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• GAE modeling relationship options

  - by Sway

  Hi there, I need to model the following situation and I can't seem to find a consistent example on how to do it "correctly" for the google app engine. Suppose I've got a simple situation like the following: [Company] 1 ----- M [Stare] A company has one to many stores. Each store has an address made up of a address line 1, city, state, country, postcode etc. Ok. Lets say we need to create say an "Audit". An Audit is for a company and can be across one to many stares. So something like: [Audit] 1 ------ 1 [Company] 1 ------ M [Store] Now we need to query all of the "audits" based on the Store "addresses" in order to send the "Auditors" to the right locations. There seem to be numerous articles like this one: http://code.google.com/appengine/articles/modeling.html Which give examples of creating a "ContactCompany" model class. However they also say that you should use this kind of relationship only when you "really need to" and with "care" for performance. I've also read - frequently - that you should denormalize as much as possible thereby moving all of the "query-able" data into the Audit class. So what would you suggest as the best way to solve this? I've seen that there is an Expando class but I'm not sure if that is the "best" option for this. Any help or thoughts on this would be totally appreciated. Thanks in advance, Matt

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• SQL Server - Multi-Column substring matching

  - by hamlin11

  One of my clients is hooked on multi-column substring matching. I understand that Contains and FreeText search for words (and at least in the case of Contains, word prefixes). However, based upon my understanding of this MSDN book, neither of these nor their variants are capable of searching substrings. I have used LIKE rather extensively (Select * from A where A.B Like '%substr%') Sample table A: ID | Col1 | Col2 | Col3 | ------------------------------------- 1 | oklahoma | colorado | Utah | 2 | arkansas | colorado | oklahoma | 3 | florida | michigan | florida | ------------------------------------- The following code will give us row 1 and row 2: select * from A where Col1 like '%klah%' or Col2 like '%klah%' or Col3 like '%klah%' This is rather ugly, probably slow, and I just don't like it very much. Probably because the implementations that I'm dealing with have 10+ columns that need searched. The following may be a slight improvement as code readability goes, but as far as performance, we're still in the same ball park. select * from A where (Col1 + ' ' + Col2 + ' ' + Col3) like '%klah%' I have thought about simply adding insert, update, and delete triggers that simply add the concatenated version of the above columns into a separate table that shadows this table. Sample Shadow_Table: ID | searchtext | --------------------------------- 1 | oklahoma colorado Utah | 2 | arkansas colorado oklahoma | 3 | florida michigan florida | --------------------------------- This would allow us to perform the following query to search for '%klah%' select * from Shadow_Table where searchtext like '%klah%' I really don't like having to remember that this shadow table exists and that I'm supposed to use it when I am performing multi-column substring matching, but it probably yields pretty quick reads at the expense of write and storage space. My gut feeling tells me there there is an existing solution built into SQL Server 2008. However, I don't seem to be able to find anything other than research papers on the subject. Any help would be appreciated.

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• When does it makes sense to use a map?

  - by kiwicptn

  I am trying to round up cases when it makes sense to use a map (set of key-value entries). So far I have five categories (see below). Assuming more exist, what are they? Please limit each answer to one unique category, put up an example, and vote up the fascinating ones. Property values (like a bean) age -> 30 sex -> male loc -> calgary Histograms peter -> 1 john -> 7 paul -> 5 Presence, with O(1) performance peter -> 1 john -> 1 paul -> 1 Functions peter -> treatPeter() john -> dealWithJohn() paul -> managePaul() Conversion peter -> pierre john -> jean paul -> paul

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• SQL Server Search Proper Names Full Text Index vs LIKE + SOUNDEX

