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• Small questions on data structure

  - by John Graveston

  Hi, I'm trying to search the parent of a node with Kruskal's algorithm. My program works just fine, but I think I have heard of a method to improve the speed of the algorithm by reconstructing the tree while searching for the parent node and connecting it to the parent node. I'm pretty sure that I've heard of this somewhere, maybe in a lecture. Can anyone refresh my memory? And also, given a number of arrays, when searching for the minimum and the maximum value from a certain section of an array, what is the name of the tree that can calculate the minimum/maximum value from the array by making a binary tree that has the minimum/maximum value of each array in O(log N)?

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• file names based on file content

  - by Mark

  So iow, some algorithm to generate a unique, reasonable length filename based on binary file content. Two files that have the same binary content should have the same name. Obviously there would be limits to this, as presumably you couldn't have unique reasonable length filenames for each of a large set of large files only differing at a handful of bit positions. But presumably there is some heuristic, best approximation to this that for example exploits known attributes of typical image files. If I had the name of some algorithm that does this I can google it and find other approaches as well.

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• question on reverse array

  - by davit-datuashvili

  we know algorithm how reverse array of n integers for (int i=0;i<n/2;i++){ swap(a[i],a[n-1-i]): } is this method better according the speed of algorithm or not because swap using xor is more fast then in other method here is code public class swap { public static void main(String[]args){ int a[]=new int[]{2,4,5,7,8,11,13,12,14,24}; System.out.println(" array at the begining:"); for (int i=0;i<a.length;i++){ System.out.println(a[i]); } for (int j=0;j<a.length/2;j++){ a[j]^=a[a.length-1-j]; a[a.length-1-j]^=a[j]; a[j]^=a[a.length-1-j]; } System.out.println("reversed array:"); for (int j=0;j<a.length;j++){ System.out.println(a[j]); } } } Result: array at the begining: 2 4 5 7 8 11 13 12 14 24 reversed array: 24 14 12 13 11 8 7 5 4 2

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• C# Improved algorithm

  - by generixs

  I have been asked at interview (C# 3.0) to provide a logic to remove a list of items from a list. I responded int[] items={1,2,3,4}; List<int> newList = new List<int>() { 1, 2, 3, 4, 5, 56, 788, 9 }; newList.RemoveAll((int i) => { return items.Contains(i); }); 1) The interviewer replied that the algorithm i had employed will gradually take time if the items grow and asked me to give even better and faster one.What would be the efficient algorithm ? 2) How can i achieve the same using LINQ? 3) He asked me to provide an example for Two-Way-Closure? (General I am aware of closure, what is Two-Way-Closure?, I replied there is no such term exists,but he did not satisfy).

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• How/where to run the algorithm on large dataset?

  - by niko

  I would like to run the PageRank algorithm on graph with 4 000 000 nodes and around 45 000 000 edges. Currently I use neo4j graph databse and classic relational database (postgres) and for software projects I mostly use C# and Java. Does anyone know what would be the best way to perform a PageRank computation on such graph? Is there any way to modify the PageRank algorithm in order to run it at home computer or server (48GB RAM) or is there any useful cloud service to push the data along the algorithm and retrieve the results? At this stage the project is at the research stage so in case of using cloud service if possible, would like to use such provider that doesn't require much administration and service setup, but instead focus just on running the algorith once and get the results without much overhead administration work.

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• Facebook graph api photo upload to a fan page album

  - by kielie

  Hi guys, I have gotten the photo upload function to work with this code, <?php include_once 'facebook-php-sdk/src/facebook.php'; include_once 'config.php';//this file contains the secret key and app id etc... $facebook = new Facebook(array( 'appId' => FACEBOOK_APP_ID, 'secret' => FACEBOOK_SECRET_KEY, 'cookie' => true, 'domain' => 'your callback url goes here' )); $session = $facebook->getSession(); if (!$session) { $url = $facebook->getLoginUrl(array( 'canvas' => 1, 'fbconnect' => 0, 'req_perms'=>'user_photos,publish_stream,offline_access'//here I am requesting the required permissions, it should work with publish_stream alone, but I added the others just to be safe )); echo 'You are not logged in, please <a href="' . $facebook->getLoginUrl() . '">Login</a> to access this application'; } else{ try { $uid = $facebook->getUser(); $me = $facebook->api('/me'); $token = $session['access_token'];//here I get the token from the $session array $album_id = 'the id of the album you wish to upload to eg: 1122'; //upload your photo $file= 'test.jpg'; $args = array( 'message' => 'Photo from application', ); $args[basename($file)] = '@' . realpath($file); $ch = curl_init(); $url = 'https://graph.facebook.com/'.$album_id.'/photos?access_token='.$token; curl_setopt($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); $data = curl_exec($ch); //returns the id of the photo you just uploaded print_r(json_decode($data,true)); } catch(FacebookApiException $e){ echo "Error:" . print_r($e, true); } } ?> I hope this helps, a friend and I smashed our heads against a wall for quite some time to get this working! Anyways, here is my question, how can I upload a image to a fan page? I am struggling to get this working, when I upload the image all I get is the photo id but no photo in the album. So basically, when the user clicks the upload button on our application, I need it to upload the image they created to our fan page's album with them tagged on it. Anyone know how I can accomplish this?

