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  • Performance considerations of a large hard-coded array in the .cs file

    - by terence
    I'm writing some code where performance is important. In one part of it, I have to compare a large set of pre-computed data against dynamic values. Currently, I'm storing that pre-computed data in a giant array in the .cs file: Data[] data = { /* my data set */ }; The data set is about 90kb, or roughly 13k elements. I was wondering if there's any downside to doing this, as opposed to loading it in from an external file? I'm not entirely sure how C# works internally, so I just wanted to be aware of any performance issues I might encounter with this method.

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  • Help with optimising SQL query

    - by user566013
    Hi i need some help with this problem. I am working web application and for database i am using sqlite. Can someone help me with one query from databse which must be optimized == fast =) I have table x: ID | ID_DISH | ID_INGREDIENT 1 | 1 | 2 2 | 1 | 3 3 | 1 | 8 4 | 1 | 12 5 | 2 | 13 6 | 2 | 5 7 | 2 | 3 8 | 3 | 5 9 | 3 | 8 10| 3 | 2 .... ID_DISH is id of different dishes, ID_INGREDIENT is ingredient which dish is made of: so in my case dish with id 1 is made with ingredients with ids 2,3 In this table a have more then 15000 rows and my question is: i need query which will fetch rows where i can find ids of dishes ordered by count of ingreedients ASC which i haven added to my algoritem. examle: foo(2,4) will rows in this order: ID_DISH | count(stillMissing) 10 | 2 1 | 3 Dish with id 10 has ingredients with id 2 and 4 and hasn't got 2 more, then is

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  • MySQL Limiting a query to one consistent value

    - by Lucas Matos
    My current query returns a table like: +------------+ value1 | .... value1 | .... value2 | .... value3 | .... +------------+ I want: +------------+ value1 | .... value1 | .... +------------+ I want to only receive all rows with the first value. Normally I would do a WHERE clause if I knew that value, and I cannot use a LIMIT because each value has a different number of rows. Right now My query looks like "SELECT u.*, n.something, w.* FROM ... AS u, ... AS n, ... AS w WHERE u.id = n.id AND w.val = n.val AND u.desc LIKE '%GET REQUEST VARIABLE%';" This works great, except I get way too many rows and using PHP to do this ruins code portability and is superfluous. Thanks for reading

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  • C++ DWORD* to BYTE*

    - by NomeSkavinski
    My issue, i am trying to convert and array of dynamic memory of type DWORD to a BYTE. Fair enough i can for loop through this and convert the DWORD into a BYTE per entry. But is their a faster way to do this? to take a pointer to DWORD data and convert the whole piece of data into a pointer to BYTE data? such as using a memcpy operation? I feel this is not possible, im not requesting an answer just an experienced opinion on my approach, as i have tried testing both approaches but seem to fail getting to a solution on my second solution. Thanks for any input, again no answers just a point in the right direction. Nor is this a homework question, i felt that had to be mentioned.

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  • is there any faster way to parse than by walk each byte?

    - by uray
    is there any faster way to parse a text than by walk each byte of the text? I wonder if there is any special CPU (x86/x64) instruction for string operation that is used by string library, that somehow used to optimize the parsing routine. for example instruction like finding a token in a string that could be run by hardware instead of looping each byte until a token is found.

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  • How to speed-up a simple method? (possibily without changing interfaces or data structures)

    - by baol
    Hello. I have some data structures: all_unordered_mordered_m is a big vector containing all the strings I need (all different) ordered_m is a small vector containing the indexes of a subset of the strings (all different) in the former vector position_m maps the indexes of objects from the first vector to their position in the second one. The string_after(index, reverse) method returns the string referenced by ordered_m after all_unordered_m[index]. ordered_m is considered circular, and is explored in natural or reverse order depending on the second parameter. The code is something like the following: struct ordered_subset { // [...] std::vector<std::string>& all_unordered_m; // size = n >> 1 std::vector<size_t> ordered_m; // size << n std::map<size_t, size_t> position_m; // positions of strings in ordered_m const std::string& string_after(size_t index, bool reverse) const { size_t pos = position_m.find(index)->second; if(reverse) pos = (pos == 0 ? orderd_m.size() - 1 : pos - 1); else pos = (pos == ordered.size() - 1 ? 0 : pos + 1); return all_unordered_m[ordered_m[pos]]; } }; Given that: I do need all of the data-structures for other purposes; I cannot change them because I need to access the strings: by their id in the all_unordered_m; by their index inside the various ordered_m; I need to know the position of a string (identified by it's position in the first vector) inside ordered_m vector; I cannot change the string_after interface without changing most of the program. How can I speed up the string_after method that is called billions of times and is eating up about 10% of the execution time?

