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  • how to work with strings and integers as bit strings in python?

    - by Manuel
    Hello! I'm developing a Genetic Algorithm in python were chromosomes are composed of strings and integers. To apply the genetic operations, I want to convert these groups of integers and strings into bit strings. For example, if one chromosome is: ["Hello", 4, "anotherString"] I'd like it to become something like: 0100100100101001010011110011 (this is not actual translation). So... How can I do this? Chromosomes will contain the same amount of strings and integers, but this numbers can vary from one algorithm run to another. To be clear, what I want to obtain is the bit representation of each element in the chromosome concatenated. If you think this would not be the best way to apply genetic operators (such as mutation and simple crossover) just tell me! I'm open to new ideas. Thanks a lot! Manuel

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  • How to "smart resize" a displayed image to original aspect ratio

    - by Paul Sasik
    I have an application in which end-users can size and position images in a designer. Since the spec calls for the image to be "stretched" to the containing control, the end user can end up with an awkwardly stretched image. To help the user with image sizing I am thinking of implementing a smart resizer function which would allow the the user to easily fix the aspect ratio of the picture so that it no longer appears stretched. The quick way to solve this is to actually provide two options: 1) scale from width 2) scale from height. The user chooses the method and the algorithm adjusts the size of the picture by using the original aspect ratio. For example: A picture is displayed as 200x200 on the designer but the original image is 1024x768 pixels. The user chooses "Smart Size from width" and the new size becomes ~200x150 since the original aspect ratio is ~1.333 That's OK, but how could I make the algorithm smarter and not bother the user by asking which dimension the recalculation should be based on?

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  • Sum of path products in DAG

    - by Jules
    Suppose we have a DAG with edges labeled with numbers. Define the value of a path as the product of the labels. For each (source,sink)-pair I want to find the sum of the values of all the paths from source to sink. You can do this in polynomial time with dynamic programming, but there are still some choices that can be made in how you decompose the problem. In my case I have one DAG that has to be evaluated repeatedly with different labelings. My question is: for a given DAG, how can we pre-compute a good strategy for computing these values for different labelings repeatedly. It would be nice if there was an algorithm that finds an optimal way, for example a way that minimizes the number of multiplications. But perhaps this is too much to ask, I would be very happy with an algorithm that just gives a good decomposition.

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  • Most useful parallel programming algorithm?

    - by Zubair
    I recenty asked a question about parallel programming algorithms which was closed quite fast due to my bad ability to communicate my intent: http://stackoverflow.com/questions/2407631/what-is-the-most-useful-parallel-programming-algorithm-closed I had also recently asked another question, specifically: http://stackoverflow.com/questions/2407493/is-mapreduce-such-a-generalisation-of-another-programming-principle/2407570#2407570 The other question was specifically about map reduce and to see if mapreduce was a more specific version of some other concept in parallel programming. This question (about a useful parallel programming algorithm) is more about the whole series of algorithms for parallel programming. You will have to excuse me though as I am quite new to parallel programming, so maybe MapReduce or something that is a more general form of mapreduce is the "only" parallel programming construct which is available, in which case I apologise for my ignorance

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  • Which method should I use ?

    - by Ivan
    I want to do this exercise but I don't know exactly which method should I use for an exercise like this and what data will I use to test the algorithm. The driving distance between Perth and Adelaide is 1996 miles. On the average, the fuel consumption of a 2.0 litre 4 cylinder car is 8 litres per 100 kilometres. The fuel tank capacity of such a car is 60 litres. Design and implement a JAVA program that prompts for the fuel consumption and fuel tank capacity of the aforementioned car. The program then displays the minimum number of times the car’s fuel tank has to be filled up to drive from Perth to Adelaide. Note that 62 miles is equal to 100 kilometres. What data will you use to test that your algorithm works correctly?

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  • What is the result of X(X,X)? [closed]

    - by Sorush Rabiee
    A friend who studies pure mathematics ask me to think about the following problem. Suppose that there is an algorithm named X that has 2 inputs: A and a_1...a_n, where 'A' stands for an arbitary algorithm and 'a_1..a_n' are inputs of A. X receives A and its inputs and returns true if A with a_1..a_n could be terminated, and false if A with a_1..a_n inputs fall into an infinite loop (never ends). Like this: A(n): while(n<5): write "I'm immortal!" and the result of X(A,6) is true and X(A,2) is false. So what is the result of X(X,X)? Also, do you know who was the first to introduce this problem?

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  • How to detect generation loss of a transcoded audio.

    - by The Rook
    Lets say you have a 96 kbit mp3 and you Transcode the file into a 320 kbit mp3. How could you programmatically detect the original bit rate or quality? Generation loss is created because each time a lossy algorithm is applied new information will be deemed "unnecessary" and is discarded. How could an algorithm use this property to detect the transcoding of audio. 128 kbps LAME mp3 transcoded to 320 kbps LAME mp3 (I Feel You, Depeche Mode) 10.8 MB. This image was taken from the bottom of this site. The 2 tracks above look nearly identical, but the difference is enough to support this argument.