  - by Matthew Talbert

  I have a database of names of people that has (currently) 35 million rows. I need to know what is the best method for quickly searching these names. The current system (not designed by me), simply has the first and last name columns indexed and uses "LIKE" queries with the additional option of using SOUNDEX (though I'm not sure this is actually used much). Performance has always been a problem with this system, and so currently the searches are limited to 200 results (which still takes too long to run). So, I have a few questions: Does full text index work well for proper names? If so, what is the best way to query proper names? (CONTAINS, FREETEXT, etc) Is there some other system (like Lucene.net) that would be better? Just for reference, I'm using Fluent NHibernate for data access, so methods that work will with that will be preferred. I'm using SQL Server 2008 currently. EDIT I want to add that I'm very interested in solutions that will deal with things like commonly misspelled names, eg 'smythe', 'smith', as well as first names, eg 'tomas', 'thomas'. Query Plan |--Parallelism(Gather Streams) |--Nested Loops(Inner Join, OUTER REFERENCES:([testdb].[dbo].[Test].[Id], [Expr1004]) OPTIMIZED WITH UNORDERED PREFETCH) |--Hash Match(Inner Join, HASH:([testdb].[dbo].[Test].[Id])=([testdb].[dbo].[Test].[Id])) | |--Bitmap(HASH:([testdb].[dbo].[Test].[Id]), DEFINE:([Bitmap1003])) | | |--Parallelism(Repartition Streams, Hash Partitioning, PARTITION COLUMNS:([testdb].[dbo].[Test].[Id])) | | |--Index Seek(OBJECT:([testdb].[dbo].[Test].[IX_Test_LastName]), SEEK:([testdb].[dbo].[Test].[LastName] >= 'WHITDþ' AND [testdb].[dbo].[Test].[LastName] < 'WHITF'), WHERE:([testdb].[dbo].[Test].[LastName] like 'WHITE%') ORDERED FORWARD) | |--Parallelism(Repartition Streams, Hash Partitioning, PARTITION COLUMNS:([testdb].[dbo].[Test].[Id])) | |--Index Seek(OBJECT:([testdb].[dbo].[Test].[IX_Test_FirstName]), SEEK:([testdb].[dbo].[Test].[FirstName] >= 'THOMARþ' AND [testdb].[dbo].[Test].[FirstName] < 'THOMAT'), WHERE:([testdb].[dbo].[Test].[FirstName] like 'THOMAS%' AND PROBE([Bitmap1003],[testdb].[dbo].[Test].[Id],N'[IN ROW]')) ORDERED FORWARD) |--Clustered Index Seek(OBJECT:([testdb].[dbo].[Test].[PK__TEST__3214EC073B95D2F1]), SEEK:([testdb].[dbo].[Test].[Id]=[testdb].[dbo].[Test].[Id]) LOOKUP ORDERED FORWARD) SQL for above: SELECT * FROM testdb.dbo.Test WHERE LastName LIKE 'WHITE%' AND FirstName LIKE 'THOMAS%' Based on advice from Mitch, I created an index like this: CREATE INDEX IX_Test_Name_DOB ON Test (LastName ASC, FirstName ASC, BirthDate ASC) INCLUDE (and here I list the other columns) My searches are now incredibly fast for my typical search (last, first, and birth date).

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• Maintain denormalized data with NHibernate EventListener

  - by Michael Valenty

  I have one bit of denormalized data used for performance reasons and I'm trying to maintain the data with an NHibernate event listener rather than a trigger. I'm not convinced this is the best approach, but I'm neck deep into it and I want to figure this out before moving on. I'm getting following error: System.InvalidOperationException : Collection was modified; enumeration operation may not execute. System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource) System.Collections.Generic.List`1.Enumerator.MoveNextRare() System.Collections.Generic.List`1.Enumerator.MoveNext() NHibernate.Engine.ActionQueue.ExecuteActions(IList list) NHibernate.Engine.ActionQueue.ExecuteActions() NHibernate.Event.Default.AbstractFlushingEventListener.PerformExecutions (IEventSource session) NHibernate.Event.Default.DefaultFlushEventListener.OnFlush(FlushEvent event) NHibernate.Impl.SessionImpl.Flush() NHibernate.Transaction.AdoTransaction.Commit() Here's the code to make happen: using (var tx = session.BeginTransaction()) { var business = session .Get<Business>(1234) .ChangeZipCodeTo("92011"); session.Update(business); tx.Commit(); // error happens here } and the event listener: public void OnPostUpdate(PostUpdateEvent @event) { var business = @event.Entity as Business; if (business != null) { var links = @event.Session .CreateQuery("select l from BusinessCategoryLink as l where l.Business.BusinessId = :businessId") .SetParameter("businessId", business.BusinessId) .List<BusinessCategoryLink>(); foreach (var link in links) { link.Location = business.Location; @event.Session.Update(link); } } }

