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• Running Awk command on a cluster

  - by alex

  How do you execute a Unix shell command (awk script, a pipe etc) on a cluster in parallel (step 1) and collect the results back to a central node (step 2) Hadoop seems to be a huge overkill with its 600k LOC and its performance is terrible (takes minutes just to initialize the job) i don't need shared memory, or - something like MPI/openMP as i dont need to synchronize or share anything, don't need a distributed VM or anything as complex Google's SawZall seems to work only with Google proprietary MapReduce API some distributed shell packages i found failed to compile, but there must be a simple way to run a data-centric batch job on a cluster, something as close as possible to native OS, may be using unix RPC calls i liked rsync simplicity but it seem to update remote notes sequentially, and you cant use it for executing scripts as afar as i know switching to Plan 9 or some other network oriented OS looks like another overkill i'm looking for a simple, distributed way to run awk scripts or similar - as close as possible to data with a minimal initialization overhead, in a nothing-shared, nothing-synchronized fashion Thanks Alex

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• C# Process flow - Datastream, XML and datagrid

  - by Farstucker

  Im looking for some advice/suggestions on how I should setup the work flow of a small application Im building. When the application is launched the datagrid will be populated via the XML file. Once running the application will receive a datastream that I hope to update the file and datagrid. So Im curious what you would suggest on how I setup the workflow (ie, split the data from the data stream and simultaneously populate the file and grid or would you suggest populating the XML file first and setting up a timer to have the grid read the file?) Im really looking for optimal performance.

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• How to simulate different CPU frequency and limit RAM

  - by user351103

  Hi I have to build a simulator with C#. This simulator should be able to run a second thread with configureable CPU speed and limited RAM size, e.g. 144MHz and 50 MB. Of course I know that a simulator can never be as accurate as the real hardware. But I try to get almost similar performance. At the moment I'm thinking about creating a thread which I will stop/sleep from time to time. Depending on the desired CPU speed the simulator should adjust the sleep time of this thread and therefore simulate different cpu frequency. To measure the achieved speed I though about using PerformanceCounters. But with this approach I have the problem that I don't know how to limit the RAM size the thread could use. Do you have any ideas how to realize such a simulator? Thanks in advance!!

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• select only new row in oracle

  - by Hlex

  Hi, I have table with "varchar2" as primary key. Transaction is about 1 000 000 per day. my app wake up every 5 minute to generate text file by query only new record. It will remember last point and do only new record. 1)Do you have idea how query with good performance? I able to add new column if need. 2)what do you think this process should do by? plsql? java?

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• Faking a dynamic schema in Core Data?

  - by Gouldsc

  From reading the Apple Docs on Core Data, I've learned that you should not use Core Data when you need a dynamic schema. If I wanted to provide the user the ability to create their own properties, in a core data model would it work if I created some "dummy" attributes like "custom decimal 1", "custom decimal 2", "custom text 1", "custom text 2" etc that the user could name and use for their own purposes? Obviously this won't work for relationships, but for simple properties it seems like a reasonable workaround. Will creating a bunch of dummy attributes on my entities that go unused by most users noticeably decrease performance for them? Have any of you tried something like this? Thanks!

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• How to avoid the same calculations on column values over and over again in a select?

  - by Peter

  I sometimes write SELECTs on the form: SELECT a.col1+b.col2*c.col4 as calc_col1, a.col1+b.col2*c.col4 + xxx as calc_col1_PLUS_MORE FROM .... INNER JOIN ... ON a.col1+b.col2*c.col4 < d.some_threshold WHERE a.col1+b.col2*c.col4 > 0 When the calculations get rather involved and used up to 3-5 times within the same SELECT, I would really like to refactor that out in a function or similar in order to 1) hopefully improve performance / make use of cache 2) avoid forgetting to update one of the 4 calculations when I at a later stage realize I need to change the calculation. I usually have these selects within SPs. Any ideas?

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• FreeBSD or NetBSD based commercial TCP/IP stack vendor?

