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  • What Use are Threads Outside of Parallel Problems on MultiCore Systesm?

    - by Robert S. Barnes
    Threads make the design, implementation and debugging of a program significantly more difficult. Yet many people seem to think that every task in a program that can be threaded should be threaded, even on a single core system. I can understand threading something like an MPEG2 decoder that's going to run on a multicore cpu ( which I've done ), but what can justify the significant development costs threading entails when you're talking about a single core system or even a multicore system if your task doesn't gain significant performance from a parallel implementation? Or more succinctly, what kinds of non-performance related problems justify threading? Edit Well I just ran across one instance that's not CPU limited but threads make a big difference: TCP, HTTP and the Multi-Threading Sweet Spot Multiple threads are pretty useful when trying to max out your bandwidth to another peer over a high latency network connection. Non-blocking I/O would use significantly less local CPU resources, but would be much more difficult to design and implement.

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  • Excel Add-in memory explosion

    - by tsinik
    I wrote a small .NET add in to excel 2007 that read data from external c++ api and display it inside an excel. The task manager shows that I'm having a memory leak (the memory usage is inflate linearly up to 250MB after whitch it throws an "Excel cannot complete this task with available resources error") but the problem disappears as soon as I minimize the excel window. The api uses delegates to return data and I update it into a dictionary. another thread is updating the excel from the dictionary every second. It is unlikely that the unmanaged code is responsible of the leak. Does anybody have an idea what can cause this? 10x!

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  • C++: Trouble with Pointers, loop variables, and structs

    - by Rosarch
    Consider the following example: #include <iostream> #include <sstream> #include <vector> #include <wchar.h> #include <stdlib.h> using namespace std; struct odp { int f; wchar_t* pstr; }; int main() { vector<odp> vec; ostringstream ss; wchar_t base[5]; wcscpy_s(base, L"1234"); for (int i = 0; i < 4; i++) { odp foo; foo.f = i; wchar_t loopStr[1]; foo.pstr = loopStr; // wchar_t* = wchar_t ? Why does this work? foo.pstr[0] = base[i]; vec.push_back(foo); } for (vector<odp>::iterator iter = vec.begin(); iter != vec.end(); iter++) { cout << "Vec contains: " << iter->f << ", " << *(iter->pstr) << endl; } } This produces: Vec contains: 0, 52 Vec contains: 1, 52 Vec contains: 2, 52 Vec contains: 3, 52 I would hope that each time, iter->f and iter->pstr would yield a different result. Unfortunately, iter->pstr is always the same. My suspicion is that each time through the loop, a new loopStr is created. Instead of copying it into the struct, I'm only copying a pointer. The location that the pointer writes to is getting overwritten. How can I avoid this? Is it possible to solve this problem without allocating memory on the heap?

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  • LaTeX: Left aligning without extra space between words in tables

    - by goldfrapp04
    Here is the illustrating code: \documentclass[letterpaper, 10pt]{article} \usepackage[margin=1in]{geometry} \usepackage{array} \usepackage[none]{hyphenat} \begin{document} \begin{center} \begin{tabular}{|m{4.5cm}|m{1.2cm}<{\centering}|m{8cm}|c|} \hline \centering \textbf{Course Name} & \centering \textbf{Date} & \centering \textbf{Textbook} & \centering \textbf{Grade} \tabularnewline \hline C Programming Language \& Lab & 09/2009 - 12/2009 & Brian W. Kernighan, and Dennis M. Ritchie, \textit{The C Programming Language}, 2nd ed. ISBN:9780131103627 & 89 \\ \hline Integrative Practice on Courses & 07/2011 & LUPA, \textit{Linux Software Engineer}, ISBN:9787030199645 & 87 \\ \hline \end{tabular} \end{center} \end{document} As shown in the pdf generated, there are too much space between some words because I disabled automatic hyphenation. I'd like to leave only single space between words, without justify align. THANK YOU!

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  • How to discover table properties from SQLAlchemy mapped object

    - by ssaboum
    Hi, My point is i have a class mapped with a table, in my case in a declarative way, and i want to "discover" table properties, columns, names, relations, from this class : engine = create_engine('sqlite:///' + databasePath, echo=True) # setting up root class for declarative declaration Base = declarative_base(bind=engine) class Ship(Base): __tablename__ = 'ships' id = Column(Integer, primary_key=True) name = Column(String(255)) def __init__(self, name): self.name = name def __repr__(self): return "<Ship('%s')>" % (self.name) So now my goal is from the "Ship" class to get the table columns and their properties from another piece of code. I guess i can deal with it using instrumentation but is there any way provided by the SQLAlchemy API ? Thank you.

