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• shortest path search in a map represented as 2d shapes

  - by joe_shmoe

  Hi, I have a small library of a few shortest path search algorithms. They were developed for simple undirected graphs (the normal representation - vertices and edges). Now I'd like to somehow apply them on a bit different scenario - where the maps are represented as 2-dimensional shapes, connected by shared edges (edges of the polygons, that is). In this scenario, the search can start/end either at a map object or some point (x,y). What would be the best approach? Try to apply the algorithms onto shapes? or try to extract a 'normal' graph out of the shapes (I have preprocessing time available)? Any advice would be much appreciated, as I'm really not sure which way to go, and I don't have enough time (and skill) to explore many options... Thanks a lot

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• circuit/block-diagram drawing

  - by JCLL

  I'm looking for either algorithms or visualization tool for (nice) circuit/block-diagram drawing. I am also interested in a general formulation of the problem. By "circuit drawing", I mean the capability of exploring place & route for block-diagrams (rectangles) with I/O ports and their connections (wires). These block-diagrams can be hierarchical i.e some blocks may have some nested internal sub-structure etc. This topic is strongly related to classical graph-drawing, with the supplemental constraint of the need to take ports location into account, and possibly the shape of the blocks (rectangle of various sizes). Graphviz tools do not respond to the problem (at least my previous experiments have not been satisfactory). Force-directed algorithms retain my attention, but I have just found papers on classical directed graphs. Any hints ?

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• Stream post URL security and wall post links

  - by Jeff Lee

  Our app's mobile client can create wall post links to our app's web-facing pages. Since this happens in the context of a mobile app, we do this on behalf of our user using the Graph API's feed/message endpoint. I noticed that the links showing up in the wall posts are being routed through our app's auth dialog, which is NOT what we want. We just want transparent links, without forcing the client to auth our app, similar to what happens when you share to FB in Path. I went ahead and disabled the "Stream post URL option" several hours ago, but we still seem to be getting the re-routed links for wall posts. The target URLs for these links are within the domain we've registered for our Facebook app. Is there anything else I need to do fix this?

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• best way to get new access_token using PHP sdk

  - by randy

  I am getting the error "An active access token must be used to query information about the current user". There seems to be tons of articles and ideas, but am very confused and it seems that things are changing as well. A lot say to use offline-access but that appears to be going away. I did find this article. Does anyone have an example using the PHP SDK? I tried doing something like the below but it does not seem to work; $FBuser is still zero: $token_url = "https://graph.facebook.com/oauth/access_token?" . "client_id=" . FB_APP_ID . "&client_secret=" . FB_APP_SECRET . "&grant_type=client_credentials"; list($name, $ACCESS_TOKEN) = explode("=", file_get_contents($token_url) ); $facebook->setAccessToken(ACCESS_TOKEN); $FBuser = $facebook->getUser();

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• Code jumps out of a jar and runs? What is causing this?

  - by Mike

  I am trying to get a sample program working with JUNG, a graphing tool in Java. I downloaded and referenced all the .jar files in eclipse so my project hierarchy looks like this: In Test.java I have the following code: public class Test { static public void main() { System.out.print("Hello"); }} For some reason though when I try to run it as a Java Application by right clicking on Jung test in the project hierarchy I am presented with a bunch of classes. My Test.java isn't on the list so if I just leave it as ** and press ok it starts running a program that is dynamically adding nodes and vertexes to a graph. I can't seem to figure out what code its actually executing. I know java but stuff like this with the jar files seems to be getting lost on me. Any ideas? Thanks

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• Recommended Tutorials for php mysql and graphs

  - by Vinit Joshi

  I need help to find a tutorial or anything to help me create a comparison chart. The user is able to search for device names. The information about the device names is in a drop down box dynamically added from the database. I want the user to be able to select two separate devices and view the devices information plotted onto a graph. I'll be grateful for keywords that I can search for or any tutorials that will help me to carry on with this task. Currently on my screen I can see the data that has been inserted into the database. This data is placed inside a table. I have so far used xhtml, php and mysql. I've tried to make the question as clear as possible so sorry if it does confuse anyone.

