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• Which NoSQL db to use with C?

  - by systemsfault

  Hello all, I'm working on an application that I'm going to write with C and i am considering to use a nosql db for storing timeseries data with at most 8 or 9 fields. But in every 5 minutes there will huge write operations such as 2-10 million rows and then there will be reads(but performance is not as crucial in read as in the write operation). I'm considering to use a NoSQL db here in order to store the data but couldn't decide on which one to use. Couchdb seems to have a stable driver called pillowtalk for C; but Mongo's driver doesn't look as promising as pillowtalk. I'm also open to other suggestions. What is your recommendation?

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• Optimal search queries

  - by Macros

  Following on from my last question http://stackoverflow.com/questions/2788082/sql-server-query-performance, and discovering that my method of allowing optional parameters in a search query is sub optimal, does anyone have guidelines on how to approach this? For example, say I have an application table, a customer table and a contact details table, and I want to create an SP which allows searching on some, none or all of surname, homephone, mobile and app ID, I may use something like the following: select * from application a inner join customer c on a.customerid = a.id left join contact hp on (c.id = hp.customerid and hp.contacttype = 'homephone') left join contact mob on (c.id = mob.customerid and mob.contacttype = 'mobile') where (a.ID = @ID or @ID is null) and (c.Surname = @Surname or @Surname is null) and (HP.phonenumber = @Homphone or @Homephone is null) and (MOB.phonenumber = @Mobile or @Mobile is null) The schema used above isn't real, and I wouldn't be using select * in a real world scenario, it is the construction of the where clause I am interested in. Is there a better approach, either dynamic sql or an alternative which can achieve the same result, without the need for many nested conditionals. Some SPs may have 10 - 15 criteria used in this way

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• InvalidCastException: System.Web.UI.PartialCachingControl -> MyCustomControl when OutputCaching

  - by marcinn

  The problem: I am unable to use OutputCaching with my controls which derives from MyCustomControl. Controls are loaded dynamically using definitions from database with Page.LoadControl method. When I add to ascx <%@ OutputCache VaryByParam="*" Duration="3600"% the "InvalidCastException: System.Web.UI.PartialCachingControl - MyCustomControl" exception is thrown. I am unable to modify assembly witch contains dynamic loading controls logic. Is there any way to fix it in derived controls? The second question is about iis7 and native output caching - is it resolves this problem? (I tried to set up several performance counters and I saw that cache wasn't hit...)

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• "Remember" last three MySql queries; Cookie, passed variable or other method?

  - by Camran

  I have a classified website, with pretty sophisticated searching, and I am about to implement a function where the last three queries is displayed for the user, so that the user can go back easier through the queries. This because for each query the user has to provide a lot of input. I have four questions for you: I wonder, how can I save the actual query (SELECT * FROM etc etc)...? Do I need to add some form of encryption to be on the safe side? How will this affect performance? (I don't like the fact that cookies slow websites down) Anything else to think about? If you need more input, let me know... Btw, the website is PHP based. Thanks

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• Facing problem in configuring Reporting Server

  - by idrees99

  Hi all, I am using Sql server 2005 express edition and i want to Install and configure Reporting server on my local machine.Now i have installed the reporting server but the issue is that i am unable to configure it properly.when ever i go to start the reporting services it gives me the following message: THE SQL SERVER REPORTING SERVICE(SQLEXPRESS)service on Local computer started and then stopped. Some services stop automatically if they have no work to do, for example, the performance Logs and Alerts service. I am using WindowsXp Professional. plz help me out as i have just started using sql server and i dont have any idea.

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• How can I update a column in a table with the result of a select statement that uses row being updat

  - by Sailing Judo

  This SQL statement example is very close to what I think I need... update table1 set value1 = x.value1 from (select value1, code from table2 where code = something) as x However, what I need to do is change the "something" in the above example to a value from the row that is being updated. For example, I tried this but it didn't work: update table1 A set value1 = x.value1 from (select value1, code from table2 where code = A.something) as x This is a one time operation to update an existing table and I'm not really looking for high performance way to do this. Any solution that gets the task done is good enough.