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  • Patterns for dynamic CMS components (event driven?)

    - by CitrusTree
    Sorry my title is not great, this is my first real punt at moving 100% to OO as I've been procedural for more years than I can remember. I'm finding it hard to understand if what I'm trying to do is possible. Depending on people's thoughts on the 2 following points, I'll go down that route. The CMS I'm putting together is quote small, however focuses very much on different types of content. I could easily use Drupal which I'm very comfortable with, but I want to give myself a really good reasons to move myself into design patterns / OO-PHP 1) I have created a base 'content' class which I wish to be able to extend to handle different types of content. The base class, for example, handles HTML content, and extensions might handle XML or PDF output instead. On the other hand, at some point I may wish to extend the base class for a given project completely. I.e. if class 'content-v2' extended class 'content' for that site, any calls to that class should actually call 'content-v2' instead. Is that possible? If the code instantiates an object of type 'content' - I actually want it to instantiate one of type 'content-v2'... I can see how to do it using inheritance, but that appears to involve referring to the class explicitly, I can't see how to link the class I want it to use instead dynamically. 2) Secondly, the way I'm building this at the moment is horrible, I'm not happy with it. It feels very linear indeed - i.e. get session details get content build navigation theme page publish. To do this all the objects are called 1-by-1 which is all very static. I'd like it to be more dynamic so that I can add to it at a later date (very closely related to first question). Is there a way that instead of my orchestrator class calling all the other classes 1-by-1, then building the whole thing up at the end, that instead each of the other classes can 'listen' for specific events, then at the applicable point jump in and do their but? That way the orchestrator class would not need to know what other classes were required, and call them 1-by-1. Sorry if I've got this all twisted in my head. I'm trying to build this so it's really flexible.

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  • Multiple layouts in rails [Newbie Q]

    - by BriteLite
    Hi. As a newb, I decided to build a "home inventory" application. I am now stuck on how to programmatically select a layout based on what type of item it is when viewing it in a browser. According to my planning, so far I should have created a few models to represent types of items I can find in my home: Furniture, Electronics and Books. class Book < ActiveRecord::Base end class Furniture < ActiveRecord::Base end class Electronic < ActiveRecord::Base end Now the Books model has things like isbn, pages, address, and category. Furniture model has things like color, price, address, and category. Electronics has things like name, voltage, address, and category. Here is where I got confused. I know the property address is going to be the same for all of them. I also know that, I will need to create multiple "layouts" for 3 different types of items to show the different properties of said items with appropriate graphics and stylesheets. But how will I go about deciding which category the item is so I can determine which layout to render. According to me, this is how I will do it: class DisplayController < ApplicationController def display @item = Params[:item] if @item.category = "electronics" render :layout => 'electronics' end end In my routes.rb map.display ':item', :controller => 'display', :action => 'display' I only seem to have one concern with this, I probably will add a lot of categories later on and think there should be a more DRY-esque way of dealing, rather than hardcoding them. I understand that I need to add into my layout html tags to display relevant information for that particular category. ----Questions---- Is this the right way to approach this type of problem. Will this approach be compatible when I decide to add a gem like *thinking_sphinx* to run search. What issues do you see with my approach and how can I make it better. I was reading something about "Polymorphic Assoc", does that apply in this case, since category exist for all items? Also, I was trying to get a routes to render a URL like "http://localhost/living-room-tv"

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  • passing parameter to view in IOS after a button is pressed

    - by ghostrider
    I am new to IOS programming. So far I have been programming in android. So in android when pressing a button code for passing an argument would be like that: Intent i = new Intent(MainScreen.this,OtherScreen.class); Bundle b = new Bundle(); b.putString("data_1",data); i.putExtras(b); startActivity(i); and on the activity that opens, i would write something like this: Bundle b = getIntent().getExtras(); ski_center=b.getString("data_1"); what methods should I need to change in MainScreen and in OtherScreen in IOS to achieve the above. Basically I will have 3 buttons lets say in my MainScreen and each of it will open the Otherview but each time a different parameter will be passed. Foe example for each button i have code like these in MainScreen.m @synthesize fl; -(IBAction) ifl:(id) sender { } So I need your help in where to place the "missing" code, too.

