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• How to best handle exception to repeating calendar events

  - by blcArmadillo

  I'm working on a project that will require me to implement a calendar. I'm trying to come up with a system that is very flexible: can handle repeating events, exceptions to repeats, etc. I've looked at the schema for applications like iCal, Lotus Notes, and Mozilla to get an idea of how to go about implementing such a system. Currently I'm having trouble deciding what is the best way to handle exceptions to repeating events. I've used databases quite a bit but don't have a ton of experience with really optimizing everything so I'm not sure which method of the two I'm considering would be optimal in terms of overall performance and ability to query/search: Breaking the repeating event. So taking the changing the ending date on the current row for the repeating event, inserting a new row with the exception, and adding another row continuing the old sequence. Simply adding an exception. So adding a new row with some field that indicates it as an override. So here is why I can't decide. Method one will result in a lot more rows since each edit requires 2 extra rows as apposed to only one row by the second method. On the other hand I think the query to find an event would be much simper, and thus possibly faster(?) using the first method. The second method seems like it will require more calculating on the application server since once you get the data you'll have to remove the intersection of the two rows. I know databases are often the bottleneck for websites and while I'm sure a lot of you are thinking either is fine because your project will probably never get large enough for the difference in efficiency to really matter, I'd still like to implement the best solution. So what method would you guys pick, or would you do something completely different? Also, as a side note I'll be using MySQL and PHP. If there is another technology that you think would be better suited for this, especially in the database area, please mention it. Thanks for the advice.

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• Highlighting a Table Correctly Despite rowspan and colspan attributes - WITHOUT jQuery

  - by ScottSEA

  Thanks to some !#$#@ in another department who wrote some crap code, I am unable to use the jQuery library - despite my fervent desire to do so. Their software has already been released into the world, and I have to be compatible. ============================================ I am trying to highlight a table. Desired behavior: Clicking on a cell in the body highlights the row. Clicking on a cell in the head highlights the column. If a column and row are both highlighted, the intersection is highlighted a different color (super-highlight). Clicking on a previously super-highlighted cell turns off the highlights. This behavior is simple enough to do with a basic table, but when rowspans and colspans start rearing their ugly heads, things start to get a little wonky... highlighting cell[5], for instance, no longer works reliably. My thought, in order to speed execution time of the highlighting itself (by changing a class name), is to pre-calculate the 'offsets' of all cells - with a 'colStart' and 'colEnd', 'rowStart' and 'rowEnd' when the page loads and store that in an array somehow. The question: How would YOU implement this functionality? I am fairly rusty at my JavaScript, awfully rudimentary in my programming skills and would benefit greatly from some guidance. Thanks, Scott.

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• Raytraced Shadows Problem

  - by Mat

  Hey There! I've got a problem with shadowrays in my raytracer. Please have a look at the following two pictures 3D sMax: My Raytracer: The scene is lit by a very bright light, shining from the back. It's so bright that there is no gradient in the shading, just either white or dark (due to the overexposure). both images were rendered using 3DStudioMax and both use the exact same geometry, just in one case the normals are interpolated across the triangles. Now consider the red dot on the surface. In the case of the unsmoothed version, it lies in a dark area. this means that the light source is not visible from this triangle, since it's facing away from it. In the smoothed version however, it lies in the lit area, because the interpolated normal would suggest, that the light would be visible at that point (although the actual geometry of the triangle is facing away from the lightsource). My problem now is when raytraced shadows come in. if a shadowray is shot into the scene, from the red dot, to test whether the light-source is visible or not (to determine shadowing), the shadowray will return an intersection, independent of whether normals are interpolated or not (because intersections only depend on the geometry). Therefore the pixel would be shaded dark. 3dsamx is handling the case correctly - the rendered image was generated with Raytraced shadows turned on. However, my own Raytracer runs exactly into this problem when i turn on raytraced shadows (in my raytracer, the point is dark in both cases, because raytraced shadows determine the point lying in the shadow), and i don't know how to solve it. I hope someone knows this problem and how to deal with it.. thanks!

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• Are there any radix/patricia/critbit trees for Python?

  - by Andrew Dalke

  I have about 10,000 words used as a set of inverted indices to about 500,000 documents. Both are normalized so the index is a mapping of integers (word id) to a set of integers (ids of documents which contain the word). My prototype uses Python's set as the obvious data type. When I do a search for a document I find the list of N search words and their corresponding N sets. I want to return the set of documents in the intersection of those N sets. Python's "intersect" method is implemented as a pairwise reduction. I think I can do better with a parallel search of sorted sets, so long as the library offers a fast way to get the next entry after i. I've been looking for something like that for some time. Years ago I wrote PyJudy but I no longer maintain it and I know how much work it would take to get it to a stage where I'm comfortable with it again. I would rather use someone else's well-tested code, and I would like one which supports fast serialization/deserialization. I can't find any, or at least not any with Python bindings. There is avltree which does what I want, but since even the pair-wise set merge take longer than I want, I suspect I want to have all my operations done in C/C++. Do you know of any radix/patricia/critbit tree libraries written as C/C++ extensions for Python? Failing that, what is the most appropriate library which I should wrap? The Judy Array site hasn't been updated in 6 years, with 1.0.5 released in May 2007. (Although it does build cleanly so perhaps It Just Works.)

