simple and more efficient way to solve this?

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• How much detail should be in a project plan or spec?

  - by DeanMc

  I have an issue that I feel many programmers can relate to... I have worked on many small scale projects. After my initial paper brain storm I tend to start coding. What I come up with is usually a rough working model of the actual application. I design in a disconnected fashion so I am talking about underlying code libraries, user interfaces are the last thing as the library usually dictates what is needed in the UI. As my projects get bigger I worry that so should my "spec" or design document. The above paragraph, from my investigations, is echoed all across the internet in one fashion or another. When a UI is concerned there is a bit more information but it is UI specific and does not relate to code libraries. What I am beginning to realise is that maybe code is code is code. It seems from my extensive research that there is no 1:1 mapping between a design document and the code. When I need to research a topic I dump information into OneNote and from there I prioritise features into versions and then into related chunks so that development runs in a fairly linear fashion, my tasks tend to look like so: Implement Binary File Reader Implement Binary File Writer Create Object to encapsulate Data for expression to the caller Now any programmer worth his salt is aware that between those three to do items could be a potential wall of code that could expand out to multiple files. I have tried to map the complete code process for each task but I simply don't think it can be done effectively. By the time one mangles pseudo code it is essentially code anyway so the time investment is negated. So my question is this: Am I right in assuming that the best documentation is the code itself. We are all in agreement that a high level overview is needed. How high should this be? Do you design to statement, class or concept level? What works for you?

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• summer experiment: GWT & python for a trading game- arch question

  - by sadhu_

  Hi, As a summer learning experiment, I'm thinking of coding up a web front end for a trading game i wrote in python, that generates share prices and random snippets of text. I am sort of struggling with how this should work on the back-end though. I'd rather have my GWT client page interact with the python share price generator, than to try and re-code it in java. I suppose i could use an sqlite db, and then use jdbc to pick up the prices, but i was wondering if there is a better way, for me to be able to poll some python script either from my client page, or from the serverside java code ? I found this python wrapper, but i'm not sure how i could use it though: http://code.google.com/apis/visualization/documentation/dev/gviz_api_lib.html Thanks.

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• Caching issues with TDBadgedCell

  - by Wolfgang Schreurs

  This post is closely related to my previous post: http://stackoverflow.com/questions/2201256/tdbadgedcell-keeps-caching-the-badgenumber The "badge" from TDBadgedCell keeps caching the numbers. A very simple example is shown here: - (UITableViewCell *)tableView:(UITableView *)_tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; TDBadgedCell *cell = (TDBadgedCell *)[_tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[TDBadgedCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier]; [cell setAccessoryType:UITableViewCellAccessoryDisclosureIndicator]; } [cell setBadgeColor:[UIColor blackColor]]; [cell setBadgeNumber:[indexPath row]]; [[cell textLabel] setText:[NSString stringWithFormat:%@"%d", [indexPath row]]]; return cell; } Anyone has any clue why this happens? The textLabel and detailTextLabel don't cache the data. Any additonal info would be welcome as well, as I seem to have a lot of issues with the caching of graphics in UITableViewCells. Any best practices or other useful information would be most welcome.

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• update columns when value is numeric in tsql

  - by knittl

  i want to normalize date fields from an old badly designed db dump. i now need to update every row, where the datefield only contains the year. update table set date = '01.01.' + date where date like '____' and isnumeric(date) = 1 and date >= 1950 but this will not work, because sql does not do short circuit evaluation of boolean expressions. thus i get an error "error converting nvarchar '01.07.1989' to int" is there a way to work around this? the column also contains strings with a length of 4, which are not numbers (????, 5/96, 70/8, etc.) the table only has 60000 rows

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• How do API Keys and Secret Keys work?

  - by viatropos

  I am just starting to think about how api keys and secret keys work. Just 2 days ago I signed up for Amazon S3 and installed the S3Fox Plugin. They asked me for both my Access Key and Secret Access Key, both of which require me to login to access. So I'm wondering, if they're asking me for my secret key, they must be storing it somewhere right? Isn't that basically the same thing as asking me for my credit card numbers or password and storing that in their own database? How are secret keys and api keys supposed to work? How secret do they need to be? Are these applications that use the secret keys storing it somehow? Thanks for the insight.

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• Math - Adding with PHP

  - by Wayne

  Basically I can't get it right. I need something like this: if($p == 1) { $start = 0; $limit = 16; } The numbers must add on depending on the value of the $p, e.g. if $p is 5 then the values of $start and $limit would be: if($p == 5) { $start = 64; $limit = 80; } The math is to add 16, depending on the value of $p. Thanks.

