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• Perl graph garbage collection usage

  - by Kevin

  Hi, I have built a tiny application in Perl that displays a graph over time. It graphs garbage collection usage over time. I use gnuplot to display the actual graph. This works fine if the time period is short, like a few hours. However, as the time increases (say a few days), the graph becomes difficult to read as the information gets crammed. Note that there is a tool called gcviewer which performs a similar function, it works by allowing you to choose the percentage of the graph. http://www.tagtraum.com/gcviewer.html Ideally I would like to take this further by adding the ability to "move" within the graph. I am not a developer but am good at scripting, so if there is some module in Perl which would provide this functionality it would be excellent! However, if it cannot be done in Perl, I am not averse to learning a new technology. Inputs are highly appreciated. Thanks!

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• Silverlight Line Graph with Gradient

  - by gav

  I have a series of points which I will turn into a line on a graph. What I want is to give the area under the graph a gradient fill. It would look somewhat similar to a Bloomberg graph like this; My question really has three parts; First, how should I fill only the area under the graph? Second, how do I fill that with a gradient? Finally, if I have multiple lines on the same graph any area under more than one line should have a greyscale gradient fill, how would you set this up? My biggest problem is deciding on the data structures to use, I could use many multiple sided shapes (One for each line/ data series) and then tell the brush to draw; Transparent if it's not in any shape The colour of one series if it's in one shape (Alpha relative to height to give grad) Black if it's in multiple shapes (Alpha relative to height to give grad) Then I'd draw the shapes' boundaries in white afterwards. Thanks, Gav

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• Graph Databases' Implementation

  - by user1478153

  I am having trouble visualizing a Graph Database. Visualizing an RDBMS is really very simple and I was able to understand from the first tutorial itself when I started learning it some 4-5 years ago. But I am not able to understand Graph Databases. I am also unable to get any good links on this topic, hence posting this question here. Specifically, I am looking for the following: Some really simple book/link on Graph Dbs Atleast some knowledge on the implementation details of a Graph DB (I hope all Graph DBs would be having atleast a few basic things in common). Thanks a lot in advance guys,

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• Looking for a good implementation that will access multiple databases simultaneously

  - by eibhrum

  I just want to find out if there's a good implementation (in C#/ASP.NET) on how to access my records from my different databases simultaneously. I have this simple application which suppose to search on these databases, then, display the record if a certain keyword is matched. I have like 5 databases (currently using MySQL) all in all and will be expanding it on the future (might be changing to SQL Server). I am fully aware on how to search on a single database, while I'm still learning how do it in multiple databases. Any tips, comments or suggestions?

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• Eliminating cyclic flows from a graph

  - by Jon Harrop

  I have a directed graph with flow volumes along edges and I would like to simplify it by removing all cyclic flows. This can be done by finding the minimum of the flow volumes along each edge in any given cycle and reducing the flows of every edge in the cycle by that minimum volume, deleting edges with zero flow. When all cyclic flows have been removed the graph will be acyclic. For example, if I have a graph with vertices A, B and C with flows of 1 from A?B, 2 from B?C and 3 from C?A then I can rewrite this with no flow from A?B, 1 from B?C and 2 from C?A. The number of edges in the graph has reduced from 3 to 2 and the resulting graph is acyclic. Which algorithm(s), if any, solve this problem?

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• Howto use FB Graph to post a message on a feed (wall)

  - by qualbeen

  I have created an app, and now i want to post a message on one of my friends wall with use of the new Graph API. Is this do-able? I am already using oAuth and the Graph-api to get a list of all my friends. The API at http://developers.facebook.com/docs/api tells me to cURL https://graph.facebook.com/[userid]/feed to read the feed, but it also tells me howto post a message: curl -F 'access_token=[...]' -F 'message=Hello, Arjun. I like this new API.' https://graph.facebook.com/arjun/feed Ofcourse this doesn't work! And I can't find out why.. Here are my PHP-code: require_once 'facebook.php'; // PHP-SDK downloaded from http://github.com/facebook/php-sdk $facebook = new Facebook(array(appId=>123, secret=>'secret')); $result = $facebook->api( '/me/feed/', array('access_token' => $this->access_token, 'message' => 'Playing around with FB Graph..') ); This code does not throws any error, and I know my access_token are correct (otherwise i could't run $facebook-api('/me?access_token='.$this-access_token); to get my userobject. Have anyone out there sucsessfully posted a message using Graph-api? Then i need your help! :-)

