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• Limit a process's relative (not absolute) processor consumption in Linux

  - by BobBanana

  What is the standard way in Linux to enforce a system policy to limit the relative CPU use of a single process? That is, on a quad-core machine, I never want a process to use more than 2 CPUs at once, even if the process creates more threads. I do not want an absolute time limit, just a relative limit so that one task cannot dominate the machine. This is also different than renice, which allows a process to use all the resources but just politely step aside if others need them too. ulimit is the usual resource limiting tool, but it does not allow such CPU restrictions.. it can limit the number of processes per user, or absolute CPU time, not restrict the maximum number of active threads of a single process. I've found a couple of user-level tools, like CPUlimit, but not a system level tool or setting. Does such a standard resource controller exist in Linux (Red Hat Enterprise, if it matters.) If there is such a limit imposed, how would a user identify it?

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• How to choose between Tell don't Ask and Command Query Separation?

  - by Dakotah North

  The principle Tell Don't Ask says: you should endeavor to tell objects what you want them to do; do not ask them questions about their state, make a decision, and then tell them what to do. The problem is that, as the caller, you should not be making decisions based on the state of the called object that result in you then changing the state of the object. The logic you are implementing is probably the called object’s responsibility, not yours. For you to make decisions outside the object violates its encapsulation. A simple example of "Tell, don't Ask" is Widget w = ...; if (w.getParent() != null) { Panel parent = w.getParent(); parent.remove(w); } and the tell version is ... Widget w = ...; w.removeFromParent(); But what if I need to know the result from the removeFromParent method? My first reaction was just to change the removeFromParent to return a boolean denoting if the parent was removed or not. But then I came across Command Query Separation Pattern which says NOT to do this. It states that every method should either be a command that performs an action, or a query that returns data to the caller, but not both. In other words, asking a question should not change the answer. More formally, methods should return a value only if they are referentially transparent and hence possess no side effects. Are these two really at odds with each other and how do I choose between the two? Do I go with the Pragmatic Programmer or Bertrand Meyer on this?

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• REST API wrapper - class design for 'lite' object responses

  - by sasfrog

  I am writing a class library to serve as a managed .NET wrapper over a REST API. I'm very new to OOP, and this task is an ideal opportunity for me to learn some OOP concepts in a real-life situation that makes sense to me. Some of the key resources/objects that the API returns are returned with different levels of detail depending on whether the request is for a single instance, a list, or part of a "search all resources" response. This is obviously a good design for the REST API itself, so that full objects aren't returned (thus increasing the size of the response and therefore the time taken to respond) unless they're needed. So, to be clear: .../car/1234.json returns the full Car object for 1234, all its properties like colour, make, model, year, engine_size, etc. Let's call this full. .../cars.json returns a list of Car objects, but only with a subset of the properties returned by .../car/1234.json. Let's call this lite. ...search.json returns, among other things, a list of car objects, but with minimal properties (only ID, make and model). Let's call this lite-lite. I want to know what the pros and cons of each of the following possible designs are, and whether there is a better design that I haven't covered: Create a Car class that models the lite-lite properties, and then have each of the more detailed responses inherit and extend this class. Create separate CarFull, CarLite and CarLiteLite classes corresponding to each of the responses. Create a single Car class that contains (nullable?) properties for the full response, and create constructors for each of the responses which populate it to the extent possible (and maybe include a property that returns the response type from which the instance was created). I expect among other things there will be use cases for consumers of the wrapper where they will want to iterate through lists of Cars, regardless of which response type they were created from, such that the three response types can contribute to the same list. Happy to be pointed to good resources on this sort of thing, and/or even told the name of the concept I'm describing so I can better target my research.

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• Creating movement path displays in a top-down 2d RTS

  - by nihohit

  My game is a top-down 2d RTS coded in C# using SFML's libraries. I want that during unit selection, a unit will display it's movement path on the map. Currently, after the path is computed as a list of directions ({left, up,down, down, down, left}, as an example), it's sent to the graphical component to create it's UI equivalent, and here I'm having some problems. current, these I've checked three ways to do it: compute the size of the image (in the example above it'll be a 3*2 rectangle) and create an invisible rectangle, and then go over the directions list and mark each spot with a visible point, so as to get a continous line. This system is slightly problematic because of the amount of large images that I need to save, but mostly because I have a lot of fine detail onscreen, and a continous line obstructs the view. again, compute the size of the image, but now create several (let's say 4) invisible images of that size, and then instead of a single continous line I'll switch between the four images, in each will appear only a fourth of the spots, in a way which creates a path animation. This is nicer on the eye, but here the memory demands, and the amount of time needed to compute each such image-loop is significant. Just create a list of single markers, each on a different spot on the path. This is very quick & easy on memory, but too sparse. Is there a simple or resource-light system to create path-animations?

