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  • Efficient way of calculating average difference of array elements from array average value

    - by Saysmaster
    Is there a way to calculate the average distance of array elements from array average value, by only "visiting" each array element once? (I search for an algorithm) Example: Array : [ 1 , 5 , 4 , 9 , 6 ] Average : ( 1 + 5 + 4 + 9 + 6 ) / 5 = 5 Distance Array : [|1-5|, |5-5|, |4-5|, |9-5|, |6-5|] = [4 , 0 , 1 , 4 , 1 ] Average Distance : ( 4 + 0 + 1 + 4 + 1 ) / 5 = 2 The simple algorithm needs 2 passes. 1st pass) Reads and accumulates values, then divides the result by array length to calculate average value of array elements. 2nd pass) Reads values, accumulates each one's distance from the previously calculated average value, and then divides the result by array length to find the average distance of the elements from the average value of the array. The two passes are identical. It is the classic algorithm of calculating the average of a set of values. The first one takes as input the elements of the array, the second one the distances of each element from the array's average value. Calculating the average can be modified to not accumulate the values, but caclulating the average "on the fly" as we sequentialy read the elements from the array. The formula is: Compute Running Average of Array's elements ------------------------------------------- RA[i] = E[i] {for i == 1} RA[i] = RA[i-1] - RA[i-1]/i + A[i]/i { for i > 1 } Where A[x] is the array's element at position x, RA[x] is the average of the array's elements between position 1 and x (running average). My question is: Is there a similar algorithm, to calculate "on the fly" (as we read the array's elements), the average distance of the elements from the array's mean value? The problem is that, as we read the array's elements, the final average value of the array is not known. Only the running average is known. So calculating differences from the running average will not yield the correct result. I suppose, if such algorithm exists, it probably should have the "ability" to compensate, in a way, on each new element read for the error calculated as far.

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  • Are mathematical Algorithms protected by copyright?

    - by analogy
    I wish to implement an algorithm which i read in a journal paper in my software (commercial). I want to know if this is allowed or not. The algorithm in question is described in http://arxiv.org/abs/0709.2938 It is a very simple algorithm and a number of implementations exist in python (http://igraph.sourceforge.net/) and java. One of them is in gpl another which i got from a different researcher and had no license attached. There are significant differences in two implementations, e.g. second one uses threads and multiple cores. It is possible to rewrite/ (not translate) the algorithm. So can I use it in my software or on a server for commercial purpose. Thanks UPDATE: I am completely aware of copyright on the text of paper, it was published in phys rev E. I am concerned with use of the algorithm, in commercial software. Also the publication means that unless the patent has been already filed. The method has been disclosed publicly hence barring patent in future. Also the GPL implementation is not by authors themselves but comes from a third party. Finally i am not using the GPL implementation but creating my own using C++.

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  • Packing differently sized chunks of data into multiple bins

    - by knizz
    EDIT: It seems like this problem is called "Cutting stock problem" I need an algorithm that gives me the (space-)optimal arrangement of chunks in bins. One way would be put the bigger chunks in first. But see how that algorithm fails in this example: Chunks Bins ----------------------------- AAA BBB CC DD ( ) ( ) Algorithm Result ----------------------------- biggest first (AAABBB ) (CC ) optimal (AAACCDD) (BBB) "Biggest first" can't fit in DD. Maybe it helps to build a table like this: Size 1: --- Size 2: CC, DD Size 3: AAA, BBB Size 4: CCDD Size 5: AAACC, AAADD, BBBCC, BBBDD Size 6: AAABBB Size 7: AAACCDD, BBBCCDD Size 8: AAABBBCC, AAABBBDD Size 10: AAABBBCCDD

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  • Are mathamatical Algorithms protected by copyright

    - by analogy
    I wish to implement an algorithm which i read in a journal paper in my software (commercial). I want to know if this is allowed or not. The algorithm in question is described in http://arxiv.org/abs/0709.2938 It is a very simple algorithm and a number of implementations exist in python (http://igraph.sourceforge.net/) and java. One of them is in gpl another which i got from a different researcher and had no license attached. There are significant differences in two implementations, e.g. second one uses threads and multiple cores. It is possible to rewrite/ (not translate) the algorithm. So can I use it in my software or on a server for commercial purpose. Thanks

