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• minimum enclosing rectangle of fixed aspect ratio

  - by Ramya Narasimha

  I have an Image with many rectangles at different positions in the image and of different sizes (both overlapping and non-overlapping). I also have a non-negative scores associated with each of these rectangles. My problem now is to find one larger rectangle *of a fixed (given) aspect ratio* that encloses as many of these rectangles as possible. I am looking for an algorithm to do this, if anyone has a solution, even a partial one it would be helpful. Please note that the positions of the rectangles in the image is fixed and cannot be moved around and there is no orientation issue as all of them are upright.

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• SQL Encryption - Asymmetric Key - 2nd Server

  - by Jason Heine

  Hello, I created an asymmetric key on one of my SQL servers (2008). I encrypted a password field and I am able to retrieve that password just fine on my development server. The issue comes into play where I need to move this data to a production server. Here is the code for the key that was created: CREATE MASTER KEY ENCRYPTION BY PASSWORD='#########' CREATE ASYMMETRIC KEY UserEncryptionKey WITH ALGORITHM = RSA_2048 Now, when I run this on the production server, it creates the key just fine. However, when I run my sproc to get the password, it returns NULL. SQL: SELECT EncryptByAsymKey(AsymKey_ID('UserEncryptionKey'), Password ) FROM Users WHERE UserName = '######' Any thoughts on what I need to do to get the encrypted field to work on multiple SQL Servers? Please let me know if I need to clarify something. Thanks

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• C++ assignment question [closed]

  - by Adam Joof

  (Bubble Sort) In the bubble sort algorithm, smaller values gradually "bubble" their way upward to the top of the array like air bubbles rising in water, while the larger values sink to the bottom. The bubble sort makes several passes through the array. On each pass, successive pairs of elements are compared. If a pair is in increasing order (or the values are identical), we leave the values as they are. If a pair is in decreasing order, their values are swapped in the array. Write a program that sorts an array of 10 integers using bubble sort.

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• Why might different computers calculate different arithmetic results in VB.NET?

  - by Eyal

  I have some software written in VB.NET that performs a lot of calculations, mostly extracting jpegs to bitmaps and computing calculations on the pixels like convolutions and matrix multiplication. Different computers are giving me different results despite having identical inputs. What might be the reason? Edit: I can't provide the algorithm because it's proprietary but I can provide all the relevant operations: ULong \ ULong (Turuncating division) Bitmap.Load("filename.bmp') (Load a bitmap into memory) Bitmap.GetPixel(Integer, Integer) (Get a pixel's brightness) Double + Double Double * Double Math.Sqrt(Double) Math.PI Math.Cos(Double) ULong - ULong ULong * ULong ULong << ULong List.OrderBy(Of Double)(Func) Hmm... Is it possible that OrderBy is using a non-stable QuickSort and that QuickSort is using a random pivot? Edit: Just tested, nope. The sort is stable.

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• 50 sequences in one line

  - by user343934

  I have Muttiple sequence alignment (clustal) file and i want to read this file and arrange sequences in a such a way that in looks more clear and precise in order. I am doing this from biopython using AlignIO object. My codes like this alignment = AlignIO.read("opuntia.aln", "clustal") print "Number of rows: %i" % len(align) for record in alignment: print "%s - %s" % (record.id, record.seq) My Output-- http://i48.tinypic.com/ae48ew.jpg , it looks messy and long scrolling. What i want to do is print only 50 sequences in each line and continue till the end of alignment file. I wish to have output like this---http://i45.tinypic.com/4vh5rc.jpg from --http://www.ebi.ac.uk/Tools/clustalw2/, sorry two links are just a text due to my reputation. Any suggestions, algorithm and sample code is appreciated Thanks in advance Br,

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• Casting array of pointers to objects

  - by ritmbo

  If B is subclass of A. And I have in main(): B** b = new B*[10]; ... some algorithm that do b[i] = new B(..); ... So I have an array of pointers to objets B. Then I have a function: void f(A** foo); If in main, I do: f(b); I get a warning, but obviously if I do: f((A**)b);, i dont. The (A**) its a bit nasty. I was wondering if there's a more elegant way in C++ that at least do type checking as dynamic_cast.

