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  • Speed up multiple JDBC SQL querys?

    - by paddydub
    I'm working on a shortest path a* algorithm in java with a mysql db. I'm executing the following SQL Query approx 300 times in the program to find route connections from a database of 10,000 bus connections. It takes approx 6-7 seconds to execute the query 300 times. Any suggestions on how I can speed this up or any ideas on a different method i can use ? Thanks ResultSet rs = stmt.executeQuery("select * from connections" + " where Connections.From_Station_stopID ="+StopID+";"); while (rs.next()) { int id = rs.getInt("To_Station_id"); String routeID = rs.getString("To_Station_routeID"); Double lat = rs.getDouble("To_Station_lat"); Double lng = rs.getDouble("To_Station_lng"); int time = rs.getInt("Time"); }

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  • Embarrassingly parallel workflow creates too many output files

    - by Hooked
    On a Linux cluster I run many (N > 10^6) independent computations. Each computation takes only a few minutes and the output is a handful of lines. When N was small I was able to store each result in a separate file to be parsed later. With large N however, I find that I am wasting storage space (for the file creation) and simple commands like ls require extra care due to internal limits of bash: -bash: /bin/ls: Argument list too long. Each computation is required to run through a qsub scheduling algorithm so I am unable to create a master program which simply aggregates the output data to a single file. The simple solution of appending to a single fails when two programs finish at the same time and interleave their output. I have no admin access to the cluster, so installing a system-wide database is not an option. How can I collate the output data from embarrassingly parallel computation before it gets unmanageable?

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  • head detection from video

    - by Aman Kaushal
    I have to detect heads of people in crowd in real time.For that I detected edge from video using matlab but from edge detected video , how to identify heads that i am unable to do. I used edge detection of video because it is easy to find circle from edged video and detection of head would be easy can anyone help me or suggest me any method for head- detection in real time. I have used VGG head detector and viola jones algorithm but it is only detecting face for small size video not detecting heads for large crowd. Suggestions?

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  • Tracing\profiling instructions

    - by LeChuck2k
    Hi Y'all. I'd like to statistically profile my C code at the instruction level. I need to know how many additions, multiplications, devides, etc,... I'm performing. This is not your usual run of the mill code profiling requirement. I'm an algorithm developer and I want to estimate the cost of converting my code to hardware implementations. For this, I'm being asked the instruction call breakdown during run-time (parsing the compiled assembly isn't sufficient as it doesn't consider loops in the code). After looking around, It seems VMWare may offer a possible solution, but I still couldn't find the specific feature that will allow me to trace the instruction call stream of my process. Are you aware of any profiling tools which enable this?

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  • I'm having a problem identifying a floating point exception.

    - by Peter Stewart
    I'm using c++ in visual studio express to generate random expression trees for use in a genetic algorithm type of program. Because they are random, the trees often generate (I'll call them exceptions, I'm not sure what they are) Thanks to a suggestion by George, I turned the mask _MCW_EM on so that hardware interrupts are turned off. (the default) So, the program runs uninterrupted, but some of the values returned are: -1.#INF, -1.#NAN, -1.#INV. I don't know how to identify these so that I can throw an exeption: if ( variable == -1.#INF) ?? DigitalRoss in this post seemed to have the solution, but as I understood it I couldn't make it work. I've been looking all over the place for this simple bit of code, that I assumed would be used all the time, but have had no luck. thanks

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  • What are some useful SQL statements / usage patterns that should be known by all developers who may

    - by Jian Lin
    What are some useful SQL statements that should be known by all developers who may touch the Back end side of the project? (Update: just like in algorithm, we know there are sorting problems, shuffling problems, and we know some solutions to them. This question is aiming at the same thing). For example, ones I can think of are: Get a list of Employees and their boss. Or one with the employee's salary greater than the boss. (Self-join) Get a list of the most popular Classes registered by students, from the greatest number to the smallest. (Count, group by, order by) Get a list of Classes that are not registered by any students. (Outer join and check whether the match is NULL, or by Get from Classes table, all ClassIDs which are NOT IN (a subquery to get all ClassIDs from the Registrations table)) Are there some SQL statements that should be under the sleeve of all developers that might touch back end data?