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• interval overlapping in tsql

  - by Nico

  hi folks, i need to get splited intervals and the number of overlapping intervals, eg basedata: interval A: startTime 08:00, endTime 12:00 interval B: startTime 09:00, endTime 12:00 interval C: startTime 12:00, endTime 16:00 interval D: startTime 13:00, endTime 14:00 now i have a separate interval from 10:00 to 15:00 and have to determine what intervals are intersected at first. result should be something like: 1: 10:00 - 12:00 ( intersecting with interval A ) 2: 10:00 - 12:00 ( intersecting with interval B ) 3: 12:00 - 15:00 ( intersecting with interval C ) 4: 13:00 - 14:00 ( intersecting with interval D ) this part works fine, the following causes the trouble: i need some kind of weighting for parallel intervals. this also means, that it can occur that an interval-intersection must be splitted n times, if it's ( partly ) intersected by another one. in the upper example the expecting result would be: 1: 10:00 - 12:00 -> weightage: 50% 2: 10:00 - 12:00 -> weightage: 50% 3.1: 12:00 - 13:00 -> weightage: 1oo% 3.2: 13:00 - 14:00 -> weightage: 50% 3.3: 14:00 - 15:00 -> weightage: 50% 4: 13:00 - 14:00 -< weightage: 100% the splitting of interval 3 is caused by the intersecting with interval 4 between 13:00 and 14:00. sql-server is ms-sql 2008. thanks for help in advance!

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• Calculating bounding grid coordinates to a user click on google maps/google earth

  - by user170304

  Hello, I have a requirement to calculate the centroid or geodesic midpoint of when a user clicks in between the lat/long grid crossing. The crossing forms a square in most parts of GE and sometimes elongated rectangles. This is due to the shape of the earth of course. I'm looking for a valid mathematical formula that would allow a user to click anywhere in between this grid and then an accurate function (in Javascript or server side code) that would take an assumed grid resolution (say 1km intervals for this discussion) and the input coordinates that should return a centroid coordinate within that graticule grid. To clarify please take a look at the attached image to my google group post: http://google-earth-api.googlegroups.com/web/Picture+5.png?gda=h5oFPz8AAAD315KpovipQeBwdfGpmW3ZhBc9PTADwYa-n193hZ6AItFmHuno63c7phcEXYVuRA6ccyFKn-rNKC-d1pM%5FIdV0&gsc=sz6bbAsAAABBKF7YXWYyc4GmXg-QruHj What I need to be able to do is if a user clicks anywhere in this grid square, I need to find the centroid or center point of that grid intersection/square or at least the bounding grid coordinates (that make the square). If we assume that the grid is UTM standard and has a max resolution of 1km (or make this a parameter), I need to detect the four other points nearby and then calculating the centroid is not as difficult. I welcome any feedback you all may have and appreciate it. I don't have a simple way of letting a user click anywhere on the grid and finding the grid bounding coordinates (making a square of 4 coordinates) or the centroid / midpoint of the graticule grid square necessary. One thought is to use assumptions as much as possible using a reference such as UTM coordinate reference. If I assume that the grid is X degrees wide, can we have a pure javascript function take any input coordinate and return for me the bounding graticule coordinates in Decimal Degrees? Another thought I had was to create the grid in a geo-spatial layer to take any input coordinate and return the nearest centroid of the graticule? Does this make sense? Thanks! Omar

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• Problem Displaying XML in Grid View-newbie

  - by Dean

  I am trying to do something in VisualWebDev 2008 Express that I thought would be simple, but it is not working. I want to display data from an XML file so I added the XMLDataSource to my page, pointed it to the XML file, and then added the GridView and connected it to the datasource. I am getting the following error: GridView - GridView1There was an error rendering the control. The data source for GridView with id 'GridView1' did not have any properties or attributes from which to generate columns. Ensure that your data source has content. Could someone please tell me what I might be doing wrong, TIA Dean A smippet from my XML is as follows: 6019 - Renaissance MS - New School Renaissance MS 7155 Hall Road Fairburn, GA 30213 NS-6019200-LA-01 New School Close-out NS-6019200 0.000000000000000e+000 The construction of the new Renaissance MS will be at the intersection of Jones/Hall Road, in the districts 7th & 9F and Land Lots 117, 143 & 146 of Fulton County, GA. The work includes the construction of the 180,500 square foot building that will house 34 standard classrooms, 12 standard science labs, 20 special purpose classrooms, cafeteria and litchen, gymnasium, media center and administrative offices. The site will also have multi-purpose playfields with track, softball field, tennis courts and basketball/volleyball court. Terry O'Brien Parsons Stevens Wilkinson Stang Newdow Barton Malow -84.62242 33.61497

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• Matlab - Propagate points orthogonally on to the edge of shape boundaries

  - by Graham

  Hi I have a set of points which I want to propagate on to the edge of shape boundary defined by a binary image. The shape boundary is defined by a 1px wide white edge. I also have the coordinates of these points stored in a 2 row by n column matrix. The shape forms a concave boundary with no holes within itself made of around 2500 points. I want to cast a ray from each point from the set of points in an orthogonal direction and detect at which point it intersects the shape boundary at. What would be the best method to do this? Are there some sort of ray tracing algorithms that could be used? Or would it be a case of taking orthogonal unit vector and multiplying it by a scalar and testing after multiplication if the end point of the vector is outside the shape boundary. When the end point of the unit vector is outside the shape, just find the point of intersection? Thank you very much in advance for any help!

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• How to stop the targets generated by schedule:@selector(target:) interval:timeInterval ?