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• set / line intersection solution

  - by Xavier

  I have two lists in python and I want to know if they intersect at the same index. Is there a mathematical way of solving this? For example if I have [9,8,7,6,5] and [3,4,5,6,7] I'd like a simple and efficient formula/algorithm that finds that at index 3 they intersect. I know I could do a search just wondering if there is a better way. I know there is a formula to solve two lines in y = mx + b form by subtracting them from each other but my "line" isn't truly a line because its limited to the items in the list and it may have curves. Any help is appreciated.

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• Google Web Optimizer -- How long until winning combination?

  - by Django Reinhardt

  I've had an A/B Test running in Google Web Optimizer for six weeks now, and there's still no end in sight. Google is still saying: "We have not gathered enough data yet to show any significant results. When we collect more data we should be able to show you a winning combination." Is there any way of telling how close Google is to making up its mind? (Does anyone know what algorithm does it use to decide if there's been any "high confidence winners"?) According to the Google help documentation: Sometimes we simply need more data to be able to reach a level of high confidence. A tested combination typically needs around 200 conversions for us to judge its performance with certainty. But all of our conversions have over 200 conversations at the moment: 230 / 4061 (Original) 223 / 3937 (Variation 1) 205 / 3984 (Variation 2) 205 / 4007 (Variation 3) How much longer is it going to have to run?? Thanks for any help.

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• Drawing bezier curve with limited subdivisions in OpenGL

  - by xEnOn

  Is it possible to tell OpenGL to draw a 4 degree (5 control points) bezier curve with 10 subdivisions? I was trying with this: point ctrlpts[] = {..., ..., ..., ...}; glMap1f(GL_MAP1_VERTEX_3, 0, 1, 3, 5, ctrlpts); glBegin(GL_LINE_STRIP); for (i = 0; i <= 30; i++) glEvalCoord1f((GLfloat) i/30.0); glEnd(); But this just draws the curve nicely. I am thinking that I want the algorithm inside the bezier curve to draw only until 10 subdivisions and then stop. The line should look a little facet.

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• Security & Authentication: SSL vs SASL

  - by 4herpsand7derpsago

  My understanding is that SSL combines an encryption algorithm (like AES, DES, etc.) with akey exchange method (like Diffier-Hellman) to provide secure encryption and identification services between two endpoints on an un-secure network (like the Internet). My understanding is that SASL is an MD5/Kerberos protocol that pretty much does the same thing. So my question: what are the pros/cons to choosing both and what scenarios make both more preferable? Basically, I'm looking for a guidelines to follow when choosing SSL or to go with SASL instead. Thanks in advance!

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• C++: call original definition of operator equals

  - by Luis Daniel

  I am overloading the operator equals (==) as show bellow: #include <string> #include <algorithm> bool operator == (std::string str1, std::string str2) { std::transform(str1.begin(), str1.end(), str1.begin(), ::tolower); std::transform(str2.begin(), str2.end(), str2.begin(), ::tolower); return (str1 == str2); } but, the problem appear on line return (str1 == str2), because operator == is called recursively. So, how can I call the original definition for operator equals (not the overloaded) ? Best regards

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• How do I visualize a complex graph in .Net?

  - by Ivan

  I need to visualize a graph (technically being a set of Entity Framework objects, but I can translate it to another representation if needed) of this kind. I don't know how to name it (by the way, if you know - I'll appreciate if you tell me). It would be ideal for graph elements to be clickable (so that when user clicks on a block, I can handle an event with the element id specified) but I can survive even without any interactivity. Are there any components available good for this task? If no, what should I look for to help me to develop an algorithm for drawing such a graph with visually-comfortable layout?

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• What is better for a student programming in C++ to learn for writing GUI: C# vs QT?

  - by flashnik

  I'm a teacher(instructor) of CS in the university. The course is based on Cormen and Knuth and students program algorithms in C++. But sometimes it is good to show how an algorithm works or just a result of task through GUI. Also in my opinion it's very imporant to be able to write full programs. They will have courses concerning GUI but a three years, later, in fact, before graduatuion. I think that they should be able to write simple GUI applications earlier. So I want to teach them it. How do you think, what is more useful for them to learn: programming GUI with QT or writing GUI in C# and calling unmanaged C++ library?