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  • Plotting an Arc in Discrete Steps

    - by phobos51594
    Good afternoon, Background My question relates to the plotting of an arbitrary arc in space using discrete steps. It is unique, however, in that I am not drawing to a canvas in the typical sense. The firmware I am designing is for a gcode interpreter for a CNC mill that will translate commands into stepper motor movements. Now, I have already found a similar question on this very site, but the methodology suggested (Bresenham's Algorithm) appears to be incompatable for moving an object in space, as it only relies on the calculation of one octant of a circle which is then mirrored about the remaining axes of symmetry. Furthermore, the prescribed method of calculation an arc between two arbitrary angles relies on trigonometry (I am implementing on a microcontroller and would like to avoid costly trig functions, if possible) and simply not taking the steps that are out of the range. Finally, the algorithm only is designed to work in one rotational direction (e.g. counterclockwise). Question So, on to the actual question: Does anyone know of a general-purpose algorithm that can be used to "draw" an arbitrary arc in discrete steps while still giving respect to angular direction (CW / CCW)? The final implementation will be done in C, but the language for the purpose of the question is irrelevant. Thank you in advance. References S.O post on drawing a simple circle using Bresenham's Algorithm: "Drawing" an arc in discrete x-y steps Wiki page describing Bresenham's Algorithm for a circle http://en.wikipedia.org/wiki/Midpoint_circle_algorithm Gcode instructions to be implemented (see. G2 and G3) http://linuxcnc.org/docs/html/gcode.html

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  • Books on string algorithms

    - by Max
    There have been numerous posts on string algorithms: http://stackoverflow.com/questions/246961/algorithm-to-find-similar-text, http://stackoverflow.com/questions/451884/similar-string-algorithm, http://stackoverflow.com/questions/613133/efficient-string-matching-algorithm However, no general literature was mentioned. Could anyone recommend a book(s) that would thoroughly explore various string algorithms? The topic which is of special interest is approximate string matching [things like google-offered corrected search string variants :) ]. Thanks a lot for advice.

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  • List modification in Python

    - by user2945143
    We are given an algorithm to modify a list of numbers from 1 to 28. There are 5 steps in the algorithm. We have written functions for each step (all correct). We need to write a function that combines all 5 steps. The algorithm modifies the list to get a value. Each time you get a new value, you use the list created by the algorithm from the previous step. This is what we have gotten so far for the code: get_card_at_top_index(insert_top_to_bottom(triple_cut((move_joker_2( move_joker_1(deck)))))) When we run the code to generate the get_card_at_top_index, the first answer is correct. However, the rest are not. Instead of using from the new list, python uses the value that it generated from the last step. What did we do wrong? UPDATE: The other 5 codes passed the tests, they are correct. Code 1 (List) = list1 Code 2 (list1) = list2 Code 3 (list2) = list3 Code 4 (list3) = list4 Code 5 (list4) = list5 we generate a number from 5. We need to run the algorithm again to generate 25 more numbers. We will use list 5 start from step 1

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  • How to find pythagorean triplets in an array faster than O(N^2)?

    - by SS
    Can someone suggest an algorithm that finds all Pythagorean triplets among numbers in a given array? If it's possible, please, suggest an algorithm faster than O(n2). Pythagorean triplet is a set {a,b,c} such that a2 = b2 + c2. Example: for array [9, 2, 3, 4, 8, 5, 6, 10] the output of the algorithm should be {3, 4, 5} and {6, 8, 10}.

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  • How to get a random node from a tree?

