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• Project Euler problem 214, How can i make it more efficient?

  - by Once

  I am becoming more and more addicted to the Project Euler problems. However since one week I am stuck with the #214. Here is a short version of the problem: PHI() is Euler's totient function, i.e. for any given integer n, PHI(n)=numbers of k<=n for which gcd(k,n)=1. We can iterate PHI() to create a chain. For example starting from 18: PHI(18)=6 = PHI(6)=2 = PHI(2)=1. So starting from 18 we get a chain of length 4 (18,6,2,1) The problem is to calculate the sum of all primes less than 40e6 which generate a chain of length 25. I built a function that calculates the chain length of any number and I tested it for small values: it works well and fast. sum of all primes<=20 which generate a chain of length 4: 12 sum of all primes<=1000 which generate a chain of length 10: 39383 Unfortunately my algorithm doesn't scale well. When I apply it to the problem, it takes several hours to calculate... so I stop it because the Project Euler problems must be solved in less than one minute. I thought that my prime detection function might be slow so I fed the program with a list of primes <40e6 to avoid the primality test... The code runs now a little bit faster, but there is still no way to get a solution in less than a few hours (and I don't want this). So is there any "magic trick" that I am missing here ? I really don't understand how to be more efficient on this one... I am not asking for the solution, because fighting with optimization is all the fun of Project Euler. However, any small hint that could put me on the right track would be welcome. Thanks !

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• How do you save and retrieve a Key/IV pair securely?

  - by Shawn Steward

  I'm using VB.Net's RijndaelManaged (RM) to encrypt files, using the RM.GenerateKey and RM.GenerateIV methods to generate the Key and IV and encrypting the file using the CryptoStream class. I'm planning on saving this Key and IV to a file and want to make sure I'm doing it the right way. I am combining the IV+Key, and encrypting that with my RSA Public key and writing it out to a file. Then, to decrypt I use the RSA Private key on this file to get the IV+Key, split them up and set RM.Key and RM.IV to these values and run the decryptor. Is this the best method to accomplish this, or is there a preferred method for saving the IV & Key? Also, what's the best way to construct and deconstruct the byte array? I used the .Concat method to join them together and that seems to work well but I can't seem to find something as easy to deconstruct it. I played with the .Take method that takes the first x # of bytes and it works for the first part but can't find anything that gets the rest of it.

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• How do I store a string longer than 4000 characters in an Oracle Database using Java/JDBC?

  - by Ventrue

  I’m not sure how to use Java/JDBC to insert a very long string into an Oracle database. I have a String which is greater than 4000 characters, lets say it’s 6000. I want to take this string and store it in an Oracle database. The way to do this seems to be with the CLOB datatype. Okay, so I declared the column as description CLOB. Now, when it comes time to actually insert the data, I have a prepared statement pstmt. It looks like pstmt = conn.prepareStatement(“INSERT INTO Table VALUES(?)”). So I want to use the method pstmt.setClob(). However, I don’t know how to create a Clob object with my String in it; there’s no constructor (presumably because it can be potentially much larger than available memory). How do I put my String into a Clob? Keep in mind I’m not a very experienced programmer; please try to keep the explanations as simple as possible. Efficiency, good practices, etc. are not a concern here, I just want the absolute easiest solution. I’d like to avoid downloading other packages if it all possible; right now I’m just using JDK 1.4 and what is labelled “ojdbc14.jar”. I've looked around a bit but I haven't been able to follow any of the explanations I've found. If you have a solution that doesn’t use Clobs, I’d be open to that as well, but it has to be one column.

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• Does this language feature already exists?

  - by Pindatjuh

  I'm currently developing a new language for programming in a continuous environment (compare it to electrical engineering), and I've got some ideas on a certain language construction. Let me explain the feature by explanation and then by definition; x = a | b; Where x is a variable and a and b are other variables (or static values). if(x == a) { // all references to "x" are essentially references to "a". } if(x == b) { // same but with "b" } if(x != a) { // ... } if(x == a | b) { // guaranteed that "x" is '"a" | "b"'; interacting with "x" // will interact with both "a" and "b". } // etc. In the above, all code-blocks are executed, but the "scope" changes in each block how x is interpreted. In the first block, x is guaranteed to be a: thus interacting with x inside that block will interact on a. The second and the third code-block are only equal in this situation (because not b only remains a). The last block guarantees that x is at least a or b. Further more; | is not the "bitwise or operator", but I've called it the "and/or"-operator. It's definition is: "|" = "and" | "or" (On my blog, http://cplang.wordpress.com/2009/12/19/binop-and-or/, is more (mathematical) background information on this operator. It's loosely based on sets.) I do not know if this construction already exists, so that's my question: does this language feature already exists?