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  • What are some good algorithms for drawing lines between graph nodes?

    - by ApplePieIsGood
    What I'm specifically grappling with is not just the layout of a graph, but when a user selects a graph node and starts to drag it around the screen area, the line has to constantly be redrawn to reflect what it would look like if the user were to release the node. I suppose this is part of the layout algorithm? Also some applications get a bit fancy and don't simply draw the line in a nice curvy way, but also bend the line around the square shaped node in almost right angles. See attached image and keep in mind that as a node is dragged, the line is drawn as marching ants, and re-arranged nicely, while retaining its curved style.

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  • What container is easiest for combining JPEGS and MP3s as video?

    - by Ole Jak
    So I have N (for example, 1000) JPEG frames and 10*N ( for example, 100) seconds of MP3 sound. I need some container for joining them into one video file (at 10 frames/second) (popular containers like FLV or AVI or MOV are better). So what I need is an algorithm or code example of combining my data into some popular format. The code example should be in some language like C#, Java, ActionScript or PHP. The algorithm should be theoretically implementable with ActionScript or PHP. Can any one, please help me with that?

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  • Segmenting a double array of labels

    - by Ami
    The Problem: I have a large double array populated with various labels. Each element (cell) in the double array contains a set of labels and some elements in the double array may be empty. I need an algorithm to cluster elements in the double array into discrete segments. A segment is defined as a set of pixels that are adjacent within the double array and one label that all those pixels in the segment have in common. (Diagonal adjacency doesn't count and I'm not clustering empty cells). |-------|-------|------| | Jane | Joe | | | Jack | Jane | | |-------|-------|------| | Jane | Jane | | | | Joe | | |-------|-------|------| | | Jack | Jane | | | Joe | | |-------|-------|------| In the above arrangement of labels distributed over nine elements, the largest cluster is the “Jane” cluster occupying the four upper left cells. What I've Considered: I've considered iterating through every label of every cell in the double array and testing to see if the cell-label combination under inspection can be associated with a preexisting segment. If the element under inspection cannot be associated with a preexisting segment it becomes the first member of a new segment. If the label/cell combination can be associated with a preexisting segment it associates. Of course, to make this method reasonable I'd have to implement an elaborate hashing system. I'd have to keep track of all the cell-label combinations that stand adjacent to preexisting segments and are in the path of the incrementing indices that are iterating through the double array. This hash method would avoid having to iterate through every pixel in every preexisting segment to find an adjacency. Why I Don't Like it: As is, the above algorithm doesn't take into consideration the case where an element in the double array can be associated with two unique segments, one in the horizontal direction and one in the vertical direction. To handle these cases properly, I would need to implement a test for this specific case and then implement a method that will both associate the element under inspection with a segment and then concatenate the two adjacent identical segments. On the whole, this method and the intricate hashing system that it would require feels very inelegant. Additionally, I really only care about finding the large segments in the double array and I'm much more concerned with the speed of this algorithm than with the accuracy of the segmentation, so I'm looking for a better way. I assume there is some stochastic method for doing this that I haven't thought of. Any suggestions?

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  • What is result of X(X,X)?

    - by Sorush Rabiee
    a friend who studies pure mathematics ask me to think about this problem: suppose that there is an algorithm named X that have 2 inputs: A and a_1...a_n, 'A' stands for an arbitary algorithm and 'a_1..a_n' are inputs of A. X recieves A and its inputs and returns true if A with a_1..a_n couold be terminated, and false if A with a_1..a_n inputs fall into infty loop (never ends). like this: A(n): while(n<5): write "I'm immortal!" and result of X(A,6) is true and X(A,2) is false. so what is the result of X(X,X)? ...and do you know who introduced this problem first time?

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  • HPC (mainly on Java)

    - by Insectatorious
    I'm looking for some way of using the number-crunching ability of a GPU (with Java perhaps?) in addition to using the multiple cores that the target machine has. I will be working on implementing (at present) the A* Algorithm but in the future I hope to replace it with a Genetic Algorithm of sorts. I've looked at Project Fortress but as I'm building my GUI in JavaFX, I'd prefer not to stray too far from a JVM. Of course, should no feasible solution be available, I will migrate to the easiest solution to implement.

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  • What is the fastest way to compare two list of items?

    - by edude05
    I have two folders with approximately 10,000 files each. I'd like to write a script or program that can tell me if these folders are in sync and then tell me what files are missing from each to make them in sync. Therefore, after generating a list of files, what is the fastest algorithm to sort them for unique files? What I'm thinking right now is comparing the first file on each list then if they are different remove one until they are the same, then remove both from the list (because they are not unique.) Is there a faster algorithm then this?

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  • How do I check the validity of the Canadian Social Insurance Number in C#?