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• semi dynamic cdn

  - by dwi kristianto

  i'm developing couple of websites using php (directory script, etc.) and wordpress as cms. i need to improve its performance, by using cdn for static files (css, js, images). the problem is, css and javascript files are generated on the fly. i did that due to yahoo and some expert advice to combine the files into one file. also changing basic color of css files. for the time being, i use couple of small vps but still its not fast enough. i already contact maxcdn and the support guy said that they dont have such kind of services. what i need is: a cdn that will serve the request from user/visitor and there's no file in local disk, the cdn will redirect/fetch it from another domain/server. in vps, it could be done easily using combination of .htaccess and php, but NOT in the cdn. most of cdn only support purely static files. is there any such cdn that will server semi-dynamic files?

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• Out of Core Implementation of a Quadtree

  - by Nima

  Hi, I am trying to build a Quadtree data structure(or let's just say a tree) on the secondary memory(Hard Disk). I have a C++ program to do so and I use fopen to create the files. Also, I am using tesseral coding to store each cell in a file named with its corresponding code to store it on the disk in one directory. The problem is that after creating about 1,100 files, fopen just returns NULL and stops creating new files. I can create further files manually in that directory, but using C++ it can not create any further files. I know about max limit of inode on ext3 filesystem which is (from Wikipedia) 32,000 but mine is way less than that, also note that I can create files manually on the disk; just not through fopen. Also, I really appreciate any idea regarding the best way to store a very dynamic quadtree on disk(I need the nodes to be in separate files and the quadtree might have a depth of 50). Using nested directories is one idea, but I think it will slow down the performance because of following the links on the filesystem to access the file. Thanks, Nima

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• Sorting GridView Formed With Data Set

  - by nani

  Following Code is for Sorting GridView Formed With DataSet Source: http://www.highoncoding.com/Articles/176_Sorting_GridView_Manually_.aspx But it is not displaying any output. There is no problem in sql connection. I am unable to trace the error, please help me. Thank You. public partial class _Default : System.Web.UI.Page { private const string ASCENDING = " ASC"; private const string DESCENDING = " DESC"; private DataSet GetData() { SqlConnection cnn = new SqlConnection("Server=localhost;Database=Northwind;Trusted_Connection=True;"); SqlDataAdapter da = new SqlDataAdapter("SELECT TOP 5 firstname,lastname,hiredate FROM EMPLOYEES", cnn); DataSet ds = new DataSet(); da.Fill(ds); return ds; } public SortDirection GridViewSortDirection { get { if (ViewState["sortDirection"] == null) ViewState["sortDirection"] = SortDirection.Ascending; return (SortDirection)ViewState["sortDirection"]; } set { ViewState["sortDirection"] = value; } } protected void GridView1_Sorting(object sender, GridViewSortEventArgs e) { string sortExpression = e.SortExpression; if (GridViewSortDirection == SortDirection.Ascending) { GridViewSortDirection = SortDirection.Descending; SortGridView(sortExpression, DESCENDING); } else { GridViewSortDirection = SortDirection.Ascending; SortGridView(sortExpression, ASCENDING); } } private void SortGridView(string sortExpression, string direction) { // You can cache the DataTable for improving performance DataTable dt = GetData().Tables[0]; DataView dv = new DataView(dt); dv.Sort = sortExpression + direction; GridView1.DataSource = dv; GridView1.DataBind(); } } aspx page asp:GridView ID="GridView1" runat="server" AllowSorting="True" OnSorting="GridView1_Sorting" /asp:GridView

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• Is there added overhead to looking up a column in a DataTable by name rather than by index?

