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• Writing a VM - well formed bytecode?

  - by David Titarenco

  Hi, I'm writing a virtual machine in C just for fun. Lame, I know, but luckily I'm on SO so hopefully no one will make fun :) I wrote a really quick'n'dirty VM that reads lines of (my own) ASM and does stuff. Right now, I only have 3 instructions: add, jmp, end. All is well and it's actually pretty cool being able to feed lines (doing it something like write_line(&prog[1], "jmp", regA, regB, 0); and then running the program: while (machine.code_pointer <= BOUNDS && DONE != true) { run_line(&prog[machine.cp]); } I'm using an opcode lookup table (which may not be efficient but it's elegant) in C and everything seems to be working OK. My question is more of a "best practices" question but I do think there's a correct answer to it. I'm making the VM able to read binary files (storing bytes in unsigned char[]) and execute bytecode. My question is: is it the VM's job to make sure the bytecode is well formed or is it just the compiler's job to make sure the binary file it spits out is well formed? I only ask this because what would happen if someone would edit a binary file and screw stuff up (delete arbitrary parts of it, etc). Clearly, the program would be buggy and probably not functional. Is this even the VM's problem? I'm sure that people much smarter than me have figured out solutions to these problems, I'm just curious what they are!

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• Point data structure for a sketching application

  - by bebraw

  I am currently developing a little sketching application based on HTML5 Canvas element. There is one particular problem I haven't yet managed to find a proper solution for. The idea is that the user will be able to manipulate existing stroke data (points) quite freely. This includes pushing point data around (ie. magnet tool) and manipulating it at whim otherwise (ie. altering color). Note that the current brush engine is able to shade by taking existing stroke data in count. It's a quick and dirty solution as it just iterates the points in the current stroke and checks them against a distance rule. Now the problem is how to do this in a nice manner. It is extremely important to be able to perform efficient queries that return all points within given canvas coordinate and radius. Other features, such as space usage, should be secondary to this. I don't mind doing some extra processing between strokes while the user is not painting. Any pointers are welcome. :)

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• Vertex Buffers in opengl

  - by JB

  I'm making a small 3d graphics game/demo for personal learning. I know d3d9 and quite a bit about d3d11 but little about opengl at the moment so I'm intending to abstract out the actual rendering of the graphics so that my scene graph and everything "above" it needs to know little about how to actually draw the graphics. I intend to make it work with d3d9 then add d3d11 support and finally opengl support. Just as a learning exercise to learn about 3d graphics and abstraction. I don't know much about opengl at this point though, and don't want my abstract interface to expose anything that isn't simple to implement in opengl. Specifically I'm looking at vertex buffers. In d3d they are essentially an array of structures, but looking at the opengl interface the equivalent seems to be vertex arrays. However these seem to be organised rather differently where you need a separate array for vertices, one for normals, one for texture coordinates etc and set the with glVertexPointer, glTexCoordPointer etc. I was hoping to be able to implement a VertexBuffer interface much like the the directx one but it looks like in d3d you have an array of structures and in opengl you need a separate array for each element which makes finding a common abstraction quite hard to make efficient. Is there any way to use opengl in a similar way to directx? Or any suggestions on how to come up with a higher level abstraction that will work efficiently with both systems?

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• Calling DI Container directly in method code (MVC Actions)

  - by fearofawhackplanet

  I'm playing with DI (using Unity). I've learned how to do Constructor and Property injection. I have a static container exposed through a property in my Global.asax file (MvcApplication class). I have a need for a number of different objects in my Controller. It doesn't seem right to inject these throught the constructor, partly because of the high quantity of them, and partly because they are only needed in some Actions methods. The question is, is there anything wrong with just calling my container directly from within the Action methods? public ActionResult Foo() { IBar bar = (Bar)MvcApplication.Container.Resolve(IBar); // ... Bar uses a default constructor, I'm not actually doing any // injection here, I'm just telling my conatiner to give me Bar // when I ask for IBar so I can hide the existence of the concrete // Bar from my Controller. } This seems the simplest and most efficient way of doing things, but I've never seen an example used in this way. Is there anything wrong with this? Am I missing the concept in some way?

