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  • Does Python Django support custom SQL and denormalized databases with no Foreign Key relationships?

    - by Jay
    I've just started learning Python Django and have a lot of experience building high traffic websites using PHP and MySQL. What worries me so far is Python's overly optimistic approach that you will never need to write custom SQL and that it automatically creates all these Foreign Key relationships in your database. The one thing I've learned in the last few years of building Chess.com is that its impossible to NOT write custom SQL when you're dealing with something like MySQL that frequently needs to be told what indexes it should use (or avoid), and that Foreign Keys are a death sentence. Percona's strongest recommendation was for us to remove all FKs for optimal performance. Is there a way in Django to do this in the models file? create relationships without creating actual DB FKs? Or is there a way to start at the database level, design/create my database, and then have Django reverse engineer the models file?

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  • WPF Labels look fine in XP, but are cut off at the bottom in Vista and Windows 7.

    - by juharr
    The following xaml looks fine in XP, but the bottom of the text gets cut off in Vista and Windows 7. <Grid> <Border Height="86" Margin="10,54,10,0" VerticalAlignment="Top" BorderBrush="Black" BorderThickness="1"/> <Label Height="22" Width="100" Margin="15,43,0,0" VerticalAlignment="Top" HorizontalAlignment="Left" Background="White">Text Over Border</Label> </Grid> I realize that I could just increase the Height of the label, but I'm guessing I'll have problems with systems that have different resolution settings, or large text settings. Is there a better way to lay this out?

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  • Anyone Know a Great Sparse One Dimensional Array Library in Python?

    - by TheJacobTaylor
    I am working on an algorithm in Python that uses arrays heavily. The arrays are typically sparse and are read from and written to constantly. I am currently using relatively large native arrays and the performance is good but the memory usage is high (as expected). I would like to be able to have the array implementation not waste space for values that are not used and allow an index offset other than zero. As an example, if my numbers start at 1,000,000 I would like to be able to index my array starting at 1,000,000 and not be required to waste memory with a million unused values. Array reads and writes needs to be fast. Expanding into new territory can be a small delay but reads and writes should be O(1) if possible. Does anybody know of a library that can do it? Thanks!

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  • Diamonds Are Forever. Services Are Not.

    - by rayman
    Hi, ive read this article by Mark Murphy, while i was looking for a solution to my case. I have a Listener in my system, which suppose to get a UDP trigger times to times from an outside server, ive done this listener as a service. how could i prevent it being shut off by the user? (SDK 1.5), i`am working for a company which create cell phones, and we spread the device with this Listener. as soon as the listener goes off our systems will be terminated any idea for this scenario? *i`am already aware to the face, that the system could also take it off, but this case will be easier to handle and avoid. thanks, ray.

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  • How to split movie and play parts to look as a whole?

    - by luksow
    I'm writing software which is demonstraiting video on demand service. One of the feature is something similiar to IIS Smooth Streaming - I want to adjust quality to the bandwith of the client. My idea is, to split single movie into many, let's say - 2 seconds parts, in different qualities and then send it to the client and play them. The point is that for example first part can be in very high quality, and second in really poor (if the bandwith seems to be poor). The question is - do you know any software that allows me to cut movies precisly? For example ffmpeg splits movies in a way that join is visible and really annoying (seconds are the measure of precision). I use qt + phonon as a player if it matters. Or maybe you know any better way to provide such feature, without splitting movie into parts?

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  • Are there any good books on writing commercial quality software?

    - by Andy
    Hey, My background has been generally new technology demonstrators, which, well... demonstrate the latest technology and how it can be of use to a clients company. They use it for internal demos etc. Now my career has shiffed course a bit more into actual products, in particular software which runs in locations like museums as interactive pieces. Clearly, although the technology demonstrators had to be well coded etc, there wasn't as much emphasis as there is on my current work, which has to work, be highly configurable, probably multi-ligual and run constantly, without restarts. So my question is, now that I'm trying to up my coding quality and write more commercial applications, are there any books which discuss issues surrounding high quality commercial software? I currently have a copy of Code Complete 2nd Edition, which is excellent, but just wondering if there's any better, possibly more focused titles out there? Thanks a lot! Andy.

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  • In a virtual machine monitor such as VMware's ESXi Server, how are shadow page tables implemented?