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  • Encryption-Decryption in Rails

    - by Salil
    Hi All, I am using require 'digest/sha1' to encrypt my password and save into database. During login I authenticate by matching the encrypted password saved in database and again encrypted the one use enter in password field. As of now everything works fine but now I want to do 'Forgot Password' functionality. To do this I need to decrypt the password which is saved in database to find original one. How to decrypt using digest/sha1? Or does anyone know any algorithm which supports encryption & decryption as well? I am using ruby on rails so I need Ruby way to accomplish it.

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  • Matching a rotated bitmap to a collage image

    - by Dmi
    Hi, My problem is that I have an image of a detailed street map. On this map, there can be a certain small image of a sign (such as a traffic light icon) rotated at any angle, maybe resized. I have this small image in a bitmap. Is there any algorithm or technique by which I can locate this bitmap if a copy of it exists, rotated and maybe resized, in the large collage image? This is similar to the problem with Augmented Reality and locating the marker image, but mine is only 2D with no perspective distortion.

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  • How can I tell if a closed path contains a given point?

    - by Tom Seago
    In Android, I have a Path object which I happen to know defines a closed path, and I need to figure out if a given point is contained within the path. What I was hoping for was something along the lines of path.contains(int x, int y) but that doesn't seem to exist. The specific reason I'm looking for this is because I have a collection of shapes on screen defined as paths, and I want to figure out which one the user clicked on. If there is a better way to be approaching this such as using different UI elements rather than doing it "the hard way" myself, I'm open to suggestions. I'm open to writing an algorithm myself if I have to, but that means different research I guess.

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  • [PHP] - Lowering script memory usage in a "big" file creation

    - by Riccardo
    Hi there people, it looks like I'm facing a typical memory outage problem when using a PHP script. The script, originally developed by another person, serves as an XML sitemap creator, and on large websites uses quite a lot of memory. I thought that the problem was related due to an algorithm holding data in memory until the job was done, but digging into the code I have discovered that the script works in this way: open file in output (will contain XML sitemap entries) in the loop: ---- for each entry to be added in sitemap, do fwrite close file end Although there are no huge arrays or variables being kept in memory, this technique uses a lot of memory. I thought that maybe PHP was buffering under the hood the fwrites and "flushing" data at the end of the script, so I have modified the code to close and open the file every Nth record, but the memory usage is still the same.... I'm debugging the script on my computer and watching memory usage: while script execution runs, memory allocation grows. Is there a particular technique to instruct PHP to free unsed memory, to force flushing buffers if any? Thanks

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  • Set NTFS Permissions with DirectorySecurity after created Active Dirctory Groups c#

    - by maverick
    Hi I am a little confused about setting NTFS Permissions to a directory after I created Active Directory Groups (both programmatically). When I created the Active Directory Objects then I have to wait a few seconds to set the NTFS Permissions. If I have not this timeout then I get sometimes an error message that the identify (active directory groupname) could not found. Is it possible that the DirectorySecurity-Class from DirectoryInfo-Class has an different algorithm to get the idenfity from active directory objects? Because when I checking the existing of the groups in active directory with System.DirectoryServices all the objects exist suddenly after creation. Kind regards

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  • Lua: Random: Percentage

    - by jargl
    I'm creating a game and currently have to deal with some math.randomness. As I'm not that strong in Lua, how do you think Can you make an algorithm that uses math.random with a given percentage? I mean a function like this: function randomChance( chance ) -- Magic happens here -- Return either 0 or 1 based on the results of math.random end randomChance( 50 ) -- Like a 50-50 chance of "winning", should result in something like math.random( 1, 2 ) == 1 (?) randomChance(20) -- 20% chance to result in a 1 randomChance(0) -- Result always is 0 However I have no clue how to go on, and I completely suck at algorithms I hope you understood my bad explanation of what I'm trying to accomplish

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  • java and mysql geting shortest path from to two points

    - by shaharnakash
    hi i have a mysql database that hold id ,name , oneid , twoid , size 1 1 1 2 4 2 2 1 3 1 3 3 2 1 74 4 4 2 4 2 5 5 2 5 12 6 6 4 2 12 7 7 4 6 74 8 8 4 7 12 9 9 3 5 32 10 10 3 8 22 11 11 5 3 66 12 12 5 6 76 13 13 5 9 33 14 14 6 10 11 15 15 6 7 21 16 16 8 3 12 17 17 8 9 10 18 18 9 8 2 19 19 9 10 72 20 20 10 6 31 21 21 10 7 7 22 22 10 9 18 23 23 7 6 8 i want to do Dijkstra algorithm but i cant get the details right if i got the contents to class Conn id ,name , oneid , twoid , size how do i find the path from oneid 1 to twoid 7 and believe me i triad many Dijkstra algorithms so please dont give me only reference