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• Building asynchronous cache pattern with JSP

  - by merweirdo

  I have a JSP that will take some 8 minutes to render. The code logic itself can not be made more efficient (it will update often and be updated by basically a pointy haired boss). I tried wrapping it with a caching layer like <%@ taglib uri="/WEB-INF/classes/oscache.tld" prefix="oscache" %> <oscache:cache time="60"> <div class="pagecontent"> ..... my logic </div> </oscache:cache> This is nice until the 60 seconds is over. The next query after that blocks until the 8 minutes of rendering is done with again. I would need a way to build a pattern something like: If there is no version of the dynamic content in the cache run the actual logic (and populate the cache for subsequent requests) If there is a non-expired version of the dynamic content in the cache serve the output of the JSP logic from the cache If there is an expired version of the dynamic content in the cache serve the output of the JSP logic still from the cache AND run the JSP logic in the background so that the cache gets updated transparently to the user - avoiding the user have to wait for 8 minutes I found out that at least EHCache might be able to do some asynchronous cache updating but it did not sadly seem to apply to the JSP tags... Also I have to take in 10-20 parameters for the actual logic of the JSP and some of them should be used as a key for caching. Code example and/or pointers would be greatly appreciated. I do not frankly care if the solution provided is extremely ugly. I just want a simple 5 minute caching with asynchronous cache update taking into account some parameters as a key.

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• Reversing permutation of an array in Java efficiently

  - by HansDampf

  Okay, here is my problem: Im implementing an algorithm in Java and part of it will be following: The Question is to how to do what I will explain now in an efficient way. given: array a of length n integer array perm, which is a permutation of [1..n] now I want to shuffle the array a, using the order determined by array perm, i.e. a=[a,b,c,d], perm=[2,3,4,1] ------ shuffledA[b,c,d,a], I figured out I can do that by iterating over the array with: shuffledA[i]=a[perm[i-1]], (-1 because the permutation indexes in perm start with 1 not 0) Now I want to do some operations on shuffledA... And now I want to do the reverse the shuffle operation. This is where I am not sure how to do it. Note that a can hold an item more than once, i.e. a=[a,a,a,a] If that was not the case, I could iterate perm, and find the corresponding indexes to the values. Now I thought that using a Hashmap instead of the the perm array will help. But I am not sure if this is the best way to do.

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• Wrappers of primitive types in arraylist vs arrays

  - by ismail marmoush

  Hi, In "Core java 1" I've read CAUTION: An ArrayList is far less efficient than an int[] array because each value is separately wrapped inside an object. You would only want to use this construct for small collections when programmer convenience is more important than efficiency. But in my software I've already used Arraylist instead of normal arrays due to some requirements, though "The software is supposed to have high performance and after I've read the quoted text I started to panic!" one thing I can change is changing double variables to Double so as to prevent auto boxing and I don't know if that is worth it or not, in next sample algorithm public void multiply(final double val) { final int rows = getSize1(); final int cols = getSize2(); for (int i = 0; i < rows; i++) { for (int j = 0; j < cols; j++) { this.get(i).set(j, this.get(i).get(j) * val); } } } My question is does changing double to Double makes a difference ? or that's a micro optimizing that won't affect anything ? keep in mind I might be using large matrices.2nd Should I consider redesigning the whole program again ?

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• Help ! How do I get the total number rows from my SQL Server paging procedure ?

  - by The_AlienCoder

  Ok I have a table in my SQL Server database that stores comments. My desire is to be able to page though the records using [Back],[Next], page numbers & [Last] buttons in my data list. I figured the most efficient way was to use a stored procedure that only returns a certain number of rows within a particular range. Here is what I came up with @PageIndex INT, @PageSize INT, @postid int AS SET NOCOUNT ON begin WITH tmp AS ( SELECT comments.*, ROW_NUMBER() OVER (ORDER BY dateposted ASC) AS Row FROM comments WHERE (comments.postid = @postid)) SELECT tmp.* FROM tmp WHERE Row between (@PageIndex - 1) * @PageSize + 1 and @PageIndex*@PageSize end RETURN Now everything works fine and I have been able implement [Next] and [Back] buttons in my data list pager. Now I need the total number of all comments (not in the current page) so that I can implement my page numbers and the[Last] button on my pager. In other words I want to return the total number of rows in my first select statement i.e WITH tmp AS ( SELECT comments.*, ROW_NUMBER() OVER (ORDER BY dateposted ASC) AS Row FROM comments WHERE (comments.postid = @postid)) set @TotalRows = @@rowcount @@rowcount doesn't work and raises an error. I also cant get count.* to work either. Is there another way to get the total amount of rows or is my approach doomed.

