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  • Output from OouraFFT correct sometimes but completely false other times. Why ?

    - by Yan
    Hi I am using Ooura FFT to compute the FFT of the accelerometer data in windows of 1024 samples. The code works fine, but then for some reason it produces very strange outputs, i.e. continuous spectrum with amplitudes of the order of 10^200. Here is the code: OouraFFT *myFFT=[[OouraFFT alloc] initForSignalsOfLength:1024 NumWindows:10]; // had to allocate it UIAcceleration *tempAccel = nil; double *input=(double *)malloc(1024 * sizeof(double)); double *frequency=(double *)malloc(1024*sizeof(double)); if (input) { //NSLog(@"%d",[array count]); for (int u=0; u<[array count]; u++) { tempAccel = (UIAcceleration *)[array objectAtIndex:u]; input[u]=tempAccel.z; //NSLog(@"%g",input[u]); } } myFFT.inputData=input; // specifies input data to myFFT [myFFT calculateWelchPeriodogramWithNewSignalSegment]; // calculates FFT for (int i=0;i<myFFT.dataLength;i++) // loop to copy output of myFFT, length of spectrumData is half of input data, so copy twice { if (i<myFFT.numFrequencies) { frequency[i]=myFFT.spectrumData[i]; // } else { frequency[i]=myFFT.spectrumData[myFFT.dataLength-i]; // copy twice } } for (int i=0;i<[array count];i++) { TransformedAcceleration *NewAcceleration=[[TransformedAcceleration alloc]init]; tempAccel=(UIAcceleration*)[array objectAtIndex:i]; NewAcceleration.timestamp=tempAccel.timestamp; NewAcceleration.x=tempAccel.x; NewAcceleration.y=tempAccel.z; NewAcceleration.z=frequency[i]; [newcurrentarray addObject:NewAcceleration]; // this does not work //[self replaceAcceleration:NewAcceleration]; //[NewAcceleration release]; [NewAcceleration release]; } TransformedAcceleration *a=nil;//[[TransformedAcceleration alloc]init]; // object containing fft of x,y,z accelerations for(int i=0; i<[newcurrentarray count]; i++) { a=(TransformedAcceleration *)[newcurrentarray objectAtIndex:i]; //NSLog(@"%d,%@",i,[a printAcceleration]); fprintf(fp,[[a printAcceleration] UTF8String]); //this is going wrong somewhow } fclose(fp); [array release]; [myFFT release]; //[array removeAllObjects]; [newcurrentarray release]; free(input); free(frequency);

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  • Is there a website to lookup already common code functions?

    - by pinnacler
    I'm sitting here writing a function that I'm positive has been written before, somewhere on earth. It's just too common to have not been attempted, and I'm wondering why I can't just go to a website and search for a function that I can then copy and paste into my project in 2 seconds, instead of wasting my day reinventing the wheel. Sure there are certain libraries you can use, but where do you find these libraries and when they are absent, is there a site like I'm describing?

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  • How can I store this kind of graph in neo4j for fast traversal?

    - by James
    This is a graph whose nodes exist in many connected components at once because a node's relationships are a collection of edge groups such that only one edge per edge group can be present at once. I need to be able to find all of the connected components that a node exists in. What would be the best way to store this graph in neo4j to quickly find all of the connected components that a node exists in? Is there a way to use the built in traversals to do this? Also: is there a name for this kind of graph? I'd appreciate any help/ideas. Update: Sorry for not being clear. All nodes are of the same type. Nodes have a variable number of edge groups. Exactly one edge from each edge group needs to be chosen for a particular connected component. I'm going to try to explain through example: Node x1 is related to: (x2 or x3 or x4) AND (x5 or x6) AND (x7) Node x2 is related to: (x8) AND (x9 or x10) So x1's first edge group is (x2, x3, x4), its second edge group is (x5, x6), and its third edge group is (x7). So here are a few connected components that x1 exists in: CC1: x1 is related to: x2, x5, x7 x2 is related to: x8 x9 CC2: x1 is related to: x2, x6, x7 x2 is related to: x8, x9 CC3: x1 is related to: x3, x5, x7 CC4: x1 is related to: x3, x6, x7 etc. I'm grateful for your help in this.

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  • How does the Ableton warp algorithm work exactly?

