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• Generate random number from an arbitrary weighted list

  - by Fernando

  Here's what I need to do, I'll be doing this both in PHP and JavaScript. I have a list of numbers that will range from 1 to 300-500 (I haven't set the limit yet). I will be running a drawing were 10 numbers will be picked at random from the given range. Here's the tricky part: I want some numbers to be less likely to be drawn up. A small set of those 300-500 will be flagged as "lucky numbers". For example, out of 100 drawings, most numbers have equal chances of being drawn, except for a few, that will only be picked once every 30-50 drawings. Basically I need to artificially set the probability of certain numbers to be picked while maintaining an even distribution with the rest of the numbers. The only similar thing I've found so far is this question: Generate A Weighted Random Number, the problem being that my spec has considerably more numbers (up to 500) so the weights would get very small and supposedly this could be a problem with that solution (Rejection Sampling). I'm still trying it, though, but I wonder if there other solutions. Math is not my thing so I appreciate any input. Thanks.

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• VS2010 development web server does not use integrated-mode HTTP handlers/modules

  - by Domenic

  I am developing an ASP.NET MVC 2 web site, targeted for .NET Framework 4.0, using Visual Studio 2010. My web.config contains the following code: <system.webServer> <modules runAllManagedModulesForAllRequests="true"> <add name="XhtmlModule" type="DomenicDenicola.Website.XhtmlModule" /> </modules> <handlers> <add name="DotLess" type="dotless.Core.LessCssHttpHandler,dotless.Core" path="*.less" verb="*" /> </handlers> </system.webServer> When I use Build > Publish to put the web site on my local IIS7 instance, it works great. However, when I use Debug > Start Debugging, neither the HTTP handler nor module are executed on any requests. Strangely enough, when I put the handler and module <add /> tags back into <system.web /> under <httpHandlers /> and <httpModules />, they work. This seems to imply that the development web server is running in classic mode. How do I fix this?

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• Why does a sub-class class of a class have to be static in order to initialize the sub-class in the

  - by Alex

  So, the question is more or less as I wrote. I understand that it's probably not clear at all so I'll give an example. I have class Tree and in it there is the class Node, and the empty constructor of Tree is written: public class RBTree { private RBNode head; public RBTree(RBNode head,RBTree leftT,RBTree rightT){ this.head=head; this.head.leftT.head.father = head; this.head.rightT.head.father = head; } public RBTree(RBNode head){ this(head,new RBTree(),new RBTree()); } public RBTree(){ this(new RBNode(),null,null); } public class RBNode{ private int value; private boolean isBlack; private RBNode father; private RBTree leftT; private RBTree rightT; } } Eclipse gives me the error: "No enclosing instance of type RBTree is available due to some intermediate constructor invocation" for the "new RBTree()" in the empty constructor. However, if I change the RBNode to be a static class, there is no problem. So why is it working when the class is static. BTW, I found an easy solution for the cunstructor: public RBTree(){ this.head = new RBNode(); } So, I have no idea what is the problem in the first piece of code.

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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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• Practical non-image based CAPTCHA approaches?

  - by Jeff Atwood

  It looks like we'll be adding CAPTCHA support to Stack Overflow. This is necessary to prevent bots, spammers, and other malicious scripted activity. We only want human beings to post or edit things here! We'll be using a JavaScript (jQuery) CAPTCHA as a first line of defense: http://docs.jquery.com/Tutorials:Safer_Contact_Forms_Without_CAPTCHAs The advantage of this approach is that, for most people, the CAPTCHA won't ever be visible! However, for people with JavaScript disabled, we still need a fallback and this is where it gets tricky. I have written a traditional CAPTCHA control for ASP.NET which we can re-use. However, I'd prefer to go with something textual to avoid the overhead of creating all these images on the server with each request. I've seen things like.. ASCII text captcha: \/\/(_)\/\/ math puzzles: what is 7 minus 3 times 2? trivia questions: what tastes better, a toad or a popsicle? Maybe I'm just tilting at windmills here, but I'd like to have a less resource intensive, non-image based <noscript> compatible CAPTCHA if possible. Ideas?

