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  • HTML / PHP from

    - by user317128
    I am trying to code an all in one HTML/PHP contact from with error checking. When I load this file in my browser there is not HTML. I am a newb php programmer so most likely forgot something pretty obvious. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>All In One Feedback Form</title> </head> <body> <? $form_block = " <input type=\"hidden\" name=\"op\" value=\"ds\"> <form method=\"post\" action=\"$server[PHP_SELF]\"> <p>Your name<br /> <input name=\"sender_name\" type=\"text\" size=30 value=\"$_POST[sender_name]\" /></p> <p>Email<br /> <input name=\"sender_email\" type=\"text\" size=30 value=\"$_POST[sender_email]\"/></p> <p>Message<br /> <textarea name=\"message\" cols=30 rows=5 value=\"$_POST[message]\"></textarea></p> <input name=\"submit\" type=\"submit\" value=\"Send This Form\" /> </form>"; if ($_POST[op] != "ds") { //they see this form echo "$form_block"; } else if ($_POST[op] == "ds") { if ($_POST[sender_name] == "") { $name_err = "Please enter your name<br>"; $send = "no"; } if ($_POST[sender_email] == "ds") { $email_err = "Please enter your email<br>"; $send = "no"; } if ($_POST[message] == "ds") { $message_err = "please enter message<br>"; $send = "no"; } if ($send != "no") { //its ok to send $to = "[email protected]"; $subject = "All in one web site feed back"; $mailheaders = "From: website <some email [email protected]> \n"; $mailheaders .= "Reply-To: $_POST[sender_email]\n"; $msg = "Email sent from this site www.ccccc.com\n"; $msg .= "Senders name: $_POST[senders_name]\n"; $msg .= "Sender's E-Mail: $_POST[sender_email]\n"; $msg .= "Message: $_POST[message]\n\n"; mail($to, $subject, $msg, $mailheaders); echo "<p>Mail has been sent</p>"; } else if ($send == "no") { echo "$name_err"; echo "$email_err"; echo "$message_err"; echo "$form_block"; } } ?> </body> </html> FYI I am trying the example from a book named PHP 6 Fast and Easy Wed Development

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  • Find optimal strategy and AI for the game 'Proximity'?

    - by smci
    'Proximity' is a strategy game of territorial domination similar to Othello, Go and Risk. Two players, uses a 10x12 hex grid. Game invented by Brian Cable in 2007. Seems to be a worthy game for discussing a) optimal algorithm then b) how to build an AI. Strategies are going to be probabilistic or heuristic-based, due to the randomness factor, and the insane branching factor (20^120). So it will be kind of hard to compare objectively. A compute time limit of 5s per turn seems reasonable. Game: Flash version here and many copies elsewhere on the web Rules: here Object: to have control of the most armies after all tiles have been placed. Each turn you received a randomly numbered tile (value between 1 and 20 armies) to place on any vacant board space. If this tile is adjacent to any ally tiles, it will strengthen each tile's defenses +1 (up to a max value of 20). If it is adjacent to any enemy tiles, it will take control over them if its number is higher than the number on the enemy tile. Thoughts on strategy: Here are some initial thoughts; setting the computer AI to Expert will probably teach a lot: minimizing your perimeter seems to be a good strategy, to prevent flips and minimize worst-case damage like in Go, leaving holes inside your formation is lethal, only more so with the hex grid because you can lose armies on up to 6 squares in one move low-numbered tiles are a liability, so place them away from your main territory, near the board edges and scattered. You can also use low-numbered tiles to plug holes in your formation, or make small gains along the perimeter which the opponent will not tend to bother attacking. a triangle formation of three pieces is strong since they mutually reinforce, and also reduce the perimeter Each tile can be flipped at most 6 times, i.e. when its neighbor tiles are occupied. Control of a formation can flow back and forth. Sometimes you lose part of a formation and plug any holes to render that part of the board 'dead' and lock in your territory/ prevent further losses. Low-numbered tiles are obvious-but-low-valued liabilities, but high-numbered tiles can be bigger liabilities if they get flipped (which is harder). One lucky play with a 20-army tile can cause a swing of 200 (from +100 to -100 armies). So tile placement will have both offensive and defensive considerations. Comment 1,2,4 seem to resemble a minimax strategy where we minimize the maximum expected possible loss (modified by some probabilistic consideration of the value ß the opponent can get from 1..20 i.e. a structure which can only be flipped by a ß=20 tile is 'nearly impregnable'.) I'm not clear what the implications of comments 3,5,6 are for optimal strategy. Interested in comments from Go, Chess or Othello players. (The sequel ProximityHD for XBox Live, allows 4-player -cooperative or -competitive local multiplayer increases the branching factor since you now have 5 tiles in your hand at any given time, of which you can only play one. Reinforcement of ally tiles is increased to +2 per ally.)

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  • How to use JQuery to set the value of 2 html form select elements depending on the value of another

    - by Chris Stevenson
    My Javascript and JQuery skills are poor at best and this is ** I have the following three elements in a form : <select name="event_time_start_hours"> <option value="blank" disabled="disabled">Hours</option> <option value="blank" disabled="disabled">&nbsp;</option> <option value="01">1</option> <option value="02">2</option> <option value="03">3</option> <option value="04">4</option> <option value="05">5</option> <option value="06">6</option> <option value="07">7</option> <option value="08">8</option> <option value="09">9</option> <option value="10">10</option> <option value="11">11</option> <option value="12">12</option> <option value="midnight">Midnight</option> <option value="midday">Midday</option> </select> <select name="event_time_start_minutes"> <option value="blank" disabled="disabled">Minutes</option> <option value="blank" disabled="disabled">&nbsp;</option> <option value="00">00</option> <option value="15">15</option> <option value="30">30</option> <option value="45">45</option> </select> <select name="event_time_start_ampm"> <option value="blank" disabled="disabled">AM / PM</option> <option value="blank" disabled="disabled">&nbsp;</option> <option value="am">AM</option> <option value="pm">PM</option> </select> Quite simply, when either 'midnight' or 'midday' is selected in "event_time_start_hours", I want the values of "event_time_start_minutes" and "event_time_start_ampm" to change to "00" and "am" respectively. My VERY poor piece of Javascript says this so far : $(document).ready(function() { $('#event_time_start_hours').change(function() { if($('#event_time_start_hours').val('midnight')) { $('#event_time_start_minutes').val('00'); } }); }); ... and whilst I'm not terribly surprised it doesn't work, I'm at a loss as to what to do next. I want to do this purely for visual reasons for the user as when the form submits I ignore the "minutes" and "am/pm". I'm trying to decide whether it would be best to change the selected values, change the selected values and then disable the element or hide them altogether. However, without any success in getting anything to happen at all I haven't been able to try the different approaches to see what feels right. I've ruled out the obvious things like a duplicate element ID or simply not linking to JQuery. Thank you.

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  • Managing highly repetitive code and documentation in Java

    - by polygenelubricants
    Highly repetitive code is generally a bad thing, and there are design patterns that can help minimize this. However, sometimes it's simply inevitable due to the constraints of the language itself. Take the following example from java.util.Arrays: /** * Assigns the specified long value to each element of the specified * range of the specified array of longs. The range to be filled * extends from index <tt>fromIndex</tt>, inclusive, to index * <tt>toIndex</tt>, exclusive. (If <tt>fromIndex==toIndex</tt>, the * range to be filled is empty.) * * @param a the array to be filled * @param fromIndex the index of the first element (inclusive) to be * filled with the specified value * @param toIndex the index of the last element (exclusive) to be * filled with the specified value * @param val the value to be stored in all elements of the array * @throws IllegalArgumentException if <tt>fromIndex &gt; toIndex</tt> * @throws ArrayIndexOutOfBoundsException if <tt>fromIndex &lt; 0</tt> or * <tt>toIndex &gt; a.length</tt> */ public static void fill(long[] a, int fromIndex, int toIndex, long val) { rangeCheck(a.length, fromIndex, toIndex); for (int i=fromIndex; i<toIndex; i++) a[i] = val; } The above snippet appears in the source code 8 times, with very little variation in the documentation/method signature but exactly the same method body, one for each of the root array types int[], short[], char[], byte[], boolean[], double[], float[], and Object[]. I believe that unless one resorts to reflection (which is an entirely different subject in itself), this repetition is inevitable. I understand that as a utility class, such high concentration of repetitive Java code is highly atypical, but even with the best practice, repetition does happen! Refactoring doesn't always work because it's not always possible (the obvious case is when the repetition is in the documentation). Obviously maintaining this source code is a nightmare. A slight typo in the documentation, or a minor bug in the implementation, is multiplied by however many repetitions was made. In fact, the best example happens to involve this exact class: Google Research Blog - Extra, Extra - Read All About It: Nearly All Binary Searches and Mergesorts are Broken (by Joshua Bloch, Software Engineer) The bug is a surprisingly subtle one, occurring in what many thought to be just a simple and straightforward algorithm. // int mid =(low + high) / 2; // the bug int mid = (low + high) >>> 1; // the fix The above line appears 11 times in the source code! So my questions are: How are these kinds of repetitive Java code/documentation handled in practice? How are they developed, maintained, and tested? Do you start with "the original", and make it as mature as possible, and then copy and paste as necessary and hope you didn't make a mistake? And if you did make a mistake in the original, then just fix it everywhere, unless you're comfortable with deleting the copies and repeating the whole replication process? And you apply this same process for the testing code as well? Would Java benefit from some sort of limited-use source code preprocessing for this kind of thing? Perhaps Sun has their own preprocessor to help write, maintain, document and test these kind of repetitive library code? A comment requested another example, so I pulled this one from Google Collections: com.google.common.base.Predicates lines 276-310 (AndPredicate) vs lines 312-346 (OrPredicate). The source for these two classes are identical, except for: AndPredicate vs OrPredicate (each appears 5 times in its class) "And(" vs Or(" (in the respective toString() methods) #and vs #or (in the @see Javadoc comments) true vs false (in apply; ! can be rewritten out of the expression) -1 /* all bits on */ vs 0 /* all bits off */ in hashCode() &= vs |= in hashCode()

