interpret order - Page 195

How to eliminate tearing from animation?

- by MusiGenesis

I'm running an animation in a WinForms app at 18.66666... frames per second (it's synced with music at 140 BPM, which is why the frame rate is weird). Each cel of the animation is pre-calculated, and the animation is driven by a high-resolution multimedia timer. The animation itself is smooth, but I am seeing a significant amount of "tearing", or artifacts that result from cels being caught partway through a screen refresh. When I take the set of cels rendered by my program and write them out to an AVI file, and then play the AVI file in Windows Media Player, I do not see any tearing at all. I assume that WMP plays the file smoothly because it uses DirectX (or something else) and is able to synchronize the rendering with the screen's refresh activity. It's not changing the frame rate, as the animation stays in sync with the audio. Is this why WMP is able to render the animation without tearing, or am I missing something? Is there any way I can use DirectX (or something else) in order to enable my program to be aware of where the current scan line is, and if so, is there any way I can use that information to eliminate tearing without actually using DirectX for displaying the cels? Or do I have to fully use DirectX for rendering in order to deal with this problem? Update: forgot a detail. My app renders each cell onto a PictureBox using Graphics.DrawImage. Is this significantly slower than using BitBlt, such that I might eliminate at least some of the tearing by using BitBlt?

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SQL UNION ALL with a INNER JOIN

- by kOhm

I'm looking for the best way to display all rows from two tables while joining first by one field (dwg) then where applicable a 2nd join on part. Table1 data consists of schematics(dwg) along with a list of parts required to build the item depicted in the drawing. Table2 consists of data about the actual parts ordered to build the schematic. Some parts in table2 are a combination of parts in table1 (ex: foo and bar in table1 were ordered as foobar in table2). I can display all rows in both tables with UNION ALL, but this doesn't join on both the dwg and part fields. I looked at FULL OUTER JOIN also, but I haven't figured out how to join first by dwg, then by part. Here is an example of the data. table1 table2 dwg part qty order dwg part qty ----- ----- ----- ----- ----- ----- ----- 123 foo 1 ord1 123 foobar 1 123 bar 1 ord1 123 bracket 2 123 widget 2 ord2 123 screw 4 123 bracket 4 ord2 123 nut 4 456 foo 1 ord2 123 widget 2 ord2 123 bracket 2 ord3 456 foo 1 Desired output: The goal is to create a view that provides visibility to all parts in table1 and the associated orders in table2 (including those parts that appear in one but not the other table) so that I can see all the drawing parts in table1 and the associated records in table2 along with records in table2 where the part wasn't in table1. part_request_order_report dwg part qty order part qty ----- ----- ----- ------ ----- ----- 123 foo 1 123 bar 1 123 widget 2 ord2 widget 2 123 bracket 4 ord1 bracket 2 123 bracket 4 ord2 bracket 2 123 ord1 foobar 1 123 ord1 screw 4 123 ord1 nut 4 456 foo 1 ord3 foo 1 Is this possible? Or am I better off iterating through the data to build the report table? Thanks in advance.

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Which database I can used and relationship in it ??

- by mimo-hamad

My projece make me confused which I didn't find clear things that make me understand the required database and the relationships in it So, would a super one help me to solve it ?!! ;D this is required: 1) Model the data stored in the database (Identify the entities, roles, relationships, constraints, etc.) 2) Write the Oracle commands to create the database, find appropriate data, and populate the database 3) Write five different queries on your database, using the SELECT/FROM/WHERE construct provided in SQL. Your five queries should illustrate several different aspects of database querying, such as: a. Queries over more than one relation (by listing more than one relation in the FROM clause) b. Queries involving aggregate functions, such as SUM, COUNT, and AVG c. Queries involving complicated selects and joins d. Queries involving GROUP BY, HAVING or other similar functions. e. Queries that require the use of the DISTINCT keyword. And this the condition that we need to determine it to solve the required Q's above : 5) It is desired to develop an Internet membership club to buy products at special prices online. To join, new members must be referred by another existing member of the club. The system will keep the following information for each member: The member ID, referring member, birth date, member name, address, phone, mobile, credit card type, number and expiration date. The items are always shipped to the member's address noted in the membership application. The shipping fees will differ for each order.For each item to be requested, the member will select an item from a long list of possible items. For each item in the database, we store an item ID, an item name, description, and list price. The list price will be different from the actual sale price. The available quantity and the back-ordered quantity (the back-ordered quantity is the quantity on-order by the club from its suppliers) is also noted

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How to approach parallel processing of messages?