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  • Determining whether a file is a duplicate

    - by Todd R
    Is there a reliable way to determine whether or not two files are the same? For example, two files with the same size and type may or may not be the same binarilly (yeah, I know it's not really a word). I assume that comparing one or two checksums of the files will help, but I wonder: How reliable are checksums at determining whether two files are different; what are the chances of two different files having the same checksum? Would reliability increase by applying additional checksum comparisons? Which checksum algorithm(s) would be the most efficient and/or reliable? Any ideas, suggestions or thoughts are appreciated! P.S. The code for this is being written in Java running on a nix system, but generic or platform agnostic input is most helpful.

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  • Google Maps API v3 - Directions/Paths breaking KML Overlay Infowindows

    - by Douglas
    I'm in the end stages before content filling and then production on the Google Maps project I've been working on. A number of bugs and such have been thwarted, but this latest one has me relatively stumped. The demo map can be viewed here: http://dougglover.com/samples/finalProduct/ Everything works fine until you create a path using the Directions section(not to be confused with Get Directions). To reproduce the problem, play around with the map, click on a building or two, just to see the functionality. After ensuring that clicking on a building works(brings up an infowindow), choose two buildings to get directions to in the Directions area. It works great with the routing algorithm I've implemented, and the paths show up nicely, and intelligently. The problem being that you can't click buildings anymore to see their info. I'm assuming it has something to do with the z-index error popping up in the console, but I'm not sure how to handle that if it is the problem. Any guidance is greatly appreciated. :)

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  • [Ruby] How can I randomly iterate through a large Range?

    - by void
    I would like to randomly iterate through a range. Each value will be visited only once and all values will eventually be visited. For example: (0..9).sort_by{rand}.map{|x| f(x)} where f(x) is some function that operates on each value. A Fisher-Yates shuffle could be used to increase efficiency, but this code is sufficient for many purposes. My problem is that sort_by will transform the range into an array, which is not cool because I am working with astronomically large numbers. Ruby will quickly consume a large amount of RAM trying to create a monstrous array. This is also why the following code will not work: tried = {} # store previous attempts bigint = 99**99 bigint.times { x = rand(bigint) redo if tried[x] tried[x] = true f(x) # some function } This code is very naive and quickly runs out of memory as tried obtains more entries. What sort of algorithm can accomplish what I am trying to do?

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  • saving file name from html form input

    - by user343934
    I am working on python and biopython right now. I have a file upload form and whatever file is uploaded suppose(abc.fasta) then i want to pass same name in execute (abc.fasta) function parameter and display function parameter (abc.aln). Workflow goes like this. ----If submit is not true then display only header and form part --- if submit is true then call execute() and get file name from form input --- Then display the save file result in the same page. File name is same as input. My raw code is here -- http://pastebin.com/FPUgZSSe Any suggestions, changes and algorithm is appreciated Thanks

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  • Simulating brush strokes for painting application

    - by DrRobot
    I'm trying to write an application that can be used to create pictures that look like paintings using simulated brush strokes. Are there any good sources for simple ways of simulating brush strokes? For example, given a list of mouse positions that the user has dragged the mouse through, a brush width and a brush texture, how do I determine what to draw to the canvas? I've tried angling the brush texture in the direction of the mouse movement and dabbing several brush texture images along the path, but it doesn't look great. I think I'm missing something where the brush texture should shrink and grow on corners. Any simple to follow links would be appreciated. I've found complex academic papers on simulating e.g. oil paints but I just want a basic algorithm to use that produces OK results if possible.

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  • NASM: Count how many bits in a 32 Bit number are set to 1.

    - by citronas
    I have a 32 Bit number and want to count know how many bits are 1. I'm thinking of this pseudocode: mov eax, [number] while(eax != 0) { div eax, 2 if(edx == 1) { ecx++; } shr eax, 1 } Is there a more efficient way? I'm using NASM on a x86 processor. (I'm just beginning with assembler, so please do not tell me to use code from extern libraries, because I do not even know how to include them ;) ) (I just found http://stackoverflow.com/questions/109023/best-algorithm-to-count-the-number-of-set-bits-in-a-32-bit-integer which also contains my solution. There are other solutions posted, but unfortunatly I can't seem to figure out, how I would write them in assembler)

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  • How to map a property for HQL usage only (in Hibernate)?