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• Understanding many to many relationships and Entity Framework

  - by Anders Svensson

  I'm trying to understand the Entity Framework, and I have a table "Users" and a table "Pages". These are related in a many-to-many relationship with a junction table "UserPages". First of all I'd like to know if I'm designing this relationship correctly using many-to-many: One user can visit multiple pages, and each page can be visited by multiple users..., so am I right in using many2many? Secondly, and more importantly, as I have understood m2m relationships, the User and Page tables should not repeat information. I.e. there should be only one record for each user and each page. But then in the entity framework, how am I able to add new visits to the same page for the same user? That is, I was thinking I could simply use the Count() method on the IEnumerable returned by a LINQ query to get the number of times a user has visited a certain page. But I see no way of doing that. In Linq to Sql I could access the junction table and add records there to reflect added visits to a certain page by a certain user, as many times as necessary. But in the EF I can't access the junction table. I can only go from User to a Pages collection and vice versa. I'm sure I'm misunderstanding relationships or something, but I just can't figure out how to model this. I could always have a Count column in the Page table, but as far as I have understood you're not supposed to design database tables like that, those values should be collected by queries... Please help me understand what I'm doing wrong...

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• Rails - eager load the number of associated records, but not the record themselves.

  - by Max Williams

  I have a page that's taking ages to render out. Half of the time (3 seconds) is spent on a .find call which has a bunch of eager-loaded associations. All i actually need is the number of associated records in each case, to display in a table: i don't need the actual records themselves. Is there a way to just eager load the count? Here's a simplified example: @subjects = Subject.find(:all, :include => [:questions]) In my table, for each row (ie each subject) i just show the values of the subject fields and the number of associated questions for each subject. Can i optimise the above find call to suit these requirements? I thought about using a group field but my full call has a few different associations included, with some second-order associations, so i don't think group by will work. @subjects = Subject.find(:all, :include => [{:questions => :tags}, {:quizzes => :tags}], :order => "subjects.name") :tags in this case is a second-order association, via taggings. Here's my associations in case it's not clear what's going on. Subject has_many :questions has_many :quizzes Question belongs_to :subject has_many :taggings has_many :tags, :through => :taggings Quiz belongs_to :subject has_many :taggings has_many :tags, :through => :taggings Grateful for any advice - max

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• Compiling Objective-C project on Linux (Ubuntu)

  - by Alex

  How to make an Objective-C project work on Ubuntu? My files are: Fraction.h #import <Foundation/NSObject.h> @interface Fraction: NSObject { int numerator; int denominator; } -(void) print; -(void) setNumerator: (int) n; -(void) setDenominator: (int) d; -(int) numerator; -(int) denominator; @end Fraction.m #import "Fraction.h" #import <stdio.h> @implementation Fraction -(void) print { printf( "%i/%i", numerator, denominator ); } -(void) setNumerator: (int) n { numerator = n; } -(void) setDenominator: (int) d { denominator = d; } -(int) denominator { return denominator; } -(int) numerator { return numerator; } @end main.m #import <stdio.h> #import "Fraction.h" int main( int argc, const char *argv[] ) { // create a new instance Fraction *frac = [[Fraction alloc] init]; // set the values [frac setNumerator: 1]; [frac setDenominator: 3]; // print it printf( "The fraction is: " ); [frac print]; printf( "\n" ); // free memory [frac release]; return 0; } I've tried two approaches to compile it: Pure gcc: $ sudo apt-get install gobjc gnustep gnustep-devel $ gcc `gnustep-config --objc-flags` -o main main.m -lobjc -lgnustep-base /tmp/ccIQKhfH.o:(.data.rel+0x0): undefined reference to `__objc_class_name_Fraction' I created a GNUmakefile Makefile: include ${GNUSTEP_MAKEFILES}/common.make TOOL_NAME = main main_OBJC_FILES = main.m include ${GNUSTEP_MAKEFILES}/tool.make ... and ran: $ source /usr/share/GNUstep/Makefiles/GNUstep.sh $ make Making all for tool main... Linking tool main ... ./obj/main.o:(.data.rel+0x0): undefined reference to `__objc_class_name_Fraction' So in both cases compiler gets stuck at undefined reference to `__objc_class_name_Fraction' Do you have and idea how to resolve this issue?