- by Dan

I am redesigning the messaging system for my app to use intel threading building blocks and am stumped trying to decide between two possible approaches. Basically, I have a sequence of message objects and for each message type, a sequence of handlers. For each message object, I apply each handler registered for that message objects type. The sequential version would be something like this (pseudocode): for each message in message_sequence <- SEQUENTIAL for each handler in (handler_table for message.type) apply handler to message <- SEQUENTIAL The first approach which I am considering processes the message objects in turn (sequentially) and applies the handlers concurrently. Pros: predictable ordering of messages (ie, we are guaranteed a FIFO processing order) (potentially) lower latency of processing each message Cons: more processing resources available than handlers for a single message type (bad parallelization) bad use of processor cache since message objects need to be copied for each handler to use large overhead for small handlers The pseudocode of this approach would be as follows: for each message in message_sequence <- SEQUENTIAL parallel_for each handler in (handler_table for message.type) apply handler to message <- PARALLEL The second approach is to process the messages in parallel and apply the handlers to each message sequentially. Pros: better use of processor cache (keeps the message object local to all handlers which will use it) small handlers don't impose as much overhead (as long as there are other handlers also to be run) more messages are expected than there are handlers, so the potential for parallelism is greater Cons: Unpredictable ordering - if message A is sent before message B, they may both be processed at the same time, or B may finish processing before all of A's handlers are finished (order is non-deterministic) The pseudocode is as follows: parallel_for each message in message_sequence <- PARALLEL for each handler in (handler_table for message.type) apply handler to message <- SEQUENTIAL The second approach has more advantages than the first, but non-deterministic ordering is a big disadvantage.. Which approach would you choose and why? Are there any other approaches I should consider (besides the obvious third approach: parallel messages and parallel handlers, which has the disadvantages of both and no real redeeming factors as far as I can tell)? Thanks!

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PHP header redirection does not reload <iframe> in IE

- by Marco Demaio

When displaying data from DB usually I'm in this situation I'm in page A.php that shows data from DB, user performs some action (like edit/delete etc) and page B.php is loaded to perform the action, once page B performed the action, it redirects browser to page A, page A is auto reloaded during step (3) therefor it shows an updated situation of the data In order to make page B to redirect to page A i use a simple PHP header("Location: " . "A.php", TRUE, 302); This works well in all situations, except when pages A.php is displaied into an <iframe>: in such a case it does not reload (step 4 does not get done). This seems to happen only in IE7 (don't know about IE8), it works perfectly on FF/Safari. And only when using an <iframe>, if page A.php is not in <iframe> it gest refreshed also in IE7. In order to solve this I simply added a couple of headers in page A.php to set it to not be cached: header("Cache-Control: no-cache, must-revalidate"); // HTTP/1.1 header("Expires: Sat, 26 Jul 1997 05:00:00 GMT"); // Date in the past But I was curious if you might have experienced the same issue too in the past, and if you good give me some advice about this?

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Optimize a MySQL count each duplicate Query

- by Onema

I have the following query That gets the city name, city id, the region name, and a count of duplicate names for that record: SELECT Country_CA.City AS currentCity, Country_CA.CityID, globe_region.region_name, ( SELECT count(Country_CA.City) FROM Country_CA WHERE City LIKE currentCity ) as counter FROM Country_CA LEFT JOIN globe_region ON globe_region.region_id = Country_CA.RegionID AND globe_region.country_code = Country_CA.CountryCode ORDER BY City This example is for Canada, and the cities will be displayed on a dropdown list. There are a few towns in Canada, and in other countries, that have the same names. Therefore I want to know if there is more than one town with the same name region name will be appended to the town name. Region names are found in the globe_region table. Country_CA and globe_region look similar to this (I have changed a few things for visualization purposes) CREATE TABLE IF NOT EXISTS `Country_CA` ( `City` varchar(75) NOT NULL DEFAULT '', `RegionID` varchar(10) NOT NULL DEFAULT '', `CountryCode` varchar(10) NOT NULL DEFAULT '', `CityID` int(11) NOT NULL DEFAULT '0', PRIMARY KEY (`City`,`RegionID`), KEY `CityID` (`CityID`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8; AND CREATE TABLE IF NOT EXISTS `globe_region` ( `country_code` char(2) COLLATE utf8_unicode_ci NOT NULL, `region_code` char(2) COLLATE utf8_unicode_ci NOT NULL, `region_name` varchar(50) COLLATE utf8_unicode_ci NOT NULL, PRIMARY KEY (`country_code`,`region_code`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci; The query on the top does exactly what I want it to do, but It takes way too long to generate a list for 5000 records. I would like to know if there is a way to optimize the sub-query in order to obtain the same results faster. the results should look like this City CityID region_name counter sheraton 2349269 British Columbia 1 sherbrooke 2349270 Quebec 2 sherbrooke 2349271 Nova Scotia 2 shere 2349273 British Columbia 1 sherridon 2349274 Manitoba 1

