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  • Boost Mersenne Twister: how to seed with more than one value?

    - by Eamon Nerbonne
    I'm using the boost mt19937 implementation for a simulation. The simulation needs to be reproducible, and that means storing and potentially reusing the RNG seeds later. I'm using the windows crypto api to generate the seed values because I need an external source for the seeds and not because of any particular guarantees of randomness. The output of any simulation run will have a note including the RNG seed - so the seed needs to be reasonably short. On the other hand, as part of the analysis of the simulation, I'll be comparing several runs - but to be sure that these runs are actually different, I'll need to use different seeds - so the seed needs to be long enough to avoid accidental collisions. I've determined that 64-bits of seeding should suffice; the chance of a collision will reach 50% after about 2^32 runs - that probability is low enough that the average error caused by it is negligible to me. Using just 32-bits of seed is tricky; the chance of a collision reaches 50% already after 2^16 runs; and that's a little too likely for my tastes. Unfortunately, the boost implementation either seeds with a full state vector - which is far, far too long - or a single 32-bit unsigned long - which isn't ideal. How can I seed the generator with more than 32-bits but less than a full state vector? I tried just padding the vector or repeating the seeds to fill the state vector, but even a cursory glance at the results shows that that generates poor results.

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  • Is there a Boost (or other common lib) type for matrices with string keys?

    - by mohawkjohn
    I have a dense matrix where the indices correspond to genes. While gene identifiers are often integers, they are not contiguous integers. They could be strings instead, too. I suppose I could use a boost sparse matrix of some sort with integer keys, and it wouldn't matter if they're contiguous. Or would this still occupy a great deal of space, particularly if some genes have identifiers that are nine digits? Further, I am concerned that sparse storage is not appropriate, since this is an all-by-all matrix (there will be a distance in each and every cell, provided the gene exists). I'm unlikely to need to perform any matrix operations (e.g., matrix multiplication). I will need to pull vectors out of the matrix (slices). It seems like the best type of matrix would be keyed by a Boost unordered_map (a hash map), or perhaps even simply an STL map. Am I looking at this the wrong way? Do I really need to roll my own? I thought I saw such a class somewhere before. Thanks!

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  • Compiling my Boost/NTL program with c++ on Linux.

    - by Martin Lauridsen
    Hi SO, I wrote a client program and a server program, that uses the NTL library and Boost::Asio, to do client/server communication for an integer factorization application, in C++. Both sides consist of several headers and cpp files. Both project compile fine individually on Windows in Visual Studio. All I did, was add the include path of NTL and Boost to both projects: Additional include paths: "D:\Downloads\WinNTL-5_5_2\include";D:\boost_1_42_0 Furthermore, for both projects, I added the two library paths to both projects in VS: Additional library directories: D:\boost_1_42_0\stage\lib;"D:\Documents\Visual Studio 2008\Projects\ntl\Debug" And added under Additional dependencies: ntl.lib As said, it compiles fine on Windows. But when I put the code on a Linux machine provided by university, I try to compile with the following statement c++ -I/appl/htopopt/Linux_x86_64/NTL-5.4.2/include -I/appl/htopopt/Linux_x86_64/boost_1_43_0/include client_protocol.cpp mpqs_client.cpp mpqs_sieve.cpp mpqs_helper.cpp -o mpqs_helper -L/appl/htopopt/Linux_x86_64/NTL-5.4.2/lib -lntl -L/appl/htopopt/Linux_x86_64/gmp-4.2.1/lib -lgmp -lm -L/appl/htopopt/Linux_x86_64/boost_1_43_0/lib -lboost_system -static Upon doing this, I get a huuuge error, which I posted here. Any idea how to fix this, please??

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  • (How) Can I approximate a "dynamic" index (key extractor) for Boost MultiIndex?