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  • Foreign Key constraint violation when persisting a many-to-one class

    - by tieTYT
    I'm getting an error when trying to persist a many to one entity: Internal Exception: org.postgresql.util.PSQLException: ERROR: insert or update on table "concept" violates foreign key constraint "concept_concept_class_fk" Detail: Key (concept_class_id)=(Concept) is not present in table "concept_class". Error Code: 0 Call: INSERT INTO concept (concept_key, description, label, code, concept_class_id) VALUES (?, ?, ?, ?, ?) bind = [27, description_1, label_1, code_1, Concept] Query: InsertObjectQuery(com.mirth.results.entities.Concept[conceptKey=27]) at com.sun.ejb.containers.BaseContainer.checkExceptionClientTx(BaseContainer.java:3728) at com.sun.ejb.containers.BaseContainer.postInvokeTx(BaseContainer.java:3576) at com.sun.ejb.containers.BaseContainer.postInvoke(BaseContainer.java:1354) ... 101 more Here is the method that tries to persist it. I've put a comment where the line is: @Override public void loadConcept(String metaDataFilePath, String dataFilePath) throws Exception { try { ConceptClassMetaData conceptClassMetaData = (ConceptClassMetaData) ModelSerializer.getInstance().fromXML(FileUtils.readFileToString(new File(metaDataFilePath), "UTF8")); em.executeNativeQuery(conceptClassMetaData.getCreateStatement()); ConceptClassRow conceptClassRow = conceptClassMetaData.getConceptClassRow(); ConceptClass conceptClass = em.findByPrimaryKey(ConceptClass.class, conceptClassRow.getId()); if (conceptClass == null) { conceptClass = new ConceptClass(conceptClassRow.getId()); } conceptClass.setLabel(conceptClassRow.getLabel()); conceptClass.setOid(conceptClassRow.getOid()); conceptClass.setDescription(conceptClassRow.getDescription()); conceptClass = em.merge(conceptClass); DataParser dataParser = new DataParser(conceptClassMetaData, dataFilePath); for (ConceptModel conceptModel : dataParser.getConceptRows()) { ConceptFilter<Concept> filter = new ConceptFilter<Concept>(Concept.class); filter.setCode(conceptModel.getCode()); filter.setConceptClass(conceptClass.getLabel()); List<Concept> concepts = em.findAllByFilter(filter); Concept concept = new Concept(); if (concepts != null && !concepts.isEmpty()) { concept = concepts.get(0); } concept.setCode(conceptModel.getCode()); concept.setDescription(conceptModel.getDescription()); concept.setLabel(conceptModel.getLabel()); concept.setConceptClass(conceptClass); concept = em.merge(concept); //THIS LINE CAUSES THE ERROR! } } catch (Exception e) { e.printStackTrace(); throw e; } } ... Here are how the two entities are defined: @Entity @Table(name = "concept") @Inheritance(strategy=InheritanceType.JOINED) @DiscriminatorColumn(name="concept_class_id", discriminatorType=DiscriminatorType.STRING) public class Concept extends KanaEntity { @Id @Basic(optional = false) @Column(name = "concept_key") protected Integer conceptKey; @Basic(optional = false) @Column(name = "code") private String code; @Basic(optional = false) @Column(name = "label") private String label; @Column(name = "description") private String description; @JoinColumn(name = "concept_class_id", referencedColumnName = "id") @ManyToOne private ConceptClass conceptClass; ... @Entity @Table(name = "concept_class") public class ConceptClass extends KanaEntity { @Id @Basic(optional = false) @Column(name = "id") private String id; @Basic(optional = false) @Column(name = "label") private String label; @Column(name = "oid") private String oid; @Column(name = "description") private String description; .... And also, what's important is the sql that's being generated: INSERT INTO concept_class (id, oid, description, label) VALUES (?, ?, ?, ?) bind = [LOINC_TEST, 2.16.212.31.231.54, This is a meta data file for LOINC_TEST, loinc_test] INSERT INTO concept (concept_key, description, label, code, concept_class_id) VALUES (?, ?, ?, ?, ?) bind = [27, description_1, label_1, code_1, Concept] The reason this is failing is obvious: It's inserting the word Concept for the concept_class_id. It should be inserting the word LOINC_TEST. I can't figure out why it's using this word. I've used the debugger to look at the Concept and the ConceptClass instance and neither of them contain this word. I'm using eclipselink. Does anyone know why this is happening?

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  • How do I imply code contracts of chained methods to avoid superfluous checks while chaining?

    - by Sandor Drieënhuizen
    I'm using Code Contracts in C# 4.0. I'm applying the usual static method chaining to simulate optional parameters (I know C# 4.0 supports optional parameters but I really don't want to use them). The thing is that my contract requirements are executed twice (or possibly the number of chained overloads I'd implement) if I call the Init(string , string[]) method -- an obvious effect from the sample source code below. This can be expensive, especially due to relatively expensive requirements like the File.Exists I use. public static void Init(string configurationPath, string[] mappingAssemblies) { // The static contract checker 'makes' me put these here as well as // in the overload below. Contract.Requires<ArgumentNullException>(configurationPath != null, "configurationPath"); Contract.Requires<ArgumentException>(configurationPath.Length > 0, "configurationPath is an empty string."); Contract.Requires<FileNotFoundException>(File.Exists(configurationPath), configurationPath); Contract.Requires<ArgumentNullException>(mappingAssemblies != null, "mappingAssemblies"); Contract.ForAll<string>(mappingAssemblies, (n) => File.Exists(n)); Init(configurationPath, mappingAssemblies, null); } public static void Init(string configurationPath, string[] mappingAssemblies, string optionalArgument) { // This is the main implementation of Init and all calls to chained // overloads end up here. Contract.Requires<ArgumentNullException>(configurationPath != null, "configurationPath"); Contract.Requires<ArgumentException>(configurationPath.Length > 0, "configurationPath is an empty string."); Contract.Requires<FileNotFoundException>(File.Exists(configurationPath), configurationPath); Contract.Requires<ArgumentNullException>(mappingAssemblies != null, "mappingAssemblies"); Contract.ForAll<string>(mappingAssemblies, (n) => File.Exists(n)); //... } If however, I remove the requirements from that method, the static checker complains that the requirements of the Init(string, string[], string) overload are not met. I reckon that the static checker doesn't understand that there requirements of the Init(string, string[], string) overload implicitly apply to the Init(string, string[]) method as well; something that would be perfectly deductable from the code IMO. This is the situation I would like to achieve: public static void Init(string configurationPath, string[] mappingAssemblies) { // I don't want to repeat the requirements here because they will always // be checked in the overload called here. Init(configurationPath, mappingAssemblies, null); } public static void Init(string configurationPath, string[] mappingAssemblies, string optionalArgument) { // This is the main implementation of Init and all calls to chained // overloads end up here. Contract.Requires<ArgumentNullException>(configurationPath != null, "configurationPath"); Contract.Requires<ArgumentException>(configurationPath.Length > 0, "configurationPath is an empty string."); Contract.Requires<FileNotFoundException>(File.Exists(configurationPath), configurationPath); Contract.Requires<ArgumentNullException>(mappingAssemblies != null, "mappingAssemblies"); Contract.ForAll<string>(mappingAssemblies, (n) => File.Exists(n)); //... } So, my question is this: is there a way to have the requirements of Init(string, string[], string) implicitly apply to Init(string, string[]) automatically?

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  • HTML / PHP form

    - by user317128
    I am trying to code an all in one HTML/PHP contact from with error checking. When I load this file in my browser there is not HTML. I am a newb php programmer so most likely forgot something pretty obvious. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>All In One Feedback Form</title> </head> <body> <? $form_block = " <input type=\"hidden\" name=\"op\" value=\"ds\"> <form method=\"post\" action=\"$server[PHP_SELF]\"> <p>Your name<br /> <input name=\"sender_name\" type=\"text\" size=30 value=\"$_POST[sender_name]\" /></p> <p>Email<br /> <input name=\"sender_email\" type=\"text\" size=30 value=\"$_POST[sender_email]\"/></p> <p>Message<br /> <textarea name=\"message\" cols=30 rows=5 value=\"$_POST[message]\"></textarea></p> <input name=\"submit\" type=\"submit\" value=\"Send This Form\" /> </form>"; if ($_POST[op] != "ds") { //they see this form echo "$form_block"; } else if ($_POST[op] == "ds") { if ($_POST[sender_name] == "") { $name_err = "Please enter your name<br>"; $send = "no"; } if ($_POST[sender_email] == "ds") { $email_err = "Please enter your email<br>"; $send = "no"; } if ($_POST[message] == "ds") { $message_err = "please enter message<br>"; $send = "no"; } if ($send != "no") { //its ok to send $to = "[email protected]"; $subject = "All in one web site feed back"; $mailheaders = "From: website <some email [email protected]> \n"; $mailheaders .= "Reply-To: $_POST[sender_email]\n"; $msg = "Email sent from this site www.ccccc.com\n"; $msg .= "Senders name: $_POST[senders_name]\n"; $msg .= "Sender's E-Mail: $_POST[sender_email]\n"; $msg .= "Message: $_POST[message]\n\n"; mail($to, $subject, $msg, $mailheaders); echo "<p>Mail has been sent</p>"; } else if ($send == "no") { echo "$name_err"; echo "$email_err"; echo "$message_err"; echo "$form_block"; } } ?> </body> </html> FYI I am trying the example from a book named PHP 6 Fast and Easy Wed Development

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  • Wordpress add_meta_box() weirdness