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• What scenarios/settings will result in a query on SQL Server (2008) return stale data

  - by s1mm0t

  Most applications rarely need to display 100% accurate data. For example if this stack overflow question displays that there have been 0 views, when there have really been 10, it doesn't really matter. This is one way that the (perceived) performance of applications can be improved, by caching results and therefore sometimes not showing 100% accurate results. There are some cases where the data does need to be 100% accurate though. So if I run the query select * from Foo I want to be sure that the results are not stale. Now depending on how my database is set up, other activity on the database, use of transactions and isolation levels etc this query may or may not be a true reflection of the world. What scenario's and settings can people think of that will result in this query returning stale results or given that another connection is part way through a transaction that has updated this table, how can I guarantee that when the above query returns, the results will be accurate.

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• java virtual machine - how does it allocate resources?

  - by Will

  I am testing the performance of a data streaming system that supports continuous queries. This is how it works: - There is a polling service which sends data to my system. - As data passes into the system, each query evaluates based on a window of the stream at the current time. - The window slides as data passes in. My problem is this, when I add more queries to the system, I should expect the throughput to decrease because it can't cope the data rate. However, I actually observe an increase in throughput. I can't understand why this is the case and I am guessing that it's something to do with the way the JVM allocates CPU, memory etc. Can anyone shed any light to my problem?

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• How do you use the C language to produce a ruby gem?

  - by DJTripleThreat

  I would like to see some source code or maybe a link to some that gives at least a stub for writing ruby gems in the C languages (C++?? is that possible too?) Also, some of you may know that Facebook compiles some of their code natively as php extensions for better performance. Is anyone doing this in Rails? If so, what has been your experience with it? Have you found it to be useful? Thanks. Edit: I guess I'll answer my own question with some stuff I learned today but I'm going to leave the question open for another answer because I'd like to see what others have to say on this topic

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• PHP, better to set the variable before if or use if/else?

  - by DssTrainer

  So a simple one that I just never could find a straight answer on. What is better (performance or otherwise): $var = false; If ($a == $b) { $var = true; } or If ($a == $b) { $var = true; } else { $var = false; } I've heard arguments for both ways. I find the first cleaner to ensure I have it set, and a little less code too. The pro being that you may only need to set it once without conditional. But the con being that if the argument is true, it gets set twice. I am assuming the second way is probably best practice

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• Will Haskell be a good choice for my task?

  - by Narzanka

  I'm starting a new project and don't know which language to use. My 'must have' requirements are: Be able to run on Windows/LinuxMacOs natively (native executable) - user should be able to just run the exe (when on Windows for example) and see the results. No runtimes/interpreters (no jvm, clr, etc) - one file download should be enough to run the application. Full unicode support. Be able to manipulate OS threads (create them, run multiple tasks in parallel on multi-core CPUs, etc). Be reasonably fast (Python level performance and better). To have some kind of standard library that does low-level, mundane tasks. Not very niche and have some community behind it to be able to ask questions. My 'nice to have' requirements are: Language should be functional It should have good string manipulation capabilities (not necessarily regex) Not extremely hard to learn I'm thinking about Haskell now but keeping in mind OCaml as well. Please advice if my choice is correct.

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• What machine learning algorithms can be used in this scenario?

  - by ExceptionHandler

  My data consists of objects as follows. Obj1 - Color - shape - size - price - ranking So I want to be able to predict what combination of color/shape/size/price is a good combination to get high ranking. Or even a combination could work like for eg: in order to get good ranking, the alg predicts best performance for this color and this shape. Something like that. What are the advisable algorithms for such a prediction? Also may be if you can briefly explain how I can approach towards the model building I would really appreciate it. Say for eg: my data looks like Blue pentagon small $50.00 #5 Red Squre large $30.00 #3 So what is a useful prediction model that I should look at? What algorithm should I try to predict like say highest weightage is for price followed by color and then size. What if I wanted to predict in combinations like a Red small shape is less likely to higher rank compared to pink small shape . (In essence trying to combine more than one nominal values column to make the prediction)

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• "Volkswagen Passat" Navigation

