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• Are there any well-known algorithms or computer models that computer scientists use to predict FIFA

  - by Khnle

  Occasionally I read news articles that mention about some computer models that computer scientists use to predict winners of some sporting events or the odds for betting which I think there must be a mathematical model behind it. I never bothered to think twice even though I am a "pseudo computer scientist" myself. With the 2010 FIFA World Cup just underway, and since I am also a "pseudo football/soccer player" myself, I just started to wonder about these calculations algorithms. For example, I know one factor is determining the strength of opponents, so that a win against a strong opponent can count more than a win against a weak opponent. But it now kind of gets in a circular loop, or at least how does one determine the strength of a team in the first place, before that team can be considered strong or weak? If it's based on a historical data then there's no way that could be accurate, because those players of the past are no longer on the fields so their impact is none (except maybe if they become coaches like Maradona) Anyway, long question short, if you're happen to be working in this field or have some knowledge, please shed some lights.

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• Define 2D array with loops in php

  - by Michael

  I have an array $rows where each element is a row of 15 tab-delimited values. I want to explode $rows into a 2D array $rowData where each row is an array element and each tab-delimited value is assigned to a different array element. I've tried these two methods without success. I know the first one has a coding error but I do not know how to correct it. Any help would be amazing. for ($i=0; $i<count($rows); $i++){ for ($j=0; $j<15; $j++){ $rowData = array([$i] => array (explode(" ", $rows[$j]))); } } foreach ($rows as $value){ $rowData = array( array (explode(" ", $rows[$value]))); }

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• How do I write a writer method for a class variable in Ruby?

  - by tepidsam

  I'm studying Ruby and my brain just froze. In the following code, how would I write the class writer method for 'self.total_people'? I'm trying to 'count' the number of instances of the class 'Person'. class Person attr_accessor :name, :age @@nationalities = ['French', 'American', 'Colombian', 'Japanese', 'Russian', 'Peruvian'] @@current_people = [] @@total_people = 0 def self.nationalities #reader @@nationalities end def self.nationalities=(array=[]) #writer @@nationalities = array end def self.current_people #reader @@current_people end def self.total_people #reader @@total_people end def self.total_people #writer #-----????? end def self.create_with_attributes(name, age) person = self.new(name) person.age = age person.name = name return person end def initialize(name="Bob", age=0) @name = name @age = age puts "A new person has been instantiated." @@total_people =+ 1 @@current_people << self end

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• Indexing affects only the WHERE clause?

  - by andre matos

  If I have something like: CREATE INDEX idx_myTable_field_x ON myTable USING btree (field_x); SELECT COUNT(field_x), field_x FROM myTable GROUP BY field_x ORDER BY field_x; Imagine myTable with around 500,000 rows and most of field_x values being unique. Since I don't use any WHERE clause, will the created index have any effect at all in my query? Edit: I'm asking this question because I don't get any relevant difference between query-times before and after creating the index; They always take about 8 seconds (which, of course is too much time!). Is this behaviour expected?

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• manipulating 15+ million records in mysql with php?

  - by Nithish

  Hey, I got a user table containing 15+ million records and while doing the registration function i wish to check whether the username already exist. I did indexing for username column and when i run the query "select count(uid) from users where username='webdev'" ,. hmmm, its keep on loading blank screen finally hanged up. I'm doing this in my localhost with php 5 & mysql 5. So suggest me some technique to handle this situation. Is that mongodb is good alternative for handling this process in our local machine? Thanks, Nithish.

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• Would like help with LOGON Trigger

  - by Risho

  I've created a logon trigger in MS SQL that needs to check dm_exec_sessions for a login. This login is the user listed in the connection string and has owner right to the database. If the login is verified, I need it to update a specific table and send an email. So far I've done just the following piece and it disabled my web site. The error I get is: "Logon failed for login 'dev' due to trigger execution. Changed database context to 'mydatabase'. Changed language setting to us_english." Any idea what I did wrong? Thanks, Risho CREATE TRIGGER TDY_Assets_Notification ON ALL SERVER WITH EXECUTE AS 'dev' FOR LOGON AS BEGIN IF ORIGINAL_LOGIN()='dev' AND (SELECT COUNT(*) FROM sys.dm_exec_sessions WHERE is_user_process = 1 AND original_login_name = 'dev') > 1 UPDATE Assets_TDY SET Suspense = 1, Warning = 1 WHERE (Date_Returned IS NULL) AND (GETDATE() >= DATEADD(day, 3, Date_Return)) END

