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  • SQL Query That Should Return Least two days record

    - by Aryans
    I have a table "abc" where i store timestamp having multiple records let suppose 1334034000 Date:10-April-2012 1334126289 Date:11-April-2012 1334291399 Date:13-April-2012 I want to build a sql query where I can find at first attempt the records having last two day values and so second time the next two days . . . Example: Select *,dayofmonth(FROM_UNIXTIME(i_created)) from notes where dayofmonth(FROM_UNIXTIME(i_created)) > dayofmonth(FROM_UNIXTIME(i_created)) -2 order by dayofmonth(FROM_UNIXTIME(i_created)) this query returns all the records date wise but we need very most two days record. Please suggest accordingly. Thanks in advance

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  • Can a conforming C# compiler optimize away a local (but unused) variable if it is the only strong re

    - by stakx
    The title says it all, but let me explain: void Case_1() { var weakRef = new WeakReference(new object()); GC.Collect(); // <-- doesn't have to be an explicit call; just assume that // garbage collection would occur at this point. if (weakRef.IsAlive) ... } In this code example, I obviously have to plan for the possibility that the new'ed object is reclaimed by the garbage collector; therefore the if statement. (Note that I'm using weakRef for the sole purpose of checking if the new'ed object is still around.) void Case_2() { var unusedLocalVar = new object(); var weakRef = new WeakReference(unusedLocalVar); GC.Collect(); // <-- doesn't have to be an explicit call; just assume that // garbage collection would occur at this point. Debug.Assert(weakReferenceToUseless.IsAlive); } The main change in this code example from the previous one is that the new'ed object is strongly referenced by a local variable (unusedLocalVar). However, this variable is never used again after the weak reference (weakRef) has been created. Question: Is a conforming C# compiler allowed to optimize the first two lines of Case_2 into those of Case_1 if it sees that unusedLocalVar is only used in one place, namely as an argument to the WeakReference constructor? i.e. is there any possibility that the assertion in Case_2 could ever fail?

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  • Optimising ruby regexp -- lots of match groups

    - by Farcaller
    I'm working on a ruby baser lexer. To improve performance, I joined up all tokens' regexps into one big regexp with match group names. The resulting regexp looks like: /\A(?<__anonymous_-1038694222803470993>(?-mix:\n+))|\A(?<__anonymous_-1394418499721420065>(?-mix:\/\/[\A\n]*))|\A(?<__anonymous_3077187815313752157>(?-mix:include\s+"[\A"]+"))|\A(?<LET>(?-mix:let\s))|\A(?<IN>(?-mix:in\s))|\A(?<CLASS>(?-mix:class\s))|\A(?<DEF>(?-mix:def\s))|\A(?<DEFM>(?-mix:defm\s))|\A(?<MULTICLASS>(?-mix:multiclass\s))|\A(?<FUNCNAME>(?-mix:![a-zA-Z_][a-zA-Z0-9_]*))|\A(?<ID>(?-mix:[a-zA-Z_][a-zA-Z0-9_]*))|\A(?<STRING>(?-mix:"[\A"]*"))|\A(?<NUMBER>(?-mix:[0-9]+))/ I'm matching it to my string producing a MatchData where exactly one token is parsed: bigregex =~ "\n ... garbage" puts $~.inspect Which outputs #<MatchData "\n" __anonymous_-1038694222803470993:"\n" __anonymous_-1394418499721420065:nil __anonymous_3077187815313752157:nil LET:nil IN:nil CLASS:nil DEF:nil DEFM:nil MULTICLASS:nil FUNCNAME:nil ID:nil STRING:nil NUMBER:nil> So, the regex actually matched the "\n" part. Now, I need to figure the match group where it belongs (it's clearly visible from #inspect output that it's _anonymous-1038694222803470993, but I need to get it programmatically). I could not find any option other than iterating over #names: m.names.each do |n| if m[n] type = n.to_sym resolved_type = (n.start_with?('__anonymous_') ? nil : type) val = m[n] break end end which verifies that the match group did have a match. The problem here is that it's slow (I spend about 10% of time in the loop; also 8% grabbing the @input[@pos..-1] to make sure that \A works as expected to match start of string (I do not discard input, just shift the @pos in it). You can check the full code at GH repo. Any ideas on how to make it at least a bit faster? Is there any option to figure the "successful" match group easier?