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  • How to custom query using ORM in Fuelphp?

    - by viyancs
    I have a problem when I want to query table using ORM ,example I have article table with field id,author,text. My code like this : // Single where $article = Model_Article::find()->where('id', 4); print_r($article); that't code will be fetch all field on table article, it's like select * from article where id = 4 Try Possibility $article = Model_Article::find(null, array('id','title'))->where('id', 3); the response is object(Orm\Query)#89 (14) { ["model":protected]=> string(10) "Model_Article" ["connection":protected]=> NULL ["view":protected]=> NULL ["alias":protected]=> string(2) "t0" ["relations":protected]=> array(0) { } ["joins":protected]=> array(0) { } ["select":protected]=> array(1) { ["t0_c0"]=> string(5) "t0.id" } ["limit":protected]=> NULL ["offset":protected]=> NULL ["rows_limit":protected]=> NULL ["rows_offset":protected]=> NULL ["where":protected]=> array(1) { [0]=> array(2) { [0]=> string(9) "and_where" [1]=> array(3) { [0]=> string(5) "t0.id" [1]=> string(1) "=" [2]=> int(3) } } } ["order_by":protected]=> array(0) { } ["values":protected]=> array(0) { } } that's is not return id or title field. but when i'm try by adding get_one() method $article = Model_Article::find(null, array('id','title'))->where('id', 3)->get_one(); id is return , but title is not and another field, i don't know why ? Reference ORM Discussion FuelPHP it's say ORM currently will be select all column, no plans to change that at the moment. My Goal I want to query in orm like this select id,owner from article where id = 4 it's will be return only id & owner, how i can get that using orm ?

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  • how to speed up code??

    - by kaushik
    i want to speed my code compilation..I have searched the internet and heard that psyco is a very tool to improve the speed.i have searched but could get a site for download. i have installed any additional libraries or modules till date in my python.. can psyco user,tell where we can download the psyco and its installation and using procedures?? i use windows vista and python 2.6 does this work on this ??

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  • Optimizing JS Array Search

    - by The.Anti.9
    I am working on a Browser-based media player which is written almost entirely in HTML 5 and JavaScript. The backend is written in PHP but it has one function which is to fill the playlist on the initial load. And the rest is all JS. There is a search bar that refines the playlist. I want it to refine as the person is typing, like most media players do. The only problem with this is that it is very slow and laggy as there are about 1000 songs in the whole program and there is likely to be more as time goes on. The original playlist load is an ajax call to a PHP page that returns the results as JSON. Each item has 4 attirbutes: artist album file url I then loop through each object and add it to an array called playlist. At the end of the looping a copy of playlist is created, backup. This is so that I can refine the playlist variable when people refine their search, but still repopulated it from backup without making another server request. The method refine() is called when the user types a key into the searchbox. It flushes playlist and searches through each property (not including url) of each object in the backup array for a match in the string. If there is a match in any of the properties, it appends the information to a table that displays the playlist, and adds it to the object to playlist for access by the actual player. Code for the refine() method: function refine() { $('#loadinggif').show(); $('#library').html("<table id='libtable'><tr><th>Artist</th><th>Album</th><th>File</th><th>&nbsp;</th></tr></table>"); playlist = []; for (var j = 0; j < backup.length; j++) { var sfile = new String(backup[j].file); var salbum = new String(backup[j].album); var sartist = new String(backup[j].artist); if (sfile.toLowerCase().search($('#search').val().toLowerCase()) !== -1 || salbum.toLowerCase().search($('#search').val().toLowerCase()) !== -1 || sartist.toLowerCase().search($('#search').val().toLowerCase()) !== -1) { playlist.push(backup[j]); num = playlist.length-1; $("<tr></tr>").html("<td>" + num + "</td><td>" + sartist + "</td><td>" + salbum + "</td><td>" + sfile + "</td><td><a href='#' onclick='setplay(" + num +");'>Play</a></td>").appendTo('#libtable'); } } $('#loadinggif').hide(); } As I said before, for the first couple of letters typed, this is very slow and laggy. I am looking for ways to refine this to make it much faster and more smooth.