    - by Sarah
    I have a MultiIndex container of boost::shared_ptrs to members of class Host. These members contain private arrays bool infections[NUM_SEROTYPES] revealing Hosts' infection statuses with respect to each of 1,...,NUM_SEROTYPES serotypes. I want to be able to determine at any time in the simulation the number of people infected with a given serotype, but I'm not sure how: Ideally, Boost MultiIndex would allow me to sort, for example, by Host::isInfected( int s ), where s is the serotype of interest. From what I understand, MultiIndex key extractors aren't allowed to take arguments. An alternative would be to define an index for each serotype, but I don't see how to write the MultiIndex container typedef ... in such an extensible way. I will be changing the number of serotypes between simulations. (Do experienced programmers think this should be possible? I'll attempt it if so.) There are 2^(NUM_SEROTYPES) possible infection statuses. For small numbers of serotypes, I could use a single index based on this number (or a binary string) and come up with some mapping from this key to actual infection status. Counting is still darn slow. I could maintain a separate structure counting the total numbers of infecteds with each serotype. The synchrony is a bit of a pain, but the memory is fine. I would prefer a slicker option, since I would like to do further sorts on other host attributes (e.g., after counting the number infected with serotype s, count the number of those infected who are also in a particular household and have a particular age). Thanks in advance.

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  • Any implementations of graph st-ordering or ear-decomposition?

    - 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. I'm aware of Ulrik Brandes publication on a linear time Eager st-ordering algorithm, which results in an ear decomposition as a side product, if I understand correctly (it even includes pseudocode, which I'm trying to base my implementation on). 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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  • Facebook Open Graph - Grab how many times a page has been liked?

    - by DoMx
    I have a site that allows users to create a saying and then users "like" those sayings on Facebook. http://www.likeylikey.net/ I got a friend to throw up this simple code in less than 2 hours so it's basic. He knows little to nothing regarding the Open Graph API. Basically, I want to know how I can programmatically store how many times a page has been liked so I can list a "Top 10, most liked pages" list. Right now the index shows a list of all created pages and now I just wish to show the 10 most liked but I need a way of pulling that information from Facebook. Is this possible?

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  • Is there any way to validate the Open Graph protocol meta tags for Facebook integration?

    - by John
    Is there any way to validate the Facebook Open Graph protocol meta tags in the head section of my website? Code below. <meta property="og:title" content="my content" /> <meta property="og:type" content="company" /> <meta property="og:url" content="http://mycompany.com/" /> <meta property="og:image" content="http://mycompany.com/image.png" /> <meta property="og:site_name" content="my site name" /> <meta property="fb:admins" content="my_id" /> <meta property="og:description" content="my description" /> -edit- I mean validating the html. Sorry for the confusion! Right now my site isn't valid because of these tags.

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  • Fixed Resource Monitor Graph Scale in Windows Server 2008 R2

    - by Clever Human
    In Windows Server 2008 R2's Resource Monitor, is there a way to set the scale of the various graphs to be constant values instead of variable based on data? It seems to me that the utility of a graph is to get a quick overview glance at the values those graphs are showing. So if I look at the CPU graph and the line is up near the top, I can know immediately that something is using all my CPU and go investigate what. I don't really care if the CPU is jumping between .01% and 2%. Or if the network usage monitor is up near the top, I will know that all my bandwidth is being used up, and go figure out what. But the way things are now, the graphs are meaningless because the scales constantly shift. If you look at the network usage graph in one second it might have a scale out of 100kbps, and the next second have a scale based on 1mbps! So... is there a registry key or something that will peg the scale of these graphs to logical maximums?

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  • Scene graphs and spatial partitioning structures: What do you really need?

