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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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• 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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• 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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• 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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• Merge overlapping triangles into a polygon

  - by nornagon

  I've got a bunch of overlapping triangles from a 3D model projected into a 2D plane. I need to merge each island of touching triangles into a closed, non-convex polygon. The resultant polygons shouldn't have any holes in them (since the source data doesn't). Many of the source triangles share (floating point identical) edges with other triangles in the source data. What's the easiest way to do this? Performance isn't particularly important, since this will be done at design time.

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• Jquery selectors by CSS class in IE is really slow--workarounds?

  - by Sam Lee

  I have a web app where I have several elements with class="classA". I want to select and apply a function to all of them. I am doing the obvious thing, which is $(".classA").each(function () { ... }). This works just fine in Chrome/Safari/Firefox but is really slow in IE. It turns out IE has serious performance issues when selecting things by CSS class in jQuery. I was wondering if anyone has suggestions on good ways to deal with this. I can't use ID selectors because there can be multiple DOM elements I want to select.

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• Rails Unit Testing with MyISAM Tables

  - by tadman

  I've got an application that requires the use of MyISAM on a few tables, but the rest are the traditional InnoDB type. The application itself is not concerned with transactions where it applies to these records, but performance is a concern. The Rails testing environment assumes the engine used is transactional, though, so when the test database is generated from the schema.rb it is imported with the same engine. Is it possible to over-ride this behaviour in a simple manner? I've resorted to an awful hack to ensure the tables are the correct type by appending this to test_helper.rb: (ActiveRecord::Base.connection.select_values("SHOW TABLES") - %w[ schema_info ]).each do |table_name| ActiveRecord::Base.connection.execute("ALTER TABLE `#{table_name}` ENGINE=InnoDB") end Is there a better way to make a MyISAM-backed model be testable?

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• render HTML (convert to bitmap)

  - by MK

  Can somebody recommend the best (and preferably portable) way to render HTML documents onto a bitmap? As far as I understand my main 2 options are WebKit and Gecko, but I wasn't able to find a good starting point on how to do it. When I last tried doing this 5 years ago, I ended up using Gecko to send the document to a printer, which is not really what I need. I need rendering to a in-memory bitmap. To clarify: server side, no Java, no .NET, batch processing, performance, not interactive, no Javascript.

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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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• I don't understand Application Domains

  - by Jeremy Edwards

  .NET has this concept of Application Domains which from what I understand can be used to load an assembly into memory. I've done some research on Application Domains as well as go to my local book store for some additional knowledge on this subject matter but it seems very scarce. All I know that I can do with Application Domains is to load assemblies in memory and I can unload them when I want. What are the capabilities other that I have mentioned of Application Domains? Do Threads respect Application Domains boundaries? Are there any drawbacks from loading Assemblies in different Application Domains other than the main Application Domains beyond performance of communication? Links to resources that discuss Application Domains would be nice as well. I've already checked out MSDN which doesn't have that much information about them.

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• Speeding up CakePHP

  - by DavidYell

  I've been a keen fan and user of CakePHP for about 2.5 years now, but the main bugbear that most fellow developers level at the framework is that it's slow, and the dispatch cycle takes too long to make it a viable solution for production environments. I'm hoping that this question will inspire people to share their tips, tricks and hacks for speeding up CakePHP performance. The blog post I most often refer to is here, http://www.pseudocoder.com/archives/8-ways-to-speed-up-cakephp-apps Which has great tips, but there must be more out there! So please feel free to share your thoughts on making this excellent framework that much more nimble!

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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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• Sql server indexed view

  - by Jose

  OK, I'm confused about sql server indexed views(using 2008) I've got an indexed view called AssignmentDetail when I look at the execution plan for select * from AssignmentDetail it shows the execution plan of all the underlying indexes of all the other tables that the indexed view is supposed to abstract away. I would think that the execution plan woul simply be an clustered index scan of PK_AssignmentDetail(the name of the clustered index for my view) but it doesn't. There seems to be no performance gain with this indexed view what am I supposed to do? Should I also create a non-clustered index with all of the columns so that it doesn't have to hit all the other indexes? Any insight would be greatly appreciated

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• Saving Blob data from SQLite database to a file

  - by Felipe

  Hello, I'm trying to save blob data from a SQLite database (Safari cache: Cache.db) to a file, but for some reason sqlite won't read the whole blob. I eventually would like to do this in ruby, but for now something that works directly in sqlite command prompt is fine. Also, I've read all of the entries that talk about this here on stackoverflow, but most of them only discuss the performance of saving images in blobs and the one entry that does show to save blobs to file is in C# which does not help me. Here is what I've tried: sqlite select * from cfurl_cache_response limit 1; 3501|0|945281827|0|http://www.gospelz.com/components/com_jomcomment/smilies/guest.gif|2010-02-24 16:20:07 sqlite select receiver_data from cfurl_cache_blob_data where entry_ID = 3501; GIF89a( A hexdump of the original (guest.gif) file shows that sqlite stops reading the blob after the first null value: $ hexdump -C guest.gif 00000000 47 49 46 38 39 61 28 00 28 00 f7 00 00 f1 f5 fd |GIF89a(.(.......| sqlite .output test.gif sqlite select receiver_data from cfurl_cache_blob_data where entry_ID = 3501; $ hexdump -C test.gif 00000000 47 49 46 38 39 61 28 0a |GIF89a(.|

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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 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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• Table with a lot of attributes

  - by Robert

  Hi, I'm planing to build some database project. One of the tables have a lot of attributes. My question is: What is better, to divide the the class into 2 separate tables or put all of them into one table. below is an example create table User { id, name, surname,... show_name, show_photos, ...) or create table User { id, name, surname,... ) create table UserPrivacy {usr_id, show_name, show_photos, ...) The performance i suppose is similar due to i can use index.