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• MS Chart Control Scale - Line graph show 12 months

  - by Mike

  Hi, On my X Axis, I have months. The chart shows up to 11 points, i.e. Jan - Nov of the same year, but when I add 12 points (Jan - Dec), it will do an auto label thing and change the interval for every 4 months. How can I change the graph so that it shows 12 months before it does the auto labels? Here is the server control code I am currently using. <asp:CHART ID="Chart1" runat="server" BorderColor="181, 64, 1" BorderDashStyle="Solid" BorderWidth="2" Height="296px" ImageLocation="~/TempImages/ChartPic_#SEQ(300,3)" ImageType="Png" Palette="None" Width="700px" BorderlineColor=""> <legends> <asp:Legend BackColor="Transparent" Font="Trebuchet MS, 8pt, style=Bold" IsTextAutoFit="False" Name="Default" Alignment="Center" DockedToChartArea="ChartArea1" Docking="Top" IsDockedInsideChartArea="False" Title="Legend"> </asp:Legend> </legends> <series> <asp:Series BorderColor="180, 26, 59, 105" BorderWidth="2" ChartType="Line" Color="220, 65, 140, 240" MarkerSize="6" Name="Series1" ShadowColor="Black" ShadowOffset="2" XValueType="DateTime" YValueType="Double" LabelFormat="c0" LegendText="Actual" MarkerStyle="Circle"> </asp:Series> <asp:Series BorderColor="180, 26, 59, 105" BorderWidth="2" ChartType="Line" Color="220, 224, 64, 10" MarkerSize="6" Name="Series2" ShadowColor="Black" ShadowOffset="2" XValueType="DateTime" YValueType="Double" LabelFormat="c0" LegendText="Projected" MarkerStyle="Circle"> </asp:Series> <asp:Series BorderColor="180, 26, 59, 105" BorderWidth="2" ChartArea="ChartArea1" ChartType="Line" Legend="Default" Name="Series3" LabelFormat="c0" XValueType="DateTime" YValueType="Double" Color="0, 192, 192" MarkerSize="6" ShadowColor="Black" ShadowOffset="2" LegendText="Actual Credit Limit" MarkerStyle="Circle"> </asp:Series> </series> <chartareas> <asp:ChartArea BackColor="#DEEDF7" BackGradientStyle="TopBottom" BackSecondaryColor="White" BorderColor="64, 64, 64, 64" BorderDashStyle="Solid" Name="ChartArea1" ShadowColor="Transparent"> <area3dstyle inclination="40" isclustered="False" isrightangleaxes="False" lightstyle="Realistic" perspective="9" rotation="25" wallwidth="3" /> <axisy linecolor="64, 64, 64, 64" islabelautofit="False" isstartedfromzero="False"> <LabelStyle Font="Trebuchet MS, 8.25pt, style=Bold" Format="c0" /> <majorgrid linecolor="64, 64, 64, 64" /> </axisy> <axisx linecolor="64, 64, 64, 64" intervaloffsettype="Months" intervaltype="Months" islabelautofit="False" isstartedfromzero="False"> <LabelStyle Font="Trebuchet MS, 8.25pt, style=Bold" Angle="-60" Format="MMM yy" /> <majorgrid linecolor="64, 64, 64, 64" /> </axisx> </asp:ChartArea> </chartareas> </asp:CHART> Thanks.

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• Running a graph returns E_FAIL