  - by srikanth rongali

  I am using [self schedule:@selector(target:) interval:timeInterval]; for generating bullets in shooting game in cocos2d. In target: I called method targetGenerate to generate for bullet. The enemy generates these bullets. After the player won or enemy won the game the bullets should stop. But, I could not make them stop. I used flags for this. But they did either work. If I set flag1 = 1; for game won. I am using [self schedule:@selector(update:)]; for updating the bullet position to know it hits the player or not ? And I tried like this -(id)init { if( (self = [super init]) ) { //code for enemy [self schedule:@selector(target:) interval:timeInterval]; [self schedule:@selector(update:)]; }return self; } -(void)target:(ccTime)dt { if(flag != 1) [self targetGenerate]; } -(void)targetGenerate { //code for the bullet to generate; CCSprite *bullet = … } -(void)update:(ccTime)dt { //code for to know intersection of bullet and player } But it was not working. How can I make the bullets to disappear after player won the game or enemy won the game ? Thank you.

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• Why do my raytraced spheres have dark lines when lit with multiple light sources?

  - by Curyous

  I have a simple raytracer that only works back up to the first intersection. The scene looks OK with two different light sources, but when both lights are in the scene, there are dark shadows where the lit area from one ends, even if in the middle of a lit area from the other light source (particularly noticeable on the green ball). The transition from the 'area lit by both light sources' to the 'area lit by just one light source' seems to be slightly darker than the 'area lit by just one light source'. The code where I'm adding the lighting effects is: // trace lights for ( int l=0; l<primitives.count; l++) { Primitive* p = [primitives objectAtIndex:l]; if (p.light) { Sphere * lightSource = (Sphere *)p; // calculate diffuse shading Vector3 *light = [[Vector3 alloc] init]; light.x = lightSource.centre.x - intersectionPoint.x; light.y = lightSource.centre.y - intersectionPoint.y; light.z = lightSource.centre.z - intersectionPoint.z; [light normalize]; Vector3 * normal = [[primitiveThatWasHit getNormalAt:intersectionPoint] retain]; if (primitiveThatWasHit.material.diffuse > 0) { float illumination = DOT(normal, light); if (illumination > 0) { float diff = illumination * primitiveThatWasHit.material.diffuse; // add diffuse component to ray color colour.red += diff * primitiveThatWasHit.material.colour.red * lightSource.material.colour.red; colour.blue += diff * primitiveThatWasHit.material.colour.blue * lightSource.material.colour.blue; colour.green += diff * primitiveThatWasHit.material.colour.green * lightSource.material.colour.green; } } [normal release]; [light release]; } } How can I make it look right?

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• Searching a column containing CSV data in a MySQL table for existence of input values

  - by Adarsh R

  Hi, I have a table say, ITEM, in MySQL that stores data as follows: ID FEATURES -------------------- 1 AB,CD,EF,XY 2 PQ,AC,A3,B3 3 AB,CDE 4 AB1,BC3 -------------------- As an input, I will get a CSV string, something like "AB,PQ". I want to get the records that contain AB or PQ. I realized that we've to write a MySQL function to achieve this. So, if we have this magical function MATCH_ANY defined in MySQL that does this, I would then simply execute an SQL as follows: select * from ITEM where MATCH_ANY(FEAURES, "AB,PQ") = 0 The above query would return the records 1, 2 and 3. But I'm running into all sorts of problems while implementing this function as I realized that MySQL doesn't support arrays and there's no simple way to split strings based on a delimiter. Remodeling the table is the last option for me as it involves lot of issues. I might also want to execute queries containing multiple MATCH_ANY functions such as: select * from ITEM where MATCH_ANY(FEATURES, "AB,PQ") = 0 and MATCH_ANY(FEATURES, "CDE") In the above case, we would get an intersection of records (1, 2, 3) and (3) which would be just 3. Any help is deeply appreciated. Thanks

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• How do I improve this design for dealing with intersecting date ranges and resolving date range conf

  - by derdo

  I am working on some code that deals with date ranges. I have pricing activities that have a starting-date and an end-date to set a certain price for that range. There are multiple pricing activities with intersecting date ranges. What I ultimately need is the ability to query valid prices for a date range. I pass in (jan1,jan31) and I get back a list that says jan1--jan10 $4 , jan11--jan19 $3 jan20--jan31 $4. There are priorities between pricing activities. Some type of pricing activities have high priority, so they override other pricing activities and for certain type of pricing activities lowest price wins etc. I currently have a class that holds these pricing activities and keeps a resolved pricing calendar. As I add new pricing activities I update the resolved calendar. As I write more tests/code, it started to get very complicated with all the different cases (pricing activities intersecting in different ways). I am ending up with very complicated code where I am resolving a newly added pricing activity. See AddPricingActivity() method below. Can anybody think of a simpler way to deal with this? Could there be similar code somewhere out there? Public class PricingActivity() { DateTime startDate; DateTime endDate; Double price; Public bool StartsBeforeEndsAfter (PricingActivity pAct) { // pAct covers this pricing activity } Public bool StartsMiddleEndsAfter (PricingActivity pAct){ // early part of pAct Itersects with later part of this pricing activity } //more similar methods to cover all the combinations of intersecting } Public Class PricingActivityList() { List<PricingActivity> activities; SortedDictionary<Date, PricingActivity> resolvedPricingCalendar; Public void AddPricingActivity(PricingActivity pAct) { //update the resolvedCalendar //go over each activity and find intersecting ones //update the resolved calendar correctly //depending on the type of the intersection //this part is getting out of hand….. } }

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• How do I find all paths through a set of given nodes in a DAG?

