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• How do I install graphviz 2.29 in 12.04?

  - by bidur

  In my ubuntu 12.04, the graphviz is not the latest version(2.29). I need some features available in the latest version of graphviz. I tried to install the graphviz version 2.29, which requires libgraphviz4(=2.18). I anyhow installed libgraphviz4 and installed graphviz 2.29. For that I have to remove packages libcdt4 and libpathplan4. Now whenever I try to generate graph, I get some problems: For e.g.: dot -Kfdp -n -Tpng -o samplePOS.png forcePOS.dot It says: dot: error while loading shared libraries: libgvc.so.6: cannot open shared object file: No such file or directory neato -Tps -o sample_1.ps sourcedot.gv It says: neato: error while loading shared libraries: libgvc.so.6: cannot open shared object file: No such file or directory So, I am looking for some ways so that I can run graphviz 2.29 in my ubuntu 12.04.

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• How can I lower my C# learning curve? [closed]

  - by MSU

  I have been learning programming, mostly C# and .net stuff. And I have target to become a fulltime .NET developer. But I am feeling that learning Graph is very slow, I have been learning C# programming, doing some coding everyday, but how I can learn very fast and increase my skills rapidly? I know there should be a balance of coding and reading, as without reading I can't code and without coding I can't increase my skills. SO, I am requesting here suggesting from experts on how I bring more pace to my learning curve? I intend to give 4-6 hours daily for this and on weekends 10+ hours.

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• Aide On a Low Memory System

  - by Jason Mock

  I have a Linux server running on a Linode.com VPS, where I'm trying to utilize aide to detect any issues. However, the nightly aide run uses up all of my available memory and swap (512MB RAM / 384MB SWAP). I've tried adding a script to /etc/cron.daily that would stop/start services using a lot of memory (apache2, mysql) during the aide run. Unfortunately, it seems like aide continued to use every available byte (including the space freed up from apache2 and mysql). Here's a graph from munin showing what happens when aide runs: Note the spike of memory usage, well into swap, when aide runs Any suggestions on tuning aide to not use so much memory, or is there an alternative to aide that doesn't behave this way?

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• Stateless game design

  - by L. De Leo

  I'm facing a challenge understanding how to program a web version of a card game that is completely stateless. I create my object graph when the game begins and distribute cards to PlayerA and PlayerB so I lay them out on the screen. At this point I could assume that HTML and the querystring is what holds at least some of my state and just keep a snapshot copy of the game state on the server-side for the sole purpose of validating the inputs I receive from the web clients. Still it appears to me that the state of the game is by its nature mutable: cards are being dealt from the deck, etc... Am I just not getting it? Or should I just strive to minimize the side-effects of my functions to the objects that I take as my input? How would you design a stateless card game?

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• Separating merged array of arithmetic and geometric series [closed]

  - by user1814037

  Possible Duplicate: Separating merged array of arithmetic and geometric series My friend asked me an interseting question. Given an array of positive integers in increasing order. Seperate them in two series, an arithmetic sequence and geometric sequence. The given array is such that a solution do exist. The union of numbers of the two sequence must be the given array. Both series can have common elements i.e. series need not to be disjoint. The ratio of the geometric series can be fractional. Example: Given series : 2,4,6,8,10,12,25 AP: 2,4,6,8,10,12 GP: 4,10,25 I tried taking few examples but could not reach a general way. Even tried some graph implementation by introducing edges if they follow a particular sequence but could not reach solution.

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• Writing a spell checker similar to "did you mean"

  - by user888734

  I'm hoping to write a spellchecker for search queries in a web application - not unlike Google's "Did you mean?" The algorithm will be loosely based on this: http://catalog.ldc.upenn.edu/LDC2006T13 In short, it generates correction candidates and scores them on how often they appear (along with adjacent words in the search query) in an enormous dataset of known n-grams - Google Web 1T - which contains well over 1 billion 5-grams. I'm not using the Web 1T dataset, but building my n-gram sets from my own documents - about 200k docs, and I'm estimating tens or hundreds of millions of n-grams will be generated. This kind of process is pushing the limits of my understanding of basic computing performance - can I simply load my n-grams into memory in a hashtable or dictionary when the app starts? Is the only limiting factor the amount of memory on the machine? Or am I barking up the wrong tree? Perhaps putting all my n-grams in a graph database with some sort of tree query optimisation? Could that ever be fast enough?

