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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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• Connect to Oracle database on a different server from PHP

  - by macha

  Hello I have a database engine sitting on a remote server, while my webserver is present locally. I have worked pretty much with client-server architecture, where the server has both the webserver and the database engine. Now I need to connect to an Oracle database which is situated on a different server. Can anybody give me any suggestions?? I believe ODBC_CONNECT might not work. Do I use OCI8 drivers?? How would I connect to my database server. Also I would have a very high number of database calls going back and forth, so is it good to go with persistent connection or do I still use individual database calls?

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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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• Best computer-science universities in Europe?

  - by Tom

  I am in 11th grade and only one year left when I finish my school. I am sure I want to dedicate my life to programming. In my country the education's level is not so high as in Europe, so I want to emigrate and study not just for a diploma, but for knowledge too. So, what universities would you suggest me which has subject Computer-Science? I prefer web programming. Please do not delete this message though it is quite offtopic, but it's the best place for me to get suggestions from advanced programmers who have already finished their university. And I hope here comes also teenagers who can make the best decision choosing university. Thank you. Please read the whole my message before voting to close this thread, thanks.

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• Hopefully simple topic to spark some good opinions, Question is MySQL or SQL Server???

  - by magellings

  I'm beginning development of a website and a high priority is for it to be extremely optimized, quick responses, etc. There will ultimately end up being large amounts of rows in the main tables (millions), so scalability is also important. It will need to use a database on the back-end for data storage and my web hosting service supports either MySQL or Sql Server. This website will be developed with .NET ASP.NET MVC with NHibernate (hopefully it can run in medium trust mode, as that is a requirement of my web hosting and reflection requirements of NHibernate may be problematic, maybe someone has a comment on this too). I'd also prefer to use the database that will require the least attention in regards to management. I don't want to have to be a DBA here. :) I wanted to through this topic out to the public to see what the community thinks? So MySQL or Sql Server, generally, which one would be better to use?

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• Script Speed vs Memory Usage

  - by Doug Neiner

  I am working on an image generation script in PHP and have gotten it working two ways. One way is slow but uses a limited amount of memory, the second is much faster, but uses 6x the memory . There is no leakage in either script (as far as I can tell). In a limited benchmark, here is how they performed: -------------------------------------------- METHOD | TOTAL TIME | PEAK MEMORY | IMAGES -------------------------------------------- One | 65.626 | 540,036 | 200 Two | 20.207 | 3,269,600 | 200 -------------------------------------------- And here is the average of the previous numbers (if you don't want to do your own math): -------------------------------------------- METHOD | TOTAL TIME | PEAK MEMORY | IMAGES -------------------------------------------- One | 0.328 | 540,036 | 1 Two | 0.101 | 3,269,600 | 1 -------------------------------------------- Which method should I use and why? I anticipate this being used by a high volume of users, with each user making 10-20 requests to this script during a normal visit. I am leaning toward the faster method because though it uses more memory, it is for a 1/3 of the time and would reduce the number of concurrent requests.

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• Expert system for writing programs?

  - by aaa

  I am brainstorming an idea of developing a high level software to manipulate matrix algebra equations, tensor manipulations to be exact, to produce optimized C++ code using several criteria such as sizes of dimensions, available memory on the system, etc. Something which is similar in spirit to tensor contraction engine, TCE, but specifically oriented towards producing optimized rather than general code. The end result desired is software which is expert in producing parallel program in my domain. Does this sort of development fall on the category of expert systems? What other projects out there work in the same area of producing code given the constraints?

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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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• 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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• 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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• 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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• GPU Computing - # of GPUs supported

  - by TehTypoKing

  I currently have a desktop with 6 GPUs ( 3x HD 5970s ) in non-crossfire mode. Unfortunately, it seems that Windows 7 64bit only supports up to 4 GPUs. I have not been able to find a reliable source to deny or confirm this. If windows 7 has this limitation, is there a Linux flavor that supports more than 4 GPUs? In-case you are wondering, this is not for gaming but high-speed single precision computing. With this current setup ( if I can find 6gpu support ) I am looking to reach 13.8 Teraflops. Also, my motherboard does support 3 16x pci-xpress gen2 slots... and I have a 1500w powersupply plugged into a 20amp outlet. Windows is able to detect all 6 cores.. although, 2 of which displays the warning "Drivers failed to load". To recap: - Can windows support 6 GPUs? - If not, does Linux? Thank you.