  - by Hanno Fietz

  I have a list of items (blue nodes below) which are categorized by the users of my application. The categories themselves can be grouped and categorized themselves. The resulting structure can be represented as a Directed Acyclic Graph (DAG) where the items are sinks at the bottom of the graph's topology and the top categories are sources. Note that while some of the categories might be well defined, a lot is going to be user defined and might be very messy. Example: On that structure, I want to perform the following operations: find all items (sinks) below a particular node (all items in Europe) find all paths (if any) that pass through all of a set of n nodes (all items sent via SMTP from example.com) find all nodes that lie below all of a set of nodes (intersection: goyish brown foods) The first seems quite straightforward: start at the node, follow all possible paths to the bottom and collect the items there. However, is there a faster approach? Remembering the nodes I already passed through probably helps avoiding unnecessary repetition, but are there more optimizations? How do I go about the second one? It seems that the first step would be to determine the height of each node in the set, as to determine at which one(s) to start and then find all paths below that which include the rest of the set. But is this the best (or even a good) approach? The graph traversal algorithms listed at Wikipedia all seem to be concerned with either finding a particular node or the shortest or otherwise most effective route between two nodes. I think both is not what I want, or did I just fail to see how this applies to my problem? Where else should I read?

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• Dataset holds a table called "Table", not the table I pass in?

  - by dotnetdev

  Hi, I have the code below: string SQL = "select * from " + TableName; using (DS = new DataSet()) using (SqlDataAdapter adapter = new SqlDataAdapter()) using (SqlConnection sqlconn = new SqlConnection(connectionStringBuilder.ToString())) using (SqlCommand objCommand = new SqlCommand(SQL, sqlconn)) { sqlconn.Open(); adapter.SelectCommand = objCommand; adapter.Fill(DS); } System.Windows.Forms.MessageBox.Show(DS.Tables[0].TableName); return DS; However, every time I run this code, the dataset (DS) is filled with one table called "Table". It does not represent the table name I pass in as the parameter TableName and this parameter does not get mutated so I don't know where the name Table comes from. I'd expect the table to be the same as the tableName parameter I pass in? Any idea why this is not so? EDIT: Important fact: This code needs to return a dataset because I use the dataRelation object in another method, which is dependent on this, and without using a dataset, that method throws an exception. The code for that method is: DataRelation PartToIntersection = new DataRelation("XYZ", this.LoadDataToTable(tableName).Tables[tableName].Columns[0], // Treating the PartStat table as the parent - .N this.LoadDataToTable("PartProducts").Tables["PartProducts"].Columns[0]); // 1 // PartsProducts (intersection) to ProductMaterial DataRelation ProductMaterialToIntersection = new DataRelation("", ds.Tables["ProductMaterial"].Columns[0], ds.Tables["PartsProducts"].Columns[1]); Thanks

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• How can I solve the Log Pile wooden puzzle with a computer program?

  - by craig1410

  Can anyone suggest how to solve the Log Pile wooden puzzle using a computer program? See here to visualise the puzzle: http://www.puzzlethis.co.uk/products/madcow/the_log_pile.htm The picture only shows some of the pieces. The full set of 10 pieces are configured as follows with 1 representing a peg, -1 representing a hole and 0 representing neither a peg nor a hole. -1,1,0,-1,0 1,0,1,0,0 1,-1,1,0,0 -1,-1,0,0,-1 -1,1,0,1,0 0,1,0,0,1 1,0,-1,0,-1 0,-1,0,1,0 0,0,-1,1,-1 1,0,-1,0,0 The pieces can be interlocked in two layers of 5 pieces each with the top layer at 90 degrees to the bottom layer as shown in the above link. I have already created a solution to this problem myself using Java but I feel that it was a clumsy solution and I am interested to see some more sophisticated solutions. Feel free to either suggest a general approach or to provide a working program in the language of your choice. My approach was to use the numeric notation above to create an array of "Logs". I then used a combination/permutation generator to try all possible arrangements of the Logs until a solution was found where all the intersections equated to zero (ie. Peg to Hole, Hole to Peg or Blank to Blank). I used some speed-ups to detect the first failed intersection for a given permutation and move on to the next permutation. I hope you find this as interesting as I have. Thanks, Craig.

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• Finding missing files by checksum

  - by grw

  Hi there, I'm doing a large data migration between two file systems (let's call them F1 and F2) on a Linux system which will necessarily involve copying the data verbatim into a differently-structured hierarchy on F2 and changing the file names. I'd like to write a script to generate a list of files which are in F1 but not in F2, i.e. the ones which weren't copied by the migration script into the new hierarchy, so that I can go back and migrate them manually. Unfortunately for reasons not worth going into, the migration script can't be modified to list files that it doesn't migrate. My question differs from this previously answered one because of the fact that I cannot rely on filenames as a comparison. I know the basic outline of the process would be: Generate a list of checksums for all files, recursing through F1 Do the same for F2 Compare the lists and generate a negative intersection of the checksums, ignoring the file names, to find files which are in F1 but not in F2. I'm kind of stuck getting past that stage, so I'd appreciate any pointers on which tools to use. I think I need to use the 'comm' command to compare the list of file checksums, but since md5sum, sha512sum and the like put the file name next to the checksum, I can't see a way to get it to bring me a useful comparison. Maybe awk is the way to go? I'm using Red Hat Enterprise Linux 5.x. Thanks.

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• Is it possible to achieve MAX(As,Ad) openGL blending?