    - by ooboo
    It looks easy, but I found the implementation tricky. I need that for a simple genetic programming problem I'm trying to implement. The function should, given a node, return the node itself or any of its children such that the probability of choosing a node is normally distributed relative to its depth (so the function should return mostly middle nodes, but sometimes the root itself or the lowest ones - but that's not really necessary if that makes it significantly more complex, if all any node is chosen with equal probability, that's good enough). Thanks

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  • question on find value in array

    - by davit-datuashvili
    i have seen a few days ago such problem there is given two array find elements which are common of these array one of the solution was sort big array and then use binary search algorithm and also there is another algorithm- brute-force algorithm for (int i=0;i<array1.length;i++){ for (int j=0;j<array2.length;j++){ if (array1[i]==array2[j]){ //code here } } it's complexity is O(array1.length*array2.length); and i am interested the first method's complexity is also same yes? because we should sort array first and then use search method binary search algorithm's complexity is log_2(n) so it means that total time will be array.length*log_2(n) and about sort? please explain me which is better

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  • Splitting values into groups evenly

    - by Paul Knopf
    Let me try to explain the situation the best I can. Lets say I have 3 values 1, 2, 3 I tell an algorithm to split this values into x columns. Lets say x = 2 for clarification. The algorithm determines that the group of values is best put into two columns the following way. 1st column 2nd column --------------------------- 1 3 2 Each column has an even number (totals, not literals) value. Now lets say I have the following values 7, 8, 3, 1, 4 I tell the algorithm that I want the values split into 3 columns. The algorithm now tells me that the following is the best fit. 1st column 2nd column 3rd column 8 7 3 1 4 Notice how the columns arent quiet even, but it is as close as it can get. A little over and a little under is considered ok, as long as the list is AS CLOSE TO EVEN AS IT CAN BE. Anybody got any suggestions? Know any good methods of doing this?

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  • bulls and cows game -- programming algorithm(python)

    - by IcyFlame
    This is a simulation of the game Cows and Bulls with three digit numbers I am trying to get the number of cows and bulls between two numbers. One of which is generated by the computer and the other is guessed by the user. I have parsed the two numbers I have so that now I have two lists with three elements each and each element is one of the digits in the number. So: 237 will give the list [2,3,7]. And I make sure that the relative indices are maintained.the general pattern is:(hundreds, tens, units). And these two lists are stored in the two lists: machine and person. ALGORITHM 1 So, I wrote the following code, The most intuitive algorithm: cows and bulls are initialized to 0 before the start of this loop. for x in person: if x in machine: if machine.index(x) == person.index(x): bulls += 1 print x,' in correct place' else: print x,' in wrong place' cows += 1 And I started testing this with different type of numbers guessed by the computer. Quite randomly, I decided on 277. And I guessed 447. Here, I got the first clue that this algorithm may not work. I got 1 cow and 0 bulls. Whereas I should have got 1 bull and 1 cow. This is a table of outputs with the first algorithm: Guess Output Expected Output 447 0 bull, 1 cow 1 bull, 1 cow 477 2 bulls, 0 cows 2 bulls, 0 cows 777 0 bulls, 3 cows 2 bulls, 0 cows So obviously this algorithm was not working when there are repeated digits in the number randomly selected by the computer. I tried to understand why these errors are taking place, But I could not. I have tried a lot but I just could not see any mistake in the algorithm(probably because I wrote it!) ALGORITHM 2 On thinking about this for a few days I tried this: cows and bulls are initialized to 0 before the start of this loop. for x in range(3): for y in range(3): if x == y and machine[x] == person[y]: bulls += 1 if not (x == y) and machine[x] == person[y]: cows += 1 I was more hopeful about this one. But when I tested this, this is what I got: Guess Output Expected Output 447 1 bull, 1 cow 1 bull, 1 cow 477 2 bulls, 2 cows 2 bulls, 0 cows 777 2 bulls, 4 cows 2 bulls, 0 cows The mistake I am making is quite clear here, I understood that the numbers were being counted again and again. i.e.: 277 versus 477 When you count for bulls then the 2 bulls come up and thats alright. But when you count for cows: the 7 in 277 at units place is matched with the 7 in 477 in tens place and thus a cow is generated. the 7 in 277 at tens place is matched with the 7 in 477 in units place and thus a cow is generated.' Here the matching is exactly right as I have written the code as per that. But this is not what I want. And I have no idea whatsoever on what to do after this. Furthermore... I would like to stress that both the algorithms work perfectly, if there are no repeated digits in the number selected by the computer. Please help me with this issue. P.S.: I have been thinking about this for over a week, But I could not post a question earlier as my account was blocked(from asking questions) because I asked a foolish question. And did not delete it even though I got 2 downvotes immediately after posting the question.