  - by joe_midi

  http://web.vw.com/all-new-passat-experience/ The navigation on this .swf is very impressive, and I was wondering how I would go about replicating it. The way each of the sections Design / Technology / Safety / Performance I want to know how each section can expand and still fit together. I've started with MOUSE_OVER events, but I'm not entirely sure how to order them so each section is the right size for every mouse over Event. This is the code I have for each "Section", I have created a movie clip with a Mask that expands on mouse over and brings the selected clip to the highest depth. this.firstButton01.addEventListener(MouseEvent.MOUSE_OVER, firstButton01OVER) function firstButton01OVER(e:Event):void { this.firstButton01.gotoAndPlay(2); this.setChildIndex(firstButton01,this.numChildren-1); }

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• Fastest way to convert a binary file to SQLite database

  - by chown

  I've some binary files and I'm looking for a way to convert each of those files to a SQLite database. I've already tried C# but the performance is too slow. I'm seeking an advice on how and what programming language should be the best to perform this kind of conversion. Though I prefer any Object Oriented Language more (like C#, Java etc), I'm open for any programming language that boosts up the conversion. I don't need a GUI frontend for the conversion, running the script/program from console is okay. Thanks in advance

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• Simulators for thread scheduling on multicore

  - by shijie xu

  I am seeking a simulator for thread scheduling at multi-core architecture, that is mapping threads to the cores at runtime. During runtime, simulator collects overall cache and IPC statistics. I checked below simulators, but seems there are not sufficient for me: Simplescalar: A simulator only for single core. SESC: multiprocessor simulator with detailed power, thermal, and performance models, QSim: provides instruction-level control of the emulated environment and detailed information about the executing instruction stream. It seems both SESC and QSim supports instructions scheduling instead of thread scheduling on the cores? Anyone can help provide some clues or share experience for this part?

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• Choosing an alternative ( visual basic) high level programming language

  - by user370244

  I used to be visual basic 6 programmer, i was pleased with visual basic : it is high level language that do stuff fast,easy to learn, easy to do stuff in,you can drag and drop stuff to the form and write your code,it is simply amazing.however microsoft buried VB6 and pointed us to VB.NET which is so different that it is not the old VB anymore.I didn't like what microsoft did and would like to look somewhere AWAY from microsoft and from any other proprietary language . I would like to look into a similar language that is easy,cross platform (windows / Linux), object oriented, visual design, non proprietary and compile (for some guarding against reverse engineering). i am freelancer so the choice is entirely mine,i don't care about performance of programs, the time taken to develop a given programs is much more important. desktop / database / GUI /networking programming is what i am looking for. so any such language offered by our open source community ? thank you so much

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• Eclipse debug - line: not available

  - by Mike

  I can't seem to find anything on google telling me why this might be and what the resolution is. I'm Stepping through third party code (that I have the source for) and would really like to see the current line being executed... Looking at javac compile flags, I see the -g:none flag. If this flag is set, would this be enough to explain why I'm not able to see line numbers? If so, why would someone do this, are there performance implications? Do I need to recompile the jar myself to attach the missing debug info (if possible)? Thanks!

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• CouchDB: How to change view function via javascript?

  - by osti

  Hello Guys, I am playing around with CouchDB to test if it is "possible" [1] to store scientific data (simulated and experimental raw data + metadata). A big pro is the schema-less approach of CouchDB: we have to be very flexible with the metadata, as the set of parameters changes very often. Up to now I have some code to feed raw data, plots (both as attachments), and hierarchical metadata (as JSON) into CouchDB documents, and have written some prototype Javascript for filtering and showing. But the filtering is done on the client side (a.k.a. browser): The map function simply returns everything. How could I change the (or push a second) map function of a specific _design-document with simple browser-JS? I do not think that a temporary view would yield any performance gain... Thanks for your time and answers. [1]: of course it is possible, but is it also useful? feasible? reasonable?

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• How does a cmdlet know when it really should call WriteVerbose()?

  - by Roman Kuzmin

  How does a cmdlet know when it really should call WriteVerbose(), WriteDebug() and etc.? Perhaps I miss something simple but I cannot find the answer. All cmdlet implementations I have seen so far just call WriteVerbose() without any hesitation. I know that it is correct to do so, but it is not effective. Performance suffers when verbose mode is off but a cmdlet still prepares data for WriteVerbose() call, that is, for nothing. In other words, in a cmdlet I would like to be able to: if (<VerboseMode>) { .... data preparation, sometimes expensive ... WriteVerbose(...); } But I don't know how to get this if (<VerboseMode>). Any ideas?

