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  • What are all the disadvantages of using files as a means of communicating between two processes?

    - by Manny
    I have legacy code which I need to improve for performance reasons. My application comprises of two executables that need to exchange certain information. In the legacy code, one exe writes to a file ( the file name is passed as an argument to exe) and the second executable first checks if such a file exists; if does not exist checks again and when it finds it, then goes on to read the contents of the file. This way information in transferred between the two executables. The way the code is structured, the second executable is successful on the first try itself. Now I have to clean this code up and was wondering what are the disadvantages of using files as a means of communication rather than some inter-process communication like pipes.Is opening and reading a file more expensive than pipes? Are there any other disadvantages? And how significant do you think would be the performance degradation. The legacy code is run on both windows and linux.

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  • More FP-correct way to create an update sql query

    - by James Black
    I am working on access a database using F# and my initial attempt at creating a function to create the update query is flawed. let BuildUserUpdateQuery (oldUser:UserType) (newUser:UserType) = let buf = new System.Text.StringBuilder("UPDATE users SET "); if (oldUser.FirstName.Equals(newUser.FirstName) = false) then buf.Append("SET first_name='").Append(newUser.FirstName).Append("'" ) |> ignore if (oldUser.LastName.Equals(newUser.LastName) = false) then buf.Append("SET last_name='").Append(newUser.LastName).Append("'" ) |> ignore if (oldUser.UserName.Equals(newUser.UserName) = false) then buf.Append("SET username='").Append(newUser.UserName).Append("'" ) |> ignore buf.Append(" WHERE id=").Append(newUser.Id).ToString() This doesn't properly put a , between any update parts after the first, for example: UPDATE users SET first_name='Firstname', last_name='lastname' WHERE id=... I could put in a mutable variable to keep track when the first part of the set clause is appended, but that seems wrong. I could just create an list of tuples, where each tuple is oldtext, newtext, columnname, so that I could then loop through the list and build up the query, but it seems that I should be passing in a StringBuilder to a recursive function, returning back a boolean which is then passed as a parameter to the recursive function. Does this seem to be the best approach, or is there a better one?

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  • Jquery each loop with json array

    - by Ben
    I'm trying to use Jquery's each loop to go through this Json and add it to a div named #contentHere. The Json is as follows: { "justIn": [ { "textId": "123", "text": "Hello", "textType": "Greeting" }, { "textId": "514", "text":"What's up?", "textType": "Question" }, { "textId": "122", "text":"Come over here", "textType": "Order" } ], "recent": [ { "textId": "1255", "text": "Hello", "textType": "Greeting" }, { "textId": "6564", "text":"What's up?", "textType": "Question" }, { "textId": "0192", "text":"Come over here", "textType": "Order" } ], "old": [ { "textId": "5213", "text": "Hello", "textType": "Greeting" }, { "textId": "9758", "text":"What's up?", "textType": "Question" }, { "textId": "7655", "text":"Come over here", "textType": "Order" } ] } I'm getting this Json through use of this code: $.get("data.php", function(data){ }) Any solutions?

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  • MPAPI vs MPI.NET vs ?

    - by Olexandr
    I'm working on college project. I have to develop distributed computing system. And i decided to do some research to make this task fun :) I've found MPAPI and MPI.NET libraries. Yes, they are .NET libraries(Mono, in my case). Why .NET ? I'm choosing between Ada, C++ and C# so to i've choosed C# because of lower development time. I have two goals: Simplicity; Performance; Cluster computing. So, what to choose - MPAPI or MPI.NET or something else ?

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  • Naming Suggestions For A Function Providing Chaining In A Different Way

    - by sid3k
    I've coded an experimental function which makes passed objects chainable by using high order functions. It's name is "chain" for now, and here is a usage example; chain("Hello World") (print) // evaluates print function by passing "Hello World" object. (console.log,"Optional","Parameters") (returnfrom) // returns "Hello World" It looks lispy but behaves very different since it's coded in a C based language, I don't know if there is a name for this idiom and I couldn't any name more suitable than "chain". Any ideas, suggestions?

