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  • How are SaaS applications organized?

    - by tomekw
    Consider web (MVC, for example Rails) application for multiple clients as a service. How to design this? one application instance per client? (+ one database per client) one instance for all clients (+ one database for all clients) Former one is simple, but... "inefficient". How about the latter? (best practises, design patterns) How to separate client data? For example: worker "A" of client "1" has two documents, worker "B" of client "2" has three documents. How to build model associations to protect other users (and clients) data? I think joining every query with Client model is not a good solution.

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  • Find Line Above or Below in Javascript

    - by Dark Falcon
    I am working on an in-place HTML editor, concentrating on Firefox only right now. I have an element inserted where the cursor should be and also have left and right arrows working, but I can't seem to find a way to find: Start and end of a line for the home and end keys The next line up or down for the up/down arrows. I see document.elementFromPoint, but this doesn't get me a Range object. The Range object itself seems rather useless when it comes to using pixel positions.

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  • How to calculate the average rgb color values of a bitmap

    - by Matthias
    In my C# (3.5) application I need to get the average color values for the red, green and blue channels of a bitmap. Preferably without using an external library. Can this be done? If so, how? Thanks in advance. Trying to make things a little more precise: Each pixel in the bitmap has a certain RGB color value. I'd like to get the average RGB values for all pixels in the image.

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  • How do you find out release, mailing list statistics information on open source projects

    - by Samuel
    We are interested in finding out some statistics of various frameworks Mailing list activity on say richfaces. Much similar to what is available on http://code.google.com (Low, Medium, High) + average number of emails per day | per month. Number of releases made in a year including patch, minor, major releases. We did look at the maven repositories but that wasn't very useful either. We did look at ohloh, but didn't get the desired information. Any other ideas on where to get this information (any maven-2 plugins)?

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  • Analysis services with non normalized table

    - by Uwe
    I have a table with several million rows. Each row represents a user session. There is a column called user which is not unique. There can be multiple sessions per user. I want to use Analysis services to get me the additional properties per user. Example: How many users (unique!) had a session longer than x minutes. How is that possible without changing the database. Note: there is no lookup-table and I cannot create one. What I am able of at the moment is to ask how many sessions were longer then x minutes.

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  • Ruby Rack: startup and teardown operations (Tokyo Cabinet connection)

    - by clint.tseng
    I have built a pretty simple REST service in Sinatra, on Rack. It's backed by 3 Tokyo Cabinet/Table datastores, which have connections that need to be opened and closed. I have two model classes written in straight Ruby that currently simply connect, get or put what they need, and then disconnect. Obviously, this isn't going to work long-term. I also have some Rack middleware like Warden that rely on these model classes. What's the best way to manage opening and closing the connections? Rack doesn't provide startup/shutdown hooks as I'm aware. I thought about inserting a piece of middleware that provides reference to the TC/TT object in env, but then I'd have to pipe that through Sinatra to the models, which doesn't seem efficient either; and that would only get be a per-request connection to TC. I'd imagine that per-server-instance-lifecycle would be a more appropriate lifespan. Thanks!

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  • Programmer Health - how to avoid going blind and sick!

    - by stefanyko
    Hi All! this is my very first time here! so nice to meet you guys! ;-) When i was starting with this job, ( when i have chosed of doing this for the rest of my life) i have thinked also, one day, before or after, i would become blind or at least sick by drinking 5 or more coffee per day and of course by sitting down on my pc for hours!!! ;-\ From many years now, i'm asking myself how my eyes can stay in front o the monitor for so many hours per day!? well now i'm to a point of no return!!! i feel my eyes each day more tired, and my productivity is waning, but i can't change work now and i don't want do this!!!! what i need to do for prevent this to become a more serious problem for me and for my eyes!? any suggestion will be really appreciated!!! Thanks!

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  • Programming graphics and sound on PC - Total newbie questions, and lots of them!

    - by Russel
    Hello, This isn't exactly specifically a programming question (or is it?) but I was wondering: How are graphics and sound processed from code and output by the PC? My guess for graphics: There is some reserved memory space somewhere that holds exactly enough room for a frame of graphics output for your monitor. IE: 800 x 600, 24 bit color mode == 800x600x3 = ~1.4MB memory space Between each refresh, the program writes video data to this space. This action is completed before the monitor refresh. Assume a simple 2D game: the graphics data is stored in machine code as many bytes representing color values. Depending on what the program(s) being run instruct the PC, the processor reads the appropriate data and writes it to the memory space. When it is time for the monitor to refresh, it reads from each memory space byte-for-byte and activates hardware depending on those values for each color element of each pixel. All of this of course happens crazy-fast, and repeats x times a second, x being the monitor's refresh rate. I've simplified my own likely-incorrect explanation by avoiding talk of double buffering, etc Here are my questions: a) How close is the above guess (the three steps)? b) How could one incorporate graphics in pure C++ code? I assume the practical thing that everyone does is use a graphics library (SDL, OpenGL, etc), but, for example, how do these libraries accomplish what they do? Would manual inclusion of graphics in pure C++ code (say, a 2D spite) involve creating a two-dimensional array of bit values (or three dimensional to include multiple RGB values per pixel)? Is this how it would be done waaay back in the day? c) Also, continuing from above, do libraries such as SDL etc that use bitmaps actual just build the bitmap/etc files into machine code of the executable and use them as though they were build in the same matter mentioned in question b above? d) In my hypothetical step 3 above, is there any registers involved? Like, could you write some byte value to some register to output a single color of one byte on the screen? Or is it purely dedicated memory space (=RAM) + hardware interaction? e) Finally, how is all of this done for sound? (I have no idea :) )