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• How to detect and collide two elastic line segments?

  - by Tautrimas

  There are 4 moving physical nodes in 3D space. They are paired with two elastic line segments / strings (1 <- 2; 3 <- 4). Part I: How to detect the collision of two segments? Part II: On the moment of collision, fifth node is created at the intersection point and here you have the force-based graph. 5-th node (bend point) can slide among the strings as in a real world. Given the new coordinates of 4 nodes, how to calculate the position of the 5-th node on the next frame? I assume string force on the nodes to be F = -k * x where x is the string length. All I came up to is that the force between 5 and 1 equals 5 and 2 (the same with 3 and 4). What are the other properties?.

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• Periodic script execution

  - by Vagelism

  I made a script that sends my local sensors temperature to a server in the internet and then I can see a graph of it. Everything works fine when I execute it manully. I have the latest ubuntu version. When it comes to run periodically every minute with crontab then nothing works. It doesnt send anything. I tried to run it as SUDO and as user, I tried to add it in the crontab file to run it from several locations like /bin/myscript.sh , /user/Desktop and many others...Nothing seems to work. Any Idea how to solve it? Thank you!

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• How does Google store search trends in backend?

  - by Achshar

  Google trends shows what query has been searched how many times and some other properties of the said query. But how is this data stored in a database? Storing a new row for every search does not seem right. They also tell the query on a time graph, so they must have some way to look for individual searches made by users, but the number of queries they get every day, it does not feel right that they would store every search in a database row along with a time-stamp. This does not apply to just Google trends or Google in general but any other big site that gets awful number of queries and then has tools to see them in depth. I am not an expert on this but I am interested to know some high level structure of how things work behind the scenes.

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• How can I refactor my code to use fewer singletons?

  - by fish

  I started a component based, networked game (so far only working on the server). I know why singletons can be bad, but I can't think of another way to implement the same thing. So far I have: A GameState singleton (for managing the global state of the game, i.e. pre-game, running, exiting). A World singleton, which is the root entity for my entity graph An EntityFactory A ComponentFactory I'm thinking about adding a "MessageDispatcher" so individual components can subscribe to network messages. The factories do not have state, so I suppose they aren't so bad. However, the others do have global state, which is asking for trouble. How can I refactor my code so it uses fewer singletons?

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• Basic/research RTS engine/model

  - by XTF

  Does a basic/research RTS engine/model exist that can be used as a basis for further experimentation/research? I'd like to avoid reinventing the wheel if possible. I'm aware of Spring Engine and Stratagus, but those are real game engines and may not be the best to experiment with and learn from. Ideally the docs for the model would answer questions like: How exactly do units move? (constant velocity? constant acceleration? constant force?) How is pathfinding handled? Does every grid cell become an A* graph node (may be expensive)? Does it consider threats? How are groups handled? (w.r.t pathfinding and movement) How is combat handled? I'm mostly interested in the low-level model details (for now), not the graphics etc. I've read a lot of the other quesions (and answers/references) tagged RTS but I haven't found my answer yet.

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• Does a large (hidden) submenu count towards site content in tems of determining page similarities?

  - by Name

  Basically, I have this site that recently lost a lot of traffic after I optimized the html, the exact reasons to which are uncertain. The graph of impressions (times a page appears on search listings) is continuously going down like an e^-x function. Because the content, previously occupying five pages of tables, now fits within a few paragraph tags, the menu now occupies about 80% of the live html code and I am starting to have doubts wherether this affects the "similar pages" factor that Google punishes. Questions: As far as I know, Google ignores invisible material and the submenus are only visible when hovered over. Has anything at all changed in this area? If I ajax in the submenus, leaving only the main eight menu items to load, will I be punished for "hiding" information? Is the idea worth testing or is it frankly retarded?