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  • Persistent (purely functional) Red-Black trees on disk performance

    - by Waneck
    I'm studying the best data structures to implement a simple open-source object temporal database, and currently I'm very fond of using Persistent Red-Black trees to do it. My main reasons for using persistent data structures is first of all to minimize the use of locks, so the database can be as parallel as possible. Also it will be easier to implement ACID transactions and even being able to abstract the database to work in parallel on a cluster of some kind. The great thing of this approach is that it makes possible implementing temporal databases almost for free. And this is something quite nice to have, specially for web and for data analysis (e.g. trends). All of this is very cool, but I'm a little suspicious about the overall performance of using a persistent data structure on disk. Even though there are some very fast disks available today, and all writes can be done asynchronously, so a response is always immediate, I don't want to build all application under a false premise, only to realize it isn't really a good way to do it. Here's my line of thought: - Since all writes are done asynchronously, and using a persistent data structure will enable not to invalidate the previous - and currently valid - structure, the write time isn't really a bottleneck. - There are some literature on structures like this that are exactly for disk usage. But it seems to me that these techniques will add more read overhead to achieve faster writes. But I think that exactly the opposite is preferable. Also many of these techniques really do end up with a multi-versioned trees, but they aren't strictly immutable, which is something very crucial to justify the persistent overhead. - I know there still will have to be some kind of locking when appending values to the database, and I also know there should be a good garbage collecting logic if not all versions are to be maintained (otherwise the file size will surely rise dramatically). Also a delta compression system could be thought about. - Of all search trees structures, I really think Red-Blacks are the most close to what I need, since they offer the least number of rotations. But there are some possible pitfalls along the way: - Asynchronous writes -could- affect applications that need the data in real time. But I don't think that is the case with web applications, most of the time. Also when real-time data is needed, another solutions could be devised, like a check-in/check-out system of specific data that will need to be worked on a more real-time manner. - Also they could lead to some commit conflicts, though I fail to think of a good example of when it could happen. Also commit conflicts can occur in normal RDBMS, if two threads are working with the same data, right? - The overhead of having an immutable interface like this will grow exponentially and everything is doomed to fail soon, so this all is a bad idea. Any thoughts? Thanks! edit: There seems to be a misunderstanding of what a persistent data structure is: http://en.wikipedia.org/wiki/Persistent_data_structure

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  • Parsing language for both binary and character files

    - by Thorsten S.
    The problem: You have some data and your program needs specified input. For example strings which are numbers. You are searching for a way to transform the original data in a format you need. And the problem is: The source can be anything. It can be XML, property lists, binary which contains the needed data deeply embedded in binary junk. And your output format may vary also: It can be number strings, float, doubles.... You don't want to program. You want routines which gives you commands capable to transform the data in a form you wish. Surely it contains regular expressions, but it is very good designed and it offers capabilities which are sometimes much more easier and more powerful. Something like a super-grep which you can access (!) as program routines, not only as tool. It allows: joining/grouping/merging of results inserting/deleting/finding/replacing write macros which allows to execute a command chain repeatedly meta-grouping (lists-tables-hypertables) Example (No, I am not looking for a solution to this, it is just an example): You want to read xml strings embedded in a binary file with variable length records. Your tool reads the record length and deletes the junk surrounding your text. Now it splits open the xml and extracts the strings. Being Indian number glyphs and containing decimal commas instead of decimal points, your tool transforms it into ASCII and replaces commas with points. Now the results must be stored into matrices of variable length....etc. etc. I am searching for a good language / language-design and if possible, an implementation. Which design do you like or even, if it does not fulfill the conditions, wouldn't you want to miss ? EDIT: The question is if a solution for the problem exists and if yes, which implementations are available. You DO NOT implement your own sorting algorithm if Quicksort, Mergesort and Heapsort is available. You DO NOT invent your own text parsing method if you have regular expressions. You DO NOT invent your own 3D language for graphics if OpenGL/Direct3D is available. There are existing solutions or at least papers describing the problem and giving suggestions. And there are people who may have worked and experienced such problems and who can give ideas and suggestions. The idea that this problem is totally new and I should work out and implement it myself without background knowledge seems for me, I must admit, totally off the mark.