  - by Manish

  Hi, I have been struggling for a while now to get my filter graph to run .I am trying to crop a .wmv file into smaller duration .wmv files .It looks quite a simple task I dont know why its is getting so complicated.I follow this Source- SampleGrabber-WMA sf writer. Here is my code IBaseFilter* pASFWriter; ICaptureGraphBuilder2 * pBuilder=NULL; CoCreateInstance(CLSID_CaptureGraphBuilder2,NULL,CLSCTX_INPROC_SERVER,IID_ICaptureGraphBuilder2,(LPVOID*)&pBuilder); pBuilder-SetFiltergraph(pGraphBuilder); pBuilder-SetOutputFileName(&MEDIASUBTYPE_Asf,OUTFILE,&pASFWriter,NULL); IConfigAsfWriter *pConfig=NULL; HRESULT hr80 = pASFWriter-QueryInterface(IID_IConfigAsfWriter, (void**)&pConfig); if (SUCCEEDED(hr80)) { // Configure the ASF Writer filter. pConfig-Release(); } IBaseFilter *pSource=NULL; pGraphBuilder->AddSourceFilter(FILENAME,L"Source",&pSource); IBaseFilter *pGrabberF2=NULL; ISampleGrabber *pGrabber2=NULL; CoCreateInstance(CLSID_SampleGrabber,NULL,CLSCTX_INPROC_SERVER,IID_PPV_ARGS(&pGrabberF2)); pGraphBuilder->AddFilter(pGrabberF2,L"Sample Grabber2"); AM_MEDIA_TYPE mt1; ZeroMemory(&mt1,sizeof(mt1)); mt1.majortype=MEDIATYPE_Video; mt1.subtype=MEDIASUBTYPE_RGB24; pGrabberF2->QueryInterface(IID_ISampleGrabber,(void**)(&pGrabber2)); pGrabber2->SetBufferSamples(TRUE); pGrabber2->SetOneShot(FALSE); pGrabber->SetMediaType(&mt1); pSource->EnumPins(&pEnum2); pEnum2->Next(1,&pPin2,NULL); HRESULT hr108=ConnectFilters(pGraphBuilder,pPin2,pGrabberF2);//Source to Grabber pGrabberF2->EnumPins(&pEnum3); IEnumPins *pEnum4=NULL; pASFWriter->EnumPins(&pEnum4); IPin* pPin4=NULL; while (S_OK==pEnum3->Next(1,&pPin3,NULL)&& S_OK==pEnum4->Next(1,&pPin4,NULL)){ pGraphBuilder->Connect(pPin3,pPin4);//Grabber to FileWriter } pGraphBuilder->RenderFile(FILENAME,NULL);//FILENAME=INPUTFILENAME (.wmv format) pMediaPosition->put_CurrentPosition(start); pMediaPosition->put_StopTime(stop); HRESULT test1=pMediaControl->Run(); All of it runs fine(returns S_OK) .But test1 returns E_FAIL and no file is created.Can somebody help?

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• What Javascript graphing package will let me plot points against a user-selected coordinate system?

  - by wes

  My customer has some specific requirements for a graph to show in our web app. We use HighCharts elsewhere in the app for more traditional graphing, but it doesn't seem to work for this situation. Their requirements: Allow the user to select a background image, set the scale and origin of the coordinate system. We'll graph our points against the user-defined coordinates. Points can be color coded Mouse-over boxes show more detail about the points Support for zooming and panning, scaling the background appropriately Less importantly: Support for drawing vectors off the points Some of this seems basic, but looking around at different graph packages, I was unable to find any with an example of this kind of usage. I've entertained the thought of just hacking it together in canvas myself, but I've never worked with canvas before so I don't think it would be cost effective. The basics of plotting points with a scaled coordinate system against an image background wouldn't be too hard, but the mouse-over details, zooming and panning sound much more daunting to me. More info: Right now we use jQuery, HighCharts, and ExtJS for our app. We tried flot in the past but switched to HighCharts after flot didn't meet our needs.

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• Unable to register achievements

  - by abe

  I've been unable to register any achievements. I keep getting the following: {"error":{"message":"(#3502) Object at achievement URL is not of type game.achievement","type":"OAuthException","code":3502}} When I run my URL through the linter, I get: Open Graph Warnings That Should Be Fixed Inferred Property: The 'og:url' property should be explicitly provided, even if a value can be inferred from other tags. Inferred Property: The 'og:title' property should be explicitly provided, even if a value can be inferred from other tags. Although when I load the URL myself I clearly see those set in the meta tags. My HTML looks like: <html> <head prefix="og: http://ogp.me/ns# fb: http://ogp.me/ns/fb# game: http://ogp.me/ns/game#"> <meta property="fb:app_id" content="<MY_APP_ID>" /> <meta property="og:type" content="game.achievement" /> <meta property="og:url" content="http://<MY_DOMAIN>/ach10.html" /> <meta property="og:title" content="Title" /> <meta property="og:description" content="Description" /> <meta property="og:image" content="http://placekitten.com/g/200/300" /> </head> <body> Hmm.. </body> </html> Also interesting, is the graph API sees it as: { "url": "http://<MY_DOMAIN>/ach10.html", "type": "website", "title": "http://<MY_DOMAIN>/ach10.html", "updated_time": "2012-03-09T19:49:14+0000", "id": "<ID>" } And the scraped URL returns nothing ... anyone have any ideas? I've also tried adding the Game Achievement object in the Open Graph settings and every combination of Sandbox Mode/Social Discovery enabled and disabled.

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• Open source libraries to design directed graphs

  - by Benjamin

  Hi all, I'm going to need to write a software that takes a list of persons and connects them together in a directed-graph-like manner. The GUI aspect of the whole project is very important. The graph must allow a lot of interaction. Such as selecting several people and hiding the others, moving them around. Additionally, the software will need to be able to provide other kind of GUI-features such as several tabs, text boxes etc. The application must be quite performant. As in, it must be able to handle hundreds if not thousands of widgets. Hence, I would like to know which open source libraries (at this point the programming language they are written in does not matter - I just want an overview of everything good that is out there) would allow me to develop such piece of software? What would you recommend? Thanks for that. Edit: Could you please also link to tutorials explaining how I could program a GUI that can interact with the generated graph? For example mouse events.