  - by Jeff B

  I am working on a game where I want to create shadows under a series of sprites on a grid. The shadows are larger than the sprites themselves and the sprites are animated (i.e. move and rotate). I cannot simply render them into the sprite png, or the shadows will overlap adjacent sprites. I also cannot simply put shadows on a lower layer by themselves, because when they overlap, they will create dark bands at their intersection. These sprites are animated, so it is not feasible to render these en masse. Basically, I want the sprites' shadows to blend together such that they max out at a set opacity. Example: I believe this is equivalent to an openGL blending of (Rs,Gs,Bs,Max(As,Ds)), where I don't really care about R,G, and B, as it will always be the same color in src and dst. However, this is not a valid openGL blending mode. Is there an easy way to accomplish this, especially in cocos2d-iphone? I would be able to approximate this by making the shadow sprites opaque, then applying them both to a parent sprite, and making the parent sprite 40% opacity. However, the way cocos2d works, this only sets the opacity of each child to 40%, rather than the combined sprite image, which results in the same stripe.

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• Mysql - Help me alter this query to apply AND logic instead of OR in searching?

  - by sandeepan-nath

  First execute these tables and data dumps :- CREATE TABLE IF NOT EXISTS `Tags` ( `id_tag` int(10) unsigned NOT NULL auto_increment, `tag` varchar(255) default NULL, PRIMARY KEY (`id_tag`), UNIQUE KEY `tag` (`tag`), KEY `id_tag` (`id_tag`), KEY `tag_2` (`tag`), KEY `tag_3` (`tag`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=18 ; INSERT INTO `Tags` (`id_tag`, `tag`) VALUES (1, 'key1'), (2, 'key2'); CREATE TABLE IF NOT EXISTS `Tutors_Tag_Relations` ( `id_tag` int(10) unsigned NOT NULL default '0', `id_tutor` int(10) default NULL, KEY `Tutors_Tag_Relations` (`id_tag`), KEY `id_tutor` (`id_tutor`), KEY `id_tag` (`id_tag`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1; INSERT INTO `Tutors_Tag_Relations` (`id_tag`, `id_tutor`) VALUES (1, 1), (2, 1); The following query finds all the tutors from Tutors_Tag_Relations table which have reference to at least one of the terms "key1" or "key2". SELECT td . * FROM Tutors_Tag_Relations AS td INNER JOIN Tags AS t ON t.id_tag = td.id_tag WHERE t.tag LIKE "%key1%" OR t.tag LIKE "%key2%" Group by td.id_tutor LIMIT 10 Please help me modify this query so that it returns all the tutors from Tutors_Tag_Relations table which have reference to both the terms "key1" and "key2" (AND logic instead of OR logic). Please suggest an optimized query considering huge number of data records (the query should NOT individually fetch two sets of tutors matching each keyword and then find the intersection).

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• Stable/repeatable random sort (MySQL, Rails)

  - by Matt Rogish

  I'd like to paginate through a randomly sorted list of ActiveRecord models (rows from MySQL database). However, this randomization needs to persist on a per-session basis, so that other people that visit the website also receive a random, paginate-able list of records. Let's say there are enough entities (tens of thousands) that storing the randomly sorted ID values in either the session or a cookie is too large, so I must temporarily persist it in some other way (MySQL, file, etc.). Initially I thought I could create a function based on the session ID and the page ID (returning the object IDs for that page) however since the object ID values in MySQL are not sequential (there are gaps), that seemed to fall apart as I was poking at it. The nice thing is that it would require no/minimal storage but the downsides are that it is likely pretty complex to implement and probably CPU intensive. My feeling is I should create an intersection table, something like: random_sorts( sort_id, created_at, user_id NULL if guest) random_sort_items( sort_id, item_id, position ) And then simply store the 'sort_id' in the session. Then, I can paginate the random_sorts WHERE sort_id = n ORDER BY position LIMIT... as usual. Of course, I'd have to put some sort of a reaper in there to remove them after some period of inactivity (based on random_sorts.created_at). Unfortunately, I'd have to invalidate the sort as new objects were created (and/or old objects being removed, although deletion is very rare). And, as load increases the size/performance of this table (even properly indexed) drops. It seems like this ought to be a solved problem but I can't find any rails plugins that do this... Any ideas? Thanks!!

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• How find all overlapping circles from radius of central circle?

  - by roza

  How to do an intersection or overlap query in mongo shell - what circles overlap my search region? Within relate only to the center position but doesn't include radius of the other circles in searched scope. Mongo: # My bad conception: var search = [[30, 30], 10] db.places.find({circle : {"$within" : {"$center" : [search]}}}) Now I can obtain only this circles within central point lies in searched area of circle: Ruby: # field :circle, type: Circle # eg. [ [ 30, 30 ], 10 ] field :radius, type: Integer field :location, :type => Array, :spatial => true spatial_index :location Places.within_circle(location: [ [ 30, 30 ], 10 ]) # {"$query"=>{"location"=>{"$within"=>{"$center"=>[[30, 30], 10]}}} I created example data with additional location (special index) and radius instead circle because circle isn't supported by mongodb geo index: { "_id" : 1, "name" : "a", "circle" : [ [ 5, 5 ], 40 ], "latlng" : [ 5, 5 ], "radius" : 40 } { "_id" : 2, "name" : "b", "circle" : [ [ 10, 10 ], 5 ], "latlng" : [ 10, 10 ], "radius" : 5 } { "_id" : 3, "name" : "c", "circle" : [ [ 20, 20 ], 5 ], "latlng" : [ 20, 20 ], "radius" : 5 } { "_id" : 4, "name" : "d", "circle" : [ [ 30, 30 ], 50 ], "latlng" : [ 30, 30 ], "radius" : 50} { "_id" : 5, "name" : "e", "circle" : [ [ 80, 80 ], 30 ], "latlng" : [ 80, 80 ], "radius" : 30} { "_id" : 6, "name" : "f", "circle" : [ [ 80, 80 ], 20 ], "latlng" : [ 80, 80 ], "radius" : 20} Desired query result: { "_id" : 1, "name" : "a", "circle" : [ [ 5, 5 ], 40 ], "latlng" : [ 5, 5 ], "radius" : 40 } { "_id" : 3, "name" : "c", "circle" : [ [ 20, 20 ], 5 ], "latlng" : [ 20, 20 ], "radius" : 5 } { "_id" : 4, "name" : "d", "circle" : [ [ 30, 30 ], 50 ], "latlng" : [ 30, 30 ], "radius" : 50} { "_id" : 5, "name" : "e", "circle" : [ [ 80, 80 ], 30 ], "latlng" : [ 80, 80 ], "radius" : 30} Solution below assumes that I get all rows and then filter on the ruby side my radius but it returns only: { "_id" : 4, "name" : "d", "circle" : [ [ 30, 30 ], 50 ], "latlng" : [ 30, 30 ], "radius" : 50}