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• Resolve php endless recursion issue

  - by Matt

  Hey all, I'm currently running into an endless recursion situation. I'm implementing a message service that calls various object methods.. it's quite similar to observer pattern.. Here's whats going on: Dispatcher.php class Dispatcher { ... public function message($name, $method) { // Find the object based on the name $object = $this->findObjectByName($name); // Slight psuedocode.. for ease of example if($this->not_initialized($object)) $object = new $object(); // This is where it locks up. } return $object->$method(); ... } class A { function __construct() { $Dispatcher->message("B", "getName"); } public function getName() { return "Class A"; } } class B { function __construct() { // Assume $Dispatcher is the classes $Dispatcher->message("A", "getName"); } public function getName() { return "Class B"; } } It locks up when neither object is initialized. It just goes back and forth from message each other and no one can be initialized. I'm looking for some kind of queue implementation that will make messages wait for each other.. One where the return values still get set. I'm looking to have as little boilerplate code in class A and class B as possible Any help would be immensely helpful.. Thanks! Matt Mueller

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• Have no idea with python-excel read data file

  - by Protoss Reed

  I am a student and haven't a big expirence to do this work. So problem is next. I have a part of code: import matplotlib.pyplot as plt from pylab import * import cmath def sf(prompt): """ """ error_message = "Value must be integer and greater or equal than zero" while True: val = raw_input(prompt) try: val = float(val) except ValueError: print(error_message) continue if val <= 0: print(error_message) continue return val def petrogen_elements(): """Input and calculations the main parameters for pertogen elements""" print "Please enter Petrogen elements: \r" SiO2 = sf("SiO2: ") Al2O3= sf("Al2O3: ") Na2O = sf("Na2O: ") K2O = sf("K2O: ") petro = [SiO2,TiO2,Al2O3,] Sum = sum(petro) Alcal = Na2O + K2O TypeA lcal= Na2O / K2O Ka= (Na2O + K2O)/ Al2O3 print '-'*20, "\r Alcal: %s \r TypeAlcal: %s \ \r Ka: %s \r" % (Alcal, TypeAlcal,Ka,) petrogen_elements() So the problem is next. I have to load and read excel file and read all data in it. After that program have to calculate for example Alcaline, Type of Alcaline etc. Excel file has only this structure 1 2 3 4 5   1 name1 SiO2 Al2O3 Na2O K2O 2 32 12 0.21 0.1 3 name2 SiO2 Al2O3 Na2O K2O 4 45 8 7.54 5 5 name3 SiO2 Al2O3 Na2O K2O 6. … …. …. … … … All excel file has only 5 columns and unlimited rows. User has choice input data or import excel file. First part of work I have done but it stays a big part Finally I need to read all file and calculate the values. I would be so grateful for some advice

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• How do I bring forward the SELECTED option in PHP from MySQL?

  - by Derek

  Hi all, In my update form, I want the fields to recall the values that are already stored. This is very simple in a text field, but for my drop down () I'm having trouble with PHP reading the already stored name of user. Here is my query and code: $sql = "SELECT users.user_id, users.name FROM users"; $result = mysql_query($sql, $connection) or die ("Couldn't perform query $sql <br />".mysql_error()); $row = mysql_fetch_array($result);?> <label>Designated Person:</label> <select name="name" id="name"> <option value="<?php echo $row['user_id']?>" SELECTED><?php echo $row['name']?> - Current</option> <?php while($row = mysql_fetch_array($result)) { ?> <option value="<?php echo $row['user_id']; if (isset($_POST['user_id']));?>"><?php echo $row['fullname']?></option> <?php } ?> The result of this displays all of the users (as required) and lets me select a user then perform the change successfully...however the 'SELECTED' is always the first one in my database and never the user that was selected when my activity was added :( !!!