    - by ali01
    My understanding is that VMMs such as VMware's ESXi Server maintain shadow page tables to map virtual page addresses of guest operating systems directly to machine (hardware) addresses. I've been told that shadow page tables are then used directly by the processor's paging hardware to allow memory access in the VM to execute without translation overhead. I would like to understand a bit more about how the shadow page table mechanism works in a VMM. Is my high level understanding above correct? What kind of data structures are used in the implementation of shadow page tables? What is the flow of control from the guest operating system all the way to the hardware? How are memory access translations made for a guest operating system before its shadow page table is populated? How is page sharing supported? Short of straight up reading the source code of an open source VMM, what resources can I look into to learn more about hardware virtualization?

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  • Question about varrying top margin when using custom Fonts on the iPhone.

    - by user170030
    I am using FontLabel to display varying lengths of texts in a custom font. I size the FontLabel using the following : CGSize size = [myString sizeWithFont:[UIFont systemFontOfSize:[[[UIApplication sharedApplication] delegate] getFontSize]] constrainedToSize:CGSizeMake(290, 4000) lineBreakMode:UILineBreakModeWordWrap]; For some reason, this always presents a Fontlabel where the text starts at a different space from the top. Sometimes the text begins at the correct location. Other times, it appears either too high or too low. Would appreciate some help in how to solve this issue.

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  • memcached cluster maintenance

    - by Yang
    Scaling up memcached to a cluster of shards/partitions requires either distributed routing/partition table maintenance or centralized proxying (and other stuff like detecting failures). What are the popular/typical approaches/systems here? There's software like libketama, which provides consistent hashing, but this is just a client-side library that reacts to messages about node arrivals/departures---do most users just run something like this, plus separate monitoring nodes that, on detecting failures, notify all the libketamas of the departure? I imagine something like this might be sufficient since typical use of memcached as a soft-state cache doesn't require careful attention to consistency, but I'm curious what people do.

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  • Writing custom Django form fields and widgets

    - by hekevintran
    Django has very good documentation that describes how to write custom database fields and custom template tags and filters. I cannot find the document that describes how to write custom form fields and widgets. Does this document exist? The way I've been able to write custom form fields and widgets is by reading the Django source code and imitating what I see there. I know that there are still things about implementing fields and widgets that I do not completely understand because I have not read any high level document that describes their interfaces.

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  • How can I avoid "Your system is running low on virtual memory" pop-up?

    - by Xavier Nodet
    Our application sometimes uses a lot of memory, and this is expected. But when we test it under high load on Windows XP, we usually get the very annoying "Your system is running low on virtual memory" popup, and this prevents our automated, unattended, tests to run through... Is it possible to prevent this popup to appear, and just have the allocation fail? The app will handle it gracefully, and tests will go on... We are using Windows XP, but if a solution only exists on later versions, I'd be happy to know anyway.

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  • What is the best method of assessment for computer science students?

    - by Gavimoss
    This question is a bit more philosophical so feel free to remove if you like but it's been bugging me for the last 4 years! As a final year student I find that exams can be often be passed with a couple of days of cramming, without necessarily retaining or understanding the content i.e. a regurgitation of lecture notes is often enough to gain high marks. A friend of mine is about to graduate with an honours degree whose final year evaluation was based solely on practical work (a project, assignment marks and the creation of a poster) yet all of this work could have been completed by a third party. Personally I don't think either of these methods of assessment is sufficient as I am currently on track for a 1st class honours in artificial intelligence and computer science and believe this is mostly due to my skill in passing exams not my skill as a programmer or my vast in depth knowledge of any of the subjects I have "studied". Surely there is a better way to assess our skills - isn't there?

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  • How would I implement separate databases for reading and writing operations?

    - by Matt
    I am interested in implementing an architecture that has two databases one for read operations and the other for writes. I have never implemented something like this and have always built single database, highly normalised systems so I am not quite sure where to begin. I have a few parts to this question. 1. What would be a good resource to find out more about this achitecture? 2. Is it just a question of replicating between two identical schemas, or would your schemas differ depending on the operations, would normalisation vary too? 3. How do you insure that data written to one database is immediately available for reading from the second? Any further help, tips, resources would be appreciated. Thanks.

