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• Threading vs single thread

  - by user177883

  Is it always guaranteed that a multi-threaded application would run faster than a single threaded application? I have two threads that populates data from a data source but different entities (eg: database, from two different tables), seems like single threaded version of the application is running faster than the version with two threads. Why would the reason be? when i look at the performance monitor, both cpu s are very spikey ? is this due to context switching? what are the best practices to jack the CPU and fully utilize it? I hope this is not ambiguous.

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• postgreSQL - pg_class question

  - by Sachin Chourasiya

  PostgreSQL stores statistics about tables in the system table called pg_class. The query planner accesses this table for every query. These statistics may only be updated using the analyze command. If the analyze command is not run often, the statistics in this table may not be accurate and the query planner may make poor decisions which can degrade system performance. Another strategy is for the query planner to generate these statistics for each query (including selects, inserts, updates, and deletes). This approach would allow the query planner to have the most up-to-date statistics possible. Why postgres always rely on pg_class instead?

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• Is re-using a Command and Connection object in ado.net a legitimate way of reducing new object creat

  - by Neil Trodden

  The current way our application is written, involves creating a new connection and command object in every method that access our sqlite db. Considering we need it to run on a WM5 device, that is leading to hideous performance. Our plan is to use just one connection object per-thread but it's also occurred to us to use one global command object per-thread too. The benefit of this is it reduces the overhead on the garbage collector created by instantiating objects all over the place. I can't find any advice against doing this but wondered if anyone can answer definitively if this is a good or bad thing to do, and why?

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• Thread.sleep vs Monitor.Wait vs RegisteredWaitHandle?

  - by Royi Namir

  (the following items has different goals , but im interesting knowing how they "PAUSEd") questions Thread.sleep - Does it impact performance on a system ?does it tie up a thread with its wait ? what about Monitor.Wait ? what is the difference in the way they "wait"? do they tie up a thread with their wait ? what aboutRegisteredWaitHandle ? This method accepts a delegate that is executed when a wait handle is signaled. While it’s waiting, it doesn’t tie up a thread. so some thread are paused and can be woken by a delegate , while others just wait ? spin ? can someone please make things clearer ? edit http://www.albahari.com/threading/part2.aspx

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• NHibernate parent-childs save redundant sql update executed

  - by Broken Pipe

  I'm trying to save (insert) parent object with a collection of child objects, all objects are new. I prefer to manually specify what to save\update and when so I do not use any cascade saves in mappings and flush sessions by myself. So basically I save this object graph like: session.Save(Parent) foreach (var child in Parent.Childs) { session.Save(child); } session.Flush() I expect this code to insert Parent row, then each child row, however NHibernate executes this SQL: INSERT INTO PARENT.... INSERT INTO CHILD .... UPDATE CHILD SET ParentId=@1 WHERE Id=@2 This update statement is absolutely unnecessary, ParentId was already set correctly in INSERT. How do I get rid of it? Performance is very important for me.

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• Which Android platform and API to target?

  - by Ben Mc

  I'm just about to launch my first Android app, and it runs on the Android 1.1 platform, API Level 2, but is this what I should officially sign and launch the app as? Does it affect performance at all or is it simply for Android to know which devices it works on? The only problem I see is that I can't specify <supports-screens> in the Manifest, which I would like to do, but it appears I'd have to launch at 1.6 at least for this to work. Would I be missing a huge number of phones by launching at 1.6 instead of 1.1? Thank you!

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• AES acceleration for Java

  - by chris_l

  I want to encrypt/decrypt lots of small (2-10kB) pieces of data. The performance is ok for now: On a Core2Duo, I get about 90 MBytes/s AES256 (when using 2 threads). But I may need to improve that in the future - or at least reduce the impact on the CPU. Is it possible to use dedicated AES encryption hardware with Java (using JCE, or maybe a different API)? Would Java take advantage of special CPU features (SSE5?!), if I get a better CPU? Or are there faster JCE providers? (I tried SunJCE and BouncyCastle - no big difference.) Other possiblilities?

