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• Using a C#.net DLL in Node.js / serverside javascript

  - by Dve

  I have spent a while playing with node.js and exploring related frameworks such as express and geddy... and I am very impressed, especially with the WebSockets implementation in socket.io. I have a pet project that is an online game, the entire game engine is written in C# and I would like to know if there is anyway I can call the functions of this existing dll from a solution built using node.js, socket.io, express etc? The game engine itself is pretty complete; tested and robust. I am hoping there is some neat way of exposing its functionality without to much overhead. Thanks

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• Killing a deadlocked Task in .NET 4 TPL

  - by Dan Bryant

  I'd like to start using the Task Parallel Library, as this is the recommended framework going forward for performing asynchronous operations. One thing I haven't been able to find is any means of forcible Abort, such as what Thread.Abort provides. My particular concern is that I schedule tasks running code that I don't wish to completely trust. In particular, I can't be sure this untrusted code won't deadlock and therefore I can't be certain if a Task I schedule using this code will ever complete. I want to stay away from true AppDomain isolation (due to the overhead and complexity of marshaling), but I also don't want to leave a Task thread hanging around, deadlocked. Is there a way to do this in TPL?

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• Java - When to use Iterators?

  - by Walter White

  Hi all, I am trying to better understand when I should and should not use Iterators. To me, whenever I have a potentially large amount of data to iterate through, I write an Iterator for it. If it also lends itself to the Iterator interface, then it seems like a win. I was reading a little bit that there is a lot of overhead with using an Iterator. A good example of where I used an Iterator was to iterate through a bunch of SQL scripts to execute one query at a time, reading it in, then executing it. Is there another performance trade off I should be aware of? Before I used iterators, I would read the entire String of SQL commands to execute into an ArrayList, and the iterate through that. If the import is rather large (like for geolocation data, then the server tends to get bogged down). Walter

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• Need advice on speeding up tableViewCell photo loading performance

  - by ambertch

  I have around 20 tableview cells that each contain a number (2-5) thumbnail sized pictures (they are VERY small Facebook profile pictures, ex. http://profile.ak.fbcdn.net/hprofile-ak-sf2p/hs254.snc3/23133_201668_2989_q.jpg). Each picture is an UIImageView added to the cell's contentview. Scrolling performance is poor, and measuring the draw time I've found the UIImage rendering is the bottleneck. I've researched/thought of some solutions but as I am new to iphone development I am not sure which strategy to pursue: preload all the images and retrieve them from disk instead of URL when drawing cells (I'm not sure if cell drawing will still be slow, so I want to hold off on the time investment here) Have the cells display a placeholder image from disk, while the picture is asynchronously loaded (this seems to be the best solution, but I'm currently not sure exactly how to do best do this) There's the fast drawing recommendation from Tweetie, but I don't know that will have much affect if it turns out my overhead is in network loading (http://blog.atebits.com/2008/12/fast-scrolling-in-tweetie-with-uitableview/) Thoughts/implementation advice? Thanks!

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• Using Protocol Buffers in J2EE?

  - by mlaverd

  Hello everyone, I have coded a server that uses Protocol Buffers in Java. A client talks to it using PB. I'd like to migrate the server code to J2EE and take advantage of the containers' built-in features like clustering. How can I have a service that receives PB messages and interprets them properly, and then gets them handled? I was thinking of a dedicated type of servlet, but how can it be done? I'm a J2EE newbie... I'm not familiar enough with J2EE application servers to know if there is a way to make that happen. P.S. I'm looking for a solution that uses TLS sockets directly. No overhead-causing middleman protocols like HTTP are welcome here. P.P.S. Open source solutions only please.

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• SIMPLE Bug Tracking Suggestions?

  - by mauriciopastrana

  Any suggestions for good, solid, bug tracking solutions that let me (and company members) document bugs in 1-or-2-click steps? Basically I grew tired of all the overhead Mantis brings in... All I need is a list (do away with assign/status/priority/notes, phew! we're a small company!). I'm tempted to write it up in CakePHP, but before I do so, i'd love to know if there's something out there. Points if its free or web2-"ish". Cheers, Thx. /mp

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• calculating the potential effect of inaccurate triangle vertex positions on the triangle edge lenght

  - by stingrey

  i'm not sure how to solve the following problem: i have a triangle with each of the three known vertex positions A,B,C being inaccurate, meaning they can each deviate up to certain known radii rA, rB, rC into arbitrary directions. given such a triangle, i want to calculate how much the difference of two specific edge lengths (for instance the difference between lengths of edge a and edge b) of the triangle may change in the worst case. is there any elegant mathematical solution to this problem? the naive way i thought of is calculating all 360^3 angle combinations and measuring the edge differences for each case, which is a rather high overhead.