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  • Linux Kernel - Adding field to task_struct

    - by Drex
    I'm playing around with the linux kernel and added a struct field to the task_struct in sched.h. I know that can be costly but my struct is very small. I then initialize the new struct in INIT_TASK() and also re-initialize in fork.c copy_process() function so that when the INIT task or any other task creates a new process the process gets the init values. What then happens is when I try to run the kernel I get a SEGFAULT. The gdb error is: Locating the bottom of the address space ... Program received signal SIGSEGV, Segmentation fault. 0x08066ad7 in page_ok (page=) at arch/um/os-Linux/sys-i386/task_size.c:31 31 n = *address; It looks like it fails out in task_size. Is there anything else I need to do to add a field to task_struct?

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  • Hiredis waiting for message

    - by Vivek Goel
    I am using hiredis C library to connect to redis server. I am not able to figure out how to wait for new messages after subscribing to new message. My code look like: signal(SIGPIPE, SIG_IGN ); struct event_base *base = event_base_new(); redisAsyncContext *c = redisAsyncConnect("127.0.0.1", 6379); if (c->err) { /* Let *c leak for now... */ printf("Error: %s\n", c->errstr); return 1; } redisLibeventAttach(c, base); redisAsyncSetConnectCallback(c, connectCallback); redisAsyncSetDisconnectCallback(c, disconnectCallback); redisAsyncCommand(c, NULL, NULL, "SET key %b", argv[argc - 1], strlen(argv[argc - 1])); redisAsyncCommand(c, getCallback, (char*) "end-1", "GET key"); redisAsyncCommand(c, getCallback, (char*) "end-1", "SUBSCRIBE foo"); Now how to tell hiredis to wait for message on channel ?

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  • Catching KeyboardInterrupt when working with PyGame

    - by Sebastian P.
    I have written a small Python application where I use PyGame for displaying some simple graphics. I have a somewhat simple PyGame loop going in the base of my application, like so: stopEvent = Event() # Just imagine that this eventually sets the stopEvent # as soon as the program is finished with its task. disp = SortDisplay(algorithm, stopEvent) def update(): """ Update loop; updates the screen every few seconds. """ while True: stopEvent.wait(options.delay) disp.update() if stopEvent.isSet(): break disp.step() t = Thread(target=update) t.start() while not stopEvent.isSet(): for event in pygame.event.get(): if event.type == pygame.QUIT: stopEvent.set() It works all fine and dandy for the normal program termination; if the PyGame window gets closed, the application closes; if the application finishes its task, the application closes. The trouble I'm having is, if I Ctrl-C in the Python console, the application throws a KeyboardInterrupt, but keeps on running. The question would therefore be: What have I done wrong in my update loop, and how do I rectify it so a KeyboardInterrupt causes the application to terminate?

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  • are C functions declared in <c____> headers guaranteed to be in the global namespace as well as std?

    - by Evan Teran
    So this is something that I've always wondered but was never quite sure about. So it is strictly a matter of curiosity, not a real problem. As far as I understand, what you do something like #include <cstdlib> everything (except macros of course) are declared in the std:: namespace. Every implementation that I've ever seen does this by doing something like the following: #include <stdlib.h> namespace std { using ::abort; // etc.... } Which of course has the effect of things being in both the global namespace and std. Is this behavior guaranteed? Or is it possible that an implementation could put these things in std but not in the global namespace? The only way I can think of to do that would be to have your libstdc++ implement every c function itself placing them in std directly instead of just including the existing libc headers (because there is no mechanism to remove something from a namespace). Which is of course a lot of effort with little to no benefit. The essence of my question is, is the following program strictly conforming and guaranteed to work? #include <cstdio> int main() { ::printf("hello world\n"); } EDIT: The closest I've found is this (17.4.1.2p4): Except as noted in clauses 18 through 27, the contents of each header cname shall be the same as that of the corresponding header name.h, as specified in ISO/IEC 9899:1990 Programming Languages C (Clause 7), or ISO/IEC:1990 Programming Languages—C AMENDMENT 1: C Integrity, (Clause 7), as appropriate, as if by inclusion. In the C + + Standard Library, however, the declarations and definitions (except for names which are defined as macros in C) are within namespace scope (3.3.5) of the namespace std. which to be honest I could interpret either way. "the contents of each header cname shall be the same as that of the corresponding header name.h, as specified in ISO/IEC 9899:1990 Programming Languages C" tells me that they may be required in the global namespace, but "In the C + + Standard Library, however, the declarations and definitions (except for names which are defined as macros in C) are within namespace scope (3.3.5) of the namespace std." says they are in std (but doesn't specify any other scoped they are in).