    - by user518307
    I've been given the assignment to write an algorithm in C# that checks the validity of a Canadian Social Insurance Number (SIN). Here are the steps to validate a SIN. Given an example Number: 123 456 782 Remove the check digit (the last digit): 123456782 Extract the even digits (2,4,6,8th digith): 12345678 Double them: 2 4 6 8 | | | | v v v v 4 8 12 16 Add the digits together: 4+8+1+2+1+6 = 22 Add the Odd placed digits: 1+3+5+7 = 16 Total : 38 Validity Algorithm If the total is a multiple of 10, the check digit should be zero. Otherwise, Subtract the Total from the next highest multiple of 10 (40 in this case) The check digit for this SIN must be equal to the difference of the number and the totals from earlier (in this case, 40-38 = 2; check digit is 2, so the number is valid) I'm lost on how to actually implement this in C#, how do I do this?

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  • Tag/Keyword based recommendation

    - by Hellnar
    Hello I am wondering what algorithm would be clever to use for a tag driven e-commerce enviroment: Each item has several tags. IE: Item name: "Metallica - Black Album CD", Tags: "metallica", "black-album", "rock", "music" Each user has several tags and friends(other users) bound to them. IE: Username: "testguy", Interests: "python", "rock", "metal", "computer-science" Friends: "testguy2", "testguy3" I need to generate recommendations to such users by checking their interest tags and generating recommendations in a sophisticated way. Ideas: A Hybrid recommendation algorithm can be used as each user has friends.(mixture of collaborative + context based recommendations). Maybe using user tags, similar users (peers) can be found to generate recommendations. Maybe directly matching tags between users and items via tags. Any suggestion is welcome. Any python based library is also welcome as I will be doing this experimental engine on python language.

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  • Nesting Patterns Algorithms / Cutting Waste Problem

    - by WedTM
    First off, I'd like to say that I'm already looking into the "Cutting Stock Problem" algorithm, however I feel that I need a bit more clarification, and possibly some help with some of the math (Not my strong point). What I need to do is have an offset pattern that causes the circle to fit in the crevasse created by having the two circular dies sitting next to each other on the previous line, like so: O O O O O O O O O O O O O O O O O I'm hoping someone can point me towards the right algorithm for this! Thanks!

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  • How would you sample a real-time stream of coordinates to create a Speed Graph?

    - by Andrew Johnson
    I have a GPS device, and I am receiving continuous points, which I store in an array. These points are time stamped. I would like to graph distance/time (speed) vs. distance in real-time; however, I can only plot 50 of the points because of hardware constraints. How would you select points from the array to graph? For example, one algorithm might be to select every Nth point from the array, where N results in 50 points total. Code: float indexModifier = 1; if (MIN(50,track.lastPointIndex) == 50) { indexModifier = track.lastPointIndex/50.0f; } index = ceil(index*indexModifier); Another algorithm might be to keep an array of 50 points, and throw out the point with the least speed change each time you get a new point.

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  • Implementing Dijkstra's Algorithm

    - by DeadMG
    I've been tasked (coursework @ university) to implement a form of path-finding. Now, in-spec, I could just implement a brute force, since there's a limit on the number of nodes to search (begin, two in the middle, end), but I want to re-use this code and came to implement Dijkstra's algorithm. I've seen the pseudo on Wikipedia and a friend wrote some for me as well, but it flat out doesn't make sense. The algorithm seems pretty simple and it's not a problem for me to understand it, but I just can't for the life of me visualize the code that would realize such a thing. Any suggestions/tips?

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  • [Java] Implement a RSA algorithm

    - by Robin Monjo
    Hello everyone. I want to implement a RSA algorithm to encrypt an image (byte[]). To generate my two keys I used this piece of code : KeyPairGenerator keygen = KeyPairGenerator.getInstance("RSA"); keygen.initialize(512); keyPair = keygen.generateKeyPair(); Once public and private key are generated, I would like to show them to the user so he can distribute the public key and use the private key to decode. How can I get back those key ? Using keygen.getPrivateKey() and keygen.getPublicKey() give me all the information of the RSA algorithm, not only the keys I need. Thanks

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  • Encrypt text using a number

    - by Adam Matan
    Project Euler I have recently begun to solve some of the Project Euler riddles. I found the discussion forum in the site a bit frustrating (most of the discussions are closed and poorly-threaded), So I have decided to publish my Python solutions on launchpad for discussion. The problem is that it seems quite unethical to publish these solutions, as it would let other people gain reputation without doing the programming work, which the site deeply discourages. My Encryption problem I want to encrypt my answers so that only those who have already solved the riddles can see my code. The logical key would be the answer to the riddle, which is always numeric. In order to prevent brute-force attacks on my answers, I want to find an encryption algorithm that takes a significantly long time (few seconds) to run. Do you know any such algorithm? I would fancy a Python package, which I can attach to the code, over an external program that might have portability issues. Thanks, Adam

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