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  • how do i determine the image compression algorithm

    - by klijo
    i have a folder containing images. I need to determine the image compression algorithm used in them. Image format is TIFF. Is there a program that i can use to do this ? A program that runs on windows or Linux is ok. When i do a file it gives 100 (2).tif: TIFF image data, little-endian 100.tif: TIFF image data, little-endian It doesnt say which type of algorithm it uses. whether its lossy or lossless and the name of it ?

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  • Should I be an algorithm developer, or java web frameworks type developer?

    - by Derek
    So - as I see it, there are really two kinds of developers. Those that do frameworks, web services, pretty-making front ends, etc etc. Then there are developers that write the algorithms that solve the problem. That is, unless the problem is "display this raw data in some meaningful way." In that case, the framework/web developer guy might be doing both jobs. So my basic problem is this. I have been an algorithms kind of software developer for a few years now. I double majored in Math and Computer science, and I have a master's in systems engineering. I have never done any web-dev work, with the exception of a couple minor jobs, and some hobby level stuff. I have been job interviewing lately, and this is what happens: Job is listed as "programmer- 5 years of experience with the following: C/C++, Java,Perl, Ruby, ant, blah blah blah" Recruiter calls me, says they want me to come in for interview In the interview, find out they have some webservices development, blah blah blah When asked in the interview, talk about my experience doing algorithms, optimization, blah blah..but very willing to learn new languages, frameworks, etc Get a call back saying "we didn't think you were a fit for the job you interviewed wtih, but our algorithm team got wind of you and wants to bring you on" This has happened to me a couple times now - see a vague-ish job description looking for a "programmer" Go in, find out they are doing some sort of web-based tool, maybe with some hardcore algorithms running in the background. interview with people for the web-based tool, but get an offer from the algorithms people. So the question is - which job is the better job? I basically just want to get a wide berth of experience at this level of my career, but are algorithm developers so much in demand? Even more so than all these supposed hot in demand web developer guys? Will I be ok in the long run if I go into the niche of math based algorithm development, and just little to no, or hobby level web-dev experience? I basically just don't want to pigeon hole myself this early. My salary is already starting to get pretty high - and I can see a company later on saying "we really need a web developer, but we'll hire this 50k/year college guy, instead of this 100k/year experience algorithm guy" Cliffs notes: I have been doing algorithm development. I consider myself to be a "good programmer." I would have no problem picking up web technologies and those sorts of frameworks. During job interviews, I keep getting "we think you've got a good skillset - talk to our algorithm team" instead of wanting me to learn new skills on the job to do their web services or whhatever other new technology they are doing. Edit: Whenever I am talking about algorithm development here - I am talking about the code that produces the answer. Typically I think of more math-based algorithms: solving a financial problem, solving a finite element method, image processing, etc