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• st-ordering library function?

  - by chang

  I'm in the search for an implementation of an ear-decomposition algorithm (http://www.ics.uci.edu/~eppstein/junkyard/euler/ear.html). I examined networkx and didn't find one. Although the algorithm layout is vaguely in my mind, I'd like to see some reference implementation, too. Side problem: First step could be an st-ordering of a graph. Are there any implementations for st-ordering algorithms you know? Thanks for your input. I'd really like to contribute e.g. to networkx by implementing the ear-decomposition algorithm in python.

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• All minimum spanning trees implementation

  - by russtbarnacle

  I've been looking for an implementation (I'm using networkx library.) that will find all the minimum spanning trees (MST) of an undirected weighted graph. I can only find implementations for Kruskal's Algorithm and Prim's Algorithm both of which will only return a single MST. I've seen papers that address this problem (such as http://fano.ics.uci.edu/cites/Publication/Epp-TR-95-50.html) but my head tends to explode someway through trying to think how to translate it to code. In fact i've not been able to find an implementation in any language!

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• core-plot and NSDate (iPhone)

  - by Urizen

  I wish to plot a line graph where the x-axis is defined as a number of days between two dates and the y-axis is a value that varies on each of the days. I can plot the y values as an NSNumber but I have no idea how to set the ranges and the markup on the x-axis. I have looked at the date example in the "examples" directory of the core-plot distribution but have found it a little confusing. Does anyone know of a tutorial, or code sample, which might asist me in this regard? Thank you in advance.

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• Why is image_hash empty for some ad_creatives? Is it because it is expired?

  - by Chris Conner

  I ran _"https://graph.facebook.com/act_47121778/adcreatives?access_token=_ and got the following results. Why are some creatives returning empty image hash? { "view_tag": "", "alt_view_tags": [ ], "creative_id": "6002716206572", "type": 1, "title": "Grow your fans!", "body": "Fan Page Owners! Grow your fanbase. Create quizzes for your page. Win $100 Weekly. Make money with our revenue share program.", "image_hash": "6ac30e43f21c8580361de92d3288ed68", "link_url": "http://www.facebook.com/quizwriter?sk=app_81434956828", "name": "Grow your fans!", "run_status": 1, "preview_url": "http://www.facebook.com/ads/api/creative_preview.php?cid=6002716206572", "count_current_adgroups": 1, "id": "6002716206572", "image_url": "http://creative.ak.fbcdn.net/v41818/flyers/109/44/1296329249810543669_1_31eb15ed.jpg" }, { "view_tag": "", "alt_view_tags": [ ], "creative_id": "6002444043572", "type": 1, "title": "Tennis Champs Social Game", "body": "Tennis Champ! Start with 5,000 dollars , beat out other players with your mad tennis skills and become the tennis champ! Socialize!", "image_hash": "", "link_url": "334886511760", "name": "Tennis Champs Social Game", "run_status": 1, "preview_url": "http://www.facebook.com/ads/api/creative_preview.php?cid=6002444043572", "count_current_adgroups": 2, "id": "6002444043572" },

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• Trust metrics and related algorithms

  - by Nick Gerakines

  I'm trying to learn more about trust metrics (including related algorithms) and how user voting, ranking and rating systems can be wired to stiffle abuse. I've read abstract articles and papers describing trust metrics but haven't seen any actual implementations. My goal is to create a system that allows users to vote on other users and the content of other users and with those votes and related meta-data, determine if those votes can be applied to a users level or popularity. Have you used or seen some sort of trust system within a social graph? How did it work and what were its areas of strength and weaknesses?

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• Java: how to represent graphs?

  - by Rosarch

  I'm implementing some algorithms to teach myself about graphs and how to work with them. What would you recommend is the best way to do that in Java? I was thinking something like this: public class Vertex { private ArrayList<Vertex> outnodes; //Adjacency list. if I wanted to support edge weight, this would be a hash map. //methods to manipulate outnodes } public class Graph { private ArrayList<Vertex> nodes; //algorithms on graphs } But I basically just made this up. Is there a better way? Also, I want it to be able to support variations on vanilla graphs like digraphs, weighted edges, multigraphs, etc.