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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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  • C++ performance, optimizing compiler, empty function in .cpp

    - by Dodo
    I've a very basic class, name it Basic, used in nearly all other files in a bigger project. In some cases, there needs to be debug output, but in release mode, this should not be enabled and be a NOOP. Currently there is a define in the header, which switches a makro on or off, depending on the setting. So this is definetely a NOOP, when switched off. I'm wondering, if I have the following code, if a compiler (MSVS / gcc) is able to optimize out the function call, so that it is again a NOOP. (By doing that, the switch could be in the .cpp and switching will be much faster, compile/link time wise). --Header-- void printDebug(const Basic* p); class Basic { Basic() { simpleSetupCode; // this should be a NOOP in release, // but constructor could be inlined printDebug(this); } }; --Source-- // PRINT_DEBUG defined somewhere else or here #if PRINT_DEBUG void printDebug(const Basic* p) { // Lengthy debug print } #else void printDebug(const Basic* p) {} #endif

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  • SimpleDB as Denormalized DB

    - by Max
    In an environment where you have a relational database which handles all business transactions is it a good idea to utilise SimpleDB for all data queries to have faster and more lightweight search? So the master data storage would be a relational DB which is "replicated"/"transformed" into SimpleDB to provide very fast read only queries since no JOINS and complicated subselects are needed.

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  • Please help me optimize my Python code

    - by Haidon
    Beginner here! Forgive me in advance for raising what is probably an incredibly simple problem. I've been trying to put together a Python script that runs multiple find-and-replace actions and a few similar things on a specified plain-text file. It works, but from a programming perspective I doubt it works well. How would I best go about optimizing the actions made upon the 'outtext' variable? At the moment it's basically doing a very similar thing four times over... import binascii import re import struct import sys infile = sys.argv[1] charenc = sys.argv[2] outFile=infile+'.tex' findreplace = [ ('TERM1', 'TERM2'), ('TERM3', 'TERM4'), ('TERM5', 'TERM6'), ] inF = open(infile,'rb') s=unicode(inF.read(),charenc) inF.close() # THIS IS VERY MESSY. for couple in findreplace: outtext=s.replace(couple[0],couple[1]) s=outtext for couple in findreplace: outtext=re.compile('Title: (.*)', re.I).sub(r'\\title'+ r'{\1}', s) s=outtext for couple in findreplace: outtext=re.compile('Author: (.*)', re.I).sub(r'\\author'+ r'{\1}', s) s=outtext for couple in findreplace: outtext=re.compile('Date: (.*)', re.I).sub(r'\\date'+ r'{\1}', s) s=outtext # END MESSY SECTION. outF = open(outFile,'wb') outF.write(outtext.encode('utf-8')) outF.close()

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  • PHP shell_exec() - Run directly, or perform a cron (bash/php) and include MySQL layer?

    - by Jimbo
    Sorry if the title is vague - I wasn't quite sure how to word it! What I'm Doing I'm running a Linux command to output data into a variable, parse the data, and output it as an array. Array values will be displayed on a page using PHP, and this PHP page output is requested via AJAX every 10 seconds so, in effect, the data will be retrieved and displayed/updated every 10 seconds. There could be as many as 10,000 characters being parsed on every request, although this is usually much lower. Alternative Idea I want to know if there is a better* alternative method of retrieving this data every 10 seconds, as multiple users (<10) will be having this command executed automatically for them. A cronjob running on the server could execute either bash or php (which is faster?) to grab the data and store it in a MySQL database. Then, any AJAX calls to the PHP output would return values in the MySQL database rather than making a direct call to execute server code every 10 seconds. Why? I know there are security concerns with running execs directly from PHP, and (I hope this isn't micro-optimisation) I'm worried about CPU usage on the server. The server is running a sempron processor. Yes, they do still exist. Having this only execute when the user is on the page (idea #1) means that the server isn't running code that doesn't need to be run. However, is this slow and insecure? Just in case the type of linux command may be of assistance in determining it's efficiency: shell_exec("transmission-remote $host:$port --auth $username:$password -l"); I'm hoping that there are differences in efficiency and level of security with the two methods I have outlined above, and that this isn't just micro-micro-optimisation. If there are alternative methods that are better*, I'd love to learn about these! :)