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  • Building a subquery with ARel in Rails3

    - by Christopher
    I am trying to build this query in ARel: SELECT FLOOR(AVG(num)) FROM ( SELECT COUNT(attendees.id) AS num, meetings.club_id FROM `meetings` INNER JOIN `attendees` ON `attendees`.`meeting_id` = `meetings`.`id` WHERE (`meetings`.club_id = 1) GROUP BY meetings.id) tmp GROUP BY tmp.club_id It returns the average number of attendees per meeting, per club. (a club has many meetings and a meeting has many attendees) So far I have (declared in class Club < ActiveRecord::Base): num_attendees = meetings.select("COUNT(attendees.id) AS num").joins(:attendees).group('meetings.id') Arel::Table.new('tmp', self.class.arel_engine).from(num_attendees).project('FLOOR(AVG(num))').group('tmp.club_id').to_sql but, I am getting the error: undefined method `visit_ActiveRecord_Relation' for #<Arel::Visitors::MySQL:0x9b42180> The documentation for generating non trivial ARel queries is a bit hard to come by. I have been using http://rdoc.info/github/rails/arel/master/frames Am I approaching this incorrectly? Or am I a few methods away from a solution?

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  • bmp image header doubts

    - by vikramtheone
    Hi Guys, I'm doing a project where I have to make use of the pixel information of a bmp image. So, I'm gathering the image information by reading the header information of the input .bmp image. I'm quite successful with everything but one thing bothers me, can any one here clarify it? The header information of my .bmp image is as follows (My test image is very tiny and gray scale)- BMP File header File size 1210 Offset information 1078 BMP Information header Image Header Size 40 Image Size 132 Image width 9 Image height 11 Image bits_p_p 8 So, from the .bmp header I see that the image size is 132 (bytes) but when I multiply the width and height it is only 99, how is such a thing possible? I'm confident with 132 bytes because when I subtract the Offset value with the File Size value, I get 132(1210 - 1078 = 132) and also when I manually count the number of bytes (In a HEX editor) from the point 1078 or 436h (End of the offset field), there are exactly 132 bytes of pixel information. So, why is there a disparity between the size filed and the (width x height)? My future implementations are dependent on the image width and height information and not on Image size information. So, I have to understand thoroughly whats going on here. My understanding of the header should be clearly wrong... I guess!!! Help!!! Regards Vikram My bmp structures are a as follows - typedef struct bmpfile_magic { short magic; }BMP_MAGIC_NUMBER; typedef struct bmpfile_header { uint32_t filesz; uint16_t creator1; uint16_t creator2; uint32_t bmp_offset; }BMP_FILE_HEADER; typedef struct { uint32_t header_sz; uint32_t width; uint32_t height; uint16_t nplanes; uint16_t bitspp; uint32_t compress_type; uint32_t bmp_bytesz; uint32_t hres; uint32_t vres; uint32_t ncolors; uint32_t nimpcolors; } BMP_INFO_HEADER;

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  • MVVM Binding Orthogonal Aspects in Views e.g. Application Settings

    - by chibacity
    I have an application which I am developing using WPF\Prism\MVVM. All is going well and I have some pleasing MVVM implementations. However, in some of my views I would like to be able to bind application settings e.g. when a user reloads an application, the checkbox for auto-scrolling a grid should be checked in the state it was last time the user used the application. My view needs to bind to something that holds the "auto-scroll" setting state. I could put this on the view-model, but applications settings are orthogonal to the purpose of the view-model. The "auto-scroll" setting is controlling an aspect of the view. This setting is just an example. There will be quite a number of them and splattering my view-models with properties to represent application settings (so I can bind them) feels decidedly yucky. One view-model per view seems to be de rigeuer... What is best\usual practice here? Splatter my view-models with application settings? Have multiple view-models per view so settings can be represented in their own right? Split views so that controls can bind to an ApplicationSettingsViewModel? = too many views? Something else? Edit 1 To add a little more context, I am developing a UI with a tabbed interface. Each tab will host a single widget and there a variety of widgets. Each widget is a Prism composition of individual views. Some views are common amongst widgets e.g. a file picker view. Whilst each widget is composed of several views, as a whole, conceptually a widget has a single set of user settings e.g. last file selected, auto-scroll enabled, etc. These need to be persisted and retrieved\applied when the application starts again, and the widget views are created. My question is focused on the fact that conceptually a widget has a single set of user settings which is at right-angles to the fact that a widget consists of many views. Each view in the widget has it's own view-model (which works nicely and logically) but if I stick to a one view-model per view, I would have to splatter each view-model with user settings appropriate to it. This doesn't sound right ?!?