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• How to unmangle PDF format into a usable text or spreadsheet document?

  - by Chuck

  Upon requesting some daily/hourly sales data from a coworker who is responsible for such requests, I was given a series of PDF files. The point of sale program that is used, for some reason, answers requests for this type of information in the form of PDF files. The issue: The PDF files look to be in a format that should easily be copy and pasted into a spreadsheet. There are three columns that look to be neatly organized across two pages. When copy/pasting the first page, all three columns from the PDF's first page are dumped into a single column consisting of the Date followed by the Hours for the transactions on that day. The end of this Date/Time information is followed by all of the Total Sales values that should be attached a Date and Time of the transaction. (NOTE: There are no duplicated Dates in the Date column, ie, Multiple transactions for a day only have one yyyy/mm/dd listed for the first row but not the following rows.) While it was a huge pain, it was possible to, in about four or five steps, get the single column of data broken out into three columns that matched the PDF. The second page of the PDF file, when attempting to copy/paste into a spreadsheet, creates a single column with the first third of the cells being the Dates from the PDF, the second third of the cells being the Hours of the transactions and the final third of the cells being filled with the Total Sales. After the copy/paste there is no way to figure out which Hours belong to which Dates or Total Sales due to the lack of the duplicated Dates in the Date column as mentioned above. My PDF-fu is next to non-existent. I've just now started to work with PDF editors and some www.convertmyPDFforfree.com websites, so far, with absolutely nothing remotely coming anywhere near usable output. (Both methods have so far done nothing but product blank documents.) Before I go back and pester my co-worker into figuring out a way to create a report in some other format than PDF, is there any method by which to take the data that looks to be formatted correctly in a PDF and copy/paste it into a spreadsheet that will look the same? I appreciate any help that can be made available. The sales data isn't so sensitive that I couldn't part with a bit to let somebody actually see what it is that needs to be dealt with, just let me know. The PDF's are less than 100kb each so sending them shouldn't be a burden to any interested party.

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• Syncing Large Directories/Filesystems using USB Drive

  - by Alan Lue

  Does anyone have a solution for syncing large directories/filesystems using just a USB flash drive (and specifically without using a network connection)? The objective is simply to sync a user directory between two computers. The contents of the user directory could amount to a large quantity of data—say, a quantity larger than could be stored on any single USB drive—but the aggregate size of changes that must be propagated by a single sync could easily fit on a USB drive. As an example, suppose a user directory is already synchronized between a desktop and a laptop computer. Here's a use case: Some changes are made in the user directory on the desktop. We mount a USB drive onto the desktop and copy whatever changes need to be applied to the laptop user directory in order to synchronize the desktop and laptop user directories. We now mount the USB drive onto the laptop and apply the changes. The desktop and laptop user directories are now synchronized. Any ideas? Alan

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• Linux mdadm software RAID 6 - does it support bit corruption recovery?

  - by user101203

  Wikipedia says "RAID 2 is the only standard RAID level, other than some implementations of RAID 6, which can automatically recover accurate data from single-bit corruption in data." Does anyone know if the RAID 6 mdadm implementation in Linux is one such implementation that can automatically detect and recover from single-bit data corruption. This pertains to CentOS / Red Hat 6 if those are different from other versions. I tried searching online but didn't have much luck. With SATA error rates being 1 in 1E14 bits, and a 2TB SATA disk containing 1.6E13 bits, this is especially relevant to preventing data corruption. Thanks!

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• Replace Certificate using Plesk 11

  - by Lambda Dusk

  I am not an admin, but a programmer. But how it is, if you're the only guy who knows about computers, everyone shoves those tasks to you. A certificate of a domain recently expired. The domains are managed using Plesk 11, on a Linux system, Apache2.2. I was given a new certificate from the host, and it is one single .pem file. However, Plesk asks me for a .crt file, a private key and some CA file. I have neither, only this single .pem file the host claims to be the certificate. Since I myself never did anything with SSL certificates, I would really appreciate if anyone can tell me what to do with this file and how to properly add a new one so the old one can be removed.