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  • build a chrome extension in order to upload images (from clipboard)

    - by dayscott
    I wanted to write a simple chrome extension in order to substitute the following sequence of steps which i have to do very often for university: make screenshot of something edit screenshot in Paint save unnamend.png to harddrive upload unnamed.png to imageshack.us/pic-upload.de or any other website share link of image with others. I don't care which image upload service to use, i just want automize this use-case in order to save time (I already red and did a getting-started chrome extension and checked out their API, but that's it, this page: http://farter.users.sourceforge.net/blog/2010/11/20/accessing-operating-system-clipboard-in-chromium-chrome-extensions/ seemed useful, but i couldn't make it overwrite my systems clipboard - moreover i can't find a tutorial which helps me further).

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  • How sync the MYSQL database to remote server and from remote to desktop server

    - by qulzam
    I make a application, which has to interfaces. one is desktop and other is web application. both have their own databases (which are same is structure). I want to sync the database from desktop to remote server and also from remote server to desktop but i have no idea that how it does. I use the MYSql database. and my desktop application is in .NET NOTE: There are more than one destop systems who update their databases and also sync databases.

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  • iPhone - Drawing 2D with OpenGL ES, fast and simple.

    - by Johannes Jensen
    I'm going to make a game for the iPhone, and I'm mostly going to be using images. I've read that using Quartz only is slow for actual games with high frame rates, so I was wondering if you guys had any good ideas for using OpenGL for rendering a game scene? I'm going to be using a lot of images, and I want to be able to freely rotate them. I've looked at Apple's examples GLSprite and GLPaint, but I don't really see anything I could use. All I want to do is be able to render images at specific positions, and want to be able to rotate them. I'm a noob at OpenGL, but I know Quartz.

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  • Slow Client connection blocks Mongrel

    - by Sanjay
    I have a Apache + Haproxy + Mongrel setup for my rails application. When I hit a particular server page, mongrel takes around 100ms to process the request and I get the page in around 5 secs due to data transmission time on my slow home connection. Now I see that during these 5 secs of data transmission, mongrel does not serve any other request. I am surprised as that means mongrel is serving the response html to the client and is blocked till the client receives it. Shouldn't serving response be the job of Apache? This puts serious bottleneck in the no of requests Mongrel can serve as that would depend on the speed of the client connection. Is there any way that html generated by mongrel is served by apache/haproxy or any other web server like nginx? I wonder how the other high traffic sites are managing it?

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  • How is an SOA architecture really supposed to be implemented?

    - by smaye81
    My project is converting a legacy fat-client desktop application into the web. The database is not changing as a result. Consequently, we are being forced to call external web services to access data in our own database. Couple this with the fact that some parts of our application are allowed to access the database directly through DAOs (a practice that is much faster and easier). The functionality we're supposed to call web services for are what has been deemed necessary for downstream, dependent systems. Is this really how SOA is supposed to work? Admittedly, this is my first foray into the SOA world, but I have to think this is the complete wrong way to go about this.

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  • Ways to make your WCF services compatible with non-.NET consumers

    - by Mayo
    I'm working on adding a WCF services layer to my existing .NET application. This layer will be hosted in IIS and will be consumed by a variety of UIs, at least one of which will not use Microsoft technologies. I can make a Web service in WCF that is consumed by my .NET application. However, I'm concerned about things that work in the .NET world but not with other technologies. For example, simply throwing an exception from my WCF service works fine in .NET. But according to this article, one should approach exception handling with fault contracts to ensure compatibility with non-.NET consumers. The author labels this lack of foresight as The Fallacy of the .NET-Only World. Does anyone have any high level suggestions or links to articles that cover interoperability between WCF and non-.NET consumers? I realize I'm potentially working against the YAGNI principle. I'm only really looking to avoid things that will be incredibly difficult to overcome later when the developers of the non-.NET consumer report problems to me.

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  • How much trust can I put behind a computer system? How can I measure trust?

    - by danmine
    How much trust can I put in a standard computer running windows? To what certainty can I be sure it will run my code the way I wrote it? How can I be sure that if I declare something like "int j = 5;", j will alway be 5? Is there a way to measure trust in a standard x86 computer system? What kind of protections are there to make sure that j = 5? I'm thinking about critical systems where nothing can be off even by one bit and everything must run exactly the way it was written to run.