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• Enumerate shared folders on Windows with low privileges

  - by Phil Nash

  Using C++ (VS2008) I need to be able to enumerate all shared folders on the current machine and get or construct the local and remote names. We've been using NetShareEnum for this fairly successfully, but have hit a problem where we need to run with a user account with low privileges. To get the local path using NetShareEnum we need to retrieve at least SHARE_INFO_2 structures - but that requires "Administrator, Power User, Print Operator, or Server Operator group membership". I've been trying to use WNetOpenEnum and WNetEnumResource instead but I don't seem to be getting the local name back for that for shares either - and I can't seem to get it to enumerate just local resources - it goes off and finds all shared resources on the local network - which is not an acceptable overhead. So I'd either like help on where I'm going wrong with WNetEnumResource, or a suggestion as to another way of doing this. Any suggestions are much appreciated.

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• Why is thread local storage so slow?

  - by dsimcha

  I'm working on a custom mark-release style memory allocator for the D programming language that works by allocating from thread-local regions. It seems that the thread local storage bottleneck is causing a huge (~50%) slowdown in allocating memory from these regions compared to an otherwise identical single threaded version of the code, even after designing my code to have only one TLS lookup per allocation/deallocation. This is based on allocating/freeing memory a large number of times in a loop, and I'm trying to figure out if it's an artifact of my benchmarking method. My understanding is that thread local storage should basically just involve accessing something through an extra layer of indirection, similar to accessing a variable via a pointer. Is this incorrect? How much overhead does thread-local storage typically have? Note: Although I mention D, I'm also interested in general answers that aren't specific to D, since D's implementation of thread-local storage will likely improve if it is slower than the best implementations.

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• ETW tracking from .net, user mode and driver

  - by Jack Juiceson

  Hi everyone, We have an application that parts of it are in .net, c++ usermode and C++ drivers. The application is divided into several executables that run on demand and communication with each other using LPC(the processes run in different sessions(winlogon)). Currently We have a home written logging service to which .net and c++ usermode communicate by sending LPC messages. The driver uses DbgPrint and is not always enabled, as it causes the code to run 30% slower(we have lots of logging). I want to have all the logs written in one place and preferably not writing the logger myself(I love log4cpp and log4net). The requirement is to write from all the executables and drivers into one place and to have minimal overhead. I have read that ETW is way to go, however I wasn't able to find already written logger that uses it like log4cpp or log4net. So basically my questions is, do you know if there is already implemented ETW appender for log4cpp and log4net I can use ?

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• Android and Protocol Buffers

  - by spaceboy2000

  I am writing an Android application that would both store data and communicate with a server using protocol buffers. However, the stock implementation of protocol buffers compiled with the LITE flag (in both the JAR library and the generated .java files) has an overhead of ~30 KB, where the program itself is only ~30 KB. In other words, protocol buffers doubled the program size. Searching online, I found a reference to an Android specific implementation. Unfortunately, there seems to be no documentation for it, and the code generated from the standard .proto file is incompatible with it. Has anyone used it? How do I generate code from a .proto file for this implementation? Are there any other lightweight alternatives?

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• Hadoop: Iterative MapReduce Performance

  - by S.N

  Is it correct to say that the parallel computation with iterative MapReduce can be justified only when the training data size is too large for the non-parallel computation for the same logic? I am aware that the there is overhead for starting MapReduce jobs. This can be critical for overall execution time when a large number of iterations is required. I can imagine that the sequential computation is faster than the parallel computation with iterative MapReduce as long as the memory allows to hold a data set in many cases. Is it the only benefit to use the iterative MapReduce? If not, what are the other benefits could be?

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• C Programming: malloc and free within a loop

  - by kouei

  Hi all, I just started out with C and have very little knowledge about performance issues with malloc() and free(). My question is as such: if I were to call malloc() followed by free() in a while-loop that loops for, say, 20 times, would it run slower compared to if I were to call free() outside the loop? I am actually using the first method to allocate memory to a buffer, read a string of variable length in a file, perform some string operation, and then clear the buffer after every iteration. If my method results in a lot of overhead then I'd like to ask for a better way for me to achieve the same results. Sorry for my bad English. Thanks and regards, K

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• Where does the ObjectDataSource cache data?