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• What language should I use to parse a lot of text?

  - by BicMan

  My company's proprietary software generates a log file that is much easier to use if it is parsed. The log parser we all use was written by another employee as a side project, and it has horrible performance. These log files can grow to 10s of megabytes very quickly, and the parser we currently use has issues if a log file is bigger than 1 megabyte. So, I want to write a program that can parse this massive amount of text in the shortest amount of time possible. We use Windows exclusively, so running on Windows is a must. Our current implementation runs on a local web server, and I'm convinced that running it as an application would have to be faster. All suggestions will be helpful. Thanks.

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• C# Why does calling an interface member from a class generate an error?

  - by Jack

  So I have an interface: interface IFoo { int Bar(); int this[int i] {get; set;} } And a class that derives from it class Foo : IFoo { public int IFoo.Bar() { //Implementation { public int IFoo.this[int i] { //Implementation } } Now, I try to do this: var fooey = new Foo(); int i = Fooey.Bar(); or this: int i = Fooey[4]; I would expect these to work properly. However, the compiler generates an error as if such members don't exist. Why is that? I am aware I can cast Foo as IFoo, but I am also aware that casting is costly to performance, which is often the reason to use interfaces in the first place. EDIT 1: These are the errors generated 'Foo' does not contain a definition for 'Bar' and no extension method 'Bar' accepting a first argument of type 'Foo' could be found (are you missing a using directive or an assembly reference?) "Cannot apply indexing to an expression of type 'Foo'"

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• Language D compared to C++?

  - by Henrik

  Anyone here with experience of the language D? I was just reading through its presentation at http://www.d-programming-language.org/ and at Wikipedia and it seems like a good (better) alternative to C++. With good/better I mean that it seem simpler yet it has all the good stuff within C/C++. But without some of the difficulties that make C++ more difficult to learn and use in a good and efficient way. So anyone with comments/experience with the language D? Performance?

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• Any efficient way to read datas from large binary file?

  - by limi

  Hi, I need to handle tens of Gigabytes data in one binary file. Each record in the data file is variable length. So the file is like: <len1><data1><len2><data2>..........<lenN><dataN> The data contains integer, pointer, double value and so on. I found python can not even handle this situation. There is no problem if I read the whole file in memory. It's fast. But it seems the struct package is not good at performance. It almost stuck on unpack the bytes. Any help is appreciated. Thanks.

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• I want to make a wrapped acces type for certain internals of one of classes and I have some performa

  - by Alex

  I am writing an abstract matrix class (and some concrete subclasses) for use on very differing hardwares/architectures, etc. and I want to write a row and column type that provides a transparent reference to the rows and columns of the matrix. However, I want to tune for performance, so I'd like this class to be essentially a compiler construct. In other words, I'm willing to sacrifice some dev time to making the overhead of these classes as small as possible. I assume all (small) methods would want to be virtual? Keep the structure small? Any other suggestions?

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• Excel Interop: Fastest way to change color of portions of text in a huge range of cells

  - by Kyopaxa

  There some articles about the fastest way to write data using Excel interop assigning directly an Array of data to the value of the range. Like: string[,] multidimensionalArrayData = new string[200, 3]; // (...) Fill multidimensionalArrayData with your data dataSheet.Range["A1:C200"].Value = multidimensionalArrayData; There are also some articles about how to change the Font color of a specific portion of text, for example (VB this time): With ActiveCell.Characters(Start:=3, Length:=3).Font .Name = "Arial" .FontStyle = "Regular" .Size = 10 .Color = "Red" .ThemeFont = xlThemeFontNone End With The question now is, what would be the fastest way to change the color of specific portions of text for thousands of cells? Currently, in my C# code, I have to do it cell by cell, with a horrible performance hit. Is there a way to fill an array of 'Characters' objects in C# and pass that array to a range in one go? Any other solutions?

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