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• Real time embeddable http server library required

  - by Howard May

  Having looked at several available http server libraries I have not yet found what I am looking for and am sure I can't be the first to have this set of requirements. I need a library which presents an API which is 'pipelined'. Pipelining is used to describe an HTTP feature where multiple HTTP requests can be sent across a TCP link at a time without waiting for a response. I want a similar feature on the library API where my application can receive all of those request without having to send a response (I will respond but want the ability to process multiple requests at a time to reduce the impact of internal latency). So the web server library will need to support the following flow 1) HTTP Client transmits http request 1 2) HTTP Client transmits http request 2 ... 3) Web Server Library receives request 1 and passes it to My Web Server App 4) My Web Server App receives request 1 and dispatches it to My System 5) Web Server receives request 2 and passes it to My Web Server App 6) My Web Server App receives request 2 and dispatches it to My System 7) My Web Server App receives response to request 1 from My System and passes it to Web Server 8) Web Server transmits HTTP response 1 to HTTP Client 9) My Web Server App receives response to request 2 from My System and passes it to Web Server 10) Web Server transmits HTTP response 2 to HTTP Client Hopefully this illustrates my requirement. There are two key points to recognise. Responses to the Web Server Library are asynchronous and there may be several HTTP requests passed to My Web Server App with responses outstanding. Additional requirements are Embeddable into an existing 'C' application Small footprint; I don't need all the functionality available in Apache etc. Efficient; will need to support thousands of requests a second Allows asynchronous responses to requests; their is a small latency to responses and given the required request throughput a synchronous architecture is not going to work for me. Support persistent TCP connections Support use with Server-Push Comet connections Open Source / GPL support for HTTPS Portable across linux, windows; preferably more. I will be very grateful for any recommendation Best Regards

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• one table is shared between several websites

  - by sami

  I have a static table that's shared by several websites. By static, I mean that the data is read but never updated by the websites. Currently, all websites are served from the same server but that may change. I want to minimize the need for creating/maintaining this table for each of the websites, so I thought about turning it to an xml file that's stored in a shared library that all websites have access to. The problem is I use an ORM and use forign key constraints to ensure integrity of the ids used from that table, so by removing that table out of the MySQL database into an XML file, will this affect the integrity of the ids coming from that table? My table looks like this <table name="entry"> <column name="id" type="INTEGER" primaryKey="true" autoIncrement="true" /> <column name="title" type="VARCHAR" size="500" required="true" /> </table> and I use it as a foreign key in other tables <table name="refer"> <column name="id" type="INTEGER" primaryKey="true" autoIncrement="true" /> <column name="linkto" type="INTEGER"/> <foreign-key foreignTable="entry"> <reference local="linkto" foreign="id" /> </foreign-key> </table> So I'm wondering if I remove that table out of the database, is there a way to retain that referential integrity? And of course are these any other efficient ways to do the same thing? I just don't want to have to repeat that table for several websites.

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• How to effectively color pixels in a BufferedImage?