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• For what purpose does java have a float primitive type?

  - by Roman

  I heard plenty times different claims about float type in java. The most popular issues typicaly regard to converting float value to double and vice versa. I read (rather long time ago and not sure that it's actual now with new JVM) that float gives much worse performance then double. And it's also not recommended to use float in scientific applications which should have certain accuracy. I also remember that when I worked with AWT and Swing I had some problems with using float or double (like using Point2D.Float or Point2D.Double). So, I see only 2 advantages of float over double: it needs only 4 bytes while double needs 8 bytes JMM garantees that assignment operation is atomic with float variables while it's not atomic with double's. Are there any other cases where float is better then double? Do you use float's in your applications? It seems to me that the only valuable reason java has float is backward compatibility.

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• How do you handle passwords or credentials for standalone applications?

  - by Abel Morelos

  Let's say that you have a standalone application (a Java application in my case) and that this application has a configuration file (a XML file in my case) where you store the credentials (user and password) for a bunch of databases you need to connect. Everything works great, but now you discover (or your are given a new requirement like me) that you have to put this application in a different server and that you can't have these credentials in the configuration files because of security and/or compliance considerations. I'm considering to use data sources hosted in the application server (a WAS server), but I think this could have poor performance and maybe it's not the best approach since I'm connecting from a standalone application. I was also considering to use some sort of encryption, but I would like to keep things as simple as possible. How would you handle this case? Where would you put these credentials or protect them from being compromised? Or how would you connect to your databases in this scenario?

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• Javascript - Determine if String Is In List

  - by Emtucifor

  In SQL we can see if a string is in a list like so: Column IN ('a', 'b', 'c') What's a good way to do this in javascript? I realize one can use the switch function: var str = 'a' var flag = false; switch (str) { case 'a': case 'b': case 'c': flag = true; default: } if (thisthing || thatthing || flag === true) { // do something } But this is a horrible mess. It's also clunky to do this: if (thisthing || thatthing || str === 'a' || str === 'b' || str = 'c') { // do something } And I'm not sure about the performance or clarity of this: if (thisthing || thatthing || {a:1, b:1, c:1}[str]) { // do something } Any ideas?

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• What is the preferred way to associate css styles with GWT widgets (using UiBinder)?

  - by smallbec

  From the GWT page (http://code.google.com/webtoolkit/doc/latest/DevGuideUiCss.html#cssfiles), it mentions 2 ways (for modern application): Using a CssResource contained within a ClientBundle. Using an inline element in a UiBinder template. Modern GWT applications typically use a combination of CssResource and UiBinder. So my question is, when should I use a css file and create a CssResource for it, and when should I define styles directly in the ui.xml file using <ui:style>? Are there any performance implication (i.e. resource size to download on the client) with either of these ways?

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• ColdFusion static key/value list?

  - by richardtallent

  I have a database table that is a dictionary of defined terms -- key, value. I want to load the dictionary in the application scope from the database, and keep it there for performance (it doesn't change). I gather this is probably some sort of "struct," but I'm extremely new to ColdFusion (helping out another team). Then, I'd like to do some simple string replacement on some strings being output to the browser, looping through the defined terms and replacing the terms with some HTML to define the terms (a hover or a link, details to be worked out later, not important). Can anyone point me in the right direction of: How to define the stucture (if that is what I need for a key/value pair list) How to query at the application start-up and reuse the list properly The best way to do the string replacement

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• Caching instances in a jee web app

  - by SibzTer

  Hi, Consider the scenario of a typical webapp with JSFs on the front and ejb3, with Hibernate as JPA provider, talking to backend database such as mysql, etc. The main user actions are login and mostly CRUD operations (minus any D(elete) operations). And the App Server is GlassFish of course. Given this scenario, how and where all would one go about providing caching to improve performance? From what I have googled, I have seen that hibernate provides some sort of caching through different cache providers. Is there any sort of caching that can be provided for the jsf pages? How about session beans or entity beans on the ejb side of things? Also, I just read about memcached and was wondering if this was something to consider?