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• creating video from set of images on windows with java language [on hold]

  - by Atif

  I am stuck in making video from set of images, i am using ffmpeg tool on windows platform with java language, for single image it is converting into mp4 but for the set of images it gets failed, i have converted single % to double % with doube quotes but unsuccessful ffmpeg -r 1/5 -i "D:\novoworkspace\MGram\src\biz\novosol\mgram\main\img%%04d.jpg" -c:v libx264 -r 30 -pix_fmt yuv420p D:\novoworkspace\MGram\src\biz\novosol\mgram\main\video.mp4 Above is the exact command i tried from the command line as well from the java language with getRuntime() method. Environment is widows please suggest is it possibe under windows or I have to use some alternative Thanks Atif

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• GLSL custom interpolation filter

  - by Cyan

  I'm currently building a fragment shader which is using several textures to render the final pixel color. The textures are not really textures, they are in fact "input data" to be used in the formula to generate the final color. The problem I've got is that the texture are getting bi-linear-filtered, and therefore the input data as well. This results in many unwanted side-effects, especially when final rendered texture is "zoomed" compared to original resolution. Removing the side effect is a complex task, and only result in "average" rendering. I was thinking : well, all my problems seems to come from the "default" bi-linear filtering on these input data. I can't move to GL_NEAREST either, since it would create "blocky" rendering. So i guess the better way to proceed is to be fully in charge of the interpolation. For this to work, i would need the input data at their "natural" resolution (so that means 4 samples), and a relative position between the sampled points. Is that possible, and if yes, how ? [EDIT] Since i started this question, i found this internet entry, which seems to (mostly) answer my needs. http://www.gamerendering.com/2008/10/05/bilinear-interpolation/ One aspect of the solution worry me though : the dimensions of the texture must be provided in an argument. It seems there is no way to "find this information transparently". Adding an argument into the rendering pipeline is unwelcomed though, since it's not under my responsibility, and translates into adding complexity for others.

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• Isn't Java a quite good choice for desktop applications?

  - by tactoth

  At present most applications are still developed with C++, painfully. Lack of portability, in compatible libraries, memory leaks, slow compilation, and poor productivity. Even if you pick only a single from these shortages, it's still a big headache. However the surprising truth is that C++ remains the first choice for desktop applications. Compared to C++ Java has lots of advantages. The success in server side development shows that the language itself is good, Swing is also thought to be as programmer friendly as the highly recognized QT framework (No, never say even a single word about MFC!). All the disadvantages of C++ listed above has a solution in Java. "Performance!", Well that might still be the problem but to my experience it's a slight problem. I'd been using Java to decode some screen video and generate key frames. The video has a duration of more than 1 hour. The time spent on an average machine is just 1 minute. With C++ I don't expect even faster speed. In recent days there are many news on the JIT performance improvements, that make us feel Java is gradually becoming very suitable for desktop development, without people realizing it. Isn't it?

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• Backup all plesk MySQL Databases to individual files

  - by Michael

  Hy, Because I'm new to shell scripting I need a hand. I currently backup all mydatabases to a single file, thing that makes the restore preaty hard. The second problem that my MySQL password dosen't work because of a Plesk bug and i get the password from "/etc/psa/.psa.shadow". Here is the code that I use to backup all my databases to a single file. mysqldump -uadmin -p`cat /etc/psa/.psa.shadow` --all-databases | bzip2 -c > /root/21.10.2013.sql.bz2 I found some scripts on the web that backup each database to individual files but I don't know how to make them work for my situation. Here is a example script: for db in $(mysql -e 'show databases' -s --skip-column-names); do mysqldump $db | gzip > "/backups/mysqldump-$(hostname)-$db-$(date +%Y-%m-%d-%H.%M.%S).gz"; done Can someone help me make the script above work for my situation? Requirements: Backup each database to individual file using plesk password location.

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• Tar an gzip together, but the other way round?

  - by Boldewyn

  Gzipping a tar file as whole is drop dead easy and even implemented as option inside tar. So far, so good. However, from an archiver's point of view, it would be better to tar the gzipped single files. (The rationale behind it is, that data loss is minified, if there is a single corrupt gzipped file, than if your whole tarball is corrupted due to gzip or copy errors.) Has anyone experience with this? Are there drawbacks? Are there more solid/tested solutions for this than find folder -exec gzip '{}' \; tar cf folder.tar folder

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• Merging two sites into one, how to redirect from the domain that's going away?

