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• Elo rating system: start value

  - by Marco W.

  I've implemented an Elo rating system in a game. There is no limit for the number players. Players can join the game constantly so the number of players probably rises gradually. How the Elo values are exactly calculated isn't important because of this fact: If team A beats team B then A's Elo win equals B's Elo loss. Hence I've got a problem concerning the starting values for my rating system: Should I use the starting value "0" for every player? The sum of all Elo values would be constant. But since the number of players is increasing there would be some kind of Elo deflation, wouldn't it? Should I use any starting value greater than 0? In this case, the sum of all Elo values would constantly increase. So there could be an Elo inflation. The problem: Elo points lose value but the starting value keeps always the same. What should I do? Can you help me? Thanks in advance!

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• How do I tell NHibernate to load a component as not null even when all its properties are null?

  - by SharePoint Newbie

  Hi, I have a Date class which wraps over the DateTime? class (aids in mocking DateTime.Now, our domain ,etc). The Date class class only has one protected property : DateTime? date public class Date { protected DateTime? date; } // mapping in hbm <component name="CompletedOn"> <property column="StartedOn" name="date" access="field" not-null="false" /> </component> From the nhibernate docs: Like all value types, components do not support shared references. The null value semantics of a component are ad hoc. When reloading the containing object, NHibernate will assume that if all component columns are null, then the entire component is null. This should be okay for most purposes. Can I override this behaviour? I want my Date class to be instantiated even if date is null. Thanks,

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• Hibernate multi column discriminator

  - by shikarishambu

  I have a single lookup table that manages all lookups - legacy and new lookup table structure is context,name, code, value context is either legacy or new name is the name of the lookup - state, status etc...for example code is the code and value is the value associated with the code Is there a way to specify multiple columns as discriminators so that I can get all legacy state code/values or all new status code/values. Is there a different way to do this if discriminators cannot do it? <class name="com.company.domain.Lookup"> <id name="Id" column="id" type="big_integer"> <generator class="org.hibernate.id.TableHiLoGenerator" /> </id> <discriminator column="context" insert="false" /> <property name="code" type="string"/> <property name="value" type="string"/> <property name="desc" type="string"/> <subclass name="com.company.domain.LegacyLookup" discriminator-value="legacy">

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• Another dynamic memory allocation bug.

  - by m4design

  I'm trying to allocate memory for a multidimensional array (8 rows, 3 columns). Here's the code for the allocation (I'm sure the error is clear for you) char **ptr = (char **) malloc( sizeof(char) * 8); for (i = 0; i < 3; i++) ptr[i] = (char *) malloc( sizeof(char) * 3); The crash happens when I reference this: ptr[3][0]; Unhandled exception at 0x0135144d in xxxx.exe: 0xC0000005: Access violation writing location 0xabababab. Are there any recommended references/readings for this kind of subject? Thanks.

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• Efficient persistent storage for simple id to table of values map for java

  - by wds

  I need to store some data that follows the simple pattern of mapping an "id" to a full table (with multiple rows) of several columns (i.e. some integer values [u, v, w]). The size of one of these tables would be a couple of KB. Basically what I need is to store a persistent cache of some intermediary results. This could quite easily be implemented as simple sql, but there's a couple of problems, namely I need to compress the size of this structure on disk as much as possible. (because of amount of values I'm storing) Also, it's not transactional, I just need to write once and simply read the contents of the entire table, so a relational DB isn't actually a very good fit. I was wondering if anyone had any good suggestions? For some reason I can't seem to come up with something decent atm. Especially something with an API in java would be nice.

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• Big-O for calculating all routes from GPS data

  - by HH

  A non-critical GPS module use lists because it needs to be modifiable, new routes added, new distances calculated, continuos comparisons. Well so I thought but my team member wrote something I am very hard to get into. His pseudo code int k =0; a[][] <- create mapModuleNearbyDotList -array //CPU O(n) for(j = 1 to n) // O(nlog(m)) for(i =1 to n) for(k = 1 to n) if(dot is nearby) adj[i][j]=min(adj[i][j], adj[i][k] + adj[k][j]); His ideas transformations of lists to tables His worst case time complexity is O(n^3), where n is number of elements in his so-called table. Exception to the last point with Finite structure: O(mlog(n)) where n is number of vertices and m is the amount of neighbour vertices. Questions about his ideas why to waste resources to transform constantly-modified lists to table? Fast? only point where I to some extent agree but cannot understand the same upper limits n for each for-loops -- perhaps he supposed it circular why does the code take O(mlog(n)) to proceed in time as finite structure? The term finite may be wrong, explicit?