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• Xcode automatically converts the object to NSArray

  - by Farrukh Javeid

  I have been working on an app and during the development, I am facing a very strange problem. I have a NSMutableArray tempSortedArray, which is full of objects of Store types. All the objects are valid as I can see them in my GUI, the problem arises when I iterate through the array, at index 90, which can be generally anyone, the XCode converts the Store object to NSMutableArray object. Any idea, why this is happening. This is the code to check out what I am doing: NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"cashBack" ascending:NO]; NSArray *sortDescriptors = [NSArray arrayWithObject:sortDescriptor]; NSArray *sortedArray = [storesArray sortedArrayUsingDescriptors:sortDescriptors]; for (int i = 0; i < [tempSortedArray count]; i++) { Store *currentStore = [tempSortedArray objectAtIndex:i]; NSLog(@"store class: %@", [currentStore.class description]); if (currentStore.cashBackTypeString != (id)[NSNull null]) { //do whatever is required to do here }

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• LINQ - if condition

  - by ile

  In code, the commented part is what I need to solve... Is there a way to write such query in LINQ? I need this because I will need sorting based on Status. var result = ( from contact in db.Contacts join user in db.Users on contact.CreatedByUserID equals user.UserID join deal in db.Deals on contact.ContactID equals deal.ContactID into deals orderby contact.ContactID descending select new ContactListView { ContactID = contact.ContactID, FirstName = contact.FirstName, LastName = contact.LastName, Email = contact.Email, Deals = deals.Count(), EstValue = deals.Sum(e => e.EstValue), SalesAgent = user.FirstName + " " + user.LastName, Tasks = 7, // This is critical part if(Deals == 0) Status = "Prospect"; else Status = "Client"; // End of critical part... }) .OrderBy(filterQuery.OrderBy + " " + filterQuery.OrderType) .Where(filterQuery.Status);

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• problem reading a csv file in python

  - by Hossein

  Hi, I am trying to read a very simple but somehow large(800Mb) csv file using the csv library in python. The delimiter is a single tab and each line consists of some numbers. Each line is a record, and I have 20681 rows in my file. I had some problems during my calculations using this file,it always stops at a certain row. I got suspicious about the number of rows in the file.I used the code below to count the number of row in this file: tfdf_Reader = csv.reader(open('v2-host_tfdf_en.txt'),delimiter=' ') c = 0 for row in tfdf_Reader: c = c + 1 print c To my surprise c is printed with the value of 61722!!! Why is this happening? What am I doing wrong?

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• Problem with DataGrid_CellFormatting event to set default value

  - by Royson

  Hi, I have created an applicationto display list of files. it also provide user interface for adding new column to a gridview. DataGridViewTextBoxColumn txtBoxColumn = new DataGridViewTextBoxColumn(); txtBoxColumn.Name = columnName; txtBoxColumn.HeaderText = columnName; g_dataGridView.Columns.Add(txtBoxColumn); User will create some custom type column therefore i am adding column directly to grid. I am also able to set its default value before adding for this i am using DataGrid_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e) { if (colIndexWithDefaultValue.Count > 0) { if (colIndexWithDefaultValue.Contains(e.ColumnIndex)) { g_dataGridView.Rows[e.RowIndex].Cells[e.ColumnIndex].Value = colIndexWithDefaultValue[e.ColumnIndex]; } } } where colIndexWithDefaultValue is list of columns with its default value. It is able to show newly created column with default value. But values are getting set for currently visible rows. To set value for all rows i have to do scrolling. So, how do i overcome this problem...

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• Split text by whitespaces

  - by sterh

  Hi to all. I have text file with some text information and i need to split this text at spaces and all word push into List. I make so: QStringList list = line.split(" "); for (int i = 0; i < list.count(); i++){ table.push_back(list[i]); this->ui->textEdit->setText(list[i]); } In line i have my text. But when i test this code i get all text, but not by the word. Thank you.

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• Even lighter than SQLite

  - by Richard Fabian

  I've been looking for a C++ SQL library implementation that is simple to hook in like SQLite, but faster and smaller. My projects are in games development and there's definitely a cutoff point between needing to pass the ACID test and wanting some extreme performance. I'm willing to move away from SQL string style queries, allowing it to be code driven, but I haven't found anything out there that provides SQL like flexibility while also preferring performance over the ACID test. I don't want to go reinventing the wheel, and the idea of implementing an SQL library on my own is quite daunting, even if it's only going to be simple subset of all the calls you could make. I need the basic commands (SELECT, MODIFY, DELETE, INSERT, with JOIN, and WHERE), not data operations (like sorting, min, max, count) and don't need the database to be atomic, or even enforce consistency (I can use a real SQL service while I'm testing and debugging).