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• Truly declarative language?

  - by gjvdkamp

  Hi all, Does anyone know of a truly declarative language? The behaviour I'm looking for is kind of what Excel does, where I can define variables and formulas, and have the formula's result change when the input changes (without having set the answer again myself) The behaviour I'm looking for is best shown with this pseudo code: X = 10 // define and assign two variables Y = 20; Z = X + Y // declare a formula that uses these two variables X = 50 // change one of the input variables ?Z // asking for Z should now give 70 (50 + 20) I've tried this in a lot of languages like F#, python, matlab etc, but every time i try this they come up with 30 instead of 70. Wich is correct from an imperative point of view, but i'm looking for a more declerative behaviour if you know what i mean. And this is just a very simple calculation. When things get more difficult it should handle stuff like recursion and memoization automagically. The code below would obviously work in C# but it's just so much code for the job, i'm looking for something a bit more to the point without all that 'technical noise' class BlaBla{ public int X {get;set;} // this used to be even worse before 3.0 public int Y {get;set;} public int Z {get{return X + Y;}} } static void main(){ BlaBla bla = new BlaBla(); bla.X = 10; bla.Y = 20; // can't define anything here bla.X = 50; // bit pointless here but I'll do it anyway. Console.Writeline(bla.Z);// 70, hurray! } This just seems like so much code, curly braces and semicolons that add nothing. Is there a language/ application (apart from Exel) that does this? Maybe I'm no doing it right in the mentioned langauges, or I've completely missed an app that does just this. I prototyped a language/ application that does this (along with some other stuff) and am thinking of productizing it. I just can't believe it's not there yet. Don't want to waste my time. Thanks in advance, Gert-Jan

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• Grails multi column indexes

  - by Kimble

  Can someone explain how to define multi column indexes in Grails? The documentation is at best sparse. This for example does not seem to work at all: http://grails.org/GORM+Index+definitions I've had some luck with this, but the results seems random at best. Definitions that works in one domain class does not when applied to another (with different names of course). http://www.grails.org/doc/1.1/guide/single.html#5.5.2.6%20Database%20Indices Some working examples and explanations would be highly appreciated!

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• Can 3D OpenGL game written in Python look good and run fast?

  - by praavDa

  I am planning to write an simple 3d(isometric view) game in Java using jMonkeyEngine - nothing to fancy, I just want to learn something about OpenGL and writing efficient algorithms (random map generating ones). When I was planning what to do, I started wondering about switching to Python. I know that Python didn't come into existence to be a tool to write 3d games, but is it possible to write good looking games with this language? I have in mind 3d graphics, nice effects and free CPU time to power to rest of game engine? I had seen good looking java games - and too be honest, I was rather shocked when I saw level of detail achieved in Runescape HD. On the other hand, pygame.org has only 2d games, with some starting 3d projects. Are there any efficient 3d game engines for python? Is pyopengl the only alternative? Good looking games in python aren't popular or possible to achieve? I would be grateful for any information / feedback.

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• Understanding The Convolution Matrix

  - by Ryan Naddy

  I am learning about the Convolution Matrix, and I understand how they work, but I don't understand how to know before hand what the output of a Matrix will look like. For example lets say I want to add a blur to an image, I could guess 10,000+ different combinations of numbers before I get the correct one. I do know though that this formula will give me a blur effect, but I have no idea why. float[] sharpen = new float[] { 1/9f, 1/9f, 1/9f, 1/9f, 1/9f, 1/9f, 1/9f, 1/9f, 1/9f }; Can anyone either explain to me how this works or point me to some article, that explains this? I would like to know before hand what a possible output of the matrix will be without guessing. Basically I would like to know why do we put that number in the filed, and why not some other number?