    - by Scott B
    The code below is working nearly flawlessly, however my value for page title on one of my pages keeps coming up empty after a few page refreshes... It sticks for awhile, then it appears to reset to empty. I'm thinking I must have a conflict in the code below, but I can't quite figure it. I'm allowing the user to set a custom page title for posts as well as pages via a custom "post/page title input field). Can anyone see an obvious issue here that might be resetting the page title to blank? // =================== // = POST OPTION BOX = // =================== add_action('admin_menu', 'my_post_options_box'); function my_post_options_box() { if ( function_exists('add_meta_box') ) { //add_meta_box( $id, $title, $callback, $page, $context, $priority ); add_meta_box('post_header', 'Custom Post Header Code (optional)', 'custom_post_images', 'post', 'normal', 'low'); add_meta_box('post_title', 'Custom Post Title', 'custom_post_title', 'post', 'normal', 'high'); add_meta_box('post_title_page', 'Custom Post Title', 'custom_post_title', 'page', 'normal', 'high'); add_meta_box('postexcerpt', __('Excerpt'), 'post_excerpt_meta_box', 'page', 'normal', 'core'); add_meta_box('categorydiv', __('Page Options'), 'post_categories_meta_box', 'page', 'side', 'core'); } } //Adds the custom images box function custom_post_images() { global $post; ?> <div class="inside"> <textarea style="height:70px; width:100%;margin-left:-5px;" name="customHeader" id="customHeader"><?php echo get_post_meta($post->ID, 'customHeader', true); ?></textarea> <p>Enter your custom html code here for the post page header/image area. Whatever you enter here will override the default post header or image listing <b>for this post only</b>. You can enter image references like so &lt;img src='wp-content/uploads/product1.jpg' /&gt;. To show default images, just leave this field empty</p> </div> <?php } //Adds the custom post title box function custom_post_title() { global $post; ?> <div class="inside"> <p><input style="height:25px;width:100%;margin-left:-10px;" type="text" name="customTitle" id="customTitle" value="<?php echo get_post_meta($post->ID, 'customTitle', true); ?>"></p> <p>Enter your custom post/page title here and it will be used for the html &lt;title&gt; for this post page and the Google link text used for this page.</p> </div> <?php } add_action('save_post', 'custom_add_save'); function custom_add_save($postID){ // called after a post or page is saved if($parent_id = wp_is_post_revision($postID)) { $postID = $parent_id; } if ($_POST['customHeader']) { update_custom_meta($postID, $_POST['customHeader'], 'customHeader'); } else { update_custom_meta($postID, '', 'customHeader'); } if ($_POST['customTitle']) { update_custom_meta($postID, $_POST['customTitle'], 'customTitle'); } else { update_custom_meta($postID, '', 'customTitle'); } } function update_custom_meta($postID, $newvalue, $field_name) { // To create new meta if(!get_post_meta($postID, $field_name)){ add_post_meta($postID, $field_name, $newvalue); }else{ // or to update existing meta update_post_meta($postID, $field_name, $newvalue); } } ?>

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  • Find optimal/good-enough strategy and AI for the game 'Proximity'?

    - by smci
    'Proximity' is a strategy game of territorial domination similar to Othello, Go and Risk. Two players, uses a 10x12 hex grid. Game invented by Brian Cable in 2007. Seems to be a worthy game for discussing a) optimal algorithm then b) how to build an AI. Strategies are going to be probabilistic or heuristic-based, due to the randomness factor, and the insane branching factor (20^120). So it will be kind of hard to compare objectively. A compute time limit of 5s per turn seems reasonable. Game: Flash version here and many copies elsewhere on the web Rules: here Object: to have control of the most armies after all tiles have been placed. Each turn you received a randomly numbered tile (value between 1 and 20 armies) to place on any vacant board space. If this tile is adjacent to any ally tiles, it will strengthen each tile's defenses +1 (up to a max value of 20). If it is adjacent to any enemy tiles, it will take control over them if its number is higher than the number on the enemy tile. Thoughts on strategy: Here are some initial thoughts; setting the computer AI to Expert will probably teach a lot: minimizing your perimeter seems to be a good strategy, to prevent flips and minimize worst-case damage like in Go, leaving holes inside your formation is lethal, only more so with the hex grid because you can lose armies on up to 6 squares in one move low-numbered tiles are a liability, so place them away from your main territory, near the board edges and scattered. You can also use low-numbered tiles to plug holes in your formation, or make small gains along the perimeter which the opponent will not tend to bother attacking. a triangle formation of three pieces is strong since they mutually reinforce, and also reduce the perimeter Each tile can be flipped at most 6 times, i.e. when its neighbor tiles are occupied. Control of a formation can flow back and forth. Sometimes you lose part of a formation and plug any holes to render that part of the board 'dead' and lock in your territory/ prevent further losses. Low-numbered tiles are obvious-but-low-valued liabilities, but high-numbered tiles can be bigger liabilities if they get flipped (which is harder). One lucky play with a 20-army tile can cause a swing of 200 (from +100 to -100 armies). So tile placement will have both offensive and defensive considerations. Comment 1,2,4 seem to resemble a minimax strategy where we minimize the maximum expected possible loss (modified by some probabilistic consideration of the value ß the opponent can get from 1..20 i.e. a structure which can only be flipped by a ß=20 tile is 'nearly impregnable'.) I'm not clear what the implications of comments 3,5,6 are for optimal strategy. Interested in comments from Go, Chess or Othello players. (The sequel ProximityHD for XBox Live, allows 4-player -cooperative or -competitive local multiplayer increases the branching factor since you now have 5 tiles in your hand at any given time, of which you can only play one. Reinforcement of ally tiles is increased to +2 per ally.)

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  • Cross-platform distributed fault-tolerant (disconnected operation/local cache) filesystem

    - by Adrian Frühwirth
    We are facing a design "challenge" where we are required to set up a storage solution with the following properties: What we need HA a scalable storage backend offline/disconnected operation on the client to account for network outages cross-platform access client-side access from certainly Windows (probably XP upwards), possibly Linux backend integrates with AD/LDAP (permission management (user/group management, ...)) should work reasonably well over slow WAN-links Another problem is that we don't really know all possible use cases here, if people need to be able to have concurrent access to shared files or if they will only be accessing their own files, so a possible solution needs to account for concurrent access and how conflict management would look in this case from a user's point of view. This two years old blog posts sums up the impression that I have been getting during the last couple of days of research, that there are lots of current übercool projects implementing (non-Windows) clustered petabyte-capable blob-storage solutions but that there is none that supports disconnected operation nicely and natively, but I am hoping that we have missed an obvious solution. What we have tried OpenAFS We figured that we want a distributed network filesystem with a local cache and tested OpenAFS (which, as the only currently "stable" DFS supporting disconnected operation, seemed the way to go) for a week but there are several problems with it: it's a real pain to set up there are no official RHEL/CentOS packages the package of the current stable version 1.6.5.1 from elrepo randomly kernel panics on fresh installs, this is an absolute no-go Windows support (including the required Kerberos packages) is mystical. The current client for the 1.6 branch does not run on Windows 8, the current client for the 1.7 does but it just randomly crashes. After that experience we didn't even bother testing on XP and Windows 7. Suffice to say, we couldn't get it working and the whole setup has been so unstable and complicated to setup that it's just not an option for production. Samba + Unison Since OpenAFS was a complete disaster and no other DFS seems to support disconnected operation we went for a simpler idea that would sync files against a Samba server using Unison. This has the following advantages: Samba integrates with ADs; it's a pain but can be done. Samba solves the problem of remotely accessing the storage from Windows but introduces another SPOF and does not address the actual storage problem. We could probably stick any clustered FS underneath Samba, but that means we need a HA Samba setup on top of that to maintain HA which probably adds a lot of additional complexity. I vaguely remember trying to implement redundancy with Samba before and I could not silently failover between servers. Even when online, you are working with local files which will result in more conflicts than would be necessary if a local cache were only touched when disconnected It's not automatic. We cannot expect users to manually sync their files using the (functional, but not-so-pretty) GTK GUI on a regular basis. I attempted to semi-automate the process using the Windows task scheduler, but you cannot really do it in a satisfactory way. On top of that, the way Unison works makes syncing against Samba a costly operation, so I am afraid that it just doesn't scale very well or even at all. Samba + "Offline Files" After that we became a little desparate and gave Windows "offline files" a chance. We figured that having something that is inbuilt into the OS would reduce administrative efforts, helps blaming someone else when it's not working properly and should just work since people have been using this for years. Right? Wrong. We really wanted it to work, but it just doesn't. 30 minutes of copying files around and unplugging network cables/disabling network interfaces left us with (silent! there is only a tiny notification in Windows explorer in the statusbar, which doesn't even open Sync Center if you click on it!) undeletable files on the server (!) and conflicts that should not even be conflicts. In the end, we had one successful sync of a tiny text file, everything else just exploded horribly. Beyond that, there are other problems: Microsoft admits that "offline files" in Windows XP cannot cope with "large files" and therefore does not cache/sync them at all which would mean those files become unavailable if the connection drop In Windows 7 the feature is only available in the Professional/Ultimate/Enterprise editions. Summary Unless there is another fault-tolerant DFS that supports Windows natively I assume that stacking a HA Samba cluster on top of something like GlusterFS/Lustre/whatnot is the only option, but I hope that I am wrong here. How do other companies allow fault-tolerant network access to redundant storage in a heterogeneous environment with Windows?

