Search Results

Search found 4532 results on 182 pages for 'category theory'.

Page 21/182 | < Previous Page | 17 18 19 20 21 22 23 24 25 26 27 28  | Next Page >

• Fitts Law, applying it to touch screens

  - by Caylem

  Been reading a lot into UI design lately and Fitts Law keeps popping up. Now from what i gather its basically the larger an item is, and the closer it is to your cursor, the easier it is to click on. So what about touch screen devices where the input comes from multiple touches or just single touches. What are the fundamentals to take into account considering this? Should it be something like, the hands of the user are on the sides of the device so the buttons should be close to the left and right hand sides of the device? Thanks

  Read the article

• Can an algorithmic process ever give true random numbers ?

  - by Arkapravo

  I have worked with random functions in python,ruby, MATLAB, Bash and Java. Nearly every programming language has a function to generate Random numbers. However, these apparently random sequences are termed as pseudo-random number sequences as the generation follows a deterministic approach, and the sequence seems to repeat (usually with a very large period). My question, can an algorithmic/programming process ever yield true random numbers ? The questions probably is more of theoretical computer science than just programming !

  Read the article

• What efforts exist to use programming languages to model legal code?

  - by agnoster

  Legalese can be considered an extremely inefficient language, and it certainly has ambiguities. What attempts exist out there to use programming languages (or any symbolic logic approaches, for that matter) to model legal code (such as laws and contracts)?

  Read the article

• Finding contained bordered regions from Excel imports.

  - by dmaruca

  I am importing massive amounts of data from Excel that have various table layouts. I have good enough table detection routines and merge cell handling, but I am running into a problem when it comes to dealing with borders. Namely performance. The bordered regions in some of these files have meaning. Data Setup: I am importing directly from Office Open XML using VB6 and MSXML. The data is parsed from the XML into a dictionary of cell data. This wonks wonderfully and is just as fast as using docmd.transferspreadsheet in Access, but returns much better results. Each cell contains a pointer to a style element which contains a pointer to a border element that defines the visibility and weight of each border (this is how the data is structured inside OpenXML, also). Challenge: What I'm trying to do is find every region that is enclosed inside borders, and create a list of cells that are inside that region. What I have done: I initially created a BFS(breadth first search) fill routine to find these areas. This works wonderfully and fast for "normal" sized spreadsheets, but gets way too slow for imports into the thousands of rows. One problem is that a border in Excel could be stored in the cell you are checking or the opposing border in the adjacent cell. That's ok, I can consolidate that data on import to reduce the number of checks needed. One thing I thought about doing is to create a separate graph that outlines the cells using the borders as my edges and using a graph algorithm to find regions that way, but I'm having trouble figuring out how to implement the algorithm. I've used Dijkstra in the past and thought I could do similar with this. So I can span out using no endpoint to search the entire graph, and if I encounter a closed node I know that I just found an enclosed region, but how can I know if the route I've found is the optimal one? I guess I could flag that to run a separate check for the found closed node to the previous node ignoring that one edge. This could work, but wouldn't be much better performance wise on dense graphs. Can anyone else suggest a better method? Thanks for taking the time to read this.

  Read the article

• Mutual Information / Entropy Calculation Help

  - by Fillip

  Hi, Hoping someone can give me some pointers with this entropy problem. Say X is chosen randomly from the uniform integer distribution 0-32 (inclusive). I calculate the entropy, H(X) = 32 bits, as each Xi has equal probability of occurring. Now, say the following pseudocode executes. int r = rand(0,1); // a random integer 0 or 1 r = r * 33 + X; How would I work out the mutual information between the two variables r and X? Mutual Information is defined as I(X; Y) = H(X) - H(X|Y) but I don't really understand how to apply the conditional entropy H(X|Y) to this problem. Thanks

  Read the article

• Object responsibilities - list and item

  - by Mark Tyler

  My question is more like a theoretical. Say you have an object, that represents the list of something (articles, pages, accounts etc.) class ObjCollection You have a class, that represents a specific item in collection: class objItem I have a problem thinking of a basic responsibilities of each object. Which class is responsible for creating a new objItem? Which class is responsible for deleting a objItem? Should it delete itself as a method?