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• Neo4j+Gremlin : Trouble with T.gte and floating point node attributes

  - by letronje

  For a type of nodes in my graph, attribute values for an attribute(named 'some_count') is either missing or an integer or a float. I'm trying to write gremlin to filter these nodes based on minimum value for this attribute. I first verified that the values are indeed present by firing the following gremlin g.v(XXX)._().in('category').hasNot('some_count', T.eq, null).back(1).some_count Next, I tried filtering by exact value and that works and show me the matching nodes or gives an empty array if there is no match g.v(XXX)._().in('category').hasNot('some_count', T.eq, null).back(1).has('some_count', T.eq, 120000.0d) But the following query that uses the 'greater than or equal to' comparator doesn't work. g.v(XXX)._().in('category').hasNot('some_count', T.eq, null).back(1).has('some_count', T.gte, 1.0d) this returns nil (I'm querying via ruby/rails using Neo4j AR Adapter ) Instead of returning an empty array for no match, it returns a nil, which tells me something could be wrong with the query itself. I'm running neo4j community server 1.8. Is there a way I can ask Neo4j to log errors/queries, to see what could be going wrong ?

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• Optimising Androidplot

  - by Zammbi

  Seems Androidplot (androidplot.com) website/forums are down so I'll try asking this question here. I have multi touch zoom and scrolling. Similar code to http://mlepicki.com/2012/03/androidplot-multitouch-zoom-scroll/ except that I have a bar graph instead. However with 100 data points it has noticeable lag. Even with 10 bars are just showing. Sounds like its drawing/calculating/etc all bars. Any idea on how I could optimise this? I can't use hardware rendering as I want to support Android 2.1 and the library doesn't support it(it breaks).

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• Who owes who money optimisation problem

  - by Francis

  Say you have n people, each who owe each other money. In general it should be possible to reduce the amount of transactions that need to take place. i.e. if X owes Y £4 and Y owes X £8, then Y only needs to pay X £4 (1 transaction instead of 2). This becomes harder when X owes Y, but Y owes Z who owes X as well. I can see that you can easily calculate one particular cycle. It helps for me when I think of it as a fully connected graph, with the nodes being the amount each person owes. Problem seems to be NP-complete, but what kind of optimisation algorithm could I make, nevertheless, to reduce the total amount of transactions? Doesn't have to be that efficient, as N is quite small for me.

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• Post wall message on facebook account

  - by Zeroshade

  Hello, I am trying to implement some functionality in a blackberry app, that I saw in other application. Basically it's a window that has a message, and a Facebook icon. When you click on the icon it launches a new window, this window asks the user for permissions(user and password), and then the message is posted in the user's wall. So my question is how can I replicate that?. I have been looking at the graph api, but I just can't figure out how to do all of this in one step. I mean just typing the url in the browser, and some post data. Thanks a lot.

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• Finding the longest road in a Settlers of Catan game algorithmically

  - by Jay

  I'm writing a Settlers of Catan clone for a class. One of the extra credit features is automatically determining which player has the longest road. I've thought about it, and it seems like some slight variation on depth-first search could work, but I'm having trouble figuring out what to do with cycle detection, how to handle the joining of a player's two initial road networks, and a few other minutiae. How could I do this algorithmically? For those unfamiliar with the game, I'll try to describe the problem concisely and abstractly: I need to find the longest possible path in an undirected cyclic graph.

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• NTFS Permission Structure to allow Traversal but no Modification except in Leaf Nodes?

