optimization

问题 I have a table watchlist containing today almost 3Mil records. mysql> select count(*) from watchlist; +----------+ | count(*) | +----------+ | 2957994 | +----------+ It is used as a log to record product-page-views on a large e-commerce site (50,000+ products). It records the productID of the viewed product, the IP address and USER_AGENT of the viewer. And a timestamp of when it happens: mysql> show columns from watchlist; +-----------+--------------+------+-----+-------------------+-------+

问题 As known CPU is pipeline, and it works most efficiently if the sequence of commands independent from each other - this known as ILP (Instruction-Level Parallelism): http://en.wikipedia.org/wiki/Instruction-level_parallelism But is there a really working example which showing the benefits of ILP, at least syntetic example, for CPU x86_64 (but for the same amount of cmp / jne in both cases )? I will write the following example - add up all the elements of the array, but it does not show any

问题 At my page i have about 20 common html select widgets. For example: <select> <option>1</option> ... <option>3000</option> </select> that have 3000 or more elements in each one. So i have decided to convert them to ajax selects to load items dynamically when scrolling. How can i do this ?? 回答1: I have provided a set of working example of combo-box using jQuery UI selectmenu. I have used basic JSON source for ajax request, please work on this part yourself. $(".ajax-combo").selectmenu({ "width"

问题 hi, I'm developing an ASP.NET MVC website with Visual Studio 2010. The site is built and running from the local computer with the local built-in ASP.NET Development Server, the database is located somwhere on the net. The problem is that it is very slow to load or reload the page, take a look on this sceen : Link to image Any idea why this is that slow? BestRegards Edit : I have found out that this do only happen i Firefox, IE will return the page ALOT faster? 回答1: http://codewut.de/content

问题 hi, I'm developing an ASP.NET MVC website with Visual Studio 2010. The site is built and running from the local computer with the local built-in ASP.NET Development Server, the database is located somwhere on the net. The problem is that it is very slow to load or reload the page, take a look on this sceen : Link to image Any idea why this is that slow? BestRegards Edit : I have found out that this do only happen i Firefox, IE will return the page ALOT faster? 回答1: http://codewut.de/content

问题 Most of the hardware I uses supports SSE2 these days. On Windows and Linux, I have some code to test SSE support. I read somewhere that macOS has supported SSE for a long time, but I don't know the minimum version that can be enabled. The final binary will be copied to other macOS platforms so I cannot use -march=native like with GCC. If it is enabled by default on all builds, do I have to pass -msse or -msse2 flags when building my code ? Here is my compiler version: Apple LLVM version 6.0

问题 As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance. Closed 7 years ago . Is < cheaper (faster) than <= , and similarly, is > cheaper (faster) than >= ? Disclaimer: I know I could measure but that will be on

问题 I've an image over which I would like to compute a local histogram within a circular neighborhood. The size of the neighborhood is given by a radius . Although the code below does the job, it's computationally expensive. I run the profiler and the way I'm accessing to the pixels within the circular neighborhoods is already expensive. Is there any sort of improvement/optimization based maybe on vectorization? Or for instance, storing the neighborhoods as columns? I found a similar question in

问题 I have recently completely re-written a large project. In doing so, I have consolidated great number of random MySQL queries. I do remember that over the course of developing the previous codebase, I created indexes on a whim, and I'm sure there are a great number that aren't used anymore. Is there a way to monitor MySQL's index usage to determine which indexes are being used, and which ones are not? 回答1: I don't think this information is available in a stock MySQL installation. Percona makes

问题 Currently, I have the following c# code to extract a value out of text. If its XML, I want the value within it - otherwise, if its not XML, it can just return the text itself. String data = "..." try { return XElement.Parse(data).Value; } catch (System.Xml.XmlException) { return data; } I know exceptions are expensive in C#, so I was wondering if there was a better way to determine if the text I'm dealing with is xml or not? I thought of regex testing, but I dont' see that as a cheaper