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• Python or matplotlib limitation error

  - by Werner

  Hi, I wrote an algorithm using python and matplotlib that generates histograms from some text input data. When the number of data input is approx. greater than 15000, I get in the (append) line of my code: mydata = [] for i in range(len(data)): mydata.append(string.atof(data[i])) the error: Traceback (most recent call last): File "get_histogram_picture.py", line 25, in <module> mydata.append(string.atof(data[i])) File "/usr/lib/python2.6/string.py", line 388, in atof return _float(s) ValueError: invalid literal for float(): -a can it be an error in python ? What is the solution ? Thanks

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• Portable Programming IDE

  - by Click Ok

  Frequently I'm brainstormed with programming ideas that I would like to directly code. More or less like "Wow, that algorithm will rock! I need to write it now!". For this kind of "impulse" to write, I use http://www.jarte.com/ that is a cool portable text editor. If I'm near a cybecafe or a friend computer, I just plug the usb pen drive and start to write... So, I would like: 1) a portable minimalist IDE 2) with minimal OS requirement (ie.: I want run from XP, Vista, etc...) 3) any modern language (I can learn a new language if needed. I just want write/test the algoritm) 4) Syntax Highlight/intellisense is good, but not required 5) Free Is there something like this?

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• Finding if a path between 2 sides of a game board exists

  - by Meny

  Hi, i'm currently working on a game as an assignment for school in java. the game cuurently is designed for Console. the game is for 2 players, one attacking from north to south, and the other from west to east. the purpose of the game is to build a "bridge"/"path" between the 2 of your sides before your opponent does. for example: A B C D E F 1 _ _ X _ _ _ 1 2 O X X _ _ _ 2 3 O X O O O O 3 4 O X O _ _ _ 4 5 X X _ _ _ _ 5 6 X O _ _ _ _ 6 A B C D E F player that attacks from north to south won (path/bridge from C to A) my problem is, what algorithm would be good to check if the user have managed to create a path (will be checked at the end of each turn). you're help would be very appreciated.

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• is it possible to dynamically set the level of for loop nesting

  - by galaxy

  I'm working out an algorithm to get permutations like 123 132 213 231 312 321 I'm doing it using nested foreach loops. for (..) { for(..) { for(..) { echo $i . $j . $k . "<br />"; } } } Problem is those # of nested loops are optimized for 3-spot permutations. How can I could I dynamically set the number of nested for loops to generate 4-letter or 5-letter permutations?

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• extract data from an array without using loop in R

  - by Manolo

  I have a vector v with row positions: v<-c(10,3,100,50,...) with those positions I want to extract elements of a matrix, having a column fixed, for example lets suppose my column number is 2, so I am doing: data<-c() data<-c(matrix[[v]][[2]]) matrix has the data in the following format: [[34]] [1] "200_s_at" "4853" "1910" "3554" "2658" So for example, I want to extract from the row 342 the value 1910 only, column 2, and do the same with the next rows but I got an error when I want to do that, is it possible to do it directly? or should I have a loop that read one by one the positions in v and fill the data vector like: #algorithm for i<-1 to length(v) pos<-v[i] data[[i]]<-c(matriz[[pos]][[2]]) next i Thanks

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• C#: Efficiently search a large string for occurences of other strings

  - by Jon

  Hi, I'm using C# to continuously search for multiple string "keywords" within large strings, which are = 4kb. This code is constantly looping, and sleeps aren't cutting down CPU usage enough while maintaining a reasonable speed. The bog-down is the keyword matching method. I've found a few possibilities, and all of them give similar efficiency. 1) http://tomasp.net/articles/ahocorasick.aspx -I do not have enough keywords for this to be the most efficient algorithm. 2) Regex. Using an instance level, compiled regex. -Provides more functionality than I require, and not quite enough efficiency. 3) String.IndexOf. -I would need to do a "smart" version of this for it provide enough efficiency. Looping through each keyword and calling IndexOf doesn't cut it. Does anyone know of any algorithms or methods that I can use to attain my goal?

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• "painting" one array onto another using python / numpy

  - by Nate

  I'm writing a library to process gaze tracking in Python, and I'm rather new to the whole numpy / scipy world. Essentially, I'm looking to take an array of (x,y) values in time and "paint" some shape onto a canvas at those coordinates. For example, the shape might be a blurred circle. The operation I have in mind is more or less identical to using the paintbrush tool in Photoshop. I've got an interative algorithm that trims my "paintbrush" to be within the bounds of my image and adds each point to an accumulator image, but it's slow(!), and it seems like there's probably a fundamentally easier way to do this. Any pointers as to where to start looking?