  - by pepoluan

  Assume there's this folder structure: D:\ --+-- Acctg --+-- Payable | +-- Receivable | +-- Fin --+-- Inv | +-- Tax | +-- Treas | +-- Mrktg --+-- Ads +-- Promo Users are not allowed to change the structure, but they are free to create & delete files & folders in the leaf nodes (i.e., the rightmost folders). AGDLP principle said that I should assign permissions on the above folders to DL-Groups. Let's say I have a G-Group of users, G-Accounting-Payable, containing users that have access to the D:\Acctg\Payable folder. The way I see it, I have two strategies: - Strategy 1 Create three DL-Groups and assign them permissions: DL-D-Acctg_T -- allowed traversal of D:\Acctg folder DL-D-Acctg-Pay_LF -- allowed listing of D:\Acctg\Payable folder contents DL-D-Acctg-Pay__RW -- allowed full permissions to the contents of D:\Acctg\Payable folder Add G-Accounting-Payable as member to all the above DL-Groups - Strategy 2 Create just one DL-Group DL-D-Acctg-Pay__RW, and assign it the proper permissions for each level of the folder. Then, add G-Accounting-Payable as member to that DL-Group. - Which strategy is the Recommended Best Practice, and why?

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• help in the Donalds B. Johnson's algorithm, i cannot understand the pseudo code

  - by Pitelk

  Hi , does anyone know the Donald B. Johnson's algorithm which enumarates all the elementary circuits (cycles) in a Directed graph? link text I have the paper he had published in 1975 but I cannot understand the pseudo-code. My goal is to implement this algorithm in java. Some questions i have is for example what is the matrix Ak it refers to. In the pseudo code mentions that Ak:=adjacency structure of strong component K with least vertex in subgraph of G induced by {s,s+1,....n}; Does that mean i have to implement another algorithm that finds the Ak matrix? Another question is what the following means? begin logical f; Does also the line "logical procedure CIRCUIT (integer value v);" means that the circuit procedure returns a logical variable. In the pseudo code also has the line "CIRCUIT := f;" . Does this mean? It would be great if someone could translate this 1970's pseudocode to a more modern type of pseudo code so i can understand it in case you are interested to help but you cannot find the paper please email me at [email protected] and i will send you the paper. Thanks in advance

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• How to minimize total cost of shortest path tree

  - by Michael

  I have a directed acyclic graph with positive edge-weights. It has a single source and a set of targets (vertices furthest from the source). I find the shortest paths from the source to each target. Some of these paths overlap. What I want is a shortest path tree which minimizes the total sum of weights over all edges. For example, consider two of the targets. Given all edge weights equal, if they share a single shortest path for most of their length, then that is preferable to two mostly non-overlapping shortest paths (fewer edges in the tree equals lower overall cost). Another example: two paths are non-overlapping for a small part of their length, with high cost for the non-overlapping paths, but low cost for the long shared path (low combined cost). On the other hand, two paths are non-overlapping for most of their length, with low costs for the non-overlapping paths, but high cost for the short shared path (also, low combined cost). There are many combinations. I want to find solutions with the lowest overall cost, given all the shortest paths from source to target. Does this ring any bells with anyone? Can anyone point me to relevant algorithms or analogous applications? Cheers!

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• Facebook SDK Comment Deleting

  - by mwoodworth

  Working with the Facebook php SDK's, I am having a lot of trouble figuring out how to delete comments, given its id and xid. At first I was using the REST API, where you can call 'comments_remove($xid, $id);' to delete a comment. The problem with this method came when the xid parameter only accepts alphanumeric characters and underscores. Based on the documentation (http://developers.facebook.com/docs/reference/fbml/comments ) a valid XID can be the result of any url_encode. Now I am testing my luck with the new GRAPH api. Looking at http://developers.facebook.com/docs/api under 'Deleting Objects', It seems that comment deleting is definitely supported. However, I have tried sending a DELETE request, and I have also tried sending POST and GET to the object url with the argument 'method=delete'. No matter how I try it, I always get the same error: {"error":{"type":"GraphMethodException","message":"Unsupported delete request."}} I am sending the access token as a parameter as well. The access token that I am sending is the access token saved in the facebook cookie from the single sign on javascript cookie. These are all comments made on my application. Does this happen to anyone else, or am I simply not doing this right? Any help or guidance is GREATLY appreciated.

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• How to create closed areas (convex polygons) from set of line segments ?

