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  • Suggested GA operators for a TSP problem?

    - by Mark
    I'm building a genetic algorithm to tackle the traveling salesman problem. Unfortunately, I hit peaks that can sustain for over a thousand generations before mutating out of them and getting better results. What crossover and mutation operators generally do well in this case?

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  • How to make ARGB transparency using bitwise operators.

    - by Smejda
    I need to make transparency, having 2 pixels: pixel1: {A, R, G, B} - foreground pixel pixel2: {A, R, G, B} - background pixel A,R,G,B are Byte values each color is represented by byte value now I'm calculating transparency as: newR = pixel2_R * alpha / 255 + pixel1_R * (255 - alpha) / 255 newG = pixel2_G * alpha / 255 + pixel1_G * (255 - alpha) / 255 newB = pixel2_B * alpha / 255 + pixel1_B * (255 - alpha) / 255 but it is too slow I need to do it with bitwise operators (AND,OR,XOR, NEGATION, BIT MOVE)

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  • Containers of reference_wrappers (comparison operators required?)

    - by kloffy
    If you use stl containers together with reference_wrappers of POD types, the following code works just fine: int i = 3; std::vector< boost::reference_wrapper<int> > is; is.push_back(boost::ref(i)); std::cout << (std::find(is.begin(),is.end(),i)!=is.end()) << std::endl; However, if you use non-POD types such as (contrived example): struct Integer { int value; bool operator==(const Integer& rhs) const { return value==rhs.value; } bool operator!=(const Integer& rhs) const { return !(*this == rhs); } }; It doesn't suffice to declare those comparison operators, instead you have to declare: bool operator==(const boost::reference_wrapper<Integer>& lhs, const Integer& rhs) { return boost::unwrap_ref(lhs)==rhs; } And possibly also: bool operator==(const Integer& lhs, const boost::reference_wrapper<Integer>& rhs) { return lhs==boost::unwrap_ref(rhs); } In order to get the equivalent code to work: Integer j = { 0 }; std::vector< boost::reference_wrapper<Integer> > js; js.push_back(boost::ref(j)); std::cout << (std::find(js.begin(),js.end(),j)!=js.end()) << std::endl; Now, I'm wondering if this is really the way it's meant to be done, since it seems impractical. It just seems there should be a simpler solution, e.g. templates: template<class T> bool operator==(const boost::reference_wrapper<T>& lhs, const T& rhs) { return boost::unwrap_ref(lhs)==rhs; } template<class T> bool operator==(const T& lhs, const boost::reference_wrapper<T>& rhs) { return lhs==boost::unwrap_ref(rhs); } There's probably a good reason why reference_wrapper behaves the way it does (possibly to accomodate non-POD types without comparison operators?). Maybe there already is an elegant solution and I just haven't found it.

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  • Relational Clausal Logic question: what is a Herbrand interpretation

    - by anotherstat
    I'm having a hard time coming to grips with relational clausal logic, and I'm not sure if this is the place to ask but it would be help me so much with revision if anyone could provide guidance with the following questions. Let P be the program: academic(X); student(X); other_staff(X):- works_in(X, university). :-student(john). :-other_staff(john). works_in(john, university) Question: Which are the Herbrand interpreations of P? AS

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  • PL/SQL Logical Operators evaluate whole function

    - by Chris
    I know in C like languages logical operators are evaluated one at a time so: false && really_expensive_function() is doesn't result in the function being called (I can't remember the CS name for this). Does the same happen in PL/SQL or do I need to break the IF parts out to separate blocks?

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  • php doctrine relational form naming for saving data

    - by neziric
    is it possible to have an html form organized/named in such a way that $foo-fromArray($_POST) would actually save relational data as well? example: html_form_fields: user_name country_name db_table_users: id user_name db_table_countries: id country_name update: forgot to say i'm trying to make this with zend framework forms

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  • Lightweight Relational database for BlackBerry OS 4.7

    - by Pavel
    Hey guys, I'm writing an app for BlackBerry OS 4.7 and would greatly benefit from having a lightweight relational database such as SQLite that my application can use to store data locally on the device. SQLite is coming out with 5.0, which is still in beta. Can anyone recommend any other alternatives that permit commercial use? Additional information: - Concurrent access not required - Transactions not required Thanks in advance :-)

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  • How to pass operators as parameters