  - by Vineet

  Hi - Receiving recommendations for commercial TCP/IP stack implementation based on FreeBSD or NetBSD. Requirements are similar to a typical desktop PC running a browser, email and streaming voice/video. Which is to say a rich network functionality for a end-host type of device with mature implementation and reasonable performance. BSD derived network stacks are deployed in wide variety of situations for years and hence have mature implementation. It's supposed to run on a proprietary RTOS. Most vendors I found don't advertise if their stack is based on BSD. Any recommendations? -- Vineet

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• How do I prevent jagged edges alongside the surfaces of my 3d model?

  - by badcodenotreat

  Lets say I've implemented in openGL a crude model viewer with shading which renders a series of blocks, such that I have something that looks like this. http://i.imgur.com/TsF7K.jpg Whenever I rotate my model to the side, it causes an unwanted jagged effect along any surface with a steep viewing angle. http://i.imgur.com/Bgl9o.jpg I'm pretty sure this is due to the polygon offset I used to prevent z-fighting between the model and the wireframe, however I'm not able to find the factor/unit parameters in openGL which prevent this unwanted effect. what are the best values of factor and unit for glPolygonOffset to prevent this? would implementing anti-aliasing alleviate the problem? is the trade off in performance trivial/significant? is this perhaps a shading issue? should i try a solution along this line of thought?

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• How can I combine sequential expression trees into a fast method?

  - by chillitom

  Suppose I have the following expressions: Expression<Action<T, StringBuilder>> expr1 = (t, sb) => sb.Append(t.Name); Expression<Action<T, StringBuilder>> expr2 = (t, sb) => sb.Append(", "); Expression<Action<T, StringBuilder>> expr3 = (t, sb) => sb.Append(t.Description); I'd like to be able to compile these into a method/delegate equivalent to the following: void Method(T t, StringBuilder sb) { sb.Append(t.Name); sb.Append(", "); sb.Append(t.Description); } What is the best way to approach this? I'd like it to perform well, ideally with performance equivalent to the above method.

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• Google Analytics API - Tying Behavior to Specific Dates

  - by DavidS

  I am using the API to understand the performance of Adwords ad campaigns. I need to know how to attribute metrics back to the date dimension. For instance, for a given date, if I have 20 clicks, 18 visits, and 3 goal completions, does it mean that: 1) All of these actions happened on the day in question and are otherwise independent (meaning that the 3 goals could have been for people that clicked any time in the past 30 days, not who clicked on that day) 2) The on-site actions are a subset of the click activity on that day (i.e. on that day, 20 people clicked, 18 registered a real visit, and 3 completed a goal) If it is scenario 2, does that mean there is a need to refresh old rows every day? Thanks!

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• mod_php / mod_suphp / FastCGI | Which do you recommend and why.

  - by Saif Bechan

  I am at the point that I have to choose on what type of setup my application should run. I know there are some types available where apache runs smooth on, but they all have there downsides. System: Apache 2 / PHP 5.2 I hope you can give me some tips from firsthand experience. To give you an example of what to be covered. - Performance - Ease of setup - Security I know this does not really involve programming, but I have seen post concerning this and I know that you guys/girls here are certainly qualified to comment on this subject.

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• How to modularize a b2b webservice transformation application

  - by hstoerr

  How would you modularize a large application that has some incoming (SOAP) webservices, some outgoing webservices, transformations between them and internal formats, internal logging services, accesses external archiving webservices, delays stuff and works on this asynchronously and so forth? One way is to split the functionality into a collection of WAR, deploy all of them on one application server and have them communicate with internal webservices. This has some overhead, especially if the messages are large, and you might run into performance problems due to thread count restrictions and so forth. Another way would be to put everything into a giant WAR, such that you can communicate directly. Not exactly modularization. What would you do?