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• Increasing figure size in Matplotlib

  - by Anirudh

  I am trying to plot a graph from a distance matrix. The code words fine and gives me a image in 800 * 600 pixels. The image being too small, All the nodes are packed together. I want increase the size of the image. so I added the following line to my code - figure(num=None, figsize=(10, 10), dpi=80, facecolor='w', edgecolor='k') After this all I get is a blank 1000 * 1000 image file. My overall code - import networkx as nx import pickle import matplotlib.pyplot as plt print "Reading from pickle." p_file = open('pickles/names') Names = pickle.load(p_file) p_file.close() p_file = open('pickles/distance') Dist = pickle.load(p_file) p_file.close() G = nx.Graph() print "Inserting Nodes." for n in Names: G.add_node(n) print "Inserting Edges." for i in range(601): for j in range(601): G.add_edge(Names[i],Names[j],weight=Dist[i][j]) print "Drawing Graph." nx.draw(G) print "Saving Figure." #plt.figure(num=None, figsize=(10, 10)) plt.savefig('new.png') print "Success!"

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• How can I estimate the entropy of a password?

  - by Wug

  Having read various resources about password strength I'm trying to create an algorithm that will provide a rough estimation of how much entropy a password has. I'm trying to create an algorithm that's as comprehensive as possible. At this point I only have pseudocode, but the algorithm covers the following: password length repeated characters patterns (logical) different character spaces (LC, UC, Numeric, Special, Extended) dictionary attacks It does NOT cover the following, and SHOULD cover it WELL (though not perfectly): ordering (passwords can be strictly ordered by output of this algorithm) patterns (spatial) Can anyone provide some insight on what this algorithm might be weak to? Specifically, can anyone think of situations where feeding a password to the algorithm would OVERESTIMATE its strength? Underestimations are less of an issue. The algorithm: // the password to test password = ? length = length(password) // unique character counts from password (duplicates discarded) uqlca = number of unique lowercase alphabetic characters in password uquca = number of uppercase alphabetic characters uqd = number of unique digits uqsp = number of unique special characters (anything with a key on the keyboard) uqxc = number of unique special special characters (alt codes, extended-ascii stuff) // algorithm parameters, total sizes of alphabet spaces Nlca = total possible number of lowercase letters (26) Nuca = total uppercase letters (26) Nd = total digits (10) Nsp = total special characters (32 or something) Nxc = total extended ascii characters that dont fit into other categorys (idk, 50?) // algorithm parameters, pw strength growth rates as percentages (per character) flca = entropy growth factor for lowercase letters (.25 is probably a good value) fuca = EGF for uppercase letters (.4 is probably good) fd = EGF for digits (.4 is probably good) fsp = EGF for special chars (.5 is probably good) fxc = EGF for extended ascii chars (.75 is probably good) // repetition factors. few unique letters == low factor, many unique == high rflca = (1 - (1 - flca) ^ uqlca) rfuca = (1 - (1 - fuca) ^ uquca) rfd = (1 - (1 - fd ) ^ uqd ) rfsp = (1 - (1 - fsp ) ^ uqsp ) rfxc = (1 - (1 - fxc ) ^ uqxc ) // digit strengths strength = ( rflca * Nlca + rfuca * Nuca + rfd * Nd + rfsp * Nsp + rfxc * Nxc ) ^ length entropybits = log_base_2(strength) A few inputs and their desired and actual entropy_bits outputs: INPUT DESIRED ACTUAL aaa very pathetic 8.1 aaaaaaaaa pathetic 24.7 abcdefghi weak 31.2 H0ley$Mol3y_ strong 72.2 s^fU¬5ü;y34G< wtf 88.9 [a^36]* pathetic 97.2 [a^20]A[a^15]* strong 146.8 xkcd1** medium 79.3 xkcd2** wtf 160.5 * these 2 passwords use shortened notation, where [a^N] expands to N a's. ** xkcd1 = "Tr0ub4dor&3", xkcd2 = "correct horse battery staple" The algorithm does realize (correctly) that increasing the alphabet size (even by one digit) vastly strengthens long passwords, as shown by the difference in entropy_bits for the 6th and 7th passwords, which both consist of 36 a's, but the second's 21st a is capitalized. However, they do not account for the fact that having a password of 36 a's is not a good idea, it's easily broken with a weak password cracker (and anyone who watches you type it will see it) and the algorithm doesn't reflect that. It does, however, reflect the fact that xkcd1 is a weak password compared to xkcd2, despite having greater complexity density (is this even a thing?). How can I improve this algorithm? Addendum 1 Dictionary attacks and pattern based attacks seem to be the big thing, so I'll take a stab at addressing those. I could perform a comprehensive search through the password for words from a word list and replace words with tokens unique to the words they represent. Word-tokens would then be treated as characters and have their own weight system, and would add their own weights to the password. I'd need a few new algorithm parameters (I'll call them lw, Nw ~= 2^11, fw ~= .5, and rfw) and I'd factor the weight into the password as I would any of the other weights. This word search could be specially modified to match both lowercase and uppercase letters as well as common character substitutions, like that of E with 3. If I didn't add extra weight to such matched words, the algorithm would underestimate their strength by a bit or two per word, which is OK. Otherwise, a general rule would be, for each non-perfect character match, give the word a bonus bit. I could then perform simple pattern checks, such as searches for runs of repeated characters and derivative tests (take the difference between each character), which would identify patterns such as 'aaaaa' and '12345', and replace each detected pattern with a pattern token, unique to the pattern and length. The algorithmic parameters (specifically, entropy per pattern) could be generated on the fly based on the pattern. At this point, I'd take the length of the password. Each word token and pattern token would count as one character; each token would replace the characters they symbolically represented. I made up some sort of pattern notation, but it includes the pattern length l, the pattern order o, and the base element b. This information could be used to compute some arbitrary weight for each pattern. I'd do something better in actual code. Modified Example: Password: 1234kitty$$$$$herpderp Tokenized: 1 2 3 4 k i t t y $ $ $ $ $ h e r p d e r p Words Filtered: 1 2 3 4 @W5783 $ $ $ $ $ @W9001 @W9002 Patterns Filtered: @P[l=4,o=1,b='1'] @W5783 @P[l=5,o=0,b='$'] @W9001 @W9002 Breakdown: 3 small, unique words and 2 patterns Entropy: about 45 bits, as per modified algorithm Password: correcthorsebatterystaple Tokenized: c o r r e c t h o r s e b a t t e r y s t a p l e Words Filtered: @W6783 @W7923 @W1535 @W2285 Breakdown: 4 small, unique words and no patterns Entropy: 43 bits, as per modified algorithm The exact semantics of how entropy is calculated from patterns is up for discussion. I was thinking something like: entropy(b) * l * (o + 1) // o will be either zero or one The modified algorithm would find flaws with and reduce the strength of each password in the original table, with the exception of s^fU¬5ü;y34G<, which contains no words or patterns.