    - by Rodion Ingles
    I have to load an array of doubles from a file, multiply each element by a value in a table (different values for different elements), do some work on it, invert the multiplication (that is, divide) and then save the data back to file. Currently I implement the multiplication and division process in two separate methods. Now there is some extra work behind the scenes but apart from the specific statements where the multiplication/division occurs, the rest of the code is identical. As you can imagine, with this approach you have to be very careful making any changes. The surrounding code is not trivial, so its either a case of manually editing each method or copying changes from one method to the other and remembering to change the * and / operators. After too many close calls I am fed up of this and would like to make a common function which implements the common logic and two wrapper functions which pass which operator to use as a parameter. My initial approach was to use function pointers: MultiplyData(double data) { TransformData(data, &(operator *)); } DivideData(double data) { TransformData(data, &(operator /)); } TransformData(double data, double (*func)(double op1, double op2)) { /* Do stuff here... */ } However, I can't pass the operators as pointers (is this because it is an operator on a native type?), so I tried to use function objects. Initially I thought that multiplies and divides functors in <functional> would be ideal: MultiplyData(double data) { std::multiplies<double> multFunct; TransformData(data, &multFunct); } DivideData(double data) { std::divides<double> divFunct; TransformData(data, &divFunct); } TransformData(double data, std::binary_function<double, double, double> *funct) { /* Do stuff here... */ } As you can see I was trying to use a base class pointer to pass the functor polymorphically. The problem is that std::binary_function does not declare an operator() member for the child classes to implement. Is there something I am missing, or is the solution to implement my own functor heirarchy (which really seems more trouble than it is worth)?

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  • Object Oriented vs Relational Databases

    - by Dan
    Objects oriented databases seem like a really cool idea to me, no need to worry about mapping your domain model to your database model, no messing around with sql or ORM tools. The way I understand it, relational DBs offer some advantages when there is massive amounts of data, and searching an indexing need to be done. To my mind 99% of websites are not massive, and enterprise issues never need to be thought about, so why arn't OO DBs more widely used?

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  • Windows Azure Table Storage LINQ Operators

    - by Ryan Elkins
    Currently Table Storage supports From, Where, Take, and First. Are there plans to support any of the other 29 operators? If we have to code for these ourselves, how much of a performance difference are we looking at to something similar via SQL and SQL Server? Do you see it being somewhat comparable or will it be far far slower if I need to do a Count or Sum or Group By over a gigantic dataset? I like the Azure platform and the idea of cloud based storage. I like Windows Azure for the amount of data it can store and the schema-less nature of table storage. SQL Azure just won't work due to the high cost to storage space.

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  • Creating an object relational schema from a Class diagram

    - by Caylem
    Hi Ladies and Gents. I'd like some help converting the following UML diagram: UML Diagram The diagram shows 4 classes and is related to a Loyalty card scheme for an imaginary supermarket. I'd like to create an object relational data base schema from it for use with Oracle 10g/11g. Not sure where to begin, if somebody could give me a head start that would be great. Looking for actually starting the schema, show abstraction, constraints, types(subtypes, supertypes) methods and functions. Note: I'm not looking for anyone to make any comments regarding the actual classes and whether changes should be made to the Diagram, just the schema. Thanks

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  • Import de-normalized relational data from Excel into SQL Server

    - by roryf
    I need to import data from an Excel spreadsheet into SQL Server, but the data isn't in a relational/normalized format so the import wizard isn't going to cut it (as far as I know). The data is in this format: Category SubCategory Name Description Category#1 SubCategory#1 Product#1 Description#1 Category#1 SubCategory#1 Product#2 Description#2 Category#1 SubCategory#2 Product#3 Description#3 Category#1 SubCategory#2 Product#4 Description#4 Category#2 SubCategory#3 Product#5 Description#5 (apologies I'm lacking the inventiveness to come up with 'real' data at this time in the morning...) Each row contains a unique product, but the cateogry structure is duplicated. I want to import this data into three tables: Category SubCategory Product (I know SubCategory should really be contained within Category, DB was not my design) I need a way to import unique rows based on the Category and then SubCategory columns, and then when importing the other columns into Product, obtain a reference to the SubCategory based on name. Short of scripting this, is there any way to do it using the import wizard or some other tool?

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  • MySQL Query involving column names containing math operators

    - by devil_fingers
    I'm a MySQL scrub, and I have asked around and checked around the internet for what I'm sure will turn out to be something obvious, but I'm very frustrated with what I thought would be a very, very simple query not working. So here goes. Please be gentle. Basically, in a large database, some of the column names contain mathematical operators like "/" and "+." (Don't ask, it's not my database, I can't do anything about it). Here is the "essence" of my query (I took out the irrelevant stuff for the sake of this question): SELECT PlayerId, Season, WPA/LI AS WPALI FROM tht.stats_batting_master WHERE Season = "2010" AND teamid > 0 AND PA >= 502 GROUP BY playerid ORDER BY WPALI DESC When I run this, it returns "Unknown column 'LI' in 'field list'," I assume because it sees the "/" in WPA/LI as a division sign. Like I said, I'm sure this is easy enough to work around (it must be given how much this database is used), but I haven't' been able to figure out how. Thanks in advance for any help.

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  • Database system that is not relational.