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• mySQL and general database normalization question

  - by Sinan

  I have question about normalization. Suppose I have an applications dealing with songs. First I thought about doing like this: Songs Table: id | song_title | album_id | publisher_id | artist_id Albums Table: id | album_title | etc... Publishers Table: id | publisher_name | etc... Artists Tale: id | artist_name | etc... Then as I think about normalization stuff. I thought I should get rid of "album_id, publisher_id, and artist_id in songs table and put them in intermediate tables like this. Table song_album: song_id, album_id Table song_publisher song_id, publisher_id Table song_artist song_id, artist_id Now I can't decide which is the better way. I'm not an expert on database design so If someone would point out the right direction. It would awesome. Are there any performance issues between two approaches? Thanks

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• NSThread vs. NSOperationQueue vs. ??? on the iPhone

  - by kubi

  Currently I'm using NSThread to cache images in another thread. [NSThread detachNewThreadSelector:@selector(cacheImage:) toTarget:self withObject:image]; Alternatively: [self performSelectorInBackground:@selector(cacheImage:) withObject:image]; Alternatively, I can use an NSOperationQueue NSInvocationOperation *invOperation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(cacheImage:) object:image]; NSOperationQueue *opQueue = [[NSOperationQueue alloc] init]; [opQueue addOperation:invOperation]; Is there any reason to switch away from NSThread? GCD is a 4th option when it's released for the iPhone, but unless there's a significant performance gain, I'd rather stick with methods that work in most platforms.

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• WCF - Network Cost

  - by Mubashar Ahmad

  Dear Devs I have a wcf service deployed on IIS with basicHttpBinding and aspNetCompatibilityEnabled=true I have a test client as well which invokes multiple service functions simultaneously. To check the performance of service call on client and server I calculated the Avg time it takes to complete a service request on client(in proxy code) and on server as well. after a test of 8 hrs (server and client were on the same machine) i came to know that average response time on client is around 34ms where as the Avg execution time on server is around 3ms so the difference is 31ms. I would like to know why every call is taking 31ms is it justified? and how can i reduce this?

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• SQL - query inside NOT IN takes longer than the complete query ??

  - by Aleksandar Tomic

  Hi every1, I'm using NOT IN inside my SQL query. For example: select columnA from table1 where columnA not in ( select columnB from table2) How is it possible that this part of the query select columnB from table2 takes 30sec to complete, but the whole query above takes 0.1sec to complete?? Shouldn't the complete query take 30sec + ? BTW, both queries return valid results. Thanks! Answers to Comments Is it because the second query hasn't actually completed but has only returned back the first 'x' rows (out of a very large table?) No, the query is completed after 30 seconds, not to many rows returned (eg. 50). But @Aleksandar wondered why the question congaing the performance killer was so fast. my point exactly Also how long does select distinct columnB from table2 take to execute? actually, the original query is "select distinct...

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• Should I use `!IsGood` or `IsGood == false`?

  - by chills42

  I keep seeing code that does checks like this if (IsGood == false) { DoSomething(); } or this if (IsGood == true) { DoSomething(); } I hate this syntax, and always use the following syntax. if (IsGood) { DoSomething(); } or if (!IsGood) { DoSomething(); } Is there any reason to use '== true' or '== false'? Is it a readability thing? Do people just not understand Boolean variables? Also, is there any performance difference between the two?

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• Cost of using repeated parameters

  - by Palimondo

  I consider refactoring few method signatures that currently take parameter of type List or Set of concrete classes --List[Foo]-- to use repeated parameters instead: Foo*. This would allow me to use the same method name and overload it based on the parameter type. This was not possible using List or Set, because List[Foo] and List[Bar] have same type after erasure: List[Object]. In my case the refactored methods work fine with scala.Seq[Foo] that results from the repeated parameter. I would have to change all the invocations and add a sequence argument type annotation to all collection parameters: baz.doStuffWith(foos:_*). Given that switching from collection parameter to repeated parameter is semantically equivalent, does this change have some performance impact that I should be aware of? Is the answer same for scala 2.7._ and 2.8?

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• The speed of .NET in numerical computing

  - by Yin Zhu

  In my experience, .net is 2 to 3 times slower than native code. (I implemented L-BFGS for multivariate optimization). I have traced the ads on stackoverflow to http://www.centerspace.net/products/ the speed is really amazing, the speed is close to native code. How can they do that? They said that: Q. Is NMath "pure" .NET? A. The answer depends somewhat on your definition of "pure .NET". NMath is written in C#, plus a small Managed C++ layer. For better performance of basic linear algebra operations, however, NMath does rely on the native Intel Math Kernel Library (included with NMath). But there are no COM components, no DLLs--just .NET assemblies. Also, all memory allocated in the Managed C++ layer and used by native code is allocated from the managed heap. Can someone explain more to me? Thanks!

