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• High speed matrix manipulation in c#?

  - by Donnie

  I'm working on some image manipulation code in c# and need to do some matrix operations (specifically 2D convolution). I have the code written in matlab which uses the conv2 function ... is there a library for C# / .NET that does good high-speed matrix manipulations? I'd be fine if it requires some specific GPU and does the matrix math on-GPU if that's what it takes.

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• PHP exec() and system() functions always return false in IIS

  - by Loftx

  Hi there, I'm trying to use the PHP exec() or system() (or any other similar function) to run a batch file, but I can't seem to get these to return anything. The simplest example I've seen is this, which outputs nothing: <?php echo system('dir'); ?> The script is running on a windows XP machine on IIS with PHP installed and I've also tried it on my shared hosting account running windows 2003 server/IIS. Can anyone suggest what I need to do to get this working, or provide any commands I can use for troubleshooting? Cheers, Tom

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• How to detect pending system shutdown on Linux?

  - by Rajorshi

  Hi, I am working on an app where I need to detect system shutdown. However, I have not found any reliable way get a notification on this event. I know that on shutdown, my app will receive a SIGTERM signal followed by a SIGKILL. What I want to know is if there is someway to query if a SIGTERM is part of a shutdown sequence? Does any one know if there is a way to query that programmatically (C API)? As far as I know, the system does not provide any other method to query for an impending shutdowm. If it does, that would solve my problem as well. I have been trying out runlevels as well, but change in runlevels seem to be instantaneous and without any prior warnings.

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• Numpy Matrix keeps giving me an Error,

  - by uberjumper

  Okay this is werid, i keep getting the error, randomly. ValueError: matrix must be 2-dimensional So i tracked it down, and cornered it to basically something like this: a_list = [[(1,100) for _ in range(32)] for _ in range(32)] numpy.matrix(a_list) Whats wrong with this? If i print a_list it is clearly a 2d matrix of tuples, however numpy does not believe so.

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• How can I save and read to XML the new C++ style matrix objects in OpenCV?

  - by neuviemeporte

  The old, C style cvMat matrices could be passed to the cvSave() function for easy writing to an XML file. The new C++ style cv::Mat and cv::Mat_ matrices are not accepted by this function. The OpenCV reference has a section on XML persistence, but the three classes (FileStorage, FileNode and FileNodeIterator) lack any description or example and I can't figure out how to use them from the interface. Thanks.

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• Issuing native system commands in Scala

  - by Tony

  I want to issue a native system command from a Scala program, and perhaps trap the output. ("ls" comes to mind. There may be other ways to get directory information without issuing the command, but that's beside the point of my question.) It would correspond to os.system(...) in Python. I've looked in "Programming in Scala". I've looked in O'Reilly's "Programming Scala". I've Googled several combinations of terms. No luck yet. Can someone out there give me an example, or point me at a resource where I can find an example?

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• Expert system for writing programs?

  - by aaa

  I am brainstorming an idea of developing a high level software to manipulate matrix algebra equations, tensor manipulations to be exact, to produce optimized C++ code using several criteria such as sizes of dimensions, available memory on the system, etc. Something which is similar in spirit to tensor contraction engine, TCE, but specifically oriented towards producing optimized rather than general code. The end result desired is software which is expert in producing parallel program in my domain. Does this sort of development fall on the category of expert systems? What other projects out there work in the same area of producing code given the constraints?

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• C++ Matrix class hierachy

  - by bpw1621

  Should a matrix software library have a root class (e.g., MatrixBase) from which more specialized (or more constrained) matrix classes (e.g., SparseMatrix, UpperTriangluarMatrix, etc.) derive? If so, should the derived classes be derived publicly/protectively/privately? If not, should they be composed with a implementation class encapsulating common functionality and be otherwise unrelated? Something else? I was having a conversation about this with a software developer colleague (I am not per se) who mentioned that it is a common programming design mistake to derive a more restricted class from a more general one (e.g., he used the example of how it was not a good idea to derive a Circle class from an Ellipse class as similar to the matrix design issue) even when it is true that a SparseMatrix "IS A" MatrixBase. The interface presented by both the base and derived classes should be the same for basic operations; for specialized operations, a derived class would have additional functionality that might not be possible to implement for an arbitrary MatrixBase object. For example, we can compute the cholesky decomposition only for a PositiveDefiniteMatrix class object; however, multiplication by a scalar should work the same way for both the base and derived classes. Also, even if the underlying data storage implementation differs the operator()(int,int) should work as expected for any type of matrix class. I have started looking at a few open-source matrix libraries and it appears like this is kind of a mixed bag (or maybe I'm looking at a mixed bag of libraries). I am planning on helping out with a refactoring of a math library where this has been a point of contention and I'd like to have opinions (that is unless there really is an objective right answer to this question) as to what design philosophy would be best and what are the pros and cons to any reasonable approach.