  Read the article

• Algorithm for Determining Variations of Differing Lengths

  - by joseph.ferris

  I have four objects - for the sake of arguments, let say that they are the following letters: A B C D I need to calculate the number of variations that can be made for these under the following two conditions: No repetition Objects are position agnostic Taking the above, this means that with a four object sequence, I can have only one sequence that matches the criteria (since order is not considered for being unique): ABCD There are four variations for a three object combination from the four object pool: ABC, ABD, ACD, and BCD There are six variations for a two object combination from the four object pool: AB, AC, AD, BC, BD, and CD And the most simple one, if taken on at a time: A, B, C, and D I swear that this was something covered in school, many, many years ago - and probably forgotten since I didn't think I would use it. :-) I am anticipating that factorials will come into play, but just trying to force an equation is not working. Any advice would be appreciated.

  Read the article

• What is the difference between causal models and directed graphical models?

  - by Neil G

  What is the difference between causal models and directed graphical models? or: What is the difference between causal relationships and directed probabilistic relationships? or, even better: What would you put in the interface of a DirectedProbabilisticModel class, and what in a CausalModel class? Would one inherit from the other? Collaborative solution: interface DirectedModel { map<Node, double> InferredProbabilities(map<Node, double> observed_probabilities, set<Node> nodes_of_interest) } interface CausalModel: DirectedModel { bool NodesDependent(set<Node> nodes, map<Node, double> context) map<Node, double> InferredProbabilities(map<Node, double> observed_probabilities, map<Node, double> externally_forced_probabilities, set<Node> nodes_of_interest) }

  Read the article

• P=NP?-Problem: What are the most promising methods?

  - by phimuemue

  Hello everybody, I know that P=NP has not been solved up to now, but can anybody tell me something about the following: What are currently the most promising mathematical / computer scientific methods that could be helpful to tackle this problem? Or are there even none such methods known to be potentially helpful up to now? Is there any (free) compendium on this topic where I can find all / most of the research done in this area?

  Read the article

• the problem only happens when i try create a release...

  - by ace

  I'm sorry if im not presenting this right, but i trully cannot understand what the problem is. i have a project to hand in, a code of 600 lines defined within a main, .cpp, and header file. if i compile the project with just a debugger and no release, it's fine. when i create it with the release, the following error occurs, for every function!!! 1st error: |36|multiple definition of `countLines(int&, std::vector const&)'| 2nd error: |36|first defined here| if someone will allow me and i can send them the entire code, that would be awesome - i have to have this done within 3 hours.

  Read the article

• Adjusting for compass wrap around in a navigation application

  - by chris12892

  I have a application where I am guiding a vehicle on compass headings and I am having an issue when the vehicle is crossing from 360 degrees to 0 degrees. In this case, there are no smarts in the control loop to compute that the nearest way to turn to follow a heading. For example, if the vehicle is instructed to follow a heading of 360 degrees, it will inevitably drifts a few degrees to ether side. If it drifts over to 0+ degrees, the control loop will go nuts and try to steer the vehicle all the way around to get it to 360 degrees again. Is there a graceful way to deal with this? The way the navigate function is written, I use an external PID controller class and I calculate the heading like this: lock (steering) { if (!Engaged) { return; } double mv = 90 + Trim + pidController.CalculateCorrection(flyHeading, currentHeading); steering.Degree = mv; } Thanks!

  Read the article

• Database Design for One to One relationships

  - by Greelmo

  I'm trying to finalize my design of the data model for my project, and am having difficulty figuring out which way to go with it. I have a table of users, and an undetermined number of attributes that apply to that user. The attributes are in almost every case optional, so null values are allowed. Each of these attributes are one to one for the user. Should I put them on the same table, and keep adding columns when attributes are added (making the user table quite wide), or should I put each attribute on a separate table with a foreign key to the user table. I have decided against using the EAV model. Thanks!

  Read the article

• 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?

  Read the article

• Resource placement (optimal strategy)

  - by blackened

  I know that this is not exactly the right place to ask this question, but maybe a wise guy comes across and has the solution. I'm trying to write a computer game and I need an algorithm to solve this question: The game is played between 2 players. Each side has 1.000 dollars. There are three "boxes" and each player writes down the amount of money he is going to place into those boxes. Then these amounts are compared. Whoever placed more money in a box scores 1 point (if draw half point each). Whoever scores more points wins his opponents 1.000 dollars. Example game: Player A: [500, 500, 0] Player B: [333, 333, 334] Player A wins because he won Box A and Box B (but lost Box C). Question: What is the optimal strategy to place the money? I have more questions to ask (algorithm related, not math related) but I need to know the answer to this one first. Update (1): After some more research I've learned that these type of problems/games are called Colonel Blotto Games. I did my best and found few (highly technical) documents on the subject. Cutting it short, the problem I have (as described above) is called simple Blotto Game (only three battlefields with symmetric resources). The difficult ones are the ones with, say, 10+ battle fields with non-symmetric resources. All the documents I've read say that the simple Blotto game is easy to solve. The thing is, none of them actually say what that "easy" solution is.