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  • MySQL query with 2 COUNT() of other tables with where conditions

    - by Isern Palaus
    Hello, I've a table called sports that contains a list of list of sports, other called seasons that contains the seasons for a specific sport and competitions that have the competitions of a specific sport and season. I need one MySQL query to print the list of sports with how much seasons and competitions has each. My tables structure: sports +--------------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +--------------------+------------------+------+-----+---------+----------------+ | id | int(10) unsigned | NO | PRI | NULL | auto_increment | | name | varchar(32) | NO | | NULL | | | slug | varchar(45) | NO | | NULL | | | description | varchar(128) | NO | | NULL | | +--------------------+------------------+------+-----+---------+----------------+ seasons +--------------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +--------------------+------------------+------+-----+---------+----------------+ | id | int(10) unsigned | NO | PRI | NULL | auto_increment | | id_sport | int(10) unsigned | NO | MUL | NULL | | | name | varchar(32) | NO | | NULL | | | slug | varchar(32) | NO | | NULL | | +--------------------+------------------+------+-----+---------+----------------+ competitions +--------------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +--------------------+------------------+------+-----+---------+----------------+ | id | int(10) unsigned | NO | PRI | NULL | auto_increment | | id_season | int(10) unsigned | NO | MUL | NULL | | | name | varchar(32) | NO | | NULL | | | slug | varchar(64) | NO | | NULL | | | description | varchar(128) | YES | | NULL | | +--------------------+------------------+------+-----+---------+----------------+ The result of my query needs to contain: sports.*, total_seasons (SUM of seasons where seasons.id_sport=sports.id) and total_competitions (SUM of competitions where competitions.id_season=seasons.id AND seasons.id_sport=sports.id). Thank you in advance!

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  • Who owes who money optimisation problem

    - by Francis
    Say you have n people, each who owe each other money. In general it should be possible to reduce the amount of transactions that need to take place. i.e. if X owes Y £4 and Y owes X £8, then Y only needs to pay X £4 (1 transaction instead of 2). This becomes harder when X owes Y, but Y owes Z who owes X as well. I can see that you can easily calculate one particular cycle. It helps for me when I think of it as a fully connected graph, with the nodes being the amount each person owes. Problem seems to be NP-complete, but what kind of optimisation algorithm could I make, nevertheless, to reduce the total amount of transactions? Doesn't have to be that efficient, as N is quite small for me.

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  • What is the absolute fastest way to implement a concurrent queue with ONLY one consumer and one producer?

    - by JohnPristine
    java.util.concurrent.ConcurrentLinkedQueue comes to mind, but is it really optimum for this two-thread scenario? I am looking for the minimum latency possible on both sides (producer and consumer). If the queue is empty you can immediately return null AND if the queue is full you can immediately discard the entry you are offering. Does ConcurrentLinkedQueue use super fast and light locks (AtomicBoolean) ? Has anyone benchmarked ConcurrentLinkedQueue or knows about the ultimate fastest way of doing that? Additional Details: I imagine the queue should be a fair one, meaning the consumer should not make the consumer wait any longer than it needs (by front-running it) and vice-versa.