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• Clustered Graphs Visualization Techniques

  - by jameszhao00

  I need to visualize a relatively large graph (6K nodes, 8K edges) that has the following properties: Distinct Clusters. Approximately 50-100 Nodes per cluster and moderate interconnectivity at the cluster level Minimal (5-10 inter-cluster edges per cluster) interconnectivity between clusters Let global edge overlap = The edge overlaps caused by directly visualizing a graph of Clusters = {A, B, C, D, E}, Edges = {Pentagram of those clusters, which is non-planar by the way and will definitely generate edge overlap if you draw it out directly} Let Local Edge Overlap = the above but { A, B, C, D, E } are just nodes. I need to visualize graphs with the above in a way that satisfies the following requirements No global edge overlap (i.e. edge overlaps caused by inter-cluster properties is not okay) Local edge overlap within a cluster is fine Anyone have thoughts on how to best visualize a graph with the requirements above? One solution I've come up with to deal with the global edge overlap is to make sure a cluster A can only have a max of 1 direct edge to another cluster (B) during visualization. Any additional inter-cluster edges between cluster A - C, A - D, ... are disconnected and additional node/edges A - A_C, C - C_A, A - A_D, D - D_A... are created. Anyone have any thoughts?

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• Determining the maximum stack depth

  - by Joa Ebert

  Imagine I have a stack-based toy language that comes with the operations Push, Pop, Jump and If. I have a program and its input is the toy language. For instance I get the sequence Push 1 Push 1 Pop Pop In that case the maximum stack would be 2. A more complicated example would use branches. Push 1 Push true If .success Pop Jump .continue .success: Push 1 Push 1 Pop Pop Pop .continue: In this case the maximum stack would be 3. However it is not possible to get the maximum stack by walking top to bottom as shown in this case since it would result in a stack-underflow error actually. CFGs to the rescue you can build a graph and walk every possible path of the basic blocks you have. However since the number of paths can grow quickly for n vertices you get (n-1)! possible paths. My current approach is to simplify the graph as much as possible and to have less possible paths. This works but I would consider it ugly. Is there a better (read: faster) way to attack this problem? I am fine if the algorithm produces a stack depth that is not optimal. If the correct stack size is m then my only constraint is that the result n is n = m. Is there maybe a greedy algorithm available that would produce a good result here?

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• How should I generate the partitions / pairs for the Chinese Postman problem?