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Linq to Entities custom ordering via position mapping table

- by Bigfellahull

Hi, I have a news table and I would like to implement custom ordering. I have done this before via a positional mapping table which has newsIds and a position. I then LEFT OUTER JOIN the position table ON news.newsId = position.itemId with a select case statement CASE WHEN [position] IS NULL THEN 9999 ELSE [position] END and order by position asc, articleDate desc. Now I am trying to do the same with Linq to Entities. I have set up my tables with a PK, FK relationship so that my News object has an Entity Collection of positions. Now comes the bit I can't work out. How to implement the LEFT OUTER JOIN. I have so far: var query = SelectMany (n => n.Positions, (n, s) => new { n, s }) .OrderBy(x => x.s.position) .ThenByDescending(x => x.n.articleDate) .Select(x => x.n); This kinda works. However this uses a INNER JOIN so not what I am after. I had another idea: ret = ret.OrderBy(n => n.ShufflePositions.Select(s => s.position)); However I get the error DbSortClause expressions must have a type that is order comparable. I also tried ret = ret.GroupJoin(tse.ShufflePositions, n => n.id, s => s.itemId, (n, s) => new { n, s }) .OrderBy(x => x.s.Select(z => z.position)) .ThenByDescending(x => x.n.articleDate) .Select(x => x.n); but I get the same error! If anyone can help me out, it would be much appreciated!

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How to properly translate the "var" result of a lambda expression to a concrete type?

- by CrimsonX

So I'm trying to learn more about lambda expressions. I read this question on stackoverflow, concurred with the chosen answer, and have attempted to implement the algorithm using a console app in C# using a simple LINQ expression. My question is: how do I translate the "var result" of the lambda expression into a usable object that I can then print the result? I would also appreciate an in-depth explanation of what is happening when I declare the outer => outer.Value.Frequency (I've read numerous explanations of lambda expressions but additional clarification would help) C# //Input : {5, 13, 6, 5, 13, 7, 8, 6, 5} //Output : {5, 5, 5, 13, 13, 6, 6, 7, 8} //The question is to arrange the numbers in the array in decreasing order of their frequency, preserving the order of their occurrence. //If there is a tie, like in this example between 13 and 6, then the number occurring first in the input array would come first in the output array. List<int> input = new List<int>(); input.Add(5); input.Add(13); input.Add(6); input.Add(5); input.Add(13); input.Add(7); input.Add(8); input.Add(6); input.Add(5); Dictionary<int, FrequencyAndValue> dictionary = new Dictionary<int, FrequencyAndValue>(); foreach (int number in input) { if (!dictionary.ContainsKey(number)) { dictionary.Add(number, new FrequencyAndValue(1, number) ); } else { dictionary[number].Frequency++; } } var result = dictionary.OrderByDescending(outer => outer.Value.Frequency); // How to translate the result into something I can print??

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CakePHP hasMany relationship with multiple columns

- by Muhammad Yasir

Hi, I am using CakePHP framework to build a web application. The simplest form of my problem is this: I have a users table and a messages table with corresponding models. Messages are sent from a user to another user. So messages table has columns from_id and to_id in it, both referencing to id of users. I am able to link Message model to User model by using $belongsTo but I am unable to link User model with Message model (in reverse direction) by using $hasMany in the same manner. var $hasMany = array( 'From' => array( 'className' => 'Message', 'foreignKey' => 'from_id', 'dependent' => false, 'conditions' => '', 'fields' => '', 'order' => '', 'limit' => '', 'offset' => '', 'exclusive' => '', 'finderQuery' => '', 'counterQuery' => '' ), 'To' => array( 'className' => 'Message', 'foreignKey' => 'to_id', 'dependent' => false, 'conditions' => '', 'fields' => '', 'order' => '', 'limit' => '', 'offset' => '', 'exclusive' => '', 'finderQuery' => '', 'counterQuery' => '' ) ); What can do here? Any ideas? Thanks for any help.