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  • Reduce Processing Time of accessing databse

    - by medma
    hello all, I m making an app which requires remote databse connection. I want the values in picker from database but when I click on button to invoke picker it takes some time to fetch the values and displaying. Is there any way to do it fast? and also is there any way to reduce the time of transition between 2 views? Thanx

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  • How can I write faster JavaScript?

    - by a paid nerd
    I'm writing an HTML5 canvas visualization. According to the Chrome Developer Tools profiler, 90% of the work is being done in (program), which I assume is the V8 interpreter at work calling functions and switching contexts and whatnot. Other than logic optimizations (e.g., only redrawing parts of the visualization that have changed), what can I do to optimize the CPU usage of my JavaScript? I'm willing to sacrifice some amount of readability and extensibility for performance. Is there a big list I'm missing because my Google skills suck? I have some ideas but I'm not sure if they're worth it: Limit function calls When possible, use arrays instead of objects and properties Use variables for math operation results as much as possible Cache common math operations such as Math.PI / 180 Use sin and cos approximation functions instead of Math.sin() and Math.cos() Reuse objects when passing around data instead of creating new ones Replace Math.abs() with ~~ Study jsperf.com until my eyes bleed Use a preprocessor on my JavaScript to do some of the above operations

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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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  • Need MYSQL query for finding lowest score per game player

    - by Chris Barnhill
    I have a game on Facebook called Rails Across Europe. I have a Best Scores page where I show the players with the best 20 scores, which in game terms refers to the lowest winning turn. The problem is that there are a small number of players who play frequently, and their scores dominate the page. I'd like to make the scores page open to more players. So I thought that I could display the single lowest winning turn for each player instead of displaying all of the lowest winning turns for all players. The problem is that the query for this eludes me. So I hope that one of you brilliant StackOverflow folks can help me with this. I have included the relevant MYSQL table schemas below. Here are the the table relationships: player_stats contains statistics for either a game in progress or a completed game. If a game is in progress, winning_turn is zero (which means that games with a winning_turn of zero should not be included in the query). player_stats has a game_player table id reference. game_player contains data describing games currently in progress. game_player has a player table id reference. player contains data describing a person who plays the game. Here's the query I'm currently using: 'SELECT p.fb_user_id, ps.winning_turn, gp.difficulty_level, c.name as city_name, g.name as goods_name, d.cost FROM game_player as gp, player as p, player_stats as ps, demand as d, city as c, goods as g WHERE p.status = "ACTIVE" AND gp.player_id = p.id AND ps.game_player_id = gp.id AND d.id = ps.highest_demand_id AND c.id = d.city_id AND g.id = d.goods_id AND ps.winning_turn > 0 ORDER BY ps.winning_turn ASC, d.cost DESC LIMIT '.$limit.';'; Here are the relevant table schemas: -- -- Table structure for table `player_stats` -- CREATE TABLE IF NOT EXISTS `player_stats` ( `id` int(11) NOT NULL auto_increment, `game_player_id` int(11) NOT NULL, `winning_turn` int(11) NOT NULL, `highest_demand_id` int(11) NOT NULL, PRIMARY KEY (`id`), KEY `game_player_id` (`game_player_id`,`highest_demand_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=3814 ; -- -- Table structure for table `game_player` -- CREATE TABLE IF NOT EXISTS `game_player` ( `id` int(10) unsigned NOT NULL auto_increment, `game_id` int(10) unsigned NOT NULL, `player_id` int(10) unsigned NOT NULL, `player_number` int(11) NOT NULL, `funds` int(10) unsigned NOT NULL, `turn` int(10) unsigned NOT NULL, `difficulty_level` enum('STANDARD','ADVANCED','MASTER','ULTIMATE') NOT NULL, `date_last_used` datetime NOT NULL, PRIMARY KEY (`id`), KEY `game_id` (`game_id`,`player_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=3814 ; -- -- Table structure for table `player` -- CREATE TABLE IF NOT EXISTS `player` ( `id` int(11) NOT NULL auto_increment, `fb_user_id` char(255) NOT NULL, `fb_proxied_email` text NOT NULL, `first_name` char(255) NOT NULL, `last_name` char(255) NOT NULL, `birthdate` date NOT NULL, `date_registered` datetime NOT NULL, `date_last_logged_in` datetime NOT NULL, `status` enum('ACTIVE','SUSPENDED','CLOSED') NOT NULL, PRIMARY KEY (`id`), KEY `fb_user_id` (`fb_user_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1646 ;