    - by pepperdreamteam
    I'm looking for any documentation or definitive information on Ableton's warp feature. I understand that it has something to do with finding transients, aligning them with an even rhythm and shifting audio samples accordingly. I'm hoping to find ways to approximate warping with more basic audio editing tools. I understand that this is ableton's unique device, really any information about how it works would be helpful. So...does anyone have any 411?

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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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  • Generate encoding String according to creation order.

    - by Tony
    I need to generate encoding String for each item I inserted into the database. for example: x00001 for the first item x00002 for the sencond item x00003 for the third item The way I chose to do this is counting the rows. Before I insert the third item, I count against the database, I know there're already 2 rows, so the next encoding is ended with 3. But there is a problem. If I delete the second item, the forth item will not be the x00004,but x00003. I can add additional columns to table, to store the next encoding, I don't know if there's other better solutions ?

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  • Finding the position of the max element

    - by Faken
    Is there a standard function that returns the position(not value) of the max element of an array of values? For example: say i have an array like this: sampleArray = [1, 5, 2, 9, 4, 6, 3] I want a function that returns the integer of 3 that tells me that sampleArray[3] is the largest value in the array.

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  • How to find validity of a string of parentheses, curly brackets and square brackets?

    - by Rajendra
    I recently came in contact with this interesting problem. You are given a string containing just the characters '(', ')', '{', '}', '[' and ']', for example, "[{()}]", you need to write a function which will check validity of such an input string, function may be like this: bool isValid(char* s); these brackets have to close in the correct order, for example "()" and "()[]{}" are all valid but "(]", "([)]" and "{{{{" are not! I came out with following O(n) time and O(n) space complexity solution, which works fine: Maintain a stack of characters. Whenever you find opening braces '(', '{' OR '[' push it on the stack. Whenever you find closing braces ')', '}' OR ']' , check if top of stack is corresponding opening bracket, if yes, then pop the stack, else break the loop and return false. Repeat steps 2 - 3 until end of the string. This works, but can we optimize it for space, may be constant extra space, I understand that time complexity cannot be less than O(n) as we have to look at every character. So my question is can we solve this problem in O(1) space?

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  • Can my tortoise vs. hare race be improved?

    - by FredOverflow
    Here is my code for detecting cycles in a linked list: do { hare = hare.next(); if (hare == back) return; hare = hare.next(); if (hare == back) return; tortoise = tortoise.next(); } while (tortoise != hare); throw new AssertionError("cyclic linkage"); Is there a way to get rid of the code duplication inside the loop? Am I right in assuming that I don't need a check after making the tortoise take a step forward? As I see it, the tortoise can never reach the end of the list before the hare (contrary to the fable). Any other ways to simplify/beautify this code?

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  • Result of Long Positive Integers & Search and element in array..

    - by AGeek
    Hi, I have two Questions for which I cannot find answers by googling, but I find these questions very important for preparation.. Kindly explain only the logic, I will be able to code. In Search of Efficient Logic..... in terms of Memory and Time. WAP to add two long positive integers. What Data structure / data type we can use to store the numbers and result. What is the best way to search an element from an array in shortest time. Size of the array could be large enough, and any elements could be stored in the array(i.e. no range). Thanks.

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  • Check if a string substitution rule will ever generate another string.

    - by Mgccl
    Given two strings S and T of same length. Given a set of replacement rules, that find substring A in S and replace it with string B. A and B have the same length. Is there a sequence of rule application, such that it make string S into string T? I believe there is no better way to answer this than try every single rule in every single state. Which would be exponential time. But I don't know if there are better solutions to it.

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  • arbitrary vire connection / search and replace

    - by fatai
    input :["vire_connection",[1, 2, [ 3, [ 4, "connect"]]], ["connect", [3 , 5] ] ] output:["vire_connection",[ 1, 2, [ 3, [ 4, [ 3, 5 ] ] ] ] ], [ [ 3 , 5] ] ] after connection ( simply copying [3,5] to other wanted position ) , remove connect word input :["vire_connection", [ [ [ ["connect", [ 3, 4 ] ] ] ] ], [ 2, "connect"]] output :["vire_connection",[[[[[3,4]]]]], [ 2, [ 3 , 4 ]]] after connection ( simply copying [3,4] to other wanted position ) , remove connect word how can I do ?

