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  • Are filesystem operations a function of the kernel?

    - by hydroparadise
    I suppose the question would be OS specific, so I'll take the following scenarios: Winodows (NTFS) OSX (HFS) Linux (ext2,ext3,ext4) Each operating system has it's default filesystem it operates os (OSX, I beleive, only has the one choice available). I've noticed some utilities out there for OS's to read different file systems (which obvisouly is NOT apart of the kernel), which got me thinking: Are filesystem operations a function of a driver (ie, potentially modular), or is it truly apart of the kernel?

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  • What's the convention for extending Linq with set based helper operations

    - by Luke Rohde
    Hi All I might be vaguing out here but I'm looking for a nice place to put set based helper operations in linq so I can do things like; db.Selections.ClearTemporary() which does something like db.DeleteAllOnSubmit(db.Selections.Where(s => s.Temporary)) Since I can figure out how to extend Table<Selection> the best I can do is create a static method in partial class of Selection (similar to Ruby) but I have to pass in the datacontext like; Selection.ClearTemporary(MyDataContext) This kind of sucks because I have two conventions for doing set based operations and I have to pass the data context to the static class. I've seen other people recommending piling helper methods into a partial of the datacontext like; myDataContext.ClearTemporarySelections(); But I feel this makes the dc a dumping ground for in-cohesive operations. Surely I'm missing something. I hope so. What's the convention? TIA

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  • What's the convention for extending Linq datacontext with set based helper operations specific to on

    - by Luke Rohde
    Hi All I might be vaguing out here but I'm looking for a nice place to put set based helper operations in linq so I can do things like; db.Selections.ClearTemporary() which does something like db.DeleteAllOnSubmit(db.Selections.Where(s => s.Temporary)) Since I can figure out how to extend Table<Selection> the best I can do is create a static method in partial class of Selection (similar to Ruby) but I have to pass in the datacontext like; Selection.ClearTemporary(MyDataContext) This kind of sucks because I have two conventions for doing set based operations and I have to pass the data context to the static class. I've seen other people recommending piling helper methods into a partial of the datacontext like; myDataContext.ClearTemporarySelections(); But I feel this makes the dc a dumping ground for in-cohesive operations. Surely I'm missing something. I hope so. What's the convention? TIA

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  • Library for polygon operations

    - by AJM
    I've recently encountered a need for a library or set of libraries to handle operations on 2D polygons. I need to be able to perform boolean/clipping operations (difference and union) and triangulation. So far the libraries I've found are poly2tri, CGAL, and GPC. Poly2tri looks good for triangulation but I'm still left with boolean operations, and I'm unsure about its maturity. CGAL and GPC are only free if my own project is free. My particular project isn't commercial, so I'm hesitant to pay or request for any licenses. But I may want to use my code for a future commercial project, so I'm hesitant about CGAL's open source licenses and GPC's freeware-only restriction. There doesn't seem to be any polygon clipping libraries with nice BSD-style licenses.

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  • T-SQL Operations on a Calculated Date Field

    - by firedrawndagger
    Can I do WHERE operations on a calculated date field? I have a lookup field, which has been written badly in SQL and unfortunately I can't change it. But basically it stores dates as characters such as "July-2010" or "June-2009" (along with other non date data). I want to extract the dates first (which I did using a LIKE opertor) and then extract data based on a date range. SELECT BusinessUnit, Lookup, ReleaseDate FROM ( SELECT TOP 10 LookupColumn As Lookup, BU as BusinessUnit, CONVERT(DATETIME, REPLACE(LookupColumn,'-',' ')) as ReleaseDate FROM [dbo].[LookupTable] WHERE LookupColumn LIKE N'%-2010' ) MyTable ORDER BY ReleaseDate WHERE ReleaseDate = '2010-02-01' I'm having issues with WHERE operator. I would assume creating a subquery to encapsulate the calculated field would allow me to do operations with it such as WHERE but maybe I'm wrong. Bottom line is it possible to do operations on calculated fields?