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Matab - Trace contour line between two different points

- by Graham

Hi, I have a set of points represented as a 2 row by n column matrix. These points make up a connected boundary or edge. I require a function that traces this contour from a start point P1 and stop at an end point P2. It also needs to be able trace the contour in a clockwise or anti-clockwise direction. I was wondering if this can be achieved by using some of matlabs functions. I have tried to write my own function but this was riddled with bugs and I have also tried using bwtraceboundary and indexing however this has problematic results as the points within the matrix are not in the order that create the contour. Thank you in advance for any help. Btw, I have included a link to a plot of the set of points. It is half the outline of a hand. The function would ideally trace the contour from ether the red star to the green triangle. Returning the points in order of traversal.

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My SQL query is only returning I need the parent aswell

- by sico87

My sql query is only returning the children of the parent I need it to return the parent as well, public function getNav($cat,$subcat){ //gets all sub categories for a specific category if(!$this->checkValue($cat)) return false; //checks data $query = false; if($cat=='NULL'){ $sql = "SELECT itemID, title, parent, url, description, image FROM p_cat WHERE deleted = 0 AND parent is NULL ORDER BY position;"; $query = $this->db->query($sql) or die($this->db->error); }else{ //die($cat); $sql = "SET @parent = (SELECT c.itemID FROM p_cat c WHERE url = '".$this->sql($cat)."' AND deleted = 0); SELECT c1.itemID, c1.title, c1.parent, c1.url, c1.description, c1.image, (SELECT c2.url FROM p_cat c2 WHERE c2.itemID = c1.parent LIMIT 1) as parentUrl FROM p_cat c1 WHERE c1.deleted = 0 AND c1.parent = @parent ORDER BY c1.position;"; $query = $this->db->multi_query($sql) or die($this->db->error); $this->db->store_result(); $this->db->next_result(); $query = $this->db->store_result(); } return $query; }

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TicTacToe strategic reduction

- by NickLarsen

I decided to write a small program that solves TicTacToe in order to try out the effect of some pruning techniques on a trivial game. The full game tree using minimax to solve it only ends up with 549,946 possible games. With alpha-beta pruning, the number of states required to evaluate was reduced to 18,297. Then I applied a transposition table that brings the number down to 2,592. Now I want to see how low that number can go. The next enhancement I want to apply is a strategic reduction. The basic idea is to combine states that have equivalent strategic value. For instance, on the first move, if X plays first, there is nothing strategically different (assuming your opponent plays optimally) about choosing one corner instead of another. In the same situation, the same is true of the center of the walls of the board, and the center is also significant. By reducing to significant states only, you end up with only 3 states for evaluation on the first move instead of 9. This technique should be very useful since it prunes states near the top of the game tree. This idea came from the GameShrink method created by a group at CMU, only I am trying to avoid writing the general form, and just doing what is needed to apply the technique to TicTacToe. In order to achieve this, I modified my hash function (for the transposition table) to enumerate all strategically equivalent positions (using rotation and flipping functions), and to only return the lowest of the values for each board. Unfortunately now my program thinks X can force a win in 5 moves from an empty board when going first. After a long debugging session, it became apparent to me the program was always returning the move for the lowest strategically significant move (I store the last move in the transposition table as part of my state). Is there a better way I can go about adding this feature, or a simple method for determining the correct move applicable to the current situation with what I have already done?

