Все вопросы: [performance]
3 588 вопросов
network connection capability is not fully used, why?
I am using the following code to try to test whether network consumption (monitored from network tab of task manager) will increase if I increase the concurrent connection number (i.e. the ClientCount application configuration value). But I find even if I increase client count from 100 to 500, th...
MySQL performance: Single query using GROUP_CONCAT, or two separate queries?
I have a MySQL database in which each user has an account, and each account can have multiple permissions. My ultimate goal is to end up with the account's username, and a comma-delimited list of permissions ids. There are two ways I can accomplish this: SELECT a.username, GROUP_CONCAT(rp.perm...
using jQuery (put at the bottom of the page) on specific page
Because of performance purposes I put loading of jQuery scripts at the bottom of the page (just before the closing body tag). My question is how to enable page specific scripts? I don't want to put everything inside $(document).ready method (again because of performance purposes). Update: I'm u...
Efficient way to implement LinkedIn like "How you are connected to" feature?
LinkedIn has this cool feature in which while visiting some user's profile, LinkedIn prompts how you are connecting to that user through the network. Assuming that the visitor and the profile owner are two nodes of a graph where the nodes represent users and edge represents friendship, a simple...
Use PHP and MySQL DESCRIBE command to build checkbox and radio button menus dynamically
I'm making a data-entry web page in PHP that validates and parses data for entry into a MySQL database. There are more than 30 columns in the database that consist of MySQL SET or ENUM data. If you don't know much SQL, an ENUM datatype column can only hold one value from a collection of ENUM va...
efficient function to convert float/double to string
Right now, the only function that I am aware of is _snprintf_s like the following double dMyValue = <some value>; _snprintf_s(pszMyBuffer, sizeof(pszMyBuffer), 12, "%.10f", dMyValue);
ms access complicated query. querying last two entries by date for each ID. very slow
I have two tables. Widgets, which has information about each widget (Color, size, etc); each widget has a unique ID, WidgetID. The other table is Tests, and it contains information about multiple tests that were run on each widget. This table, therefore, has multiple rows for each WidgetID. It c...
PHP output buffering - sounds like a bad idea, is it?
Just want to pick the experts' brains on php output buffering. There are times when I've wanted to implement it for one reason or another, but have always managed to rearrange my code to get around it. I avoid using it because it sounds like it'll cost resources. I mean, if they can offer th...
Using OpenGL to accelerate 2D graphics
Me and my friend are trying to accelerate a 2D game with OpenGL. The video chipset is Radeon X1250 which seems to be underpowered and can display up to some 80 1366x768 full frames/s. Given that we are drawing many sprites on top of each other the performace drops dramatically under the 60 FPS we...
Shared pointers and the performance
I have been using shared pointers for soem time now, and I have performance issues in my program... So I'd like to know if shared pointers lead to performance decrease. If so, then how hard? Thanks alot. My program is multi-threaded, using std::tr1::shared_ptr
What tools are available to test SQL statement performance?
In the never-ending search for performance (and my own bludgeoning experience), I've learnt a few things that could drag down the performance of a SQL statement. Obsessive Compulsive Subqueries Disorder Doing crazy type conversions (and nest those into oblivion) Group By on aggregate functions o...
Advantages of ASP.Net compiled model?
I'm working with a PHP developer who is, shall we say, unhappy with .NET. His complaints include having to rebuild the web application solution for every test (though I pointed out that this is usually only necessary if a .cs file has been changed, not interface .aspx files), having to include ev...
Should updating an element in List<t> by index be quicker than using ArrayList index?</t>
I am running through some tests about using ArrayLists and List. Speed is very important in my app. I have tested creating 10000 records in each, finding an item by index and then updating that object for example: List[i] = newX; Using the arraylist seems much faster. Is that correct? UPDAT...
should I add a php APC to my server
A friend has recommended that I install php APC, claiming it will help php run faster and use less memory sounds promising but I'm a little nervous about adding it to my VPS server I have one small app that I've built using codeigniter, and several sites that use the popular slideshowpro photo ...
How to Get SQL Server Database performance Information?
Are there any standard queries that can be run that will show the performance of a SQL Server 2005 database? Note: I need to know the performance of every aspect of the database. EDIT: I am looking for a way to measure the time it takes for typical queries to execute. I am then going to apply i...