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  • Recommend a Software for documenting work/research

    - by Rogue
    Need a software for documenting my work & research. I was considering to use blog engine but then I don't want to be playing around with backing up the databases and the matter separately. The specifications for the software would be: 1) To catalogue work by categories, tags and date. 2) Easy editing and drawing features 3) Easily incorporate saved html files into matter I'm writing, with the formatting and pictures. (probably use the mht format, don't want to be wasting timeformatting html pages) Would like the html pages to be directly displayed in the software and not opened on demand Software should be for Windows. Any recommendations? 4) Language tools could be an addition but only an optional feature

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  • Performance of file operations on thousands of files on NTFS vs HFS, ext3, others

    - by peterjmag
    [Crossposted from my Ask HN post. Feel free to close it if the question's too broad for superuser.] This is something I've been curious about for years, but I've never found any good discussions on the topic. Of course, my Google-fu might just be failing me... I often deal with projects involving thousands of relatively small files. This means that I'm frequently performing operations on all of those files or a large subset of them—copying the project folder elsewhere, deleting a bunch of temporary files, etc. Of all the machines I've worked on over the years, I've noticed that NTFS handles these tasks consistently slower than HFS on a Mac or ext3/ext4 on a Linux box. However, as far as I can tell, the raw throughput isn't actually slower on NTFS (at least not significantly), but the delay between each individual file is just a tiny bit longer. That little delay really adds up for thousands of files. (Side note: From what I've read, this is one of the reasons git is such a pain on Windows, since it relies so heavily on the file system for its object database.) Granted, my evidence is merely anecdotal—I don't currently have any real performance numbers, but it's something that I'd love to test further (perhaps with a Mac dual-booting into Windows). Still, my geekiness insists that someone out there already has. Can anyone explain this, or perhaps point me in the right direction to research it further myself?

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  • Ubuntu in VirtualBox File Modified Time in Future and PHP slow file operations

    - by user1750
    For some reason, some of my files have a last modified date in the future. In addition to this, file operations in PHP are SUPER slow. For example, rebuilding the Symfony2 cache can take over 40 seconds (its takes 1-2 on my MacBook Pro). Notice the time for ListingsCRUDController.php. It just says "2012". In order see the date more clearly I ran ls --time-style="full-iso" -l For some reason it shows that this file's last modified date is ~5 hours into the future. System time: To make things more confusing, the system will intermittently speed up. Suddenly, my app will start serving requests in 1-2 seconds (down from 40 seconds) for no apparent reason. I mean I don't do anything to my code/system config - it just changes. Also, during a slow PHP request, the php5-fpm process (nginx) uses 100% of the CPU for the duration of the request. This is the second VM this has happened on and I need to know why its doing this. It has become unusable. Information About My Setup VirtualBox 4.2.0 Host: Macbook Pro Guest: Ubuntu Server 12.04 Package dkms is installed Timezones match for Ubuntu and PHP. Things I've Tried Both Apache and Nginx. APC enabled and disabled. Xdebug enabled and disabled. 1 processor up to 4 processors. 1gb memory up to 4gb memory. I've installed Ubuntu using the regular kernel and the VM kernel.

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  • Disk operations in windows 7 are slow

    - by Skadlig
    My computer started lagging last Sunday. I tried to reboot it and it failed. Trying to boot into failsafe mode takes around two hours. It mainly freezes on two files: scsiport.sys and classpnp.sys When it finally has started all disc operations are really slow. When it has run for a while it goes faster, probably due to data moved into RAM instead. It froze on an other file before that was associated with Avast but uninstalling it didn't really help. A critical windows update was installed on Sunday but rolling back the update didn't help. I had a guess about the sound card but disabling the sound card drivers also didn’t help. I have an inkling of an idea that it might be Intel rapid storage technology that might be acting up but it doesn't allow me to reinstall it from failsafe mode and I haven't been able to log into normal mode for a while. I would appreciate suggestions regarding how to get into normal mode again and/or what can be the root cause.

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  • Is NFS capable of preserving order of operations?