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• Big problem with Dijkstra algorithm in a linked list graph implementation

  - by Nazgulled

  Hi, I have my graph implemented with linked lists, for both vertices and edges and that is becoming an issue for the Dijkstra algorithm. As I said on a previous question, I'm converting this code that uses an adjacency matrix to work with my graph implementation. The problem is that when I find the minimum value I get an array index. This index would have match the vertex index if the graph vertexes were stored in an array instead. And the access to the vertex would be constant. I don't have time to change my graph implementation, but I do have an hash table, indexed by a unique number (but one that does not start at 0, it's like 100090000) which is the problem I'm having. Whenever I need, I use the modulo operator to get a number between 0 and the total number of vertices. This works fine for when I need an array index from the number, but when I need the number from the array index (to access the calculated minimum distance vertex in constant time), not so much. I tried to search for how to inverse the modulo operation, like, 100090000 mod 18000 = 10000 and, 10000 invmod 18000 = 100090000 but couldn't find a way to do it. My next alternative is to build some sort of reference array where, in the example above, arr[10000] = 100090000. That would fix the problem, but would require to loop the whole graph one more time. Do I have any better/easier solution with my current graph implementation?

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• Detecting Asymptotes in a Graph

  - by nasufara

  I am creating a graphing calculator in Java as a project for my programming class. There are two main components to this calculator: the graph itself, which draws the line(s), and the equation evaluator, which takes in an equation as a String and... well, evaluates it. To create the line, I create a Path2D.Double instance, and loop through the points on the line. To do this, I calculate as many points as the graph is wide (e.g. if the graph itself is 500px wide, I calculate 500 points), and then scale it to the window of the graph. Now, this works perfectly for most any line. However, it does not when dealing with asymptotes. If, when calculating points, the graph encounters a domain error (such as 1/0), the graph closes the shape in the Path2D.Double instance and starts a new line, so that the line looks mathematically correct. Example: However, because of the way it scales, sometimes it is rendered correctly, sometimes it isn't. When it isn't, the actual asymptotic line is shown, because within those 500 points, it skipped over x = 2.0 in the equation 1 / (x-2), and only did x = 1.98 and x = 2.04, which are perfectly valid in that equation. Example: In that case, I increased the window on the left and right one unit each. My question is: Is there a way to deal with asymptotes using this method of scaling so that the resulting line looks mathematically correct? I myself have thought of implementing a binary search-esque method, where, if it finds that it calculates one point, and then the next point is wildly far away from the last point, it searches in between those points for a domain error. I had trouble figuring out how to make it work in practice, however. Thank you for any help you may give!

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• Detecting Singularities in a Graph

  - by nasufara

  I am creating a graphing calculator in Java as a project for my programming class. There are two main components to this calculator: the graph itself, which draws the line(s), and the equation evaluator, which takes in an equation as a String and... well, evaluates it. To create the line, I create a Path2D.Double instance, and loop through the points on the line. To do this, I calculate as many points as the graph is wide (e.g. if the graph itself is 500px wide, I calculate 500 points), and then scale it to the window of the graph. Now, this works perfectly for most any line. However, it does not when dealing with singularities. If, when calculating points, the graph encounters a domain error (such as 1/0), the graph closes the shape in the Path2D.Double instance and starts a new line, so that the line looks mathematically correct. Example: However, because of the way it scales, sometimes it is rendered correctly, sometimes it isn't. When it isn't, the actual asymptotic line is shown, because within those 500 points, it skipped over x = 2.0 in the equation 1 / (x-2), and only did x = 1.98 and x = 2.04, which are perfectly valid in that equation. Example: In that case, I increased the window on the left and right one unit each. My question is: Is there a way to deal with singularities using this method of scaling so that the resulting line looks mathematically correct? I myself have thought of implementing a binary search-esque method, where, if it finds that it calculates one point, and then the next point is wildly far away from the last point, it searches in between those points for a domain error. I had trouble figuring out how to make it work in practice, however. Thank you for any help you may give!