  Read the article

• django many to many validation when add()

  - by Julien

  Hi i have a Category model with parent/child self relation For primary category and sub categories : class Place(models.Model): name = models.CharField(_("name"), max_length=100) categories = models.ManyToManyField("Category", verbose_name=_("categories")) class Category(models.Model): name = models.CharField(_("name"), max_length=100) parent = models.ForeignKey('self', blank=True, null=True, related_name='child_set') i need to prevent orphans, to prevent this kind of errors (in admin web interface) c_parent = Category(name='Restaurant') c_parent.save() c_child = Category(name="Japanese restaurant", parent=c_parent) c_child.save() place1 = Place (name="Planet sushi") place1.save() place1.categories.add(c_parent) place1.categories.add(c_child) So now we have a new Place called "Planet sushi", it's a Restaurant (root category), and a Japanese Restaurant (sub category) but i want to prevent this kind of things : place2 = Place (name="Tokyofood") place2.save() place2.categories.add(c_child) because parent is not set, or is not the correct parent category where can i do form validation for the admin ? and other forms (because any user can add a new place and will have to choose correct categories for)

  Read the article

• Fastest way to perform subset test operation on a large collection of sets with same domain

  - by niktech

  Assume we have trillions of sets stored somewhere. The domain for each of these sets is the same. It is also finite and discrete. So each set may be stored as a bit field (eg: 0000100111...) of a relatively short length (eg: 1024). That is, bit X in the bitfield indicates whether item X (of 1024 possible items) is included in the given set or not. Now, I want to devise a storage structure and an algorithm to efficiently answer the query: what sets in the data store have set Y as a subset. Set Y itself is not present in the data store and is specified at run time. Now the simplest way to solve this would be to AND the bitfield for set Y with bit fields of every set in the data store one by one, picking the ones whose AND result matches Y's bitfield. How can I speed this up? Is there a tree structure (index) or some smart algorithm that would allow me to perform this query without having to AND every stored set's bitfield? Are there databases that already support such operations on large collections of sets?

  Read the article

• How to find whole graph coverage path in dynamic state-flow diagram?

  - by joseph

  Hello, As I've been researching algorithms for path finding in graph, I found interesting problem. Definition of situation: 1)State diagram can have p states, and s Boolean Fields, and z Int Fields 2)Every state can have q ingoing and r outgoing transitions, and h Int fields (h belongs to z - see above) 3)Every transition can have only 1 event, and only 1 action 4)every action can change n Boolean Fields, and x Int Fields 5)every event can have one trigger from combination of any count of Boolean Fields in diagram 6)Transition can be in OPEN/CLOSED form. If the transition is open/closed depends on trigger2 compounded from 0..c Boolean fields. 7) I KNOW algorithm for finding shortest paths from state A to state B. 8) I KNOW algorithm for finding path that covers all states and transitions of whole state diagram, if all transitions are OPEN. Now, what is the goal: I need to find shortest path that covers all states and transitions in dynamically changing state diagram described above. When an action changes some int field, the algorithm should go through all states that have changed int field. The algorithm should also be able to open and close transition (by going through transitions that open and close another transitions by action) in the way that the founded path will be shortest and covers all transitions and states. Any idea how to solve it? I will be really pleased for ANY idea. Thanks for answers.

  Read the article

• Make Java parent class not part of the interface

  - by Bart van Heukelom

  (This is a hypothetical question for discussion, I have no actual problem). Say that I'm making an implementation of SortedSet by extending LinkedHashMap: class LinkedHashSortedMapThing extends LinkedHashMap implements SortedSet { ... } Now programmers who use this class may do LinkedHashMap x = new LinkedHashSortedMapThing(); But what if I consider the extending of LinkedHashMap an implementation detail, and do not want it to be a part of the class' contract? If people use the line above, I can no longer freely change this detail without worrying about breaking existing code. Is there any way to prevent this sort of thing, other than favouring composition over inheritance (which is not always possible due to private/protected members)?

  Read the article

• clique number of a graph

  - by copperhead

  I would like to know a fast algorithm to find only the clique number(without actually finding the clique) of a graph with about 100 vertices.