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• Subsonic SQLite Multiple Files

  - by Marcus Vinicius de LIma

  Hi, I have an application that must be accessed for many users. To optimize the performance I intend to store each user profile information at a independant database file. I need everytime a user login the application, to setup a new provider linked with his own database. All databases have the same structure. So while querying user the commom generated DAL classes must switch for the database file relative the the user. Is there a way for configure SubSonic for doing that switch at runtime? Thanks.

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• jQuery/Javascript framework efficiency

  - by Russell

  My latest project is using a javascript framework (jQuery), along with some plugins (validation, jquery-ui, datepicker, facebox, ...) to help make a modern web application. I am now finding pages loading slower than I am used to. After some js profiling (thanks VS2010!), it seems a lot of the time is taken procesing inside the framework. Now I understand the more complex the ui tools, the more processing needs to be done. The project is not yet at a large stage and I think would be average functions. At this stage I can see it is not going to scale well. I noticed things like the 'each' command in jQuery takes quite a lot of processing time. Have others experienced some extra latency using JS frameworks? How do I minimise their effect on page performance? Are there best practices on implementation using JS frameworks? Thanks

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• Strip tags (with tags inside attributes and nested tags) using javascript

  - by Kokizzu

  What the fastest (in performance) way to strip strings from tags, most solution i've tried that uses regexp not resulting correct values for tags inside attributes (yes, i know it's wrong), example test case: var str = "<div data-content='yo! press this: <br/> <button type=\"button\"><i class=\"glyphicon glyphicon-disk\"></i> Save</button>' data-title='<div>this one for tooltips <div>seriously</div></div>'> this is the real content<div> with another nested</div></div>" that should resulting: this is the real content with another nested

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• Compilier optimization of repeated accessor calls C#

  - by apocalypse9

  I've found recently that for some types of financial calculations that the following pattern is much easier to follow and test especially in situations where we may need to get numbers from various stages of the computation. public class nonsensical_calculator { ... double _rate; int _term; int _days; double monthlyRate { get { return _rate / 12; }} public double days { get { return (1 - i); }} double ar { get { return (1+ days) /(monthlyRate * days) double bleh { get { return Math.Pow(ar - days, _term) public double raar { get { return bleh * ar/2 * ar / days; }} .... } Obviously this often results in multiple calls to the same accessor within a given formula. I was curious as to whether or not the compiler is smart enough to optimize away these repeated calls with no intervening change in state, or whether this style is causing a decent performance hit. Further reading suggestions are always appreciated

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• How to Obtain Data to Pre-Populate Forms.

  - by Stan

  The objective is to have a form reflect user's defined constraints on a search. At first, I relied entirely upon server-side scripting to achieve this; recently I tried to shift the functionality to JavaScript. On the server side, the search parameters are stored in a ColdFusion struct which makes it particularly convenient to have the data JSON'ed and sent to the client. Then it's just a matter of separately iterating over 'checkable' and text fields to reflect the user's search parameters; jQuery proved to be exceptionally effective in simplifying the workload. One observable difference lies in performance. The second method appeared to be somewhat slower and didn't work in IE8. Evidently, the returned JSON'ed struct was seen as an empty object. I'm sure it can be fixed, though before spending any more time with it, I'm curious to hear how others would approach the task. I'd gladly appreciate any suggestions. --Stan

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• Do you know a good and efficient FFT?

  - by yan bellavance

  Hi, I am trying to find a very fast and efficient Fourier transform (FFT). Does anyone know of any good ones. I need to run it on the iPhone so it must not be intensive. Instead, maybe you know of one that is wavelet like, i need frequency resolution but only a narrow band (vocal audio range up to 10khz max...even 10Khz might be too high). Im thinking also of truncating this FFT to keep the frequency resolution while eliminating the unwanted frequency band. This is for an iphone ...I have taken a look at the FFT in Aurio touch but it seems this is an int FFT but my app uses floats.....would it give a big performance increase to try and adapt program to an int FFT or not(which i really dont feel like doing...plus aurio touch uses a radix 2 FFT which is not that great).

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