  - by Ben McCormack

  In a DataTable object, is there added overhead to looking up a column value by name thisRow("ColumnA") rather than by the column index thisRow(0)? In which scenarios might this be an issue. I work on a team that has lots of experience writing VB6 code and I noticed that didn't do column lookups by name for DataTable objects or data grids. Even in .NET code, we use a set of integer constants to reference column names in these types of objects. I asked our team lead why this was so, and he mentioned that in VB6, there was a lot of overhead in looking up data by column name rather than by index. Is this still true for .NET? Example code (in VB.NET, but same applies to C#): Public Sub TestADOData() Dim dt As New DataTable 'Set up the columns in the DataTable ' dt.Columns.Add(New DataColumn("ID", GetType(Integer))) dt.Columns.Add(New DataColumn("Name", GetType(String))) dt.Columns.Add(New DataColumn("Description", GetType(String))) 'Add some data to the data table ' dt.Rows.Add(1, "Fred", "Pitcher") dt.Rows.Add(3, "Hank", "Center Field") 'Method 1: By Column Name ' For Each r As DataRow In dt.Rows Console.WriteLine( _ "{0,-2} {1,-10} {2,-30}", r("ID"), r("Name"), r("Description")) Next Console.WriteLine() 'Method 2: By Column Name ' For Each r As DataRow In dt.Rows Console.WriteLine("{0,-2} {1,-10} {2,-30}", r(0), r(1), r(2)) Next End Sub Is there an case where method 2 provides a performance advantage over method 1?

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• How to implement properly plugins in C#?

  - by MartyIX

  I'm trying to add plugins to my game and what I'm trying to implement is this: Plugins will be either mine or 3rd party's so I would like a solution where crashing of the plugin would not mean crashing of the main application. Methods of plugins are called very often (for example because of drawing of game objects). What I've found so far: 1) http://www.codeproject.com/KB/cs/pluginsincsharp.aspx - simple concept that seems like it should work nicely. Since plugins are used in my game for every round I would suffice to add the Restart() method and if a plugin is no longer needed Unload() method + GC should take care of that. 2) http://mef.codeplex.com/Wikipage - Managed Extensibility Framework - my program should work on .NET 3.5 and I don't want to add any other framework separately I want to write my plugin system myself. Therefore this solution is out of question. 3) Microsoft provides: http://msdn.microsoft.com/en-us/library/system.addin.aspx but according to a few articles I've read it is very complex. 4) Different AppDomains for plugins. According to Marc Gravell ( http://stackoverflow.com/questions/665668/usage-of-appdomain-in-c ) different AppDomains allow isolation. Unloading of plugins would be easy. What would the performance load be? I need to call methods of plugins very often (to draw objects for example). Using Application Domains - http://msdn.microsoft.com/en-us/library/yb506139.aspx A few tutorials on java2s.com Could you please comment on my findings? New approaches are also welcomed! Thanks!

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• Non-blocking TCP buffer issues.

  - by Poni

  Hi! I think I'm in a problem. I have two TCP apps connected to each other which use winsock I/O completion ports to send/receive data (non-blocking sockets). Everything works just fine until there's a data transfer burst. The sender starts sending incorrect/malformed data. I allocate the buffers I'm sending on the stack, and if I understand correctly, that's a wrong to do, because these buffers should remain as I sent them until I get the "write complete" notification from IOCP. Take this for example: void some_function() { char cBuff[1024]; // filling cBuff with some data WSASend(...); // sending cBuff, non-blocking mode // filling cBuff with other data WSASend(...); // again, sending cBuff // ..... and so forth! } If I understand correctly, each of these WSASend() calls should have its own unique buffer, and that buffer can be reused only when the send completes. Correct? Now, what strategies can I implement in order to maintain a big sack of such buffers, how should I handle them, how can I avoid performance penalty, etc'? And, if I am to use buffers that means I should copy the data to be sent from the source buffer to the temporary one, thus, I'd set SO_SNDBUF on each socket to zero, so the system will not re-copy what I already copied. Are you with me? Please let me know if I wasn't clear.

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• How to deal with recursive dependencies between static libraries using the binutils linker?