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  • How can i learn file name and create a folder?

    - by Phsika
    i try to make TCP/Ip Application to listen any other roemote computer to recieve any file. So i try to get files. i can do that. on the other hand every sample on google about giving SaveDialogBox to recived path folder.Forexample my old server.cs is that: using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.IO; using System.Net; using System.Net.Sockets; using System.Threading; namespace Server3 { public partial class Form1 : Form { Thread kanal; public Form1() { InitializeComponent(); try { kanal = new Thread(new ThreadStart(Dinle)); kanal.Start(); kanal.Priority = ThreadPriority.Normal; this.Text = "Kanal Çalisti"; } catch (Exception ex) { this.Text = "kanal çalismadi"; MessageBox.Show("hata:" + ex.ToString()); kanal.Abort(); throw; } } void Dinle() { TcpListener server = null; try { Int32 port = 51124; IPAddress localAddr = IPAddress.Parse("127.0.0.1"); server = new TcpListener(localAddr, port); server.Start(); Byte[] bytes = new Byte[1024 * 250000]; // string ReceivedPath = "C:/recieved"; while (true) { MessageBox.Show("Waiting for a connection... "); TcpClient client = server.AcceptTcpClient(); MessageBox.Show("Connected!"); NetworkStream stream = client.GetStream(); if (stream.CanRead) { saveFileDialog1.ShowDialog(); string pathfolder = saveFileDialog1.FileName; StreamWriter yaz = new StreamWriter(pathfolder); string satir; StreamReader oku = new StreamReader(stream); while ((satir = oku.ReadLine()) != null) { satir = satir + (char)13 + (char)10; yaz.WriteLine(satir); } oku.Close(); yaz.Close(); client.Close(); } } } catch (SocketException e) { Console.WriteLine("SocketException: {0}", e); } finally { // Stop listening for new clients. server.Stop(); } Console.WriteLine("\nHit enter to continue..."); Console.Read(); } private void Form1_Load(object sender, EventArgs e) { Dinle(); } } } i want to give automatically folder without SAVEDIALOGBOX. Also i want to learn my file name om my stream.Like that: using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.IO; using System.Net; using System.Net.Sockets; using System.Threading; namespace Server3 { public partial class Form1 : Form { Thread kanal; public Form1() { InitializeComponent(); try { kanal = new Thread(new ThreadStart(Dinle)); kanal.Start(); kanal.Priority = ThreadPriority.Normal; this.Text = "Kanal Çalisti"; } catch (Exception ex) { this.Text = "kanal çalismadi"; MessageBox.Show("hata:" + ex.ToString()); kanal.Abort(); throw; } } void Dinle() { TcpListener server = null; try { Int32 port = 51124; IPAddress localAddr = IPAddress.Parse("127.0.0.1"); server = new TcpListener(localAddr, port); server.Start(); Byte[] bytes = new Byte[1024 * 250000]; string ReceivedPath = "C:/recieved"; while (true) { MessageBox.Show("Waiting for a connection... "); TcpClient client = server.AcceptTcpClient(); MessageBox.Show("Connected!"); NetworkStream stream = client.GetStream(); if (stream.CanRead) { saveFileDialog1.ShowDialog(); string pathfolder = " i have to give property creating path and want to learn file name"; StreamWriter yaz = new StreamWriter(pathfolder); string satir; StreamReader oku = new StreamReader(stream); while ((satir = oku.ReadLine()) != null) { satir = satir + (char)13 + (char)10; yaz.WriteLine(satir); } oku.Close(); yaz.Close(); client.Close(); } } } catch (SocketException e) { Console.WriteLine("SocketException: {0}", e); } finally { // Stop listening for new clients. server.Stop(); } Console.WriteLine("\nHit enter to continue..."); Console.Read(); } private void Form1_Load(object sender, EventArgs e) { Dinle(); } } } Also i need : FileStream fs; FileInfo fi = new FileInfo(@"c:/recieved"); if (fi.Exists) fs = new FileStream(fi.FullName, FileMode.Append); else fs = new FileStream(fi.FullName, FileMode.Create); StreamWriter yazici = new StreamWriter(fs); How can i do that. Creating C:/recieved if it does not exist. And how can i learn File name on my network stream sending File Name.