  - by Ed Taylor

  I'm using the following pice of code to iterate over all pixels in an image and draw a red 1x1 square over the pixels that are within a certain RGB-tolerance. I guess there is a more efficient way to do this? Any ideas appreciated. (bi is a BufferedImage and g2 is a Graphics2D with its color set to Color.RED). Color targetColor = new Color(selectedRGB); for (int x = 0; x < bi.getWidth(); x++) { for (int y = 0; y < bi.getHeight(); y++) { Color pixelColor = new Color(bi.getRGB(x, y)); if (withinTolerance(pixelColor, targetColor)) { g2.drawRect(x, y, 1, 1); } } } private boolean withinTolerance(Color pixelColor, Color targetColor) { int pixelRed = pixelColor.getRed(); int pixelGreen = pixelColor.getGreen(); int pixelBlue = pixelColor.getBlue(); int targetRed = targetColor.getRed(); int targetGreen = targetColor.getGreen(); int targetBlue = targetColor.getBlue(); return (((pixelRed >= targetRed - tolRed) && (pixelRed <= targetRed + tolRed)) && ((pixelGreen >= targetGreen - tolGreen) && (pixelGreen <= targetGreen + tolGreen)) && ((pixelBlue >= targetBlue - tolBlue) && (pixelBlue <= targetBlue + tolBlue))); }

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• Total row count for pagination using JPA Criteria API

  - by ThinkFloyd

  I am implementing "Advanced Search" kind of functionality for an Entity in my system such that user can search that entity using multiple conditions(eq,ne,gt,lt,like etc) on attributes of this entity. I am using JPA's Criteria API to dynamically generate the Criteria query and then using setFirstResult() & setMaxResults() to support pagination. All was fine till this point but now I want to show total number of results on results grid but I did not see a straight forward way to get total count of Criteria query. This is how my code looks like: CriteriaBuilder builder = em.getCriteriaBuilder(); CriteriaQuery<Brand> cQuery = builder.createQuery(Brand.class); Root<Brand> from = cQuery.from(Brand.class); CriteriaQuery<Brand> select = cQuery.select(from); . . //Created many predicates and added to **Predicate[] pArray** . . select.where(pArray); // Added orderBy clause TypedQuery typedQuery = em.createQuery(select); typedQuery.setFirstResult(startIndex); typedQuery.setMaxResults(pageSize); List resultList = typedQuery.getResultList(); My result set could be big so I don't want to load my entities for count query, so tell me efficient way to get total count like rowCount() method on Criteria (I think its there in Hibernate's Criteria).

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• Need Help finding an appropriate task asignment algoritm for a collage project involving coordinatin

  - by Trif Mircea

  Hello. I am a long time lurker here and have found over time many answers regarding jquery and web development topics so I decided to ask a question of my own. This time I have to create a c++ project for collage which should help manage the workflow of a company providing all kinds of services through in the field teams. The ideas I have so far are: client-server application; the server is a dispatcher where all the orders from clients get and the clients are mobile devices (PDAs) each team in the field having one a order from a client is a task. Each task is made up of a series of subtasks. You have a database with estimations on how long a task should take to complete you also know what tasks or subtasks each team on the field can perform based on what kind of specialists made up the team (not going to complicate the problem by adding needed materials, it is considered that if a member of a team can perform a subtask he has the stuff needed) Now knowing these factors, what would a good task assignment algorithm be? The criteria is: how many tasks can a team do, how many tasks they have in the queue, it could also be location, how far away are they from the place but I don't think I can implement that.. It needs to be efficient and also to adapt quickly is the human dispatcher manually assigns a task. Any help or leads would be really appreciated. Also I'm not 100% sure in the idea so if you have another way you would go about creating such an application please share, even if it just a quick outline. I have to write a theoretical part too so even if the ideas are far more complex that what i outlined that would be ok ; I'd write those and implement what I can.

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• Return call from ggplot object

  - by aL3xa

  I've been using ggplot2 for a while now, and I can't find a way to get formula from ggplot object. Though I can get basic info with summary(<ggplot_object>), in order to get complete formula, usually I was combing up and down through .Rhistory file. And this becomes frustrating when you experiment with new graphs, especially when code gets a bit lengthy... so searching through history file isn't quite convenient way of doing this... Is there a more efficient way of doing this? Just an illustration: p <- qplot(data = mtcars, x = factor(cyl), geom = "bar", fill = factor(cyl)) + scale_fill_manual(name = "Cylinders", value = c("firebrick3", "gold2", "chartreuse3")) + stat_bin(aes(label = ..count..), vjust = -0.2, geom = "text", position = "identity") + xlab("# of cylinders") + ylab("Frequency") + opts(title = "Barplot: # of cylinders") I can get some basic info with summary: > summary(p) data: mpg, cyl, disp, hp, drat, wt, qsec, vs, am, gear, carb [32x11] mapping: fill = factor(cyl), x = factor(cyl) scales: fill faceting: facet_grid(. ~ ., FALSE) ----------------------------------- geom_bar: stat_bin: position_stack: (width = NULL, height = NULL) mapping: label = ..count.. geom_text: vjust = -0.2 stat_bin: width = 0.9, drop = TRUE, right = TRUE position_identity: (width = NULL, height = NULL) But I want to get code I typed in to get the graph. I reckon that I'm missing something essential here... it's seems impossible that there's no way to get call from ggplot object!