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• Algorithms for modern hardware?

  - by Jurily

  Once again, I find myself with a set of broken assumptions. The article itself is about a 10x performance gain by modifying a proven-optimal algorithm to account for virtual memory: What good is an O(log2(n)) algorithm if those operations cause page faults and slow disk operations? For most relevant datasets an O(n) or even an O(n^2) algorithm, which avoids page faults, will run circles around it. Are there more such algorithms around? Should we re-examine all those fundamental building blocks of our education? What else do I need to watch out for when writing my own?

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• Database structure for storing Bank-like accounts and transactions

  - by user1241320

  We're in the process of adding a bank-like sub-system to our own shop. We already have customers, so each will be given a sort of account and transactions of some kind will be possible (adding to the account or subtracting from it). So we at least need the account entity, the transaction one and operations will then have to recalculate overall balances. How would you structure your database to handle this? Is there any standard bank system have to use that I could mock? By the way, we're on mysql but will also look at some nosql solution for performance boost.

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• Which data structure for List of objects + datagrid wiev

  - by Martin

  Hi, I have to develop a code which will store a list of objects, as example below 101, value 11, value 12, value 13 ...etc 102, value 21, value 22, value 23 ...etc 103, value 31, value 32, value 33 ...etc 104, value 41, value 42, value 43 ...etc Now, the difficulty is, that first column is an identifier, and whole table should always be sorted by it. Easy access to each element is required. Additionally, list should be easily updated, and extended by adding element at the end as well as in front and still keep being sorted by first column. Finally, I would like to be able to display values of the above in datagridview. What is most important is a performance of the implementation, as rows will be updated many times per second, and datagridview should be able to display all changes immediately. I was thinking about creating class for the values, and then a Dictionary but encountered a problem with displaying values in gridview. What would be the most optimal way of implementing the code? Thanks in advance Martin

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• What is the differnce between "LINQ to Entities", "LINQ to SQL" and "LINQ to Dataset".

  - by Marcel

  Hi all, I'm working for quite a while now with LINQ. However, it remained still a bit of a mystery what are the real differences between the mentioned flavours of LINQ. The successful answer will contain a short differentiation between them. What is the main goal if it, what is the benefit, and is there a performance impact... P.S. I know that there are a lot of information sources out there, but I look for a kind of a "cheat sheet" which instructs a newbie where to head to for a specific goal.

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• Is ReaderWriterLockSlim.EnterUpgradeableReadLock() essentially the same as Monitor.Enter()?

  - by Neil Barnwell

  So I have a situation where I may have many, many reads and only the occasional write to a resource shared between multiple threads. A long time ago I read about ReaderWriterLock, and have read about ReaderWriterGate which attempts to mitigate the issue where many writes coming in trump reads and hurt performance. However, now I've become aware of ReaderWriterLockSlim... From the docs, I believe that there can only be one thread in "upgradeable mode" at any one time. In a situation where the only access I'm using is EnterUpgradeableReadLock() (which is appropriate for my scenario) then is there much difference to just sticking with lock(){}? Here's the excerpt: A thread that tries to enter upgradeable mode blocks if there is already a thread in upgradeable mode, if there are threads waiting to enter write mode, or if there is a single thread in write mode. Or, does the recursion policy make any difference to this?

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• Morfik - suitability for medium-scale web enterprise applications

  - by MaikB

  I'm investigating technologies with which to develop a medium-scale (up to 100 or 200 simultaneous users) database-driven web application, and someone suggested Morfik. However, outside of the Morfik company I can find practically zero community support - no active blogs, no tutorials, no videos, no books - and this is of some concern (especially when compared to C# / ASP.NET / nHibernate etc support). Deciding between Morfik (untried and not used widely AFAIK) and the other technologies I mentioned (tried, tested, used widely) is becoming a critical issue for my company. Has anyone had success using Morfik in these kind of circumstances? What kind of performance did you achieve?

