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• what mysql table structure is better

  - by Sergey

  I have very complicated search algorithm on my site, so i decided to make a table with cache or maybe all possible results. I wanna ask what structure would be better, or maybe not the one of them? (mySQL) 1) word VARCHAR, results TEXT or BLOB where i'll store ids of found objects (for example 6 chars for each id) 2) word VARCHAR, result INT, but words are not unique now i think i'll have about 200 000 rows in 1) with 1000-10000 ids each row or 200 000 000+ rows in 2) First way takes more storage memory but i think it would be much faster to find 1 unique row among 200 000, than 1000 rows among 200 mln non unique rows i think about index on word column and no sphinx. So that do YOU think? p.s. as always, sorry for my english if it's not very good.

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• Use C function in C++ program; "multiply-defined" error

  - by eom

  I am trying to use this code for the Porter stemming algorithm in a C++ program I've already written. I followed the instructions near the end of the file for using the code as a separate module. I created a file, stem.c, that ends after the definition and has extern int stem(char * p, int i, int j) ... It worked fine in Xcode but it does not work for me on Unix with gcc 4.1.1--strange because usually I have no problem moving between the two. I get the error ld: fatal: symbol `stem(char*, int, int)' is multiply-defined: (file /var/tmp//ccrWWlnb.o type=FUNC; file /var/tmp//cc6rUXka.o type=FUNC); ld: fatal: File processing errors. No output written to cluster I've looked online and it seems like there are many things I could have wrong, but I'm not sure what combination of a header file, extern "C", etc. would work.

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• character matching in grayscale image

  - by maximus

  I made patterns: images with the "A" letter of different sizes (from 12 to 72: 12, 14, .., 72) And I tested the method of pattern matching and it gave a good results. One way to select text regions from image is to run that algorithm for all small and big letters and digits of different sizes. And fonts! I don't like it. Instead of it I want to make something like a universal pattern or better to say: scanning image with different window sizes and select those regions where some function (probability of that there is a character at that window) is more than some fixed value. Do you know any methods or ideas to make that function? It must work with original image (grayscale).

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• Architecture for analysing search result impressions/clicks to improve future searches

  - by Hais

  We have a large database of items (10m+) stored in MySQL and intend to implement search on metadata on these items, taking advantage of something like Sphinx. The dataset will be changing slightly on a daily basis so Sphinx will be re-indexing daily. However we want the algorithm to self-learn and improve search results by analysing impression and click data so that we provide better results for our customers on that search term, and possibly other similar search terms too. I've been reading up on Hadoop and it seems like it has the potential to crunch all this data, although I'm still unsure how to approach it. Amazon has tutorials for compiling impression vs click data using MapReduce but I can't see how to get this data in a useable format. My idea is that when a search term comes in I query Sphinx to get all the matching items from the dataset, then query the analytics (compiled on an hourly basis or similar) so that we know the most popular items for that search term, then cache the final results using something like Memcached, Membase or similar. Am I along the right lines here?

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• function to efficiently check a change of value in a nested hashmap

  - by zcaudate

  the motivation is for checking what has changed in a deeply nest map, kind of like a reverse of update-in. This is a simple example: (def p1 {:a {:a1 :1 :a2 :2} :b {:b1 :1 :b2 :2}}) (def p2 (update-in p1 [:a :a1] (constantly :updated)) ;; => {:a {:a1 :updated :a2 :2} ;; :b {:b1 :1 :b2 :2}} (what-changed? p1 p2) ;; => {:keys [:a :a1] :value :updated) (what-changed? p2 p1) ;; => {:keys [:a :a1] :value :2) I'm hoping that because clojure maps are persistent data-structures, there may be a smart algorithm to figure this out by looking at the underlying structure as opposed to walking through the nested maps and comparing the difference.

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• How to program a connection pool?

  - by the_drow

  Is there a known algorithm for implementing a connection pool? If not what are the known algorithms and what are their trade-offs? What design patterns are common when designing and programming a connection pool? Are there any code examples implement a connection pool using boost.asio? Is it a good idea to use a connection pool for presisting connections (not http)? How is threading related to connection pooling? When do you need a new thread?