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SVN 409 conflict on commits and updates

- by bhefny

We have been using SVN for the past year now and when we migrated to an online server we started getting this error: Commit: Commit failed (details follow): File or directory 'x.php' is out of date; try updating resource out of date; try updating CHECKOUT of '/!svn/ver/491/x.php': 409 Conflict (http://svn.example.com) We are currently using SmartSVN 6.5 and we have also tested with RapidSVN & Syncro (but we can't use tortoise as we have a lot of Ubunutu users) at the begining I though this How do you fix an SVN 409 Conflict Error would help, but it didn't we are still facing the same error and it's even more absurd now. the main problem is that after you get the error, you can't shake it of. Updating doesn't solve, reverting doesn't solve. You are just stuck with the error. The only thing that could work is removing the file from SVN and adding your version but that would be against why we are using SVN in the first place This is our apache config (and yes autoversioning is ON) <Location /> DAV svn SVNPath /home/example/svn SVNAutoversioning on AuthType Basic AuthName "Access Restricted" AuthUserFile /home/example/svn-auth-file Require valid-user </Location> <Directory /> <Files ~ "^\.ht"> Order allow,deny Allow from all Satisfy All </Files> <Files ~ "^error_log"> Order allow,deny Allow from all Satisfy All </Files> </Directory> And here are some observation: We don't receive conflicts anymore, we just get this 409 conflict you can somehow avoid the error if you always update before committing When committing a modified file + a newly added file, you get the error. As if the added file incremented the version by one and then you are committing another file with a older version. Please advise, we are about to go insane

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Antlr MismatchedSetException During Interpretation

- by user1646481

I am new to Antlr and I have defined a basic grammar using Antlr 3. The grammar compiles and ANTLRWorks generates the Parser and Lexer code without any problems. The grammar can be seen below: grammar i; @header { package i; } module : 'Module1'| 'Module2'; object : 'I'; objectType : 'Name'; filters : EMPTY | 'WHERE' module; table : module object objectType; STRING : ('a'..'z'|'A'..'Z')+; EMPTY : ' '; The problem is that when I interpret the table Parser I get a MismatchedSetException. This is due to having the EMPTY. As soon as I remove EMPTY from the grammar, the interpretation works. I have looked on the Antlr website and some other examples and the Empty space is ' '. I am not sure what to do. I need this EMPTY. As soon as I change the EMPTY to be the following: EMPTY : ''; instead of: EMPTY : ' '; It actually interprets it. However, I am getting the following Exception: Interpreting... [10:57:23] problem matching token at 1:4 NoViableAltException(' '@[1:1: Tokens : ( T__4 | T__5 | T__6 | T__7 | T__8 | T__9 | T__10 | T__11 | T__12 | T__13 | T__14 | T__15 | T__16 );]) [10:57:23] problem matching token at 1:9 NoViableAltException(' '@[1:1: Tokens : ( T__4 | T__5 | T__6 | T__7 | T__8 | T__9 | T__10 | T__11 | T__12 | T__13 | T__14 | T__15 | T__16 );]) When I take out the EMPTY, there are no problems at all. I hope you can help.

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Silverlight - C# and LINQ - Ordering By Multiple Fields

- by user70192

Hello, I have an ObservableCollection of Task objects. Each Task has the following properties: AssignedTo Category Title AssignedDate I'm giving the user an interface to select which of these fields they was to sort by. In some cases, a user may want to sort by up to three of these properties. How do I dynamically build a LINQ statement that will allow me to sort by the selected fields in either ascending or descending order? Currently, I'm trying the following, but it appears to only sort by the last sort applied: var sortedTasks = from task in tasks select task; if (userWantsToSortByAssignedTo == true) { if (sortByAssignedToDescending == true) sortedTasks = sortedTasks.OrderByDescending(t => t.AssignedTo); else sortedTasks = sortedTasks.OrderBy(t => t.AssignedTo); } if (userWantsToSortByCategory == true) { if (sortByCategoryDescending == true) sortedTasks = sortedTasks.OrderByDescending(t => t.Category); else sortedTasks = sortedTasks.OrderBy(t => t.Category); } Is there an elegant way to dynamicaly append order clauses to a LINQ statement?