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• Custom collision

  - by bali182

  I was recently assigned to create a siple game using the Corona SDK. The main pillar of the game would be a simple event: the user should put a ball in a basket, and I should be able to handle this event. Here is a picture for better understanding: I successfully managed to create the collision shape for the basket, but i have trouble with the collision of the inside of this basket. My first thought was the following: create a new shape size and position it to fit the "belly" of this basket add it to the physics-world, and listen to the collision. With hybrid drawing it looks like this: But there is a problem: if i add this shape to the physics, it wouldn't let the ball fall into the, basket, it will handle this shape as a solid object as well. So my question is: How could I get this custom object to collide, without blocking the ball to fall through it? I have read a lots of forum post with similar questions but none of them got a proper answer. There must be a way to do this in an elegant way. And one note: Please don't suggest checking the collision manually, with rectangle intersection, because in this simple case it would work, but later I may need to change the shape of the basket, and then it will be useless!

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• How to delete Drawn Line in java?

  - by Jeyjey

  Hello Folks, well this is my code: import javax.swing.; import javax.; import java.awt.; import java.awt.Color; import java.awt.Graphics.; import java.awt.event.*; import javax.swing.UIManager; public class SimpleGUI extends JFrame{ public SimpleGUI(){ this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE) ; } public void go(){ Drawpanel = new Mypanel(); JFrame frame = new JFrame("Chasing Line"); frame.getContentPane().add(BorderLayout.CENTER, Drawpanel); frame.setSize(300,300); frame.setVisible(true); Drawpanel.addMouseMotionListener(new java.awt.event.MouseMotionAdapter() { public void mouseMoved(java.awt.event.MouseEvent evt) { DrawpanelMouseMoved(evt); } }); } public void DrawpanelMouseMoved(java.awt.event.MouseEvent evt) { xpos=evt.getX(); ypos=evt.getY(); System.out.println("Coordinates : X :"+ xpos+"Y: "+ypos); Drawpanel.paintImage(xpos,ypos); } class Mypanel extends JPanel{ public void paintImage(int xpost,int ypost){ Graphics d = getGraphics(); d.setColor(Color.black); d.drawLine(xpost, 0, xpost, this.getHeight()); d.setColor(Color.red); d.drawLine(0, ypost, this.getWidth(),ypost); this.validate(); } } // end the inner class public static void main(String[] args){ try { UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel"); } catch(Exception e) { System.err.println("Look and feel not set"); } SimpleGUI win = new SimpleGUI(); win.go(); } Mypanel Drawpanel; private int xpos=0; private int ypos=0; } // close SimpleGUI class The problem is how can i delete the old lines?, i mea,make only the current x and y lines appear on the screen, make the intersection between both lines "follow" the mouse pointer. thanks for any reply.

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• GLSL Atmospheric Scattering Issue