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• Is there a class like a Dictionary without a Value template? Is HashSet<T> the correct answer?

  - by myotherme

  I have 3 tables: Foos, Bars and FooBarConfirmations I want to have a in-memory list of FooBarConfirmations by their hash: FooID BarID Hash 1 1 1_1 2 1 2_1 1 2 1_2 2 2 2_2 What would be the best Class to use to store this type of structure in-memory, so that I can quickly check to see if a combination exists like so: list.Contains("1_2"); I can do this with Dictionary<string,anything>, but it "feels" wrong. HashSet looks like the right tool for the job, but does it use some form of hashing algorithm in the background to do the lookups efficiently?

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• Update NSView in function of events

  - by Forchita

  Hi everyone! I have a main view (subclass of NSView) and as i'm new to cocoa, i'd like to know how to update the view in function of events. I know there are many methods that take events such as -(void)mouseMoved:(NSEvent*)event or - (void)mouseClicked:(NSEvent*)event My algorithm to determine what to do is ready. I want to know where I should update the main view: is it in the -(void)mouseMoved:(NSEvent*)event or in the - (void)drawRect:(NSRect)dirtyRect. And if it is in drawRect, then how should i pass the information to it? Thanks in advance!

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• kmeans based on mapreduce by python

  - by user3616059

  I am going to write a mapper and reducer for the kmeans algorithm, I think the best course of action to do is putting the distance calculator in mapper and sending to reducer with the cluster id as key and coordinates of row as value. In reducer, updating the centroids would be performed. I am writing this by python. As you know, I have to use Hadoop streaming to transfer data between STDIN and STOUT. according to my knowledge, when we print (key + "\t"+value), it will be sent to reducer. Reducer will receive data and it calculates the new centroids but when we print new centroids, I think it does not send them to mapper to calculate new clusters and it just send it to STDOUT and as you know, kmeans is a iterative program. So, my questions is whether Hadoop streaming suffers of doing iterative programs and we should employ MRJOB for iterative programs?

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• Merging and splitting overlapping rectangles to produce non-overlapping ones

  - by uj

  I am looking for an algorithm as follows: Given a set of possibly overlapping rectangles (All of which are "not rotated", can be uniformly represented as (left,top,right,bottom) tuplets, etc...), it returns a minimal set of (non-rotated) non-overlapping rectangles, that occupy the same area. It seems simple enough at first glance, but prooves to be tricky (at least to be done efficiently). Are there some known methods for this/ideas/pointers? Methods for not necessarily minimal, but heuristicly small, sets, are interesting as well, so are methods that produce any valid output set at all.

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• Beginner C: error: control reaches end of non-void function?

  - by Ting

  I'm trying to make a greedy algorithm and I get this error: greedy2.c:27:1: error: control reaches end of non-void function [-Werror,-Wreturn-type] } ^ 1 error generated. with this code: int man(int argc, char* argv[]) { float amount; do { printf("Input dollar amount owed:\n"); amount = GetFloat(); } while (amount <= 0); int coins = 0; while (amount >= 0.25); { amount = amount - 0.25; coins++; } printf("Number of coins to use: %d\n", coins); } What is wrong with my curly braces, and how do I fix it?

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• android spectrum analysis of streaming input

  - by TheBeeKeeper

  for a school project I am trying to make an android application that, once started, will perform a spectrum analysis of live audio received from the microphone or a bluetooth headset. I know I should be using FFT, and have been looking at moonblink's open source audio analyzer ( http://code.google.com/p/moonblink/wiki/Audalyzer ) but am not familiar with android development, and his code is turning out to be too difficult for me to work with. So I suppose my questions are, are there any easier java based, or open source android apps that do spectrum analysis I can reference? Or is there any helpful information that can be given, such as; steps that need be taken to get the microphone input, put it into an fft algorithm, then display a graph of frequency and pitch over time from its output? Any help would be appreciated, thanks.