  - by Jeremy

  I'm considering using an ObjectDataSource as an intermediate between my page controls and my data access layer & object model. Traditionally I have manually created the object and populate it via a series of findcontrol statements when I need to insert/update data in the database. I'm hoping that I can use the ObjectDataSource to marshal data between my object and my controls, eliminating that manual code, as long as the ObjectDataSource doesn't come with a lot of overhead. I noticed the EnableCaching property, where does the caching occure? is it in view state?

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• Is it professional to have funny looking logging messages

  - by JCH

  Hi, Recently I have joined a new project team where in the java application logs have logged messages in a non-formal way[can't think of suitable word]. here how they look :-) <message> for info messages :-| <message> for warn :-( <message> for error besides there's also ASCII art drawing , different one for each log when that particular service starts up or is killed .And there many more styles for certain application events. iam not sure if it has any significant overhead on the application or not. I would like to ask you folks if you come across such unique styles of logging messages or do you also practice any styles.what is your opinion about it. BR /jon

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• Postgresql - one database for everyone, or one-database per customer

  - by user337876

  I'm working on a web-based business application where each customer will need to have their own data (think basecamphq.com type model) For scalability and ease-of-upgrades, I'd prefer to have a single database where each customer gets a filtered version of the data. The problem is how to guarantee that they stay sandboxed to their own data. Trying to enforce it in code seems like a disaster waiting to happen. I know Oracle has a way to append a where clause to every query based on a login id, but does Postgresql have anything similar? If not, is there a different design pattern I could use (like creating a view of each table for each customer that filters)? Worse case scenario, what is the performance/memory overhead of having 1000 100M databases vs having a single 1Tb database? I will need to provide backup/restore functionality on a per-customer basis which is dead-simple on a single database but quite a bit trickier if they are sharing the database with other customers.

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• Best Database Change Control Methodologies

  - by SnapJag

  As a database architect, developer, and consultant, there are many questions that can be answered. One, though I was asked recently and still can't answer good, is... "What is one of, or some of, the best methods or techniques to keep database changes documented, organized, and yet able to roll out effectively either in a single-developer or multi-developer environment." This may involve stored procedures and other object scripts, but especially schemas - from documentation, to the new physical update scripts, to rollout, and then full-circle. There are applications to make this happen, but require schema hooks and overhead. I would rather like to know about techniques used without a lot of extra third-party involvement.

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• Zend Framework: How to include an OR statement in an SQL fetchAll()

  - by Scoobler

  I am trying to build the following SQL statement: SELECT users_table.*, users_data.first_name, users_data.last_name FROM users_table INNER JOIN users_data ON users_table.id = user_id WHERE (users_table.username LIKE '%sc%') OR (users_data.first_name LIKE '%sc%') OR (users_data.last_name LIKE '%sc%') I have the following code at the moment: public function findAllUsersLike($like) { $select = $this-select(Zend_Db_Table::SELECT_WITH_FROM_PART)-setIntegrityCheck(false); $select-where('users_table.username LIKE ?', '%'.$like.'%'); $select-where('users_data.first_name LIKE ?', '%'.$like.'%'); $select-where('users_data.last_name LIKE ?', '%'.$like.'%'); $select-join('users_data', 'users_table.id = user_id', array('first_name', 'last_name')); return $this-fetchAll($select); } This is close, but not right as it uses AND to add the extra WHERE statements, instead of OR. Is there any way to do this as one select? Or should I perform 3 selects and combine the results (alot more overhead?)? P.S. The parameter $like that is past is sanitized so don't need to wory about user input in the code above!

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• Scipy sparse... arrays?

  - by spitzanator

  Hey, folks. So, I'm doing some Kmeans classification using numpy arrays that are quite sparse-- lots and lots of zeroes. I figured that I'd use scipy's 'sparse' package to reduce the storage overhead, but I'm a little confused about how to create arrays, not matrices. I've gone through this tutorial on how to create sparse matrices: http://www.scipy.org/SciPy_Tutorial#head-c60163f2fd2bab79edd94be43682414f18b90df7 To mimic an array, I just create a 1xN matrix, but as you may guess, Asp.dot(Bsp) doesn't quite work because you can't multiply two 1xN matrices. I'd have to transpose each array to Nx1, and that's pretty lame, since I'd be doing it for every dot-product calculation. Next up, I tried to create an NxN matrix where column 1 == row 1 (such that you can multiply two matrices and just take the top-left corner as the dot product), but that turned out to be really inefficient. I'd love to use scipy's sparse package as a magic replacement for numpy's array(), but as yet, I'm not really sure what to do. Any advice? Thank you very much!