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• What if you used the wrong language?

  - by HS

  A reply to another question made me remember a project from some years ago when it turned out that Java was not the right tool to use. I typically only learn a new language when I have a problem that it solves better than the ones I already know. [...] Then I write whatever program I wanted to learn that language for in the first place. [...] By the time I've gotten my target program written, I've usually got a decent handle on the language, not to mention any other features it has, and I've got other ideas to use it for. I did just that back then with Java, because the client thought it to be the right language to use (platform independent) and initial evaluation confirmed that. However, much later in the project there were some issue (can't really remember all the details by now). So, the project that started as a nice learning experience turned into a nightmare toward the end. I was at the brink of switching over to my trusted C++ and doing a complete rewrite. The client was not so much of a problem to convince back then, but my supervisor was strongly opposed because of all the work that already went into the Java version. In hindsight, he was right and the project was complete more or less with the intended features kind of working, but it was the project that I am least proud of by now. Long story short: what do you think, when is it too much and the switch to another technology is worthwhile? I personally would estimate the point of no return to be around 50% of the planned effort, but really want to know, if anyone has real experience with such a switch. And to answer the inevitable question: I do not really care, if the technology switched to is proven or another new thing. The latter would basically need more initial scrutiny based on the past experiences in the problematic project.

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• Ajax with Jsf 1.1 implementation

  - by Rohan Ved

  I am using JSF1.1 in that, have this code_ <%@ taglib uri="http://java.sun.com/jsf/html" prefix="h"%> <%@ taglib uri="http://java.sun.com/jsf/core" prefix="f"%> <%@ taglib uri="http://www.azureworlds.org" prefix="azure"%> <%@ taglib uri="http://myfaces.apache.org/tomahawk" prefix="x"%> <%@ taglib uri="http://www.asifqamar.com/jsf/asif" prefix="a"%> ... <x:selectOneMenu value="#{hotelBean.state}"> <f:selectItem itemLabel="Select One" itemValue="" /> <f:selectItem value="#{hotelBean.mapStates }" /> <x:ajax update="city" listener="#{hotelBean.handleCityChange}" /> </x:selectOneMenu> <h:outputText value="City* " /> <x:selectOneMenu id="city" value="#{hotelBean.city}"> <f:selectItem itemLabel="Select One" itemValue="" /> <f:selectItem value="#{hotelBean.mapCities }" /> </x:selectOneMenu> line x:ajax update="city" listener="#{hotelBean.handleCityChange}" is not working , i searched but got JSF1.1 not support for Ajax. then what can i do for this? and i have less knowledge of JS. Thanx

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• SQL Queries SELECT IN and SELECT NOT IN

  - by Sequenzia

  Does anyone know why the results of the following 2 queries do not add up to the results of the 3rd one? SELECT COUNT(leadID) FROM leads WHERE makeID NOT IN (SELECT uploadDataMapID FROM DG_App.dbo.uploadData WHERE uploadID = 3 AND uploadRowID = 1) AND modelID NOT IN (SELECT uploadDataMapID FROM DG_App.dbo.uploadData WHERE uploadID = 3 AND uploadRowID = 2) SELECT COUNT(leadID) FROM Leads WHERE makeID IN (SELECT uploadDataMapID FROM DG_App.dbo.uploadData WHERE uploadID = 3 AND uploadRowID = 1) OR modelID IN (SELECT uploadDataMapID FROM DG_App.dbo.uploadData WHERE uploadID = 3 AND uploadRowID = 2) SELECT COUNT(leadID) FROM Leads The first query is the count I need. The second one is to tell the user how many records were suppressed based on the contents of the DG_App.dbo.uploadData table. The third query is just a straight count of all the records. When I run these the results of query 1 + the results of query 2 comes up about 46K records less than the count of the entire table. I have played with grouping the WHERE statements with () but that did not change the counts at all. This is MSSQL Server 2012. Any input on this would be great. Thanks