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  • Where is a Web Development Career fueled by Passion? [closed]

    - by JMC Creative
    Quick Background Since learning basic html 5 years ago, I've become completely obsessed with the technology, the logic, and the thrill of solving problems involved with building websites. I am still stuck at a thoroughly non-programming type job, but would really like to move into the field of web programming/design. I have no educational background in the field (was trained as a fine artist and tutor), but in the past few years have progressed fully self-taught (and self-motivated) from html to css to php, mysql, jquery, and am now building rich web applications. The Question How can I prove to a company that even though I have no education, I have a passion to learn whatever is thrown my way? ...That essentially I would come at every issue with not only knowledge, but with a passionate desire to solve it, whether that means tackling a new language or debugging code for hours at a time? p.s. Sorry for the stupid title.

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  • rails data aggregation

    - by ash34
    Hi, I have to create a hash of the form h[:bill] = ["Billy", "NA", 20, "PROJ_A"] by login where 20 is the cumulative number of hours reported by the login for all task transactions returned by the query where each login has multiple reported transactions. Did I do this in a bad way or this seems alright. h = Hash.new Task.find_each(:include => [:user], :joins => :user, :conditions => ["from_date >= ? AND from_date <= ? AND category = ?", Date.today - 30, Date.today + 30, 'PROJ1']) do |t| h[t.login.intern] = [t.user.name, 'NA', h[t.login.intern].nil? ? (t.hrs_per_day * t.num_days) : h[t.login.intern][2] + (t.hrs_day * t.workdays), t.category] end Also if I have to aggregate this data not just by login but login and category how do I accomplish this? thanks, ash

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  • Should old/legacy/unused code be deleted from source control repository?

    - by Checkers
    I've encountered this in multiple projects. As the code base evolves, some libraries, applications, and components get abandoned and/or deprecated. Most people prefer to keep them in. The usual argument is that the code does not really take any space, it can be left alone until needed again. So a repository slowly turns into a cesspool of legacy code, where it's hard to find anything. Some people delete old code, since it creates clutter, raises more questions for new people, and you can restore any old snapshot of the code base anyway. However you can't always find the old code if you don't know where to look, as none of the (common) VCS I know offer search over the entire repository including all historical revisions, and the only way to search the old files is to check out the revision where the deleted file exists. What would be a good approach to repository management?

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  • Methodology for a Rails app

    - by Aaron Vegh
    I'm undertaking a rather large conversion from a legacy database-driven Windows app to a Rails app. Because of the large number of forms and database tables involved, I want to make sure I've got the right methodology before getting too far. My chief concern is minimizing the amount of code I have to write. There are many models that interact together, and I want to make sure I'm using them correctly. Here's a simplified set of models: class Patient < ActiveRecord::Base has_many :PatientAddresses has_many :PatientFileStatuses end class PatientAddress < ActiveRecord::Base belongs_to :Patient end class PatientFileStatus < ActiveRecord::Base belongs_to :Patient end The controller determines if there's a Patient selected; everything else is based on that. In the view, I will be needing data from each of these models. But it seems like I have to write an instance variable in my controller for every attribute that I want to use. So I start writing code like this: @patient = Patient.find(session[:patient]) @patient_addresses = @patient.PatientAddresses @patient_file_statuses = @patient.PatientFileStatuses @enrollment_received_when = @patient_file_statuses[0].EnrollmentReceivedWhen @consent_received = @patient_file_statuses[0].ConsentReceived @consent_received_when = @patient_file_statuses[0].ConsentReceivedWhen The first three lines grab the Patient model and its relations. The next three lines are examples of my providing values to the view from one of those relations. The view has a combination of text fields and select fields to show the data above. For example: <%= select("patientfilestatus", "ConsentReceived", {"val1"="val1", "val2"="val2", "Written"="Written"}, :include_blank=true )% <%= calendar_date_select_tag "patient_file_statuses[EnrollmentReceivedWhen]", @enrollment_complete_when, :popup=:force % (BTW, the select tag isn't really working; I think I have to use collection_select?) My questions are: Do I have to manually declare the value of every instance variable in the controller, or can/should I do it within the view? What is the proper technique for displaying a select tag for data that's not the primary model? When I go to save changes to this form, will I have to manually pick out the attributes for each model and save them individually? Or is there a way to name the fields such that ActiveRecord does the right thing? Thanks in advance, Aaron.