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  • Using GA in GUI

    - by AlexT
    Sorry if this isn't clear as I'm writing this on a mobile device and I'm trying to make it quick. I've written a basic Genetic Algorithm with a binary encoding (genes) that builds a fitness value and evolves through several iterations using tournament selection, mutation and crossover. As a basic command-line example it seems to work. The problem I've got is with applying a genetic algorithm within a GUI as I am writing a maze-solving program that uses the GA to find a method through a maze. How do I turn my random binary encoded genes and fitness function (add all the binary values together) into a method to control a bot around a maze? I have built a basic GUI in Java consisting of a maze of labels (like a grid) with the available routes being in blue and the walls being in black. To reiterate my GA performs well and contains what any typical GA would (fitness method, get and set population, selection, crossover, etc) but now I need to plug it into a GUI to get my maze running. What needs to go where in order to get a bot that can move in different directions depending on what the GA says? Rough pseudocode would be great if possible As requested, an Individual is built using a separate class (Indiv), with all the main work being done in a Pop class. When a new individual is instantiated an array of ints represent the genes of said individual, with the genes being picked at random from a number between 0 and 1. The fitness function merely adds together the value of these genes and in the Pop class handles selection, mutation and crossover of two selected individuals. There's not much else to it, the command line program just shows evolution over n generations with the total fitness improving over each iteration. EDIT: It's starting to make a bit more sense now, although there are a few things that are bugging me... As Adamski has suggested I want to create an "Agent" with the options shown below. The problem I have is where the random bit string comes into play here. The agent knows where the walls are and has it laid out in a 4 bit string (i.e. 0111), but how does this affect the random 32 bit string? (i.e. 10001011011001001010011011010101) If I have the following maze (x is the start place, 2 is the goal, 1 is the wall): x 1 1 1 1 0 0 1 0 0 1 0 0 0 2 If I turn left I'm facing the wrong way and the agent will move completely off the maze if it moves forward. I assume that the first generation of the string will be completely random and it will evolve as the fitness grows but I don't get how the string will work within a maze. So, to get this straight... The fitness is the result of when the agent is able to move and is by a wall. The genes are a string of 32 bits, split into 16 sets of 2 bits to show the available actions and for the robot to move the two bits need to be passed with four bits from the agent showings its position near the walls. If the move is to go past a wall the move isn't made and it is deemed invalid and if the move is made and if a new wall is found then the fitness goes up. Is that right?

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  • Can I use a genetic algorithm for balancing character builds?

    - by Renan Malke Stigliani
    I'm starting to build a online PVP (duel like, one-on-one) game, where there is leveling, skill points, special attacks and all the common stuff. Since I have never done anything like this, I'm still thinking about the math behind the levels/skills/specials balance. So I thought a good way of testing the best builds/combos, would be to implement a Genetic Algorithm. It'd be like this: Generate a big group of random characters Make them fight, level them up accordingly to their victories(more XP)/losses(less XP) Mate the winners, crossing their builds, to try and make even better characters Add some more random chars, emulating new players Repeat the process for some time, or util I find some chars who can beat everyone's butt I could then play with the math and try to find better balances to make sure that the top x% of chars would be a mix of various build types. So, is it a good idea, or is there some other, easier method to do the balancing?

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  • How can I extract similarities/patterns from a collection of binary strings?

    - by JohnIdol
    I have a collection of binary strings of given size encoding effective solutions to a given problem. By looking at them, I can spot obvious similarities and intuitively see patterns of symmetry and periodicity. Are there mathematical/algorithmic tools I can "feed" this set of strings to and get results that might give me an idea of what this set of strings have in common? By doing so I would be able to impose a structure (or at least favor some features over others) on candidate solutions in order to greatly reduce the search space, maximizing chances to find optimal solutions for my problem (I am using genetic algorithms as the search tool - but this is not pivotal to the question). Any pointers/approaches appreciated.

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  • How to transfer data between two networks efficiently

    - by Tono Nam
    I would like to transfer files between two places over the internet. Right now I have a VPN and I am able to browse, download and transfer files. So my question is not really how to transfer the files; Instead, I would like to use the most efficient approach because the two places constantly share a lot of data. The reason why I want to get rid of the VPN is because it is two slow. Having high upload speed is very expensive/impossible in residential places so I would like to use a different approach. I was thinking about using programs such as http://www.dropbox.com . The problem with Dropbox is that the free version comes with only 2 GB of storage. I think the deals they offer are OK and I might be willing to pay to get that increase in speed. But I am concerned with the speed of transferring data. Dropbox will upload the file to their server then send it from the server to the other location. I would like it to be even faster. Anyway I was thinking why not create a program myself. This is the algorithm that I was thinking of. Let me know if it sounds too crazy. (Remember my goal is to transfer files as fast as possible) Things that I will use in this algorithm: Server on the internet called S (Has fast download and upload speed. I pay to host a website and some services in there. I want to take advantage of it.) Client A at location 1 Client B at location 2 So lets say at location 1, 20 large files are created and need to be transferred to location 2. Client A compresses the files with the highest compression ratio possible. Client A starts sending data via UDP to client B. Because I am using UDP I will include the sequence number on each packet. Have server S help speed up things. For example every time a packet is lost we can use Server S to inform client A that it needs to resend a packet. Anyways I think this approach will increase the transfer rate. I do not know if it is possible to start sending data while it is being compressed. Or if it is possible to start decompressing data even if we are not done receiving the whole file. Maybe it will be faster to start sending the files right away without compressing. If I knew that I will always be sending large text files then I will obviously use the compression. I need this as a general algorithm. So I guess my question is could I increase performance by using UDP instead of TCP and by using an extra server to keep track of lost packets? And how should I compress files before sending? Compressing a 1 GB file with the highest compression ratio takes about 1 hour! I would like to take advantage of that time by sending it as it is being compressed.