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• Using XPath on String in Android (JAVA)

  - by Rav

  I am looking for some examples of using xpath in Android? Or if anyone can share their experiences. I have been struggeling to make tail or head of this problem :-( I have a string that contains a standard xml file. I believe I need to convert that into an xml document. I have found this code which I think will do the trick: public static Document stringToDom(String xmlSource) throws SAXException, ParserConfigurationException, IOException { DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder builder = factory.newDocumentBuilder(); return builder.parse(new InputSource(new StringReader(xmlSource))); } Next steps Assuming the code above is OK, I need to apply xpath to get values from cat: "/animal/mammal/feline/cat" I look at the dev doc here: http://developer.android.com/reference/javax/xml/xpath/XPath.html and also look online, but I am not sure where to start! I have tried to use the following code: XPathFactory xPathFactory = XPathFactory.newInstance(); // To get an instance of the XPathFactory object itself. XPath xPath = xPathFactory.newXPath(); // Create an instance of XPath from the factory class. String expression = "SomeXPathExpression"; XPathExpression xPathExpression = xPath.compile(expression); // Compile the expression to get a XPathExpression object. Object result = xPathExpression.evaluate(xmlDocument); // Evaluate the expression against the XML Document to get the result. But I get "Cannot be resolved". Eclipse doesn't seem to be able to fix this import. I tried manually entering: javax.xml.xpath.XPath But this did not work. Does anyone know any good source code that I can utilise, for Android platform? 1.5

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• How to define multiple elements in XML Schema with the same name and different attribute value allow

  - by David Skyba

  I would like to create XML Schema for this chunk of xml, I would like to restrict the values of "name" attribute, so that in output document on and only one instance of day is allowed for each week day: <a> <day name="monday" /> <day name="tuesday" /> <day name="wednesday" /> </a> I have tried to use this: <xs:complexType name="a"> <xs:sequence> <xs:element name="day" minOccurs="1" maxOccurs="1"> <xs:complexType> <xs:attribute name="name" use="required"> <xs:simpleType> <xs:restriction base="xs:string"> <xs:enumeration value="monday" /> </xs:restriction> </xs:simpleType> </xs:attribute> </xs:complexType> </xs:element> <xs:element name="day" minOccurs="1" maxOccurs="1"> <xs:complexType> <xs:attribute name="name" use="required"> <xs:simpleType> <xs:restriction base="xs:string"> <xs:enumeration value="tuesday" /> </xs:restriction> </xs:simpleType> </xs:attribute> </xs:complexType> </xs:element> </xs:sequence> </xs:complexType> but XML Schema validator in eclipse says error "Multiple elements with name 'day', with different types, appear in the model group.". Is there any other way?

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• How to get MySQL database to appear on index.php

  - by Teddy Truong

  Hi, I have a submission form on my website (index.php) and I have the data(user submissions) being stored into a MySQL database. Right now, I have the user submitting a post and then the page directs them to an update.php which shows what they inputed. However, I want all of the data in the database in MySQL to be shown on the index.php. It's a lot like a comment system. User submits a post... and sees their post above the other submitted posts all on the same page. I think I'm missing AJAX... ? Here is the code for index.php <div align="center"> <p>&nbsp;</p> <h2 align="center" class="Title"><em><strong>REDACTED</strong></em></h2> <form id="form1" name="form1" method="post" action="update.php"> <hr /> <label><br /> <form action="update.php" method="post"> REDACTED: <input type="text" name="text" /> <input type="submit" /> </form> </label> </form> </div> On update.php I have this: ?php $text = $_POST['text']; $myString = "REDACTED"; mysql_connect ("db----.net", "-----3", "------------") or die ('Error: ' . mysql_error()); mysql_select_db ("-----------"); $query="INSERT INTO TextArea (ID, text) VALUES ('NULL', '".$text."')"; mysql_query($query) or die ('Error updating database'); echo " $myString "," $text "; ?> Thanks a lot!

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• LINQ Join on Dictionary<K,T> where only K is changed.