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  • Foreign Key constraint when persisting a many-to-one class

    - by tieTYT
    I'm getting an error when trying to persist a many to one entity: Internal Exception: org.postgresql.util.PSQLException: ERROR: insert or update on table "concept" violates foreign key constraint "concept_concept_class_fk" Detail: Key (concept_class_id)=(Concept) is not present in table "concept_class". Error Code: 0 Call: INSERT INTO concept (concept_key, description, label, code, concept_class_id) VALUES (?, ?, ?, ?, ?) bind = [27, description_1, label_1, code_1, Concept] Query: InsertObjectQuery(com.mirth.results.entities.Concept[conceptKey=27]) at com.sun.ejb.containers.BaseContainer.checkExceptionClientTx(BaseContainer.java:3728) at com.sun.ejb.containers.BaseContainer.postInvokeTx(BaseContainer.java:3576) at com.sun.ejb.containers.BaseContainer.postInvoke(BaseContainer.java:1354) ... 101 more Here is the method that tries to persist it. I've put a comment where the line is: @Override public void loadConcept(String metaDataFilePath, String dataFilePath) throws Exception { try { ConceptClassMetaData conceptClassMetaData = (ConceptClassMetaData) ModelSerializer.getInstance().fromXML(FileUtils.readFileToString(new File(metaDataFilePath), "UTF8")); em.executeNativeQuery(conceptClassMetaData.getCreateStatement()); ConceptClassRow conceptClassRow = conceptClassMetaData.getConceptClassRow(); ConceptClass conceptClass = em.findByPrimaryKey(ConceptClass.class, conceptClassRow.getId()); if (conceptClass == null) { conceptClass = new ConceptClass(conceptClassRow.getId()); } conceptClass.setLabel(conceptClassRow.getLabel()); conceptClass.setOid(conceptClassRow.getOid()); conceptClass.setDescription(conceptClassRow.getDescription()); conceptClass = em.merge(conceptClass); DataParser dataParser = new DataParser(conceptClassMetaData, dataFilePath); for (ConceptModel conceptModel : dataParser.getConceptRows()) { ConceptFilter<Concept> filter = new ConceptFilter<Concept>(Concept.class); filter.setCode(conceptModel.getCode()); filter.setConceptClass(conceptClass.getLabel()); List<Concept> concepts = em.findAllByFilter(filter); Concept concept = new Concept(); if (concepts != null && !concepts.isEmpty()) { concept = concepts.get(0); } concept.setCode(conceptModel.getCode()); concept.setDescription(conceptModel.getDescription()); concept.setLabel(conceptModel.getLabel()); concept.setConceptClass(conceptClass); concept = em.merge(concept); //THIS LINE CAUSES THE ERROR! } } catch (Exception e) { e.printStackTrace(); throw e; } } ... Here are how the two entities are defined: @Entity @Table(name = "concept") @Inheritance(strategy=InheritanceType.JOINED) @DiscriminatorColumn(name="concept_class_id", discriminatorType=DiscriminatorType.STRING) public class Concept extends KanaEntity { @Id @Basic(optional = false) @Column(name = "concept_key") protected Integer conceptKey; @Basic(optional = false) @Column(name = "code") private String code; @Basic(optional = false) @Column(name = "label") private String label; @Column(name = "description") private String description; @JoinColumn(name = "concept_class_id", referencedColumnName = "id") @ManyToOne private ConceptClass conceptClass; ... @Entity @Table(name = "concept_class") public class ConceptClass extends KanaEntity { @Id @Basic(optional = false) @Column(name = "id") private String id; @Basic(optional = false) @Column(name = "label") private String label; @Column(name = "oid") private String oid; @Column(name = "description") private String description; .... And also, what's important is the sql that's being generated: INSERT INTO concept_class (id, oid, description, label) VALUES (?, ?, ?, ?) bind = [LOINC_TEST, 2.16.212.31.231.54, This is a meta data file for LOINC_TEST, loinc_test] INSERT INTO concept (concept_key, description, label, code, concept_class_id) VALUES (?, ?, ?, ?, ?) bind = [27, description_1, label_1, code_1, Concept] The reason this is failing is obvious: It's inserting the word Concept for the concept_class_id. It should be inserting the word LOINC_TEST. I can't figure out why it's using this word. I've used the debugger to look at the Concept and the ConceptClass instance and neither of them contain this word. I'm using eclipselink. Does anyone know why this is happening?

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  • How do I evaluate my skillset against the current market to see what needs improvement and where my

    - by baijajusav
    First of all, this question may be out of bounds for this site. If so, remove it. I say this because this site seems to be a place for more concrete questions that are not so relative in nature. And before I begin, for those of you whom just prefer a question and not this sort of dialog, here is my question: How can I assess my current skills as a programmer and decide where and what areas to improve upon? That said, here's what I'm asking/talking about, in essence. The market is always in constant flux. As programmers we're always having to learn new things, update our skills, push ourselves into that next project. There's not a very good litmus test that I know of for us to get an idea of where we stand as programmers. I came across this blog post by Jeff Atwood talking about why can't programmers code. Instinctively (and as the post goes on to state) I rushed through the program in about 4 minutes (most of that time was b/c I was hand writing it out. Still, this doesn't really answer the question of where do my skills need to be to succeed in today's world. I real blogs, listen to podcasts, try to keep up on the latest things coming out. It has only been in the past couple of months that I made a decision to pick a focus area for my learning as I can't learn everything and trying to do so is to spread myself too thin. I chose ASP.NET MVC & C#. I plan to stick with Microsoft technologies, not out of some sense of loyalty or stubbornness, but rather because they seem to stream together and have a unifying connection between them. With Windows Phone 7 coming out, it seems that now is the obvious time to pick up WPF and Silverlight as well. Still, if you asked me to code something apart from intellisense and the internet, I probably couldn't get the syntax right. I don't have libraries memorized or know precisely where the classes I use exist within the .Net framework, namely because I haven't had to pull that knowledge out of the air. In a way, I suppose Visual Studio has insulated me, which isn't a good thing, but, at the same time, I've still been able to be productive. I'm working on my own side project to try and help my learning. In doing so, I'm trying to make use of best practices and 3rd party frameworks where I can. I'm using automapper and EF 1.0. I know everyone in the .net community seems to cry foul at the sound of EF 1.0, but I can't say why because I've never used it. There's no lazy loading and that has proven rather annoying; however, aside from that, I haven't had that much of an issue. Granted this is probably because I'm not writing tests as I go (which I'm not doing because I don't know how to test EF in tests and don't really have a clue how to write tests for ASP.NET MVC 1.0). I'm also using a custom membership provider; granted, it's a barebone implementation, but I'm using it still. My thinking in all of this is, while I am neglecting a great many important technologies that are in the mainstream, I'll have a working project in the end. I can come back and add those things after I finish. Doing it all now and at once seems like too much. I know how I work and I don't think I'd ever get it done that way. I've elected to make this a community wiki as I think this question might fight better there. If a moderator disagrees with that choice or the decision to post this here, the just delete the question. I'm not trying to make undue work for anyone. I'm just a programmer trying to assess my where his skills are now and where I should be improving.

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  • snmptt not translating traps, even with translate_log_trap_oid=1

    - by mbrownnyc
    I am having some trouble configuring snmptt to properly translate snmp traps. The following is a problem: /etc/snmp/snmptt.conf reflects: EVENT fgFmTrapIfChange .1.3.6.1.4.1.12356.101.6.0.1004 "Status Events" Critical FORMAT $* EXEC /usr/local/nagios/libexec/eventhandlers/submit_check_result $r "snmp_traps" 2 "$O: $+*" "$*" SDESC Trap is sent to the managing FortiManager if an interface IP is changed Variables: 1: fnSysSerial 2: ifName 3: fgManIfIp 4: fgManIfMask EDESC when a trap is received, /var/log/messages reflects: Sep 6 12:07:32 SNMPMANAGERHOST snmptrapd[15385]: 2012-09-06 12:07:32 <UNKNOWN> [UDP: [192.168.100.2]:162->[192.168.100.31]]: #012.1.3.6.1.2.1.1.3.0 = Timeticks: (707253943) 81 days, 20:35:39.43 #011.1.3.6.1.6.3.1.1.4.1.0 = OID: .1.3.6.1.4.1.12356.101.6.0.1004 #011.1.3.6.1.4.1.12356.100.1.1.1.0 = STRING: FGTNNNNNNNNN #011.1.3.6.1.2.1.31.1.1.1.1.10 = STRING: internal4 #011.1.3.6.1.4.1.12356.101.6.2.1.0 = IpAddress: 192.168.65.100 #011.1.3.6.1.4.1.12356.101.6.2.2.0 = IpAddress: 255.255.255.0 Sep 6 12:07:37 SNMPMANAGERHOST icinga: EXTERNAL COMMAND: PROCESS_SERVICE_CHECK_RESULT; 192.168.100.2; snmp_traps; 2; enterprises.12356.101.6.0.1004: enterprises.12356.100.1.1.1.0:FGTNNNNNNNNN ifName.10:internal4 enterprises.12356.101.6.2.1.0:192.168.65.100 enterprises.12356.101.6.2.2.0:255.255.255.0 Since the icinga entry reflects the EXEC, it's obvious there is no translations occurring by snmptt. I have verified that translate_log_trap_oid and net_snmp_perl_enable is enabled in snmptt.ini When using --debug=1 to start snmptt, I see the following in the --debugfile: ********** Net-SNMP version 5.05 Perl module enabled ********** The main NET-SNMP version is reported as NET-SNMP version: 5.5. What else can be done to verify that snmptt is configured properly to translate traps? I have run snmptt-net-snmp-test to verify whatever net-snmp-perl version I have installed properly supports translations. The output indicates it does. /root/snmptt_1.3/snmptt-net-snmp-test --best_guess=2 SNMPTT Net-SNMP Test v1.0 (c) 2003 Alex Burger http://snmptt.sourceforge.net MIBS:RFC1213-MIB best_guess: 2 Testing translateObj ******************** Testing: .1.3.6.1.2.1.1.1, long_names=disabled, include_module=disabled Test passed. Result: sysDescr Testing: .1.3.6.1.2.1.1.1, long_names=disabled, include_module=enabled Test passed. Result: RFC1213-MIB::sysDescr Testing: .1.3.6.1.2.1.1.1, long_names=enabled, include_module=disabled Test passed. Result: .iso.org.dod.internet.mgmt.mib-2.system.sysDescr Testing: .1.3.6.1.2.1.1.1, long_names=enabled, include_module=enabled Test passed. Result: RFC1213-MIB::.iso.org.dod.internet.mgmt.mib-2.system.sysDescr Testing: sysDescr, long_names=disabled, include_module=disabled Test passed. Result: .1.3.6.1.2.1.1.1 Testing: RFC1213-MIB::sysDescr, long_names=disabled, include_module=disabled Test passed. Result: .1.3.6.1.2.1.1.1 Testing: system.sysDescr, long_names=disabled, include_module=disabled Test passed. Result: .1.3.6.1.2.1.1.1 Testing: RFC1213-MIB::system.sysDescr, long_names=disabled, include_module=disabled Test passed. Result: .1.3.6.1.2.1.1.1 Testing: .iso.org.dod.internet.mgmt.mib-2.system.sysDescr, long_names=disabled, include_module=disabled Test passed. Result: .1.3.6.1.2.1.1.1 Testing getType *************** Testing: .1.3.6.1.2.1.4.1 Test passed. Result: INTEGER Testing: ipForwarding Test passed. Result: INTEGER Testing Description ******************* Test passed. Result: ------------------------------------------------- The indication of whether this entity is acting as an IP gateway in respect to the forwarding of datagrams received by, but not addressed to, this entity. IP gateways forward datagrams. IP hosts do not (except those source-routed via the host). Note that for some managed nodes, this object may take on only a subset of the values possible. Accordingly, it is appropriate for an agent to return a `badValue' response if a management station attempts to change this object to an inappropriate value. ------------------------------------------------- I have manually gone through the MIB with the definition that's not resolving, and verified that it is properly linking back to the proper resolved definition. It is: FORTINET-FORTIGATE-MIB.txt contains: fgFmTrapIfChange NOTIFICATION-TYPE OBJECTS { fnSysSerial, ifName, fgManIfIp, fgManIfMask } STATUS current DESCRIPTION "Trap is sent to the managing FortiManager if an interface IP is changed" ::= { fgFmTrapPrefix 1004 } fgFmTrapPrefix OBJECT IDENTIFIER ::= { fgMgmt 0 } fgMgmt OBJECT IDENTIFIER ::= { fnFortiGateMib 6 } fnFortiGateMib ::= { fortinet 101 } IMPORTS FnBoolState, FnIndex, fnAdminEntry, fnSysSerial, fortinet FROM FORTINET-CORE-MIB fortinet MODULE-IDENTITY ::= { enterprises 12356 } LOOKS GOOD!!!!! 1.3.6.1.4.1.12356.101.6.0.1004 I've exhausted all the documentation and even posted fruitlessly in the snmptt-users mailing list. I can not prove it is the MIB. Why would snmptt fail to translate traps? Thanks, Matt