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• Parsing String to TreeNode

  - by Krusu70

  Anyone have a good algorithm how to parse a String to TreeNode in Java? Let's say we have a string s which says how to build a TreeNode. A(B,C) means that A is the name (String) of TreeNode, B is child of A (Treenode), C is sibling of A (TreeNode). So if I call function with string A(B(D,E(F,G)),C) (just a example), then I get a TreeNode equals to: level A (String: name), B - Child (TreeNode), C - Sibling (TreeNode) level B (String: name), D - Child of B (TreeNode), E - Sibling of B (TreeNode) level E (String: name), F - Child of E (TreeNode), G - Sibling of E (TreeNode) The name may not be 1 letter, it could be like real name (many letters).

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• Animate a e.Graphics.DrawLine with arrowhead

  - by Fer

  I need to "animate" an arrow. It can go in any direction (up, down, left, right and diagonals) and the arrowhead will be at the end. It needs to appear as if it is growing from orgin to the end. To make matters more complicated it has to be in a user control so it is possible to add to the controls collection in the forms and remove it to delete it from the screen, and its background is really transparent (no color.transparent) so i can't paint the background to "clear" the previous line. I have it static already (drawn from origin to end) but i can't animate it. I tried to add a timer in the user control but I fail to get a correct algorithm to calculate the intermediate ends of the line while it is growing. Any help would be appreciated. Thanks

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• Quick-sort doesn't work with middle pivot element

  - by Bobby

  I am trying to sort an array of elements using quick-sort algorithm.But I am not sure where am I going wrong.I choose the middle element as pivot every time and then I am checking the conditions.Here is my code below. void quicksort(int *temp,int p,int r) { if(r>p+1) { int mid=(p+r)/2; int piv=temp[mid]; int left=p+1; int right=r; while(left < right) { if(temp[left]<=piv) left++; else swap(&temp[left],&temp[--right]); } swap(&temp[--left],&temp[p]); quicksort(temp,p,left); quicksort(temp,right,r); } }

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• Counting variables per observation per month in Sas.

  - by John

  Hey guys, a quick question, I have data of the following sort: Ticker _ Date _ Fem Analyst (dummy 1 if true) AA _ 04/2001 _ 1 AA _ 04/2001 _ 1 AA _ 04/2001 _ 1 AA _ 05/2002 _ 1 AA _ 05/2002 _ 1 AA _ 07/2002 _ 0 AA _ 04/2003 _ 1 and so on.. What I want to receive is the following: Ticker _ Date _ Number of fem analyst AA _ 04/2001 _ 3 AA _ 05/2002 _ 2 AA _ 07/2002 _ 0 AA _ 04/2003 _ 1 So an easy counting algorithm that allows me to count for the number of analysts per company per month (the date is in 01/04/2002 format but I also have a month count variable which can be used too) Any ideas?

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• How can you deflect a direction/magnitude vector based on a direction/magnitude vector and a collided triangle?

  - by JeanOTF

  So, I have a Triangle-AABB collision algorithm and I have it returning the triangle that the AABB collided with. I was hoping with the 3 vectors of the triangle and the direction/magnitude of the movement would let me determine a deflected vector so that when you run against the wall at an angle you move slower, depending on the angle of collision, but along side the wall. This would remove the sticky collision problem with only moving when there is not a collision. Any suggestions or references would be greatly appreciated! Thanks.

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• Disposing a Bitmap through its Finalizer

  - by devoured elysium

  I have a complex program in which I have to first create, then use wrappers around bitmaps and send them across a lot of different classes. The problem in the end is deciding which classes should dispose the bitmaps. Most of the time the end classes don't know if they can indeed dispose the bitmap as the same bitmap can be used in several places. Also, I can't just copy the bitmaps because this is a kind of resource intensive algorithm and doing it would be dead slow. I looked up on reflector for Image/Bitmap's implementations and they seem to use the Dispose Pattern. So, even if I don't call Dispose(), the CLR will eventually call it some other time. Is it too bad if I just let the bitmaps be as they are, and let the finalizer take care of them?