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• encoding of =1 in emails

  - by Maenny

  Hi folks, I have probably a stupid problem. In a script I generate a URL with GET parameters, something like 'www.mydomain.com/index.php?item=1234'. This URL will be sent by PHP through mail() in an UTF-8 encoding (the scriptfile itself also is utf-8). Now each time I have the GET-Parameter with two numbers after the '=' the URL in the email looks like 'www.mydomain.com/index.php?item?34' with a rectangle instead of '=12'. I am sure there is an easy way to fix this? Thanks in advance, Maenny

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• How to convert a MSSQL database (including procedures, functions and triggers) to a firebird databas

  - by user193655

  I am considering migrating to Firebird. To have a "quick start" approach I downloaded the trial of a conversion tool (DBConvert) and tried it. I just picked up a random tool, this tool doesn't convert procedures, functions and triggers (I don't think it is a limit of the trial since there is not an explicit reference to sp, sf and triggers in the link above). Anyway by trying that tool I had the message: "The DB cannot be converted succesfully because some FK names are too long." This is because in some tables I have FK whose description is 32 chars. Is this a real firebird limit or it is possible to overcome it somehow (of course renaming the FK is an extreme option because it is extra work)? Anyway how to convert a MS SQL DB fully to FIREBIRD? Is there a valid tool? Did someone succed in a conversion of non trivial databases?

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• Spider a Website and Return URLs Only

  - by Rob Wilkerson

  I'm not quite sure how best to define/articulate this, but I'm looking for a way to pseudo-spider a website. The key is that I don't actually want the content, but rather a simple list of URIs. I can get reasonably close to this idea with Wget using the --spider option, but when piping that output through a grep, I can't seem to find the right magic to make it work: wget --spider --force-html -r -l1 http://somesite.com | grep 'Saving to:' The grep filter seems to have absolutely no affect on the wget output. Have I got something wrong or is there another tool I should try that's more geared towards providing this kind of limited result set? Thanks. UPDATE So I just found out offline that, by default, wget writes to stderr. I missed that in the man pages (in fact, I still haven't found it if it's in there). Once I piped the return to stdout, I got closer to what I need: wget --spider --force-html -r -l1 http://somesite.com 2>&1 | grep 'Saving to:' I'd still be interested in other/better means for doing this kind of thing, if any exist.

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• JavaScript on Android randomly stops working

  - by AndersWid

  Hi! I have an application that uses a WebView and a html-page with javascript functions. Randomly the JavaScript functions doesn't seem to be called. It works up to a random point (I have looked at this bug all day) can only be produced on hardware (HTC Legend) not on emulator. Basicly I'm using callback to javaScript whenever the user presses a button, these callbacks tell the html to redraw using javaScript functions. mHandler.post(new Runnable() { public void run() { mWebView.loadUrl("javascript:getDataLine()"); } }); The first line in this javaScript code is an alert that says that it has started, so that I can see that it's working. Settings alerts or console.log's everywhere won't help as it seems the problem is in the webview or in Android itself. I need a way to see what's going on in the background. Maybe see if a previous call failed and stalled the thread or something.

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• Optimal Sharing of heavy computation job using Snow and/or multicore

  - by James

  Hi, I have the following problem. First my environment, I have two 24-CPU servers to work with and one big job (resampling a large dataset) to share among them. I've setup multicore and (a socket) Snow cluster on each. As a high-level interface I'm using foreach. What is the optimal sharing of the job? Should I setup a Snow cluster using CPUs from both machines and split the job that way (i.e. use doSNOW for the foreach loop). Or should I use the two servers separately and use multicore on each server (i.e. split the job in two chunks, run them on each server and then stich it back together). Basically what is an easy way to: 1. Keep communication between servers down (since this is probably the slowest bit). 2. Ensure that the random numbers generated in the servers are not highly correlated.

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• What is the advantage of using static methods in Python?

  - by Curious2learn

  I ran into unbound method error in python with the code class Sample(object): '''This class defines various methods related to the sample''' def drawSample(samplesize,List): sample=random.sample(List,samplesize) return sample Choices=range(100) print Sample.drawSample(5,Choices) After reading many helpful posts here, I figured how I could add @staticmethod above to get the code working. I am python newbie. Can someone please explain why one would want to define static methods? Or, why are not all methods defined as static methods. Thanks in advance.

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• Why does this give a segmentation fault?

  - by nightcracker

  I'm stunned, why does this code give me a segmentation fault? #include <stdio.h> #define LIMIT 1500000 typedef struct { int p; int a; int b; } triplet; int main(int argc, char **argv) { int i; triplet triplets[LIMIT]; for (i = 0; i < 5; i++) { triplets[i].p = 9; // remove this line and everything works fine } printf("%d\n", triplets[15].p); return 0; } EDIT: After changing LIMIT to 150 I no longer get a segmentation fault, it prints random numbers instead.