  - by Jack Lloyd

  I'm porting an existing system from Windows to Linux. The build is structured with multiple static libraries. I ran into a linking error where a symbol (defined in libA) could not be found in an object from libB. The linker line looked like g++ test_obj.o -lA -lB -o test The problem of course being that by the time the linker finds it needs the symbol from libA, it has already passed it by, and does not rescan, so it simply errors out even though the symbol is there for the taking. My initial idea was of course to simply swap the link (to -lB -lA) so that libA is scanned afterwards, and any symbols missing from libB that are in libA are picked up. But then I find there is actually a recursive dependency between libA and libB! I'm assuming the Visual C++ linker handles this in some way (does it rescan by default?). Ways of dealing with this I've considered: Use shared objects. Unfortunately this is undesirable from the perspective of requiring PIC compliation (this is performance sensitive code and losing %ebx to hold the GOT would really hurt), and shared objects aren't needed. Build one mega ar of all of the objects, avoiding the problem. Restructure the code to avoid the recursive dependency (which is obviously the Right Thing to do, but I'm trying to do this port with minimal changes). Do you have other ideas to deal with this? Is there some way I can convince the binutils linker to perform rescans of libraries it has already looked at when it is missing a symbol?

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• Maximum page fetch with maximum bandwith

  - by Ehsan

  Hi I want to create an application like a spider I've implement fetching page as the following code in multi-thread application but there is two problem 1) I want to use my maximum bandwidth to send/receive request, how should I config my request to do so (Like Download Accelerator application and the like) cause I heard the normal application will use 66% of the available bandwidth. 2) I don't know what exactly HttpWebRequest.KeepAlive do, but as its name implies I think i can create a connection to a website and without closing the connection sending another request to that web site using existing connection. does it boost performance or Im wrong ?? public PageFetchResult Fetch() { PageFetchResult fetchResult = new PageFetchResult(); try { HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(URLAddress); HttpWebResponse resp = (HttpWebResponse)req.GetResponse(); Uri requestedURI = new Uri(URLAddress); Uri responseURI = resp.ResponseUri; string resultHTML = ""; byte[] reqHTML = ResponseAsBytes(resp); if (!string.IsNullOrEmpty(FetchingEncoding)) resultHTML = Encoding.GetEncoding(FetchingEncoding).GetString(reqHTML); else if (!string.IsNullOrEmpty(resp.CharacterSet)) resultHTML = Encoding.GetEncoding(resp.CharacterSet).GetString(reqHTML); req.Abort(); resp.Close(); fetchResult.IsOK = true; fetchResult.ResultHTML = resultHTML; } catch (Exception ex) { fetchResult.IsOK = false; fetchResult.ErrorMessage = ex.Message; } return fetchResult; }

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• Pitfalls and practical Use-Cases: Toplink, Hibernate, Eclipse Link, Ibatis ...

  - by Martin K.

  I worked a lot with Hibernate as my JPA implementation. In most cases it works fine! But I have also seen a lot of pitfalls: Remoting with persisted Objects is difficult, because Hibernate replaces the Java collections with its own collection implementation. So the every client must have the Hibernate .jar libraries. You have to take care on LazyLoading exceptions etc. One way to get around this problem is the use of webservices. Dirty checking is done against the Database without any lock. "Delayed SQL", causes that the data access isn't ACID compliant. (Lost data...) Implict Updates So we don't know if an object is modified or not (commit causes updates). Are there similar issues with Toplink, Eclipse Link and Ibatis? When should I use them? Have they a similar performance? Are there reasons to choose Eclipse Link/Toplink... over Hibernate?

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• Is it possible that a single-threaded program is executed simultaneously on more than one CPU core?

  - by Wolfgang Plaschg

  When I run a single-threaded program that i have written on my quad core Intel i can see in the Windows Task Manager that actually all four cores of my CPU are more or less active. One core is more active than the other three, but there is also activity on those. There's no other program (besided the OS kernel of course) running that would be plausible for that activitiy. And when I close my program all activity an all cores drops down to nearly zero. All is left is a little "noise" on the cores, so I'm pretty sure all the visible activity comes directly or indirectly (like invoking system routines) from my program. Is it possible that the OS or the cores themselves try to balance some code or execution on all four cores, even it's not a multithreaded program? Do you have any links that documents this technique? Some infos to the program: It's a console app written in Qt, the Task Manager states that only one thread is running. Maybe Qt uses threads, but I don't use signals or slots, nor any GUI. Link to Task Manager screenshot: http://img97.imageshack.us/img97/6403/taskmanager.png This question is language agnostic and not tied to Qt/C++, i just want to know if Windows or Intel do to balance also single-threaded code on all cores. If they do, how does this technique work? All I can think of is, that kernel routines like reading from disk etc. is scheduled on all cores, but this won't improve performance significantly since the code still has to run synchronous to the kernel api calls. EDIT Do you know any tools to do a better analysis of single and/or multi-threaded programs than the poor Windows Task Manager?