  - by bikeboy389

  I haven't been able to find any existing questions that cover my exact issue, so here goes: My client wants her two sites (domain1.com and domain2.com) rolled into a single, new site under domain1.com. Once the site is ready on domain1.com, DNS for domain2.com would be pointed at the same server as domain1.com. I know how to do an htaccess rewrite rule that would make all domain2.com traffic map to a specific single page or directory within domain1.com. But that's not what the client wants. What she wants is for a bunch of specific pages on domain2.com to map to specific new pages on domain1.com. For example: domain2.com/index.php?pageid=58 GOES TO domain1.com/2011/04/somearticle domain2.com/index.php?pageid=92 GOES TO domain1.com/2011/03/differentname etc. I could put a bunch of 301 redirects in the htaccess on domain1.com, which would work fine. The problem is, the client doesn't want/need specific redirects for ALL the domain2.com pages, and if I just do 301 redirects, anybody who comes looking for a domain2.com page that I haven't built a specific redirect for will get a 404 error. So I need to use 301 redirects for some traffic, and a rewrite rule for any traffic that's not covered in the 301 redirects. How do I do sort of a blending of a rewrite rule and 301 redirects, all in the htaccess file for domain1.com? Is this possible? Is it as simple as putting the 301 redirects in the htaccess file first, then doing the rewrite rule? I'm guessing not.

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• Combining multiple linux boxes and create VMs out of it

  - by NS Gopikrishnan

  I am new to virtualization. I am running on ubuntu. I have a set of linux machines (5 to 6 machines). Which I want to combine as a single resource pool and on demand create multiple virtual instances of machines out of it. This is comparable to what VirtualBox does in a single system. I stumbled across many key words: Xen, Eucalyptus, OpenStack etc. But things are very vague as to which will help me achieve this requirement. Any help will be appreciated :) Thanks in advance!

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• is using Hosts for resolving a sql-server more performant?

  - by Ice

  Hi, we have a legacy application which uses a access.mdb with hundreds of ODBC-connected tables on a sql-server. the access.mdb contains nothing else than these odbc-connections. Now we consider to use a virtual sql-servername for these odbc connections and resolve it in the local hosts-file with the ip-address of the real sql-server. Like this we can easy switch between a test-sql-database server and the the server for production in changing one single entry in the hosts. EVERYTHING works fine and now comes the question: Could it be that this is more performant because there is one single point on resolving the sql-server (name or ip-address)? Is there something like a network-cache / DNS-Cache? peace Ice

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• In developing a soap client proxy, which return structure is easier to use and more sensible?

  - by cori

  I'm writing (in PHP) a client/proxy for a SOAP web service. The return types are consistently wrapped in response objects that contain the return values. In many cases this make a lot of sense - for instance when multiple values are being returned: GetDetailsResponse Object ( Results Object ( [TotalResults] => 10 [NextPage] => 2 ) [Details] => Array ( [0] => Detail Object ( [Id] => 1 ) ) ) But some of the methods return a single scalar value or a single object or array wrapped in a response object: GetThingummyIdResponse Object ( [ThingummyId] => 42 ) In some cases these objects might be pretty deep, so getting at properties within requires drilling down several layers: $response->Details->Detail[0]->Contents->Item[5]->Id And if I unwrap them before passing them back I can strip out a layer from consumers' code. I know I'm probably being a little bit of an Architecture Astronaut here, but the latter style really bug me, so I've been working through my code to have my proxy methods just return the scalar value to the client code where there's no absolute need for a wrapper object. My question is, am I actually making things more difficult for the consumers of my code? Would I be better off just leaving the return values wrapped in response objects so that everything is consistent, or is removing unneccessary layers of indirection/abstraction worthwhile?

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• Windows 7 search for files with special characters in name.

  - by Luke

  I have a rather large source code repository on my machine; it is not indexed by Windows Search. I am trying to find some oddly-named generated files of the form .#name.extension.version where name and extension are normal names and extensions and version is a numeric value (e.g. something like 1.186). On Windows XP I could find these files by searching for .#*; on Windows 7 that just returns every single file and directory. So my question is this: is it possible to find files named like that using the built-in Windows 7 search functionality? I did find this question which is very similar, but the answer doesn't work for me; it seems like any special character I put in the query is either ignored or treated as a wildcard, and as a result it matches every single file and directory. Is there perhaps some registry value I can set to make the search-by-filename feature work with special characters?

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• phpmyadmin or other mysql gui - edit whole table from one screen

  - by lorem

  Let's say I have table in database. I'd like to be able to view all data from this table and be able to edit every field from single screen. I tried to do this in phpmyadmin but I'm not sure how... I can see all data but I have to click edit on single field and then I'm sent to next screen, can't really edit everything at once. How do I do this in phpmyadmin or other mysql gui? I'm on Linux, my server too. I'd like each field in table to be editable text field - maybe this will show better what I'm searching for.

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• Managing Windows 7 Workstations

  - by ethamoose

  There was a similar thread to this a few years back, but without any solutions. Just wondering if things have moved on since then. I'm primarily an Mac admin working in a college, but I have recently taken over responsibility for about 30 student workstations running Windows 7. For the Macs I have Apple Remote Desktop, where I can logon to machines in a session,check for any nefarious student activity and if necessary, log off or lock users out of machines. Could anyone give me a suggestion for an equivalent Windows system manager where I can do these tasks - e.g. not just a vnc client but one with more management options?