  - by Marten

  The following problem is in 2D, so some simplifications can be made when suggesting answers. I need to create closed areas (defined either by line segments or just set of points - convex polygon) from a set of points/line segments. Basically I used Voronoi to generate "roads". Then I changed some of the data. Now I need a way to loop through that data (which is still line segments but doesn't comply with Voronoi anymore) and generate "neigbourhoods" that are bordered with the "roads". I looked at some graph diagrams and shortest path theories, but I could not figure it out. Logically it could be done by starting at left edge from one point, finding the way back to that point using the shortest path with available lines (using only clockwise directions). Then mark this line set down and remove from the data. Then you can repeat the same process and get all the areas like that. I tried to implement that but it did not get me anywhere as I could not figure out a way to write a C++ code that could do that. Problem was with choosing the most counterclockwise line from available lines from a specific point. All angle based math I did gave wrong answers because the way sin/cos are implemented in c++. So to summarize - if you can help me with a totally new approach to the problem its good, if not could you help me find a way to write the part of the code that finds the shortest clockwise path back to the beginning point using the line segment set as paths back. Thank you for your help!

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• ArrayList<String> NullPointerException

  - by Carlucho

  Am trying to solve a labyrinth by DFS, using adj List to represent the vertices and edges of the graph. In total there are 12 nodes (3 rows[A,B,C] * 4 cols[0,..,3]). My program starts by saving all the vertex labels (A0,..C3), so far so good, then checks the adjacent nodes, also no problems, if movement is possible, it proceeds to create the edge, here its where al goes wrong. adjList[i].add(vList[j].label); I used the debugger and found that vList[j].label is not null it contains a correct string (ie. "B1"). The only variables which show null are in adjList[i], which leads me to believe i have implemented it wrongly. this is how i did it. public class GraphList { private ArrayList<String>[] adjList; ... public GraphList(int vertexcount) { adjList = (ArrayList<String>[]) new ArrayList[vertexCount]; ... } ... public void addEdge(int i, int j) { adjList[i].add(vList[j].label); //NULLPOINTEREXCEPTION HERE } ... } I will really appreaciate if anyone can point me on the right track regrading to what its going wrong... Thanks!

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• Facebook app request in java not working

  - by Arpit Solanki

  I am trying to send a facebook app request to a user through the code below.But it gives an IO Exception and HTTP status code 400 in running.I dont see a any app request being sent to a user on running this. StringBuffer buffer = new StringBuffer(); buffer.append("access_token").append('=').append(this.app_access_token); buffer.append('&').append("message=").append("sent an app request!"); String content = buffer.toString(); try{ URLConnection connection = new URL("https://graph.facebook.com/me/apprequests").openConnection(); connection.setDoOutput(true); connection.setRequestProperty("Content-Type","application/x-www-form-urlencoded"); connection.setRequestProperty("Content-Length",Integer.toString(content.length())); DataOutputStream outs = new DataOutputStream(connection.getOutputStream()); outs.writeBytes(content); outs.flush(); outs.close(); BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream())); String inputLine; while ((inputLine = in.readLine()) != null) { System.out.println(inputLine); } in.close(); } catch(Exception e){ System.out.println(e); }

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• Is it a good idea to use MySQL and Neo4j together?

  - by Sanoj

  I will make an application with a lot of similar items (millions), and I would like to store them in a MySQL database, because I would like to do a lot of statistics and search on specific values for specific columns. But at the same time, I will store relations between all the items, that are related in many connected binary-tree-like structures (transitive closure), and relation databases are not good at that kind of structures, so I would like to store all relations in Neo4j which have good performance for this kind of data. My plan is to have all data except the relations in the MySQL database and all relations with item_id stored in the Neo4j database. When I want to lookup a tree, I first search the Neo4j for all the item_id:s in the tree, then I search the MySQL-database for all the specified items in a query that would look like: SELECT * FROM items WHERE item_id = 45 OR item_id = 345435 OR item_id = 343 OR item_id = 78 OR item_id = 4522 OR item_id = 676 OR item_id = 443 OR item_id = 4255 OR item_id = 4345 Is this a good idea, or am I very wrong? I haven't used graph-databases before. Are there any better approaches to my problem? How would the MySQL-query perform in this case?

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