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  • Implementing ZBar QR Code Reader in UIView

    - by Bobster4300
    I really need help here. I'm pretty new to iOS/Objective-C so sorry if the problem resolution is obvious or if my code is terrible. Be easy on me!! :-) I'm struggling to integrate ZBarSDK for reading QR Codes into an iPad app i'm building. If I use ZBarReaderController (of which there are plenty of tutorials and guides on implementing), it works fine. However I want to make the camera come up in a UIView as opposed to the fullscreen camera. Now I have gotten as far as making the camera view (readerView) come up in the UIView (ZBarReaderView) as expected, but I get an error when it scans a code. The error does not come up until a code is scanned making me believe this is either delegate related or something else. Here's the important parts of my code: (ZBarSDK.h is imported at the PCH file) SignInViewController.h #import <UIKit/UIKit.h> #import <AVFoundation/AVFoundation.h> @class AVCaptureSession, AVCaptureDevice; @interface SignInViewController : UIViewController < ZBarReaderDelegate > { ZBarReaderView *readerView; UITextView *resultText; } @property (nonatomic, retain) UIImagePickerController *imgPicker; @property (strong, nonatomic) IBOutlet UITextView *resultText; @property (strong, nonatomic) IBOutlet ZBarReaderView *readerView; -(IBAction)StartScan:(id) sender; SignInViewController.m #import "SignInViewController.h" @interface SignInViewController () @end @implementation SignInViewController @synthesize resultText, readerView; -(IBAction)StartScan:(id) sender { readerView = [ZBarReaderView new]; readerView.readerDelegate = self; readerView.tracksSymbols = NO; readerView.frame = CGRectMake(30,70,230,230); readerView.torchMode = 0; readerView.device = [self frontFacingCameraIfAvailable]; ZBarImageScanner *scanner = readerView.scanner; [scanner setSymbology: ZBAR_I25 config: ZBAR_CFG_ENABLE to: 0]; [self relocateReaderPopover:[self interfaceOrientation]]; [readerView start]; [self.view addSubview: readerView]; resultText.hidden=NO; } - (void) readerControllerDidFailToRead: (ZBarReaderController*) reader withRetry: (BOOL) retry{ NSLog(@"the image picker failing to read"); } - (void) imagePickerController: (UIImagePickerController*) reader didFinishPickingMediaWithInfo: (NSDictionary*) info { NSLog(@"the image picker is calling successfully %@",info); id<NSFastEnumeration> results = [info objectForKey: ZBarReaderControllerResults]; ZBarSymbol *symbol = nil; NSString *hiddenData; for(symbol in results) hiddenData=[NSString stringWithString:symbol.data]; NSLog(@"the symbols is the following %@",symbol.data); resultText.text=symbol.data; NSLog(@"BARCODE= %@",symbol.data); NSLog(@"SYMBOL : %@",hiddenData); resultText.text=hiddenData; } The error I get when a code is scanned: 2012-12-16 14:28:32.797 QRTestApp[7970:907] -[SignInViewController readerView:didReadSymbols:fromImage:]: unrecognized selector sent to instance 0x1e88b1c0 2012-12-16 14:28:32.799 QRTestApp[7970:907] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[SignInViewController readerView:didReadSymbols:fromImage:]: unrecognized selector sent to instance 0x1e88b1c0' I'm not too worried about what happens with the results just yet, just want to get over this error. Took me ages just to get the camera to come up in the UIView due to severe lack of tutorial or documentation on ZBarReaderView (for beginners anyway). Thanks all.

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  • Rx IObservable buffering to smooth out bursts of events

    - by Dan
    I have an Observable sequence that produces events in rapid bursts (ie: five events one right after another, then a long delay, then another quick burst of events, etc.). I want to smooth out these bursts by inserting a short delay between events. Imagine the following diagram as an example: Raw: --oooo--------------ooooo-----oo----------------ooo| Buffered: --o--o--o--o--------o--o--o--o--o--o--o---------o--o--o| My current approach is to generate a metronome-like timer via Observable.Interval() that signals when it's ok to pull another event from the raw stream. The problem is that I can't figure out how to then combine that timer with my raw unbuffered observable sequence. IObservable.Zip() is close to doing what I want, but it only works so long as the raw stream is producing events faster than the timer. As soon as there is a significant lull in the raw stream, the timer builds up a series of unwanted events that then immediately pair up with the next burst of events from the raw stream. Ideally, I want an IObservable extension method with the following function signature that produces the bevaior I've outlined above. Now, come to my rescue StackOverflow :) public static IObservable<T> Buffered(this IObservable<T> src, TimeSpan minDelay) PS. I'm brand new to Rx, so my apologies if this is a trivially simple question... 1. Simple yet flawed approach Here's my initial naive and simplistic solution that has quite a few problems: public static IObservable<T> Buffered<T>(this IObservable<T> source, TimeSpan minDelay) { Queue<T> q = new Queue<T>(); source.Subscribe(x => q.Enqueue(x)); return Observable.Interval(minDelay).Where(_ => q.Count > 0).Select(_ => q.Dequeue()); } The first obvious problem with this is that the IDisposable returned by the inner subscription to the raw source is lost and therefore the subscription can't be terminated. Calling Dispose on the IDisposable returned by this method kills the timer, but not the underlying raw event feed that is now needlessly filling the queue with nobody left to pull events from the queue. The second problem is that there's no way for exceptions or end-of-stream notifications to be propogated through from the raw event stream to the buffered stream - they are simply ignored when subscribing to the raw source. And last but not least, now I've got code that wakes up periodically regardless of whether there is actually any work to do, which I'd prefer to avoid in this wonderful new reactive world. 2. Way overly complex appoach To solve the problems encountered in my initial simplistic approach, I wrote a much more complicated function that behaves much like IObservable.Delay() (I used .NET Reflector to read that code and used it as the basis of my function). Unfortunately, a lot of the boilerplate logic such as AnonymousObservable is not publicly accessible outside the system.reactive code, so I had to copy and paste a lot of code. This solution appears to work, but given its complexity, I'm less confident that its bug free. I just can't believe that there isn't a way to accomplish this using some combination of the standard Reactive extensions. I hate feeling like I'm needlessly reinventing the wheel, and the pattern I'm trying to build seems like a fairly standard one.