    - by JustJeff
    I have a diskless host 'A', that has a directory NFS mounted on server 'B'. A process on A writes to two files F1 and F2 in that directory, and a process on B monitors these files for changes. Assume that B polls for changes faster than A is expected to make them. Process A seeks the head of the files, writes data, and flushes. Process B seeks the head of the files and does reads. Are there any guarantees about how the order of the changes performed by A will be detected at B? Specifically, if A alternately writes to one file, and then the other, is it reasonable to expect that B will notice alternating changes to F1 and F2? Or could B conceivably detect a series of changes on F1 and then a series on F2? I know there are a lot of assumptions embedded in the question. For instance, I am virtually certain that, even operating on just one file, if A performs 100 operations on the file, B may see a smaller number of changes that give the same result, due to NFS caching some of the actions on A before they are communicated to B. And of course there would be issues with concurrent file access even if NFS weren't involved and both the reading and the writing process were running on the same real file system. The reason I'm even putting the question up here is that it seems like most of the time, the setup described above does detect the changes at B in the same order they are made at A, but that occasionally some events come through in transposed order. So, is it worth trying to make this work? Is there some way to tune NFS to make it work, perhaps cache settings or something? Or is fine-grained behavior like this just too much expect from NFS?

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  • Windows Server 2008 R2 grinds to a screeching halt during file copy operations

    - by skolima
    When my Windows Server 2008 R2 machine is performing any large disk operations (copying 10GB files from one drive to another, copying similar file over network, merging HyperV snapshots, compressing large files), performance of the whole machine slows down terribly, everything becomes unresponsive. This is noticeable in any situation when the disk access is large enough not to fit in the cache. Are there any settings available for tuning this behaviour? I can accept slower file transfer if this would give me more responsiveness. System details: Dell Optiflex 960, Core 2 Quad Q9650, 8GB RAM, 2 SATA drives - 320GB (ST3320418AS) and 1TB (ST31000528AS), NCQ active on both, Intel 82564LM-3 Gigabit Ethernet, ATI HD 3450 graphics, Intel ICH10 bridge. We have multiple machines like this, every one is exhibiting the same behaviour. I though this was overkill for a workstation, apparently I was mistaken. Update: I guess I shouldn't have mentioned the HyperV at all. The above configuration is a standard workstation setup at the company I work for, this is not a server of any kind. I have at most 3 virtual machines working, and usually I'm the only person accessing them. Never the less, the slowdown occurs even when no VMs are running. On a Linux machine I'd simply ionice the copy process and I could forget about it, is there any way to manage IO priorities on Windows?

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  • Sort algorithm with fewest number of operations

    - by luvieere
    What is the sort algorithm with fewest number of operations? I need to implement it in HLSL as part of a pixel shader effect v2.0 for WPF, so it needs to have a really small number of operations, considering Pixel Shader's limitations. I need to sort 9 values, specifically the current pixel and its neighbors.

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  • C++ vs Matlab vs Python as a main language for Computer Vision Research

    - by Hough
    Hi all, Firstly, sorry for a somewhat long question but I think that many people are in the same situation as me and hopefully they can also gain some benefit from this. I'll be starting my PhD very soon which involves the fields of computer vision, pattern recognition and machine learning. Currently, I'm using opencv (2.1) C++ interface and I especially like its powerful Mat class and the overloaded operations available for matrix and image operations and seamless transformations. I've also tried (and implemented many small vision projects) using opencv python interface (new bindings; opencv 2.1) and I really enjoy python's ability to integrate opencv, numpy, scipy and matplotlib. But recently, I went back to opencv C++ interface because I felt that the official python new bindings were not stable enough and no overloaded operations are available for matrices and images, not to mention the lack of machine learning modules and slow speeds in certain operations. I've also used Matlab extensively in the past and although I've used mex files and other means to speed up the program, I just felt that Matlab's performance was inadequate for real-time vision tasks, be it for fast prototyping or not. When the project becomes larger and larger, many tasks have to be re-written in C and compiled into Mex files increasingly and Matlab becomes nothing more than a glue language. Here comes the sub-questions: For carrying out research in these fields (machine learning, vision, pattern recognition), what is your main or ideal programming language for rapid prototyping of ideas and testing algorithms contained in papers? For computer vision research work, can you list down the pros and cons of using the following languages? C++ (with opencv + gsl + svmlib + other libraries) vs Matlab (with all its toolboxes) vs python (with the imcomplete opencv bindings + numpy + scipy + matplotlib). Are there computer vision PhD/postgrad students here who are using only C++ (with all its availabe libraries including opencv) without even needing to resort to Matlab or python? In other words, given the current existing computer vision or machine learning libraries, is C++ alone sufficient for fast prototyping of ideas? If you're currently using Java or C# for your research, can you list down the reasons why they should be used and how they compare to other languages in terms of available libraries? What is the de facto vision/machine learning programming language and its associated libraries used in your research group? Thanks in advance. Edit: As suggested, I've opened the question to both academic and non-academic computer vision/machine learning/pattern recognition researchers and groups.