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  • Whats the deal with python?

    - 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 to read data between two html tags as text.

    - by vijay.shad
    Hi, I am working on a project which needs to extract text form a predefined div tag. My requirement is to send the content in the target div in a email body. I have to use javascript or php for this task. The Process : When a given link will be clicked; a javascript function will trigger and read that target div. The content of the div will be then submitted to server in dynamic form. What options I have to get this task done? Thanks.

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  • set map in google maps with TimerTask

    - by Chad White
    I would like to change the Position of the map in google maps v2 But Ive done it in a TimerTask ... target, zoom, bearing and so on and it says "IllegalStateException - not on the main thread What should I do? Any help? class Task extends TimerTask { @Override public void run() { CameraPosition cameraPosition = new CameraPosition.Builder() .target(Zt) // Sets the center of the map to Mountain View .zoom(12) // Sets the zoom .bearing(180) // Sets the orientation of the camera to east .tilt(30) // Sets the tilt of the camera to 30 degrees .build(); // Creates a CameraPosition from the builder mMap.moveCamera(CameraUpdateFactory.newCameraPosition(cameraPosition)); } } Timer timer = new Timer(); timer.scheduleAtFixedRate(new Task(), 0, 20000);

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  • What technologies are appropriate for a human workflow system?

    - by CCw
    I'm researching various workflow architectures and it is overwhelming. The workflow system I am creating will be almost completely human-driven. Very little, if any, asynchronous activity will be taking place. One possibility is to simply use a RDBMS and have a task table, from which stored procedures would be used to enforce synchronous access to each task. This seems very simple, but I'm having a hard time coming up with reasons why I might need to involve a heavier solution. If my system has ~500 concurrent users, and there is very little in the way of automated or asynchronous tasks, should I even consider the various workflow patterns/packages out there like Mule, BPEL/SOA, Spring Work Flow, etc?

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  • What is Perl's secret of getting small code do so much?

    - by sak
    I've seen many (code-golf) Perl programs out there and even if I can't read them (Don't know Perl) I wonder how you can manage to get such a small bit of code to do what would take 20 lines in some other programming language. What is the secret of Perl? Is there a special syntax that allows you to do complex tasks in few keystrokes? Is it the mix of regular expressions? I'd like to learn how to write powerful and yet short programs like the ones you know from the code-golf challenges here. What would be the best place to start out? I don't want to learn "clean" Perl - I want to write scripts even I don't understand anymore after a week. If there are other programming languages out there with which I can write even shorter code, please tell me.

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  • C# - LINQ Statements with OR clauses

    - by user70192
    Hello, I am trying to use LINQ to return a list of tasks that are in one of three states. These states are: 10 - Completed 11 - Incomplete 12 - Skipped The state is available through a property called "TaskStateID". I can do this in LINQ with just one state as shown here: var filteredTasks = from task in tasks select task; // Do stuff with filtered tasks string selectedComboBoxValue = GetFilterComboBoxValue(); if (selected ComboBoxValue == 3) { filteredTasks = filteredTasks.Where(p => p.TaskStateID == 10); // How do I use an 'OR' here to say p.TaskStateID == 10 OR p.TaskStateID == 11 OR p.TaskStateID == 12 } As shown in the comment above, how do I use an 'OR' in a LINQ statement to say p.TaskStateID == 10 OR p.TaskStateID == 11 OR p.TaskStateID == 12? Thank you

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  • Is this possible with Sql 2005 CTE?

    - by aenima1982
    I have been working on a query that will return a suggested start date for a manufacturing line based on due date and the number of minutes needed to complete the task. There is a calendar table(LINE_ID, CALENDAR_DATE, SCHEDULED_MINUTES) that displays per manufacturing line, the number of minutes scheduled for that day. Example: (Usually 3 shifts worth of time scheduled per day, no weekends but can vary) 1, 06/8/2010 00:00:00.000, 1440 1, 06/7/2010 00:00:00.000, 1440 1, 06/6/2010 00:00:00.000, 0 1, 06/5/2010 00:00:00.000, 0 1, 06/4/2010 00:00:00.000, 1440 In order to get the suggested start date, I need to start with the due date and iterate downward through the days until i have accumulated enough time to complete the task. My Question can something like this be done with CTE, or is this something that should be handled by a cursor. Or... am i just going about this the wrong way completely??

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