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• Java bytecode compiler benchmarks

  - by Dave Jarvis

  Q.1. What free compiler produces the fastest executable Java bytecode? Q.2. What free virtual machine executes Java bytecode the fastest (on 64-bit multi-core CPUs)? Q.3. What other (currently active) compiler projects are missing from this list: http://www.ibm.com/developerworks/java/jdk/ http://gcc.gnu.org/java/ http://openjdk.java.net/groups/compiler/ http://java.sun.com/javase/downloads/ http://download.eclipse.org/eclipse/downloads/ Q.4. What performance improvements can compilers do that JITs cannot (or do not)? Q.5. Where are some recent benchmarks, comparisons, or shoot-outs (for Q1 or Q2)? Thank you!

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• Data logged to a file; how do I rotate logs and how do I parse the data to not have 'gaps' in the da

  - by phidah

  I've got a web application that, for performance reasons, throws any data sent into a logfile. I've got two concerns with this approach: How do I best rotate logs, in order to not lose data? For each user session multiple requests are logged. Each request has a unique id so there is an easy way for me to tie the requests to the session. The problem is, however, that if I rotate the logs I risk ending up with one request in one log and another request in another log. How do I arrange my parsing in a way that allows me to parse all requests from a given session? I am willing to define a session timelimit, for example that the requests must, at maximum be 30 minutes apart. If I had a hourly log rotation at 00 minutes: What if the user made one request at 13:59 and one at 14:01 - The user would end up having requests in two different logs.

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• Why dont Android applications provide an "Exit" option?

  - by Howiecamp

  Is there something in the Android developer guidelines that disuadea developers from providing the option to "exit" (stop running) an application from within the application itself? I love multitasking and all but it's not clear to me why: the vast majority of apps don't have their own Exit functions and hence just keep running forever don't give you a choice about running when you turn on the phone - they just do by default Both of these things lead to memory usage constantly increasing and your device running with this performance burden all of the time despite the fact that you may only want certain apps to run some of the time. Am I missing something?

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• When getting substring in .Net, does the new string reference the same original string data or does

  - by Elan

  Assuming I have the following strings: string str1 = "Hello World!"; string str2 = str1.SubString(6, 5); // "World" I am hoping that in the above example str2 does not copy "World", but simply ends up being a new string that points to the same memory space only that it starts with an offset of 6 and a length of 5. In actuality I am dealing with some potentially very long strings and am interested in how this works behind the scenes for performance reasons. I am not familiar enaugh with IL to look into this.

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• nginx-tornado-django request timeout

  - by Xie

  We are using nginx-tornado-django to provide web services. That is, no web page frontend. The nginx server serves as a load-balancer. The server has 8 cores, so we launched 8 tornado-django processes on every server. Memcached is also deployed to gain better performance. The requests per day is about 1 million per server. We use MySQL as backend DB. The code is tested and correct. Our profiling shows that normally every request are processed within 100ms. The problem is, we find that about 10 percent of the requests suffers from time-out issue. Many requests didn't even reach tornado. I really don't have much experience on tuning of nginx/tornado/MySQL. Right now I don't have a clue on what is going wrong. Any advise is appreiciated.

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• MS Sql Full-text search vs. LIKE expression

  - by Marks

  Hi. I'm currently looking for a way to search a big database (500MB - 10GB or more on 10 tables) with a lot of different fields(nvarchars and bigints). Many of the fields, that should be searched are not in the same table. An example: A search for '5124 Peter' should return all items, that ... have an ID with 5124 in it, have 'Peter' in the title or description have item type id with 5124 in it created by a user named 'peter' or a user whose id has 5124 in it created by a user with '5124' or 'peter' in his street address. How should i do the search? I read that the full-text search of MS-Sql is a lot more performant than a query with the LIKE keyword and i think the syntax is more clear, but i think it cant search on bigint(id) values and i read it has performance problems with indexing and therefore slows down inserts to the DB. In my project there will be more inserting than reading, so this could be a matter. Thanks in advance, Marks

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• Does a System.Collection.Collection<T> wrap a IList<T> or enumerate over the IList<T> or simply wra

  - by Brian Triplett

  If I am exposing a internal member via a Collection property via: public Collection<T> Entries { get { return new Collection<T>(this.fieldImplimentingIList<T>); } } When this property is called what happens? For example what happens when the following lines of code are called: T test = instanceOfAbove.Entries[i]; instanceOfAbove[i] = valueOfTypeT; It's clear that each time this property is called a new reference type is created but what acctually happens? Does it simply wrap the IList<T> underneath, does it enumerate over the IList<T> and to create a new Collection<T> instance? I'm concerned about performance if this property is used in a for loop.