  - by Simucal

  I'm working on a program for class that involves solving the Chinese Postman problem. Our assignment only requires us to write a program to solve it for a hard-coded graph but I'm attempting to solve it for the general case on my own. The part that is giving me trouble is generating the partitions of pairings for the odd vertices. For example, if I had the following labeled odd verticies in a graph: 1 2 3 4 5 6 I need to find all the possible pairings / partitions I can make with these vertices. I've figured out I'll have i paritions given: n = num of odd verticies k = n / 2 i = ((2k)(2k-1)(2k-2)...(k+1))/2 So, given the 6 odd verticies above, we will know that we need to generate i = 15 partitions. The 15 partions would look like: 1 2 3 4 5 6 1 2 3 5 4 6 1 2 3 6 4 5 ... 1 6 ... Then, for each partition, I take each pair and find the shortest distance between them and sum them for that partition. The partition with the total smallest distance between its pairs is selected, and I then double all the edges between the shortest path between the odd vertices (found in the selected partition). These represent the edges the postman will have to walk twice. At first I thought I had worked out an appropriate algorithm for generating these partitions / pairs but it is flawed. I found it wasn't a simple permutation/combination problem. Does anyone who has studied this problem before have any tips that can help point me in the right direction for generating these partitions?

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• Classical task-scheduling assignment

  - by Bruno

  I am working on a flight scheduling app (disclaimer: it's for a college project, so no code answers, please). Please read this question w/ a quantum of attention before answering as it has a lot of peculiarities :( First, some terminology issues: You have planes and flights, and you have to pair them up. For simplicity's sake, we'll assume that a plane is free as soon as the flight using it prior lands. Flights are seen as tasks: They have a duration They have dependencies They have an expected date/time for beginning Planes can be seen as resources to be used by tasks (or flights, in our terminology). Flights have a specific type of plane needed. e.g. flight 200 needs a plane of type B. Planes obviously are of one and only one specific type, e.g., Plane Airforce One is of type C. A "project" is the set of all the flights by an airline in a given time period. The functionality required is: Finding the shortest possible duration for a said project The earliest and latest possible start for a task (flight) The critical tasks, with basis on provided data, complete with identifiers of preceding tasks. Automatically pair up flights and planes, so as to get all flights paired up with a plane. (Note: the duration of flights is fixed) Get a Gantt diagram with the projects scheduling, in which all flights begin as early as possible, showing all previously referred data graphically (dependencies, time info, etc.) So the questions is: How in the world do I achieve this? Particularly: We are required to use a graph. What do the graph's edges and nodes respectively symbolise? Are we required to discard tasks to achieve the critical tasks set? If you could also recommend some algorithms for us to look up, that'd be great.

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• Blueprints for Oracle NoSQL Database

  - by dan.mcclary

  I think that some of the most interesting analytic problems are graph problems.  I'm always interested in new ways to store and access graphs.  As such, I really like the work being done by Tinkerpop to create Open Source Software to make property graphs more accessible over a wide variety of datastores.  Since key-value stores like Oracle NoSQL Database are well-suited to storing property graphs, I decided to extend the Blueprints API to work with it.  Below I'll discuss some of the implementation details, but you can check out the finished product here: http://github.com/dwmclary/blueprints-oracle-nosqldb.  What's in a Property Graph?  In the most general sense, a graph is just a collection of vertices and edges.  Vertices and edges can have properties: weights, names, or any number of other traits.  In an undirected graph, edges connect vertices without direction.  A directed graph specifies that all edges have a head and a tail --- a direction.  A multi-graph allows multiple edges to connect two vertices.  A "property graph" encompasses all of these traits. Key-Value Stores for Property Graphs Key-Value stores like Oracle NoSQL Database tend to be ideal for implementing property graphs.  First, if any vertex or edge can have any number of traits, we can treat it as a hash map.  For example: Vertex["name"] = "Mary" Vertex["age"] = 28 Vertex["ID"] = 12345  and so on.  This is a natural key-value relationship: the key "name" maps to the value "Mary."  Moreover if we maintain two hash maps, one for vertex objects and one for edge objects, we've essentially captured the graph.  As such, any scalable key-value store is fertile ground for planting graphs. Oracle NoSQL Database as a Scalable Graph Database While Oracle NoSQL Database offers useful features like tunable consistency, what lends it to storing property graphs is the storage guarantees around its key structure.  Keys in Oracle NoSQL Database are divided into two parts: a major key and a minor key.  The storage guarantee is simple.  Major keys will be distributed across storage nodes, which could encompass a large number of servers.  However, all minor keys which are children of a given major key are guaranteed to be stored on the same storage node.  For example, the vertices: /Personnel/Vertex/1  and /Personnel/Vertex/2 May be stored on different servers, but /Personnel/Vertex/1-/name and  /Personnel/Vertex/1-/age will always be on the same server.  This means that we can structure our graph database such that retrieving all the properties for a vertex or edge requires I/O from only a single storage node.  Moreover, Oracle NoSQL Database provides a storeIterator which allows us to store a huge number of vertices and edges in a scalable fashion.  By storing the vertices and edges as major keys, we guarantee that they are distributed evenly across all storage nodes.  At the same time we can use a partial major key to iterate over all the vertices or edges (e.g. we search over /Personnel/Vertex to iterate over all vertices). Fork It! The Blueprints API and Oracle NoSQL Database present a great way to get started using a scalable key-value database to store and access graph data.  However, a graph store isn't useful without a good graph to work on.  I encourage you to fork or pull the repository, store some data, and try using Gremlin or any other language to explore.