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• Load SQL query result data into cache in advance

  - by Marc

  I have the following situation: .net 3.5 WinForm client app accessing SQL Server 2008 Some queries returning relatively big amount of data are used quite often by a form Users are using local SQL Express and restarting their machines at least daily Other users are working remotely over slow network connections The problem is that after a restart, the first time users open this form the queries are extremely slow and take more or less 15s on a fast machine to execute. Afterwards the same queries take only 3s. Of course this comes from the fact that no data is cached and must be loaded from disk first. My question: Would it be possible to force the loading of the required data in advance into SQL Server cache? Note My first idea was to execute the queries in a background worker when the application starts, so that when the user starts the form the queries will already be cached and execute fast directly. I however don't want to load the result of the queries over to the client as some users are working remotely or have otherwise slow networks. So I thought just executing the queries from a stored procedure and putting the results into temporary tables so that nothing would be returned. Turned out that some of the result sets are using dynamic columns so I couldn't create the corresponding temp tables and thus this isn't a solution. Do you happen to have any other idea?

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• stealing inside the move constructor

  - by FredOverflow

  During the implementation of the move constructor of a toy class, I noticed a pattern: array2D(array2D&& that) { data_ = that.data_; that.data_ = 0; height_ = that.height_; that.height_ = 0; width_ = that.width_; that.width_ = 0; size_ = that.size_; that.size_ = 0; } The pattern obviously being: member = that.member; that.member = 0; So I wrote a preprocessor macro to make stealing less verbose and error-prone: #define STEAL(member) member = that.member; that.member = 0; Now the implementation looks as following: array2D(array2D&& that) { STEAL(data_); STEAL(height_); STEAL(width_); STEAL(size_); } Are there any downsides to this? Is there a cleaner solution that does not require the preprocessor?

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• Automated Legal Processing

  - by Chris S

  Will it ever be possible to make legal systems quantifiable enough to process with computer algorithms? What technologies would have to be in place before this is possible? Are there any existing technologies that are already trying to accomplish this? Out of curiosity, I downloaded the text for laws in my local municipality, and tried applying some simple NLP tricks to extract rules from sentences. I had mixed results. Some sentences were very explicit (e.g. "Cars may not be left in the park overnight"), but other sentences seemed hopelessly vague (e.g. "The council's purpose is to ensure the well-being of the community"). I apologize if this is too open-ended a topic, but I've often wondered what society would look like if legal systems were based on less ambiguous language. Lawyers, and the legal process in general, are so expensive because they have to manually process a complex set of rules codified in ambiguous legal texts. If this system could be represented in software, this huge expense could potentially be eliminated, making the legal system more accessible for everyone.

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• Java 8 Stream, getting head and tail

  - by lyomi

  Java 8 introduced a Stream class that resembles Scala's Stream, a powerful lazy construct using which it is possible to do something like this very concisely: def from(n: Int): Stream[Int] = n #:: from(n+1) def sieve(s: Stream[Int]): Stream[Int] = { s.head #:: sieve(s.tail filter (_ % s.head != 0)) } val primes = sieve(from(2)) primes takeWhile(_ < 1000) print // prints all primes less than 1000 I wondered if it is possible to do this in Java 8, so I wrote something like this: IntStream from(int n) { return IntStream.iterate(n, m -> m + 1); } IntStream sieve(IntStream s) { int head = s.findFirst().getAsInt(); return IntStream.concat(IntStream.of(head), sieve(s.skip(1).filter(n -> n % head != 0))); } IntStream primes = sieve(from(2)); PrimitiveIterator.OfInt it = primes.iterator(); for (int prime = it.nextInt(); prime < 1000; prime = it.nextInt()) { System.out.println(prime); } Fairly simple, but it produces java.lang.IllegalStateException: stream has already been operated upon or closed because both findFirst() and skip() is a terminal operation on Stream which can be done only once. I don't really have to use up the stream twice since all I need is the first number in the stream and the rest as another stream, i.e. equivalent of Scala's Stream.head and Stream.tail. Is there a method in Java 8 Stream that I can achieve this? Thanks.