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  • Two UIViews, one UIViewController (in one UINavigationController)

    - by jdandrea
    Given an iPhone app with a UITableViewController pushed onto a UINavigationController, I would like to add a right bar button item to toggle between the table view and an "alternate" view of the same data. Let's also say that this other view uses the same data but is not a UITableView. Now, I know variations on this question already exist on Stack Overflow. However, in this case, that alternate view would not be pushed onto the UINavigationController. It would be visually akin to flipping the current UIViewController's table view over and revealing the other view, then being able to flip back. In other words, it's intended to take up a single spot in the UINavigationController hierarchy. Moreover, whatever selection you ultimately make from within either view will push a common UIViewController onto the UINavigationController stack. Still more info: We don't want to use a separate UINavigationController just to handle this pair of views, and we don't want to split these apart via a UITabBarController either. Visually and contextually, the UX is meant to show two sides of the same coin. It's just that those two sides happen to involve their own View Controllers in normal practice. Now … it turns out I have already gone and quickly set this up to see how it might work! However, upon stepping back to examine it, I get the distinct impression that I went about it in a rather non-MVC way, which of course concerns me a bit. Here's what I did at a high level. Right now, I have a UIViewController (not a UITableViewController) that handles all commonalities between the two views, such as fetching the raw data. I also have two NIBs, one for each view, and two UIView objects to go along with them. (One of them is a UITableView, which is a kind of UIView.) I switch between the views using animation (easy enough). Also, in an effort to keep things encapsulated, the now-split-apart UITableView (not the UIViewController!) acts as its own delegate and data source, fetching data from the VC. The VC is set up as a weak, non-retained object in the table view. In parallel, the alternate view gets at the raw data from the VC in the exact same way. So, there are a few things that smell funny here. The weak linking from child to parent, while polite, seems like it might be wrong. Making a UITableView the table's data source and delegate also seems odd to me, thinking that a view controller is where you want to put that per Apple's MVC diagrams. As it stands now, it would appear as if the view knows about the model, which isn't good. Loading up both views in advance also seems odd, because lazy loading is no longer in effect. Losing the benefits of a UITableViewController (like auto-scrolling to cells with text fields) is also a bit frustrating, and I'd rather not reinvent the wheel to work around that as well. Given all of the above, and given we want that "flip effect" in the context of a single spot on a single UINavigationController, and given that both views are two sides of the same coin, is there a better, more obvious way to design this that I'm just happening to miss completely? Clues appreciated!

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  • Architecture for Qt SIGNAL with subclass-specific, templated argument type

    - by Barry Wark
    I am developing a scientific data acquisition application using Qt. Since I'm not a deep expert in Qt, I'd like some architecture advise from the community on the following problem: The application supports several hardware acquisition interfaces but I would like to provide an common API on top of those interfaces. Each interface has a sample data type and a units for its data. So I'm representing a vector of samples from each device as a std::vector of Boost.Units quantities (i.e. std::vector<boost::units::quantity<unit,sample_type> >). I'd like to use a multi-cast style architecture, where each data source broadcasts newly received data to 1 or more interested parties. Qt's Signal/Slot mechanism is an obvious fit for this style. So, I'd like each data source to emit a signal like typedef std::vector<boost::units::quantity<unit,sample_type> > SampleVector signals: void samplesAcquired(SampleVector sampleVector); for the unit and sample_type appropriate for that device. Since tempalted QObject subclasses aren't supported by the meta-object compiler, there doesn't seem to be a way to have a (tempalted) base class for all data sources which defines the samplesAcquired Signal. In other words, the following won't work: template<T,U> //sample type and units class DataSource : public QObject { Q_OBJECT ... public: typedef std::vector<boost::units::quantity<U,T> > SampleVector signals: void samplesAcquired(SampleVector sampleVector); }; The best option I've been able to come up with is a two-layered approach: template<T,U> //sample type and units class IAcquiredSamples { public: typedef std::vector<boost::units::quantity<U,T> > SampleVector virtual shared_ptr<SampleVector> acquiredData(TimeStamp ts, unsigned long nsamples); }; class DataSource : public QObject { ... signals: void samplesAcquired(TimeStamp ts, unsigned long nsamples); }; The samplesAcquired signal now gives a timestamp and number of samples for the acquisition and clients must use the IAcquiredSamples API to retrieve those samples. Obviously data sources must subclass both DataSource and IAcquiredSamples. The disadvantage of this approach appears to be a loss of simplicity in the API... it would be much nicer if clients could get the acquired samples in the Slot connected. Being able to use Qt's queued connections would also make threading issues easier instead of having to manage them in the acquiredData method within each subclass. One other possibility, is to use a QVariant argument. This necessarily puts the onus on subclass to register their particular sample vector type with Q_REGISTER_METATYPE/qRegisterMetaType. Not really a big deal. Clients of the base class however, will have no way of knowing what type the QVariant value type is, unless a tag struct is also passed with the signal. I consider this solution at least as convoluted as the one above, as it forces clients of the abstract base class API to deal with some of the gnarlier aspects of type system. So, is there a way to achieve the templated signal parameter? Is there a better architecture than the one I've proposed?

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  • C# thread functions not properly sharing a static data member

    - by Umer
    I have a class as following public class ScheduledUpdater { private static Queue<int> PendingIDs = new Queue<int>(); private static bool UpdateThreadRunning = false; private static bool IsGetAndSaveScheduledUpdateRunning = false; private static DataTable ScheduleConfiguration; private static Thread updateRefTableThread; private static Thread threadToGetAndSaveScheduledUpdate; public static void ProcessScheduledUpdates(int ID) { //do some stuff // if ( updateRefTableThread not already running) // execute updateRefTableThread = new Thread(new ThreadStart(UpdateSchedulingRefTableInThrear)); // execute updateRefTableThread.Start(); //do some stuff GetAndSaveScheduledUpdate(ID) } private static void UpdateSchedulingRefTableInThrear() { UpdateSchedulingRefTable(); } public static void UpdateSchedulingRefTable() { // read DB and update ScheduleConfiguration string query = " SELECT ID,TimeToSendEmail FROM TBLa WHERE MODE = 'WebServiceOrder' AND BDELETE = false "; clsCommandBuilder commandBuilder = new clsCommandBuilder(); DataSet ds = commandBuilder.GetDataSet(query); if (ds != null && ds.Tables.Count > 0 && ds.Tables[0].Rows.Count > 0) { List<string> lstIDs = new List<string>(); for (int i = 0; i < ds.Tables[0].Rows.Count; i++) { lstIDs.Add(ds.Tables[0].Rows[i]["ID"].ToString()); if (LastEmailSend.Contains(ds.Tables[0].Rows[i]["ID"].ToString())) LastEmailSend[ds.Tables[0].Rows[i]["ID"].ToString()] = ds.Tables[0].Rows[i]["TimeToSendEmail"].ToString(); else LastEmailSend.Add(ds.Tables[0].Rows[i]["ID"].ToString(), ds.Tables[0].Rows[i]["TimeToSendEmail"].ToString()); } if (lstIDs.Count > 0) { string Ids = string.Join(",", lstIDs.ToArray()).Trim(','); dhDBNames dbNames = new dhDBNames(); dbNames.Default_DB_Name = dbNames.ControlDB; dhGeneralPurpose dhGeneral = new dhGeneralPurpose(); dhGeneral.StringDH = Ids; DataSet result = commandBuilder.GetDataSet(dbNames, (object)dhGeneral, "xmlGetConfigurations"); if (result != null && result.Tables.Count > 0) { if (ScheduleConfiguration != null) ScheduleConfiguration.Clear(); ScheduleConfiguration = result.Tables[0]; } } } } public static void GetAndSaveScheduledUpdate(int ID) { //use ScheduleConfiguration if (ScheduleConfiguration == null)[1] UpdateSchedulingRefTable(); DataRow[] result = ScheduleConfiguration.Select("ID = "+ID); //then for each result row, i add this to a static Queue PendingIDs } } The function UpdateSchedulingRefTable can be called any time from outside world (for instance if someone updates the schedule configuration manually) ProcessScheduledUpdates is called from a windows service every other minute. Problem: Datatable ScheduleConfiguration is updated in the UpdateSchedulingRefTable (called from outside world - say manually) but when i try to use Datatable ScheduleConfiguration in GetAndSaveScheduledUpdate, i get the older version of values.... What am I missing in this stuff??? About EDIT: I thought the stuff i have not shown is quite obvious and possibly not desired, perhaps my structure is wrong :) and sorry for incorrect code previously, i made a simple function call as a thread initialization... sorry for my code indentation too because i don't know how to format whole block...

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  • Use QuickCheck by generating primes

    - by Dan
    Background For fun, I'm trying to write a property for quick-check that can test the basic idea behind cryptography with RSA. Choose two distinct primes, p and q. Let N = p*q e is some number relatively prime to (p-1)(q-1) (in practice, e is usually 3 for fast encoding) d is the modular inverse of e modulo (p-1)(q-1) For all x such that 1 < x < N, it is always true that (x^e)^d = x modulo N In other words, x is the "message", raising it to the eth power mod N is the act of "encoding" the message, and raising the encoded message to the dth power mod N is the act of "decoding" it. (The property is also trivially true for x = 1, a case which is its own encryption) Code Here are the methods I have coded up so far: import Test.QuickCheck -- modular exponentiation modExp :: Integral a => a -> a -> a -> a modExp y z n = modExp' (y `mod` n) z `mod` n where modExp' y z | z == 0 = 1 | even z = modExp (y*y) (z `div` 2) n | odd z = (modExp (y*y) (z `div` 2) n) * y -- relatively prime rPrime :: Integral a => a -> a -> Bool rPrime a b = gcd a b == 1 -- multiplicative inverse (modular) mInverse :: Integral a => a -> a -> a mInverse 1 _ = 1 mInverse x y = (n * y + 1) `div` x where n = x - mInverse (y `mod` x) x -- just a quick way to test for primality n `divides` x = x `mod` n == 0 primes = 2:filter isPrime [3..] isPrime x = null . filter (`divides` x) $ takeWhile (\y -> y*y <= x) primes -- the property prop_rsa (p,q,x) = isPrime p && isPrime q && p /= q && x > 1 && x < n && rPrime e t ==> x == (x `powModN` e) `powModN` d where e = 3 n = p*q t = (p-1)*(q-1) d = mInverse e t a `powModN` b = modExp a b n (Thanks, google and random blog, for the implementation of modular multiplicative inverse) Question The problem should be obvious: there are way too many conditions on the property to make it at all usable. Trying to invoke quickCheck prop_rsa in ghci made my terminal hang. So I've poked around the QuickCheck manual a bit, and it says: Properties may take the form forAll <generator> $ \<pattern> -> <property> How do I make a <generator> for prime numbers? Or with the other constraints, so that quickCheck doesn't have to sift through a bunch of failed conditions? Any other general advice (especially regarding QuickCheck) is welcome.