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• Putting WPF Control (ComboBox) into canvas with Visuals

  - by Mikhail

  I am writing a WPF chart and use Visuals for performance. The code looks like: public class DrawingCanvas2 : Canvas { private List<Visual> _visuals = new List<Visual>(); protected override Visual GetVisualChild( int index ) { return _visuals[index]; } protected override int VisualChildrenCount { get { return _visuals.Count; } } public void AddVisual( Visual visual ) { _visuals.Add( visual ); base.AddVisualChild( visual ); base.AddLogicalChild( visual ); } } Beside DrawingVisual elements (line, text) I need a ComboBox in the chart. So I tried this: public DrawingCanvas2() { ComboBox box = new ComboBox(); AddVisual( box ); box.Width = 100; box.Height = 30; Canvas.SetLeft( box, 10 ); Canvas.SetTop( box, 10 ); } but it does not work, there is no ComboBox displayed. What I am missing?

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• MySqlDataAdapter or MySqlDataReader for bulk transfer?

  - by Jeff Meatball Yang

  I'm using the MySql connector for .NET to copy data from MySql servers to SQL Server 2008. Has anyone experienced better performance using one of the following, versus the other? DataAdapter and calling Fill to a DataTable in chunks of 500 DataReader.Read to a DataTable in a loop of 500 I am then using SqlBulkCopy to load the 500 DataTable rows, then continue looping until the MySql record set is completely transferred. I am primarily concerned with using a reasonable amount of memory and completing in a short amount of time. Any help would be appreciated!

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• Partition of tables in MySQL

  - by Joel

  Hello, I have read that in a case where a table has many columns, but most of the time only one of them is used (say a title column in a forum post), a way to increase performance would be a partition to two tables, where one will contain only the title and the other one will contain the other columns (such as the forum post body). However, in case I use select ForumTitle from Forum; won't that be good enough to prevent the load of all columns (such as the forum post's body) to the memory, and eliminate the need of partition? Thanks, Joel

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• Backup Active Directory only

  - by MainMa

  Hi, I have a server with Windows Server 2008. I want to install a new Windows Server 2008 R2 on a new hard disk but on a same machine. What is the way to backup/migrate only Active Directory? I found that migration must be done with Microsoft Active Directory Migration Tool, but it requires both source and target domains running at the same time. Any other suggests are to use an ordinary system backup/restore, but this will restore all other roles, whereas I need only Active Directory role on the new server.

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• Using memtables in sql. When is it reasonable and is it safe?

  - by Spiros

  I was just reading an update from a friend's project, mentioning the use of memtables to store data temporatily and then flush to a table on disk. Up to now, I have never faced a situation where I would use a memtable, or a situation where I would think the use of a mem table would be beneficial; so I wonder, when would someone use mem tables? what makes a memtable (appart from access speed) a reasonable choice? and how safe is it, even for temp data? there is always the limitation of available physical memory.

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• Should I commit or rollback a transaction that creates a temp table, reads, then deletes it?

  - by Triynko

  To select information related to a list of hundreds of IDs... rather than make a huge select statement, I create temp table, insert the ids into it, join it with a table to select the rows matching the IDs, then delete the temp table. So this is essentially a read operation, with no permanent changes made to any persistent database tables. I do this in a transaction, to ensure the temp table is deleted when I'm finished. My question is... what happens when I commit such a transaction vs. let it roll it back? Performance-wise... does the DB engine have to do more work to roll back the transaction vs committing it? Is there even a difference since the only modifications are done to a temp table? Related question here, but doesn't answer my specific case involving temp tables: http://stackoverflow.com/questions/309834/should-i-commit-or-rollback-a-read-transaction

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• Any exprience with Castle ActiveRecord?