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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 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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  • 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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  • [PersistenceException: org.hibernate.exception.SQLGrammarException: could not execute query]

    - by doniyor
    i need help. i am trying to select from database thru sql statement in play framework, but it gives me error, i cannot figure out where the clue is. here is the code: @Transactional public static Users findByUsernameAndPassword(String username, String password){ String hash = DigestUtils.md5Hex(password); Query q = JPA.em().createNativeQuery("select * from USERS where" + "USERNAME=? and PASSWORD=?").setParameter(1, username).setParameter(2, password); List<Users> users = q.getResultList(); if(users.isEmpty()){ return null; } else{ return users.get(0); here is the eror message: [PersistenceException: org.hibernate.exception.SQLGrammarException: could not execute query] can someone help me please! any help i would appreciate! thanks

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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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  • Optimizing C++ Tree Generation

    - by cam
    Hi, I'm generating a Tic-Tac-Toe game tree (9 seconds after the first move), and I'm told it should take only a few milliseconds. So I'm trying to optimize it, I ran it through CodeAnalyst and these are the top 5 calls being made (I used bitsets to represent the Tic-Tac-Toe board): std::_Iterator_base::_Orphan_me std::bitset<9::test std::_Iterator_base::_Adopt std::bitset<9::reference::operator bool std::_Iterator_base::~_Iterator_base void BuildTreeToDepth(Node &nNode, const int& nextPlayer, int depth) { if (depth > 0) { //Calculate gameboard states int evalBoard = nNode.m_board.CalculateBoardState(); bool isFinished = nNode.m_board.isFinished(); if (isFinished || (nNode.m_board.isWinner() > 0)) { nNode.m_winCount = evalBoard; } else { Ticboard tBoard = nNode.m_board; do { int validMove = tBoard.FirstValidMove(); if (validMove != -1) { Node f; Ticboard tempBoard = nNode.m_board; tempBoard.Move(validMove, nextPlayer); tBoard.Move(validMove, nextPlayer); f.m_board = tempBoard; f.m_winCount = 0; f.m_Move = validMove; int currPlay = (nextPlayer == 1 ? 2 : 1); BuildTreeToDepth(f,currPlay, depth - 1); nNode.m_winCount += f.m_board.CalculateBoardState(); nNode.m_branches.push_back(f); } else { break; } }while(true); } } } Where should I be looking to optimize it? How should I optimize these 5 calls (I don't recognize them=.

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  • C++ Reserve Memory Space

    - by uray
    is there any way to reserve memory space to be used later by default Windows Memory Manager so that my application won't run out of memory if my program don't use space more than I have reserved at start of my program?

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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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  • 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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  • Filter Phrase Query

    - by alsuelo
    I try to filter a phrase to make a search in my website i've this query, this code working with one word but when i type wit more than one isn't working becuase the print is without spaces. $phrase = $this->getState($this->context.".filter_phrase"); printf("Original string: %s\n", $phrase); if(!empty($phrase)) { $escaped = $db->escape($phrase, true); printf("Escaped string: %s\n", $escaped); $quoted = $db->quote("%" . $escaped . "%" , false); $query->where ('a.title LIKE ' .$quoted); } Example i type king and the output is king , when i type the king the output is theking, i want to know if exist any way to conserve the blank spaces.

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