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  • How do I destruct data associated with an object after the object no longer exists?

    - by Phineas
    I'm creating a class (say, C) that associates data (say, D) with an object (say, O). When O is destructed, O will notify C that it soon will no longer exist :( ... Later, when C feels it is the right time, C will let go of what belonged to O, namely D. If D can be any type of object, what's the best way for C to be able to execute "delete D;"? And what if D is an array of objects? My solution is to have D derive from a base class that C has knowledge of. When the time comes, C calls delete on a pointer to the base class. I've also considered storing void pointers and calling delete, but I found out that's undefined behavior and doesn't call D's destructor. I considered that templates could be a novel solution, but I couldn't work that idea out. Here's what I have so far for C, minus some details: // This class is C in the above description. There may be many instances of C. class Context { public: // D will inherit from this class class Data { public: virtual ~Data() {} }; Context(); ~Context(); // Associates an owner (O) with its data (D) void add(const void* owner, Data* data); // O calls this when he knows its the end (O's destructor). // All instances of C are now aware that O is gone and its time to get rid // of all associated instances of D. static void purge (const void* owner); // This is called periodically in the application. It checks whether // O has called purge, and calls "delete D;" void refresh(); // Side note: sometimes O needs access to D Data *get (const void *owner); private: // Used for mapping owners (O) to data (D) std::map _data; }; // Here's an example of O class Mesh { public: ~Mesh() { Context::purge(this); } void init(Context& c) const { Data* data = new Data; // GL initialization here c.add(this, new Data); } void render(Context& c) const { Data* data = c.get(this); } private: // And here's an example of D struct Data : public Context::Data { ~Data() { glDeleteBuffers(1, &vbo); glDeleteTextures(1, &texture); } GLint vbo; GLint texture; }; }; P.S. If you're familiar with computer graphics and VR, I'm creating a class that separates an object's per-context data (e.g. OpenGL VBO IDs) from its per-application data (e.g. an array of vertices) and frees the per-context data at the appropriate time (when the matching rendering context is current).

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  • Algorithm for finding symmetries of a tree

    - by Paxinum
    I have n sectors, enumerated 0 to n-1 counterclockwise. The boundaries between these sectors are infinite branches (n of them). The sectors live in the complex plane, and for n even, sector 0 and n/2 are bisected by the real axis, and the sectors are evenly spaced. These branches meet at certain points, called junctions. Each junction is adjacent to a subset of the sectors (at least 3 of them). Specifying the junctions, (in pre-fix order, lets say, starting from junction adjacent to sector 0 and 1), and the distance between the junctions, uniquely describes the tree. Now, given such a representation, how can I see if it is symmetric wrt the real axis? For example, n=6, the tree (0,1,5)(1,2,4,5)(2,3,4) have three junctions on the real line, so it is symmetric wrt the real axis. If the distances between (015) and (1245) is equal to distance from (1245) to (234), this is also symmetric wrt the imaginary axis. The tree (0,1,5)(1,2,5)(2,4,5)(2,3,4) have 4 junctions, and this is never symmetric wrt either imaginary or real axis, but it has 180 degrees rotation symmetry if the distance between the first two and the last two junctions in the representation are equal. Edit: This is actually for my research. I have posted the question at mathoverflow as well, but my days in competition programming tells me that this is more like an IOI task. Code in mathematica would be excellent, but java, python, or any other language readable by a human suffices. Here are some examples (pretend the double edges are single and we have a tree) http://www2.math.su.se/~per/files.php?file=contr_ex_1.pdf http://www2.math.su.se/~per/files.php?file=contr_ex_2.pdf http://www2.math.su.se/~per/files.php?file=contr_ex_5.pdf Example 1 is described as (0,1,4)(1,2,4)(2,3,4)(0,4,5) with distances (2,1,3). Example 2 is described as (0,1,4)(1,2,4)(2,3,4)(0,4,5) with distances (2,1,1). Example 5 is described as (0,1,4,5)(1,2,3,4) with distances (2). So, given the description/representation, I want to find some algorithm to decide if it is symmetric wrt real, imaginary, and rotation 180 degrees. The last example have 180 degree symmetry. (These symmetries corresponds to special kinds of potential in the Schroedinger equation, which has nice properties in quantum mechanics.)