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  • Fast, Vectorizable method of taking floating point number modulus of special primes?

    - by caffiend
    Is there a fast method for taking the modulus of a floating point number? With integers, there are tricks for Mersenne primes, so that its possible to calculate y = x MOD 2^31 without needing division. Can any similar tricks be applied for floating point numbers? Preferably, in a way that can be converted into vector/SIMD operations, or moved into GPGPU code. The primes I'm interested in would be 2^7 and 2^31, although if there are more efficient ones for floating point numbers, those would be welcome.

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  • Using c#,c/c++ or java to improve BBN with GA

    - by madicemickael
    I have a little problem in my little project , I wish that someone here could help me! I am planning to use a bayesian network as a decision factor in my game AI and I want to improve the decision making every step of the way , anyone knows how to do that ? Any tutorials / existing implementations will be very good,I hope some of you could help me. I heard that a programmer in this community did a good implementation of this put together for poker game AI.I am planning to use it like him ,but in another poker(Texas) or maybe Rentz. Looking for C/c++ or c# or java code. Thanks , Mike

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  • Tracking/Counting Word Frequency

    - by Joel Martinez
    I'd like to get some community consensus on a good design to be able to store and query word frequency counts. I'm building an application in which I have to parse text inputs and store how many times a word has appeared (over time). So given the following inputs: "To Kill a Mocking Bird" "Mocking a piano player" Would store the following values: Word Count ------------- To 1 Kill 1 A 2 Mocking 2 Bird 1 Piano 1 Player 1 And later be able to quickly query for the count value of a given arbitrary word. My current plan is to simply store the words and counts in a database, and rely on caching word count values ... But I suspect that I won't get enough cache hits to make this a viable solution long term. Can anyone suggest algorithms, or data structures, or any other idea that might make this a well-performing solution?

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  • How does Photoshop (Or drawing programs) blit?

    - by user146780
    I'm getting ready to make a drawing application in Windows. I'm just wondering, do drawing programs have a memory bitmap which they lock, then set each pixel, then blit? I don't understand how Photoshop can move entire layers without lag or flicker without using hardware acceleration. Also in a program like Expression Design, I could have 200 shapes and move them around all at once with no lag. I'm really wondering how this can be done without GPU help. I don't think super efficient algorithms could justify that? Thanks

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  • Given a word, how do I get the list of all words, that differ by one letter?

    - by user187809
    Let's say I have the word "CAT". These words differ from "CAT" by one letter (not the full list) CUT CAP PAT FAT COT etc. Is there an elegant way to generate this? Obviously, one way to do it is through brute force. pseduo code: while (0 to length of word) while (A to Z) replace one letter at a time, and check if the resulting word is a valid word If I had a 10 letter word, the loop would run 26 * 10 = 260 times. Is there a better, elegant way to do this?

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  • Picking apples off a tree

    - by John Retallack
    I have the following problem: I am given a tree with N apples, for each apple I am given it's weight and height. I can pick apples up to a given height H, each time I pick an apple the height of every apple is increased with U. I have to find out the maximum weight of apples I can pick. 1 = N = 100000 0 < {H, U, apples' weight and height, maximum weight} < 231 Example: N=4 H=100 U=10 height weight 82 30 91 10 93 5 94 15 The answer is 45: first pick the apple with the weight of 15 then the one with the weight of 30. Could someone help me approach this problem?

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  • Is my program taking too much time to execute?

    - by Conrad C
    I wanted to solve a question from project euleur about finding the largest prime number of a big number. I run my code on a virtual machine on Visual studio 2012, and the code seems froze. When I step into the loop, the code works well, but when I execute it, the console is always there. It is as if the program is still running. Could it be that the program takes time to execute? My Code static void Main(string[] args) { long number = 5; for (long i = 1; i < 600851475143; i++) { if (i % 2 != 0 && i % 1 == 0 && i % i == 0) number = i; } }

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  • An O(1) Sort ~~~

    - by FlySwat
    Before you stone me for being a heretic, There is a sort that proclaims to be O(1), called "Bead Sort" (http://en.wikipedia.org/wiki/Bead_sort) , however that is pure theory, when actually applied I found that it was actually O(N * M), which is pretty pathetic. That said, Lets list out some of the fastest sorts, and their best case and worst case speed in Big O notation. ~~ FlySwat ~~

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