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Passing params in rails... Breakthrough in understanding params, aka, the "aha" moment

- by Brian McDonough

I have a simple has_many belongs_to relationship and I want to include the parent object for the view of the belongs_to model and I have had some success, but I want it to work better. class Submission < ActiveRecord::Base belongs_to :user belongs_to :contest end class Contest < ActiveRecord::Base belongs_to :user has_many :submissions, :dependent => :destroy end In the case that works, I pass contest_id to submissions by placing it in the url: <%= link_to 'Submit Contest Entry', new_submission_path(:contest_id => @contest.id), :class => 'btn btn-primary btn-large mleft10' %> So that, combined with a hidden_field: <%= f.hidden_field :contest_id %> And a find_contest method in the controller (called with a before_filter): def find_contest #the next line is giving the error (line 76) @contest = Contest.find(params[:submission][:contest_id]) end Makes it work for submissions/new, but how do I add a find to the controller that just works across more than that one page, like if I want to access in show and index. Right now, I get an error: Started GET "/submissions?contest_id=5" for 127.0.0.1 at 2012-12-01 16:01:45 -0800 Processing by SubmissionsController#index as HTML Parameters: {"contest_id"=>"5"} User Load (0.3ms) SELECT "users".* FROM "users" WHERE "users"."id" = 2 ORDER BY users.created_at DESC LIMIT 1 Completed 500 Internal Server Error in 37ms NoMethodError (undefined method `[]' for nil:NilClass): app/controllers/submissions_controller.rb:76:in `find_contest' [edited] Adding show action for submissions: before_filter :find_contest, :except => [:index, :show, :edit, :update, :destroy] def find_contest @contest = Contest.find(params[:submission][:contest_id]) end def show contest_id = @submission.contest_id @submission = @commentable = Submission.find(params[:id]) @comments = @commentable.comments.order(:created_at).reverse respond_to do |format| format.html # show.html.erb format.json { render :json => @submission } end end

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How to debug problems in Linux kernel module `init()`?

- by Kimvais

I am using remote (k)gdb to debug a problem in a module that causes a panic when loaded e.g. when init() is called. The stack trace just shows that do_one_initcall(mod->init) causes the crash. In order to get the symbol file loaded in the gdb, I need to get the address of the module text section, and to get that I need to get the module loaded. Because the insmod in busybox (1.16.1) doesn't support -m so I'm stuck to grep modulename /proc/modules + adding the offset from nm to figure out the address. So I'm facing a sort a of a chicken and an egg problem here - to be able to debug the module loading, I need to get the module loaded - but in order to get the module loaded, I need to debug the problem... So I am currently thinking about two options - is there a way to get the address information either: by printk() in the module init code by printk() somewhere in the kernel code all this prior to calling the mod->init() - so I could place a breakpoint there, load the symbol file, hit c and see it crash and burn...

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JQuery tablesorter - Second click on column header doesn't resort

- by Jonathan

I'm using tablesorter in on a table I added to a view in django's admin (although I'm not sure this is relevant). I'm extending the html's header: {% block extrahead %} <script type="text/javascript" src="http://code.jquery.com/jquery-1.4.2.js"></script> <script type="text/javascript" src="http://mysite.com/media/tablesorter/jquery.tablesorter.js"></script> <script type="text/javascript"> $(document).ready(function() { $("#myTable").tablesorter(); } ); </script> {% endblock %} When I click on a column header, it sorts the table using this column in descending order - that's ok. When I click the same column header a second time - it does not reorder to ascending order. What's wrong with it? the table's html looks like: <table id="myTable" border="1"> <thead> <tr> <th>column_name_1</th> <th>column_name_2</th> <th>column_name_3</th> </tr> </thead> <tbody> {% for item in extra.items %} <tr> <td>{{ item.0|safe }} </td> <td>{{ item.1|safe }} </td> <td>{{ item.2|safe }} </td> </tr> {% endfor %} </tbody> </table>

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Ad distribution problem: an optimal solution?

- by Mokuchan

I'm asked to find a 2 approximate solution to this problem: You’re consulting for an e-commerce site that receives a large number of visitors each day. For each visitor i, where i € {1, 2 ..... n}, the site has assigned a value v[i], representing the expected revenue that can be obtained from this customer. Each visitor i is shown one of m possible ads A1, A2 ..... An as they enter the site. The site wants a selection of one ad for each customer so that each ad is seen, overall, by a set of customers of reasonably large total weight. Thus, given a selection of one ad for each customer, we will define the spread of this selection to be the minimum, over j = 1, 2 ..... m, of the total weight of all customers who were shown ad Aj. Example Suppose there are six customers with values 3, 4, 12, 2, 4, 6, and there are m = 3 ads. Then, in this instance, one could achieve a spread of 9 by showing ad A1 to customers 1, 2, 4, ad A2 to customer 3, and ad A3 to customers 5 and 6. The ultimate goal is to find a selection of an ad for each customer that maximizes the spread. Unfortunately, this optimization problem is NP-hard (you don’t have to prove this). So instead give a polynomial-time algorithm that approximates the maximum spread within a factor of 2. The solution I found is the following: Order visitors values in descending order Add the next visitor value (i.e. assign the visitor) to the Ad with the current lowest total value Repeat This solution actually seems to always find the optimal solution, or I simply can't find a counterexample. Can you find it? Is this a non-polinomial solution and I just can't see it?