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• Experiences with (free) embedded TCP / IP stacks?

  - by Dan

  Does anyone have especially good (or bad) experiences with any of the following embedded TCP / IP stacks? uIP lwIP Bentham's TCP/IP Lean implementation The TCP/IP stack from this book My needs are for a solid, easy-to-port stack. Code size isn't terribly important, performance is relatively important, but ease of use & porting is very important. The system will probably use an RTOS, that hasn't been decided, but in my experience most stacks can be used with or without an RTOS. Most likely the platform will be an ARM variant (ARM7 or CM3 in all likelihood). Not too concerned about bolting the stack to the Ethernet driver, so that isn't a big priority in the selection. I'm not terribly interested in extracting a stack out of an OS, such as Linux, RTEMS, etc. I'm also not interested in commercial offerings such as Interniche, Micrium, etc... The stack doesn't need all sorts of bells & whistles, doesn't need IPv6, and I don't need any stuff on top of it (web servers, FTP servers, etc..) In fact it's possible that I'll only use UDP, although I can envision a couple scenarios where TCP would be preferable. Experiences with other stacks I've missed are of course also very much of interest. Thanks for your time & input.

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• Application passwords and SQLite security

  - by Bryan

  I have been searching on google for information regarding application passwords and SQLite security for some time, and nothing that I have found has really answered my questions. Here is what I am trying to figure out: 1) My application is going to have an optional password activity that will be called when the application is first opened. My questions for this are a) If I store the password via android preference or SQLite database, how can I ensure security and privacy for the password, and b) how should password recovery be handled? Regarding b) from above, I have thought about requiring an email address when the password feature is enabled, and also a password hint question for use when requesting password recovery. Upon successfully answering the hint question, the password is then emailed to the email address that was submitted. I am not completely confident in the security and privacy of the email method, especially if the email is sent when the user is connected to an open, public wireless network. 2) My application will be using an SQLite database, which will be stored on the SD card if the user has one. Regardless of whether it is stored on the phone or the SD card, what options do I have for data encryption, and how does that affect the application performance? Thanks in advance for time taken to answer these questions. I think that there may be other developers struggling with the same concerns.

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• How to invalidate cache when benchmarking?

  - by Michael Buen

  I have this code, that when swapping the order of UsingAs and UsingCast, their performance also swaps. using System; using System.Diagnostics; using System.Linq; using System.IO; class Test { const int Size = 30000000; static void Main() { object[] values = new MemoryStream[Size]; UsingAs(values); UsingCast(values); Console.ReadLine(); } static void UsingCast(object[] values) { Stopwatch sw = Stopwatch.StartNew(); int sum = 0; foreach (object o in values) { if (o is MemoryStream) { var m = (MemoryStream)o; sum += (int)m.Length; } } sw.Stop(); Console.WriteLine("Cast: {0} : {1}", sum, (long)sw.ElapsedMilliseconds); } static void UsingAs(object[] values) { Stopwatch sw = Stopwatch.StartNew(); int sum = 0; foreach (object o in values) { if (o is MemoryStream) { var m = o as MemoryStream; sum += (int)m.Length; } } sw.Stop(); Console.WriteLine("As: {0} : {1}", sum, (long)sw.ElapsedMilliseconds); } } Outputs: As: 0 : 322 Cast: 0 : 281 When doing this... UsingCast(values); UsingAs(values); ...Results to this: Cast: 0 : 322 As: 0 : 281 When doing just this... UsingAs(values); ...Results to this: As: 0 : 322 When doing just this: UsingCast(values); ...Results to this: Cast: 0 : 322 Aside from running them independently, how to invalidate the cache so the second code being benchmarked won't receive the cached memory of first code? Benchmarking aside, just loved the fact that modern processors do this caching magic :-)