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  • How to transfer data between two netowks efficiently

    - by Tono Nam
    I will like to transfer files between two places over the internet. Right now I have a VPN and I am able to browse, download and transfer files. So my question is not really how to transfer the files; Instead, I will like to use the most efficient approach because the two places constantly share a lot of data. The reason why I want to get rid of the vpn is because it is two slow. Having high upload speed is very expensive/impossible on residential places so I will like to use a different approach. I was thinking about using programs such as http://www.dropbox.com . The problem with dropbox is it only enables 2 GB of storage in order for it to be free. I think the deals they offer are ok and I might be willing to pay to get that increase in speed. But I am concerned with the speed of transferring data. Dropbox will upload the file to their server then send it from the server to the other location. I will like it even faster lol. Anyways I was thinking why not create a program my self. This is the algorithm that I was thinking let me know if it sounds to crazy. (remember my goal is to transfer files as fastest as possible) Things that I will use in this algorithm: Server on the internet called S ( has fast download and upload speed. I pay to host a website and some services in there. I want to take advantage of it) Client A on location 1 Client B on location 2 So lets say on location 1 20 large files are created and need to be transferred to location 2. Client A compresses the files with the highest compression ratio possible. Client A starts sending data via UDP to client B. Because I am using UDP I will include the sequence number on each package. Have server S help speed up things. For example every time a package is lost we can use Server S to inform client A that it needs to resend a package. Anyways I think this approach will increase the transfer rate. I do not know if it is possible to start sending data meanwhile it is being compressed. Also if it is possible to start decompressing data even if we are not done receiving all the info. Maybe it will be faster to start sending the files right away without compressing. If I knew that I will always be sending large text files then I will obviously use the compression. I need this as a general algorithm. So i guess my question is should using UDP over TCP could increase performance by using an extra server to keep track of lost packages? and How should I compress files before sending? compressing a 1 GB file with the highest compression ration takes about 1 hour! I will like to take advantage of that time by sending it meanwhile it is compressed.

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  • Setting up java configurations in eclipse..Param files

    - by Charlie
    I'm going to be using ECJ for doing genetic programming and I haven't touched java in years. I'm working on setting up the eclipse environment and I'm catching a few snags. The ECJ source has several packages, and several sample programs come along with it. I ran one sample program (called tutorial1) by going to the run configurations and adding -file pathToParamsFile to the program arguments. This made it point to the params file of that tutorial and run that sample. In a new example I am testing (from the package gui) there are TWO params files. I tried pointing to just one param file and a program ran in the console, but there was supposed to be a GUI which did not load. I'm not sure what I'm doing wrong. Any help would be greaaatly appreciated.

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  • How to create a container that holds different types of function pointers in C++?

    - by Alex
    I'm doing a linear genetic programming project, where programs are bred and evolved by means of natural evolution mechanisms. Their "DNA" is basically a container (I've used arrays and vectors successfully) which contain function pointers to a set of functions available. Now, for simple problems, such as mathematical problems, I could use one type-defined function pointer which could point to functions that all return a double and all take as parameters two doubles. Unfortunately this is not very practical. I need to be able to have a container which can have different sorts of function pointers, say a function pointer to a function which takes no arguments, or a function which takes one argument, or a function which returns something, etc (you get the idea)... Is there any way to do this using any kind of container ? Could I do that using a container which contains polymorphic classes, which in their turn have various kinds of function pointers? I hope someone can direct me towards a solution because redesigning everything I've done so far is going to be painful.

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