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• Encrypt two drives with Truecrypt with password before boot

  - by Deshroom

  i'm using laptop and PC with single HDD with full disk encryption. I know how works truecrypt on single drive because i use it everyday. My second laptop has 2 HHDs. My question is how to encrypt first 128GB SSD and second 1TB HDD in same way. I have multiple applications installed on second drive so i want to have it accessible during boot in ex. Steam in installed on second drive and it starts with windows. How to do it? can i encrypt two drives in truecrypt and unlock it via password before boot? My main reason is i want to RMA laptop without removing disks or data - my data need to be encrypted. Thank you.

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• Best approach for tracking dependent state

  - by Pace

  Let's pretend I work on a project tracking application. The application is a database backed, server hosted, web application. In this application there are Projects which have many Activities which have many Tasks. A Task has two date fields an originalDueDate and a projectedDueDate. In addition, there are dynamic fields on the Activities and the Projects which indicate whether the Activity or Project is behind schedule based on the projected due dates of the child tasks and various other variables such as remaining buffer time, etc. There are a number of things that can cause the projectedDueDate to change. For example, an employee working on the project may (via a server request) enter in a shipping delay. Alternatively, a site may (via a server request) enter in an unexpected closure. When any of these things occur I need to not only update the projectedDueDate of the Task but also trigger the corresponding Project and Activity to update as well. What is the best way to do this? I've thought of the observer pattern but I don't keep a single copy of all these objects in memory. When a request comes in, I query the Task in from the database, at that point there is no associated Activity in memory that would be a listener. I could remove the ability to query for Tasks and force the application to query first by Project, then by Activity (in context of Project), then by task (in context of Activity) adding the observer relationships at each step but I'm not sure if that is the best way. I could setup a database event listening system so when a Task modified event is dispatched I have a handler which queries for the Activity at that point. I could simply setup a two-way relationship between Task and Activity so that the Task knows about the parent Activity and when the Task updates his state the Task grabs his parent and updates state. Right now I'm stuck considering all the options and am wondering if any single approach (doesn't have to be a listed approach) is jumping out at others as the best approach.

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• In C++ Good reasons for NOT using symmetrical memory management (i.e. new and delete)

  - by Jim G

  I try to learn C++ and programming in general. Currently I am studying open source with help of UML. Learning is my hobby and great one too. My understanding of memory allocation in C++ is that it should be symmetrical. A class is responsible for its resources. If memory is allocated using new it should be returned using delete in the same class. It is like in a library you, the class, are responsibility for the books you have borrowed and you return them then you are done. This, in my mind, makes sense. It makes memory management more manageable so to speak. So far so good. The problem is that this is not how it works in the real world. In Qt for instance, you create QtObjects with new and then hand over the ownership of the object to Qt. In other words you create QtObjects and Qt destroys them for you. Thus unsymmetrical memory management. Obviously the people behind Qt must have a good reason for doing this. It must be beneficial in some kind of way, My questions is: What is the problem with Bjarne Stroustrups idea about a symmetrical memory management contained within a class? What do you gain by splitting new and delete so you create an object and destroy it in different classes like you do in Qt. Is it common to split new and delete and why in such case, in other projects not involving Qt? Thanks for any help shedding light on this mystery!

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• Stopping immediate right button up in Mint 13 (Cinnamon) actioning first menu choice

  - by jontyc

  In Windows, a single right click (i.e., with release) displays a context menu on the screen, allowing you to select the appropriate choice with a further click from either button. In Mint 13, Cinnamon, it's hold down the right button, drag, then release on the appropriate menu choice. Both methods are fine, but constantly using both OSs regularly, I'm doing the Windows procedure in Mint by mistake all the time. This makes the single right click and release bring up the context menu and immediately action the first menu choice. Is there any mechanism to ignore right-button-up if a substantial dragging action or time period hasn't occurred, and have Mint looking for a further click to select?

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• Can most Intel processors run 64-bit Windows 7?

  - by Jian Lin

  Can most Intel processors run 64-bit Windows 7? Such as all the i7, i5, Core 2 Duo, Dual Core, Single Core with HT, and even just Single Core? I think a popular view is that if you can run 64-bit Windows 7, then use it? It might have driver compatibility issue but if there is no device hooked up, then there is no problem? What about some software / games not compatible with the 64-bit version or may run slower? thanks. update: a couple of my machines have 4GB RAM. so 64-bit Win 7 can make use of the full 4GB RAM instead of only about 3.2GB

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