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• Deleting Part of An Array in Java to Free Memory on Heap

  - by kate

  I am implementing a dynamic programming algorithm for the knapsack problem in Java. I declare the array and then initialize its size to be [number of objects][capacity of knapsack]. When my number of objects or my capacity gets too large, I get a memory error because I run out of space on the heap. My questions is: If I delete rows from my double array as I go along, will Java free the memory as I delete? Or does Java reserve that memory space for the size of the array I originally created? If it's the latter, is there a way to manually free the memory in Java? Thanks for your Help!

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• Correct expression for checking leap years

  - by Debanjan

  What will be the exact definition of leap year? AFAIK "A year which is divisible by 4 is a leap year. But for century years' the years which are divisible by 400 is a leap year." But that definition makes 100, 200, 300, 400.... upto 1700 NOT LEAP years! But in Gregorian calendar all of them are all leap year, check this out. You can also try "call 1700" in Linux to verify. So the correct algorithm for leap years would be: if ( (year % 4 == 0) && ( year <= 1700 || year % 100 != 0 || year % 400 == 0 )) printf("%d is a leap year.\n", year); else printf("%d is not a leap year.\n", year); But is this specific to Gregorian calendar? Even if that is the case why is it not mentioned here? Regards, PS:The history of Gregorian callender seems interesting check out the September month of 1752.

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• Validation of viewstate MAC failed in Safari

  - by Midhat

  Hi I have a web app using forms authentication. When I perform the following steps Let the login cookie expire Click on a link that requires a logged in user The user is redirected to the login page Click the browser back button The user is redirected to the login page again Log in using a valid username/password I get this exception Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster. This case appears only in safari (windows and mac). The fundamental difference between safari and other browsers is that when we click the back button in step 4, safari shows the login page again, while the other browsers show the previous page the user was working on. Please help in this regard

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• Using my ISerializable implementation instead of DataContractSerializer

  - by mpm

  My WCF client and server exchange objects whose types are defined on a class library shared by both, the server and the client. These objects implement custom serialization via ISerializable. However, my custom serialization is not being used. DataContractSerializer is being used, instead. How do I force my custom serialization to be used? The reason why I need to use my own serialization is because I do trasfer some big object graphs and my serialization algorithm does a good job in compressing/speeding up things.

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• Security issues in accepting passwords vs auto generating the password

  - by Vivekanand Poojari

  Hi, I am developing a console application. This application generates a self signed certificate and installs it in the current machine's certificate store. The steps invlolved are :- Generate a certificate Create a pfx file Install the pfx file For these steps i would need a password for protecting the private key and the pfx file. However these passwords are used only during the execution of the exe. Should I auto generate a password using some random number generation algorithm or accept the password as input from the user? What are the security issues involved in both the scenarios ? Thanks Vivekanand

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• How can I add floats together in different orders, and always get the same total?

  - by splicer

  Let's say I have three 32-bit floating point values, a, b, and c, such that (a + b) + c != a + (b + c). Is there summation algorithm, perhaps similar to Kahan summation, that guarantees that these values can be summed in any order and always arrive at the exact same (fairly accurate) total? I'm looking for the general case (i.e. not a solution that only deals with 3 numbers). Is arbitrary precision arithmetic the only way to go? I'm dealing with very large data sets, so I'd like to avoid the overhead of using arbitrary precision arithmetic if possible. Thanks!

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• Windows Server 2008 Antivirus Software with an API

  - by Dave Jellison

  I'm looking for an Antivirus package that is compliant with Windows Server 2008. That's not the hard part. What I need is an API layer on the Antivirus that i can call from managed .net code. For example: I am developing an Asp.Net (C#) website that allows users to upload files to the web server which the web site resides on. We have full control of the server so there are no security/rights issues on the server. I need to be able to run the antivirus algorithm on the newly uploaded files without (hopefully) shelling out to a command-ilne version of the software. Does anyone know of such a package?

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