    - by tapirath
    I've been fiddling with 2D games for awhile and I'm trying to go into 3D game development. I thought I should get my basics right first. From what I read scene graphs hold your game objects/entities and their relation to each other like 'a tire' would be the child of 'a vehicle'. It's mainly used for frustum/occlusion culling and minimizing the collision checks between the objects. Spatial partitioning structures on the other hand are used to divide a big game object (like the map) to smaller parts so that you can gain performance by only drawing the relevant polygons and again minimizing the collision checks to those polygons only. Also a spatial partitioning data structure can be used as a node in a scene graph. But... I've been reading about both subjects and I've seen a lot of "scene graphs are useless" and "BSP performance gain is irrelevant with modern hardware" kind of articles. Also some of the game engines I've checked like gameplay3d and jmonkeyengine are only using a scene graph (That also may be because they don't want to limit the developers). Whereas games like Quake and Half-Life only use spatial partitioning. I'm aware that the usage of these structures very much depend on the type of the game you're developing so for the sake of clarity let's assume the game is a FPS like Counter-Strike with some better outdoor environment capabilities (like a terrain). The obvious question is which one is needed and why (considering the modern hardware capabilities). Thank you.

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  • Triangulating a partially triangulated mesh (2D)

    - by teodron
    Referring to the above exhibits, this is the scenario I am working with: starting with a planar graph (in my case, a 2D mesh) with a given triangulation, based on a certain criterion, the graph nodes are labeled as RED and BLACK. (A) a subgraph containing all the RED nodes (with edges between only the directly connected neighbours) is formed (note: although this figure shows a tree forming, it may well happen that the subgraph contain loops) (B) Problem: I need to quickly build a triangulation around the subgraph (e.g. as shown in figure C), but under the constraint that I have to keep the already present edges in the final result. Question: Is there a fast way of achieving this given a partially triangulated mesh? Ideally, the complexity should be in the O(n) class. Some side-remarks: it would be nice for the triangulation algorithm to take into account a certain vertex priority when adding edges (e.g. it should always try to build a "1-ring" structure around the most important nodes first - I can implement iteratively such a routine, but it's O(n^2) ). it would also be nice to reflect somehow the "hop distance" when adding edges: add edges first between the nodes that were "closer" to each other given the start topology. Nevertheless, disregarding the remarks, is there an already known scenario similar to this one where a triangulation is built upon a partially given set of triangles/edges?

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  • Graphical Interface and Object Selection/Manipulation

    - by ToriArendt
    I have a project I want to try to implement, but I'm kind of stuck on how to get started. I know there are probably a lot of resources that I can look at, but I'm really just stuck on what to even search for and where to begin. Basically, I have a program written in Java that separates 3D coordinates from a 3D reconstructed model into different objects. I then want to be able to perform a logistic regression on these objects to determine if they are type A or type B. But first, I need to classify a training set of objects as type A or B by hand. I don't know ANYTHING about graphing or user interfaces in Java, so I have been plotting the coordinates of a given object in MATLAB so that I can visualize the object and assign it a type. Now, as I am trying to make this program more "user friendly" I want to create an interface in Java where I can simply graph all the coordinates of the objects from the entire 3D model (on the same graph). I then want to be able to click on the each object and assign it to be either of type A or type B. I hope this description makes sense and someone can point me in the direction of something that will help me. I'm sorry if some of this terminology is off; I'm a bit new to software development. P.S. If anyone also has some tips on implementing logistic regression in Java, I'm sure I'll need them down the road :).

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  • How can I display the users profile pic using the facebook graph api?

    - by kielie
    Hi, I would like to display the users profile picture inside of my applications canvas page, is there a way to do that using the graph api? I know I can do it using FBML but I would also like to pass the profile pic to a flash game I am making, so I would have to get the profile pic from the api and send it as a variable, here is the code I have thus far, $facebook = new Facebook(array( 'appId' => FACEBOOK_APP_ID, 'secret' => FACEBOOK_SECRET_KEY, 'cookie' => true, 'domain' => 'myurl/facebook-test' )); $session = $facebook->getSession(); $uid = $facebook->getUser(); $me = $facebook->api('/me'); $updated = date("l, F j, Y", strtotime($me['updated_time'])); echo "Hello " . $me['name'] . $me['picture'] . "<br />"; echo "<div style=\"background:url(images/bg.jpg); width:760px; height:630px;\">" . "You last updated your profile on " . $updated . "</div>" . "<br /> your uid is" . $uid; Thanx in advance!