  Read the article

• SRAM Cell Diagram - Can someone explain this a bit more clearly? ( From COMP1917 @ UNSW: Lecture 2 o

  - by Kristina

  I've begun watching a series of first year lectures from the University of New South Wales (UNSW) in Australia, and I'm a bit perplexed by the instructors explanation of how an SRAM gate works. I realize this isn't exactly "programming-related" but since it comes from a series of lectures relating to computing and programming, I thought StackOverflow may be able to help (reddit failed me entirely). In this lecture beginning at around 32:12, Richard (the lecturer) tries to explain how a "latch gate" works within SRAM. Although his students seem to keep up, I feel I'm missing something crucial which is preventing the concept from really "clicking" in my brain. For convenience, I've added the image from the video below: Thanks in advance for any help you can provide, but if this question doesn't fit your view of "programming-related" could you please provide an alternate forum for this in a comment when you cast your close vote? Thanks!

  Read the article

• Enumerating all hamiltonian paths from start to end vertex in grid graph

  - by Eric

  Hello, I'm trying to count the number of Hamiltonian paths from a specified start vertex that end at another specified vertex in a grid graph. Right now I have a solution that uses backtracking recursion but is incredibly slow in practice (e.g. O(n!) / 3 hours for 7x7). I've tried a couple of speedup techniques such as maintaining a list of reachable nodes, making sure the end node is still reachable, and checking for isolated nodes, but all of these slowed my solution down. I know that the problem is NP-complete, but it seems like some reasonable speedups should be achievable in the grid structure. Since I'm trying to count all the paths, I'm sure that the search must be exhaustive, but I'm having trouble figuring out how to prune out paths that aren't promising. Does anyone have some suggestions for speeding the search up? Or an alternate search algorithm?

  Read the article

• Big-O for Eight Year Olds?

  - by Jason Baker

  I'm asking more about what this means to my code. I understand the concepts mathematically, I just have a hard time wrapping my head around what they mean conceptually. For example, if one were to perform an O(1) operation on a data structure, I understand that the amount of operations it has to perform won't grow because there are more items. And an O(n) operation would mean that you would perform a set of operations on each element. Could somebody fill in the blanks here? Like what exactly would an O(n^2) operation do? And what the heck does it mean if an operation is O(n log(n))? And does somebody have to smoke crack to write an O(x!)?

  Read the article

• Is it possible to "learn" a regular expression by user-provided examples?

  - by DR

  Is it possible to "learn" a regular expression by user-provided examples? To clarify: I do not want to learn regular expressions. I want to create a program which "learns" a regular expression from examples which are interactively provided by a user, perhaps by selecting parts from a text or selecting begin or end markers. Is it possible? Are there algorithms, keywords, etc. which I can Google for? EDIT: Thank you for the answers, but I'm not interested in tools which provide this feature. I'm looking for theoretical information, like papers, tutorials, source code, names of algorithms, so I can create something for myself.

  Read the article

• The limits of parallelism

  - by psihodelia

  Is it possible to solve a problem of O(n!) complexity within a reasonable time given infinite number of processing units and infinite space? The typical example of O(n!) problem is brute-force search: trying all permutations (ordered combinations).

  Read the article

• circles and triangles problem

  - by Faken

  Hello everyone, I have an interesting problem here I've been trying to solve for the last little while: I have 3 circles on a 2D xy plane, each with the same known radius. I know the coordinates of each of the three centers (they are arbitrary and can be anywhere). What is the largest triangle that can be drawn such that each vertice of the triangle sits on a separate circle, what are the coordinates of those verticies? I've been looking at this problem for hours and asked a bunch of people but so far only one person has been able to suggest a plausible solution (though i have no way of proving it). The solution that we have come up with involves first creating a triangle about the three circle centers. Next we look at each circle individually and calculate the equation of a line that passes through the circle's center and is perpendicular to the opposite edge. We then calculate two intersection points of the circle. This is then done for the next two circles with a result of 6 points. We iterate over the 8 possible 3 point triangles that these 6 points create (the restriction is that each point of the big triangle must be on a separate circle) and find the maximum size. The results look reasonable (at least when drawn out on paper) and it passes the special case of when the centers of the circles all fall on a straight line (gives a known largest triangle). Unfortunate i have no way of proving this is correct or not. I'm wondering if anyone has encountered a problem similar to this and if so, how did you solve it? Note: I understand that this is mostly a math question and not programming, however it is going to be implemented in code and it must be optimized to run very fast and efficient. In fact, I already have the above solution in code and tested to be working, if you would like to take a look, please let me know, i chose not to post it because its all in vector form and pretty much impossible to figure out exactly what is going on (because it's been condensed to be more efficient). Lastly, yes this is for school work, though it is NOT a homework question/assignment/project. It's part of my graduate thesis (abet a very very small part, but still technically is part of it). Thanks for your help.

  Read the article

< Previous Page | 17 18 19 20 21 22 23 24 25 26 27 28  | Next Page >