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  • Are free operator->* overloads evil?

    - by Potatoswatter
    I was perusing section 13.5 after refuting the notion that built-in operators do not participate in overload resolution, and noticed that there is no section on operator->*. It is just a generic binary operator. Its brethren, operator->, operator*, and operator[], are all required to be non-static member functions. This precludes definition of a free function overload to an operator commonly used to obtain a reference from an object. But the uncommon operator->* is left out. In particular, operator[] has many similarities. It is binary (they missed a golden opportunity to make it n-ary), and it accepts some kind of container on the left and some kind of locator on the right. Its special-rules section, 13.5.5, doesn't seem to have any actual effect except to outlaw free functions. (And that restriction even precludes support for commutativity!) So, for example, this is perfectly legal (in C++0x, remove obvious stuff to translate to C++03): #include <utility> #include <iostream> #include <type_traits> using namespace std; template< class F, class S > typename common_type< F,S >::type operator->*( pair<F,S> const &l, bool r ) { return r? l.second : l.first; } template< class T > T & operator->*( pair<T,T> &l, bool r ) { return r? l.second : l.first; } template< class T > T & operator->*( bool l, pair<T,T> &r ) { return l? r.second : r.first; } int main() { auto x = make_pair( 1, 2.3 ); cerr << x->*false << " " << x->*4 << endl; auto y = make_pair( 5, 6 ); y->*(0) = 7; y->*0->*y = 8; // evaluates to 7->*y = y.second cerr << y.first << " " << y.second << endl; } I can certainly imagine myself giving into temp[la]tation. For example, scaled indexes for vector: v->*matrix_width[2][5] = x; Did the standards committee forget to prevent this, was it considered too ugly to bother, or are there real-world use cases?

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  • When should I use indexed arrays of OpenGL vertices?

    - by Tartley
    I'm trying to get a clear idea of when I should be using indexed arrays of OpenGL vertices, drawn with gl[Multi]DrawElements and the like, versus when I should simply use contiguous arrays of vertices, drawn with gl[Multi]DrawArrays. (Update: The consensus in the replies I got is that one should always be using indexed vertices.) I have gone back and forth on this issue several times, so I'm going to outline my current understanding, in the hopes someone can either tell me I'm now finally more or less correct, or else point out where my remaining misunderstandings are. Specifically, I have three conclusions, in bold. Please correct them if they are wrong. One simple case is if my geometry consists of meshes to form curved surfaces. In this case, the vertices in the middle of the mesh will have identical attributes (position, normal, color, texture coord, etc) for every triangle which uses the vertex. This leads me to conclude that: 1. For geometry with few seams, indexed arrays are a big win. Follow rule 1 always, except: For geometry that is very 'blocky', in which every edge represents a seam, the benefit of indexed arrays is less obvious. To take a simple cube as an example, although each vertex is used in three different faces, we can't share vertices between them, because for a single vertex, the surface normals (and possible other things, like color and texture co-ord) will differ on each face. Hence we need to explicitly introduce redundant vertex positions into our array, so that the same position can be used several times with different normals, etc. This means that indexed arrays are of less use. e.g. When rendering a single face of a cube: 0 1 o---o |\ | | \ | | \| o---o 3 2 (this can be considered in isolation, because the seams between this face and all adjacent faces mean than none of these vertices can be shared between faces) if rendering using GL_TRIANGLE_FAN (or _STRIP), then each face of the cube can be rendered thus: verts = [v0, v1, v2, v3] colors = [c0, c0, c0, c0] normal = [n0, n0, n0, n0] Adding indices does not allow us to simplify this. From this I conclude that: 2. When rendering geometry which is all seams or mostly seams, when using GL_TRIANGLE_STRIP or _FAN, then I should never use indexed arrays, and should instead always use gl[Multi]DrawArrays. (Update: Replies indicate that this conclusion is wrong. Even though indices don't allow us to reduce the size of the arrays here, they should still be used because of other performance benefits, as discussed in the comments) The only exception to rule 2 is: When using GL_TRIANGLES (instead of strips or fans), then half of the vertices can still be re-used twice, with identical normals and colors, etc, because each cube face is rendered as two separate triangles. Again, for the same single cube face: 0 1 o---o |\ | | \ | | \| o---o 3 2 Without indices, using GL_TRIANGLES, the arrays would be something like: verts = [v0, v1, v2, v2, v3, v0] normals = [n0, n0, n0, n0, n0, n0] colors = [c0, c0, c0, c0, c0, c0] Since a vertex and a normal are often 3 floats each, and a color is often 3 bytes, that gives, for each cube face, about: verts = 6 * 3 floats = 18 floats normals = 6 * 3 floats = 18 floats colors = 6 * 3 bytes = 18 bytes = 36 floats and 18 bytes per cube face. (I understand the number of bytes might change if different types are used, the exact figures are just for illustration.) With indices, we can simplify this a little, giving: verts = [v0, v1, v2, v3] (4 * 3 = 12 floats) normals = [n0, n0, n0, n0] (4 * 3 = 12 floats) colors = [c0, c0, c0, c0] (4 * 3 = 12 bytes) indices = [0, 1, 2, 2, 3, 0] (6 shorts) = 24 floats + 12 bytes, and maybe 6 shorts, per cube face. See how in the latter case, vertices 0 and 2 are used twice, but only represented once in each of the verts, normals and colors arrays. This sounds like a small win for using indices, even in the extreme case of every single geometry edge being a seam. This leads me to conclude that: 3. When using GL_TRIANGLES, one should always use indexed arrays, even for geometry which is all seams. Please correct my conclusions in bold if they are wrong.

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  • Why does jquery leak memory so badly?

    - by Thomas Lane
    This is kind of a follow-up to a question I posted last week: http://stackoverflow.com/questions/2429056/simple-jquery-ajax-call-leaks-memory-in-ie I love the jquery syntax and all of its nice features, but I've been having trouble with a page that automatically updates table cells via ajax calls leaking memory. So I created two simple test pages for experimenting. Both pages do an ajax call every .1 seconds. After each successful ajax call, a counter is incremented and the DOM is updated. The script stops after 1000 cycles. One uses jquery for both the ajax call and to update the DOM. The other uses the Yahoo API for the ajax and does a document.getElementById(...).innerHTML to update the DOM. The jquery version leaks memory badly. Running in drip (on XP Home with IE7), it starts at 9MB and finishes at about 48MB, with memory growing linearly the whole time. If I comment out the line that updates the DOM, it still finishes at 32MB, suggesting that even simple DOM updates leak a significant amount of memory. The non-jquery version starts and finishes at about 9MB, regardless of whether it updates the DOM. Does anyone have a good explanation of what is causing jquery to leak so badly? Am I missing something obvious? Is there a circular reference that I'm not aware of? Or does jquery just have some serious memory issues? Here is the source for the leaky (jquery) version: <html> <head> <script type="text/javascript" src="http://www.google.com/jsapi"></script> <script type="text/javascript"> google.load('jquery', '1.4.2'); </script> <script type="text/javascript"> var counter = 0; leakTest(); function leakTest() { $.ajax({ url: '/html/delme.x', type: 'GET', success: incrementCounter }); } function incrementCounter(data) { if (counter<1000) { counter++; $('#counter').text(counter); setTimeout(leakTest,100); } else $('#counter').text('finished.'); } </script> </head> <body> <div>Why is memory usage going up?</div> <div id="counter"></div> </body> </html> And here is the non-leaky version: <html> <head> <script type="text/javascript" src="http://yui.yahooapis.com/2.8.0r4/build/yahoo/yahoo-min.js"></script> <script type="text/javascript" src="http://yui.yahooapis.com/2.8.0r4/build/event/event-min.js"></script> <script type="text/javascript" src="http://yui.yahooapis.com/2.8.0r4/build/connection/connection_core-min.js"></script> <script type="text/javascript"> var counter = 0; leakTest(); function leakTest() { YAHOO.util.Connect.asyncRequest('GET', '/html/delme.x', {success:incrementCounter}); } function incrementCounter(o) { if (counter<1000) { counter++; document.getElementById('counter').innerHTML = counter; setTimeout(leakTest,100); } else document.getElementById('counter').innerHTML = 'finished.' } </script> </head> <body> <div>Memory usage is stable, right?</div> <div id="counter"></div> </body> </html>

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  • How to find minimum weight with maximum cost in 0-1 Knapsack algorithm?