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• Show data relationship in gridview with dropdownlist or similar?

  - by Anders Svensson

  I have data coming from two tables with a foreign key relationship - one User table containing users of the web application, and one Page table containing details about pages visited by each user. I would like to be able to view these data in a gridview or the like on a page. It's easy enough to just show the User table data like so (I'm using the Entity Framework and LINQ): UserDBEntities context = new UserDBEntities(); GridView1.DataSource = from user in context.UserSet select new { user.Ip, user.Count, user.Description, user.Referer }; GridView1.DataBind(); But how can I show the Page details? I'm not bent on any particular way of showing it, but the only idea I've been able to come up with is to have a dropdown list for each user in a column. But I can't figure out how to get the page data into such a dropdown list. The tables are associated with the primary/foreign key UserID. Any ideas would be welcome (dropdownlist solution or other)!

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• Any ideas why this wont print out

  - by stan

  Revising for php and cant seem to get this to print the values out that i want Any ideas? Thanks <form action="revision.php" method="GET"> <input type=“text” name=“number[]”/> <input type=“text” name=“number[]”/> <input type=“text” name=“number[]”/> <input type=“text” name=“number[]”/> <input type=“text” name=“number[]”/> <input type="Submit" name="Calcuate"/> </form> <?php if(isset($_GET['number'])){ $amount = count($number); for($i=0; $i < $amount; $i++){ echo $number[$i]; } } ?>

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• Improve SQL strategy - denormalize in object-children-images case

  - by fesja

  Hi, I have a Tour object which has many Place objects. For the list of tours, I want to show some info of the tour, the number of places of the tour, and three Place's images. Right one my SQL queries are (i'm using Doctrine with Symfony on MySQL) get Tour get Tour 1 places get Tour 2 places get Tour 3 places ... get Tour n places If I have a three Tour list, it's not so bad; but I'm sure it can get bad if I do a 10-20 tour-list. So, thinking on how to improve the queries I've thought of several measures: Having a place count cache Storing the urls of three images on a new tour field. The problem with 2. is that if I change the image, I have to check all the tours to update that image for another one. What solution do you think is best to scale the system in a near future? Any other suggestion. thanks!

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• Why is std::tr1::shared_ptr<>.reset() so expensive?

  - by Paul Oyster

  Profiling some code that heavily uses shared_ptrs, I discovered that reset() was surprisingly expensive. For example: struct Test { int i; Test() { this->i = 0; } Test(int i) { this->i = i; } } ; ... auto t = make_shared<Test>(1); ... t.reset(somePointerToATestObject); Tracing the reset() in the last line (under VC++ 2010), I discovered that it creates a new reference-counting object. Is there a cheaper way, that reuses the existing ref-count and does not bother the heap?

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• LINQ How to force query to materialize?

  - by Bobb

  Say I have simple LINQ extenstion: var filtered = data.Where(i => i.Count > 0); I know that this will not evaluated unless I start to use filtered i.e. foreach(DataItem i in filtered) ... However I need to create cloned version of data and release data as soon as possible. data can be changed in other thread so I want to get immediate snapshot of it. How can I force filtered to be evaluated immediately?

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• Stuck on solving the Minimal Spanning Tree problem.

  - by kunjaan

  I have reduced my problem to finding the minimal spanning tree in the graph. But I want to have one more constraint which is that the total degree for each vertex shouldnt exceed a certain constant factor. How do I model my problem? Is MST the wrong path? Do you know any algorithms that will help me? One more problem: My graph has duplicate edge weights so is there a way to count the number of unique MSTs? Are there algorithms that do this? Thank You. Edit: By degree, I mean the total number of edges connecting the vertex. By duplicate edge weight I mean that two edges have the same weight.

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• Getting Popular Topics on a Custom Made Forum

  - by Navarr

  For this website we're working on, we're trying to get the most popular topics (based on how many posts have been made in them within the last 24 hours). We have a medium to large based forum, and the current MySQL query looks like this: SELECT `forums_topics`.*, ( SELECT COUNT(`id`) FROM `forums_posts` WHERE `postdate` > (UNIX_TIMESTAMP()-60*60*24) AND `topicid`=`forums_topics`.`id` ) AS `trendy_threads` FROM `forums_topics` WHERE `deleted`=0 ORDER BY `trendy_threads` DESC,`postdate` DESC LIMIT 3 This unfortunately causes an SQL timeout with just one query and Error 500's. How can we get this information as quickly and as efficiently as possible?