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• Asp.net MVC Route class that supports catch-all parameter anywhere in the URL

  - by Robert Koritnik

  the more I think about it the more I believe it's possible to write a custom route that would consume these URL definitions: {var1}/{var2}/{var3} Const/{var1}/{var2} Const1/{var1}/Const2/{var2} {var1}/{var2}/Const as well as having at most one greedy parameter on any position within any of the upper URLs like {*var1}/{var2}/{var3} {var1}/{*var2}/{var3} {var1}/{var2}/{*var3} There is one important constraint. Routes with greedy segment can't have any optional parts. All of them are mandatory. Example This is an exemplary request http://localhost/Show/Topic/SubTopic/SubSubTopic/123/This-is-an-example This is URL route definition {action}/{*topicTree}/{id}/{title} Algorithm Parsing request route inside GetRouteData() should work like this: Split request into segments: Show Topic SubTopic SubSubTopic 123 This-is-an-example Process route URL definition starting from the left and assigning single segment values to parameters (or matching request segment values to static route constant segments). When route segment is defined as greedy, reverse parsing and go to the last segment. Parse route segments one by one backwards (assigning them request values) until you get to the greedy catch-all one again. When you reach the greedy one again, join all remaining request segments (in original order) and assign them to the greedy catch-all route parameter. Questions As far as I can think of this, it could work. But I would like to know: Has anyone already written this so I don't have to (because there are other aspects to parsing as well that I didn't mention (constraints, defaults etc.) Do you see any flaws in this algorithm, because I'm going to have to write it myself if noone has done it so far. I haven't thought about GetVirtuaPath() method at all.

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• Implementing Autocompletion in iPhone UITextField for contacts in address book

  - by nacho4d

  Hi, I would like to have a UITextField or UITextView in where as I do some input, alternatives will appear something similar to when you type an address in Mail Application, alternatives appear down and is possible tap them so get a better input user interface.(since there is no need to type the complete word or address or phone number) I do know how to fetch data from Address Book framework, also how to input text in UITextField/UITextView and its delegates but I don't know what kind of structure to use for fetching and showing data as the user do his/her input. I know basic CoreData if this matters, I hope I can get some help. UPDATE (2010/3/10): I don't have problem make a native-like GUI but I am asking about the algorithm, does any body knows what kind algorithm is best for this thing? maybe some binary tree? Or should I just fetch data from coredata everytime? Thanks Ignacio UPDATE (2010/03/28): I've been very busy these days, so I have not tried UISearchResults but it seems fine to me. BUT I wonder was there a necessity of deletion of the wining answer? I don't think is fair my reputation went down and couldn't see the winning answer. ;(

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• C++ behavior of for loops vs. while loops

  - by kjh

  As far as I understand, when you write a for-loop similar to this one for (int i = 0; i < SOME_NUM; i++) { if (true) do_something(); else do_something_else(); } The time complexity of this operation is mostly affected by the if (true) statement because the for-loop iterations don't actually involve any comparisons of i to SOME_NUM, the compiler will just essentially run the code inside the for-loop SOME_NUM times. Please correct me if I am wrong. However if this is correct, then how do the following nested for-loops behave? for (int i = 0; i < SOME_NUM; i++) { for (int j = 0; j < i; j++) { do_something(); } } The j in the inner for-loop is now upper bound by i, a value that changes every time the loop restarts. How will the compiler compile this? Do these nested for-loops essentially behave like a for-loop with while-loop inside of it? If you're writing an algorithm that uses nested for-loops where the inner counting variable depends on the outer counting variable should you be concerned about what this will do to the complexity of your algorithm?