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JoinColumn name not used in sql

- by Vladimir

Hi! I have a problem with mapping many-to-one relationship without exact foreign key constraint set in database. I use OpenJPA implementation with MySql database, but the problem is with generated sql scripts for insert and select statements. I have LegalEntity table which contains RootId column (among others). I also have Address table which has LegalEntityId column which is not nullable, and which should contain values referencing LegalEntity's "RootId" column, but without any database constraint (foreign key) set. Address entity is mapped: @Entity @Table(name="address") public class Address implements Serializable { ... @ManyToOne(fetch=FetchType.LAZY, optional=false) @JoinColumn(referencedColumnName="RootId", name="LegalEntityId", nullable=false, insertable=true, updatable=true, table="LegalEntity") public LegalEntity getLegalEntity() { return this.legalEntity; } } SELECT statement (when fetching LegalEntity's addresses) and INSERT statment are generated: SELECT t0.Id, .., t0.LEGALENTITY_ID FROM address t0 WHERE t0.LEGALENTITY_ID = ? ORDER BY t0.Id DESC [params=(int) 2] INSERT INTO address (..., LEGALENTITY_ID) VALUES (..., ?) [params=..., (int) 2] If I omit table attribute from mentioned statements are generated: SELECT t0.Id, ... FROM address t0 INNER JOIN legalentity t1 ON t0.LegalEntityId = t1.RootId WHERE t1.Id = ? ORDER BY t0.Id DESC [params=(int) 2] INSERT INTO address (...) VALUES (...) [params=...] So, LegalEntityId is not included in any of the statements. Is it possible to have relationship based on such referencing (to column other than primary key, without foreign key in database)? Is there something else missing? Thanks in advance.

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SQL query to get latest record for all distinct items in a table

- by David Buckley

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wsgi django not working

- by MaKo

im installing django, the test for wsgi is ok, but when i point my default file to the django test, it doesnt work, this is the test that works fine: default: /etc/apache2/sites-available/default <VirtualHost *:80> ServerName www.example.com ServerAlias example.com ServerAdmin [email protected] DocumentRoot /var/www <Directory /var/www/documents> Order allow,deny Allow from all </Directory> WSGIScriptAlias / /home/ubuntu/djangoProj/micopiloto/application.wsgi <Directory /home/ubuntu/djangoProj/mysitio/wsgi_handler.py> Order allow,deny Allow from all </Directory> </VirtualHost> application.wsgi:: ~/djangoProj/micopiloto import os import sys sys.path.append('/srv/www/cucus/application') os.environ['PYTHON_EGG_CACHE'] = '/srv/www/cucus/.python-egg' def application(environ, start_response): status = '200 OK' output = 'Hello World!MK SS9 tkt kkk' response_headers = [('Content-type', 'text/plain'), ('Content-Length', str(len(output)))] start_response(status, response_headers) return [output] but if I change the default to point to application_sa.wsgi the django test, it doesnt work :( application_sa.wsgi import os, sys sys.path.append('/home/ubuntu/djangoProj/micopiloto') os.environ['DJANGO_SETTINGS_MODULE'] = 'micopiloto.settings' import django.core.handlers.wsgi application = django.core.handlers.wsgi.WSGIHandler() I restart the apache server every time i change the wsgi to test, so what im i missing? thanks a lot!