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  • How is this algorithm, for finding maximum path on a Directed Acyclical Graph, called?

    - by Martín Fixman
    Since some time, I'm using an algorithm that runs in complexity O(V + E) for finding maximum path on a Directed Acyclical Graph from point A to point B, that consists on doing a flood fill to find what nodes are accessible from note A, and how many "parents" (edges that come from other nodes) each node has. Then, I do a BFS but only "activating" a node when I already had used all its "parents". queue <int> a int paths[] ; //Number of paths that go to note i int edge[][] ; //Edges of a int mpath[] ; //max path from 0 to i (without counting the weight of i) int weight[] ; //weight of each node mpath[0] = 0 a.push(0) while not empty(a) for i in edge[a] paths[i] += 1 a.push(i) while not empty(a) for i in children[a] mpath[i] = max(mpath[i], mpath[a] + weight[a]) ; paths[i] -= 1 ; if path[i] = 0 a.push(i) ; Is there any special name for this algorithm? I told it to an Informatics professor, he just called it "Maximum Path on a DAG", but it doesn't sound good when you say "I solved the first problem with a Fenwick Tree, the second with Dijkstra, and the third with Maximum Path".

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  • Common and useful Graph functions?

    - by Nazgulled
    Hi, I'm implementing a simple Graph library for my uni project and since this is the first time I'm dealing with graphs, I would like to know which functions you guys consider to be most common and useful for Graph implementations... So far, I have this: graphInitialize() graphInsertVertex() graphRemoveVertex() graphGetVertex() graphGetVertexValue() (not implemented yet, not sure if I'll need it) graphInsertEdge() graphRemoveEdge() graphLinkVertices() (this calls graphInsertEdge twice for bidirectional graph) graphUnlinkVertices() (this calls graphRemoveEdge twice for bidirectional graph) graphDestroy() I know I'm missing a function do determine the shortest path, but I'm leaving that for last... Do you think I'm missing any common/useful function?

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  • How to draw the graph in android based on its height and size

    - by Rakesh
    i want to draw a graph in a area and i used a linear layout as area.i want to set the size of the graph area,which should be compatible to small,medium ,default emulators etc.i need to set the size for graph area,how can i do it in xml file for eg in blackberry we use Display.getWidth();Similar is there way to get the width of the display either programmatically or in xml Regards Rakesh Shankar.p

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  • BFS traversal of directed graph from a given node

    - by p1
    Hi, My understanding of basic BFS traversal for a graph is: BFS { Start from any node . Add it to que. Add it to visited array While(que is not empty) { remove head from queue. Print node; add all unvisited direct subchilds to que; mark them as visited } } However, if we have to traverse a DIRECTED graph from a given node and not all nodes are accessible from the given node [directly or indirectly] how do we use BFS for the same. Can you please explain in this graph as well: a= b = d = e = d a= c = d Here if the starting node is b , we never print a and c. Am I missing something in the algorithm. P.S: I used "HashMap adj = new HashMap();" to create the adjacencey list to store graph Any pointers are greatly appreciated. Thanks.

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  • Plot a graph using .NET

    - by veda
    I need to read some data from an input file and plot a graph based on the inputs... I want to plot a graph using visual C#. Is there any in-built functions to plot a graph in visual C#.. If not, how can I do that..

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  • Creating an adjacency Matrix from a JUNG Graph.

    - by prince
    Graph < Integer, Integer> g = new SparseMultigraph<Integer, Integer>(); g.addVertex(1);g.addVertex(2);g.addVertex(3); g.addEdge(0,1,2 ,EdgeType.DIRECTED);g.addEdge(1,2,3 ,EdgeType.DIRECTED);g.addEdge(2,3,1 ,EdgeType.DIRECTED);g.addEdge(3,1,3 ,EdgeType.DIRECTED); How can I convert this graph into an adjacency matrix taking into consideration that it is a directed graph.

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