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• How can I synchronize database access between a write-thread and a read-thread?

  - by Runcible

  My program has two threads: Main execution thread that handles user input and queues up database writes A utility thread that wakes up every second and flushes the writes to the database Inside the main thread, I occasionally need to make reads on the database. When this happens, performance is not important, but correctness is. (In a perfect world, I would be reading from a cache, not making a round-trip to the database - but let's put that aside for the sake of discussion.) How do I make sure that the main thread sees a correct / quiescent database? A standard mutex won't work, since I run the risk of having the main thread grab the mutex before the data gets flushed to the database. This would be a big race condition. What I really want is some sort of mutex that lets the main thread of execution proceed only AFTER the mutex has been grabbed and released once. Does such a thing exist? What's the best way to solve this problem?

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• Decoupling into DAL and BLL - my concerns.

  - by novice_man

  Hi, In many posts concerning this topic I come across very simple examples that do not answer my question. Let's say a have a document table and user table. In DAL written in ADO.NET i have a method to retries all documents for some criteria. Now I the UI I have a case where I need to show this list along with the names of the creator. Up to know I have it done with one method in DAL containig JOIN statement. However eveytime I have such a complex method i have to do custom mapping to some object that doesn't mark 1:1 to DB. Should it be put into another layer ? If so then I will have to resing from join query for iteration through results and querying each document author. . . which doen't make sense... (performance) what is the best approach for such scenarios ?

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• Scripting language to embed into a Java server application

  - by Alexey Kalmykov

  I want to make a business logic of server side Java application as a set of scripts. So I need from a scripting engine: Maximum Java interoperability (i.e. Spring framework) Script reloading and recompiling Easy DB access from scripting language Clear and simple syntax (some DSL capabilities would be nice to have), easy learning curve for non-hardcore developers Performance and stability I had some experience in the similar project with Rhino and it was pretty good. But I want to see if there is something better. Currently I'm looking into Groovy. JRuby and Jython are a bit more complex than I need for this task. Any other suggestion? What to take into consideration?

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• WCF Rest services for use with the repository pattern?

  - by mark smith

  Hi there, I am considering moving my Service Layer and my data layer (repository pattern) to a WCF Rest service. So basically i would have my software installed locally (WPF client) which would call the Service Layer that exists via a Rest Service... The service layer would then call my data layer using a WCF Rest Service also OR maybe just call it via the DLL assembly I was hoping to understand what the performance would be like. Currently I have my datalayer and servicelayer installed locally via DLL Assemblies locally on the pc. Also i presume the WCF REST services won't support method overloading hance the same name but with a different signature?? I would really appreciate any feedback anyone can give. Thanks

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• Flex 4.5 - to long build process

  - by Idob

  We are developing an app using flex 4.5. The app runs just fine (no performance issues at all) but it takes us forever to compile and build it. A minor change, like just add a comment or press enter in an mxml file and rebuild takes about 3 minutes. You just cant work that way. It is a large project with about 1300 files. We also use Parsley as IOC container and a beat of cairngorm navigation. We also use Maven (Flex mojos) but I am talking about a normal eclipse build (Ctrl + B). We separated some of the code to a different SWC and all of our graphics are stored in a different resource SWF. Please, Do you have any suggestions? Regards, Ido

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• Tips for a successful AppStore submission?

  - by Andrew Grant

  In a day or two I'll be ready to submit my iPhone app to the AppStore and I'm curious whether people who have gone through this process have any tips / suggestions for a smooth submission process. Here's things I've covered; No memory leaks Tested performance on an actual device Doesn't crash :) Using correct certificates / profile What I'm a little unsure about are how to configure the "Bundle Display Name" /"Bundle Identifier" and "Bundle Name" in info.plist. I understand the first is the text that's shown on the iPhone itself, but what about the last? Does this have to match Bundle Identifier? Are there any other things I should add to the info.plist? I've noticed that when built for Adhoc distribution my app does not have any author/title information in iTunes.

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