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• Using Reachability for Internet *or* local WiFi?

  - by randallmeadows

  I've searched SO for the answer to this question, and it's not really addressed, at least not to a point where I can make it work. I was originally only checking for Internet reachability, using: self.wwanReach = [Reachability reachabilityWithHostName:@"www.apple.com"]; [wwanReach startNotifer]; I now need to support a local WiFi connection (in the absence of reaching the Internet in general), and when I found +reachabilityForLocalWiFi, I also noticed there was +reachabilityForInternetConnection. I figured I could use these, instead of hard-coding "www.apple.com" in there, but alas, when I use self.wwanReach = [Reachability reachabilityForInternetConnection]; [wwanReach startNotifer]; self.wifiReach = [Reachability reachabilityForLocalWiFi]; [wifiReach startNotifer]; the reachability callback that I've set up "never" gets called, for values of "never" up to 10, 12, 15 minutes or so (which was as long as my patience lasted. (User's patience will be much less, I'm sure.) Switching back to +reachabilityWithHostName: works within seconds. I also tried each "pair" individually, in case there was an issue with two notifiers in progress simultaneously, but that made no difference. So: what is the appropriate way to determine reachability to either the Internet/WWAN or a local Wifi network (either one, or both)? [This particular use case is an iPhone or iPad connecting to a Mac mini computer-to-computer network; I'm sure other situations apply.]

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• PHP Socket Server vs node.js: Web Chat

  - by Eliasdx

  I want to program a HTTP WebChat using long-held HTTP requests (Comet), ajax and websockets (depending on the browser used). Userdatabase is in mysql. Chat is written in PHP except maybe the chat stream itself which could also be written in javascript (node.js): I don't want to start a php process per user as there is no good way to send the chat messages between these php childs. So I thought about writing an own socket server in either PHP or node.js which should be able to handle more then 1000 connections (chat users). As a purely web developer (php) I'm not much familiar with sockets as I usually let web server care about connections. The chat messages won't be saved on disk nor in mysql but in RAM as an array or object for best speed. As far as I know there is no way to handle multiple connections at the same time in a single php process (socket server), however you can accept a great amount of socket connections and process them successive in a loop (read and write; incoming message - write to all socket connections). The problem is that there will most-likely be a lag with ~1000 users and mysql operations could slow the whole thing down which will then affect all users. My question is: Can node.js handle a socket server with better performance? Node.js is event-based but I'm not sure if it can process multiple events at the same time (wouldn't that need multi-threading?) or if there is just an event queue. With an event queue it would be just like php: process user after user. I could also spawn a php process per chat room (much less users) but afaik there are singlethreaded IRC servers which are also capable to handle thousands of users. (written in c++ or whatever) so maybe it's also possible in php. I would prefer PHP over Node.js because then the project would be php-only and not a mixture of programming languages. However if Node can process connections simultaneously I'd probably choose it.

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• How to emulate mod_rewrite in PHP

  - by Tyler Crompton

  I have a few URLs that I want to map to certain files via PHP. Currently, I am just using mod_rewrite in Apache. However, my application is getting too large for the rewriting to be done with regular expressions. So I created a file router.php that does the rewriting. I understand to do a redirect I could just send the Location: header. However, I don't always want to do a redirect. For example, I may want /api/item/ to map to the file /herp/derp.php relative to the document root. I need to preserve the HTTP method as well. "No problem," I thought. I made my .htaccess have the following snippet. RewriteEngine On RewriteRule ^api/item/$ /cgi-bin/router.php [L] And my router.php file looks as follows: <?php $uri = parse_url($_SERVER['REQUEST_URI']); $query = isset($uri['query']) ? $uri['query'] ? array(); // some code that modifies the query require_once "{$_SERVER['DOCUMENT_ROOT']}/herp/derp.php?" . http_build_query($query); ?> However, this doesn't work, because the OS is looking for a file named derp.php?some=query. How can I simulate a rewrite rule such as RewriteRule ^api/item/$ /herp/derp/ [L] in PHP. In other words, how do I tell the server to process a different URL than requested and preserve the query and HTTP method without causing a redirect? Note: Using variables set in router.php is less than desirable and is bad structure since it's only supposed to be responsible for handling URLs. I am open to using a light-weight third party solution.