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• What the performance impact of enabling WebSphere PMI

  - by Andrew Whitehouse

  I am currently looking at some JProfiler traces from our WebSphere-based application, and am noticing that a significant amount of CPU time is being spent in the class com.ibm.io.async.AsyncLibrary.getCompletionData2. I am guessing, but I am wondering whether this is PMI-related (and we do have this enabled). My knowledge of PMI is limited, as this is managed by another team. Is it expected that PMI can have this sort of impact? (If so) Is the only option to turn it off completely? Or are there some types of data capture that have a particularly high overhead?

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• Instantiating a context in LINQ to Entities

  - by Jagd

  I've seen two different manners that programmers approach when creating an entity context in their code. The first is like such, and you can find it all over the MSDN code examples: public void DoSomething() { using TaxableEducationEntities context = new TaxableEducationEntities()) { // business logic and whatever else } } The second is to create the context as a private attribute in some class that encapsulates your business logic. So you would have something like: public class Education_LINQ { private TaxableEducationEntities context = new TaxableEducationEntities(); public void DoSomething() { var result = from a in context.luAction select a; // business logic and whatever else } } Which way is more efficient? Assume that you have two methods, one called DoSomething1() and another called DoSomething2(), and both methods incorporate the using statement to open the context and do whatever with it. Were you to call one method after the other, would there be any superfluous overhead going on, since essentially both methods create the context and then clean it up when they're done? As opposed to having just one private attribute that is created when a class object is instantiated, and then in turn cleaned up when the object goes out of scope?

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• Delphi-5 single-file storage solution?

  - by pastacool

  Hi! Is there a Delphi-5 solution to easily integrate single-file storage into existing code? I would like to have files like Java *.jar or Openoffice document files which are zipped/compressed files and folders but with their own file extension. Edit: I know some ZIP capable components but in a nutshell I want to access files within the "container" and use normal file handling routines on them (eg. TStringList.SaveToFile). Any overhead about compress/uncompress should be handled by the component.

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• How do I make "simple" throughput servlet-filter?

  - by Tommy

  I'm looking to create a filter that can give me two things: number of request pr minute, and average responsetime pr minute. I already got the individual readings, I'm just not sure how to add them up. My filter captures every request, and it records the time each request takes: public void doFilter(ServletRequest request, ...() { long start = System.currentTimeMillis(); chain.doFilter(request, response); long stop = System.currentTimeMillis(); String time = Util.getTimeDifferenceInSec(start, stop); } This information will be used to create some pretty Google Chart charts. I don't want to store the data in any database. Just a way to get current numbers out when requested As this is a high volume application; low overhead is essential. I'm assuming my applicationserver doesn't provide this information.

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• Dynamically creating controls in MFC (Collection question)

  - by ProgramWriter

  Hello all, I have some custom control inside of which i should create radiobuttons or checkboxes. The count of child controls is available only at runtime (it loads some file from which it gets this count). So i need to create variable number of controls. Which collection i should use for this purpose? Solution 1: simply use std::vector (or CArray) - not suitable because i want use MFC (CButton). Of course i can Attach() and later Detach() handle to window each time i need this window, but it will give big overhead. Solution 2: use std::vector or CArray or CList or... In this case i take care about making 'new' and appropriate 'delete' when control is unneeded. I am forgetful :) MFC handle map contains pointer to CButton and i can't use simple CArray, because it will move my objects each time when his size will grow. ... and the question is: Which collection i should use for containing variable count of MFC control classes?

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• What is the underlying reason for not being able to put arrays of pointers in unsafe structs in C#?

  - by cons

  If one could put an array of pointers to child structs inside unsafe structs in C# like one could in C, constructing complex data structures without the overhead of having one object per node would be a lot easier and less of a time sink, as well as syntactically cleaner and much more readable. Is there a deep architectural reason why fixed arrays inside unsafe structs are only allowed to be composed of "value types" and not pointers? I assume only having explicitly named pointers inside structs must be a deliberate decision to weaken the language, but I can't find any documentation about why this is so, or the reasoning for not allowing pointer arrays inside structs, since I would assume the garbage collector shouldn't care what is going on in structs marked as unsafe. Digital Mars' D handles structs and pointers elegantly in comparison, and I'm missing not being able to rapidly develop succinct data structures; by making references abstract in C# a lot of power seems to have been removed from the language, even though pointers are still there at least in a marketing sense. Maybe I'm wrong to expect languages to become more powerful at representing complex data structures efficiently over time.

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