  - by mtf1200

  I am attempting to use Sean O'Neil's shaders to accomplish atmospheric scattering. For now I am just using SkyFromSpace and GroundFromSpace. The atmosphere works fine but the planet itself is just a giant dark sphere with a white blotch that follows the camera. I think the problem might rest in the "v3Attenuation" variable as when this is removed the sphere is show (albeit without scattering). Here is the vertex shader. Thanks for the time! uniform mat4 g_WorldViewProjectionMatrix; uniform mat4 g_WorldMatrix; uniform vec3 m_v3CameraPos; // The camera's current position uniform vec3 m_v3LightPos; // The direction vector to the light source uniform vec3 m_v3InvWavelength; // 1 / pow(wavelength, 4) for the red, green, and blue channels uniform float m_fCameraHeight; // The camera's current height uniform float m_fCameraHeight2; // fCameraHeight^2 uniform float m_fOuterRadius; // The outer (atmosphere) radius uniform float m_fOuterRadius2; // fOuterRadius^2 uniform float m_fInnerRadius; // The inner (planetary) radius uniform float m_fInnerRadius2; // fInnerRadius^2 uniform float m_fKrESun; // Kr * ESun uniform float m_fKmESun; // Km * ESun uniform float m_fKr4PI; // Kr * 4 * PI uniform float m_fKm4PI; // Km * 4 * PI uniform float m_fScale; // 1 / (fOuterRadius - fInnerRadius) uniform float m_fScaleDepth; // The scale depth (i.e. the altitude at which the atmosphere's average density is found) uniform float m_fScaleOverScaleDepth; // fScale / fScaleDepth attribute vec4 inPosition; vec3 v3ELightPos = vec3(g_WorldMatrix * vec4(m_v3LightPos, 1.0)); vec3 v3ECameraPos= vec3(g_WorldMatrix * vec4(m_v3CameraPos, 1.0)); const int nSamples = 2; const float fSamples = 2.0; varying vec4 color; float scale(float fCos) { float x = 1.0 - fCos; return m_fScaleDepth * exp(-0.00287 + x*(0.459 + x*(3.83 + x*(-6.80 + x*5.25)))); } void main(void) { gl_Position = g_WorldViewProjectionMatrix * inPosition; // Get the ray from the camera to the vertex and its length (which is the far point of the ray passing through the atmosphere) vec3 v3Pos = vec3(g_WorldMatrix * inPosition); vec3 v3Ray = v3Pos - v3ECameraPos; float fFar = length(v3Ray); v3Ray /= fFar; // Calculate the closest intersection of the ray with the outer atmosphere (which is the near point of the ray passing through the atmosphere) float B = 2.0 * dot(m_v3CameraPos, v3Ray); float C = m_fCameraHeight2 - m_fOuterRadius2; float fDet = max(0.0, B*B - 4.0 * C); float fNear = 0.5 * (-B - sqrt(fDet)); // Calculate the ray's starting position, then calculate its scattering offset vec3 v3Start = m_v3CameraPos + v3Ray * fNear; fFar -= fNear; float fDepth = exp((m_fInnerRadius - m_fOuterRadius) / m_fScaleDepth); float fCameraAngle = dot(-v3Ray, v3Pos) / fFar; float fLightAngle = dot(v3ELightPos, v3Pos) / fFar; float fCameraScale = scale(fCameraAngle); float fLightScale = scale(fLightAngle); float fCameraOffset = fDepth*fCameraScale; float fTemp = (fLightScale + fCameraScale); // Initialize the scattering loop variables float fSampleLength = fFar / fSamples; float fScaledLength = fSampleLength * m_fScale; vec3 v3SampleRay = v3Ray * fSampleLength; vec3 v3SamplePoint = v3Start + v3SampleRay * 0.5; // Now loop through the sample rays vec3 v3FrontColor = vec3(0.0, 0.0, 0.0); vec3 v3Attenuate; for(int i=0; i<nSamples; i++) { float fHeight = length(v3SamplePoint); float fDepth = exp(m_fScaleOverScaleDepth * (m_fInnerRadius - fHeight)); float fScatter = fDepth*fTemp - fCameraOffset; v3Attenuate = exp(-fScatter * (m_v3InvWavelength * m_fKr4PI + m_fKm4PI)); v3FrontColor += v3Attenuate * (fDepth * fScaledLength); v3SamplePoint += v3SampleRay; } vec3 first = v3FrontColor * (m_v3InvWavelength * m_fKrESun + m_fKmESun); vec3 secondary = v3Attenuate; color = vec4((first + vec3(0.25,0.25,0.25) * secondary), 1.0); // ^^ that color is passed to the frag shader and is used as the gl_FragColor } Here is also an image of the problem image

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• Joins in single-table queries

  - by Rob Farley

  Tables are only metadata. They don’t store data. I’ve written something about this before, but I want to take a viewpoint of this idea around the topic of joins, especially since it’s the topic for T-SQL Tuesday this month. Hosted this time by Sebastian Meine (@sqlity), who has a whole series on joins this month. Good for him – it’s a great topic. In that last post I discussed the fact that we write queries against tables, but that the engine turns it into a plan against indexes. My point wasn’t simply that a table is actually just a Clustered Index (or heap, which I consider just a special type of index), but that data access always happens against indexes – never tables – and we should be thinking about the indexes (specifically the non-clustered ones) when we write our queries. I described the scenario of looking up phone numbers, and how it never really occurs to us that there is a master list of phone numbers, because we think in terms of the useful non-clustered indexes that the phone companies provide us, but anyway – that’s not the point of this post. So a table is metadata. It stores information about the names of columns and their data types. Nullability, default values, constraints, triggers – these are all things that define the table, but the data isn’t stored in the table. The data that a table describes is stored in a heap or clustered index, but it goes further than this. All the useful data is going to live in non-clustered indexes. Remember this. It’s important. Stop thinking about tables, and start thinking about indexes. So let’s think about tables as indexes. This applies even in a world created by someone else, who doesn’t have the best indexes in mind for you. I’m sure you don’t need me to explain Covering Index bit – the fact that if you don’t have sufficient columns “included” in your index, your query plan will either have to do a Lookup, or else it’ll give up using your index and use one that does have everything it needs (even if that means scanning it). If you haven’t seen that before, drop me a line and I’ll run through it with you. Or go and read a post I did a long while ago about the maths involved in that decision. So – what I’m going to tell you is that a Lookup is a join. When I run SELECT CustomerID FROM Sales.SalesOrderHeader WHERE SalesPersonID = 285; against the AdventureWorks2012 get the following plan: I’m sure you can see the join. Don’t look in the query, it’s not there. But you should be able to see the join in the plan. It’s an Inner Join, implemented by a Nested Loop. It’s pulling data in from the Index Seek, and joining that to the results of a Key Lookup. It clearly is – the QO wouldn’t call it that if it wasn’t really one. It behaves exactly like any other Nested Loop (Inner Join) operator, pulling rows from one side and putting a request in from the other. You wouldn’t have a problem accepting it as a join if the query were slightly different, such as SELECT sod.OrderQty FROM Sales.SalesOrderHeader AS soh JOIN Sales.SalesOrderDetail as sod on sod.SalesOrderID = soh.SalesOrderID WHERE soh.SalesPersonID = 285; Amazingly similar, of course. This one is an explicit join, the first example was just as much a join, even thought you didn’t actually ask for one. You need to consider this when you’re thinking about your queries. But it gets more interesting. Consider this query: SELECT SalesOrderID FROM Sales.SalesOrderHeader WHERE SalesPersonID = 276 AND CustomerID = 29522; It doesn’t look like there’s a join here either, but look at the plan. That’s not some Lookup in action – that’s a proper Merge Join. The Query Optimizer has worked out that it can get the data it needs by looking in two separate indexes and then doing a Merge Join on the data that it gets. Both indexes used are ordered by the column that’s indexed (one on SalesPersonID, one on CustomerID), and then by the CIX key SalesOrderID. Just like when you seek in the phone book to Farley, the Farleys you have are ordered by FirstName, these seek operations return the data ordered by the next field. This order is SalesOrderID, even though you didn’t explicitly put that column in the index definition. The result is two datasets that are ordered by SalesOrderID, making them very mergeable. Another example is the simple query SELECT CustomerID FROM Sales.SalesOrderHeader WHERE SalesPersonID = 276; This one prefers a Hash Match to a standard lookup even! This isn’t just ordinary index intersection, this is something else again! Just like before, we could imagine it better with two whole tables, but we shouldn’t try to distinguish between joining two tables and joining two indexes. The Query Optimizer can see (using basic maths) that it’s worth doing these particular operations using these two less-than-ideal indexes (because of course, the best indexese would be on both columns – a composite such as (SalesPersonID, CustomerID – and it would have the SalesOrderID column as part of it as the CIX key still). You need to think like this too. Not in terms of excusing single-column indexes like the ones in AdventureWorks2012, but in terms of having a picture about how you’d like your queries to run. If you start to think about what data you need, where it’s coming from, and how it’s going to be used, then you will almost certainly write better queries. …and yes, this would include when you’re dealing with regular joins across multiples, not just against joins within single table queries.