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• DataGridView with row-specific DataGridViewComboBoxColumn contents

  - by XXXXX

  So I have something like the following data structure (constructors omitted) class Child { public string Name { get; set; } public int Age { get; set; } } class Parent { public string Name { get; set; } public List <Child> Children { get; private set; } // never null; list never empty public Child FavoriteChild { get; set; } // never null; always a reference to a Child in Children } List < Parent > Parents; What I want to do is show a DataGridView where each row is a Parent from Parent list. Each row should have two columns: a text box showing the parent's name and a DataGridViewComboBoxColumn containing that parent's children, from which the user can select the parent's favorite child. I suppose I could do the whole thing manually, but I'd like to do all this with more-or-less standard Data Binding. It's easy enough to bind the DataGridView to the list of parents, and easy enough to bind the selected child to the FavoriteChild property. The part that's giving me difficulty is that it looks like the Combo Box column wants to bind to one data source for all the combo-box's contents on all rows. I'd like each instance of the combo box to bind to the list of each parent's children. I'm fairly new to C#/Windows Forms, so I may well be missing something obvious. Or it could be that "you can't get there from here." It's not too tough to make a separate list of all the children and filter it by parent; I'm looking into that possibility right now. Is this feasible, or is there a better way?

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• IF-block brackets: best practice

  - by MasterPeter

  I am preparing a short tutorial for level 1 uni students learning JavaScript basics. The task is to validate a phone number. The number must not contain non-digits and must be 14 digits long or less. The following code excerpt is what I came up with and I would like to make it as readable as possible. if ( //set of rules for invalid phone number phoneNumber.length == 0 //empty || phoneNumber.length > 14 //too long || /\D/.test(phoneNumber) //contains non-digits ) { setMessageText(invalid); } else { setMessageText(valid); } A simple question I can not quite answer myself and would like to hear your opinions on: How to position the surrounding (outermost) brackets? It's hard to see the difference between a normal and a curly bracket. Do you usually put the last ) on the same line as the last condition? Do you keep the first opening ( on a line by itself? Do you wrap each individual sub-condition in brackets too? Do you align horizontally the first ( with the last ), or do you place the last ) in the same column as the if? Do you keep ) { on a separate line or you place the last ) on the same line with the last sub-condition and then place the opening { on a new line? Or do you just put the ) { on the same line as the last sub-condition? Community wiki.

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• ORA- 01157 / Cant connect to database

  - by Tom

  Hi everyone, this is a follow up from this question. Let me start by saying that i am NOT a DBA, so i'm really really lost with this. A few weeks ago, we lost contact with one of our SID'S. All the other services are working, but this one in particular is not. What we got was this message when trying to connect ORA-01033: ORACLE initialization or shutdown in progress An attempt to alter database open ended up in ORA-01157: cannot identify/lock data file 6 - see DBWR trace file ORA-01110: data file 6: '/u01/app/oracle/oradata/xxx/xxx_data.dbf' I tried to shutdown / restart the database, but got this message. Total System Global Area 566231040 bytes Fixed Size 1220604 bytes Variable Size 117440516 bytes Database Buffers 444596224 bytes Redo Buffers 2973696 bytes Database mounted. ORA-01157: cannot identify/lock data file 6 - see DBWR trace file ORA-01110: data file 6: '/u01/app/oracle/oradata/xxx/xxx_data.dbf' When all continued the same, I erased the dbf files (rm xxx_data.dbf xxx_index.dbf), and recreated them using touch xxx_data.dbf. I also tried to recreate the tablespaces using `CREATE TABLESPACE DATA DATAFILE XXX_DATA.DBF` and got Database not open As I said, i don't know how bad this is, or how far i'm from gaining access to my database (well, to this SID at least, the others are working). I would imagine that a last resource would be to throw everything away, and recreating it, but I don't know how to, and I was hoping there's a less destructive solution. Any help will be greatly appreciated . Thanks in advance.