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  • Iterative Reduction to Null Matrix

    - by user1459032
    Here's the problem: I'm given a matrix like Input: 1 1 1 1 1 1 1 1 1 At each step, I need to find a "second" matrix of 1's and 0's with no two 1's on the same row or column. Then, I'll subtract the second matrix from the original matrix. I will repeat the process until I get a matrix with all 0's. Furthermore, I need to take the least possible number of steps. I need to print all the "second" matrices in O(n) time. In the above example I can get to the null matrix in 3 steps by subtracting these three matrices in order: Expected output: 1 0 0 0 1 0 0 0 1 0 0 1 1 0 0 0 1 0 0 1 0 0 0 1 1 0 0 I have coded an attempt, in which I am finding the first maximum value and creating the second matrices based on the index of that value. But for the above input I am getting 4 output matrices, which is wrong: My output: 1 0 0 0 1 0 0 0 1 0 1 0 1 0 0 0 0 0 0 0 1 0 0 0 1 0 0 0 0 0 0 0 1 0 1 0 My solution works for most of the test cases but fails for the one given above. Can someone give me some pointers on how to proceed, or find an algorithm that guarantees optimality? Test case that works: Input: 0 2 1 0 0 0 3 0 0 Output 0 1 0 0 0 0 1 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 1 0 0

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  • Speed up this query joining to a table multiple times

    - by Mongus Pong
    Hi, I have this query that (stripped right down) goes something like this : SELECT [Person_PrimaryContact].[LegalName], [Person_Manager].[LegalName], [Person_Owner].[LegalName], [Person_ProspectOwner].[LegalName], [Person_ProspectBDM].[LegalName], [Person_ProspectFE].[LegalName], [Person_Signatory].[LegalName] FROM [Cache] LEFT JOIN [dbo].[Person] AS [Person_Owner] WITH (NOLOCK) ON [Person_Owner].[PersonID] = [Cache].[ClientOwnerID] LEFT JOIN [dbo].[Person] AS [Person_Manager] WITH (NOLOCK) ON [Person_Manager].[PersonID] = [Cache].[ClientManagerID] LEFT JOIN [dbo].[Person] AS [Person_Signatory] WITH (NOLOCK) ON [Person_Signatory].[PersonID] = [Cache].[ClientSignatoryID] LEFT JOIN [dbo].[Person] AS [Person_PrimaryContact] WITH (NOLOCK) ON [Person_PrimaryContact].[PersonID] = [Cache].[PrimaryContactID] LEFT JOIN [dbo].[Person] AS [Person_ProspectOwner] WITH (NOLOCK) ON [Person_ProspectOwner].[PersonID] = [Cache].[ProspectOwnerID] LEFT JOIN [dbo].[Person] AS [Person_ProspectBDM] WITH (NOLOCK) ON [Person_ProspectBDM].[PersonID] = [Cache].[ProspectBDMID] LEFT JOIN [dbo].[Person] AS [Person_ProspectFE] WITH (NOLOCK) ON [Person_ProspectFE].[PersonID] = [Cache].[ProspectFEID] Person is a huge table and each join to it has a pretty significant hit in the execution plan. Is there anyway I can adjust this query so that I am only linking to it once, or at least get SQL Server to scan through it only once?

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  • get js file query param from inside it

    - by vsync
    I load this file with some query param like this: src='somefile.js?userId=123' I wrote the below function in 'somefile.js' file that reads the 'userId' query param but I feel this is not the best approach. Frankly, its quite ugly. Is there a better way? function getId(){ var scripts = document.getElementsByTagName('script'), script; for(var i in scripts){ if( scripts.hasOwnProperty(i) && scripts[i].src.indexOf('somefile.js') != -1 ) var script = scripts[i]; } var s = (script.getAttribute.length !== undefined) ? script.getAttribute('src') : script.getAttribute('src', 2); return getQueryParams('userId',s); };

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  • Preventing objects from being linked if they are not needed?

    - by Massif
    I have an ARM project that I'm building with make. I'm creating the list of object files to link based on the names of all of the .c and .cpp files in my source directory. However, I would like to exclude objects from being linked if they are never used. Will the linker exclude these objects from the .elf file automatically even if I include them in the list of objects to link? If not, is there a way to generate a list of only the objects that need to be linked?

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  • Optimizing Code

    - by Claudiu
    You are given a heap of code in your favorite language which combines to form a rather complicated application. It runs rather slowly, and your boss has asked you to optimize it. What are the steps you follow to most efficiently optimize the code? What strategies have you found to be unsuccessful when optimizing code? Re-writes: At what point do you decide to stop optimizing and say "This is as fast as it'll get without a complete re-write." In what cases would you advocate a simple complete re-write anyway? How would you go about designing it?