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  • Operations on Python hashes

    - by cdecker
    I've got a rather strange problem. For a Distributed Hash Table I need to be able to do some simple math operations on MD5 hashes. These include a sum (numeric sum represented by the hash) and a modulo operation. Now I'm wondering what the best way to implement these operations is. I'm using hashlib to calculate the hashes, but since the hashes I get are then string, how do I calculate with them?

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  • An extended Bezier Library or Algorithms of bezier operations

    - by Sorush Rabiee
    Hi, Is there a library of data structures and operations for quadratic bezier curves? I need to implement: bezier to bitmap converting with arbitrary quality optimizing bezier curves common operations like subtraction, extraction, rendering etc. languages: c,c++,.net,python Algorithms without implementation (pseudocode or etc) could be useful too. (especially optimization)

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  • Productivity research material

    - by Rune FS
    While debating which platform to use for what applications (specifically we debated c++, java, c# and f#) we tried finding scientific quality research on productivity (cost of ownership really) of similar applications build on various platforms/using the above mentioned languages. Any one know of such research?

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  • Data retrieval and Join operations with cluster db server

    - by Goerge
    If any database spreads across multiple servers (ex. Microsoft Sql Server), how can we do join or filter operations. In my scenario, if suppose: A single table spreads across multiple servers how can we filter rows based on user input? If master table is there on one db server and transaction table is at another db server, how can we do join operations? Please let me know how can we achieve this and where can I get more details about this?

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  • Circular shift operations in C++

    - by Elroy
    Left and right shift operators (<< and ) are already available in C++. However, I couldn't find out how I could perform circular shift or rotate operations. How can operations like "Rotate Left" and "Rotate Right" be performed? Rotating right twice here Initial --> 1000 0011 0100 0010 should result in: Final --> 1010 0000 1101 0000 An example would be helpful.

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  • File Operations in Java

    - by Amir Rachum
    I'm working on a small application in Java that takes a directory structure and renames the files according to a certain format, after parsing the original name. What is the best Java class / methodology to use in order to facilitate these file operations? Edit: the question is only regarding the file operations part, I got the "getting the formatted name" down :)

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  • Manual drag-drop operations in Flex

    - by Yarin
    This is a two-part problem: A) I'm implementing several irregular drag-drop operations in Flex (e.g. DataGrid ItemRenderer into Tree). My preference was modifying DragManager operations to meet my needs, and in fact using DragManager allows me to do everything I need, but I'm having serious issues with performance. For example, dragging anything over a many-columned DataGrid, whether the drag was initiated with DragManager.doDrag, or just using native ListBase drag-drop functionality, slows the drag movement to a crawl. Even if the DataGrid is disabled/ not listenening for any move/drag events, this happens. On the other hand, if the drag is initiated by calling .startDrag() on the Sprite, the drag is smooth and performs great over DataGrids and everything else. So part A would be: Is there a reason why .startDrag() operations work so well, while drags initiated through DragManager.doDrag suffer so badly when over certain components? B) If indeed the solution is to handle drag-drops using .startDrag(), how would I go about determining what component the mouse is over when the drag is released? In my example, my dragged object is brought up to the top level of the display list, and so is being moved around in stage coordinates. mouseMove, mouseOver events don't fire on the components I'm dragging over because the mouse is constantly over the dragged component, so I would need some sort of stage.coordinate - visibleComponentAtThatCoordinate conversion. Any thoughts on this? Thanks alot!-- Yarin