    - by Nitin9791
    I am trying to solve a spoj problem Party Schedule the problem statement is- You just received another bill which you cannot pay because you lack the money. Unfortunately, this is not the first time to happen, and now you decide to investigate the cause of your constant monetary shortness. The reason is quite obvious: the lion's share of your money routinely disappears at the entrance of party localities. You make up your mind to solve the problem where it arises, namely at the parties themselves. You introduce a limit for your party budget and try to have the most possible fun with regard to this limit. You inquire beforehand about the entrance fee to each party and estimate how much fun you might have there. The list is readily compiled, but how do you actually pick the parties that give you the most fun and do not exceed your budget? Write a program which finds this optimal set of parties that offer the most fun. Keep in mind that your budget need not necessarily be reached exactly. Achieve the highest possible fun level, and do not spend more money than is absolutely necessary. Input The first line of the input specifies your party budget and the number n of parties. The following n lines contain two numbers each. The first number indicates the entrance fee of each party. Parties cost between 5 and 25 francs. The second number indicates the amount of fun of each party, given as an integer number ranging from 0 to 10. The budget will not exceed 500 and there will be at most 100 parties. All numbers are separated by a single space. There are many test cases. Input ends with 0 0. Output For each test case your program must output the sum of the entrance fees and the sum of all fun values of an optimal solution. Both numbers must be separated by a single space. Example Sample input: 50 10 12 3 15 8 16 9 16 6 10 2 21 9 18 4 12 4 17 8 18 9 50 10 13 8 19 10 16 8 12 9 10 2 12 8 13 5 15 5 11 7 16 2 0 0 Sample output: 49 26 48 32 now I know that it is an advance version of 0/1 knapsack problem where along with maximum cost we also have to find minimum weight that is less than a a given weight and have maximum cost. so I have used dp to solve this problem but still get a wrong awnser on submission while it is perfectly fine with given test cases. My code is typedef vector<int> vi; #define pb push_back #define FOR(i,n) for(int i=0;i<n;i++) int main() { //freopen("input.txt","r",stdin); while(1) { int W,n; cin>>W>>n; if(W==0 && n==0) break; int K[n+1][W+1]; vi val,wt; FOR(i,n) { int x,y; cin>>x>>y; wt.pb(x); val.pb(y); } FOR(i,n+1) { FOR(w,W+1) { if(i==0 || w==0) { K[i][w]=0; } else if (wt[i-1] <= w) { if(val[i-1] + K[i-1][w-wt[i-1]]>=K[i-1][w]) { K[i][w]=val[i-1] + K[i-1][w-wt[i-1]]; } else { K[i][w]=K[i-1][w]; } } else { K[i][w] = K[i-1][w]; } } } int a1=K[n][W],a2; for(int j=0;j<W;j++) { if(K[n][j]==a1) { a2=j; break; } } cout<<a2<<" "<<a1<<"\n"; } return 0; } Could anyone suggest what am I missing??

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  • Linux Kernel crash mutex_lock_slowpath "blocked for more than 120 seconds". What to do?

    - by Roddick
    I have out-of-the box Debian Lenny with non-custom kernel 2.6.26-2-amd64. Brand new server that is used to 5% of it's potential, CPU and Disk-wise. Meaning it probably not crashing because of overload. every few days it freezes with hundreds of these messages in console log: : [284847.828428] INFO: task apache2:12473 blocked for more than 120 seconds. : [284847.868468] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. : [284847.912759] apache2 D ffff8101bc6b7ab0 0 12473 14358 : [284847.912763] ffff810160d5bc50 0000000000000082 ffff8101c0002e40 0000000000000000 : [284847.912766] ffff8101a7c42950 ffff810327d92810 ffff8101a7c42bd8 0000000400000044 : [284847.912770] ffff8101c0002e40 00000000000612d0 0000000000000000 00000040000612d0 : [284847.912773] Call Trace: : [284847.912786] [<ffffffff80429b0d>] __mutex_lock_slowpath+0x64/0x9b : [284847.912790] [<ffffffff80429972>] mutex_lock+0xa/0xb : [284847.912794] [<ffffffff802a20b9>] do_lookup+0x82/0x1c1 : [284847.912800] [<ffffffff802a4271>] __link_path_walk+0x87a/0xd19 : [284847.912805] [<ffffffff80295844>] kmem_getpages+0x96/0x15f : [284847.912808] [<ffffffff80295fb7>] ____cache_alloc_node+0x6d/0x106 : [284847.912814] [<ffffffff802a4756>] path_walk+0x46/0x8b : [284847.912819] [<ffffffff802a4a82>] do_path_lookup+0x158/0x1cf : [284847.912822] [<ffffffff802a3879>] getname+0x140/0x1a7 : [284847.912827] [<ffffffff802a53f1>] __user_walk_fd+0x37/0x4c : [284847.912831] [<ffffffff8029e381>] vfs_lstat_fd+0x18/0x47 : [284847.912840] [<ffffffff8029e3c9>] sys_newlstat+0x19/0x31 : [284847.912848] [<ffffffff8020beda>] system_call_after_swapgs+0x8a/0x8f Almost all traces has __mutex_lock_slowpath as top-level. Only some has different trace: : [284847.737386] INFO: task apache2:12472 blocked for more than 120 seconds. : [284847.777551] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. : [284847.824881] apache2 D ffff8101bc6b7ab0 0 12472 14358 : [284847.824886] ffff8101b9cc1c50 0000000000000086 ffffffffa0131e0a 0000000000000002 : [284847.824889] ffff8102e7454300 ffff810324c6cad0 ffff8102e7454588 0000000000000000 : [284847.824893] 0000000000000001 0000000000000296 0000000000000003 ffff8101b9cc1c58 : [284847.824896] Call Trace: : [284847.828403] [<ffffffffa0131e0a>] :ext3:__ext3_journal_dirty_metadata+0x1e/0x46 : [284847.828412] [<ffffffff80429b0d>] __mutex_lock_slowpath+0x64/0x9b : [284847.828418] [<ffffffff80429972>] mutex_lock+0xa/0xb : [284847.828421] [<ffffffff802a20b9>] do_lookup+0x82/0x1c1 : [284847.828427] [<ffffffff802a4271>] __link_path_walk+0x87a/0xd19 : [284847.828428] [<ffffffff80271296>] find_lock_page+0x1f/0x8a : [284847.828428] [<ffffffff80273182>] filemap_fault+0x1c2/0x33c : [284847.828428] [<ffffffff802a4756>] path_walk+0x46/0x8b : [284847.828428] [<ffffffff802a4a82>] do_path_lookup+0x158/0x1cf : [284847.828428] [<ffffffff802a3879>] getname+0x140/0x1a7 : [284847.828428] [<ffffffff802a53f1>] __user_walk_fd+0x37/0x4c : [284847.828428] [<ffffffff8029e381>] vfs_lstat_fd+0x18/0x47 : [284847.828428] [<ffffffff8029e3c9>] sys_newlstat+0x19/0x31 : [284847.828428] [<ffffffff8020beda>] system_call_after_swapgs+0x8a/0x8f kernel: [1912668.466347] INFO: task apache2:17984 blocked for more than 120 seconds. [1912668.507035] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. : [1912668.555165] apache2 D ffff8101c5637ba0 0 17984 17282 : [1912668.596752] ffff810166a7dd30 0000000000000086 0000000000000000 ffff810166a7dcd8 : [1912668.643341] ffff8101c563c880 ffff81024505f000 0000000000000002 ffff810166a7dd68 : [1912668.699566] 0000000000000086 00000000000cb1a0 0000000000000000 ffff81017f344d60 : [1912668.744773] Call Trace: : [1912668.761754] [<ffffffff8022a3ed>] pick_next_task_fair+0x6e/0x7a : [1912668.829311] [<ffffffff802be0e2>] bio_alloc_bioset+0x89/0xd9 : [1912668.861930] [<ffffffff8024ac3a>] getnstimeofday+0x39/0x98 : [1912668.897005] [<ffffffff802710f6>] sync_page+0x0/0x41 : [1912668.927868] [<ffffffff80429487>] io_schedule+0x5c/0x9e : [1912668.960286] [<ffffffff80271132>] sync_page+0x3c/0x41 : [1912668.991756] [<ffffffff804295fa>] __wait_on_bit_lock+0x36/0x66 : [1912669.031757] [<ffffffff802710e3>] __lock_page+0x5e/0x64 : [1912669.064191] [<ffffffff802461d3>] wake_bit_function+0x0/0x23 : [1912669.100100] [<ffffffff80281bc5>] handle_mm_fault+0x5e4/0x8de : [1912669.134531] [<ffffffff802461a5>] autoremove_wake_function+0x0/0x2e : [1912669.174623] [<ffffffff802aa108>] fcntl_setlk+0x1cf/0x291 : [1912669.210623] [<ffffffff802461a5>] autoremove_wake_function+0x0/0x2e : [1912669.246923] [<ffffffff802a677f>] sys_fcntl+0x280/0x2f7 After googling for "mutex_lock_slowpath" I can only find the Kernel mailing list discussions that this issue was introduced in some commit. Wthout reference to verison. Discussions as recent as Jan 25, 2011. The Kernel I am using is form Debian Lenny, year ago. What should I do? Is this bug even fixed in kernel? if it's such obvious bug why it happens so rarely? Should I download latest kernel from kernel.org and upgrade? Should I use Debian backports to install new "Approved" kernel? Am I missing something? What to do?

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  • What container type provides better (average) performance than std::map?

    - by Truncheon
    In the following example a std::map structure is filled with 26 values from A - Z (for key) and 0 - 26 for value. The time taken (on my system) to lookup the last entry (10000000 times) is roughly 250 ms for the vector, and 125 ms for the map. (I compiled using release mode, with O3 option turned on for g++ 4.4) But if for some odd reason I wanted better performance than the std::map, what data structures and functions would I need to consider using? I apologize if the answer seems obvious to you, but I haven't had much experience in the performance critical aspects of C++ programming. UPDATE: This example is rather trivial and hides the true complexity of what I'm trying to achieve. My real world project is a simple scripting language that uses a parser, data tree, and interpreter (instead of a VM stack system). I need to use some kind of data structure (perhaps map) to store the variables names created by script programmers. These are likely to be pretty randomly named, so I need a lookup method that can quickly find a particular key within a (probably) fairly large list of names. #include <ctime> #include <map> #include <vector> #include <iostream> struct mystruct { char key; int value; mystruct(char k = 0, int v = 0) : key(k), value(v) { } }; int find(const std::vector<mystruct>& ref, char key) { for (std::vector<mystruct>::const_iterator i = ref.begin(); i != ref.end(); ++i) if (i->key == key) return i->value; return -1; } int main() { std::map<char, int> mymap; std::vector<mystruct> myvec; for (int i = 'a'; i < 'a' + 26; ++i) { mymap[i] = i - 'a'; myvec.push_back(mystruct(i, i - 'a')); } int pre = clock(); for (int i = 0; i < 10000000; ++i) { find(myvec, 'z'); } std::cout << "linear scan: milli " << clock() - pre << "\n"; pre = clock(); for (int i = 0; i < 10000000; ++i) { mymap['z']; } std::cout << "map scan: milli " << clock() - pre << "\n"; return 0; }

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