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• Perl - CodeGolf - Nested loops & SQL inserts

  - by CheeseConQueso

  I had to make a really small and simple script that would fill a table with string values according to these criteria: 2 characters long 1st character is always numeric (0-9) 2nd character is (0-9) but also includes "X" Values need to be inserted into a table on a database The program would execute: insert into table (code) values ('01'); insert into table (code) values ('02'); insert into table (code) values ('03'); insert into table (code) values ('04'); insert into table (code) values ('05'); insert into table (code) values ('06'); insert into table (code) values ('07'); insert into table (code) values ('08'); insert into table (code) values ('09'); insert into table (code) values ('0X'); And so on, until the total 110 values were inserted. My code (just to accomplish it, not to minimize and make efficient) was: use strict; use DBI; my ($db1,$sql,$sth,%dbattr); %dbattr=(ChopBlanks => 1,RaiseError => 0); $db1=DBI->connect('DBI:mysql:','','',\%dbattr); my @code; for(0..9) { $code[0]=$_; for(0..9) { $code[1]=$_; insert(@code); } insert($code[0],"X"); } sub insert { my $skip=0; foreach(@_) { if($skip==0) { $sql="insert into table (code) values ('".$_[0].$_[1]."');"; $sth=$db1->prepare($sql); $sth->execute(); $skip++; } else { $skip--; } } } exit; I'm just interested to see a really succinct & precise version of this logic.

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• SQL Server 2008 - Keyword search using table Join

  - by Aaron Wagner

  Ok, I created a Stored Procedure that, among other things, is searching 5 columns for a particular keyword. To accomplish this, I have the keywords parameter being split out by a function and returned as a table. Then I do a Left Join on that table, using a LIKE constraint. So, I had this working beautifully, and then all of the sudden it stops working. Now it is returning every row, instead of just the rows it needs. The other caveat, is that if the keyword parameter is empty, it should ignore it. Given what's below, is there A) a glaring mistake, or B) a more efficient way to approach this? Here is what I have currently: ALTER PROCEDURE [dbo].[usp_getOppsPaged] @startRowIndex int, @maximumRows int, @city varchar(100) = NULL, @state char(2) = NULL, @zip varchar(10) = NULL, @classification varchar(15) = NULL, @startDateMin date = NULL, @startDateMax date = NULL, @endDateMin date = NULL, @endDateMax date = NULL, @keywords varchar(400) = NULL AS BEGIN SET NOCOUNT ON; ;WITH Results_CTE AS ( SELECT opportunities.*, organizations.*, departments.dept_name, departments.dept_address, departments.dept_building_name, departments.dept_suite_num, departments.dept_city, departments.dept_state, departments.dept_zip, departments.dept_international_address, departments.dept_phone, departments.dept_website, departments.dept_gen_list, ROW_NUMBER() OVER (ORDER BY opp_id) AS RowNum FROM opportunities JOIN departments ON opportunities.dept_id = departments.dept_id JOIN organizations ON departments.org_id=organizations.org_id LEFT JOIN Split(',',@keywords) AS kw ON (title LIKE '%'+kw.s+'%' OR [description] LIKE '%'+kw.s+'%' OR tasks LIKE '%'+kw.s+'%' OR requirements LIKE '%'+kw.s+'%' OR comments LIKE '%'+kw.s+'%') WHERE ( (@city IS NOT NULL AND (city LIKE '%'+@city+'%' OR dept_city LIKE '%'+@city+'%' OR org_city LIKE '%'+@city+'%')) OR (@state IS NOT NULL AND ([state] = @state OR dept_state = @state OR org_state = @state)) OR (@zip IS NOT NULL AND (zip = @zip OR dept_zip = @zip OR org_zip = @zip)) OR (@classification IS NOT NULL AND (classification LIKE '%'+@classification+'%')) OR ((@startDateMin IS NOT NULL AND @startDateMax IS NOT NULL) AND ([start_date] BETWEEN @startDateMin AND @startDateMax)) OR ((@endDateMin IS NOT NULL AND @endDateMax IS NOT NULL) AND ([end_date] BETWEEN @endDateMin AND @endDateMax)) OR ( (@city IS NULL AND @state IS NULL AND @zip IS NULL AND @classification IS NULL AND @startDateMin IS NULL AND @startDateMax IS NULL AND @endDateMin IS NULL AND @endDateMin IS NULL) ) ) ) SELECT * FROM Results_CTE WHERE RowNum >= @startRowIndex AND RowNum < @startRowIndex + @maximumRows; END