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  • Large number of simultaneous long-running operations in Qt

    - by Hostile Fork
    I have some long-running operations that number in the hundreds. At the moment they are each on their own thread. My main goal in using threads is not to speed these operations up. The more important thing in this case is that they appear to run simultaneously. I'm aware of cooperative multitasking and fibers. However, I'm trying to avoid anything that would require touching the code in the operations, e.g. peppering them with things like yieldToScheduler(). I also don't want to prescribe that these routines be stylized to be coded to emit queues of bite-sized task items...I want to treat them as black boxes. For the moment I can live with these downsides: Maximum # of threads tend to be O(1000) Cost per thread is O(1MB) To address the bad cache performance due to context-switches, I did have the idea of a timer which would juggle the priorities such that only idealThreadCount() threads were ever at Normal priority, with all the rest set to Idle. This would let me widen the timeslices, which would mean fewer context switches and still be okay for my purposes. Question #1: Is that a good idea at all? One certain downside is it won't work on Linux (docs say no QThread::setPriority() there). Question #2: Any other ideas or approaches? Is QtConcurrent thinking about this scenario? (Some related reading: how-many-threads-does-it-take-to-make-them-a-bad-choice, many-threads-or-as-few-threads-as-possible, maximum-number-of-threads-per-process-in-linux)

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  • Suggestions of the easiest algorithms for some Graph operations

    - by Nazgulled
    Hi, The deadline for this project is closing in very quickly and I don't have much time to deal with what it's left. So, instead of looking for the best (and probably more complicated/time consuming) algorithms, I'm looking for the easiest algorithms to implement a few operations on a Graph structure. The operations I'll need to do is as follows: List all users in the graph network given a distance X List all users in the graph network given a distance X and the type of relation Calculate the shortest path between 2 users on the graph network given a type of relation Calculate the maximum distance between 2 users on the graph network Calculate the most distant connected users on the graph network A few notes about my Graph implementation: The edge node has 2 properties, one is of type char and another int. They represent the type of relation and weight, respectively. The Graph is implemented with linked lists, for both the vertices and edges. I mean, each vertex points to the next one and each vertex also points to the head of a different linked list, the edges for that specific vertex. What I know about what I need to do: I don't know if this is the easiest as I said above, but for the shortest path between 2 users, I believe the Dijkstra algorithm is what people seem to recommend pretty often so I think I'm going with that. I've been searching and searching and I'm finding it hard to implement this algorithm, does anyone know of any tutorial or something easy to understand so I can implement this algorithm myself? If possible, with C source code examples, it would help a lot. I see many examples with math notations but that just confuses me even more. Do you think it would help if I "converted" the graph to an adjacency matrix to represent the links weight and relation type? Would it be easier to perform the algorithm on that instead of the linked lists? I could easily implement a function to do that conversion when needed. I'm saying this because I got the feeling it would be easier after reading a couple of pages about the subject, but I could be wrong. I don't have any ideas about the other 4 operations, suggestions?

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  • WCF Windows Service - Long operations/Callback to calling module

    - by A9S6
    I have a Windows Service that takes the name of a bunch of files and do operations on them (zip/unzip, updating db etc). The operations can take time depending on size and number of files sent to the service. (1) The module that is sending a request to this service waits until the files are processed. I want to know if there is a way to provide a callback in the service that will notify the calling module when it is finished processing the files. Please note that multiple modules can call the service at a time to process files so the service will need to provide some kind of a TaskId I guess. (2) If a service method is called and is running and another call is made to the same service, then how will that call be processed(I think there is only one thread asociated with the service). I have seen that when the service is taking time in processing a method, the threads associated with the service begin to increase.

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