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• deleting and reusing a temp table in a stored precedure

  - by Sheagorath

  Hi I need to SELECT INTO a temp table multiple times with a loop but I just can't do it, because after the table created by SELECT INTO you can't simply drop the table at the end of the loop, because you can't delete a table and create it again in the same batch. so how can I delete a table in a stored procedure and create it again? is it possible to this without using a temp table? here is a snippet of where I am actualy using the temp table which is supposed to be a pivoting algorithm: WHILE @offset<@NumDays BEGIN SELECT bg.*, j.ID, j.time, j.Status INTO #TEMP1 FROM #TEMP2 AS bg left outer join PersonSchedule j on bg.PersonID = j.PersonID and bg.TimeSlotDateTime = j.TimeSlotDateTime and j.TimeSlotDateTime = @StartDate + @offset DROP TABLE #TEMP2; SELECT * INTO #TEMP2 FROM #TEMP1 DROP TABLE #TEMP1 SET @offset = @offset + 1 END

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• Gradients and memory

  - by user146780

  I'm creating a drawing application with OpenGL. I'v created an algorithm that generates gradient textures. I then map these to my polygons and this works quite well. What I realized is how much memory this requires. Creating 1000 gradients takes about 800MB and that's way too much. Is there an alternative to textures, or a way to compress them, or another way to map gradients to polygons that doesn't use up as much memory? Thanks My polygons are concave, I use GLUTesselator, and they are multicolored and point to point

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• Is Python appropriate for algorithms focused on scientific computing?

  - by gmatt

  My interests in programming lie mainly in algorithms, and lately I have seen many reputable researchers write a lot of their code in python. How easy and convenient is python for scientific computing? Does it have a library of algorithms that compares to matlab's? Is Python a scripting language or does it compile? Is it a great language for prototyping an algorithm? How long would it take me to learn enough of it to be productive provided I know C well and OO programming somewhat? Is it OO based? Sorry for the condensed format of questions, but I'm very curious and was hoping a more experienced programmer could help me out.

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• How secure are GUIDs in terms of predictability?

  - by ssg

  We're using .NET's Guid.NewGuid() to generate activation codes and API keys currently. I wonder if that poses a security problem since their algorithm is open. .NET Guid uses Win32 CoCreateGuid and I don't know it's internals (possibly MAC address + timestamp?). Can someone derive a second GUID out of the first one, or can he hit it with some smart guesses or is the randomness good enough so search space becomes too big? Generating random keys have the problem of collision, they need a double check before adding to a database. That's why we stuck with GUIDs but I'm unsure about their security for these purposes. Here are the 4 consecutive UUIDGEN outputs: c44dc549-5d92-4330-b451-b29a87848993 d56d4c8d-bfba-4b95-8332-e86d7f204c1c 63cdf958-9d5a-4b63-ae65-74e4237888ea 6fd09369-0fbd-456d-9c06-27fef4c8eca5 Here are 4 of them by Guid.NewGuid(): 0652b193-64c6-4c5e-ad06-9990e1ee3791 374b6313-34a0-4c28-b336-bb2ecd879d0f 3c5a345f-3865-4420-a62c-1cdfd2defed9 5b09d7dc-8546-4ccf-9c85-de0bf4f43bf0

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• Why does my program occasionally segfault when out of memory rather than throwing std::bad_alloc?

  - by Bradford Larsen

  I have a program that implements several heuristic search algorithms and several domains, designed to experimentally evaluate the various algorithms. The program is written in C++, built using the GNU toolchain, and run on a 64-bit Ubuntu system. When I run my experiments, I use bash's ulimit command to limit the amount of virtual memory the process can use, so that my test system does not start swapping. Certain algorithm/test instance combinations hit the memory limit I have defined. Most of the time, the program throws an std::bad_alloc exception, which is printed by the default handler, at which point the program terminates. Occasionally, rather than this happening, the program simply segfaults. Why does my program occasionally segfault when out of memory, rather than reporting an unhandled std::bad_alloc and terminating?

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