Why is the Android emulator so slow? How can we speed up the Android emulator?
I have got a 2.67 GHz Celeron processor, and 1.21 GB of RAM on a x86 Windows XP Professional machine. My understanding is that the Android Emulator should start fairly quickly on such a machine, but for me, it doesn't. I have followed all the instructions in setting up the IDE, SDKs, JDKs and s...
How to test application's startup time or performance
There is a free tool called PassMark AppTimer. But I think it's not quite fit for my needs. Windows provides a tool called xperf, is there a way to use it to test/benchmark application startup time?
How to automatically tune parameters of an algorithm?
Here's the setup: I have an algorithm that can succeed or fail. I want it to succeed with highest probability possible. Probability of success depends on some parameters (and some external circumstances): struct Parameters { float param1; float param2; float param3; float param4; // ....
Does SAS Proc SQL ever use an index when merging
Consider the following (admittedly long) example. The sample code creates two data sets, data one with "key" variables i,j,k and data two with key variables j,k and a "value" variable x. I'd like to merge these two data sets as efficiently as possible. Both of the data sets are indexed with res...
Performance of Arrays.asList
What is the cost of using Arrays.asList to convert static object arrays? Assuming that the object array has N items is it just an O(N) algorithm, where all of the items are copied by reference or is it merely a facade where the original array is put behind a List facade?
Optimum file buffer read size?
I am writing an application which needs to read fairly large files. I have always wondered what's the optimum size for the read buffer on a modern Windows XP computer. I googled and found many examples which had 1024 as the optimum size. Here is a snippet of what I mean: long pointer = 0; buff...
Sybase 15 performance issue
I am working with Sybase 15 in my application and there is performance issue related with nested joins. I have stored procedure which selects 2 columns from 2 tables and compares equalities of over 10 columns between this 2 tables. But when I run this stor. proc., the result takes 40 minutes. I a...
hardware environment for compilation performance
This is a rather general question .. What hardware setup is best for large C/C++ compile jobs, like a Linux kernel or Applications ? I remember reading a post by Joel Spolsky on experiments with solid state disks and stuff like that. Do I have to have rather more CPU power or more RAM or a f...
C++ and Java performance
this question is just speculative. I have the following implementation in C++: using namespace std; void testvector(int x) { vector<string> v; char aux[20]; int a = x * 2000; int z = a + 2000; string s("X-"); for (int i = a; i < z; i++) { sprintf(aux, "%d", i); v...
Profiling PHP app, 50% of time busy constructing classes -- is this OK?
I have a web application written in PHP. It uses MySQL for data storage. Today I decided to profile it to find bottlenecks in code and find which parts of it are running slower that the others. The usual stuff. I did a lot of work and now my page loads in less than 0.05 seconds on my desktop. Bu...
PHP MVC - How to design?
I'm relatively well versed in designing websites. I mostly go for LAMP where I already have a small "framework" of my own, that I use. In short, it separates the logic from the layout and I have basically one logic file to one or many layout files depending on what views are supported in the layo...
Is there a limit on the number of exceptions I should throw from a method?
Will declaring the function in this way have any implications on the performance? public init(){ try{ initApplication(); }catch(A1Exception){ }catch(A2Exception){ ... }catch(A5Exception){ } } private void initApplication() throws A1Exception, A2Exceptio...
Creating the most efficient fullscreen color-shifting gradient
For a project I'm working on I'm trying to create a Flash file with a constantly color-shifting gradient that fills up the entire browser window. For a better explanation please see the following link: GradientTest Example Don't worry about the moving balls, those are just there to challenge th...
What performance overhead do IoC containers involve?
Loose coupling is wonderful of course, but I have often wondered what overhead wiring up dynamically using an IoC container (for example Castle Windsor) has over a tightly coupled system? I know that a detailed answer would depend on what the IoC was being used for, but I'm really just trying to...
Ajax PageMethods Vs XMLHTTP
i have a case where when the user closes the browser window i have to set an Application Object to null...and for this i will use the JavaScript onbeforeUnload to do the server side work... so i wanted to know which is better XMLHTTP or an ajax PageMethod...which is faster..?? i have used both ...