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• Munin Aggregated Graphs Configuration Error

  - by Sparsh Gupta

  I tried making some Munin Aggregated graphs but somehow I am unable to make the configuration work. I think I have followed the instructions but since its not working, I would love some assistance or guidance as to what I am doing wrong. I want to Aggregate (sum) the total number of requests / second all my nginx servers are doing combined together. The configuration looks like [TRAFFIC.AGGREGATED] update no requests.graph_title nGinx requests requests.graph_vlabel nGinx requests per second requests.draw LINE2 requests.graph_args --base 1000 requests.graph_category nginx requests.label req/sec requests.type DERIVE requests.min 0 requests.graph_order output requests.output.sum \ lb1.visualwebsiteoptimizer.com:nginx_request_lb1.visualwebsiteoptimizer.com_request.request \ lb3.visualwebsiteoptimizer.com:nginx_request_lb2.visualwebsiteoptimizer.com_request.request \ lb3.visualwebsiteoptimizer.com:nginx_request_lb3.visualwebsiteoptimizer.com_request.request The munin graph I want to aggregate is http://exchange.munin-monitoring.org/plugins/nginx_request/details Thanks Sparsh Gupta

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• vps like [load] graphs

  - by foober

  I investigated a couple of tools but they were really annoying and not polished. kSar for exampe is supposed to graph sar output, but it doesn't work. There's a perl script around (sar2rrd) that's supposed to convert sar output in rrd format and generate graphs. Doesn't work. (at least it doesn't like the output of "atsar" as per debian/ubuntu package). Tried munin but it wants to mess with http servers, and for some reason it didn't really work, too. It displayed errors in the webpage generated by the http server it put on port 4949. So, is there a simple install and forget tool to generate daily load,cpu,memory,network graphs? It seems strange to me that this problem has not been solved, maybe I'm looking in the wrong places

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• Munin help... configure graphs to show different time periods

  - by PiZzL3

  I'm running a server with Munin installed through WHM cPanel. I've been googling around and I can't seem to find out how to do the following: A: Change a graph to show a different time period (currently I can only view, day, week, month, year). I would like to possibly view per minute, per hour... or specific intervals such as per 30 minutes, per 4 hours, etc... B(optional, but preferred): Add new graphs with the above criteria(A) above. I am a novice with all things that will possibly be required to do this (such as ssh). I wish I could just go edit a php file as I'm highly experienced in that subject. Thanks for any help!

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• Edges on polygon outlines not always correct

  - by user146780

  I'm using the algorithm below to generate quads which are then rendered to make an outline like this http://img810.imageshack.us/img810/8530/uhohz.png The problem as seen on the image, is that sometimes the lines are too thin when they should always be the same width. My algorithm finds the 4 verticies for the first one then the top 2 verticies of the next ones are the bottom 2 of the previous. This creates connected lines, but it seems to not always work. How could I fix this? This is my algorithm: void OGLENGINEFUNCTIONS::GenerateLinePoly(const std::vector<std::vector<GLdouble>> &input, std::vector<GLfloat> &output, int width) { output.clear(); if(input.size() < 2) { return; } int temp; float dirlen; float perplen; POINTFLOAT start; POINTFLOAT end; POINTFLOAT dir; POINTFLOAT ndir; POINTFLOAT perp; POINTFLOAT nperp; POINTFLOAT perpoffset; POINTFLOAT diroffset; POINTFLOAT p0, p1, p2, p3; for(unsigned int i = 0; i < input.size() - 1; ++i) { start.x = static_cast<float>(input[i][0]); start.y = static_cast<float>(input[i][1]); end.x = static_cast<float>(input[i + 1][0]); end.y = static_cast<float>(input[i + 1][1]); dir.x = end.x - start.x; dir.y = end.y - start.y; dirlen = sqrt((dir.x * dir.x) + (dir.y * dir.y)); ndir.x = static_cast<float>(dir.x * 1.0 / dirlen); ndir.y = static_cast<float>(dir.y * 1.0 / dirlen); perp.x = dir.y; perp.y = -dir.x; perplen = sqrt((perp.x * perp.x) + (perp.y * perp.y)); nperp.x = static_cast<float>(perp.x * 1.0 / perplen); nperp.y = static_cast<float>(perp.y * 1.0 / perplen); perpoffset.x = static_cast<float>(nperp.x * width * 0.5); perpoffset.y = static_cast<float>(nperp.y * width * 0.5); diroffset.x = static_cast<float>(ndir.x * 0 * 0.5); diroffset.y = static_cast<float>(ndir.y * 0 * 0.5); // p0 = start + perpoffset - diroffset //p1 = start - perpoffset - diroffset //p2 = end + perpoffset + diroffset // p3 = end - perpoffset + diroffset p0.x = start.x + perpoffset.x - diroffset.x; p0.y = start.y + perpoffset.y - diroffset.y; p1.x = start.x - perpoffset.x - diroffset.x; p1.y = start.y - perpoffset.y - diroffset.y; if(i > 0) { temp = (8 * (i - 1)); p2.x = output[temp + 2]; p2.y = output[temp + 3]; p3.x = output[temp + 4]; p3.y = output[temp + 5]; } else { p2.x = end.x + perpoffset.x + diroffset.x; p2.y = end.y + perpoffset.y + diroffset.y; p3.x = end.x - perpoffset.x + diroffset.x; p3.y = end.y - perpoffset.y + diroffset.y; } output.push_back(p2.x); output.push_back(p2.y); output.push_back(p0.x); output.push_back(p0.y); output.push_back(p1.x); output.push_back(p1.y); output.push_back(p3.x); output.push_back(p3.y); } } Thanks