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• Php is stripping one letter "g" from my rtrim function but not other chars

  - by Chase

  I'm trying to trim some youtube URLs that I am reading in from a playlist. The first 3 work fine and all their URLs either end in caps or numbers but this one that ends in a lower case g is getting trimmed one character shorter than the rest. for ($z=0; $z <= 3; $z++) { $ythref2 = rtrim($tubeArray["feed"]["entry"][$z]["link"][0]["href"], '&feature=youtube_gdata'); The URL is http://www.youtube.com/watch?v=CuE88oVCVjg&feature=youtube_gdata .. and it should get trimmed down to .. http://www.youtube.com/watch?v=CuE88oVCVjg but instead it is coming out as http://www.youtube.com/watch?v=CuE88oVCVj. I think it may be the ampersand symbol but I am not sure.

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• Regex gurus! here's a teaser: mixed thousands separators and csv's

  - by chichilatte

  I've got a string like... "labour 18909, liberals 12,365,conservatives 14,720" ...and i'd like a regex which can get rid of any thousands separators so i can pull out the numbers easily. Or even a regex which could give me a tidy array like: (labour => 18909, liberals => 12365, conservatives => 14720) Oh i wish i had the time to figure out regexes! Maybe i'll buy one as a toilet book, mmm.

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• Glib convert epoch time to string.

  - by PP

  I am using glibs functions to convert epoch time to string as follows. But each time it is giving me some random time. //Convert Time in string. GDate *date = g_date_new_julian(timestampsecs); gchar date_string[50]; g_date_strftime(date_string, 50, (const gchar*)"%a, %I:%M %p", (const GDate*)date); printf("Date String [%s]\n", date_string ); Why this might be happening? am i missing anything? Thanks, PP.

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• Html combo box to database record Id

  - by LanguaFlash

  I'm fairly sure there has to be a simple solution to my problem, but I am a new web developer and can't quite figure it out. On my page I have a combo box whose values are filled from my database. When the user submits the form, how to I go about converting those values back to the record numbers in the database? Up to now I have been just doing a sort of reversed lookup in my database to try to get the record's ID. This has quite a few obvious flaws and I am sure that there has to be a better way. I am used to MS Forms combo boxes where the record data and ID are never separated. But in the case of a web form, I have no way to do multiple columns in the combo box like I am used to. Thanks! Jeff

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• How do I modify this download function in Python?

  - by TIMEX

  Right now, it's iffy. Gzip, images, sometimes it doesn't work. How do I modify this download function so that it can work with anything? (Regardless of gzip or any header?) How do I automatically "Detect" if it's gzip? I don't want to always pass True/False, like I do right now. def download(source_url, g = False, correct_url = True): try: socket.setdefaulttimeout(10) agents = ['Mozilla/4.0 (compatible; MSIE 5.5; Windows NT 5.0)','Mozilla/4.0 (compatible; MSIE 7.0b; Windows NT 5.1)','Microsoft Internet Explorer/4.0b1 (Windows 95)','Opera/8.00 (Windows NT 5.1; U; en)'] ree = urllib2.Request(source_url) ree.add_header('User-Agent',random.choice(agents)) ree.add_header('Accept-encoding', 'gzip') opener = urllib2.build_opener() h = opener.open(ree).read() if g: compressedstream = StringIO(h) gzipper = gzip.GzipFile(fileobj=compressedstream) data = gzipper.read() return data else: return h except Exception, e: return ""

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• c99 goto past initialization

  - by R Samuel Klatchko

  While debugging a crash, I came across this issue in some code: int func() { char *p1 = malloc(...); if (p1 == NULL) goto err_exit; char *p2 = malloc(...); if (p2 == NULL) goto err_exit; ... err_exit: free(p2); free(p1); return -1; } The problem occurs when the first malloc fails. Because we jump across the initialization of p2, it contains random data and the call to free(p2) can crash. I would expect/hope that this would be treated the same way as in C++ where the compiler does not allow a goto to jump across an initialization. My question: is jumping across an initialization allowed by the standard or is this a bug in gcc's implementation of c99?

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• Subset generation by rules

  - by Sazug

  Let's say that we have a 5000 users in database. User row has sex column, place where he/she was born column and status (married or not married) column. How to generate a random subset (let's say 100 users) that would satisfy these conditions: 40% should be males and 60% - females 50% should be born in USA, 20% born in UK, 20% born in Canada, 10% in Australia 70% should be married and 30% not. These conditions are independent, that is we cannot do like this: (0.4 * 0.5 * 0.7) * 100 = 14 users that are males, born in USA and married (0.4 * 0.5 * 0.3) * 100 = 6 users that are males, born in USA and not married. Is there an algorithm to this generation?

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