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• Scientific Data processing(Graph comparison and interpretation)

  - by pinkynobrain

  Hi stackoverflow friends, I'm trying to write a program to automate one of my more boring and repetative work tasks. I have some programming experience but none with processing or interpreting large volumes of data so i am seeking your advice(both suggestions of techneques to try and also things to read to learn more about doing this stuff). I have a piece of equipment that monitors an experiment by taking repeated samples and displays the readings on its screen as a graph. The input of experiment can be altered and one of these changes should produce a change in a section of the graph which i currently identify by eye and is what im looking for in the experiment. I want to automate it so that a computer looks at a set of results and spots the experiment input that causes the change. I can already extract the results from the machine. Currently they results for a run are in the form of an integer array with the index being the sample number and the corresponding value being the measurement. The overall shape of the graph will be similar for each experiment run. The change im looking for will be roughly the same and will occur in approximatly the same place every time for the correct experiment input. Unfortunatly there are a few gotcha's that make this problem more difficult. There is some noise in the measuring process which mean there is some random variation in the measured values between different runs. Although the overall shape of the graph remains the same. The time the experiment takes varies slightly each run causing two effects. First, the a whole graph may be shifted slightly on the x axis relative to another runs graph. Second, individual features may appear slightly wider or narrower in different runs. In both these cases the variation isn't particularly large and you can assume that the only non random variation is caused by the correct input being found. Thank you for your time, Pinky

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• Scientific Data processing (Graph comparison and interpretation)

  - by pinkynobrain

  Hi stackoverflow friends, I'm trying to write a program to automate one of my more boring and repetitive work tasks. I have some programming experience but none with processing or interpreting large volumes of data so I am seeking your advice (both suggestions of techniques to try and also things to read to learn more about doing this stuff). I have a piece of equipment that monitors an experiment by taking repeated samples and displays the readings on its screen as a graph. The input of experiment can be altered and one of these changes should produce a change in a section of the graph which I currently identify by eye and is what I'm looking for in the experiment. I want to automate it so that a computer looks at a set of results and spots the experiment input that causes the change. I can already extract the results from the machine. Currently they results for a run are in the form of an integer array with the index being the sample number and the corresponding value being the measurement. The overall shape of the graph will be similar for each experiment run. The change I'm looking for will be roughly the same and will occur in approximately the same place every time for the correct experiment input. Unfortunately there are a few gotchas that make this problem more difficult. There is some noise in the measuring process which mean there is some random variation in the measured values between different runs. Although the overall shape of the graph remains the same. The time the experiment takes varies slightly each run causing two effects. First, the a whole graph may be shifted slightly on the x axis relative to another run's graph. Second, individual features may appear slightly wider or narrower in different runs. In both these cases the variation isn't particularly large and you can assume that the only non random variation is caused by the correct input being found. Thank you for your time, Pinky

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• Which technology is best suited to store and query a huge readonly graph?

  - by asmaier

  I have a huge directed graph: It consists of 1.6 million nodes and 30 million edges. I want the users to be able to find all the shortest connections (including incoming and outgoing edges) between two nodes of the graph (via a web interface). At the moment I have stored the graph in a PostgreSQL database. But that solution is not very efficient and elegant, I basically need to store all the edges of the graph twice (see my question PostgreSQL: How to optimize my database for storing and querying a huge graph). It was suggested to me to use a GraphDB like neo4j or AllegroGraph. However the free version of AllegroGraph is limited to 50 million nodes and also has a very high-level API (RDF), which seems too powerful and complex for my problem. Neo4j on the other hand has only a very low level API (and the python interface is not mature yet). Both of them seem to be more suited for problems, where nodes and edges are frequently added or removed to a graph. For a simple search on a graph, these GraphDBs seem to be too complex. One idea I had would be to "misuse" a search engine like Lucene for the job, since I'm basically only searching connections in a graph. Another idea would be, to have a server process, storing the whole graph (500MB to 1GB) in memory. The clients could then query the server process and could transverse the graph very quickly, since the graph is stored in memory. Is there an easy possibility to write such a server (preferably in Python) using some existing framework? Which technology would you use to store and query such a huge readonly graph?