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  • c, pass awk syntax as argument to execl

    - by Skuja
    I want to run following command in c to read systems cpu and memory usage: ps aux|awk 'NR > 0 { cpu +=$3; ram+=$4 }; END {print cpu,ram}' I am trying to pass it to execl command and after that read its output: execl("/bin/ps", "/bin/ps", "aux|awk", "'NR > 0 { cpu +=$3; ram+=$4 }; END {print cpu,ram}'",(char *) 0); but in terminal i am getting following error: ERROR: Unsupported option (BSD syntax) I would like to know how to properly pass awk as argument to execl?

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  • SQL Function for On Balance Volume (Financial Query)

    - by CraigJSte
    I would like to create a function for On Balance Volume (SQL Function). This is too complex of a calculation for met to figure out but here is the outline of the User Defined Table Function. If someone could help me to fill in the blanks I would appreciate it. Craig CREATE FUNCTION [dbo].[GetStdDev3] (@TKR VARCHAR(10)) RETURNS @results TABLE ( dayno SMALLINT IDENTITY(1,1) PRIMARY KEY , [date] DATETIME , [obv] FLOAT ) AS BEGIN DECLARE @rowcount SMALLINT INSERT @results ([date], [obv]) // CREATE A FUNCTION FOR ON BALANCE VOLUME // On Balance Volume is the Summ of Volume for Total Periods // OBV = 1000 at Period = 0 // OBV = OBV Previous + Previous Volume if Close Previous Close // OBV = OBV Previous - Previous Volume if Close < Previous Close // OBV = OBV Previous if Close = Previous Close // The actual Value of OBV is not important so to keep the ratio low we reduce the // Total Value of Tickers by 1/10th or 1/100th // For Value of Volume = Volume * .01 if Volume < 999 // For Value of Volume = Volume * .001 If Volume = 999 FROM Tickers RETURN END This is the Tickers table [dbo].[Tickers]( [ticker] [varchar](10) NULL, [date] [datetime] NULL, [high] [float] NULL, [low] [float] NULL, [open] [float] NULL, [close] [float] NULL, [volume] [float] NULL, [time] [datetime] NULL, [change] [float] NULL )

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  • Using WCF to expose underlying process

    - by Steven
    I have a server application that spins up and monitors about 8 separate processes that gather data from different systems. The server app then runs some calculations over the aggregated data and stores it in a db. Simple stuff. I now have a requirement to modify the process so that it no longer saves data to the db but rather exposes it directly to clients via WCF. That's cool, I've used WCF a fair bit but I'm struggling a little with it for some reason. Basically my plan is to HOST the WCF service in my application and have calls redirect into the internals of my existing application but I can figure out how to do that without getting the WCF class to encapsulate the existing app. I want the service to inside my current app, not become it. Any suggestions?

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  • What strategies are efficient to handle concurrent reads on heterogeneous multi-core architectures?

    - by fabrizioM
    I am tackling the challenge of using both the capabilities of a 8 core machine and a high-end GPU (Tesla 10). I have one big input file, one thread for each core, and one for the the GPU handling. The Gpu thread, to be efficient, needs a big number of lines from the input, while the Cpu thread needs only one line to proceed (storing multiple lines in a temp buffer was slower). The file doesn't need to be read sequentially. I am using boost. My strategy is to have a mutex on the input stream and each thread locks - unlocks it. This is not optimal because the gpu thread should have a higher precedence when locking the mutex, being the fastest and the most demanding one. I can come up with different solutions but before rush into implementation I would like to have some guidelines. What approach do you use / recommend ?

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  • How do I keep JTextFields in a Java Swing BoxLayout from expanding?

    - by Matthew
    I have a JPanel that looks something like this: JPanel panel = new JPanel(); panel.setLayout(new BoxLayout(panel, BoxLayout.Y_AXIS)); ... panel.add (jTextField1); panel.add (Box.createVerticalStrut(10)); panel.add (jButton1); panel.add (Box.createVerticalStrut(30)); panel.add (jTextField2); panel.add (Box.createVerticalStrut(10)); panel.add (jButton2); ... //etc. My problem is that the JTextFields become huge vertically. I want them to only be high enough for a single line, since that is all that the user can type in them. The buttons are fine (they don't expand vertically). Is there any way to keep the JTextFields from expanding? I'm pretty new to Swing, so let me know if I'm doing everything horribly wrong.

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