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• spl_object_hash for PHP < 5.2 (unique ID for object instances)

  - by Rowan

  I'm trying to get unique IDs for object instances in PHP 5+. The function, spl_object_hash() is available from PHP 5.2 but I'm wondering if there's a workaround for older versions. There are a couple of functions in the comments on php.net but they're not working for me. The first (simplified): function spl_object_hash($object){ if (is_object($object)){ return md5((string)$object); } return null; } does not work with native objects (such as DOMDocument), and the second: function spl_object_hash($object){ if (is_object($object)){ ob_start(); var_dump($object); $dump = ob_get_contents(); ob_end_clean(); if (preg_match('/^object\(([a-z0-9_]+)\)\#(\d)+/i', $dump, $match)) { return md5($match[1] . $match[2]); } } return null; } looks like it could be a major performance buster! Does anybody have anything up their sleeve?

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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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• Throughput measurements

  - by dotsid

  I wrote simple load testing tool for testing performance of Java modules. One problem I faced is algorithm of throughput measurements. Tests are executed in several thread (client configure how much times test should be repeated), and execution time is logged. So, when tests are finished we have following history: 4 test executions 2 threads 36ms overall time - idle * test execution 5ms 9ms 4ms 13ms T1 |-*****-*********-****-*************-| 3ms 6ms 7ms 11ms T2 |-***-******-*******-***********-----| <-----------------36ms---------------> For the moment I calculate throughput (per second) in a following way: 1000 / overallTime * threadCount. But there is problem. What if one thread will complete it's own tests more quickly (for whatever reason): 3ms 3ms 3ms 3ms T1 |-***-***-***-***----------------| 3ms 6ms 7ms 11ms T2 |-***-******-*******-***********-| <--------------32ms--------------> In this case actual throughput is much better because of measured throughput is bounded by the most slow thread. So, my question is how should I measure throughput of code execution in multithreaded environment.

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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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• Setting up a web developer lab for learning purposes

  - by Saleh Al-Abbas

  I'm not a developer by profession. Therefore, I'm not exposed to real world technical problems that face professional developers. I read/heard about web farms, integration between different systems, load balancing ... etc. Therefore, I was wondering if there are ways for the individual developer to create an environment that simulates real world situations with minimal number of machines like: web farms & caching simulating many users accessing your website (Pressure tests?) Performance load balancing anything you think I should consider. By the way, I have a server machine and 1 PC. and I don't mind investing in tools and software. PS. I'm using Microsoft technologies for development but I hope this is not a limiting factor. Thanks

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• Order hybrid mixed mysql search result in one query?

  - by Fredrik

  This problem is easy fixed clientside. But for performance I want to do it directly to the database. LIST a +------+-------+-------+ | name | score | cre | +------+-------+-------+ | Abe | 3 | 1 | | Zoe | 5 | 2 | | Mye | 1 | 3 | | Joe | 3 | 4 | Want to retrieve a joined hybrid result without duplications. Zoe (1st higest score) Joe (1st last submitted) Abe (2nd highest score) Mye (2nd last submitted) ... Clientside i take each search by itself and step though them. but on 100.000+ its getting awkward. To be able to use the LIMIT function would ease things up a lot! SELECT name FROM a ORDER BY score DESC, cre DESC; SELECT name FROM a ORDER BY cre DESC, score DESC;

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• Automatic layout of manual network mapping

  - by Paul

  So I have a small business network mainly consisting of two routed layer-2 domains with a total of ca. 100 devices spread over ca. 2000m² production and office spaces. Typical problems to solve using the graph would be: Over what (cable) path is a PC connected to the server? Where to expect devices connected to a switch port? I want to generate a graph of the physical network topology: Nodes are endpoint devices, switch ports, wall outlets, patch panel ports etc. Edges are cable connections. Ideally, grouping edges (or segments) that pass through the same bundle could be grouped. Also I would like to augment the graph data with automatically gathered data (monitoring state, MAC address, Switch port <- MAC entries to build up parts of the map). At the moment I use graphviz for this inside a Confluence wiki like that: layout = "neato" overlap = scale subgraph { rankdir = "TB" subgraph cluster_r1pf1 { r1pf1 [label="{ Rack 1 PF 1 | { <p1>P1 | <p2>P2 | <p3>P3} }", shape=record] } subgraph cluster_switch1 { switch1 [label="{ Rack 1 Switch 1 | { <p1> P1 | <p1> P1 | <p3> P3} }", shape=record] } r1pf1:p1 -> switch1:p1 (obviously there are dozens of entries omitted here) Problem is: I have a hard time to influence graphviz to generate a bearable layout. Edges overlap so bad that you can't read the diagram anymore. The question is: What other tools (be it interactive like Visio, Omnigraffle or I/O-oriented like graphviz) exist that would allow an easily versionable (as in: Operates on a text file) documentation that is both machine and human readable and editable? Why not OmniGraffle or Visio? Well we don't have Macs and Visio is not available at the moment. To buy it I would need good arguments. Automation would be one of that. But last time I looked, versioning Visio files or even thinking about automatic handling was a nightmare. Related: Network Mapping Tools basically asks the same with a focus on generating the complete graph automatically (but without the need to document cabling connections) Recommendations for automatic computer inventory brings up links of "all-in-one" solutions

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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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