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• Sorting by custom field and fetching whole tree from DB

  - by Niaxon

  Hello everyone, I am trying to do file browser in a tree form and have a problem to sort it somehow. I use PHP and MySQL for that. I've created mixed (nested set + adjacency) table 'element' with the following fields: element_id, left_key, right_key, level, parent_id, element_name, element_type (enum: 'folder','file'), element_size. Let's not discuss right now that it is better to move information about element (name, type, size) into other table. Function to scan specified directory and fill table work correctly. Noteworthy, i am adding elements to tree in specific order: folders first and then files. After that i can easily fetch and display whole table on the page using simple query: SELECT * FROM element WHERE 1=1 ORDER BY left_key With the result of that query and another function i can generate correct html code (<ul><li>... and so on). to display tree. Now back to the question (finally, huh?). I am struggling to add sorting functionality. For example i want to order my result by size. Here i need to keep in my mind whole hierarchy of tree and rule: folders first, files later. I believe i can do that by generating in PHP recursive query: SELECT * FROM element WHERE parent_id = {$parentId} ORDER BY element_type (so folders would be first), size (or name for example) asc/desc After that for each result which has type = 'folder' i will send another query to get it's content. Also it's possible to fetch whole tree by left_key and after that sort it in PHP as array but i guess that would be worse :) I wonder if there is better and more efficient way to do such a thing?

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• How to check if two records have a self-referencing relation?

  - by Machine

  Consider the following schema with users and their collegues (friends): Users User: columns: user_id: name: user_id as userId type: integer(8) unsigned: 1 primary: true autoincrement: true first_name: name: first_name as firstName type: string(45) notnull: true last_name: name: last_name as lastName type: string(45) notnull: true email: type: string(45) notnull: true unique: true relations: Collegues: class: User local: invitor foreign: invitee refClass: CollegueStatus equal: true onDelete: CASCADE onUpdate: CASCADE Join table: CollegueStatus: columns: invitor: type: integer(8) unsigned: 1 primary: true invitee: type: integer(8) unsigned: 1 primary: true status: type: enum(8) values: [pending, accepted, denied] default: pending notnull: true Now, let's say I two records, one for the user making a HTTP request (the logged in user), and one record for a user he wants to send a message to. I want to check if these users are collegues. Questions: Does Doctrine have any pre-build functionality to check if two records with with self-relations are related? If not, how would you write a method to check this? Where would you put said method? (In the User-class, UserTable-class etc) I could probably do something like this: public function (User $user1, User $user2) { // Ensure we load collegues if $user1 was fetched with DQL that // doesn't load this relation $collegues = $user1->get('Collegues'); $areCollegues = false; foreach($collegues as $collegue) { if($collegue['userId'] === $user2['userId']) { $areCollegues = true; break; } } return $areCollegues; } But this looks a neither efficient nor pretty. I just feel that it should be solved already for self-referencing relations to be nice to use.