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• Several Small, Specific, MySQL Query Cache Questions

  - by Robbie

  I've look all over the web and in the questions asked here about MySQL caching and most of them seem very non-specific about a couple of questions that I have about performance and MySQL query caching. Specifically I want answers to these questions, assume for all questions that I have the query cache enabled and it is of type 2, or "DEMAND": Is the query cache per table, per database, or per server? Meaning if I have the cache size set to X and have T tables and D databases will I be caching TX, DX, or X amount of data? If I have table T1 which I regularly use the SQL_CACHE hint on for SELECT queries and table T2 which I never do, when I query T2 with a SELECT query will it check through the cache first before performing the query? *Note: I don't want to use the SQL_NO_CACHE for all T2 queries.* Assume the same situation as in question 2. If I alter (INSERT, DELETE) table T2 will any processing be done on the cache? For answers to 2 and 3, is this processing time negligible if T2 is constantly being altered and is the target of a majority of my SELECT queries?

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• What type of webapp is the sweet spot for Scala's Lift framework?

  - by ajay

  What kind of applications are the sweet spot for Scala's lift web framework. My requirements: Ease of development and maintainability Ready for production purposes. i.e. good active online community, regular patches and updates for security and performance fixes etc. Framework should survive a few years. I don't want to write a app in a framework for which no updates/patches are available after 1 year. Has good UI templating engines Interoperation with Java (Scala satisfies this arleady. Just mentioning here for completeness sake) Good component oriented development. Time required to develop should be proportion to the complexity of web application. Should not be totally configuration based. I hate it when code gets automatically generated for me and does all sorts of magic under the hood. That is a debugging nightmare. Amount of Lift knowledge required to develop a webapp should be proportional to the complexity of the web application. i.e I should't have to spend 10+ hours learning Lift just to develop a simple TODO application. (I have knowledge of Databases, Scala) Does Lift satisfy these requirements?

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• video streaming infrastructure

  - by alchemical

  We would like to set-up a live video-chat web site and are looking for basic architectural advice and/or a recomendation for a particular framework to use. Here are the basic features of the site: Most streams will be broadcast live from a single person with a web cam, etc., and viewed by typically 1-10 people, although there could be up to 100+ viewers on the high side. Audio and video do not have to be super-high quality, but do need to be "good enough". The main point is to convey the basic info in the video (and audio). If occasionally the frame-rate drops low and then goes back to normal fairly soon, we could live with that. Budget is an issue, so we are in general looking for a lower cost solution that will give us most of what we need in temers of performance and quality. We are looking at Peer1 for co-lo. The rest of our web site will be .Net / Windows platform. We are open to looking at any platform for the best streaming solution, although our technical expertise is currently more on the Windows side.

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• My OpenCL kernel is slower on faster hardware.. But why?

  - by matdumsa

  Hi folks, As I was finishing coding my project for a multicore programming class I came up upon something really weird I wanted to discuss with you. We were asked to create any program that would show significant improvement in being programmed for a multi-core platform. I’ve decided to try and code something on the GPU to try out OpenCL. I’ve chosen the matrix convolution problem since I’m quite familiar with it (I’ve parallelized it before with open_mpi with great speedup for large images). So here it is, I select a large GIF file (2.5 MB) [2816X2112] and I run the sequential version (original code) and I get an average of 15.3 seconds. I then run the new OpenCL version I just wrote on my MBP integrated GeForce 9400M and I get timings of 1.26s in average.. So far so good, it’s a speedup of 12X!! But now I go in my energy saver panel to turn on the “Graphic Performance Mode” That mode turns off the GeForce 9400M and turns on the Geforce 9600M GT my system has. Apple says this card is twice as fast as the integrated one. Guess what, my timing using the kick-ass graphic card are 3.2 seconds in average… My 9600M GT seems to be more than two times slower than the 9400M.. For those of you that are OpenCL inclined, I copy all data to remote buffers before starting, so the actual computation doesn’t require roundtrip to main ram. Also, I let OpenCL determine the optimal local-worksize as I’ve read they’ve done a pretty good implementation at figuring that parameter out.. Anyone has a clue? edit: full source code with makefiles here http://www.mathieusavard.info/convolution.zip cd gimage make cd ../clconvolute make put a large input.gif in clconvolute and run it to see results