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• Get special numbers from a random number generator

  - by Wikeno

  I have a random number generator: int32_t ksp_random_table[GENERATOR_DEG] = { -1726662223, 379960547, 1735697613, 1040273694, 1313901226, 1627687941, -179304937, -2073333483, 1780058412, -1989503057, -615974602, 344556628, 939512070, -1249116260, 1507946756, -812545463, 154635395, 1388815473, -1926676823, 525320961, -1009028674, 968117788, -123449607, 1284210865, 435012392, -2017506339, -911064859, -370259173, 1132637927, 1398500161, -205601318, }; int front_pointer=3, rear_pointer=0; int32_t ksp_rand() { int32_t result; ksp_random_table[ front_pointer ] += ksp_random_table[ rear_pointer ]; result = ( ksp_random_table[ front_pointer ] >> 1 ) & 0x7fffffff; front_pointer++, rear_pointer++; if (front_pointer >= GENERATOR_DEG) front_pointer = 0; if (rear_pointer >= GENERATOR_DEG) rear_pointer = 0; return result; } void ksp_srand(unsigned int seed) { int32_t i, dst=0, kc=GENERATOR_DEG, word, hi, lo; word = ksp_random_table[0] = (seed==0) ? 1 : seed; for (i = 1; i < kc; ++i) { hi = word / 127773, lo = word % 127773; word = 16807 * lo - 2836 * hi; if (word < 0) word += 2147483647; ksp_random_table[++dst] = word; } front_pointer=3, rear_pointer=0; kc *= 10; while (--kc >= 0) ksp_rand(); } I'd like know what type of pseudo random number generation algorithm this is. My guess is a multiple linear congruential generator. And is there a way of seeding this algorithm so that after 987721(1043*947) numbers it would return 15 either even-only, odd-only or alternating odd and even numbers? It is a part of an assignment for a long term competition and i've got no idea how to solve it. I don't want the final solution, I'd like to learn how to do it myself.

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• cleaning up noise in an edge detection algoritum

  - by Faken

  I recently wrote an extremely basic edge detection algorithm that works on an array of chars. The program was meant to detect the edges of blobs of a single particular value on the array and worked by simply looking left, right, up and down on the array element and checking if one of those values is not the same as the value it was currently looking at. The goal was not to produce a mathematical line but rather a set of ordered points that represented a descritized closed loop edge. The algorithm works perfectly fine, except that my data contained a bit of noise hence would randomly produce edges where there should be no edges. This in turn wreaked havoc on some of my other programs down the line. There is two types of noise that the data contains. The first type is fairly sparse and somewhat random. The second type is a semi continuous straight line on the x=y axis. I know the source of the first type of noise, its a feature of the data and there is nothing i can do about it. As for the second type, i know it's my program's fault for causing it...though i haven't a hot clue exactly what is causing it. My question is: How should I go about removing the noise completely? I know that the correct data has points that are always beside each other and is very compact and ordered (with no gaps) and is a closed loop or multiple loops. The first type of noise is usually sparse and random, that could be easily taken care of by checking if any edges is next that noise point is also counted as an edge. If not, then the point is most defiantly noise and should be removed. However, the second type of noise, where we have a semi continuous line about x=y poses more of a problem. The line is sometimes continuous for random lengths (the longest was it went half way across my entire array unbroken). It is even possible for it to intersect the actual edge. Any ideas on how to do this?

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• certificate issues running app in windows 7 ?

  - by Jurjen

  Hi, I'm having some problems with my App. I'm using 'org.mentalis.security' assembly to create a certificate object from a 'pfx' file, this is the line of code where the exception occurs : Certificate cert = Certificate.CreateFromPfxFile(publicKey, certificatePassword); this has always worked and still does in production, but for some reason it throws an exception when run in windows 7 (tried it on 2 machines). CertificateException : Unable to import the PFX file! [error code = -2146893792] I can't find much on this message via google, but when checking the EventViewer I get an 'Audit Failure' every time this exception occurs: Event ID = 5061 Source = Microsoft Windows Security Task Category = system Integrity Keywords = Audit Failure Cryptographic operation. Subject: Security ID: NT AUTHORITY\IUSR Account Name: IUSR Account Domain: NT AUTHORITY Logon ID: 0x3e3 Cryptographic Parameters: Provider Name: Microsoft Software Key Storage Provider Algorithm Name: Not Available. Key Name: VriendelijkeNaam Key Type: User key. Cryptographic Operation: Operation: Open Key. Return Code: 0x2 ` I'm not sure why this isn't working on win 7, I've never had problems when I was running on Vista with this. I am running VS2008 as administrator but I guess that maybe the ASP.NET user doesn't have sufficient rights or something. It's pretty strangs that the 'Algorithm name' is 'Not Available' can anyone help me with this... TIA, Jurjen de Groot