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• Recursion in prepared statements

  - by Rob

  I've been using PDO and preparing all my statements primarily for security reasons. However, I have a part of my code that does execute the same statement many times with different parameters, and I thought this would be where the prepared statements really shine. But they actually break the code... The basic logic of the code is this. function someFunction($something) { global $pdo; $array = array(); static $handle = null; if (!$handle) { $handle = $pdo->prepare("A STATEMENT WITH :a_param"); } $handle->bindValue(":a_param", $something); if ($handle->execute()) { while ($row = $handle->fetch()) { $array[] = someFunction($row['blah']); } } return $array; } It looked fine to me, but it was missing out a lot of rows. Eventually I realised that the statement handle was being changed (executed with different param), which means the call to fetch in the while loop will only ever work once, then the function calls itself again, and the result set is changed. So I am wondering what's the best way of using PDO prepared statements in a recursive way. One way could be to use fetchAll(), but it says in the manual that has a substantial overhead. The whole point of this is to make it more efficient. The other thing I could do is not reuse a static handle, and instead make a new one every time. I believe that since the query string is the same, internally the MySQL driver will be using a prepared statement anyway, so there is just the small overhead of creating a new handle on each recursive call. Personally I think that defeats the point. Or is there some way of rewriting this?

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• How can I get this week's dates in Perl?

  - by ABach

  I have the following loop to calculate the dates of the current week and print them out. It works, but I am swimming in the amount of date/time possibilities in Perl and want to get your opinion on whether there is a better way. Here's the code I've written: #!/usr/bin/env perl use warnings; use strict; use DateTime; # Calculate numeric value of today and the # target day (Monday = 1, Sunday = 7); the # target, in this case, is Monday, since that's # when I want the week to start my $today_dt = DateTime->now; my $today = $today_dt->day_of_week; my $target = 1; # Create DateTime copies to act as the "bookends" # for the date range my ($start, $end) = ($today_dt->clone(), $today_dt->clone()); if ($today == $target) { # If today is the target, "start" is already set; # we simply need to set the end date $end->add( days => 6 ); } else { # Otherwise, we calculate the Monday preceeding today # and the Sunday following today my $delta = ($target - $today + 7) % 7; $start->add( days => $delta - 7 ); $end->add( days => $delta - 1 ); } # I clone the DateTime object again because, for some reason, # I'm wary of using $start directly... my $cur_date = $start->clone(); while ($cur_date <= $end) { my $date_ymd = $cur_date->ymd; print "$date_ymd\n"; $cur_date->add( days => 1 ); } As mentioned, this works, but is it the quickest or most efficient? I'm guessing that quickness and efficiency may not necessarily go together, but your feedback is very appreciated.

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• C++ - passing references to boost::shared_ptr

  - by abigagli

  If I have a function that needs to work with a shared_ptr, wouldn't it be more efficient to pass it a reference to it (so to avoid copying the shared_ptr object)? What are the possible bad side effects? I envision two possible cases: 1) inside the function a copy is made of the argument, like in ClassA::take_copy_of_sp(boost::shared_ptr<foo> &sp) { ... m_sp_member=sp; //This will copy the object, incrementing refcount ... } 2) inside the function the argument is only used, like in Class::only_work_with_sp(boost::shared_ptr<foo> &sp) //Again, no copy here { ... sp->do_something(); ... } I can't see in both cases a good reason to pass the boost::shared_ptr by value instead of by reference. Passing by value would only "temporarily" increment the reference count due to the copying, and then decrement it when exiting the function scope. Am I overlooking something? Andrea. EDIT: Just to clarify, after reading several answers : I perfectly agree on the premature-optimization concerns, and I alwasy try to first-profile-then-work-on-the-hotspots. My question was more from a purely technical code-point-of-view, if you know what I mean.

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• Good strategy for copying a "sliding window" of data from a table?