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• Page content layout issues

  - by Prupel

  I'm designing a theme for a blog and I'm having some trouble trying to get a layout working. Here's an image of what I want. This diagram represents the individual posts and not the website itself, so it will be contained in a box of it's own, lets call it .container. Also the purple and green are in another box, let's call it .content. The other elements will be called by their color for now. so here's more or less what the CSS looks like: .container { display:block; margin:0 25px; } .gray, .blue, .content { display:block; width:100%; } .purple { display:inline-block; width:125px; height:100%; text-align:center; } .green { display:inline-block; } That's all there is at the moment. I tried float but that made no effect. What's happening is something like this. Here's a few more things you should know: .container's width is NOT set it is auto .purple and .green don't necessarily need to be the same size as long as .green doesn't go to that side. .purple CAN have a set height .green is where the meat is, that's where the actual post goes, keep that in mind. I don't think tables will help, the problem is inside .content.

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• How can I split my conkeror-rc config over multiple files?

  - by Ryan Thompson

  Short version: can you help me fill in this code? var conkeror_settings_dir = ".conkeror.mozdev.org/settings"; function load_all_js_files_in_dir (dir) { var full_path = get_home_directory().appendRelativePath(dir); // YOUR CODE HERE } load_all_js_files_in_dir(conkeror_settings_dir); Background I'm trying out Conkeror for web browsing. It's an emacs-like browser running on Mozilla's rendering engine, using javascript as configuration language (filling the role that elisp plays for emacs). In my emacs config, I have split my customizations into a series of files, where each file is a single unit of related options (for example, all my perl-related settings might be in perl-settings.el. All these settings files are loaded automatically by a function in my .emacs that simply loads every elisp file under my "settings" directory. I am looking to structure my Conkeror config in the same way, with my main conkeror-rc file basically being a stub that loads all the js files under a certain directory relative to my home directory. Unfortunately, I am much less literate in javascript than I am in elisp, so I don't even know how to "source" a file.

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• Looking to reimplement build toolchain from bash/grep/sed/awk/(auto)make/configure to something more

  - by wash

  I currently maintain a few boxes that house a loosely related cornucopia of coding projects, databases and repositories (ranging from a homebrew *nix distro to my class notes), maintained by myself and a few equally pasty-skinned nerdy friends (all of said cornucopia is stored in SVN). The vast majority of our code is in C/C++/assembly (a few utilities are in python/perl/php, we're not big java fans), compiled in gcc. Our build toolchain typically consists of a hodgepodge of make, bash, grep, sed and awk. Recent discovery of a Makefile nearly as long as the program it builds (as well as everyone's general anxiety with my cryptic sed and awking) has motivated me to seek a less painful build system. Currently, the strongest candidate I've come across is Boost Build/Bjam as a replacement for GNU make and python as a replacement for our build-related bash scripts. Are there any other C/C++/asm build systems out there worth looking into? I've browsed through a number of make alternatives, but I haven't found any that are developed by names I know aside from Boost's. (I should note that an ability to easily extract information from svn commandline tools such as svnversion is important, as well as enough flexibility to configure for builds of asm projects as easily as c/c++ projects)

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• How to control virtual memory management in linux?