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• Using formLabel in FormPanel for Localization

  - by user1782712

  I am trying to implement Localization within a panel, so to make the fieldLabel accessable from another file I am defining it like this Ext.define('Ext.app.detailForm', { extend: 'Ext.form.Panel', id: 'cscForm', // frame: true, uncomment this to show blue frame background title: 'CSC Details :', //trying cscCode: 'CSC Code', bodyPadding: 5, layout: 'anchor', // Specifies that the items will now be arranged in columns autoScroll: true, //width:1200, //height: 300, collapsible: true, fieldDefaults: { labelAlign: 'left', msgTarget: 'side' }, items: [{ columnWidth: 0.4, xtype: 'container', layout:'anchor', defaults: { labelWidth: 150 }, defaultType: 'textfield', items: [{ xtype: 'container', layout: 'hbox', items:[{ xtype: 'fieldset', columnWidth:1.5, layout: 'column', width:1050, defaultType: 'textfield', defaults: { labelWidth: 150, margin: '3 0 0 10' }, items: [{ fieldLabel: this.cscCode, name: 'CSCCode', width: 500 }, {..... but when I try to render this panel, the formLabel for cscCode does not display, is there some thing which I am doing wrong here? I am basically not able to access "this.cscCode"

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• How do you design a database to allow fast multicolumn searching?

  - by Fletcher Moore

  I am creating a real estate search from RETS data, but this is a general question. When you have a variety of columns that you would like the user to be able to filter their search result by, how do you optimize this? For example, http://www.charlestonrealestateguide.com/listings.php has 16 or so optional filters. Granted, he only has up to 11,000 entries (I have the same data), but I don't imagine the search is performed with just a giant WHERE AND AND AND ... clause. Or is this typically accomplished with one giant multicolumn index? Newegg, Amazon, and countless others also have cool & fast filtering systems for large amounts of data. How do they do it? And is there a database optimization reason for the tendency to provide ranges instead of empty inputs, or is that merely for user convenience?

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• finding common prefix of array of strings

  - by bumperbox

  I have an array like this $sports = array( 'Softball - Counties', 'Softball - Eastern', 'Softball - North Harbour', 'Softball - South', 'Softball - Western' ); and i would like to find the longest common part of the string so in this instance, it would be 'Softball - '; I am thinking that I would follow the this process $i = 1; // loop to the length of the first string while ($i < strlen($sports[0]) { // grab the left most part up to i in length $match = substr($sports[0], 0, $i); // loop through all the values in array, and compare if they match foreach ($sports as $sport) { if ($match != substr($sport, 0, $i) { // didn't match, return the part that did match return substr($sport, 0, $i-1); } } // foreach // increase string length $i++; } // while // if you got to here, then all of them must be identical Questions is there a built in function or much simpler way of doing this ? for my 5 line array that is probably fine, but if i were to do several thousand line arrays, there would be a lot of overhead, so i would have to be move calculated with my starting values of $i, eg $i = halfway of string, if it fails, then $i/2 until it works, then increment $i by 1 until we succeed. so that we are doing the least number of comparisons to get a result If there a formula/algorithm out already out there for this kind of problem ? thanks alex

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• Importing a CSV file without headers into SQL 2008

  - by Luiggi

  I want to import a CSV with 4,8M records into a SQL 2008 table. I'm trying to do it with the Management Studio wizard but it keeps trying to recognize a header row which the CSV doesnt have. I don't find any option to skip this and although I specify the columns myself, the wizard still tries to find a header row and doesnt import anything without it. The structure of the CSV is "818180","25529","Dario","Pereyra","Rosario","SF","2010-09-02" I've also tried alternatives like BULK INSERT but then I find out that with BULK INSERT I can't import files with a text qualifier.

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• gridview dropbox

  - by tbischel

  I'm trying to use a GridView to display a list of components in ASP.NET. I'm trying to make it editable at the same time. One of the columns is a string that should be selected out of a list when the user edits the row. So I've tried the following: Convert the BoundField row to an ItemTemplate Add a dropbox to the template window in the gridview bound the selecteditem to the string At this point, I get an error because the list items haven't been set up in the dropbox. So I guess the two things I'm wondering are: How do I assign the items in the dropbox to a dynamically created list of options? How do I make the dropbox only appear when the row is being edited?

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• DataGridView: how to focus the whole row instead of a single cell?

  - by Tomas Sedovic

  I'd like to use the DataGridView control as a list with columns. Sort of like ListView in Details mode but I want to keep the DataGridView flexibility. ListView (with Details view and FullRowSelect enabled) highlights the whole line and shows the focus mark around the whole line: DataGridView (with SelectionMode = FullRowSelect) displays focus mark only around a single cell: So, does anyone know of some (ideally) easy way to make the DataGridView row selection look like the ListView one? I'm not looking for a changed behaviour of the control - I only want it to look the same. Ideally, without messing up with the methods that do the actual painting.

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• How do you store sets in Cassandra?