  - by afsharm

  Hi all, I was searching for a light data access framework based on NHibernate. I needed simple CRUD and some simple HQL or LINQ-to-NHhibernate queries. Performance was not an important issue and applications which I'm working on have simple table structure but many tables. This data access framework is going to be used in a ASP.NET Webform application. Once a time I found S#harp architecture, but it was developed for ASP.NET MVC. Just today I found Castle ActiveRecord. But I'm wondering: If any one has any experience with it? Is it suitable for me? Should I consider any specific matter? What about its future? Is Castle ActiveRecord supposed to be developed and be active in coming years? Thanks in Advance

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• Has anyone ever encountered a Monad Transformer in the wild?

  - by martingw

  In my area of business - back office IT for a financial institution - it is very common for a software component to carry a global configuration around, to log it's progress, to have some kind of error handling / computation short circuit... Things that can be modelled nicely by Reader-, Writer-, Maybe-monads and the like in Haskell and composed together with monad transformers. But there seem to some drawbacks: The concept behind monad transformers is quite tricky and hard to understand, monad transformers lead to very complex type signatures, and they inflict some performance penalty. So I'm wondering: Are monad transformers best practice when dealing with those common tasks mentioned above?

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• How to think in data stores instead of databases?

  - by Jim

  As an example, Google App Engine uses data stores, not a database, to store data. Does anybody have any tips for using data stores instead of databases? It seems I've trained my mind to think 100% in object relationships that map directly to table structures, and now it's hard to see anything differently. I can understand some of the benefits of data stores (e.g. performance and the ability to distribute data), but some good database functionality is sacrificed (e.g. joins). Does anybody who has worked with data stores like BigTable have any good advice to working with them?

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• Choosing a plotting library for web/browser application

  - by Goro

  Hello, I am looking for a plotting/graphing library (mostly to do line plots) for my application. I have been looking at JavaScript APIs (like Google's) but I found them to be slowing down things at client side (I am plotting a quite large number of points). I also found that with client-side libraries, the performance was quite varied depending on the user's computer. With moving to a server-side library I would cut down on this variance, and would have more control over data flow (my data is in a MySQL database). I have then looked at some PHP-based plotting libraries, but a lot of them seem to be "forgotten" (no new version for years). I have been eying pChart, but it has not had an update in almost two years. First, what would you recommend: server-side or client-side approach? Second, what library would you recommend. Paid libraries are definitely an option, as I don't mind paying for quality software that would cut down on my development time. Thanks,

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• How to insert bulk data into mysql table from asp.net at once.

  - by kranthi

  Hi, I have a requirement that I need to read an excel sheet using asp.net/C# and insert all the records into mysql table.The excel sheet consists of around 2000 rows and 50 columns. Currently,upon reading the excel records ,I am inserting the records one by one using a prepare statement into mysql table.But its taking around 70 secs to do so because of the huge data. I've also thought of creating a new datarow, assigning values to each cell,adding the resulting datarow to datatable and finally calling dataadapter.update(...).But it seems to be complex because I got around 50 columns and hence I'll have to assign 50 values to the datarow. Could someone please suggest if there is an alternate to improve the performance of the insertion? Thanks

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• Where to execute extra logic for linq to entities query?

  - by Inez

  Let say that I want to populate a list of CustomerViewModel which are built based on Customer Entity Framework model with some fields (like Balance) calculated separately. Below I have code which works for lists - it is implemented in my service layer, but also I want to execute this code when I just get one item from the database and execute is as well in different services where I'm accessing Customers data as well. How should I do this to ensure performance but to to not duplicate code - the one for calculating Balance? public List<CustomerViewModel> GetCustomerViewModelList() { IQueryable<CustomerViewModel> list = from k in _customerRepository.List() select new CustomerViewModel { Id = k.Id, Name = k.Name, Balance = k.Event.Where(z => z.EventType == (int) EventTypes.Income).Sum(z => z.Amount) }; return list.ToList(); }

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• How to monitor MySQL query errors, timeouts and logon attempts?