  - by Stacey

  Assuming type TModel, TKey, and TValue. In a dictionary where KeyValuePair is declared, I need to merge TKey into a separate model of KeyValuePair where TKey in the original dictionary refers to an identifier in a list of TModel that will replace the item in the Dictionary. public TModel { public Guid Id { get; set; } // ... } public Dictionary<Guid, TValue> contains the elements. TValue relates to the TModel. The serialized/stored object is like this.. public SerializedModel { public Dictionary<Guid,TValue> Items { get; set; } } So I need to construct a new model... KeyValueModel { public Dictionary<TModel, TValue> { get; set; } } KeyValueModel kvm = = (from tModels in controller.ModelRepository.List<Models.Models>() join matchingModels in storedInformation.Items on tModels.Id equals matchingModels select tModels).ToDictionary( c => c.Id, storedInformation.Items.Values ) This linq query isn't doing what I'm wanting, but I think I'm at least headed in the right direction. Can anyone assist with the query? The original object is stored as a KeyValuePair. I need to merge the Guid Keys in the Dictionary to their actual related objects in another object (List) so that the final result is KeyValuePair. And as for what the query is not doing for me... it isn't compiling or running. It just says that "Join is not valid".

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• Choose a XML node in SQL Server based on max value of a child element

  - by Jay

  I am trying to select from SQL Server 2005 XML datatype some values based on the max data that is located in a child node. I have multiple rows with XML similar to the following stored in a field in SQL Server: <user> <name>Joe</name> <token> <id>ABC123</id> <endDate>2013-06-16 18:48:50.111</endDate> </token> <token> <id>XYX456</id> <endDate>2014-01-01 18:48:50.111</endDate> </token> </user> I want to perform a select from this XML column where it determines the max date within the token element and would return the datarows similar to the result below for each record: Joe XYZ456 2014-01-01 18:48:50.111 I have tried to find a max function for xpath that would all me to select the correct token element but I couldn't find one that would work. I also tried to use the SQL MAX function but I wasn't able to get it working with that method either. If I only have a single token it of course works fine but when I have more than one I get a NULL, most likely because the query doesn't know which date to pull. I was hoping there would be a way to specify a where clause [max(endDate)] on the token element but haven't found a way to do that. Here is an example of the one that works when I only have a single token: SELECT XMLCOL.query('user/name').value('.','NVARCHAR(20)') as name XMLCOL.query('user/token/id').value('.','NVARCHAR(20)') as id XMLCOL.query('user/token/endDate').value(,'xs:datetime(.)','DATETIME') as endDate FROM MYTABLE

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• PHP error problem.

  - by TaG

  I get the following error on line 8: Undefined index: real_name which is $privacy_policy = mysqli_real_escape_string($mysqli, $_POST['privacy_policy']); I was wondering how can I fix this problem? Here is the PHP. if (isset($_POST['submitted'])) { $mysqli = mysqli_connect("localhost", "root", "", "sitename"); $dbc = mysqli_query($mysqli,"SELECT users.* FROM users WHERE user_id=3"); $privacy_policy = mysqli_real_escape_string($mysqli, $_POST['privacy_policy']); if (mysqli_num_rows($dbc) == 0) { $mysqli = mysqli_connect("localhost", "root", "", "sitename"); $dbc = mysqli_query($mysqli,"INSERT INTO users (user_id, privacy_policy) VALUES ('$user_id', '$privacy_policy')"); } if ($dbc == TRUE) { $dbc = mysqli_query($mysqli,"UPDATE users SET privacy_policy = '$privacy_policy' WHERE user_id = '$user_id'"); echo '<p class="changes-saved">Your changes have been saved!</p>'; } if (!$dbc) { print mysqli_error($mysqli); return; } } Here is the HTML. <form method="post" action="index.php"> <fieldset> <ul> <li><input type="checkbox" name="privacy_policy" id="privacy_policy" value="yes" <?php if (isset($_POST['privacy_policy'])) { echo 'checked="checked"'; } else if($privacy_policy == "yes") { echo 'checked="checked"'; } ?> /></li> <li><input type="submit" name="submit" value="Save Changes" class="save-button" /> <input type="hidden" name="submitted" value="true" /> <input type="submit" name="submit" value="Preview Changes" class="preview-changes-button" /></li> </ul> </fieldset> </form>

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• what are all the Optimize tricks that you know for asp.net code ?