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  • about python scripting

    - by kmitnick
    I have this code class HNCS (ThreadingTCPServer): def verify_request(self, request, client_address): for key in connections: if connections[key].client_address[0] == client_address[0]: if client_address[0] != '127.0.0.1': return False return True def welcome(self): return '''______________________________________________________ ------------------------------------------------------ %s ______________________________________________________ ------------------------------------------------------ * Server started %s * Waiting for connections on port %i ''' % (gpl, ctime(), PORT) I only can't figure out the line where it says if connections[key].client_address[0] == client_address[0] how come we used client_address as an attribute after dictionary???

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  • math library in gcc

    - by Betamoo
    I am writing a program on linux gcc... When I tried to include <math.h> I found that I need to link math library by using command gcc -lm But I am searching for another way to link the math library 'in code', that does not require the user to compile using any options.. Can gcc -lm be done in c code using #pragma or something? EDIT: I have changed -ml to -lm

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  • Best second language to learn for a native english speaking programmer?

    - by Tom Dignan
    I have always wanted to learn a foreign language, but I would like to pick one that can also help me the most in my career. I'm in the US, so it is not necessary for me to learn a second language to influence my career success, however I think knowing one and speaking it fluently could potentially put me in a more interesting career than if I did not. I would like to be able to travel the world, especially if I could have a reason to go one place or another. Which leads me to my question: What is the best second language to learn for a native English speaking programmer? (Especially from the US) Some ideas that come to mind for me are Mandarin, German, Japanese, French... I am looking for experienced opinions though! Thanks.

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  • Known "Z notation" applications ?

    - by Amadeus45
    I was just remembering back my university classes and was wondering to know if anyone out here even used the "Z notation" in a professional environment. I honestly must say that it was the single most boring class that I have ever attended in my life. Maybe because of the teacher, but at the time we really all thought it was a big waste of time. I might have been wrong, which is why I'd like to hear you about it. If you are using it or some derived language (Z++), I'd just like to know how is it useful for you. Just curious to know some commonly-known applications of Z or your application. For those who are not familiar : http://staff.washington.edu/jon/z/z-examples.html

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  • late binding in C

    - by benjamin button
    How can late binding can be achieved in c language? can anybody please provide an example. i think it can be achieved using dlopen and dlsym but i am not sure about it.please correct me if i am wrong!

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  • side effect gotchas in python/numpy? horror stories and narrow escapes wanted

    - by shabbychef
    I am considering moving from Matlab to Python/numpy for data analysis and numerical simulations. I have used Matlab (and SML-NJ) for years, and am very comfortable in the functional environment without side effects (barring I/O), but am a little reluctant about the side effects in Python. Can people share their favorite gotchas regarding side effects, and if possible, how they got around them? As an example, I was a bit surprised when I tried the following code in Python: lofls = [[]] * 4 #an accident waiting to happen! lofls[0].append(7) #not what I was expecting... print lofls #gives [[7], [7], [7], [7]] #instead, I should have done this (I think) lofls = [[] for x in range(4)] lofls[0].append(7) #only appends to the first list print lofls #gives [[7], [], [], []] thanks in advance

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  • Find three numbers appeared only once