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  • nginx-tornado-django request timeout

    - by Xie
    We are using nginx-tornado-django to provide web services. That is, no web page frontend. The nginx server serves as a load-balancer. The server has 8 cores, so we launched 8 tornado-django processes on every server. Memcached is also deployed to gain better performance. The requests per day is about 1 million per server. We use MySQL as backend DB. The code is tested and correct. Our profiling shows that normally every request are processed within 100ms. The problem is, we find that about 10 percent of the requests suffers from time-out issue. Many requests didn't even reach tornado. I really don't have much experience on tuning of nginx/tornado/MySQL. Right now I don't have a clue on what is going wrong. Any advise is appreiciated.

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  • Thread vs ThreadPool - .Net 2.0

    - by NLV
    Hello I'm not able to understand the difference between Thread vs ThreadPool. Consider i've to manipulate 50,000 records using threads. In case of threads i need to either predefine no of threads or no of records per threads. Either of them has to be constant. In case of threadpool we dont need to set any of them theoretically. But practically we need to assign the number of records per thread, because the no of threads may grow extremely large if the input no of records is huge. Any insights on this?

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  • How to generate GIR files from the Vala compiler?

    - by celil
    I am trying to create python bindings to a vala library using pygi with gobject introspection. However, I am having trouble generating the GIR files (that I am planning to compile to typelib files subsequently). According to the documentation valac should support generating GIR files. Compiling the following helloworld.vala public struct Point { public double x; public double y; } public class Person { public int age = 32; public Person(int age) { this.age = age; } } public int main() { var p = Point() { x=0.0, y=0.1 }; stdout.printf("%f %f\n", p.x, p.y); var per = new Person(22); stdout.printf("%d\n", per.age); return 0; } with the command valac helloworld.vala --gir=Hello-1.0.gir doesn't create the Hello-1.0.gir file as one would expect. How can I generate the gir file?

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  • SQL Complicated Group / Join by Category

    - by Mike Silvis
    I currently have a database structure with two important tables. 1) Food Types (Fruit, Vegetables, Meat) 2) Specific Foods (Apple, Oranges, Carrots, Lettuce, Steak, Pork) I am currently trying to build a SQL statement such that I can have the following. Fruit < Apple, Orange Vegetables < Carrots, Lettuce Meat < Steak, Port I have tried using a statement like the following Select * From Food_Type join (Select * From Foods) as Foods on Food_Type.Type_ID = Foods.Type_ID but this returns every Specific Food, while I only want the first 2 per category. So I basically need my subquery to have a limit statement in it so that it finds only the first 2 per category. However if I simply do the following Select * From Food_Type join (Select * From Foods LIMIT 2) as Foods on Food_Type.Type_ID = Foods.Type_ID My statement only returns 2 results total.

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  • Specification: Use cases for CRUD

    - by Mario Ortegón
    I am writing a Product requirements specification. In this document I must describe the ways that the user can interact with the system in a very high level. Several of these operations are "Create-Read-Update-Delete" on some objects. The question is, when writing use cases for these operations, what is the right way to do so? Can I write only one Use Case called "Manage Object x" and then have these operations as included Use Cases? Or do I have to create one use case per operation, per object? The problem I see with the last approach is that I would be writing quite a few pages that I feel do not really contribute to the understanding of the problem. What is the best practice?

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  • Why is changing displays slow?

    - by Josh Bronson
    I've had many laptops over the course of many years, and while many things have sped up, one thing remains as slow today as it was years ago: (dis)connecting an external display. What's taking it so long to detect the new display and update the pixel buffers? I use Macs primarily, but I think this is equally slow on other platforms.

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  • Geocode multiple addresses

    - by ace2600
    I need to geocode around 200 addresses per request and do around 3,000 request per day. I will be doing this server side using PHP. I have looked at http://stackoverflow.com/questions/98449/how-to-convert-an-address-to-a-latlon, but could not find a way for either Google Maps HTTP Request API or the Yahoo Geocoding REST API (cannot use JavaScript as this is server side) to send multiple addresses. I will be primarily using this to sort addresses based on the coordinates and if the API supports, fill in any missing data for each address. The addresses will be in the United States only. The addresses to geocode will be from user input, so be free form, like "street address, postal code", or "city, state", etc. Accuracy is not too important for the coordinates, say within five hundred feet or so. Is there a free API to handle this? Is there a way to get Yahoo or Google to do multiple locations in a request?

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  • Color separation in OpenCV?

    - by user225626
    Is there a function or a series of function steps that roughly equate to... get every pixel from myInput which doesn't meet an arbitrary Green quantity threshhold set each of those pixels to black on myOutput Thanks for any assistance.

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