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• Implementation of a distance matrix of a binary tree that is given in the adjacency-list representation

  - by Denise Giubilei

  Given this problem I need an O(n²) implementation of this algorithm: "Let v be an arbitrary leaf in a binary tree T, and w be the only vertex connected to v. If we remove v, we are left with a smaller tree T'. The distance between v and any vertex u in T' is 1 plus the distance between w and u." This is a problem and solution of a Manber's exercise (Exercise 5.12 from U. Manber, Algorithms: A Creative Approach, Addison-Wesley (1989).). The thing is that I can't deal properly with the adjacency-list representation so that the implementation of this algorithm results in a real O(n²) complexity. Any ideas of how the implementation should be? Thanks.

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• building a pairwise matrix in scipy/numpy in Python from dictionaries

  - by user248237

  I have a dictionary whose keys are strings and values are numpy arrays, e.g.: data = {'a': array([1,2,3]), 'b': array([4,5,6]), 'c': array([7,8,9])} I want to compute a statistic between all pairs of values in 'data' and build an n by x matrix that stores the result. Assume that I know the order of the keys, i.e. I have a list of "labels": labels = ['a', 'b', 'c'] What's the most efficient way to compute this matrix? I can compute the statistic for all pairs like this: result = [] for elt1, elt2 in itertools.product(labels, labels): result.append(compute_statistic(data[elt1], data[elt2])) But I want result to be a n by n matrix, corresponding to "labels" by "labels". How can I record the results as this matrix? thanks.

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• HOW TO understand the programmming of operation system..!!!

  - by piemesons

  Hello, I want to learn the operating system. How it works. I dont want to make my own operating system. I just want to learn how it works. As i can find out source code of any open source OS. But how to start. Like stating from the first elementary kernal(what ever it is). Some body suggested me try to implement linux from scratch.etc etc.Please guide me in a proper way. i want to know about the proper path to follow. I am ready to invest three four years just to understand the basics. I am having good fundamentals of c c++,php, Oops, compiler design

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• i want to find determinant of 4x4 matrix in c#

  - by vj4u

  i want to find determinant of 4x4 matrix in c# please help urgent int ss = 4; int count = 0; int[,] matrix=new int[ss,ss]; ArrayList al = new ArrayList() {1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16 }; for (int i = 0; i < ss; i++) { for (int j = 0; j < ss; j++) { matrix[i, j] =Convert.ToInt32( al[count]); ++count; Response.Write(matrix[i, j] + " "); } Response.Write("<br/>"); }

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• Killing a script launched in a Process via os.system()

  - by L.J.

  I have a python script which launches several processes. Each process basically just calls a shell script: from multiprocessing import Process import os import logging def thread_method(n = 4): global logger command = "~/Scripts/run.sh " + str(n) + " >> /var/log/mylog.log" if (debug): logger.debug(command) os.system(command) I launch several of these threads, which are meant to run in the background. I want to have a timeout on these threads, such that if it exceeds the timeout, they are killed: t = [] for x in range(10): try: t.append(Process(target=thread_method, args=(x,) ) ) t[-1].start() except Exception as e: logger.error("Error: unable to start thread") logger.error("Error message: " + str(e)) logger.info("Waiting up to 60 seconds to allow threads to finish") t[0].join(60) for n in range(len(t)): if t[n].is_alive(): logger.info(str(n) + " is still alive after 60 seconds, forcibly terminating") t[n].terminate() The problem is that calling terminate() on the process threads isn't killing the launched run.sh script - it continues running in the background until I either force kill it from the command line, or it finishes internally. Is there a way to have terminate also kill the subshell created by os.system()?