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• Problem with Binding Multiple Objects on WPF

  - by Diego Modolo Ribeiro

  Hi, I'm developing a user control called SearchBox, that will act as a replacer for ComboBox for multiple records, as the performance in ComboBox is low for this scenario, but I'm having a big binding problem. I have a base control with a DependencyProperty called SelectedItem, and my SearchControl shows that control so that the user can select the record. The SearchControl also has a DependencyProperty called SelectedItem on it, and it is being updated when the user selects something on the base control, but the UI, wich has the SearchControl, is not being updated. I used a null converter so that I could see if the property was updating, but it's not. Below is some of the code: This is the UI: <NectarControles:MaskedSearchControl x:Name="teste" Grid.Row="0" Grid.Column="1" Height="21" ItemsSource="{Binding C001_Lista}" DisplayMember="C001_Codigo" Custom:CustomizadorTextBox.CodigoCampo="C001_Codigo" ViewType="{x:Type C001:C001_Search}" ViewModelType="{x:Type C001_ViewModel:C001_ViewModel}" SelectedItem="{Binding Path=Instancia.C001_Holding, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, Converter={StaticResource DebuggingConverter}}"> </NectarControles:MaskedSearchControl> This is the relevante part of the SearchControl: Binding selectedItemBinding = new Binding("SelectedItem"); selectedItemBinding.Source = this.SearchControlBase; selectedItemBinding.Mode = BindingMode.TwoWay; selectedItemBinding.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged; this.SetBinding(SelectedItemProperty, selectedItemBinding); ... public System.Data.Objects.DataClasses.IEntityWithKey SelectedItem { get { return (System.Data.Objects.DataClasses.IEntityWithKey)GetValue(SelectedItemProperty); } set { SetValue(SelectedItemProperty, value); if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs("SelectedItem")); } } Please someone help me... Tks...

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• Is Annotation in Javascript? If not, how to switch between debug/productive modes in declarative way

  - by Michael Mao

  Hi all: This is but a curious question. I cannot find any useful links from Google so it might be better to ask the gurus here. The point is: is there a way to make "annotation" in javascript source code so that all code snippets for testing purpose can be 'filtered out' when project is deployed from test field into the real environment? I know in Java, C# or some other languages, you can assign an annotation just above the function name, such as : // it is good to remove the annoying warning messages @SuppressWarnings("unchecked") public class Tester extends TestingPackage { ... } Basically I've got a lot of testing code that prints out something into FireBug console. I don't wanna manually "comment out" them because the guy that is going to maintain the code might not be aware of all the testing functions, so he/she might just miss one function and the whole thing can be brought down to its knees. One other thing, we might use a minimizer to "shrink" the source code into "human unreadable" code and boost up performance (just like jQuery.min), so trying to match testing section out of the mess is not possible for plain human eyes in the future. Any suggestion is much appreciated.

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• Design: Website calling a webservice on the same machine

  - by Chris L

  More of a design/conceptual question. At work the decision was made to have our data access layer be called through webservices. So our website would call the webservices for any/all data to and from the database. Both the website & the webservices will be on the same machine(so no trip across the wire), but the database is on a separate machine(so that would require a trip across the wire regardless). This is all in-house, the website, webservice, and database are all within the same company(AFAIK, the webservices won't be reused by another other party). To the best of my knowledge: the website will open a port to the webservices, and the webservices will in turn open another port and go across the wire to the database server to get/submit the data. The trip across the wire can't be avoided, but I'm concerned about the webservices standing in the middle. I do agree there needs to be distinct layers between the functionality(such as business layer, data access layer, etc...), but this seems overly complex to me. I'm also sensing there will be some performance problems down the line. Seems to me it would be better to have the (DAL)assemblies referenced directly within the solution, thus negating the first port to port connection. Any thoughts(or links) both for and against this idea would be appreciated P.S. We're a .NET shop(migrating from vb to C# 3.5)

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