  - by Aristos

  After some time of many code programming on asp.net, I discover the very big speed different between string and StringBuilder. I know that is very common and known but I just mention it for start. The second think that I have found to speed up the code, is to use the const, and not the static, for declare my configuration constants value (especial the strings). With the const, the compiler not create new object, but just place the value, on the point that you have ask it, but with the static declaration, is create a new memory object and keep its on the memory. My third trick, is when I search for string, I use hash values, and not the string itself. For example, if I need a List<string SomeValues, and place inside strings that I need to search them, I prefer to use List<int SomeHashValue, and I use the hash value to locate the strings. My forth thought that I was wandering, is if is better to place big strings in one line, or separate them in different lines with the + symbol to be more easy to read out. I make some tests and see that the compiler make a good job is some split the string, in many lines, using the + symbol. What other tricks/tips do you know and use on your programming to make it run faster, and maybe use less memory. Well I know, that some times, to make something run faster, you need more memory, more cache. My priority is on speed. Because Speed Counts.

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• Trouble when changing pixel data with alpha on png on iphone --okay on simulator

  - by Ted

  I'm trying to change the color of the pixels (lighten or darken) without changing the value of the alpha channel using CGDataProviderCopyData. I leave every 4th databyte untouched. It work fine of the iphone simulator, however on the real thing the alpha goes white as I increase the values of the other pixels. I've tried changing just the first byte, or the second, or the third. Does anybody have any idea what is going on? The basic code is borrowed from Jorge. I like this simple approach --I'm new to this. But I want to make it work with png images with some transparency. here is most of the code by Jorge : CFDataRef CopyImagePixels(CGImageRef inImage){ return CGDataProviderCopyData(CGImageGetDataProvider(inImage)); } CGImageRef img=originalImage.CGImage; CFDataRef dataref=CopyImagePixels(img); UInt8 *data=(UInt8 *)CFDataGetBytePtr(dataref); int length=CFDataGetLength(dataref); for(int index=0;index255){ data[index+i]=255; }else{ data[index+i]+=value; } } } } size_t width=CGImageGetWidth(img); size_t height=CGImageGetHeight(img); size_t bitsPerComponent=CGImageGetBitsPerComponent(img); size_t bitsPerPixel=CGImageGetBitsPerPixel(img); size_t bytesPerRow=CGImageGetBytesPerRow(img); CGColorSpaceRef colorspace=CGImageGetColorSpace(img); CGBitmapInfo bitmapInfo=CGImageGetBitmapInfo(img); CGImageAlphaInfo alphaInfo = kCGBitmapAlphaInfoMask(img); NSLog(@"bitmapinfo: %d",bitmapInfo); CFDataRef newData=CFDataCreate(NULL,data,length); CGDataProviderRef provider=CGDataProviderCreateWithCFData(newData); CGImageRef newImg=CGImageCreate(width,height,bitsPerComponent,bitsPerPixel,bytesPerRow,colorspace,bitmapInfo,provider,NULL,true,kCGRenderingIntentDefault); [iv setImage:[UIImage imageWithCGImage:newImg]]; CGImageRelease(newImg); CGDataProviderRelease(provider);

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• ASP.NET, C#: timeout when trying to Transaction.Commit() to database; potential deadlock?

  - by user1843921

  I have a web page that has coding structured somewhat as follows: SqlConnection conX =new SqlConnection(blablabla); conX.Open(); SqlTransaction tran=conX.BeginTransaction(); try{ SqlCommand cmdInsert =new SqlCommand("INSERT INTO Table1(ColX,ColY) VALUES @x,@y",conX); cmdInsert.Transaction=tran; cmdInsert.ExecuteNonQuery(); SqlCommand cmdSelect=new SqlCOmmand("SELECT * FROM Table1",conX); cmdSelect.Transaction=tran; SqlDataReader dtr=cmdSelect.ExecuteReader(); //read stuff from dtr dtr.Close(); cmdInsert=new SqlCommand("UPDATE Table2 set ColA=@a",conX); cmdInsert.Transaction=tran; cmdInsert.ExecuteNonQuery(); //display MiscMessage tran.Commit(); //display SuccessMessage } catch(Exception x) { tran.Rollback(); //display x.Message } finally { conX.Close(); } So, everything seems to work until MiscMessage. Then, after a while (maybe 15-ish seconds?) x.Message pops up, saying that: "Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding." So something wrong with my trans.Commit()? The database is not updated so I assume the trans.Rollback works... I have read that deadlocks can cause timeouts...is this problem cause by my SELECT statement selecting from Table1, which is being used by the first INSERT statement? If so, what should I do? If that ain't the problem, what is?

