Earlier this week I ask a question about filtering out duplicate values in sequence at run time. Had some good answers but the amount of data I was going over was to slow and not feasible. Currently in our database, event values are not filtered. Resulting in duplicate data values (with varying timestamps). We need to process that data ...
This SELECT * FROM SOME_TABLE WHERE SOME_FIELD LIKE '%some_value%'; is slower than this SELECT * FROM SOME_TABLE WHERE SOME_FIELD = 'some_value'; but what about this? SELECT * FROM SOME_TABLE WHERE SOME_FIELD LIKE 'some_value'; My testing indicates the second and third examples are exactly the same. If that's true, my question ...
When creating a class that has internal private methods, usually to reduce code duplication, that don't require the use of any instance fields, are there performance or memory advantages to declaring the method as static? Example: foreach (XmlElement element in xmlDoc.DocumentElement.SelectNodes("sample")) { string first = GetInner...
I've always struggled with how to best include classes into my php code. Pathing is usually an issue but a few minutes ago i found this question which dramatically helps that. Now I'm reading about __autoload and thinking that it could make the process of developing my applications much easier. The problem is i like to maintain folder st...
If you want a cryptographically strong random number in Java, you use SecureRandom. Unfortunately, SecureRandom can be very slow. If it uses /dev/random on Linux, it can block waiting for sufficient entropy to build up. How do you avoid the peformance penalty? Has anyone used Uncommon Maths as a solution to this problem? Can anybody co...
I am currently working in a project with developers working on three sites. One of the sites is in Delhi, India while the other two are in Europe. The communication between the European offices and the office in Delhi has poor bandwidth and quite bad latency, and a CVS update from there often takes 5-10 minutes even though only a few fil...
Or is it now the other way around? From what I've heard there are some areas in which C# proves to be faster than C++, but I've never had the guts to test it by myself. Thought any of you could explain these differences in detail or point me to the right place for information on this. ...
I would like to know when I should include external scripts or write them inline with the html code, in terms of performance and ease of maintenance. What is the general practice for this? Real-world-scenario - I have several html pages that need client-side form validation. For this I use a jQuery plugin that I include on all these pa...
I have a procedure with a lot of i := i +1; in it and I think inc(i); looks a lot better. Is there a performance difference or does the function call just get inlined by the compiler? I know this probably doesn't matter at all to my app, I'm just curious. EDIT: I did some gauging of the performance and found the difference to...
The maintenance problems that uninitialised locals cause (particularly pointers) will be obvious to anyone who has done a bit of c/c++ maintenance or enhancement, but I still see them and occasionally hear performance implications given as their justification. It's easy to demonstrate in c that redundant initialisation is optimised out:...
I have a C# interface with certain method parameters declared as object types. However, the actual type passed around can differ depending on the class implementing the interface: public interface IMyInterface { void MyMethod(object arg); } public class MyClass1 : IMyInterface { public void MyMethod(object arg) { My...
It sounds like Mozilla is having good luck improving JavaScript performance with TraceMonkey. See also Andreas Gal's paper on Trace Trees. Are these improvements available to other interpreters/compilers and if so, does this mean we'll see a cascade of improvements in other interpreted languages? ...
I'm on a team maintaining a .Net web app with a SQL Server 2005 back end. The system's been running a little slow in places lately, so after doing all the tuning kind of stuff we could think of (adding indexes, cleaning up really badly written stored procedures, etc.) I ran a typical workload through the Tuning Advisor - and it spit out...
I refactored a slow section of an application we inherited from another company to use an inner join instead of a subquery like where id in (select id from ... ) The refactored query runs about 100x faster. (~50 seconds to ~0.3) I expected an improvement, but can anyone explain why it was so drastic? The columns used in the where clau...
I came across this topic today while investigating something very strange. Doing certain things in our Flex app can cause the number of frames rendered to rocket, from 12fps to ~30fps: loaded animations start playing at high speed and the GUI starts to lock up. Since everything I've read on Flex/Flash hammers home the point "the frame r...
I have a loop that looks something like this: for(int i = 0; i < max; i++) { String myString = ...; float myNum = Float.parseFloat(myString); myFloats[i] = myNum; } This is the main content of a method whose sole purpose is to return the array of floats. I want this method to return null if there is an error, so I put the ...
Out of order execution in CPUs means that a CPU can reorder instructions to gain better performance and it means the CPU is having to do some very nifty bookkeeping and such. There are other processor approaches too, such as hyper-threading. Some fancy compilers understand the (un)interrelatedness of instructions to a limited extent, a...
I'm looking for books or online resources that go in detail over programming techniques for high performance computing using C++. ...
There appear to be several options available to programs that handle large numbers of socket connections (such as web services, p2p systems, etc). Spawn a separate thread to handle I/O for each socket. Use the select system call to multiplex the I/O into a single thread. Use the poll system call to multiplex the I/O (replacing the sele...
I've recently read the Yahoo manifesto Best Practices for Speeding Up Your Web Site. They recommend to put the javascript inclusion at the bottom of the HTML code when we can. But where exactly and when ? Should we put it before closing </html> or after ? And above all, when should we still put it in the <head> section ? ...