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• PeopleSoft at Alliance 2012 Executive Forum

  - by John Webb

  Guest Posting From Rebekah Jackson This week I jointed over 4,800 Higher Ed and Public Sector customers and partners in Nashville at our annual Alliance conference.   I got lost easily in the hallways of the sprawling Gaylord Opryland Hotel. I carried the resort map with me, and I would still stand for several minutes at a very confusing junction, studying the map and the signage on the walls. Hallways led off in many directions, some with elevators going down here and stairs going up there. When I took a wrong turn I would instantly feel stuck, lose my bearings, and occasionally even have to send out a call for help.    It strikes me that the theme for the Executive Forum this year outlines a less tangible but equally disorienting set of challenges that our higher education customer’s CIOs are facing: Making Decisions at the Intersection of Business Value, Strategic Investment, and Enterprise Technology. The forces acting upon higher education institutions today are not neat, straight-forward decision points, where one can glance to the right, glance to the left, and then quickly choose the best course of action. The operational, technological, and strategic factors that must be considered are complex, interrelated, messy…and the stakes are high. Michael Horn, co-author of “Disrupting Class: How Disruptive Innovation Will Change the Way the World Learns”, set the tone for the day. He introduced the model of disruptive innovation, which grew out of the research he and his colleagues have done on ‘Why Successful Organizations Fail’. Highly simplified, the pattern he shared is that things start out decentralized, take a leap to extreme centralization, and then experience progressive decentralization. Using computers as an example, we started with a slide rule, then developed the computer which centralized in the form of mainframes, and gradually decentralized to mini-computers, desktop computers, laptops, and now mobile devices. According to Michael, you have more computing power in your cell phone than existed on the planet 60 years ago, or was on the first rocket that went to the moon. Applying this pattern to Higher Education means the introduction of expensive and prestigious private universities, followed by the advent of state schools, then by community colleges, and now online education. Michael shared statistics that indicate 50% of students will be taking at least one on line course by 2014…and by some measures, that’s already the case today. The implication is that technology moves from being the backbone of the campus, the IT department’s domain, and pushes into the academic core of the institution. Innovative programs are underway at many schools like Bellevue and BYU Idaho, joined by startups and disruptive new players like the Khan Academy.   This presents both threat and opportunity for higher education institutions, and means that IT decisions cannot afford to be disconnected from the institution’s strategic plan. Subsequent sessions explored this theme.    Theo Bosnak, from Attain, discussed the model they use for assessing the complete picture of an institution’s financial health. Compounding the issue are the dramatic trends occurring in technology and the vendors that provide it. Ovum analyst Nicole Engelbert, shared her insights next and suggested that incremental changes are no longer an option, instead fundamental changes are affecting the landscape of enterprise technology in higher ed.    Nicole closed with her recommendation that institutions focus on the trends in higher education with an eye towards the strategic requirements and business value first. Technology then is the enabler.   The last presentation of the day was from Tom Fisher, Sr. Vice President of Cloud Services at Oracle. Tom runs the delivery arm of the Cloud Services group, and shared his thoughts candidly about his experiences with cloud deployments as well as key issues around managing costs and security in cloud deployments. Okay, we’ve covered a lot of ground at this point, from financials planning, business strategy, and cloud computing, with the possibility that half of the institutions in the US might not be around in their current form 10 years from now. Did I forget to mention that was raised in the morning session? Seems a little hard to believe, and yet Michael Horn made a compelling point. Apparently 100 years ago, 8 of the top 10 education institutions in the world were German. Today, the leading German school is ranked somewhere in the 40’s or 50’s. What will the landscape be 100 years from now? Will there be an institution from China, India, or Brazil in the top 10? As Nicole suggested, maybe US parents will be sending their children to schools overseas much sooner, faced with the ever-increasing costs of a US based education. Will corporations begin to view skill-based certification from an online provider as a viable alternative to a 4 year degree from an accredited institution, fundamentally altering the education industry as we know it?

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