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• Java SAX ContentHandler to create new objects for every root node

  - by behrk2

  Hello everyone, I am using SAX to parse some XML. Let's say I have the following XML document: <queue> <element A> 1 </element A> <element B> 2 </element B> </queue> <queue> <element A> 1 </element A> <element B> 2 </element B> </queue> <queue> <element A> 1 </element A> <element B> 2 </element B> </queue> And I also have an Elements class: public static Elements { String element; public Elements() { } public void setElement(String element){ this.element = element; } public String getElement(){ return element; } } I am looking to write a ContentHandler that follows the following algorithm: Vector v; for every <queue> root node { Element element = new Element(); for every <element> child node{ element.setElement(value of current element); } v.addElement(element); } So, I want to create a bunch of Element objects and add each to a vector...with each Element object containing its own String values (from the child nodes found within the root nodes. I know how to parse out the elements and all of those details, but can someone show me a sample of how to structure my ContentHandler to allow for the above algorithm? Thanks!

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• How do you efficiently implement a document similarity search system?

  - by Björn Lindqvist

  How do you implement a "similar items" system for items described by a set of tags? In my database, I have three tables, Article, ArticleTag and Tag. Each Article is related to a number of Tags via a many-to-many relationship. For each Article i want to find the five most similar articles to implement a "if you like this article you will like these too" system. I am familiar with Cosine similarity and using that algorithm works very well. But it is way to slow. For each article, I need to iterate over all articles, calculate the cosine similarity for the article pair and then select the five articles with the highest similarity rating. With 200k articles and 30k tags, it takes me half a minute to calculate the similar articles for a single article. So I need another algorithm that produces roughly as good results as cosine similarity but that can be run in realtime and which does not require me to iterate over the whole document corpus each time. Maybe someone can suggest an off-the-shelf solution for this? Most of the search engines I looked at does not enable document similarity searching.

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• Writing String to Stream and reading it back does not work

  - by Binary255

  I want to write a String to a Stream (a MemoryStream in this case) and read the bytes one by one. stringAsStream = new MemoryStream(); UnicodeEncoding uniEncoding = new UnicodeEncoding(); String message = "Message"; stringAsStream.Write(uniEncoding.GetBytes(message), 0, message.Length); Console.WriteLine("This:\t\t" + (char)uniEncoding.GetBytes(message)[0]); Console.WriteLine("Differs from:\t" + (char)stringAsStream.ReadByte()); The (undesired) result I get is: This: M Differs from: ? It looks like it's not being read correctly, as the first char of "Message" is 'M', which works when getting the bytes from the UnicodeEncoding instance but not when reading them back from the stream. What am I doing wrong? The bigger picture: I have an algorithm which will work on the bytes of a Stream, I'd like to be as general as possible and work with any Stream. I'd like to convert an ASCII-String into a MemoryStream, or maybe use another method to be able to work on the String as a Stream. The algorithm in question will work on the bytes of the Stream.