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• MySQL: Get average of time differences?

  - by Nebs

  I have a table called Sessions with two datetime columns: start and end. For each day (YYYY-MM-DD) there can be many different start and end times (HH:ii:ss). I need to find a daily average of all the differences between these start and end times. An example of a few rows would be: start: 2010-04-10 12:30:00 end: 2010-04-10 12:30:50 start: 2010-04-10 13:20:00 end: 2010-04-10 13:21:00 start: 2010-04-10 14:10:00 end: 2010-04-10 14:15:00 start: 2010-04-10 15:45:00 end: 2010-04-10 15:45:05 start: 2010-05-10 09:12:00 end: 2010-05-10 09:13:12 ... The time differences (in seconds) for 2010-04-10 would be: 50 60 300 5 The average for 2010-04-10 would be 103.75 seconds. I would like my query to return something like: day: 2010-04-10 ave: 103.75 day: 2010-05-10 ave: 72 ... I can get the time difference grouped by start date but I'm not sure how to get the average. I tried using the AVG function but I think it only works directly on column values (rather than the result of another aggregate function). This is what I have: SELECT TIME_TO_SEC(TIMEDIFF(end,start)) AS timediff FROM Sessions GROUP BY DATE(start) Is there a way to get the average of timediff for each start date group? I'm new to aggregate functions so maybe I'm misunderstanding something. If you know of an alternate solution please share. I could always do it ad hoc and compute the average manually in PHP but I'm wondering if there's a way to do it in MySQL so I can avoid running a bunch of loops. Thanks.

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• Parse usable Street Address, City, State, Zip from a string

  - by Rob Allen

  Problem: I have an address field from an Access database which has been converted to Sql Server 2005. This field has everything all in one field. I need to parse out the individual sections of the address into their appropriate fields in a normalized table. I need to do this for approximately 4,000 records and it needs to be repeatable. Here are the rules for this exercise: 1 - no whining about how this should have been separate fields in the first place, we are often confronted with less than ideal situations and have to make the best of them 2- for this post, use any language you want 3- feel free to play code golf 4 - Assume an address in the US (for now) 5 - assume that the input string will sometimes contain an addressee (the person being addressed) and/or a second street address (i.e. Suite B) 6 - states may be abbreviated 7 - zip code could be standard 5 digit or zip+4 8 - there are typos in some instances UPDATE: In response to the questions posed, standards were not universally followed, I need need to store the individual values, not just geocode and errors means typo (corrected above) Sample Data: A. P. Croll & Son 2299 Lewes-Georgetown Hwy, Georgetown, DE 19947 11522 Shawnee Road, Greenwood DE 19950 144 Kings Highway, S.W. Dover, DE 19901 Intergrated Const. Services 2 Penns Way Suite 405 New Castle, DE 19720 Humes Realty 33 Bridle Ridge Court, Lewes, DE 19958 Nichols Excavation 2742 Pulaski Hwy Newark, DE 19711 2284 Bryn Zion Road, Smyrna, DE 19904 VEI Dover Crossroads, LLC 1500 Serpentine Road, Suite 100 Baltimore MD 21 580 North Dupont Highway Dover, DE 19901 P.O. Box 778 Dover, DE 19903

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• Select all points in a matrix within 30m of another point

  - by pinnacler

  So if you look at my other posts, it's no surprise I'm building a robot that can collect data in a forest, and stick it on a map. We have algorithms that can detect tree centers and trunk diameters and can stick them on a cartesian XY plane. We're planning to use certain 'key' trees as natural landmarks for localizing the robot, using triangulation and trilateration among other methods, but programming this and keeping data straight and efficient is getting difficult using just Matlab. Is there a technique for sub-setting an array or matrix of points? Say I have 1000 trees stored over 1km (1000m), is there a way to say, select only points within 30m radius of my current location and work only with those? I would just use a GIS, but I'm doing this in Matlab and I'm unaware of any GIS plugins for Matlab. I forgot to mention, this code is going online, meaning it's going on a robot for real-time execution. I don't know if, as the map grows to several miles, using a different data structure will help or if calculating every distance to a random point is what a spatial database is going to do anyway. I'm thinking of mirroring two arrays, one sorted by X and the other by Y. Then bubble sorting to determine the 30m range in that. I do the same for both arrays, X and Y, and then have a third cross link table that will select the individual values. But I don't know, what that's called, how to program that and I'm sure someone already has so I don't want to reinvent the wheel. Cartesian Plane GIS