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• System.Net.WebClient Class in .Net CompactFramework 3.5 ?

  - by Leen15

  Hi at all! I need to comunicate with a Server that give me async answers (streamer connection). I find this: http://msdn.microsoft.com/en-en/library/ms144211%28v=VS.80%29.aspx that generate this event: http://msdn.microsoft.com/en-en/library/system.net.webclient.openreadcompleted%28v=VS.80%29.aspx I think this is what i need, but i don't have the WebClient class in my System.Net of CompactFramework 3.5. How can i do? Thanks. EDIT: I've done a more clear question: httpRequest, httpResponse, send GET through Stream and Receive the Result in C#

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• Is the use of union in this matrix class completely safe?

  - by identitycrisisuk

  Unions aren't something I've used that often and after looking at a few other questions on them here it seems like there is almost always some kind of caveat where they might not work. Eg. structs possibly having unexpected padding or endian differences. Came across this in a math library I'm using though and I wondered if it is a totally safe usage. I assume that multidimensional arrays don't have any extra padding and since the type is the same for both definitions they are guaranteed to take up exactly the same amount of memory? template<typename T> class Matrix44T { ... union { T M[16]; T m[4][4]; } m; }; Are there any downsides to this setup? Would the order of definition make any difference to how this works?

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• R - indirectly calling a matrix using a string

  - by Boris Senderovich

  Example: There is a matrix of data called VE There is a vector of string where the first element is the string VE. I need to indirectly call the string and be able to access data. For example if I need the 6th column of matrix VE then I want to do: Vector[1][,6] Essentially I need R to start reading those string as if they are the matrix names that are already in this page. I need this syntax to be dynamic because I am putting it in a loop.

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• How do you concatenate the rows of a matrix into a vector in MATLAB?

  - by jimbo

  For an m-by-m (square) array, how do you concatenate all the rows into a column vector with size m^2 ?

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• pthreads recursively calling system command and segfault appears

  - by jess

  I have a code base where i am creating 8 threads and each thread just calls system command to display date in a continuous cycle, as shown below: void * system_thread(void *arg) { int cpu = (int)arg; printf("thread : start %d\n", cpu); for (;;) { // date ã³ãã³ãã®å®è¡ if (mode == 0) { system("date"); } else { f_hfp_nlc_Fsystem("date"); } } sleep(timerval); return NULL; } This application segfaults after running for 2-3 seconds, due to following 2 reasons: 1. read access, where the address is out of VM area 2. write acces, where it does not of write permission and its trying to modify some structure.

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• difference between system.out and system.err

  - by sap

  As i know both out and err are of same class printstream then can anybody tell me how they differe...how they changed there behaviour

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• DotNet Get User Operating System (HTTP_USER_AGENT)

  - by rockinthesixstring

  I'm looking at building an exhaustive function that returns a friendly name for the Users Operating System. I think I have most of the Windows stuff down, but I'm not sure about Linux, OSX, and others. Does anyone know where I can find an exhaustive list of HTTP_USER_AGENT's 'Gets the users operating system Public Shared Function GetUserOS() As String Dim strAgent As String = HttpContext.Current.Request.ServerVariables("HTTP_USER_AGENT") 'Windows OS's If InStr(strAgent, "Windows NT 6.1") Then : Return "Windows 7" ElseIf InStr(strAgent, "Windows NT 6.0") Then : Return "Windows Vista" ElseIf InStr(strAgent, "Windows NT 5.2") Then : Return "Windows Server 2003" ElseIf InStr(strAgent, "Windows NT 5.1") Then : Return "Windows XP" ElseIf InStr(strAgent, "Windows NT 5.0") Then : Return "Windows 2000" ElseIf InStr(strAgent, "Windows 98") Then : Return "Windows 98" ElseIf InStr(strAgent, "Windows 95") Then : Return "Windows 95" 'Mac OS's ElseIf InStr(strAgent, "Mac OS X") Then : Return "Mac OS X" 'Linux OS's ElseIf InStr(strAgent, "Linux") Then : Return "Linux" Else : Return "Unknown" End If End Function 'GetUserOS

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• How to understand the programming of an operating system

  - by piemesons

  Hello, I want to learn the operating system. How it works. I don't want to make my own operating system. I just want to learn how it works. As I can find out source code of any open source OS. But how to start. Like starting from the first elementary kernel (whatever it is). Somebody suggested I try to implement Linux from scratch etc. Please guide me in a proper way. I want to know about the proper path to follow. I am ready to invest three to four years just to understand the basics. I have good fundamentals of C, C++, PHP, OOP and compiler design.