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• Add a wall post to a page or application wall as page or application with facebook graph API

  - by blauesocke

  Hi, I wan't to create a new wall post on a appliaction page or a "normal" page with the facebook graph API. Is there a way to "post as page"? With the old REST-API it worked like this: $facebook->api_client->stream_publish($message, NULL, $links, $targetPageId, $asPageId); So, if I passed equal IDs for $targetPageId and $asPageId I was able to post a "real" wall post not caused by my own facebook account. Thanks!

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• How can I get node coordinates from a graph, using Perl?

  - by jonny

  Ok, I have a flowchart definition (basically, array of nodes and edges for each node). Now I want to calculate coordinates for every task in the flow, preferably hierarchycal style. I need something like Graph::Easy::Layout but I have no idea how to get nodes coordinates: I render nodes myself and I only want to retrieve box coordinates/size. Any suggestions? What I need is a CPAN module available even in Debian repository.

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• How does I/O work for large graph databases?

  - by tjb1982

  I should preface this by saying that I'm mostly a front end web developer, trained as a musician, but over the past few years I've been getting more and more into computer science. So one idea I have as a fun toy project to learn about data structures and C programming was to design and implement my own very simple database that would manage an adjacency list of posts. I don't want SQL (maybe I'll do my own query language? I'm just having fun). It should support ACID. It should be capable of storing 1TB let's say. So with that, I was trying to think of how a database even stores data, without regard to data structures necessarily. I'm working on linux, and I've read that in that world "everything is a file," including hardware (like /dev/*), so I think that that obviously has to apply to a database, too, and it clearly does--whether it's MySQL or PostgreSQL or Neo4j, the database itself is a collection of files you can see in the filesystem. That said, there would come a point in scale where loading the entire database into primary memory just wouldn't work, so it doesn't make sense to design it with that mindset (I assume). However, reading from secondary memory would be much slower and regardless some portion of the database has to be in primary memory in order for you to be able to do anything with it. I read this post: Why use a database instead of just saving your data to disk? And I found it difficult to understand how other databases, like SQLite or Neo4j, read and write from secondary memory and are still very fast (faster, it would seem, than simply writing files to the filesystem as the above question suggests). It seems the key is indexing. But even indexes need to be stored in secondary memory. They are inherently smaller than the database itself, but indexes in a very large database might be prohibitively large, too. So my question is how is I/O generally done with large databases like the one I described above that would be at least 1TB storing a big adjacency list? If indexing is more or less the answer, how exactly does indexing work--what data structures should be involved?

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• convert event an activity node graph to an event node graph

  - by nunos

  Does anyone know where I can find an implementation of an algorithm to convert an activity node graph to an event node graph? Thanks in advance.

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• Let MySQL users create databases, but allow access to only their own databases

  - by eikes

  I want to have multiple a MySQL users to be able to issue commands like CREATE DATABASE dbTest; But I also want each of these users to be able to see and access only their own databases. All I could find was how to either create the databases by a DBA and grant the privileges on this database to the specific user: GRANT ALL PRIVILEGES ON dbTest.* TO 'user'; or grant privileges on all databases to a user: GRANT ALL PRIVILEGES ON *.* TO 'user'; But neither is what I want, because it needs to scale and be secure.

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• Databases supporting parallel processing across multiple servers

  - by David

  I need a database engine that can utilize multiple servers for processing a single SQL query in parallel. So far I know that this is possible with the some engines, though none of them are feasible for me either because of pricing or missing features. The engines currently known to me are: MS SQL (enterprise) DB2 (enterprise) Oracle (enterprise) GridSQL Greenplum

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• Which databases support parallel processing across multiple servers?