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  • Efficient SQL to count an occurrence in the latest X rows

    - by pulegium
    For example I have: create table a (i int); Assume there are 10k rows. I want to count 0's in the last 20 rows. Something like: select count(*) from (select i from a limit 20) where i = 0; Is that possible to make it more efficient? Like a single SQL statement or something? PS. DB is SQLite3 if that matters at all...

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  • Fastest way to compare Objects of type DateTime

    - by radbyx
    I made this. Is this the fastest way to find lastest DateTime of my collection of DateTimes? I'm wondering if there is a method for what i'm doing inside the foreach, but even if there is, I can't see how it can be faster than what i all ready got. List<StateLog> stateLogs = db.StateLog.Where(p => p.ProductID == product.ProductID).ToList(); DateTime lastTimeStamp = DateTime.MinValue; foreach (var stateLog in stateLogs) { int result = DateTime.Compare(lastTimeStamp, stateLog.TimeStamp); if (result < 0) lastTimeStamp = stateLog.TimeStamp; // sæt fordi timestamp er senere }

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  • Read large amount of data from file in Java

    - by Crozin
    Hello I've got text file that contains 1 000 002 numbers in following formation: 123 456 1 2 3 4 5 6 .... 999999 100000 Now I need to read that data and allocate it to int variables (the very first two numbers) and all the rest (1 000 000 numbers) to an array int[]. It's not a hard task, but - it's horrible slow. My first attempt was java.util.Scanner: Scanner stdin = new Scanner(new File("./path")); int n = stdin.nextInt(); int t = stdin.nextInt(); int array[] = new array[n]; for (int i = 0; i < n; i++) { array[i] = stdin.nextInt(); } It works as excepted but it takes about 7500 ms to execute. I need to fetch that data in up to several hundred of milliseconds. Then I tried java.io.BufferedReader: Using BufferedReader.readLine() and String.split() I got the same results in about 1700 ms, but it's still too many. How can I read that amount of data in less that 1 second? The final result should be equal to: int n = 123; int t = 456; int array[] = { 1, 2, 3, 4, ..., 999999, 100000 };

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  • How to make this JavaScript much faster?

    - by Ralph
    Still trying to answer this question, and I think I finally found a solution, but it runs too slow. var $div = $('<div>') .css({ 'border': '1px solid red', 'position': 'absolute', 'z-index': '65535' }) .appendTo('body'); $('body *').live('mousemove', function(e) { var topElement = null; $('body *').each(function() { if(this == $div[0]) return true; var $elem = $(this); var pos = $elem.offset(); var width = $elem.width(); var height = $elem.height(); if(e.pageX > pos.left && e.pageY > pos.top && e.pageX < (pos.left + width) && e.pageY < (pos.top + height)) { var zIndex = document.defaultView.getComputedStyle(this, null).getPropertyValue('z-index'); if(zIndex == 'auto') zIndex = $elem.parents().length; if(topElement == null || zIndex > topElement.zIndex) { topElement = { 'node': $elem, 'zIndex': zIndex }; } } }); if(topElement != null ) { var $elem = topElement.node; $div.offset($elem.offset()).width($elem.width()).height($elem.height()); } }); It basically loops through all the elements on the page and finds the top-most element beneath the cursor. Is there maybe some way I could use a quad-tree or something and segment the page so the loop runs faster?

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  • mysql PHP query question

    - by camran
    Ok, i have a problem here... I am sending values of drop down lists via ajax to this PHP file. Now I want to search a mysql database using these values, which I have managed to do, BUT, only if I set the values to something... Take a look: $query = "SELECT * FROM cars_db WHERE price BETWEEN '$cars_price_from' AND '$cars_price_to' AND year BETWEEN '$cars_year_from' AND '$cars_year_to' AND mileage BETWEEN '$cars_mileage_from' AND '$cars_mileage_to' AND gearbox = '$cars_gearbox' AND fuel = '$cars_fuel'"; now, what if the user doesnt select any "price_from" or "year_from"... The fields are only optional, so if the user doesnt enter any "price from" or "year from", then the user wants ALL cars to show... Do I have to write a query statement for each case or is there another way?

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