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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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• Calculating terrain height in 3d-space

  - by Jonas B

  Hi I'm diving into 3d programming a bit and am currently learning by writing a procedural terrain generator that generates terrain based on a heightmap. I would also want to implement some physics and my first attempt at terrain collision was by simply checking the current position vs the heightmap. This however wont work well against small objects as you'd have to calculate the height by taking the heightdifference of the nearest vertices of the object and doing this every colision check is pretty slow. Beleive me I tried googling for it but there's simply so much crap and millions of blogs posting ripped-of newbie tutorials everywhere with basically no real information on the subject, I can't find anything that explains it or even names any generally used techniques. I'm not asking for code or a complete solution, but if anyone knows a particular technique good for calculating a high-res heightmap out of the already generated and smoothed terrain I would be very happy as I could look into it further when I know what I'm looking for. Thanks

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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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• 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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• Scrolling a Div programatically using say Javascript

  - by SARAVAN

  Hi I have a jqgrid which is embedded in a Div. I am deleting records from the grid and reloading the grid using grid.Trigger('reload'). The width of the grid is considerably high so it has a scroll bar. Now I scrolled through the end of the grid horizontally before deleting records. Each time I delete the records and reload the grid, the column headers and their values are slightly misaligned. When I move the scroll bar back to original position or just move the scroll bar slightly they are aligned properly. So I thought its better to move the scroll bar to its inital position when the grid reloads. How can a scroll bar be programatically moved using javascript. Or is there any other way to solve my problem?

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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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• How to pull a RANDOM and UNIQUE record from SQL via LINQ.

  - by Jeremy H

  Okay, I found lots of posts on SO about how to pull a RANDOM item from the database when using LINQ. There seems to be a couple of differnet ways to handle this. What I need to do though is pull a RANDOM item from the database that the user has not seen before. The data I am pulling from the database is very small. Is there any way I can just hit the database once for 1000 records and then randomly scroll through those? Should I put a cookie on the users system recording the IDs of which items they have seen, pull a random record, check to see if it is seen and if so, pull from the database again? That seems like performance issues just waiting to happen. I don't expect anyone to code it for me, I am just looking for concepts and pointing in the right direction of how I should go about this. Need more details? Just let me know!

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• Self-Configuring Classes W/ Command Line Args: Pattern or Anti-Pattern?

  - by dsimcha

  I've got a program where a lot of classes have really complicated configuration requirements. I've adopted the pattern of decentralizing the configuration and allowing each class to take and parse the command line/configuration file arguments in its c'tor and do whatever it needs with them. (These are very coarse-grained classes that are only instantiated a few times, so there is absolutely no performance issue here.) This avoids having to do shotgun surgery to plumb new options I add through all the levels they need to be passed through. It also avoids having to specify each configuration option in multiple places (where it's parsed and where it's used). What are some advantages/disadvantages of this style of programming? It seems to reduce separation of concerns in that every class is now doing configuration stuff, and to make programs less self-documenting because what parameters a class takes becomes less explicit. OTOH, it seems to increase encapsulation in that it makes each class more self-contained because no other part of the program needs to know exactly what configuration parameters a class might need.

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• Creating/compling .net data class within an application

  - by MrTelly

  Is there a pattern, Xml structure, architecture technique we can use to create simple data holder class code that we can deserialise to/from and do that at runtime? We're in the early design stage of a .Net project and one of our goals is to make the resulting system extensible through configuration without needing a developer. We need to support new sources of data, typcially delivered as Xml messages. Currently we convert/deserialise the messages into simple classes and then use an already existing language which can manipulate those classes as we need. That works well when you have a developer to map the Xml to simple class, create the class and then write the deserialisation, but it's not extensible for for an administrator. Our target user audience is high end DBA and/or network admin - people who can handle Xml but may not know C#.

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• MVC-3 User-Image Management - Best Practices

  - by Rob

  Hello Experts, Developing using MVC-3, Razor, C# Been searching around and cannot find advice I'm looking for. My site will contain user-uploaded images (possibly a high number). What is the best practice for managing these pictures (placement, breakdown into sub-folders, etc...)? Where do I place them that will prevent them from getting accidentally blown away if I republish my site periodically? If there are any good articles or blog posts, that would be helpful. Also, any advice/tips anyone wants to add would be great. Thanks for your time! Rob EDIT Also would like to know what people do to prevent hot linking.

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• Can any JavaScript library perform as well as the Cut The Rope JavaScript implementation?

  - by joe

  Now that the canvas tag is starting to get hardware execration [acceleration - thanks guys!] by many browsers, developing casual games in HTML5 is becoming more feasible. ZeptoLabs did a great job porting Cut The Rope to HTML5 for use as a Windows 8 Metro App. You can find some of the details here but they do not get into specifics. I was wondering if anyone knew if they used a library (such as Impact or Crafty) or if you need to write all custom and optimized JavaScript code in order to get this type of performance. Thanks!

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• Android: How to invalidate multiple parts of screen

  - by user342731

  I need to be able to selectively invalidate multiple (about 20) rectangles on the screen for performance reasons, so tried the following: Vector<Rect> myRects = new Vector<Rect>(); // ... add some Rects to myRects for (Rect r : myRects) { invalidate(r); } However this seems to invalidates a union of all the Rect's, forming one large rectangle which covers all of small ones I'm trying to invalidate. How can one invalidate multiple areas on the screen, and only those areas?

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