    - by ManBugra
    i have a table like this one: id | name | score mapped to a POJO via XML with Hibernate. The score column i only need in oder by - clauses in HQL. The value for the score column is calculated by an algorithm and updated every 24 hours via SQL batch process (JDBC). So i dont wanna pollute my POJO with properties i dont need at runtime. For a single column that may be not a problem, but i have several different score columns. Is there a way to map a property for HQL use only? For example like this: <property name="score" type="double" ignore="true"/> so that i still can do this: from Pojo p order by p.score but my POJO implementation can look like this: public class Pojo { private long id; private String name; // ... } No Setter for score provided or property added to implementation. using the latest Hibernate version for Java.

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  • smallest perimiter rectangle with given integer area and integer sides

    - by remuladgryta
    Given an integer area A, how can one find integer sides w and h of a rectangle such that w*h = A and w+h is as small as possible? I'd rather the algorithm be simple than efficient (although within reasonable efficiency). What would be the best way to accomplish this? Finding out the prime factors of A, then combining them in some way that tries to balance w and h? Finding the two squares with integer sides with areas closest to A and then somehow interpolating between them? Any other method i'm not thinking of?

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  • List of divisors of an integer n (Haskell)

    - by Code-Guru
    I currently have the following function to get the divisors of an integer: -- All divisors of a number divisors :: Integer -> [Integer] divisors 1 = [1] divisors n = firstHalf ++ secondHalf where firstHalf = filter (divides n) (candidates n) secondHalf = filter (\d -> n `div` d /= d) (map (n `div`) (reverse firstHalf)) candidates n = takeWhile (\d -> d * d <= n) [1..n] I ended up adding the filter to secondHalf because a divisor was repeating when n is a square of a prime number. This seems like a very inefficient way to solve this problem. So I have two questions: How do I measure if this really is a bottle neck in my algorithm? And if it is, how do I go about finding a better way to avoid repetitions when n is a square of a prime?

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  • F# replace ref variable with something fun

    - by Stephen Swensen
    I have the following F# functions which makes use of a ref variable to seed and keep track of a running total, something tells me this isn't in the spirit of fp or even particular clear on its own. I'd like some direction on the clearest (possible fp, but if an imperative approach is clearer I'd be open to that) way to express this in F#. Note that selectItem implements a random weighted selection algorithm. type WeightedItem(id: int, weight: int) = member self.id = id member self.weight = weight let selectItem (items: WeightedItem list) (rand:System.Random) = let totalWeight = List.sumBy (fun (item: WeightedItem) -> item.weight) items let selection = rand.Next(totalWeight) + 1 let runningWeight = ref 0 List.find (fun (item: WeightedItem) -> runningWeight := !runningWeight + item.weight !runningWeight >= selection) items let items = [new WeightedItem(1,100); new WeightedItem(2,50); new WeightedItem(3,25)] let selection = selectItem items (new System.Random())

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  • Trying to find a good javascript function for hmac-sha1

    - by Darxval
    So i have been searching the web for a javascript source for an Hmac-sha1 algorithm. I saw Crypto's but i cant seem to get it to work, mainly because it has no idea what crypto means. (i copied the .js script functions into my script file) http://code.google.com/p/crypto-js/ I have my base64 encoded function already. that i got from here: http://nerds-central.blogspot.com/2007/01/fast-scalable-javascript-and-vbscript.html btw this for a twitter application using the new OAuth system. any help or links to where i can find anything on this would be helpful If you need me to elaborate let me know. thank you!

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  • How to reduce the number of points in (x,y) data

    - by Gowtham
    I have a set of data points: (x1, y1) (x2, y2) (x3, y3) ... (xn, yn) The number of sample points can be thousands. I want to represent the same curve as accurately as possible with minimal (lets suppose 30) set of points. I want to capture as many inflection points as possible. However, I have a hard limit on the number of allowed points to represent the data. What is the best algorithm to achieve the same? Is there any free software library that can help? PS: I have tried to implement relative slope difference based point elimination, but this does not always result in the best possible data representation. Thanks for your time. -Gowtham

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