  - by chmike

  I'm writing a program that uses an mmap file to hold a huge buffer organized as an array of 64 MB blocks. The blocks are used to aggregate data received from different hosts through the network. As a consequence the total data size written in each block is not known in advance. Most of the time it is only 2MB but in some cases it can be up to 20MB or more. The data doesn't stay long in the buffer. 90% is deleted after less than a second and the rest is transmitted to another host. I would like to know if there is a way to tell the virtual memory manager that ram pages are not dirty anymore when data is deleted. Should I use mmap and munmap when a block is used and released to control the virtual memory ? What would be the overhead of doing this ? Also, some colleagues expressed concerns about the performance impact of allocating such a big mmap space. I expect it to behave like a swap file so that only dirty pages are to be considered.

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• Multiple inequality conditions (range queries) in NoSQL

  - by pableu

  Hi, I have an application where I'd like to use a NoSQL database, but I still want to do range queries over two different properties, for example select all entries between times T1 and T2 where the noiselevel is smaller than X. On the other hand, I would like to use a NoSQL/Key-Value store because my data is very sparse and diverse, and I do not want to create new tables for every new datatype that I might come across. I know that you cannot use multiple inequality filters for the Google Datastore (source). I also know that this feature is coming (according to this). I know that this is also not possible in CouchDB (source). I think I also more or less understand why this is the case. Now, this makes me wonder.. Is that the case with all NoSQL databases? Can other NoSQL systems make range queries over two different properties? How about, for example, Mongo DB? I've looked in the Documentation, but the only thing I've found was the following snippet in their docu: Note that any of the operators on this page can be combined in the same query document. For example, to find all document where j is not equal to 3 and k is greater than 10, you'd query like so: db.things.find({j: {$ne: 3}, k: {$gt: 10} }); So they use greater-than and not-equal on two different properties. They don't say anything about two inequalities ;-) Any input and enlightenment is welcome :-)

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• R selecting duplicate rows

  - by Matt

  Okay, I'm fairly new to R and I've tried to search the documentation for what I need to do but here is the problem. I have a data.frame called heeds.data in the following form (some columns omitted for simplicity) eval.num, eval.count, ... fitness, fitness.mean, green.h.0, green.v.0, offset.0, green.h.1, green.v.1,...green.h.7, green.v.7, offset.7... And I have selected a row meeting the following criteria: best.fitness <- min(heeds.data$fitness.mean[heeds.data$eval.count = 10]) best.row <- heeds.data[heeds.data$fitness.mean == best.fitness] Now, what I want are all of the other rows with that have columns green.h.0 to offset.7 (a contiguous section of columns) equal to the best.row Basically I'm looking for rows that have some of the conditions the same as the "best" row. I thought I could just do this, heeds.best <- heeds.data$fitness[ heeds.data$green.h.0 == best.row$green.h.0 & ... ] But with 24 columns it seems like a stupid method. Looking for something a bit simpler with less manual typing. Thanks!

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• What is the fastest way to find duplicates in multiple BIG txt files?

  - by user2950750

  I am really in deep water here and I need a lifeline. I have 10 txt files. Each file has up to 100.000.000 lines of data. Each line is simply a number representing something else. Numbers go up to 9 digits. I need to (somehow) scan these 10 files and find the numbers that appear in all 10 files. And here comes the tricky part. I have to do it in less than 2 seconds. I am not a developer, so I need an explanation for dummies. I have done enough research to learn that hash tables and map reduce might be something that I can make use of. But can it really be used to make it this fast, or do I need more advanced solutions? I have also been thinking about cutting up the files into smaller files. To that 1 file with 100.000.000 lines is transformed into 100 files with 1.000.000 lines. But I do not know what is best: 10 files with 100 million lines or 1000 files with 1 million lines? When I try to open the 100 million line file, it takes forever. So I think, maybe, it is just too big to be used. But I don't know if you can write code that will scan it without opening. Speed is the most important factor in this, and I need to know if it can be done as fast as I need it, or if I have to store my data in another way, for example, in a database like mysql or something. Thank you in advance to anybody that can give some good feedback.

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