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• Getting input in system() function (Mac)

  - by Alex

  #include <iostream> using namespace std; int main() { short int enterVal; cout << "enter a number to say: " << endl; cin >> enterVal; system("say "%d"") << enterVal; return 0; } Is what I am currently trying. I want the user to enter a number and the system() function says it basically. The code above has an error which says " 'd' was not declared in this scope ". Thanks in advance.

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• Find largest rectangle containing only zeros in an N&times;N binary matrix

  - by Rajendra

  Given an NxN binary matrix (containing only 0's or 1's), how can we go about finding largest rectangle containing all 0's? Example: I 0 0 0 0 1 0 0 0 1 0 0 1 II->0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 <--IV 0 0 1 0 0 0 IV is a 6×6 binary matrix; the return value in this case will be Cell 1: (2, 1) and Cell 2: (4, 4). The resulting sub-matrix can be square or rectangular. The return value can also be the size of the largest sub-matrix of all 0's, in this example 3 × 4.

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• Creating an email notification system based on polling database rows

  - by Ashish Sharma

  I have to design an email notification system based on the following requirements: The email notifications would be created based on polling rows in a Mysql 5.5 DB table when they are in a particular 'Completed' state. The email notification should be sent out in no more than 5 minutes from the time the row was created in the DB table (At the time of DB table row creation the state of the row might not be 'Completed'). Once 5 minutes for the DB table row expire in reaching the 'Completed' state, separate email notification need to be sent (basically telling the user that the original email notification would be delayed) and then sending the email notification as and when the row state reaches to being 'Completed'. The rest of the system requirements are : Adding relevant checks to monitor the whole system via MBeans interface. The system should be scalable so that if the rate of DB table rows creation increases so does the Email notification system be able to ramp up. So I request suggestions on following lines: What approach should I take in solving the problem described from a programming/Design pattern point of view? Suggestion for any third party plugin/software that can be used to solve the problem described? Points to take care regarding scalability and monitoring the health of the system? Java is the language of preference but I am open to using off the shelf components that can be interfaced with Java language or provide standard ports for communication. Currently I do have an in house grown system (written in Java) that is catering to the specified requirements, but it's now crumbling under increased load and now I want to give the problem a fresh look. thanks in advance Ashish

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• Bootloader error Ubuntu 12.04, system goes to Grub-rescue instead of booting

  - by user83508

  I am trying to install ubuntu 12.04 on my system but it is constantly giving me bootloader install fail error. I have tried to lot to solve this issue but reading articles over the internet but still no gain. Firstly since the bootloader was not getting installed I tried to install it on all the alternative paths given in the installer, failing with I selected install ubuntu without bootloader. Then I tried to manually install bootloader via terminal at try ubuntu via grub-install, but I was not able to do that. Then I tried using boot-repair and it was also not able to install the bootloader because after it my system shows grub-rescue. I tried to use boot-repair and install bootloader on a seperate partition mounted to /boot and still my system is booting and it still shows grub-rescue. The error which my system shows during boot is: Error : no such device : 04ac0510-bd4f-43b8-b885-b885-11c4dec21db8 I am not dual booting and ubuntu is the only OS I am installing. I am using Raid 0 with two blue western digital hard drive so I am not sure whether it is right or not. The details given by boot-repair are in the below mentioned link; http://paste.ubuntu.com/1147208/ Afterwards, I made one more change I installed ubuntu again and this time I installed the bootloader at a different partition on /boot. After this the bootloader error has gone but I am still not able to boot to ubuntu as I get the same error I was getting before. I have not installed dmraid, I feel it is neccessary for Raid0, but I thought ubuntu already has Raid drivers. Moreover in the dmraid installation instructions for 12.04, I used the one for 10.04 and selected to install bootloader at the partitions from the dropdown. This time the installation finished normally without an error but still I am not able to boot my system as the same error shows during booting this time also. Now I am stucked and I have no clue on how I can boot my system. Please tell me how can I boot my system.

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