    - by shilk
    In a sequence of length n, where n=2k+3, that is there are k unique numbers appeared twice and three numbers appeared only once. The question is: how to find the three unique numbers that appeared only once? for example, in sequence 1 1 2 6 3 6 5 7 7 the three unique numbers are 2 3 5. Note: 3<=n<1e6 and the number will range from 1 to 2e9 Memory limits: 1000KB , this implies that we can't store the whole sequence. Method I have tried(Memory limit exceed): I initialize a tree, and when read in one number I try to remove it from the tree, if the remove returns false(not found), I add it to the tree. Finally, the tree has the three numbers. It works, but is Memory limit exceed. I know how to find one or two such number(s) using bit manipulation. So I wonder if we can find three using the same method(or some method similar)? Method to find one/two number(s) appeared only once: If there is one number appeared only once, we can apply XOR to the sequence to find it. If there are two, we can first apply XOR to the sequence, then separate the sequence into 2 parts by one bit of the result that is 1, and again apply XOR to the 2 parts, and we will find the answer.

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  • How can I generate the Rowland prime sequence idiomatically in J?

    - by Gregory Higley
    If you're not familiar with the Rowland prime sequence, you can find out about it here. I've created an ugly, procedural monadic verb in J to generate the first n terms in this sequence, as follows: rowland =: monad define result =. 0 $ 0 t =. 1 $ 7 while. (# result) < y do. a =. {: t n =. 1 + # t t =. t , a + n +. a d =. | -/ _2 {. t if. d > 1 do. result =. ~. result , d end. end. result ) This works perfectly, and it indeed generates the first n terms in the sequence. (By n terms, I mean the first n distinct primes.) Here is the output of rowland 20: 5 3 11 23 47 101 7 13 233 467 941 1889 3779 7559 15131 53 30323 60647 121403 242807 My question is, how can I write this in more idiomatic J? I don't have a clue, although I did write the following function to find the differences between each successive number in a list of numbers, which is one of the required steps. Here it is, although it too could probably be refactored by a more experienced J programmer than I: diffs =: monad : '}: (|@({.-2&{.) , $:@}.) ^: (1 < #) y'

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  • Why do I not get the correct answer for Euler 56 in J?

    - by Gregory Higley
    I've solved 84 of the Project Euler problems, mostly in Haskell. I am now going back and trying to solve in J some of those I already solved in Haskell, as an exercise in learning J. Currently, I am trying to solve Problem 56. Let me stress that I already know what the right answer is, since I've already solved it in Haskell. It's a very easy, trivial problem. I will not give the answer here. Here is my solution in J: digits =: ("."0)":"0 eachDigit =: adverb : 'u@:digits"0' NB. I use this so often I made it an adverb. cartesian =: adverb : '((#~ #) u ($~ ([:*~#)))' >./ +/ eachDigit x: ^ cartesian : i. 99 This produces a number less than the desired result. In other words, it's wrong somehow. Any J-ers out there know why? I'm baffled, since it's pretty straightforward and totally brute force.

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  • Is it possible to call a user-space callback function from kernel space in Linux (ioctl)?

    - by Makis
    Is it possible to expand the ioctl interface in Linux so that the user-space application can send a pointer to a function to the kernel space driver? I'm in particular thinking of ways to handle the stream in user-controllable way but doing it in the kernel. Those operations could be attached to the kernel module but this would make development a lot easier as I wouldn't need to mess with the kernel during development. More specifically, this would be the process: Data is read by the driver to a buffer. Data is handled by these user-defined functions in place. Some more handling is done, possibly with some HW blocks. Data is used by a user-space application.

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  • Channels in Socket.io

    - by mat3001
    Hi, I am trying to broadcast a message through the Node.js service socket.io (http://socket.io/) to certain subset of all subscribers. To be more exact, I would like to use channels that users can subscribe to, in order to efficiently push messages to a couple hundred people at the same time. I'm not really sure if addEvent('channel_name',x) is the way to go. I have not found anything in the docs. Any ideas? Thanks Mat

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