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• Confusion using MYSQLI

  - by user1020069

  I just started using mysqli API for PHP. Apparently, every time an object of the class MYSQLI is instantiated, it can setup a connection to the database as it connects to the server unlike mysql_connect, which connects to the server first and then you are required to specify the database to query. Now this is a good problem if the db exists, in my case, the db does not exist on the first ever connection to the server/execution of the problem, hence I must connect without specifying the database, which is fine, since the msyqli constructor does not make this database mandatory. My challenge is essentially, how do I check if the database exists before attempting the first connection. The only way to really do this would be to establish a conection to the server and then use the result of the following query to gauge if the database exists: SELECT COUNT(*) AS `exists` FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMATA.SCHEMA_NAME="dbname" ; If this returns true, then the database exists, but now the challenge is how do I get the mysqli object to query this database rather than having to prefix the name of the database in the query. Thanks much

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• Can't seem to be able to set ListViewItem.imageIndex

  - by TKL

  I have been scratching my head with this error for at least an hour, what the heck is wrong here? In a loop: if (selectedItems[x].ImageIndex == 3) { List<ListViewItem> dupes = CP.listCache.FindAll(delegate(ListViewItem item) { return item.Text == selectedItems[x].Text; }); if (dupes != null && dupes.Count == 1) dupes[0].ImageIndex = 0; } I can access the imageIndex, but not set it. ArgumentOutOfRange exception occurs.

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• 3-clique counting in a graph

  - by Legend

  I am operating on a (not so) large graph having about 380K edges. I wrote a program to count the number of 3-cliques in the graph. A quick example: List of edges: A - B B - C C - A C - D List of cliques: A - B - C A 3-clique is nothing but a triangle in a graph. Currently, I am doing this using PHP+MySQL. As expected, it is not fast enough. Is there a way to do this in pure MySQL? (perhaps a way to insert all 3-cliques into a table?)

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• C++ shifting bits

  - by Bobby

  I am new to shifting bits, but I am trying to debug the following snippet: if (!(strcmp(arr[i].GetValType(), "f64"))) { dem_content_buff[BytFldPos] = tmp_data; dem_content_buff[BytFldPos + 1] = tmp_data >> 8; dem_content_buff[BytFldPos + 2] = tmp_data >> 16; dem_content_buff[BytFldPos + 3] = tmp_data >> 24; dem_content_buff[BytFldPos + 4] = tmp_data >> 32; dem_content_buff[BytFldPos + 5] = tmp_data >> 40; dem_content_buff[BytFldPos + 6] = tmp_data >> 48; dem_content_buff[BytFldPos + 7] = tmp_data >> 56; } I am getting a warning saying the lines with "32" to "56" have a shift count that is too large. The "f64" in the predicate just means that the data should be 64bit data. How should this be done?

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• Copy method optimization in compilers

  - by Dženan

  Hi All! I have the following code: void Stack::operator =(Stack &rhs) { //do the actual copying } Stack::Stack(Stack &rhs) //copy-constructor { top=NULL; //initialize this as an empty stack (which it is) *this=rhs; //invoke assignment operator } Stack& Stack::CopyStack() { return *this; //this statement will invoke copy contructor } It is being used like this: unsigned Stack::count() { unsigned c=0; Stack copy=CopyStack(); while (!copy.empty()) { copy.pop(); c++; } return c; } Removing reference symbol from declaration of CopyStack (returning a copy instead of reference) makes no difference in visual studio 2008 (with respect to number of times copying is invoked). I guess it gets optimized away - normally it should first make a copy for the return value, then call assignment operator once more to assign it to variable sc. What is your experience with this sort of optimization in different compilers? Regards, Dženan

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• How to create unique user key

  - by Grayson Mitchell

  Scenario: I have a fairly generic table (Data), that has an identity column. The data in this table is grouped (lets say by city). The users need an identifier in order for printing on paper forms, etc. The users can only access their cites data, so if they use the identity column for this purpose they will see odd numbers (e.g. a 'New York' user might see 1,37,2028... as the listed keys. Idealy they would see 1,2,3... (or something similar) The problem of course is concurrency, this being a web application you can't just have something like: UserId = Select Count(*)+1 from Data Where City='New York' Has anyone come up with any cunning ways around this problem?

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