  - by David

  I need a database engine that can utilize multiple servers for processing a single SQL query in parallel. So far I know that this is possible with the some engines, though none of them are feasible for me either because of pricing or missing features. The engines currently known to me are: MS SQL (enterprise) DB2 (enterprise) Oracle (enterprise) GridSQL Greenplum Which other engines have this feature? Do you have any experience with using this feature? Edit: I have now proposed a method for creating one myself. Any input is welcome. Edit: I have found another one: Informix Extended Parallel Server

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• How can I tag a user in a photo using the Facebook Graph API?

  - by fr6

  I tried: $args = array( 'access_token' => $access_token, 'id' => $uid ); $url = "https://graph.facebook.com/{$idPhoto}/tags"; $ch = curl_init(); curl_setopt($ch, CURLOPT_URL, $url); curl_setopt($ch, CURLOPT_HEADER, false); curl_setopt($ch, CURLOPT_RETURNTRANSFER, true); curl_setopt($ch, CURLOPT_POST, true); curl_setopt($ch, CURLOPT_POSTFIELDS, $args); curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false); curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2); $data = curl_exec($ch); It has returned me: {"error":{"type":"QueryParseException","message":"Unknown path components: \/tags"}} It does not seem possible because its not in the Facebook documentation: http://developers.facebook.com/docs/api#publishing Can someone confirm me that it's not possible to tag a user in a recently uploaded photo?

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• Error with python-setuptools doing "sudo easy_install python-graph-core"

  - by Dan

  Using easy_install, part of the python-setuptools, I get the following error: $ sudo easy_install python-graph-core [sudo] password for dan: Searching for python-graph-core Reading http://pypi.python.org/simple/python-graph-core/ Reading http://code.google.com/p/python-graph/ Reading http://code.google.com/p/python-graph/downloads/list?can=1 Reading http://code.google.com/p/python-graph/downloads/list Best match: python-graph-core 1.7.0 Downloading http://python-graph.googlecode.com/files/python-graph-core-1.7.0.tar.gz Processing python-graph-core-1.7.0.tar.gz Running python-graph-core-1.7.0/setup.py -q bdist_egg --dist-dir /tmp/easy_install-GwpYiM/python-graph-core-1.7.0/egg-dist-tmp-1yqbyV setup.py:8: Warning: 'as' will become a reserved keyword in Python 2.6 Traceback (most recent call last): File "/usr/bin/easy_install", line 8, in <module> load_entry_point('setuptools==0.6c9', 'console_scripts', 'easy_install')() File "/usr/lib/python2.5/site-packages/setuptools/command/easy_install.py", line 1671, in main with_ei_usage(lambda: File "/usr/lib/python2.5/site-packages/setuptools/command/easy_install.py", line 1659, in with_ei_usage return f() File "/usr/lib/python2.5/site-packages/setuptools/command/easy_install.py", line 1675, in <lambda> distclass=DistributionWithoutHelpCommands, **kw File "/usr/lib/python2.5/distutils/core.py", line 151, in setup dist.run_commands() File "/usr/lib/python2.5/distutils/dist.py", line 974, in run_commands self.run_command(cmd) File "/usr/lib/python2.5/distutils/dist.py", line 994, in run_command cmd_obj.run() File "/usr/lib/python2.5/site-packages/setuptools/command/easy_install.py", line 211, in run self.easy_install(spec, not self.no_deps) File "/usr/lib/python2.5/site-packages/setuptools/command/easy_install.py", line 446, in easy_install return self.install_item(spec, dist.location, tmpdir, deps) File "/usr/lib/python2.5/site-packages/setuptools/command/easy_install.py", line 476, in install_item dists = self.install_eggs(spec, download, tmpdir) File "/usr/lib/python2.5/site-packages/setuptools/command/easy_install.py", line 655, in install_eggs return self.build_and_install(setup_script, setup_base) File "/usr/lib/python2.5/site-packages/setuptools/command/easy_install.py", line 930, in build_and_install self.run_setup(setup_script, setup_base, args) File "/usr/lib/python2.5/site-packages/setuptools/command/easy_install.py", line 919, in run_setup run_setup(setup_script, args) File "/usr/lib/python2.5/site-packages/setuptools/sandbox.py", line 27, in run_setup lambda: execfile( File "/usr/lib/python2.5/site-packages/setuptools/sandbox.py", line 63, in run return func() File "/usr/lib/python2.5/site-packages/setuptools/sandbox.py", line 29, in <lambda> {'__file__':setup_script, '__name__':'__main__'} File "setup.py", line 8 except ImportError as ie: ^ SyntaxError: invalid syntax Any suggestions to what I may be doing wrong? Thanks, Dan