  - by Abel

  While setting up a third party closed source CMS (Sitefinity) the setup doesn't create all tables and procedures necessary to run it. The software lacks a logging system itself and it made me wonder: could I trace and monitor failing SQL statements from MySQL? This serves more than only the purpose of solving my issue with Sitefinity. More often I wonder what's send to the MySQL server, not wanting to dive into the software products or setup a debugging environment etc. I tried JetProfiler (only performance) and looked through a few others, but although they monitor a lot, they don't monitor query failures, timeouts or logon attempts. Does anyone know a profiler, tracer, monitoring tool, commercial or free, that can show me this information?

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• Oracle: '= ANY()' vs. 'IN ()'

  - by eidylon

  Hi all, I just stumbled upon something in ORACLE SQL (not sure if it's in others), that I am curious about. I am asking here as a wiki, since it's hard to try to search symbols in google... I just found that when checking a value against a set of values you can do WHERE x = ANY (a, b, c) As opposed to the usual WHERE x IN (a, b, c) So I'm curious, what is the reasoning for these two syntaxes? Is one standard and one some oddball Oracle syntax? Or are they both standard? And is there a preference of one over the other for performance reasons, or ? Just curious what anyone can tell me about that '= ANY' syntax. CheerZ!

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• Using * in SELECT Query

  - by libregeek

  I am currently porting an application written in MySQL3 and PHP4 to MySQL5 and PHP5. On analysis I found several SQL queries which uses "select * from tablename" even if only one column(field) is processed in PHP. The table has almost 60 columns and it has a primary key. In most cases, the only column used is id which is the primary key. Will there be any performance boost if I use queries in which the column names are explicitly mentioned instead of * ? (In this application there is only one method which we need all the columns and all other methods return only a subset of the columns)

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• How to make scrolling through images as fast as Apple's Photos app

  - by clozach

  The Goal — On an iPhone, to browse through several hundred locally-stored jpgs using a UIScrollView. The Problem — Like many others before me, I've tried implementing a scroll view based on Apple's Page Control sample code and found it lacking. The biggest issue I'm currently up against is that the sample code's architecture doesn't seem to scale. With just a few images loaded from disk, everything's fine. Once the number of images gets into the dozens, though, scrolling suffers terribly: the scrollview stutters mid-scroll with each new swipe. The only code I've toyed with that comes even close to being reasonably responsive is Three20, but even there the performance doesn't hold a candle to Photos. For now, I'm just using Three20, but a faster, custom solution would definitely be preferable.

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• What are the Pros & Cons of using SQL Azure for existing apps on dedicated servers

  - by Mark Redman

  We currently own our own servers, and rent a rack in a datacentre. Looking at the pricing, scalabilty and SLAs for Azure SQL, I am thinking that it might be viable to only use Azure SQL but continue to use our existing applications on our own servers in a datacentres. This will enable us to not worry about the database and its infrastructure so we can concentrate on building an application server farm with disk storeage for files etc. Our application is quite big and has various windows services and parts of it used unmanaged libraries that may not be feasible in the cloud, so probably coulnt have everything in the Azure cloud. The pros: Reduced Total Cost of ownership (no database servers, no sql server licenses) The Cons: I guess there would be overhead in the transfer of data between the Azure Cloud and our datacentre (ie cloud may be in US and datacentre is in the UK) but would this overhead be usable?

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• Any really modern, good-looking desktop apps that are developed with PyQt/PySide?

  - by Edwin

  Hi, I have started using Python for web development recently, it's kinda cool; I have seen programs that are developed in QT/C++, which is good enough in terms of esthetics; I have just noticed the new PySide project (which brings LGPL Qt license to Python and it doesn't support Windows yet). In view of the above, I see the possibility of using Python + PyQt/PySide to develop cross platform apps in the future :) but I have several doubts right now: Can PyQty/PySide be used to develop really complex/modern UI? Can somebody give me some points to have a look at some nice-looking screenshots of apps that are developed in Python+QT? What about the performance? Thanks in advance!

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