    - by paan
    What are the other types of database systems out there. I've recently came across couchDB that handles data in a non relational way. It got me thinking about what other models are other people is using. So, I want to know what other types of data model is out there. (I'm not looking for any specifics, just want to look at how other people are handling data storage, my interest are purely academic) The ones I already know are: RDBMS (mysql,postgres etc..) Document based approach (couchDB, lotus notes) Key/value pair (BerkeleyDB)

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  • Is It Worth Using Bitwise Operators In Methods?

    - by user1626141
    I am very new to Java (and programming in general, my previous experience is with ActionScript 2.0 and some simple JavaScript), and I am working my way slowly and methodically through Java: A Beginner's Guide by Herbert Schildt. It is an incredible book. For one thing, I finally understand more-or-less what bitwise operators (which I first encountered in ActionScript 2.0) do, and that they are more efficient than other methods for certain sums. My question is, is it more efficient to use a method that uses, say, a shift right, to perform all your divisions/2 (or divisions/even) for you in a large program with many calculations (in this case, a sprawling RPG), or is it more efficient to simply use standard mathematical operations because the compiler will optimise it all for you? Or, am I asking the wrong question entirely?

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  • Class basic operators

    - by swan
    Hi, Is it necessary to have a copy constructor, destructor and operator= in a class that have only static data member, no pointer class myClass{ int dm; public: myClass(){ dm = 1; } ~myClass(){ } // Is this line usefull ? myClass(const myClass& myObj){ // and that operator? this->dm = myObj.dm; } myClass& operator=(const myClass& myObj){ // and that one? if(this != &myObj){ this->dm = myObj.dm; } return *this; } }; I read that the compiler build one for us, so it is better to not have one (when we add a data member we have to update the operators)

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  • Which namespace does operator<< (stream) go to?

    - by aaa
    If I have have some overloaded ostream operators, defined for library local objects, is its okay for them to go to std namespace? If I do not declare them in std namespace, then I must use using ns:: operator <<. As a possible follow-up question, are there any operators which should go to standard or global namespace?

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  • Relational database data explorer / visualization?

    - by Ian Boyd
    Is there a tool that can let one browse relational data as a graph of connected nodes? For example, i'm faced with trying to cleanse some anomolous data. i can start with two offending rows. In this particular example, the TransactionID should, by business rules, be unique to the table, but i find a transaction that violates that rule: SELECT * FROM LCTTrans WHERE TransactionID = 1075048 LCTID TransactionID ========= ============= 4358 1075048 4359 1075048 2 row(s) affected But really what i want to begin to hunt down all the related data, to try to see which is right. So this hypothetical software would start by showing me these two rows: Next, i want to see that transaction that is linked into this table: Now that transaction points to an MAL, so show me that: Now lets add those two LCTs, that the transaction is "on". A transaction can be on only one LCT, yet this one is pointing to two: Okay computer, both of those LCTs point to an MAL and the transaction that created them, show me those: Those last two transactions, they also point at an MAL, and they themselves point to an LCT, show me those: Okay, now are there any entries in LCTTrans that point to LCTs 4358 or 4359?... And so on, and so on. Now i did all this manually, running single selects, copying and pasting uniqueidentifier keys and converting them into friendly id numbers so i could easily see the relationships. Is there software that can do this?

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  • C++ overloading comparative operators for a MyString class

    - by Taylor Gang
    bool operator == (const MyString& left, const MyString& right) { if(left.value == right.value) return true; else return false; } bool operator != (const MyString& left, const MyString& right) { if(left == right) return false; else return true; } bool operator < (const MyString& left, const MyString& right) { if(strcmp(left.value, right.value) == -1) return true; else return false; } bool operator > (const MyString& left, const MyString& right) { if(strcmp(left.value, right.value) == 1) return true; else return false; } bool operator <= (const MyString& left, const MyString& right) { if(strcmp(left.value, right.value) == -1 || strcmp(left.value, right.value) == 0) return true; else return false; } bool operator >= (const MyString& left, const MyString& right) { if(strcmp(left.value, right.value) == 1 || strcmp(left.value, right.value) == 0) return true; else return false; } So these are my implemented comparison operators for my MyString class, they fail the test program that my professor gave me and could use some direction. Thanks in advance for any and all help I receive.