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Need to add WHERE condition to query

- by Angel Carlson

I am trying to modify edit_orders.php in Zen Cart. Hoping someone might be able to help me add a condition to a query. I need the queries below to specify that the items selected from TABLE_PRODUCTS_DESCRIPTION and TABLE_CATEGORIES_DESCRIPTION must have a language_id = 1. Would be so grateful for any help you could provide. // ############################################################################ // Get List of All Products // ############################################################################ //$result = zen_db_query("SELECT products_name, p.products_id, x.categories_name, ptc.categories_id FROM " . TABLE_PRODUCTS . " p LEFT JOIN " . TABLE_PRODUCTS_DESCRIPTION . " pd ON pd.products_id=p.products_id LEFT JOIN " . TABLE_PRODUCTS_TO_CATEGORIES . " ptc ON ptc.products_id=p.products_id LEFT JOIN " . TABLE_CATEGORIES_DESCRIPTION . " cd ON cd.categories_id=ptc.categories_id LEFT JOIN " . TABLE_CATEGORIES_DESCRIPTION . " x ON x.categories_id=ptc.categories_id ORDER BY categories_id"); $result = $db -> Execute("SELECT products_name, p.products_id, categories_name, ptc.categories_id FROM " . TABLE_PRODUCTS . " p LEFT JOIN " . TABLE_PRODUCTS_DESCRIPTION . " pd ON pd.products_id=p.products_id LEFT JOIN " . TABLE_PRODUCTS_TO_CATEGORIES . " ptc ON ptc.products_id=p.products_id LEFT JOIN " . TABLE_CATEGORIES_DESCRIPTION . " cd ON cd.categories_id=ptc.categories_id ORDER BY categories_name");

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connecting to secure database from website host

- by jim

Hello all, I've got a requirement to both read and write data via a .net webservice to a sqlserver database that's on a private network. this database is currently accessed via a vpn connection by remote client software (on standard desktop machines) to get latest product prices and to upload product stock sales. I've been tasked with finding a way to centralise this access from a webservice that the clients then access, rather than them using the vpn route to connect directly to the database. My question is related to my .net service's relationship to the sqlserver database. What are the options for connecting to a private network vpn from a domain host in order to achive the functionality of allowing the webservice to both read and write data to the database. For now, I'm not too concerned about the client connectivity and security (tho i appreciate that this will have to be worked out too), I'm really just interested in discovering the options available in order to allow my .net webservice to connect to the private network in as painless and transparent a way as posible. The option of switching the database onto public hosting is not an option, so I have to work with the sdcenario as described above for now, unless there's a compelling rationale presented to do otherwise. thanks all... jim

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MySQL SELECT combining 3 SELECTs INTO 1

- by Martin Tóth

Consider following tables in MySQL database: entries: creator_id INT entry TEXT is_expired BOOL other: creator_id INT entry TEXT userdata: creator_id INT name VARCHAR etc... In entries and other, there can be multiple entries by 1 creator. userdata table is read only for me (placed in other database). I'd like to achieve a following SELECT result: +------------+---------+---------+-------+ | creator_id | entries | expired | other | +------------+---------+---------+-------+ | 10951 | 59 | 55 | 39 | | 70887 | 41 | 34 | 108 | | 88309 | 38 | 20 | 102 | | 94732 | 0 | 0 | 86 | ... where entries is equal to SELECT COUNT(entry) FROM entries GROUP BY creator_id, expired is equal to SELECT COUNT(entry) FROM entries WHERE is_expired = 0 GROUP BY creator_id and other is equal to SELECT COUNT(entry) FROM other GROUP BY creator_id. I need this structure because after doing this SELECT, I need to look for user data in the "userdata" table, which I planned to do with INNER JOIN and select desired columns. I solved this problem with selecting "NULL" into column which does not apply for given SELECT: SELECT creator_id, COUNT(any_entry) as entries, COUNT(expired_entry) as expired, COUNT(other_entry) as other FROM ( SELECT creator_id, entry AS any_entry, NULL AS expired_entry, NULL AS other_enry FROM entries UNION SELECT creator_id, NULL AS any_entry, entry AS expired_entry, NULL AS other_enry FROM entries WHERE is_expired = 1 UNION SELECT creator_id, NULL AS any_entry, NULL AS expired_entry, entry AS other_enry FROM other ) AS tTemp GROUP BY creator_id ORDER BY entries DESC, expired DESC, other DESC ; I've left out the INNER JOIN and selecting other columns from userdata table on purpose (my question being about combining 3 SELECTs into 1). Is my idea valid? = Am I trying to use the right "construction" for this? Are these kind of SELECTs possible without creating an "empty" column? (some kind of JOIN) Should I do it "outside the DB": make 3 SELECTs, make some order in it (let's say python lists/dicts) and then do the additional SELECTs for userdata? Solution for a similar question does not return rows where entries and expired are 0. Thank you for your time.

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