  - by chiborg

  I have a MySQL table from a third-party application that has millions of rows and only one index - the timestamp of each entry. Now I want to do some heavy self-joins and queries on the data using fields other than the timestamp. Doing the query on the original table would bring the database to a crawl, adding indexes to the table is not an option. Additionally, I only need entries that are newer than one week. My current strategy for doing the queries efficiently is to use a separate table (aux_table) that has the necessary indexes. My questions are: Is there another way to do the queries? and if not, How do I update the data in the indexed table efficiently? So far I have found two approaches for updating aux_table: Truncate aux_table and insert the desired data from the original table. Not very efficient because all the indexes must be re-crated. Check for the biggest timestamp in aux_table and insert all entries with a greater or equal timestamp from the original table. Occasionally drop older entries. Only copying entries with greater timestamp leads to dropped entries (because of entries with same timestamp that were inserted into the original table after the last update).

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• Efficiently sending protocol buffer messages with http on an android platform

  - by Ben Griffiths

  I'm trying to send messages generated by Google Protocol Buffer code via a simple HTTP scheme to a server. What I have currently have implemented is here (forgive the obvious incompletion...): HttpClient client = new DefaultHttpClient(); String url = "http://192.168.1.69:8888/sdroidmarshal"; HttpPost postRequest = new HttpPost(url); String proto = offers.build().toString(); List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(1); nameValuePairs.add(new BasicNameValuePair("sdroidmsg", proto)); postRequest.setEntity(new UrlEncodedFormEntity(nameValuePairs)); try { ResponseHandler<String> responseHandler = new BasicResponseHandler(); String responseBody = client.execute(postRequest, responseHandler); } catch (Throwable t) { } I'm not that experienced with communications over the internet and no more so with HTTP - while I do understand the basics... So my question, before I blindly develop the rest of the application around this, is whether or not this is particularly efficient? I ideally would like to keep messages small and I assume toString() adds some unnecessary formatting.

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• Web development scheme for staging and production servers using Git Push

  - by ServAce85

  I am using git to manage a dynamic website (PHP + MySQL) and I want to send my files from my localhost to my staging and development servers in the most efficient and hassle-free way. I am currently convinced that the best way for me to approach this problem is to use this git branching model to organize my local git repo. From there, I will use the release branches to push to my staging server for testing. Once I am happy that the release code works on the staging server, I can then merge with my master branch and push that to my production server. Pushing to Staging Server: As noted in many introductory git posts, I could run into problems pushing into a non-bare repo, so, as suggested in this response, I plan to push the release branch to a bare repo on the server and have a post-receive hook that clones the bare repo to a non-bare repo that also acts as the web-hosted directory. Pushing to Production Server: Here's my newest source of confusion... In the response that I cited above, it made me curious as to why @Paul states that it's a completely different story when pushing to a live, development server. I guess I don't see the problem. Would it be safe and hassle-free to follow the same steps as above, but for the master branch? Where are the potential pit-falls? Config Files: With respect to configuration files that are unique to each environment (.htaccess, config.php, etc), it seems simplest to .gitignore each of those files in their respective repos on their respective servers. Can you see anything immediately wrong with this? Better solutions? Accessing Data: Finally, as I initially stated, the site uses MySQL databases to store data. How would you suggest I access that data (for testing purposes) from the staging server and localhost? I realize that I may have asked way too many questions for a single post, but since they're all related to the best way to set up this development scheme, I thought it was necessary.

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• Which languages and techniques can I use to improve my coding practices?

  - by Danjah

  I've been offered the opportunity upskill through study, while at work which is great. My background I am mostly self-taught, but have worked with many excellent people over the years - both self-taught and fully educated, and on many decent projects. I have mild experience in Actionscript, I'm getting better every day with my Javascript, and my CSS is angled at best practice, but needs a bit of modernising. I'm a traditional interface developer, I'm not stupid and I like a challenge. My goal I need to start seeing ways of applying better logic, optimising code, refactoring, different styles of development (agile, others?), and.. well I need to try and start thinking like.. a more solid programmer. Its hard to describe, I have good solutions and I'm efficient - but I KNOW that there's a bunch I am missing. I am already employed with a solid career, but I feel the need to fill gaps. My question/s Are there a set of guiding principles you can recommend I focus on to improve the points above? Are there particular programming languages which I might focus on to get a broader overview? Do you think I should avoid particular styles of development, or even languages, while solidifying what might end up being part 'the basics' but hopefully 'advanced programming'? -- Sorry if this appears off topic or something but I figure you're probably some of the best people to ask.

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