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  • Database model for keeping track of likes/shares/comments on blog posts over time

    - by gage
    My goal is to keep track of the popular posts on different blog sites based on social network activity at any given time. The goal is not to simply get the most popular now, but instead find posts that are popular compared to other posts on the same blog. For example, I follow a tech blog, a sports blog, and a gossip blog. The tech blog gets waaay more readership than the other two blogs, so in raw numbers every post on the tech blog will always out number views on the other two. So lets say the average tech blog post gets 500 facebook likes and the other two get an average of 50 likes per post. Then when there is a sports blog post that has 200 fb likes and a gossip blog post with 300 while the tech blog posts today have 500 likes I want to highlight the sports and gossip blog posts (more likes than average vs tech blog with more # of likes but just average for the blog) The approach I am thinking of taking is to make an entry in a database for each blog post. Every x minutes (say every 15 minutes) I will check how many likes/shares/comments an entry has received on all the social networks (facebook, twitter, google+, linkeIn). So over time there will be a history of likes for each blog post, i.e post 1234 after 15 min: 10 fb likes, 4 tweets, 6 g+ after 30 min: 15 fb likes, 15 tweets, 10 g+ ... ... after 48 hours: 200 fb likes, 25 tweets, 15 g+ By keeping a history like this for each blog post I can know the average number of likes/shares/tweets at any give time interval. So for example the average number of fb likes for all blog posts 48hrs after posting is 50, and a particular post has 200 I can mark that as a popular post and feature/highlight it. A consideration in the design is to be able to easily query the values (likes/shares) for a specific time-frame, i.e. fb likes after 30min or tweets after 24 hrs in-order to compute averages with which to compare against (or should averages be stored in it's own table?) If this approach is flawed or could use improvement please let me know, but it is not my main question. My main question is what should a database scheme for storing this info look like? Assuming that the above approach is taken I am trying to figure out what a database schema for storing the likes over time would look like. I am brand new to databases, in doing some basic reading I see that it is advisable to make a 3NF database. I have come up with the following possible schema. Schema 1 DB Popular Posts Table: Post post_id ( primary key(pk) ) url title Table: Social Activity activity_id (pk) url (fk) type (i.e. facebook,twitter,g+) value timestamp This was my initial instinct (base on my very limited db knowledge). As far as I under stand this schema would be 3NF? I searched for designs of similar database model, and found this question on stackoverflow, http://stackoverflow.com/questions/11216080/data-structure-for-storing-height-and-weight-etc-over-time-for-multiple-users . The scenario in that question is similar (recording weight/height of users overtime). Taking the accepted answer for that question and applying it to my model results in something like: Schema 2 (same as above, but break down the social activity into 2 tables) DB Popular Posts Table: Post post_id (pk) url title Table: Social Measurement measurement_id (pk) post_id (fk) timestamp Table: Social stat stat_id (pk) measurement_id (fk) type (i.e. facebook,twitter,g+) value The advantage I see in schema 2 is that I will likely want to access all the values for a given time, i.e. when making a measurement at 30min after a post is published I will simultaneous check number of fb likes, fb shares, fb comments, tweets, g+, linkedIn. So with this schema it may be easier get get all stats for a measurement_id corresponding to a certain time, i.e. all social stats for post 1234 at time x. Another thought I had is since it doesn't make sense to compare number of fb likes with number of tweets or g+ shares, maybe it makes sense to separate each social measurement into it's own table? Schema 3 DB Popular Posts Table: Post post_id (pk) url title Table: fb_likes fb_like_id (pk) post_id (fk) timestamp value Table: fb_shares fb_shares_id (pk) post_id (fk) timestamp value Table: tweets tweets__id (pk) post_id (fk) timestamp value Table: google_plus google_plus_id (pk) post_id (fk) timestamp value As you can see I am generally lost/unsure of what approach to take. I'm sure this typical type of database problem (storing measurements overtime, i.e temperature statistic) that must have a common solution. Is there a design pattern/model for this, does it have a name? I tried searching for "database periodic data collection" or "database measurements over time" but didn't find anything specific. What would be an appropriate model to solve the needs of this problem?

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  • How to design database for tests in online test application

    - by Kien Thanh
    I'm building an online test application, the purpose of app is, it can allow teacher create courses, topics of course, and questions (every question has mark), and they can create tests for students and students can do tests online. To create tests of any courses for students, first teacher need to create a test pattern for that course, test pattern actually is a general test includes the number of questions teacher want it has, then from that test pattern, teacher will generate number of tests corresponding with number of students will take tests of that course, and every test for student will has different number of questions, although the max mark of test in every test are the same. Example if teacher generate tests for two students, the max mark of test will be 20, like this: Student A take test with 20 questions, student B take test only has 10 questions, it means maybe every question in test of student A only has mark is 1, but questions in student B has mark is 2. So 20 = 10 x 2, sorry for my bad English but I don't know how to explain it better. I have designed tables for: - User (include students and teachers account) - Course - Topic - Question - Answer But I don't know how to define associations between user and test pattern, test, question. Currently I only can think these: Test pattern table: name, description, dateStart, dateFinish, numberOfMinutes, maxMarkOfTest Test table: test_pattern_id And when user (is Student) take tests, I think i will have one more table: Result: user_id, test_id, mark but I can't set up associations among test pattern and test and question. How to define associations?

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