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• Looking for app to work fluidly with CSV data in graph form

  - by Aszurom

  It often occurs to me that if I had a good tool for viewing CSV data in graphical format, and comparing two sets of numbers to each other, I could do a great deal of meaningful trend watching and data interpretation. For example, perfmon can output quite a lot of data about a server into a CSV file, but there's no good way to view it. A lot of scripts could/have been written that would populate CSV files. I could write these all day long. My problem is that I need a great viewer. I've seen quite a few things that will take a CSV file and after a lot of tweaking and user adjustment produce a static gif/png image. A static image doesn't do me a lot of good, because I have to look at it, then re-calibrate the parameters of the program, regenerate the image, repeat. That sucks. I could do this in Excel. Ideally, I would want a FLUID graph viewer. On the fly, I can adjust how much of my timeline I'm viewing. I could adjust the scaling so that one big spike doesn't make 99.9% of the data an unreadable line across the bottom of the X axis. Stuff like that. I should be able to say "show me CSV column 3 and column 5 as graphs. Show me the data scaled for 20 or 150 entries, and let me slide that window up and down the column of data. Auto scale to fit 95% of data within the Y axis and let crazy spikes go off the screen." Maybe I'm terribly spoiled by how you can drag, zoom, and slide data around on my iPad. I want to be able to view a spreadsheet of data with that fluidity and not have to guess at what sort of static snapshot I want to create from it. I don't want to have to make a study of how to tweak some data plotting program to let me import my file and do what I could just do in Excel. I want to scale, zoom, and transform my graph on the fly and then export a snapshot of it once I have it the way I want it. Is there anything out there that fills this need? I'll take linux, osx, win32 or even iOS suggestions.

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• How to find whole graph coverage path in dynamic state-flow diagram?

  - by joseph

  Hello, As I've been researching algorithms for path finding in graph, I found interesting problem. Definition of situation: 1)State diagram can have p states, and s Boolean Fields, and z Int Fields 2)Every state can have q ingoing and r outgoing transitions, and h Int fields (h belongs to z - see above) 3)Every transition can have only 1 event, and only 1 action 4)every action can change n Boolean Fields, and x Int Fields 5)every event can have one trigger from combination of any count of Boolean Fields in diagram 6)Transition can be in OPEN/CLOSED form. If the transition is open/closed depends on trigger2 compounded from 0..c Boolean fields. 7) I KNOW algorithm for finding shortest paths from state A to state B. 8) I KNOW algorithm for finding path that covers all states and transitions of whole state diagram, if all transitions are OPEN. Now, what is the goal: I need to find shortest path that covers all states and transitions in dynamically changing state diagram described above. When an action changes some int field, the algorithm should go through all states that have changed int field. The algorithm should also be able to open and close transition (by going through transitions that open and close another transitions by action) in the way that the founded path will be shortest and covers all transitions and states. Any idea how to solve it? I will be really pleased for ANY idea. Thanks for answers.

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• boost graph adjacency_list, retrieving a node's parents

  - by Juan

  I want to find in an adjacency graph from the bgl how give a Vertexdescriptor and get the set of nodes that are parents of this given node. i would like to do this in directed graph, it seems you could use a bidirectional graph but i want to be able to restrict it so that there are no cycles.

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• A minimum spanning tree / shortest path in a directed graph

  - by mvid

  Given a directed graph with weighted edges, what algorithm can be used to give a sub-graph that has minimum weight, but allows movement from any vertex to any other vertex in the graph (under the assumption that paths between any two vertices always exist). Does such an algorithm exist?

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