  - by Ben W

  I'd like to convert this JSON to a data model in Cassandra, where each of the arrays is a set with no duplicates: var data = { "data1": { "100": [1, 2, 3], "200": [3, 4] }, "data2": { "k1", [1], "k2", [4, 5] } } I'd like to query like this: data["data1"]["100"] to retrieve the sets. Anyone know how you might model this in Cassandra? (The only thing I came up with was columns whose name was a set value and the value of the column was an empty string, but that felt wrong.) It's not OK to serialize the sets as JSON or some other string, which would make this much easier. Also, I should note that it's OK to split data1 and data2 into separate ColumnFamilies, it's not necessary that they're keys in the same one.

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• SaaS Multi-tenancy Applications: How is data import/export/backup being implemented?

  - by Mark Redman

  How are applications providing import / export (or backups) of data in SaaS based multi-tenancy applications, particularly single database designs? Imports: Keeping things simple I think basic imports are useful, ie CSV to a spec (or a way of providing a mapping between CSV columns and fields in the database. Exports: In single database designs I have seen XML exports and HTML (basic sitse generated) exports of data? I would assume that XML is a better option? How does one cater for relational data? Would you reference various things within XML and provide documentation of the relationships or let users figurethis out? Are vendors providing an export/backup that can be imported back in/restored? Your comments appreciated.

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• Idioms for a three-state toggle?

  - by Alex Mcp

  I have a table column where each row has one of three states, and the purpose of the row is to offer manipulation AND display of this property with three states. My current development view is to have three tightly packed radio buttons with labels at the head of the columns (and every 50 rows or so) and onClick they send an AJAX request and thar she blows. This is fugly. Is there a standard idiom for a control like this? I'm currently mocking up something similar to the iPhone on/off toggle, but with a "middle" state. Any input would be welcome.

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• How to access properties of Access Database Table using C# ADOX?

  - by Sachin G

  I have created MS Access Database using C# ADOX library. I have created one table with several columns. What I want to achieve is when I insert date in one column, the date format should be YYYY-MM-DD and not MM-DD-YYYY. I know its just display format, but I want to access the property which we set when we open access table in design mode, and for column with date data type, set format as Custom (YYYY-MM-DD). I want this to be set at runtime while creating table only. I wanted to know what should be property name that I should use in order to access and set the format property of column?

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• Export large amount of data from Oracle 10G to SQL Server 2005

  - by uniball

  Dear all, I need to export 100 million data rows (avg row length ~ 100 bytes) from Oracle 10G database table into SQL server (over WAN/VLAN with 6MBits/sec capacity) on a regular basis. So far, these are the options that I have tried and a quick summary. Has anyone tried this before? Are there other better options? Which option would be the best in terms of performance and reliability? The time taken has been calculated using tests on smaller amounts of data and then extrapolating it to estimate the time required. Using data import wizard on the SQL server or SSIS packages to import the data. It will take around 150 hours to complete the task. Using Oracle batch job to spool data into a comma-delimited flat-file. Then using SSIS package to FTP this file to the SQL server and then load directly from the flat-file. The issue here is the size of the flat-file which is expected to run in GBs. Although this option is drastically different, I am even considering the option of using Linked Server to query the Oracle data directly at run-time to avoid bringing in data. Performance is a big problem and I have limited control over the Oracle database in terms of creating table indexes. Regards, Uniball

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• Opening an Excel file in c#

  - by Jan de Jager

  So there are a lot of questions regarding this method on SO, but none seem to answer my question. I firstly had an issue with the connectionstring (although it seems to work in other areas of my code correctly). This was resolved easily. Now the issue is with a simple SELECT query via a OLEDBCommand (Text) that keeps popping up the following error? "SELECT [Opportunity#],[BidManager],[Prob %],[Opportunity_Stage].[Opportunity_Status],[Term],[Sign Date] FROM [Sheet1$];" No value given for one or more required parameters. but their are no parameters???? Checked and double checked the columns names, but to no avail. Also tried removing the special characters from the column names, but still the same exception.

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• Hibernate/JPA DB Schema Generation Best Practices

  - by Bytecode Ninja

  I just wanted to hear the opinion of Hibernate experts about DB schema generation best practices for Hibernate/JPA based projects. Especially: What strategy to use when the project has just started? Is it recommended to let Hibernate automatically generate the schema in this phase or is it better to create the database tables manually from earliest phases of the project? Pretending that throughout the project the schema was being generated using Hibernate, is it better to disable automatic schema generation and manually create the database schema just before the system is released into production? And after the system has been released into production, what is the best practice for maintaining the entity classes and the DB schema (e.g. adding/renaming/updating columns, renaming tables, etc.)? Thanks in advance.