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• How Random is System.Guid.NewGuid()? (Take two)

  - by Vilx-

  Before you start marking this as a duplicate, read me out. The other question has a (most likely) incorrect accepted answer. I do not know how .NET generates its GUIDs, probably only Microsoft does, but there's a high chance it simply calls CoCreateGuid(). That function however is documented to be calling UuidCreate(). And the algorithms for creating an UUID are pretty well documented. Long story short, be as it may, it seems that System.Guid.NewGuid() indeed uses version 4 UUID generation algorithm, because all the GUIDs it generates matches the criteria (see for yourself, I tried a couple million GUIDs, they all matched). In other words, these GUIDs are almost random, except for a few known bits. This then again raises the question - how random IS this random? As every good little programmer knows, a pseudo-random number algorithm is only as random as its seed (aka entropy). So what is the seed for UuidCreate()? How ofter is the PRNG re-seeded? Is it cryptographically strong, or can I expect the same GUIDs to start pouring out if two computers accidentally call System.Guid.NewGuid() at the same time? And can the state of the PRNG be guessed if sufficiently many sequentially generated GUIDs are gathered?

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• How can I load file into web app through certain periods?

  - by Elena

  Hi all! I have next task: I need to load the same file into my web app several times, for example - twice a day! Suppose in that file I have information, that changes, and I need to load this info into my app to change the statistics for example. How can I load file several times (twice an hour, or twice a day)? What should I use? Is any algorithm to do that? I am not allowed to use external libraries like Quartz Scheduler. So I need to do it with Thread and/or Timer. Can anybody give me some example or algorithm how to do it. Where can I create the entry point to my Thread, can I do it in managed bean or I need some sort of filter/listener/servlet. I works with jsf and richFaces. Maybe in this technologies there are some algorithms to solve my problem. Any ideas? Thanks very much for help!

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• Scheme Infix to Postfix

  - by Cody

  Let me establish that this is part of a class assignment, so I'm definitely not looking for a complete code answer. Essentially we need to write a converter in Scheme that takes a list representing a mathematical equation in infix format and then output a list with the equation in postfix format. We've been provided with the algorithm to do so, simple enough. The issue is that there is a restriction against using any of the available imperative language features. I can't figure out how to do this in a purely functional manner. This is our fist introduction to functional programming in my program. I know I'm going to be using recursion to iterate over the list of items in the infix expression like such. (define (itp ifExpr) ( ; do some processing using cond statement (itp (cdr ifExpr)) )) I have all of the processing implemented (at least as best I can without knowing how to do the rest) but the algorithm I'm using to implement this requires that operators be pushed onto a stack and used later. My question is how do I implement a stack in this function that is available to all of the recursive calls as well?

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• How should I go about implementing a points-to analysis in Maude?

  - by reprogrammer

  I'm going to implement a points-to analysis algorithm. I'd like to implement this analysis mainly based on the algorithm by Whaley and Lam. Whaley and Lam use a BDD based implementation of Datalog to represent and compute the points-to analysis relations. The following lists some of the relations that are used in a typical points-to analysis. Note that D(w, z) :- A(w, x),B(x, y), C(y, z) means D(w, z) is true if A(w, x), B(x, y), and C(y, z) are all true. BDD is the data structure used to represent these relations. Relations input vP0 (variable : V, heap : H) input store (base : V, field : F, source : V) input load (base : V, field : F, dest : V) input assign (dest : V, source : V) output vP (variable : V, heap : H) output hP (base : H, field : F, target : H) Rules vP(v, h) :- vP0(v, h) vP(v1, h) :- assign(v1, v2), vP(v2, h) hP(h1, f,h2) :- store(v1, f, v2), vP(v1, h1), vP(v2, h2) vP(v2, h2) :- load(v1, f, v2), vP(v1, h1), hP(h1, f, h2) I need to understand if Maude is a good environment for implementing points-to analysis. I noticed that Maude uses a BDD library called BuDDy. But, it looks like that Maude uses BDDs for a different purpose, i.e. unification. So, I thought I might be able to use Maude instead of a Datalog engine to compute the relations of my points-to analysis. I assume Maude propagates independent information concurrently. And this concurrency could potentially make my points-to analysis faster than sequential processing of rules. But, I don't know the best way to represent my relations in Maude. Should I implement BDD in Maude myself, or Maude's internal unification based on BDD has the same effect?

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