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• How can I improve my isometric tile-picking algorithm?

  - by Cypher

  I've spent the last few days researching isometric tile-picking algorithms (converting screen-coordinates to tile-coordinates), and have obviously found a lot of the math beyond my grasp. I have come fairly close and what I have is workable, but I would like to improve on this algorithm as it's a little off and seems to pick down and to the right of the mouse pointer. I've uploaded a video to help visualize the current implementation: http://youtu.be/EqwWcq1zuaM My isometric rendering algorithm is based on what is found at this stackoverflow question's answer, with the exception that my x and y axis' are inverted (x increased down-right, while y increased up-right). Here is where I am converting from screen to tiles: // these next few lines convert the mouse pointer position from screen // coordinates to tile-grid coordinates. cameraOffset captures the current // mouse location and takes into consideration the camera's position on screen. System.Drawing.Point cameraOffset = new System.Drawing.Point( 0, 0 ); cameraOffset.X = mouseLocation.X + (int)camera.Left; cameraOffset.Y = ( mouseLocation.Y + (int)camera.Top ); // the camera-aware mouse coordinates are then further converted in an attempt // to select only the "tile" portion of the grid tiles, instead of the entire // rectangle. this algorithm gets close, but could use improvement. mouseTileLocation.X = ( cameraOffset.X + 2 * cameraOffset.Y ) / Global.TileWidth; mouseTileLocation.Y = -( ( 2 * cameraOffset.Y - cameraOffset.X ) / Global.TileWidth ); Things to make note of: mouseLocation is a System.Drawing.Point that represents the screen coordinates of the mouse pointer. cameraOffset is the screen position of the mouse pointer that includes the position of the game camera. mouseTileLocation is a System.Drawing.Point that is supposed to represent the tile coordinates of the mouse pointer. If you check out the above link to youtube, you'll notice that the picking algorithm is off a bit. How can I improve on this?

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• Sorting tasks to assign

  - by Diego

  I've got a problem that I don't know where to start. I'd realy appreciate some help. The problem: I have several T task that must be done in D days by just 1 employee (let's forget using several resources right now). Each task can be done in some times (not all tasks can be done all time). e.g.: If my employee starts working at 8 o'clock and one task is "call a client". Maybe the client office opens at 9 o'clock. Also each task has a duration (really estimated). It is supposed that the D days are enough to do all task. I've to sort the tasks to the employee. e.g.: at monday 8:00 do task 7, then at 9:30 starts with task 2. In the example task 7 duration would be 1 and a half hour. Thanks for the help! Diego PD: If someone has a way to make this and it is not an algorithm never minds, please answer and I'll manage to think the algorithm. I just don't know how to face the problem. Edit Would Project be usefull? Edit 2 Tasks / Jobs dependency is NOT required

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• Programmatically creating vector arrows in KML

  - by mettadore

  Does anyone have any practical examples of programmatically drawing icons as vectors in KML? Specifically, I have data with a magnitude and an azimuth at given coordinates, and I would like to have icons (or another graphical element) generated based on these values. Some thoughts on how I might approach it: Image directory (a brute force way): Make an image director of 360 different image files (probably batch rotate a single image) each pointing in a cooresponding azimuth. I've seen things like "Excel to KML," but am looking for code that I can use within a program, rather than a web utility. Issue: Arrow does not contain magnitude context, so that would have to be a label. I'd rather dynamically lengthen the arrow. Line creation in KML: Perhaps create a formula that creates a line with the origin at the coordinate points, with the length of the line proportional to the magnitute, and angled according to azimuth. There would then be two more lines, perhaps 30 degrees or so extending from the end of the previous line to make the arrow head. Issues: Not a separate image icon, so not sure how it would work in KML. Also not sure how easy it would be to generate this algorithm. Separate image generation: Perhaps create a PHP file that uses imagemagick or something similar to dynamically generate a .png file in a similar method to the above, and then link to the icon using the URI "domain.tld/imagegen.php?magnitude=magvalue&azimuth=azmvalue". Issue: Still have the problem of actually writing the algorithm for image generation. So, the question: has anyone else come up with solutions for programmatic vector (rather than merely arrow) generation?

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