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• Problem with updating multiple rows which are in conflict with unique index

  - by GUZ

  I am using Microsoft SQL Server and I have a master-detail scenario where I need to store the order of details. So in the Detail table I have ID, MasterID, Position and some other columns. There is also a unique index on MasterID and Position. It works OK except one case: when I have some existing details and I change their order. For example when I change a detail on position 3 with a detail on position 2. When I save the detail on position 2 (which in the database has Position equal to 3) SQL Server protests, because the index uniqueness constraint. How to solve this problem in a reasonable way? Thank you in advance Lukasz Glaz

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• Avoiding seasonality assumption for stl() or decompose() in R

  - by user303922

  Hello everybody, I have high frequency commodity price data that I need to analyze. My objective is to not assume any seasonal component and just identify a trend. Here is where I run into problems with R. There are two main functions that I know of to analyze this time series: decompose() and stl(). The problem is that they both take a ts object type with a frequency parameter greater than or equal to 2. Is there some way I can assume a frequency of 1 per unit time and still analyze this time series using R? I'm afraid that if I assume frequency greater than 1 per unit time, and seasonality is calculated using the frequency parameter, then my forecasts are going to depend on that assumption. names(crude.data)=c('Date','Time','Price') names(crude.data) freq = 2 win.graph() plot(crude.data$Time,crude.data$Price, type="l") crude.data$Price = ts(crude.data$Price,frequency=freq) I want frequency to be 1 per unit time but then decompose() and stl() don't work! dim(crude.data$Price) decom = decompose(crude.data$Price) win.graph() plot(decom$random[2:200],type="line") acf(decom$random[freq:length(decom$random-freq)]) Thank you.

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• How can I access the value of a checkbox without a postback?

  - by Starwfanatic

  I have a radgrid controlling access to an application for users. There are two columns, a 'name' column and a checkbox 'access' column representing their current access permission. the checkboxes are populated from a database. I would like the to change the checkboxes to grant or deny access to the users I specify. Since there are alot of users I would like to make multiple changes and use a submit button to write the changes to the database. I do not want to postback with each checkbox change and wait for the page to "blink". My problem is that with the checkbox postback disabled, when I click submit, the value of the checkboxes are not registering the changes I make. I need a way to access the current client-side state of the checkbox or some workaround to accomplish this. Thanks in advance!

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• PHP PDO fetch null

  - by Jacob

  How do you check if a columns value is null? Example code: $db = DBCxn::getCxn(); $sql = "SELECT exercise_id, author_id, submission, result, submission_time, total_rating_votes, total_rating_values FROM submissions LEFT OUTER JOIN submission_ratings ON submissions.exercise_id=submission_ratings.exercise_id WHERE id=:id"; $st = $db->prepare($sql); $st->bindParam(":id", $this->id, PDO::PARAM_INT); $st->execute(); $row = $st->fetch(); if($this->total_rating_votes == null) // this doesn't seem to work even though there is no record in submission_ratings???? { ... }

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• MS Access CrossTab query - across 3 tables

  - by Prembo

  Hi, I have the following 3 tables: 1) Sweetness Table FruitIndex CountryIndex Sweetness 1 1 10 1 2 20 1 3 400 2 1 50 2 2 123 2 3 1 3 1 49 3 2 40 3 3 2 2) Fruit Name Table FruitIndex FruitName 1 Apple 2 Orange 3 Peaches 3) Country Name Table CountryIndex CountryName 1 UnitedStates 2 Canada 3 Mexico I'm trying to perform a CrossTab SQL query to end up with: Fruit\Country UnitedStates Canada Mexico Apple 10 20 400 Orange 50 123 1 Peaches 49 40 2 The challenging part is to label the rows/columns with the relevant names from the Name tables. I can use MS Access to design 2 queries, create the joins the fruit/country names table with the Sweetness table perform crosstab query However I'm having trouble doing this in a single query. I've attempted nesting the 1st query's SQL into the 2nd, but it doesn't seem to work. Unfortunately, my solution needs to be be wholly SQL, as it is an embedded SQL query (cannot rely on query designer in MS Access, etc.). Any help greatly appreciated. Prembo.

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• PostgeSQL: Arrays Data Type with PHP

  - by ArchJ

  I'm working on PostgeSQL with PHP and I know that PosrgeSQL allow columns of a table to be defined as arrays. So let's say I have a table like this: CREATE TABLE sal_emp ( a text ARRAY, b text ARRAY, c text ARRAY, ); These are my arrays: $a = array(aa,bb,cc); $b = array(dd,dd,aa); $c = array(bb,ff,ee); and I want to insert them into respective column each like this: a | b | c -----------+------------+------------ {aa,bb,cc} | {dd,dd,aa} | {bb,ff,ee} Can I insert it this way? $a = implode(',', $a); $b = implode(',', $b); $c = implode(',', $c); $a = array('a' => $a, 'b' => $b, 'c' => $c); pg_insert($dbconn, 'table', $a); Or is there a better way to achieve the same result?

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