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• GWT Animation final value is not respected

  - by brad

  I have a FlowPanel that I'm trying to animate back and forth like an iphone nav. (See this post for my original question on how to do this) So I have it "working" with the code shown below. I say working in quotes because I'm finding that my final position of my scroller is not precise and always changes when scrolling. The GWT.log always says the actual values I'm looking for, so for instance with the call below to scrollTo, my GWT.log says: ScrollStart: 0 scrollStop: -246 But when I actually analyze the element in fireBug, its css, left position is never exactly -246px. Sometimes it's off by as much as 10px so my panel has just stopped scrolling before being finished. The worst part is that this nav animates back and forth, so subsequent clicks can really throw it off, and I need pixel perfect positioning otherwise the whole things looks off. I don't even know where to start with debugging this other than what I've already done. Any tips are appreciated. Code to call animation scroller = new Scroller(); scroller.scrollTo(-246,400); Animation Code public class Scroller extends Animation { private FlowPanel scroller; private final Element e; public Scroller(){ scroller = new FlowPanel(); e = scroller.getElement(); } public void scrollTo(int position, int milliseconds) { scrollStart = e.getOffsetLeft(); scrollStop = position; GWT.log("ScrollStart: " + scrollStart + " scrollStop: " + scrollStop); run(milliseconds); } @Override protected void onUpdate(double progress) { double position = scrollStart + (progress * (scrollStop - scrollStart)); e.getStyle().setLeft(position, Style.Unit.PX); } }

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• Eclipse Java Content Assist not working

  - by Damo

  The Content Assist in Eclipse 3.4 and 3.5 has stopped working for me. When I type in the first few characters of a class and hit CRTL-space then after a delay I get the following error message It does not matter what proposals I enable/disable, I will get this (or similar) message. I have tried: Changing the Xms/Xmx values Starting Eclipse with -clean Creating a new workspace and importing my projects However none of these have worked. I have seen some posts suggesting that other apps may be taking over the CRTL-space or otherwise interfering, however I have nothing aside from a fresh Eclipse running and the problem persists. My problem is very similar to the one covered in this post albeit on a later version and on OSX 10.5.7. Does anyone have any suggestions for how this might be resolved? Thanks. UPDATE: To anyone interested I've had the best results by using Eclipse 3.5 Classic (ie. doesn't include Mylyn). I've also used the settings specified in the bug reports linked to by VonC below. Interestingly Classic doesn't come with some views eg. Snippets, but these are easy to drop in from another distro. UPDATE 2: This problem actually persisted even with the latest versions of Eclipse (3.6 M1). It is caused by a large JAR file generated my Altova Mapforce to handle EDIFACT transformations in our application. It is reproducible by adding this JAR to the buildpath and no changes to Content Assist settings help. The bug (and JAR) can be seen at https://bugs.eclipse.org/bugs/show_bug.cgi?id=289057

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• Hadoop/MapReduce: Reading and writing classes generated from DDL

  - by Dave

  Hi, Can someone walk me though the basic work-flow of reading and writing data with classes generated from DDL? I have defined some struct-like records using DDL. For example: class Customer { ustring FirstName; ustring LastName; ustring CardNo; long LastPurchase; } I've compiled this to get a Customer class and included it into my project. I can easily see how to use this as input and output for mappers and reducers (the generated class implements Writable), but not how to read and write it to file. The JavaDoc for the org.apache.hadoop.record package talks about serializing these records in Binary, CSV or XML format. How do I actually do that? Say my reducer produces IntWritable keys and Customer values. What OutputFormat do I use to write the result in CSV format? What InputFormat would I use to read the resulting files in later, if I wanted to perform analysis over them?

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